WHP Cruise Summary Information

WOCE section designation
A25

Expedition designation (EXPOCODE)
74DI230_1

Chief Scientist(s) and their affiliation
Sheldon Bacon, SOC/JRD

Dates
1997.08.07 - 1997.09.17

Ship
DISCOVERY

Ports of call
Vigo, Spain to Southampton, U.K.

Number of stations
143

Geographic boundaries of the stations
	6531.92''N
4319.15''W	819.98''W
	4128.00'N

Floats and drifters deployed
see below

Moorings deployed or recovered
see below

Contributing Authors
(in order of appearance)

M.A. Harding
J. Smithers
S. Cunningham 
M. Tsimplis
P. Holliday
H. Bryden
B. Marsh 
M. Yelland 
E. Rourke
S.K. Brown
J. Xiong
S. Holley 
M. Rodriguez
I. Aristegui 
D. Smythe-Wright
S. Boswell
C. Harris 
R. Davidson
C. Peckett
M. Fox
V. Thierry
P. Mason
R. Phipps
S. Mitchell

SOUTHAMPTON OCEANOGRAPHY CENTRE

Cruise Report No. 16

RRS DISCOVERY Cruise 230

7 August - 17 September 1997

Two hydrographic sections across the boundaries of the subpolar gyre

FOUREX

Principal Scientist
Sheldon Bacon

1998

James Rennell Division for Ocean Circulation
Southampton Oceanography Centre
Empress Dock
Southampton SO14 3ZH, U. K.
Tel:	+44 1703 596441
Fax:	+44 1703 596204
Email:	S.Bacon@soc.soton.ac.uk

DOCUMENT DATA SHEET:

Author:
Sheldon Bacon

Title:
RRS Discovery Cruise 230, 7 August - 17 September 1997. Two hydrographic 
sections across the boundaries of the subpolar gyre, FOUREX.

Reference:
Southampton Oceanography Centre Cruise Report, No. 16, 104 pp.

Abstract:
This report describes RRS Discovery Cruise 230, designed as a repeat of the 
International Geophysical Year (IGY) survey section 4, roughly from Cape 
Finisterre (Spain) to Cape Farewell (Greenland). IGY 4 was first surveyed in 
1957, so this repeat gives a 40-year look at decadal variability in the North 
Atlantic from the eastern boundary regime via the junction of subtropical and 
subpolar gyres to the western boundary regime. Additional short sections were 
measured (a) midway between Cape Farewell and Denmark Strait, (b) across 
Denmark Strait and (c) from Iceland to Scotland in order (i) to assess the 
spatial variability of the western boundary regime up the east Greenland coast 
to Denmark Strait, (ii) to assess the exchange between the northern North 
Atlantic and the Nordic Seas, (iii) to create a large scale North Atlantic 
closed box for evaluation of the circulation, and (iv) to continue the long 
time series of Rockall Trough sections. Sections were measured with stations 
for CTD, LADCP and tracer chemistry (CFCs, oxygen, nutrients, CO2). Continuous 
measurements of high precision position and heading navigation data were made; 
also of VM-ADCP, depth and TSG. Continuous high-quality meteorological 
measurements were made, with a view to assessing Ekman fluxes, and comparing 
with fluxes inferred from Irminger Basin float data. This cruise is a U. K. 
contribution to the World Ocean Circulation Experiment.

Keywords:
ADCP; ATLN; CARBON DIOXIDE; CFC; CHARLIE-GIBBS FRACTURE ZONE; CO2; CRUISE 230 
1997; CTD OBSERVATIONS; DENMARK STRAIT; DISCOVERY; IBERIAN ABYSSAL PLAIN; 
ICELAND BASIN; INTERNATIONAL GEOPHYSICAL YEAR; IGY; IRMINGER BASIN; LADCP; 
NORTH ATLANTIC; NUTRIENTS; OXYGEN; ROCKALL TROUGH; WATER EXCHANGE; WOCE.

CONTENTS:

SCIENTIFIC PERSONNEL

SHIP'S PERSONNEL

LIST OF FIGURES

LIST OF TABLES

ACKNOWLEDGEMENTS

1.	THE CRUISE
	a. Scientific objectives
	b. Overview
	c. Narrative

2.	CTD MEASUREMENTS
	a. Equipment
	b. Data capture and processing
	c. Post-cruise calibration

3.	LOWERED ADCP MEASUREMENTS
	a. Description
	b. Instrument problems
	c. Data processing
	d. Bottom tracking data
	e. Comparison of VM - and L-ADCP

4.	NAVIGATION
	a. Bestnav
	b. GPS and GLONASS
	c. Ship gyrocompass
	d. Ashtech 3D attitude determination

5.	VM-ADCP MEASUREMENTS
	a. Description and processing
	b. Calibration
	c. Performance
	d. General description of observed currents

6.	METEOROLOGICAL MEASUREMENTS
	a. Surface meteorology
	b. Shipborne wave recorder
	c. Rain buoy

7.	CHEMICAL MEASUREMENTS
	a. Oxygen
	b. Nutrients
	c. Carbon
	d. Halocarbons
	e. Phytoplankton Speciation and Pigment Studies
	f. Salinity

8.	OTHER MEASUREMENTS
	a. Thermosalinograph
	b. Precision Echo Sounder

9.	COMPUTING

10.	TECHNICAL SUPPORT

11.	APPENDIX: FOUREX STATION INFORMATION

SCIENTIFIC PERSONNEL

Name:			From:		Role:
BACON, Sheldon		SOC-JRD		Principal Scientist
ARISTEGUI, Iris Soler	IIM		CO2 analyst
BOSWELL, Steve		SOC-GDD		CFC analyst
BRIDGER, Martin		SOC-RVS		Computing tech.
BROWN, Sarah		Portsmouth Univ.Chemistry assistant
BRYDEN, Harry		SOC-JRD		Physics assistant
CUNNINGHAM, Stuart	SOC-JRD		CTD & data (PI)
DAVIDSON, Russell	SOC-GDD		Shrubbery (PI), CFC assistant
DUNCAN, Paul		SOC-RVS		Computing tech. (senior)
FOX, Maryke		SOC-JRD		Physics assistant & LADCP
HARRIS, Craig		Liverpool Univ.	CFC assistant
HOLLEY, Sue		SOC-GDD		Oxygen & nutrients (PI)
HOLLIDAY, Penny		SOC-GDD		LADCP (PI)
JOLLY, Dave		SOC-RVS		Mechanic
MARSH, Bob		SOC-JRD		Navigation & VM-ADCP (PI)
MASON, Peter		SOC-RVS		Mechanic (senior RVS tech.)
MITCHELL, Simon		SOC-RVS		Mechanic
PECKETT, Cristina	SOC-GDD		CFC & shrubbery assistant
PHIPPS, Richie		SOC-RVS		Mechanic
RODRIGUEZ, Marta	IIM		CO2 (PI)
ROURKE, Lizzie		SOC-JRD		Oxygen & nutrients assistant
SMITHERS, John		SOC-OTD		CTD/Electronic tech.
SMYTHE-WRIGHT, Denise	SOC-JRD		CFC (PI)
THIERRY, Virgine	IFREMER		Physics assistant
TSIMPLIS, Mickey	SOC-JRD		Computing & LADCP
XIONG, Jian		Southampton Univ.Oxygen & nutrients assistant
YELLAND, Margaret	SOC-JRD		Meteorology (PI)

KEY

SOC:	Southampton Oceanography Centre
GDD:	George Deacon Division
JRD:	James Rennell Division
OTD:	Ocean Technology Division
RVS:	Research Vessel Services
IIM:	Instituto de Investigaciones Marias, Vigo
IFREMER:Institut Franais de recherche pour l'exploitation de la mer, Brest

SHIP'S PERSONNEL

Name:		Rank/Rating:
HARDING, Mike	Master
LEATHER, Ceri	Mate
SYKES, Syd	Second Mate
REYNOLDS, Pete	Third Mate
SUGDEN, Dave	Radio Officer
McDONALD, BernieChief Engineer
CLARKE, John	Second Engineer
BELL, Steve	Third Engineer
JACKSON, Greg	Third Engineer
POOK, Tiny	C.P.O. (D)
LUCKHURTS, KevinP.O. (D)
COOK, Stuart	SG1A
CRABB, Gary	SG1A
DICKINSON, Bob	SG1A
EDWARDS, Tim	SG1A
MACLEAN, Andy	SG1A
MICKMAN, Bill	MM1A
PERRY, Clive	S.C.M.
HAUGHTON, John	Chef
DUNCAN, Andy	Mess Steward
CARTER, Shiela	Steward
ORSBORN, Jeff	Steward

LIST OF FIGURES

1.1	Cruise track
1.2	Station positions
3.1	VM- and L-ADCP profile comparison
3.2	LADCP water track / bottom track comparison
6.1	Comparison of Hs corrected and uncorrected
7.1	Variations in thiosulphate normality
7.2a	Duplicate difference at each station
7.2b	Comparison of duplicate difference with bottles used
7.3a	Silicate QC deep, QC3 and QC4
7.3b	Nitrate QC deep, QC3 and QC4
7.3c	Phosphate QC deep, QC3 and QC4
7.4	Salinity standard history
A1	Bottle depths vs. station number

LIST OF TABLES

2.1	Laboratory measurements of pressure hysteresis for DEEP01
2.2	Corrections to the conductivity offset
2.3	Laboratory measurements of pressure hysteresis for DEEP02
2.4	Salinity correction coefficients
2.5	Salinity residual statistics
2.6	Oxygen coefficients and sum square residuals
2.7	Statistics of comparison of upcast CTD minus reversing instrument value
2.8	Post-cruise laboratory measurements of pressure hysteresis for DEEP02
2.9	Post-cruise reversing instrument and DEEP02 comparisons
3.1	Upper ocean differences between VM- and L-ADCP currents
3.2	Comparison of absolute LADCP and Bottom Track velocities
4.1	Ship navigation error determined in port
4.2	Summary of Ashtech 3DF GPS performance statistics
5.1	VM-ADCP calibration exercise results
6.1	Variables and sensors logged by GrhoMet system
7.1	Summary of chemical sampling regime during cruise
7.2	Working nutrient standard concentration
7.3	Correction factors applied to the nutrient data
7.4	Standard seawater salinities
8.1	Comparison of acual depth with echo-sounder depth on station
A1	WOCE format station summary

ACKNOWLEDGEMENTS

Without meaning to anticipate the encomia which will doubtless be forthcoming, 
I must thank first the Master, Captain Mike Harding. This may well have been 
his last research cruise as Master, in view of his impending retirement, and I 
wish to thank him for helping to make my first cruise as PSO such a pleasure. 
There was a '70's theme party during the cruise, and all were amused by Mike's 
wilful misinterpretation of the invitation as over-70's rather than 1970's. He 
appeared with walking stick and pension book, and wearing a slightly 
disreputable tweed jacket, in anticipation of times to come, one supposes. 
Mike will be sorely missed by all, and I take this opportunity to wish him 
well for the future.

John Smithers is less an electronics technician and more a wizard. I express 
my sincere thanks to him, particularly in respect of the Lowered Doppler 
Affair. It is hard to imagine that this cruise would have been anything like 
the success it was without the benefit of his remarkable expertise.

I am most grateful to Sue Scrowston, Andy Louch and Jackie Skelton of the RVS 
Operations Office for their sorting out much of the mundane logistics - 
hotels, flights, freight etc. I am particularly grateful to Sue and Andy for 
their near-instant response in the Lowered Doppler Affair, which ensured that 
minimal time was lost in fetching replacement gear. Thanks also to Rob Bonner 
(SOC-OTD) for logistical help.

In the same (aforementioned) context, thanks to Nick Crisp (SOC-OTD) for 
arranging the replacement LADCP parts.

Thanks to Chris German (SOC-CHD) for the loan of the TOBI swivel.

Thanks to Robin Pascal (SOC-OTD) for flying out to Vigo to help set up the 
Met. gear, and likewise thanks to Gwyneth Jones (SOC Computing) for helping to 
set up the computers.

Thanks to Aida Rios (IIM, Vigo), for her considerable help in arranging the 
participation of IIM scientists (Marta and Iris) to look after the CO2 
measurements on this cruise.

Finally, and most importantly, my sincere thanks to the responsible 
authorities of Greenland, Iceland, Spain and Portugal, for their gracious 
granting of permission to work in their respective territorial waters, without 
which much of this cruise would have been meaningless.

The cruise was funded by the U. K. Natural Environment Research Council as 
part of the U. K. contribution to WOCE.

Sheldon Bacon

1.	THE CRUISE
a.	SCIENTIFIC OBJECTIVES

During 1996-1997 the intense measuring effort put into the North Atlantic 
under the aegis of international WOCE has several aims in accordance with Goal 
1 of WOCE (WOCE Implementation Plan, 1988). Firstly, meridional transports of 
heat, mass and freshwater will be measured, from exchanges with the South 
Atlantic across the Equator to exchanges with the Northern Seas between 
Greenland and Scotland via the Sub-Tropical and Sub-Polar Gyres. Secondly, 
decadal variability will be examined through exact track repeats of cruises 
from the International Geophysical Year (IGY) expeditions in 1957-1958, and 
others. IGY is the first large-scale field program which can be used as a 
basis for modern comparative work because its measurements are the first which 
approach modern standards of accuracy. Thirdly, there will be a focus on the 
Sub-Polar Gyre, intending to quantify the rates and to study the physics of 
the formation of mode waters and deep waters. The main or most immediate aims 
of this cruise, designated WOCE cruise A24, go under four headings:

(1)	Repeat survey of IGY Section 4 (Portugal to Greenland), for climate 
	change analysis;
(2)	Determination of heat, mass and freshwater fluxes across IGY Section 4, 
	and across northern 'closure' sections; thus, exchanges between the 
	Sub-Polar Gyre and (to the north) the Nordic Seas, and (to the south) the 
	Sub-Tropical Gyre.
(3)	Continuation of the Ellett (Dunstaffnage Marine Laboratory) time series 
	section across Anton Dohrn Seamount;
(4)	Production of data suitable for inclusion in the WOCE North Atlantic 
	data set.

Subsidiary or longer-term aims are/were:

(i)	collaborating with European and North American colleagues to produce a 
	"Summer of '97" synoptic view of the northern North Atlantic circulation, 
	particularly WOCE sections A1 (55N) and A2 (48N), AR7W (Labrador Sea), 
	with ancilliary data such as satellite altimetry (ERS2, TOPEX/POSEIDON) 
	and floats (Arcane/ Eurofloat, PALACEs);
(ii)	comparisons of PALACE float profiles and inferred surface fluxes with 
	fluxes and profiles measured on board and estimated from climatology;
(iii)	comparisons between model (GCM - OCCAM) output and measured / inferred 
	circulation;
(iv)	testing an acoustic rainfall-measuring buoy.

b.	OVERVIEW

Although the odd spat of nasty weather halted operations for short periods, 
overall the weather was splendid, enabling us to achieve all our major goals 
for this cruise, and several lesser ones. The weather only really deteriorated 
during the final week as autumn drew in, in the vicinity of Rockall. The 
cruise track and station positions are shown in figures 1.1 and 1.2.

The cruise progressed clockwise around the northern North Atlantic, beginning 
in Vigo, Spain on 7 August 1997. The initial work line was 4130'N, between 
9W and 20W. We proceeded directly from Vigo to 9W, 4130N, then out to deep 
water (>5000 m) at 4130'N, 1230'W for 2 test stations, one firing all 
bottles at one depth, one for a bottle profile. Then we ran back to 9W at 8 
kn for an acoustic current profiling survey; the section proper began with a 
station on the 200 m contour at 913'W. Over the next few days, as we worked 
across the southern flank of the Galicia Bank and down the continental slope, 
it became apparent that the LADCP was seriously malfunctioning, and could not 
be persuaded, either by attention to hardware or software, to behave. We 
decided to have a replacement unit, complete but for pressure case, sent out 
to Leixes, the port of Oporto in Portugal. We broke off work immediately 
after station 21 (2200Z, 12 August, 129'W) to run in and collect the gear 
which had been flown out overnight, and was waiting for us on the dockside on 
arrival. A short wait of a few hours in port enabled an unexpected excursion 
for some of the scientific party to a nearby beach to bathe and skylark. We 
departed promptly at 1630Z. Station 22, begun at 0700Z on 14 August, was a 
cast to 2000 m to ensure the watertight integrity of the original LADCP 
pressure case with the replacement transducer head. Station 23 later the same 
day was an 'overlap' station, repeating 21. Thus only a day and a half were 
wasted; and although LADCP data are sparse for this part of the first section, 
we have no less than five ADCP transects, which should give a decent reference 
for subsequent geostrophic calculations.

Station 35 was the 'corner', the last of line along 4130'N, after which we 
turned north-west for the rest of the section along the rhumb (Mercator-
straight) line between 4130N, 20W and Cape Farewell. Stations 21-34 crossed 
the bottom of the Iberian Abyssal Plain. Much of the remainder of the section 
consisted of a rather oblique cut along the Mid-Atlantic Ridge, with stations 
35-40 passing seamounts of the Azores-Biscay Rise and stations 41-42 at the 
bottom of the north-western corner of the King's Trough, a small deep basin 
closed below ca. 3500-4000 m. Passing the Maxwell and Faraday Fracture Zones 
in the vicinity of 27W and 29W (along the track, respectively), we arrived 
at the Charlie-Gibbs Fracture Zone with stations 62-67, where 63 was at the 
bottom of the Southern Transform Valley and 65 at the bottom of the Northern. 
Stations 70-73 spanned the crest of the Reykjanes Ridge, after which we 
descended to the bottom of the Irminger Basin around stations 78-81. Rising up 
the Greenland continental slope with nominal resolution of topography at 250 m 
depth increments, station 92 arrived at the 200 m contour, and station 93, the 
final one on this repeat of IGY section 4, was our closest approach to land, 
in 150 m of water about 2 miles from the coast.

Next we made a low-speed acoustic profiling transect of the western boundary 
current regime, retracing our path back to the position of station 81 in the 
middle of the Irminger Basin, at 5 kn. Thus a 10-minute ADCP average 
translates, with good navigation, to 1.5 km horizontal resolution with about 
<1cm/s accuracy in currents. Following this exercise, we made for the start of 
the next section, the East Greenland Central Section, which was selected by 
consultation with Alexander Sy (BSH, Hamburg), who was out in the same area at 
the same time as us, on the FS Meteor, but circuiting the North Atlantic in 
the opposite sense to us. We had hoped to meet at Cape Farewell, but our 
LADCP-derived delays contrived to make us miss. The Meteor however was engaged 
in a suite of sections down East Greenland as part of the VEINS program, and 
for comparative purposes, we carried out a repeat of the section most 
appealing to us - the most northerly one which still had a narrow continental 
shelf. This began in mid-basin with station 94; topographic resolution was 500 
m nominal, ending in about 300 m water depth 5 miles from the coast, 
surrounded by grounded icebergs, in the dark.

Next we headed north for the Denmark Strait Section. Running from west to 
east, station 103 was our furthest north at 6531'N, finishing at station 110. 
Bad weather was holding us up on what should have been the final station of 
this section in 200 m of water, so it was abandoned and we ran before the 
weather to the start of the final section south of Iceland on 20W. Also, 
since the Greenland shelf is so broad in the region of Denmark Strait, we 
began in about 500 m water depth, so there may be cause for concern over both 
endpoints of the Denmark Strait section.

The Iceland-Scotland Section began with station 111 in 200 m water depth. The 
centre of the Iceland Basin was reached around stations 121-122, after which 
we rose up the western flank of the Rockall-Hatton Plateau. Station 127 was on 
the top of Hatton Bank, 129 was the deepest in the Hatton-Rockall Basin, and 
132-133 were on the top of Rockall Bank. Rockall itself was passed at night in 
murky weather and was just visible, unlit, as a small black lump on a black 
background. Then the Rockall Trough was crossed by stations 134-140. Station 
137 was on the top of Anton Dohrn Seamount. The last three stations, 141-143, 
were on the Hebridean Shelf, after which we went home.

c.	NARRATIVE

Discovery station numbers are given, not the cruise station numbers. For 
stations 1-21, Discovery number = station number + 13201 (so station 1 = 
13202). No Discovery number was alloted to station 22. For station 23 onwards, 
Discovery number = station number + 13200. The last station was 143, Discovery 
13343.

Friday 1st August 1997: Preparations were made for the winding on of the new 
CTD wire. Familiarisation procedures for new marine staff were placed in hand.

Saturday 2nd August 1997: Further cleaning work around the laboratories was 
carried out and a slow start was made at winding on the new CTD wire.

Sunday 3rd August 1997: Wire-winding was continued but great difficulties were 
encountered and little progress was made.

Monday 4th August 1997: Wire-winding resumed and good progress was made, the 
cause of the difficulties having been identified. Storing operations were 
commenced in the forenoon and the port lifeboat lowered to the water. Storing 
was largely completed in the afternoon and at 1645B bunkering operations were 
commenced. At 2055B the winding on of the CTD wire was finally completed and 
at 2220B the bunkering operation was completed.

Tuesday 5th August 1997: Loading of scientific equipment was commenced in the 
forenoon and the lorry backloaded by early in the afternoon. The inflatable 
dinghy was taken away under power for prolonged testing in the afternoon.

Wednesday 6th August 1997: The majority of the scientific staff joined the 
vessel in the forenoon and spent the day setting up and commissioning their 
equipment. Fresh water tanks were topped up. The final members of the 
scientific staff joined the vessel at 2300B.

Thursday 7th August 1997: Familiarisation procedures of scientific staff were 
commenced at 0900B. At 1000B sailing preparations were carried out and at 
1054B the pilot boarded. At 1058B singling up commenced, the vessel proceeded 
to the master's orders and at 1103B all moorings were gone and clear. At 1112B 
the pilot disembarked and the vessel sailed down the Ria Vigo. From 1136B to 
1144B in the wider reaches of the bay, the vessel was stopped in the water to 
facilitate the deployment of the starboard lifeboat to the water. At 1218B 
with the Isla Boreiro light bearing 025T X 1.9', full away was ordered and 
the vessel proceeded into the open sea. Course was set Southwards along the 
meridian of 009 00'W and at 1600B course was altered to the West along the 
latitude of 4130.0'N, our first line of survey. At 1600B also, alarms were 
sounded and staff proceeded to emergency drill stations, followed by muster at 
and boarding of the boats and instruction for the deployment and boarding of 
the liferafts. At 2040B the Precision Echo Sounder fish (PES) was deployed.

Friday 8th August 1997: At 0650B the vessel was hove to in readiness to 
commence the first of two test stations. At 0757B the CTD+ was hove outboard 
to commence station 13202, the first of two test stations, which finished 
1018B. The second test station 13203 commenced at 1245B and was back inboard 
at 1638B. These and future stations were to consist of the lowering of a CTD 
rig overside with watersampling bottles attached along with an LADCP system 
and a fluorometer. At 1640B course was set 090T at 8 knots of the ground to 
carry out an ADCP and PES survey to the point of origin of the survey line in 
position 4130.0'N 00900.0'W. The Principal Scientist and the master met 
together to review the progress of the cruise and make plans for the future on 
the first of many occasions. Frequent forked lightning displays were observed 
to the East as the ship headed back overnight.

Saturday 9th August 1997: The day opened with but light airs giving a calm sea 
with a very low swell, the skies were cloudy and visibility was but moderate. 
As the morning progressed and the ship came into shoaler water thick fog 
developed. Having just cleared the fog the vessel reached the end of the 
survey line in position 4130'N 00859.91'W at 1145B. Coming about and re-
entering the fog the first station of the day 13204 was occupied. In the 
afternoon the skies cleared and bright sunny weather gave everybody an 
optimistic mood. After station 13205, an LADCP fault caused a delay before the 
commencement of each of the next two stations.

Sunday 10th August 1997: The day opened with light airs, a glassy sea and a 
low swell, cloudy skies prevailed at first but soon cleared to give an almost 
tropically warm sunny day. Stations 13208-11 were occupied.

Monday 11th August 1997: The start of the day was with winds of force 4 from 
SSE, a slight sea was running with a low swell and skies were cloudy and 
overcast, a slight haze reduced the visibility. Stations 13212-7 were 
occupied.

Tuesday 12th August 1997: The day opened cloudy and overcast with light rain, 
the winds were from the South South West at about 8 knots, the sea was rippled 
with a low swell. Stations 13218-13221 were occupied.

Wednesday 13th August 1997: At 0012B with the rig from station 13222 inboard 
and secured course was set to 097T for the port of Leixes in Portugal to 
where spares for the LADCP were being airfreighted from the U.K., the LADCP 
not having been functioning properly. The day opened with light variable airs 
and a rippled sea with a low swell, skies were fine and clear with clear 
horizons. Between 1047B and 1104B the PES fish was recovered. At 1443B the 
pilot boarded in the approaches to Leixes (the seaport for Oporto), the 
vessel secured on berth at 1540B. The port authorities boarded in order to 
complete the necessary formalities and the spares were loaded. The vessel was 
cleared to sail by the port authorities at 1830B, letting go the berth at 
1831B the vessel sailed down the harbour, the pilot disembarking at 1843B. 
Full away was rung at 1854B with the breakwater bearing 060T by 0.9' and 
course was set to 332T. The vessel proceeded at full speed to the parallel of 
4130'N and then altered course to 270T.

Thursday 14th August 1997: The day opened with the wind from North by West at 
9 knots with a slight sea and low to moderate swell, skies were generally fine 
and horizons clear. At 0909B a deployment of the casing for the new LADCP 
casing to 2000 m was commenced in order to give it a pressure test. This was 
not given a Discovery station number, but it was given a scientific one (22). 
The PES fish was re-deployed at 0930B. At 1030B the CTD rig was brought 
inboard and course set to the West. Station 13223 was occupied in the evening.

Friday 15th August 1997: The day opened generally cloudy with a fine haze, 
winds were from the North West at about 10 knots giving a rippled sea with a 
low swell. At 1600B all hands were exercised and trained at emergency drills, 
completing with a muster at boat stations. Stations 13224-13227 were occupied.

Saturday 16th August 1997: The day opened with cloudy skies, the wind being 
from the South West by West at 11 knots giving a slight sea accompanied by a 
low swell. On station 13230 29 minutes were lost when the rig had to be 
recovered after initial deployment, a system malfunction having occurred with 
some of the equipment mounted on the frame. Stations 13228-30 were occupied.

Sunday 17th August 1997: Light rain fell most of the night, clearing away with 
the dawn when skies were cloudy and clear, with the wind from West by North at 
8 knots giving a rippled sea with a low swell. Stations 13231-3 were occupied.

Monday 18th August 1997: A series of small depressions passing just north of 
the vessel caused freshening winds overnight and slowed the vessel's progress 
somewhat between stations. The last station on the direct East to West line, 
13235, was then occupied in the morning. Stations 13234-7 were occupied.

Tuesday 19th August 1997: In the early morning freshening winds blew from the 
South West at about force 4, with the dawn they backed into the North West 
bringing rain showers, seas were slight to moderate with a low swell. Stations 
13238-41 were occupied.

Wednesday 20th August 1997: After further overnight rain the day opened with 
the wind from South West by West at 18 knots giving a moderate sea with a low 
swell, skies were clouded with low overcast and visibility through the day was 
generally moderate. In the forenoon the crew was mustered and both lifeboats 
swung out to the embarkation deck. A safety committee meeting was held in the 
ship's library at 1030B. In the afternoon a slight diversion from track was 
made in response to a distress call relayed from Falmouth Marine Rescue Co-
ordination Centre, course was altered at 1350B and resumed at 1425B after 
receipt of message informing us that the alarm had been accidentally 
triggered. Stations 13242-5 were occupied.

Thursday 21st August 1997: Fog, mist and rain overnight gradually cleared away 
in the morning and at dawn the wind was from South West by West at 20 knots 
with moderate seas and a low swell, skies were cloudy and overcast with 
moderate visibility. Stations 13246-9 were occupied.

Friday 22nd August 1997: A cool gray, cloudy, overcast dawn with light 
variable airs, a rippled sea and low swell presaged. Emergency fire and boat 
drill took place between 1615B and 1630B. Stations 13250-3 were occupied.

Saturday 23rd August 1997: The weather at the start of the day gave promise of 
fine weather, skies being fine with some cumulus cloud, winds were variable 
and light at about 4 knots with a rippled sea and a low swell. Stations 13254 
to 13257 were occupied. In the evening, in deteriorating weather, slow 
progress was made from station 13257 to 13258.

Sunday 24th August 1997: At 0300B having arrived upon the next station 
position the decision was made to suspend operations due to winds of 40 to 45 
knots which were blowing accompanied by a heavy swell. At dawn the skies were 
heavily clouded and overcast, winds were from North West by West at about 30 
knots with moderate to rough seas and moderate to heavy swells. At 0856B with 
conditions moderating the vessel came about and at 1013B resumed station. 
Stations 13258-9 were occupied during the remainder of the day.

Monday 25th August 1997: At 0200B the ship's clocks were retarded one hour to 
Alpha time. Light rain overnight persisted into the forenoon, the day opening 
with winds from the North North East at 6 knots giving a rippled sea 
accompanied by a low swell with cloudy overcast skies. Stations 13260-4 were 
occupied.

Tuesday 26th August 1997: The day opened with freshening winds from North West 
by West at 30 knots, a moderate sea and swell were accompanied by skies that 
were cloudy and fine with good visibility. Stations 13265-8 were occupied.

Wednesday 27th August 1997: The day opened with winds from North West by West 
at 20 knots, giving a moderate sea and swell, with heavy cloud and overcast 
with frequent passing showers. Stations 13269-73 were occupied.

Thursday 28th August 1997: The day opened cloudy overcast and clear, winds 
were from the North West by West at 13 knots with a slight sea and a low 
swell. Stations 13274-7 were occupied.

Friday 29th August 1997: The day opened cloudy and overcast with the wind from 
SSW at 13 knots, seas were slight with a low swell. At 1122A speed was reduced 
to about 8 knots to allow for engine room maintenance work. At 1600A emergency 
drill was held with various instruction classes followed by man overboard 
drill when at 1626A a 'dummy' (representing the Master) was dropped overside. 
The dummy was brought on board with the vessel in the hands of the Mate. The 
vessel was underway again by 1641A. Station 13281 was notable in that during 
the period of the work our first iceberg of the cruise was sighted seven miles 
distant, closer to a growler proved impressive to those unused to working in 
high latitudes, these sightings were about 135 miles from land and just within 
the maximum indicated limit for icebergs in the month of August. Stations 
13278-81 were occupied.

Saturday 30th August 1997: Speed in darkness was now reduced to five knots. 
The day opened cloudy and clear with a wind from West North West at 18 knots 
giving a slight to moderate sea with a low swell. At 1600A, the weather having 
deteriorated with winds reaching force 8 to 9 the vessel hove to and 
scientific work was suspended pending an amelioration of conditions. At 2330A 
it having become apparent that then worst was over the vessel came about and 
steamed towards the next station position. Stations 13282-4 had been occupied.

Sunday 31st August 1997: The vessel resumed station at 0115A and work 
commenced at 0134A. The day opened fine and clear with winds force 3 from West 
by North giving a slight sea accompanied by a low to moderate swell. During 
the afternoon, our second significant piece of ice was passed at about two 
miles distant, a towering pinnacled (Arctic) giant rising to about 297 feet. 
Being now within the maximum iceberg limit speed in the hours of darkness was 
restricted to a maximum of 5 knots. Stations 13285-92 were occupied.

Monday 1st September 1997: The final station of our line from Portugal to 
Greenland was to be 13293 just over two miles from the Greenland coast East of 
Cape Farewell, close to Cape Hoppe. Series 1 was reported as a failure having 
gone to 150 m depth at 0031A, series 2 reached a depth of 150 m at 0055A. At 
0107A, the equipment having been brought inboard course was then set to carry 
out an under way profiling run. The day dawned fine and clear with light 
variable airs giving a rippled sea with a low swell. The profiling run 
continued throughout.

Tuesday 2nd September 1997: Profiling continued until 0350A when arrived at 
position 5805.5'N 04037.44'W course was altered to 036T. At daybreak skies 
were fine and clear the wind however had gathered strength and was blowing 
from the North at about 25 knots giving a moderate sea accompanied by a low 
swell, speed was increased at this time to maximum. Despite being on maximum 
speed however progress was relatively slow, the growth of weed and barnacles 
on the hull and the swell combining to reduce speed at times to seven knots. 
During the hours of darkness, being within the maximum iceberg limit, speed 
was reduced to five knots.

Wednesday 3rd September 1997: Weather conditions moderated overnight and the 
dawn was one of those beautiful occasions with winds from the North at 12 
knots, a roseate sunrise illuminating a deep blue-gray sea under clear skies 
and a few circling seabirds ever hopeful skimming the slight sea and low 
swells in our wake. Passage towards the next line of survey continued until 
arrival on station 13294 at 1308B. At 1823A whilst approaching the next 
station (13295) an experimental rain buoy was deployed astern and remained 
there for most of the station.

Thursday 4th September 1997: The day dawned with very light airs, a glassy sea 
and a low swell under fine and cloudy skies. Stations 13296-13301 were 
occupied.

Friday 5th September 1997: At 0219A on station 13302 the system went down to a 
depth of 293 m. It was not advisable to work closer in towards the coast due 
to the large number of icebergs and at 0234A course was set 118T, then at 
0300A course was set 061T towards the start of the line of positions running 
across the Southern approaches to the Denmark Strait.

Saturday 6th September 1997: In the forenoon, visibility was reduced and 
became quite thick just after noon, in consequence the afternoon was spent at 
reduced speed as the vessel approached the first station (13303) of the line 
across the southern approaches to the strait. When approaching station 13305 
speed was reduced at 2044A and the rain buoy deployed at 2053A. The rain buoy 
deployment was concluded at 2155A. At 2350A the vessel hove to on station 
13306, but due to deteriorating weather work was suspended at 2400A.

Sunday 7th September 1997: At 0720A the vessel proceeded to resume station. 
Winch problems caused a small delay on station 13307. Stations 13306-9 were 
occupied.

Monday 8th September 1997: After station 13310, the vessel reached the next 
station in deteriorating weather conditions, winds coming out of the North 
West at 40 to 45 knots and science was suspended. At 0712A the decision was 
made to abandon the station and in consequence course was set for the line of 
stations commencing from the Southern coast of Iceland and proceeding South 
along the meridian of 20W.

Tuesday 9th September 1997: At 0800A the vessel arrived just a few miles to 
the East of the new (1963) volcanic island of Surtsey and resumed scientific 
work on station 13311 at 0802A. The day had opened with much ameliorated 
conditions, winds were from the West at 5 knots, with a rippled sea and low 
swell, skies were clouded and there was a slight haze but visibility was good. 
Stations 13311-6 were occupied.

Wednesday 10th September 1997: the vessel arrived on the next station at 0412A 
having made slow progress due to deteriorating weather conditions, the vessel 
remained hove to for a while and at 0704A station was resumed. The day opened 
cloudy/overcast and clear with a moderating wind blowing at about 23 knots 
from WNW, seas were moderate to rough and the swell was moderate. Stations 
13317-20 were occupied.

Thursday 11th September 1997: The day opened with fresh winds from the North 
West at 25 knots giving a moderate sea and swell, cloudy and fine with 
occasional showers. From 1414A to 1506A for station 13322, a trial deployment 
was made with a CTD sensor mounted inside a water bottle in parallel with the 
sensor mounted on the frame in attempt to check that time necessary for water 
within an open water bottle to match that of its surroundings, unfortunately 
the the trial failed. At 1600A emergency drill was carried out with various 
classes of instruction in fire fighting and life saving followed by a muster 
at boat stations. Stations 13321-5 were occupied.

Friday 12th September 1997: The day opened with cold Northerly winds at 15 
knots and frequent violent squalls of wind with rain showers, moderate seas 
and swells were running and skies were clouded and overcast. In the evening 
station 13331 took place at 2024A, the vessel now coming up onto the Rockall 
Bank. The last station of the day took place in increasingly unsettled weather 
with heavy swells coming down from the North. Stations 13326-32 were occupied.

Saturday 13th September 1997: Having rounded Rockall, station 13333 to the 
South of St. Helen's reef was occupied. When the next station was attempted, 
problems were experienced with the wire going slack as the ship rose and fell 
in the heavy swells. The decision was made to press on to the next station in 
the hope of some amelioration in conditions occurring. The day dawned with the 
winds from the North West at about 35 knots, with rough seas and heavy swells, 
skies being cloudy and fine with good visibility. Station 13335 took place 
after lunch, however this station was not without incident as during recovery 
at 1430A there was a failure of the CTD termination. Coming up onto the Anton 
Dohrn Bank for station 13337. Stations 13333-7 were occupied.

Sunday 14th September 1997: The day opened with the wind from West South West 
at 20 knots, giving a moderate sea and swell, skies were cloudy and overcast 
with continuous light rain. With station 13341, the vessel was coming onto the 
shelf just West of the Hebrides. After station 13342, the vessel remained on 
site whilst vertical profiling was carried out. On the final station of the 
cruise (13343), the system was finally landed on deck at 1752A, the PES fish 
was brought inboard at 1800A and sampling was completed at 1820A at which time 
a course of 142T was set home in rapidly deteriorating conditions.

Monday 15th September 1997: At midnight conditions had deteriorated so much 
that course was adjusted to 180T in order to ease the extreme movments of the 
ship in the heavy South Westerly swells, at 0200A course was again adjusted to 
210T. At 0500A conditions reached their most extreme as a front approached 
and the vessel manoeuvred variously, once the front had passed an easing of 
the wind strength plus a marked veer in direction enable the vessel to come 
about and assume a course of 110T, this course was maintained until 0800A 
when it became necessary to put a further dog's leg in our progress when 
course was altered to 180T. The day opened with the wind from South West at 
30 knots, seas were still rough with a moderate swell, skies were generally 
cloudy with good visibility. At 0912A in much eased conditions course was 
finally altered to 108T directly towards the North Channel. Progress through 
the Irish Sea however proved slow the run of the tides proving contrary to the 
vessel's progress. Some slight progress towards cleaning up the scientific 
laboratories was made by a now thoroughly worn out scientific complement.

Tuesday 16th September 1997: The day opened with the wind from right ahead 
being South by West at 18 knots, seas were moderate, skies were cloudy and 
overcast with good visibility. Tuskar rock was passed, distant 13.7 miles at 
0800A. Progress was slowed again by contrary tides and the freshening wind 
which although it veered to the South West did not decrease until the vessel 
was approaching the region of Land's End late in the evening. The vessel 
turned Eastwards to head up channel off Wolf rock at 2148A.

Wednesday 17th September 1997: The weather in the English Channel was 
extremely fine and favourable and good progress was made, some lost ground 
being recovered. The day opened fine calm and clear and remained that way with 
glassy sea and sunny skies. Start Point was passed at 0640A distant 4.7 miles. 
End of passage was rung at 1300A and the Needles fairway buoy was passed at 
1308A, at 1357 we were abeam of Hurst Point. At 1429A the pilot boarded just 
before Hamstead Ledge, the vessel entered Empress Dock at 1623A and was 
alongside the berth at 1635A, finished with engines was rung at 1640A and the 
vessel was all secure at 1650A. Scientific staff disembarked soon after.

Captain M. A. Harding

For me, the highlight of the cruise was the East Greenland work. On the way in 
to Cape Farewell, we passed an enormous castellated iceberg with a huge hole 
right through the middle so you could see through to the other side. The lower 
parts of the berg were polished by wave action, and the interior of the hole 
had that shade of ice blue which you don't see anywhere else. The weather was 
glorious - calm, clear, often sunny by day, and starry by night. There were 
regular and improving auroral displays, with greens, whites and occasional 
reds, and lots of swirling arches and wavy curtains. The section in to Cape 
Farewell was completed with station 93, less than 2 miles from the 
extraordinary landscape of rocky pinnacles with ice and snow which is the 
coast of Greenland. The sun had set over the Cape as we finished, and the 
water was so very calm that Jupiter was reflected as a shining path. Seals 
were swimming near the ship. On the second approach to Greenland (not quite as 
close as the first) we had another remarkable sunset, with sunbeams shining 
through the peaks of the coast mountains to illuminate a thin layer of mist in 
a peachy-orange colour.

Sheldon Bacon

Figure 1.1:	Discovery Cruise 230 track Vigo to Southampton. Bathymetry is 200m 
		(solid), 1500m (dots), 3000m (solid).

Figure 1.2:	Discovery Cruise 230 station positions. Bathymetry is 200m 
		(solid). 1500m (dots), 3000m (solid).

2.	CTD MEASUREMENTS
a.	EQUIPMENT

The equipment used during the cruise was as follows:

-	Neil Brown MKIIIb/c CTDs DEEP01 and DEEP02
-	Chelsea Instruments Fluorometer S/N. 88/2050/95
-	Chelsea Instruments Transmissometer S/N. 161/2642/003
-	FSI OCM-D-112 S/N 1325-011592
-	FSI OTM-D-112 S/N 1333-011592
-	Simrad Altimeter 200 m range.
-	LADCP and battery pack
-	FSI Rosette Pylon No.1
-	GO and FSI 10 Litre Niskin Bottles
-	SIS Thermometers S/N T741 and T989
-	SIS Pressure Meters S/N 3192H and 3694H

Both CTDs are MKIIIb instruments converted to a MKIIIc format. Deep02 was 
specially modified for this cruise to accept data from two FSI modules: one 
FSI OTM (Platinum Resistance Thermometer Module) and one FSI OCM (Conductivity 
Module). These mount on a specially modified 10 litre GO water bottle which 
has external rubbers linking the endcaps as opposed to an internal Epoxy 
coated spring.

During this cruise 143 stations were occupied with a depth range of 130-5478 
m. As the 10 mm CTD wire does not have the load capacity to reach depths in 
excess of 4500 m (approx), the 17 mm deep tow cable was used and linked to the 
CTD package with a TOBI swivel. Although the combination of swivel and shackle 
is quite large (1 m approx), there was sufficient clearance to allow the 
package to be deployed without the need to remove the ship's rail. This 
arrangement was used until the deeper stations had been completed after the 
Vigo to Greenland section and performed well. However, in heavier sea 
conditions above Force 6, handling became more difficult due to the closer 
proximity of the package to the ship's side during deployment and recovery.

The sheave over which the cable runs is much further inboard than the 10 mm 
CTD cable. From station 103 onwards, the 10 mm CTD cable was used with a 
swivel fitted between the cable and package. This increased the working 
clearance which proved fortuitous as the majority of bad weather occurred 
after the cable change.

CTD Stations 1-135 were occupied using instrument DEEP01. There was an initial 
problem with loss of the Fluorometer signal at approximately 600 m on each 
upcast. This proved to be a faulty lead connecting the Fluorometer to the CTD. 
After replacement, this gave no further problems. The CTD and other associated 
sensors worked without fault for the duration of the cruise. The FSI pylon 
performed reliably, but after some time failed to fire bottle number 23. As 
sufficient bottles were available, this was not changed for the spare unit. 
The LADCP was fitted to the package for all stations but was not without 
problems (see LADCP report for details).

CTD DEEP02 was mounted on the frame along with the modified 10 Litre bottle 
carrying the FSI OTM and OCM modules. Although the FSI sensors worked both 
Conductivity and Oxygen sensors were unusable along with a loss of Altimeter 
signal. The cast was abandoned and DEEP01 reinstalled and the modified bottle 
removed.

During the upcast of station 136 electrical contact with the CTD was lost. On 
recovery this was traced to a fault in the swivel which had gone electrically 
short circuit. The swivel was removed and DEEP02 plus bottle mounted. The 
Conductivity and Oxygen sensors had been replaced and the loss of Altimeter 
signal traced to a broken connection within the CTD. The remaining stations 
136-142 were completed with this arrangement. The bottle was removed for 
station 143 for fear of damage in the heavy seas as the OTM and OCM protrude 
beyond the safety of the CTD frame.

During the cruise a new software package to acquire and display CTD data was 
under development. Although much remains to be done to bring this to a 
finished product, it proved essential for the stations where CTD DEEP02 was 
used. Due to the non standard format of this instrument, the GO software 
normally used was able to log raw data but not display the multiplexed 
analogue channels. The most important of these for operational use is the 
Altimeter, necessary to avoid sea bed contact. The new software was able to 
handle the data format from DEEP02 and display all data channels.

The level A system failed to log data on three stations but the data were 
recovered with the use of appropriate software designed for the purpose.

John Smithers

b.	DATA CAPTURE

CTD data were passed from the CTD Deck unit to the Level A. The level A 
averaged the raw 16 Hz data to data at 1 Hz. Before averaging, the data are 
checked for pressure jumps and median de-spiked. The gradient of temperature 
over the 1 second sample of data is calculated. From the Level A, data are 
passed to the Level B (logging) and then to Level C (archiving). Bottle firing 
times were logged using a separate Level A.

As with previous cruises, the CTD Level A caused 'serial overruns' when 
accepting and processing data from the CTD deck unit. This caused a loss of 
data of as much as 20 seconds per cast. The problem was alleviated by removing 
the clock input to the Level A. The Level A did not consume processor time 
synchronising with the clock but was able to handle CTD data. Serial overruns 
were still observed but they did not lead to data loss. The internal clock on 
the CTD Level A is sufficiently accurate over a cast if the Level A is allowed 
to communicate with the clock between stations.

The CTD unit DEEP01 was calibrated in the laboratory on the 11th of June 1997. 
A final decision on the calibration will be made after a post-cruise 
calibration. Attached to the CTD were a Chelsea 0.5 m transmissometer and a 
fluorometer. These instruments passed their data via the CTD multiplexed 
channels.

TEMPERATURE

Temperature raw counts were first scaled by (2.1) and then calibrated using 
(2.2):

(2.1)	Traw = 0.0005 x Traw

(2.2)	T = -1.94178E-2 + 0.998608 x Traw

To correct the mismatch in the temperature and conductivity measurements 
temperature is 'speeded up' by (2.3)

(2.3)	T = T + tau(dT/dt)

where the time rate of change of temperature is determined over a one second 
interval. After inspection of 'stairs' beneath Mediterranean water where step 
function changes were observed, the time constant chosen to minimise salinity 
spikes was tau = 0.175s. Temperatures are reported using the ITS-90 scale. ITS-
68 is used for computing derived quantities. Temperatures are converted to 
ITS-68 by (2.4), as suggested by Saunders (1990).

(2.4)	T68 = 1.00024 x T90

PRESSURE

Raw pressure counts were scaled by (2.5) and then calibrated using (2.6):

(2.5)	Praw = 0.1 x Praw

(2.6)	P = -10.94 + 1.0027284 x Praw + 1.36753E-6 x P2raw -1.0313E-10 x P3raw

The pressure sensor is temperature dependent: the CTD gave a larger pressure 
when it was colder. The correction (2.7) gave deck pressures which average to 
-0.0191 dbar with a standard deviation of 0.1220 dbar whilst the CTD was on 
the deck for temperatures varying between 3C and 23C,

(2.7)	P = P + 0.14(ptlag - 25.4)

where ptlag is a lagged version of the CTD temperature, and is constructed by 
(2.8) and (2.9):

(2.8)	W = exp(-tdel/tconst)

(2.9)	ptlag(t0 + tdel) = W x ptlag(t0) + (1 - W) x T(t0 + tdel)

where T is the CTD temperature, tdel is the time interval in seconds over 
which ptlag is updated with tconst = 400 s.

Pressure is adjusted to compensate for hysteresis between down and up casts: 
the pressure hysteresis is a function of the maximum pressure of the cast:

(2.10)	Pout = Pin - { dp6000(Pin) - [(Pin/Pmax) x dp6000(Pmax)]}

where dp6000(P) is the hysteresis and is given in Table 2.1, Pmax is the 
maximum pressure of the cast and Pin is the upcast CTD pressure.

CONDUCTIVITY

Raw conductivity was first scaled by (2.11) and then calibrated with (2.12):

(2.11)	Craw = 0.001 x Craw

(2.12)	C = 0.046595 + 0.9877211 x Craw

The offset and slope were determined using bottles deeper than 2000 dbar over 
stations 001 to 047. Over groups of stations small offsets were added to this 
correction compensating for fluctuations in the CTD or in the bottle sampling. 
The corrections applied to the offset are listed in Table 2.2.

The conductivity sensor was calibrated for the cell material deformation 
correction (2.13):

(2.13)	C = C x (1 + alpha x (T - T0) + beta x (P - P0))

where alpha = -6.5E-6 C-1, beta = 1.5E-8 dbar-1, T0 = 15 C and P0 = 0 dbar.

CTD INSTRUMENT DEEP02

After station 135 and to the end of the cruise, station 143, CTD DEEP02 was 
used. DEEP02 had been modified, pre-cruise, to accept inputs from two FSI 
Ocean Temperature and Conductivity modules. These modules were fitted inside a 
Niskin bottle to investigate the effect of flow through the bottle. The 
intention is to investigate the relationship of water surrounding the Niskin 
sample bottle to that inside the bottle. DEEP02 was calibrated in a similar 
mannor to DEEP01. The following equations were applied (Calibrations from Oct. 
1994),

(2.14)	T = -2.8434E-3 + 1.0067956 x Traw + 7.287E-6 x T2raw

(2.15)	tau = 0.2	

(2.16)	P = 3.42 + 1.002348 x Praw - 3.9467E-6 x P2raw

(2.17)	P = P + 0.28(ptlag - 41.86)

with R2 = 0.97 for n = 7/8 points for 10.6C < ptlag < 13.5C

(2.18)	C = 9.08698E-3 + 1.02002066 x Craw

All offsets, lagged temperatures and conductivity cell model were applied as 
outlined above for DEEP01. The pressure hysteresis data used are given in 
Table 2.3.

SALINITY

After the conductivity calibration, salinity residuals (bottle salinity - CTD 
salinity) showed a depth dependence. This dependence looks like a temperature 
effect in the upper 500 m of the water column and a pressure effect below. The 
shape of the residuals over the station groupings was modelled using pressure 
and temperature,

(2.19)	dsalin = a + bP + cT

where dsalin is the correction to salinity. This correction was then added to 
the CTD salinity. Table 2.4 lists the coefficients determined. Salinity 
residual statistics are given in Table 2.5.

Post-cruise an intercomparison of standard sea water used during the cruise 
revealed that the standard sea water used for stations 001 to 044 lead to 
salinity samples being 0.0015 fresh. Therefore, 0.0015 has been added to CTD 
salinities for these stations. Full details may be found in section 7.f.

ANALYSIS OF BOTTLE SALINITIES IN THE EASTERN NORTH ATLANTIC

Stations 020 to 034 were taken at a latitude of 41.5N between 12W and 20W, 
within the Eastern North Atlantic (ENA). These 15 stations had 73 bottle 
salinity samples taken at potential temperatures colder than 2.5C. Saunders 
(1985) first proposed that the deep basin of the ENA may be used as an oceanic 
calibration facility given that systematic measurement errors between 
instruments (and standard sea water) are bigger than the in situ variations of 
temperature and salinity. Saunders proposed that between 15-30W and 20-46N 
the relationship between potential temperature and salinity could be 
accurately described by the linear fit (2.20):

(2.20)	S = 34.698 + 0.098 x theta

Our bottle salinity samples are 0.0044 fresher with a standard deviation of 
0.0008 than this. Later Mantyla (1994) used two cruises which covered the ENA 
to propose refinements to this line accounting for latitudinal variations. At 
41.5N the relationship given by Mantyla is (2.21):

(2.21)	S = 34.9163 + 0.1000075 x (theta - 2.25)

For this cruise we have (2.22):

(2.22)	S = 34.9143 + 0.100304 x (theta - 2.25)

with R2 = 0.9954. Therefore at 2.25C our data are 0.002 fresher than the 
Mantyla data. For 73 samples spanning 2.0 to 2.5C the mean difference is 
0.0021 fresher with a standard deviation of 0.0008. At 2.25C the salinity 
predicted by the Saunders relation is 34.9185. The S/theta gradient varies 
by about 0.015 psu/C between 20N and 50N (the S/theta gradient is about 
0.1 psu/C at 41.5N). The difference in S/theta gradient in the two 
equations above is much smaller than any latitudinal variation. We therefore 
conclude that the variation between our data and that of Mantyla is due to 
variations in standard sea water and does not suggest any environmental 
difference.

Due to a standard sea water problem, post-cruise it was found that stations 
001 to 044 were 0.0015 fresh. This value has subsequently been added to our 
data making our data 0.0005 fresher than Mantyla, 1994.

OXYGEN

The oxygen model of Owens and Millard (1985) was used to calibrate the oxygens 
(2.23):

(2.23)	O2 = rho x oxysat(S,T) x (Oc - chi) x exp {alpha x [f x TCTD + (1 - 
	f) x Tlag] + beta x P}

where rho is the slope, oxysat(S,T) is the oxygen saturation value after Weiss 
(1970), Oc is oxygen current, chi is the oxygen current bias, alpha is the 
temperature correction, f is the weighting of TCTD the CTD temperature and a 
lagged temperature Tlag computed exactly as the pressure temperature lag 
earlier, and beta is the pressure correction. Five parameters, rho, alpha, 
beta, f, chi were fitted for each station. This approach minimises the 
residual bottle oxygen minus CTD oxygen differences but places complete 
reliance on the bottle oxygens being correct. Oxygens were calculated in 
mol/l. DEEP02, stations 136 to 143 have no CTD oxygen data. Table 2.6 gives 
the parameters and the sum square residual for each station.

TRANSMITTENCE, FLUORESCENCE, AND ALTIMETRY

On DEEP01, Fluorescence was converted to voltages (2.24); this is a 
calibration of the voltage digitiser in the CTD. Transmittance was similarly 
calibrated to voltages (2.25). The altimeter had the calibration (2.26) 
applied.

(2.24)	fvolts = -1.7196E-3 + 1.21971E-3 x fraw + 3.48596E-10 x f2raw

(2.25)	trvolts = -1.7196E-3 + 1.21971E-3 x trraw + 3.48596E-10 x tr2raw

(2.26)	alt = 0.2 + 5.148E-2 x altraw - 5.8E-8 x alt2raw

On DEEP02, fluorescence (2.27), transmittance (2.28) and altimeter (2.29) 
calibrations were:

(2.27)	fvolts = -3.44E-4 + 1.21971E-3 x fraw - 2.813E-11 x f2raw

(2.28)	trvolts = -3.44E-4 + 1.21971E-3 x trraw - 2.813E-11 x tr2raw

(2.29)	alt = 4.73E-2 + 5.41E-2 x altraw - 1.9E-8 x alt2raw

DIGITAL REVERSING TEMPERATURE AND PRESSURE METERS

Two digital reversing temperature meters (RTM) were used, T746 and T989 and 
two reversing pressure meters (RPM) P6132H and P6394H. T746 and P6394H were at 
position one on the CTD rosette, T989 and P6132H were at position four. T746 
failed on station 054 due to low battery power. No spare batteries were 
available so the thermometer could not be used throughout the remainder of the 
cruise. After station 054 T989 was placed in position one on the rosette. 
P6132 was calibrated by (2.30):

(2.30)	Pcal = -6.7 + 1.02 x Praw - 3.3E-6 x P2raw

This calibration was obtained from the first 92 stations where it was observed 
that residuals from this instrument had a quadratic shape with depth. The 
other instruments have had no calibrations applied. Table 2.7 summarises data 
from the reversing instruments.

Throughout the cruise no trends or offsets were identified in pressure or 
temperature. There were insufficient data to determine if there are any biases 
between CTD DEEP01 and DEEP02. Post-cruise calibration of pressure and 
temperature sensors will be our method for identifying calibration shifts.

Stuart Cunningham and Mickey Tsimplis

c.	POST CRUISE CALIBRATION

DEEP01

DEEP01 was used on the first 135 out of 143 stations. The post cruise 
calibration showed that the pressure sensor was stable and was continuing to 
give the same pressure response. Therefore, nothing was done to pressure. The 
post cruise temperature calibration revealed that the temperature sensor was 
under-reading by 0.0040C. Too few reversing temperature measurements were 
made to reveal if temperature offsets occurred during the cruise. Therefore, a 
linear difference in time between the pre and post cruise calibrations 
suggests that 0.0028C should be added to the temperatures recorded during the 
cruise. A calibration of +0.0028C has been added to stations 001 - 135. All 
variables dependant on temperature have been recalculated.

DEEP02

DEEP02 was used on stations 136 - 143 in the Rockall Trough. The post cruise 
calibrations were sufficiently different from the pre cruise calibrations that 
the post cruise calibrations were applied to the raw data, ignoring the pre 
cruise calibrations. The following equations were applied (Calibrations from 
Nov. 1997).

TEMPERATURE

Temperature raw counts were first scaled by (2.1) and then calibrated using 
(2.31):

(2.31)	T = 6.0194E-4 + 1.00702 x Traw

Equations and values (2.3) and (2.15) still apply. Temperatures are reported 
using the ITS-90 scale.

PRESSURE

Raw pressure counts were scaled by (2.5) and then calibrated using (2.32). 
Equation (2.17) is replaced by (2.33). The pressure hysteresis data of table 
2.3 are replaced by those of table 2.8.

(2.32)	P = -2.8 + 0.9928896 x Praw - 1.33E-6 x P2raw + 2.015E-10 x P3raw

(2.33)	P = P + 0.28 (ptlag - 19.36)

CONDUCTIVITY

Raw conductivity was first scaled by (2.11) and then calibrated with (2.34). 
The cell deformation correction (2.13) was unchanged.

(2.34)	C = 0.0176 + 0.97959165 x Craw

SALINITY

Following the conductivity calibration salinity residuals were examined for 
pressure and station dependance. There are few stations and no measurements 
deeper than 2500 dbar, so no residal shape was identified. The residual 
statistics are appended to table 2.5.

DIGITAL REVERSING TEMPERATURE AND PRESSURE METERS

Comparisons between CTD DEEP02 and reversing instruments are given in table 
2.9. All relevant information is as reported above for these instruments. 
Neither the means or variances were different from those obtained when using 
DEEP01.

Stuart Cunningham

REFERENCES

Mantyla, A. W., 1994: The treatment of inconsistencies in Atlantic deep water 
	salinity data. Deep-Sea Res., 41 1387-1405.
Owens, W. B., and R. C. Millard, 1985: A new algorithm for CTD oxygen 
	calibration. J. Phys. Oceanogr., 15 621-631.
Saunders, P. M., 1986: The accuracy of measurement of salinity, oxygen and 
	temperature in the deep ocean. J. Phys. Oceanogr., 16, 189-195.
Saunders, P. M. (1990) The International Temperature Scale 1990, ITS-90. 
	International WOCE Newsletter No. 10, p 10.
Weiss, R. F., 1970: The solubility of nitrogen, oxygen and argon in water and 
	seawater. Deep-Sea Res. 17 721-735.

TABLE 2.1: Laboratory measurements of pressure hysteresis for DEEP01 made on 
31/10/94 at 9.44C. Intermediate values of pressure hysteresis are found by 
linear interpolation.

P	dP6000(P)
dbar	dbar
0	0.0
400	3.9
1000	6.0
1500	5.9
2000	4.8
3000	2.0
3500	1.0
5000	0.0
6000	0.0

TABLE 2.2: Corrections to the conductivity offset.

Station		Correction	Notes
numbers		mmho/cm	
001 - 035	-0.0024		westward leg to turning stn.
036		-0.0047	
037 - 039	-0.0026	
040 - 049	-0.0010	
050 - 069	 0.0000	
070 - 089	 0.0028	
090 - 093	 0.0118		fresh and shallow stations
094 - 097	 0.0028	
098 - 102	 0.0118		fresh and shallow stations
103		-0.001	
104 - 110			bts-us=-5.45e-8xstatno+6.722e-2
104 - 110	-0.007	
111 - 129	 0.0052	
130		 0.0012	
131 - 135	 0.0073		135 last station with DEEP01
136 - 140	 0.0000		136 first station with DEEP02
141 - 143	-0.0031		143 end of cruise

TABLE 2.3: Laboratory measurements of pressure hysteresis for DEEP02. 
Intermediate values of pressure hysteresis are found by linear interpolation.

P	dP5500(P)
dbar	dbar
0	0.0
100	0.9
200	1.6
300	2.1
400	2.3
500	1.9
1000	4.3
1500	4.6
2000	4.0
2500	3.7
3000	2.7
3500	2.1
4000	1.5
4500	0.9
5500	0.0

TABLE 2.4: Salinity correction coefficients

Stations	a	b		c		Notes
001 - 035	0.838	-0.000017	-0.460610	westward leg
036 - 049	0.800	-0.000191	-0.419474	
050 - 069	1.782	-0.000113	-0.508926	
070 - 089	1.875	-0.000234	-0.616385	
090 - 093	1.947	-0.000594	-0.404307	
094 - 097	1.875	-0.000234	-0.616385	
098 - 102	1.947	-0.000594	-0.404307	
103 - 135	2.360	-0.000254	-0.453748	135 last DEEP01
136		15.079	-0.003484	-0.871264	first DEEP02
137		-1.927	-0.004599	 0.480528	
138		-3.178	 0.003279	 0.511432	
139		7.312	-0.001061	-0.200623	
140		11.539	-0.002944	-0.578537	
141 - 143	0	 0		 0		end of section

TABLE 2.5: Salinity residual statistics

Stations	all p	all p	all p		p>2000	p>2000	p>2000
		mean	stdev	n		mean	stdev	n
001 - 035	 0.0000	0.0012	650/688		 0.0000	0.0009	152/163
036 - 049	-0.0001	0.0018	317/321		 0.0000	0.0007	51/52
050 - 069	-0.0001	0.0011	409/451		 0.0000	0.0008	74/77
070 - 089	 0.0000	0.0015	507/534		-0.0002	0.0010	60/63
094 - 097	 0.0000	0.0015	507/534		-0.0002	0.0010	60/63
090 - 093	-0.0002	0.0016	82/111			
098 - 102	-0.0002	0.0016	82/111			
070 - 102	 0.0000	0.0012	557/645			
104 - 110	 0.0000	0.0009				
111 - 129			p>1500		 0.0000	0.0007	51/55
130 - 135	 0.0000	0.0011				
001 - 135	 0.0000	0.0018	2554/2659	 0.0000	0.0009	366/385
136 - 143	0.0000	0.0016	110/112		<-- post 	cruise	
001 - 143	 0.0000	0.0011	2483/2781	 0.0000	0.0009	370/389

TABLE 2.6: Oxygen coefficients and sum square residuals

num	rho	alpha	beta		f	chi	n	sumsq
								mol/l
001	2.2825	-0.0270	 0.0001684	0.2603	-0.033	22	0.71
002	2.2628	-0.0263	 0.0001957	0.2653	-0.055	19	3.04
003	2.4315	-0.0241	 0.0007435	0.0000	-0.111	 6	1.11
004	2.2825	-0.0270	 0.0001684	0.2603	-0.033	22	0.71
005	2.2844	-0.0279	 0.0000638	0.2358	-0.005	13	1.40
006	2.6819	-0.0270	 0.0003048	0.7497	-0.126	15	9.18
007	2.4749	-0.0336	 0.0001282	0.5787	-0.033	20	1.59
008	2.4324	-0.0300	 0.0001735	0.5399	-0.060	17	1.86
009	2.2763	-0.0221	 0.0002494	0.2377	-0.083	15	1.79
010	2.3307	-0.0265	 0.0001970	0.3299	-0.058	20	2.40
011	2.3818	-0.0270	 0.0002109	0.2517	-0.067	19	2.03
012	2.3456	-0.0236	 0.0002328	0.0078	-0.075	19	1.65
013	2.2872	-0.0250	 0.0002059	0.2344	-0.056	20	2.22
014	2.3238	-0.0273	 0.0001851	0.2970	-0.044	21	2.75
015	2.2988	-0.0257	 0.0001956	0.2651	-0.047	21	3.38
016	2.3099	-0.0271	 0.0001919	0.3056	-0.045	20	1.66
017	2.3219	-0.0252	 0.0002421	0.2369	-0.073	18	2.84
018	2.3162	-0.0249	 0.0002150	0.1653	-0.058	15	2.01
019	2.3629	-0.0285	 0.0001726	0.2765	-0.033	21	1.39
020	2.4225	-0.0287	 0.0001792	0.3771	-0.041	21	1.49
021	2.4291	-0.0296	 0.0001732	0.3683	-0.037	20	1.21
022	2.3886	-0.0286	 0.0001741	0.2549	-0.033	20	1.61
023	2.3886	-0.0286	 0.0001741	0.2549	-0.033	20	1.61
024	2.3886	-0.0286	 0.0001741	0.2549	-0.033	20	1.61
025	2.4124	-0.0249	 0.0002266	0.2634	-0.067	22	1.43
026	2.4270	-0.0283	 0.0001877	0.2922	-0.045	22	1.35
027	2.3836	-0.0288	 0.0001754	0.2180	-0.033	21	1.59
028	2.4391	-0.0283	 0.0001899	0.1251	-0.046	18	1.25
029	2.3690	-0.0307	 0.0001493	0.3272	-0.012	19	1.63
030	2.3380	-0.0272	 0.0001888	0.2055	-0.038	18	1.29
031	2.3542	-0.0293	 0.0001407	0.1468	-0.005	19	1.25
032	2.4067	-0.0290	 0.0001747	0.2487	-0.035	18	1.72
033	2.4206	-0.0301	 0.0001696	0.3481	-0.030	19	0.98
034	2.4523	-0.0281	 0.0001866	0.1682	-0.043	20	1.02
035	2.2878	-0.0269	 0.0001771	0.2669	-0.019	19	1.49
036	2.3696	-0.0286	 0.0001691	0.2794	-0.025	19	1.15
037	2.6065	-0.0326	 0.0001459	0.1831	-0.026	18	0.99
038	2.2542	-0.0272	 0.0001688	0.2040	-0.008	18	1.70
039	2.2542	-0.0272	 0.0001688	0.2040	-0.008	18	1.70
040	2.3552	-0.0302	 0.0001615	0.3183	-0.013	18	1.73
041	2.3939	-0.0310	 0.0001483	0.2621	-0.011	19	1.88
042	2.3557	-0.0307	 0.0001372	0.2276	-0.001	19	1.63
043	2.3362	-0.0295	 0.0001350	0.2239	 0.004	15	1.83
044	2.2448	-0.0295	 0.0001289	0.2208	 0.018	18	2.34
045	2.3659	-0.0306	 0.0001301	0.1685	 0.006	22	1.31
046	2.3208	-0.0294	 0.0001391	0.3293	 0.006	20	1.53
047	2.2890	-0.0305	 0.0001183	0.2582	 0.026	20	1.59
048	2.4680	-0.0360	 0.0000775	0.0842	 0.042	18	1.19
049	2.3151	-0.0315	 0.0001177	0.1381	 0.024	20	1.64
050	2.3796	-0.0335	 0.0001086	0.1631	 0.027	18	1.83
051	2.3648	-0.0320	 0.0001186	0.1692	 0.018	19	2.03
052	2.3658	-0.0317	 0.0001164	0.1449	 0.023	19	2.03
053	2.4367	-0.0347	 0.0000997	0.0315	 0.030	21	1.50
054	2.3321	-0.0353	 0.0000864	0.1329	 0.051	17	1.48
055	2.3887	-0.0336	 0.0001113	0.0737	 0.019	22	1.75
056	2.2867	-0.0324	 0.0001171	0.2662	 0.029	18	1.74
057	2.4469	-0.0330	 0.0001462	0.3965	-0.013	17	1.19
058	2.2070	-0.0323	 0.0001179	0.3879	 0.037	20	1.11
059	2.3013	-0.0325	 0.0001095	0.1302	 0.032	21	1.61
060	2.3664	-0.0316	 0.0001234	0.2593	 0.010	19	1.59
061	2.3066	-0.0303	 0.0001216	0.1403	 0.019	20	0.80
062	2.2269	-0.0295	 0.0001201	0.2851	 0.029	18	1.12
063	2.2864	-0.0326	 0.0001183	0.2685	 0.027	17	1.04
064	2.2957	-0.0321	 0.0001178	0.1529	 0.027	17	1.20
065	1.9973	-0.0291	 0.0000906	0.1577	 0.092	18	1.59
066	2.2988	-0.0317	 0.0001160	0.1189	 0.025	15	1.22
067	2.2861	-0.0331	 0.0001183	0.2724	 0.024	18	1.26
068	2.2786	-0.0305	 0.0001307	0.3364	 0.014	20	1.03
069	2.2814	-0.0305	 0.0001131	0.1592	 0.027	20	1.19
070	2.3036	-0.0295	 0.0001210	0.1306	 0.018	18	0.48
071	2.2927	-0.0321	 0.0001226	0.2229	 0.021	18	0.72
072	2.2868	-0.0327	 0.0001166	0.2158	 0.027	18	1.03
073	2.2770	-0.0314	 0.0001248	0.2770	 0.022	17	1.57
074	2.2802	-0.0309	 0.0001297	0.2710	 0.019	21	0.94
075	2.2844	-0.0327	 0.0001218	0.2533	 0.025	22	1.17
076	2.1222	-0.0308	 0.0001008	0.0920	 0.062	21	1.58
077	2.1222	-0.0308	 0.0001008	0.0920	 0.062	21	1.58
078	2.1828	-0.0308	 0.0001058	0.0211	 0.048	19	1.12
079	2.2759	-0.0296	 0.0001229	0.2951	 0.019	19	1.08
080	2.2847	-0.0340	 0.0001149	0.2511	 0.029	19	1.36
081	2.3079	-0.0297	 0.0001288	0.1159	 0.009	17	1.19
082	2.0535	-0.0313	 0.0000974	0.1836	 0.075	20	1.19
083	2.3156	-0.0325	 0.0001301	0.1584	 0.012	19	1.50
084	2.2733	-0.0313	 0.0001157	0.1963	 0.026	15	1.54
085	2.3008	-0.0328	 0.0001172	0.2376	 0.023	21	1.12
086	2.3008	-0.0328	 0.0001172	0.2376	 0.023	21	1.12
087	2.2812	-0.0401	 0.0000892	0.0706	 0.052	22	1.40
088	2.2657	-0.0414	 0.0000997	0.2733	 0.051	17	1.03
089	2.2158	-0.0439	 0.0000639	0.3214	 0.082	15	1.25
090	2.2440	-0.0395	 0.0000822	0.3276	 0.047	11	0.88
091	2.2968	-0.0262	 0.0001929	0.2442	-0.009	 9	0.86
092	2.4012	 0.0506	 0.0012555	0.5984	-0.208	 4	0.97
093	2.1295	-0.0395	 0.0001195	0.0000	 0.070	 5	2.15
094	2.2812	-0.0342	 0.0001146	0.2662	 0.029	20	1.16
095	2.2994	-0.0332	 0.0001078	0.1666	 0.033		
096	2.2994	-0.0332	 0.0001078	0.1666	 0.033	17	1.13
097	2.2815	-0.0289	 0.0001296	0.0321	 0.018	18	1.83
098	2.2734	-0.0365	 0.0001079	0.2735	 0.039	16	1.24
099	2.2884	-0.0256	 0.0001662	0.2640	-0.008	17	1.42
100	2.2862	-0.0265	 0.0001815	0.2577	-0.006	13	1.24
101	2.3244	-0.0221	 0.0002181	0.1490	-0.028	10	1.51
102	2.2439	-0.0359	 0.0001770	0.2856	 0.024	 6	0.58
103	2.3530	-0.0595	 0.0000412	0.0000	 0.069	 9	1.38
104	2.2769	-0.0403	 0.0000218	0.0000	 0.075	 8	1.67
105	2.3269	-0.0125	 0.0002820	0.1692	-0.076	14	1.34
106	2.2973	-0.0268	 0.0001603	0.2879	-0.006	19	1.81
107	2.2587	-0.0344	 0.0001165	0.3550	 0.033	22	1.18
108	2.2881	-0.0287	 0.0001474	0.2767	 0.005	14	1.75
109	2.2819	-0.0281	 0.0001598	0.2716	 0.001	14	1.32
110	2.2290	-0.0352	 0.0001361	0.1328	 0.040	11	1.50
111	2.2798	-0.0731	-0.0005178	0.1834	 0.351	 6	1.22
112	2.2412	-0.0433	 0.0000336	0.0232	 0.112	 9	1.12
113	2.2748	-0.0262	 0.0001944	0.1882	-0.012	12	1.27
114	2.3349	-0.0431	 0.0000342	0.0000	 0.096	13	1.43
115	2.3349	-0.0431	 0.0000342	0.0000	 0.096	13	1.43
116	2.2806	-0.0303	 0.0001356	0.2869	 0.014	18	1.38
117	2.2795	-0.0297	 0.0001416	0.2619	 0.011	18	1.46
118	2.3396	-0.0333	 0.0001178	0.1466	 0.022	17	1.36
119	2.2927	-0.0277	 0.0001506	0.2554	-0.001	18	1.67
120	2.4523	-0.0335	 0.0001445	0.5229	-0.014	20	1.21
121	2.3220	-0.0323	 0.0001284	0.2501	 0.016	20	1.22
122	2.3252	-0.0343	 0.0001170	0.3029	 0.023	20	1.42
123	2.2708	-0.0292	 0.0001507	0.2537	-0.004	14	2.37
124	2.2764	-0.0316	 0.0001295	0.2799	 0.020	15	1.55
125	2.2765	-0.0311	 0.0001509	0.3369	 0.008	15	0.98
126	2.3183	-0.0267	 0.0001909	0.3770	-0.020	11	1.42
127	2.2652	-0.0256	 0.0001868	0.1504	-0.013	 9	1.20
128	2.5701	-0.0293	 0.0002347	0.4126	-0.064	10	0.93
129	2.3546	-0.0366	 0.0000932	0.4402	 0.032	11	1.36
130	2.3133	-0.0593	-0.0002698	0.0000	 0.310	 8	3.40
131	2.2930	-0.0329	 0.0001654	0.3108	 0.019	 5	0.86
132	2.2733	-0.0498	 0.0001655	0.1263	 0.104	 5	0.12
133	2.2682	-0.0532	 0.0000126	0.1704	 0.139	 4	0.24
134	2.2600	-0.0357	 0.0001008	0.4163	 0.044	 9	1.21
135	2.2826	-0.0277	 0.0001842	0.2604	-0.019	10	0.79

TABLE 2.7: Upcast CTD value minus reversing instrument. Temperature differences 
have been calculated within 0.5C then 2 sd, pressure differences have been 
taken within 25 dbar then 2 sd. n points is the number of points in the mean 
over the total number of data points.

all P		mean	sd	n points
T989 C		0.0139	0.0088	104/122
T746 C		0.0280	0.0098	47/52
P6394 dbar	1.2	1.8	116/130
P6132 dbar	0.1	1.0	101/119
P>2000 dbar	mean	sd	n points
T989 C		0.0149	0.0041	46/58
T746 C		0.0277	0.010	45/50
P6394 dbar	0.86	1.6	77/97
P6132 dbar	-0.24	1.1	27/40

TABLE 2.8: Post-cruise laboratory measurements of pressure hysteresis for 
DEEP02. Intermediate values of pressure hysteresis are found by linear 
interpolation.

P	dP5500(P)
dbar	dbar
0	0.0
100	0.9
200	1.6
300	2.1
400	2.3
500	1.9
1000	4.3
1500	4.6
2000	4.0
2500	3.7
3000	2.7
3500	2.1
4000	1.5
4500	0.9
5500	0.0

TABLE 2.9: Upcast CTD value minus reversing instrument. Temperature 
differences have been calculated within  0.5C then  2sd, pressure 
differences have been taken within  25 dbar then  2 sd. n points is the 
number of points in the mean over the total number of data points. For post-
cruise DEEP02 calibration.

all P		mean	sd	n points
T989 C		0.0033	0.0005	6/7
T746 C		0		
P6394 dbar	2.5	3	6/7
P6132 dbar	-0.5	1.7	6/7

3.	LOWERED ADCP MEASUREMENTS
a.	DESCRIPTION

The LADCP package consisted of a RDI 150kHz BroadBand ADCP (phase III) with a 
pressure case rated to 6000 meters and 4 downward facing transducers with 20 
degree beam angles. The LADCP was fitted centrally in the CTD rosette frame 
and power during casts was supplied from a second pressure case containing a 
48 volt alkaline battery pack mounted horizontally near the bottom of the 
frame. The battery pack pressure case was aligned so that batteries could be 
replaced by simply removing the end cap of the case. A short lead was left 
permanently attached to the unit and tied to the frame to enable the external 
power/communications lead to be attached pre- and post-deployment.

A 15 m communications/power lead was routed through the Bottle Annex and Deck 
Lab and connected to a dedicated PC and power supply situated on the port side 
of the Deck Lab. While attached to the instrument the cable was taped to the 
CTD frame and draped over a deck light bracket to keep it clear of the boots 
and heads of samplers. During casts the free end of the cable was fed back 
through the opening into the Bottle Annex to keep it dry. For most of the 
cruise the CTD package was kept permanently at the aft end of its deck tracks, 
so it was necessary to extend the 15m cable with a spare short lead to enable 
connection. During set-up prior to a cast and for downloading data, external 
power was supplied to the unit via the communications lead. There is 
sufficient diode protection inside the ADCP for the battery supply to be 
overriden by applying external power at a slightly higher voltage (i.e. 50 
volts, with the battery packs used on this installation).

Prior to each cast the instrument was subjected to a series of tests and sent 
a configuration (command) file which determines the mode of operation. The 
test results and deployment files were recorded for each cast. With some 
exceptions, the instrument was set to Water and Bottom Tracking Mode with 16 m 
bins and 10-bin ensembles for the whole cruise. The LADCP clock was checked 
and corrected if it was found to be more than 1 second from GMT. The power and 
communication cable was disconnected and a blank plug placed on the lead to 
the instrument and taped to the frame for security.

A total of 16 battery packs were available for the cruise, and 8 eventually 
used. The 48 volt alkaline battery packs (32 x 1.5 volts) were replaced when 
the power level dropped to around 34-35 volts to avoid potential data loss. 
The life of the battery packs ranged from 37,000m to 110,000m of casts, with 
an average of 91,000m per pack. The packs which had a shorter life were those 
used in regions with many shallower casts, ie a relatively high time spent 
within Bottom Tracking range. One pack was used solely in water tracking mode 
and was found to use approximately the same amount of battery power as the 
casts set to Bottom Tracking Mode over deeper casts (>1500m).

b.	INSTRUMENT PROBLEMS

During the early part of the cruise performance of the LACDP was not wholly 
satisfactory. Data appeared to be logged correctly during the downcast but not 
for the whole of the upcast. Also, the power/communications cable was 
inadvertently disconnected whilst data was being downloaded. Further 
communications with the instrument failed after this. The pressure case was 
opened and the fault traced to 2 communication line fuses which had blown. 
These were of a wired in type of which no spares we carried. Fortunately, 2 
were available from unused channels which were removed and resoldered in the 
appropriate lines. Communications were then re-established. The original 
problem with data loss continued however, and lack of any spare boards or 
parts resulted in a port call to Leixes (Oporto). Spare boards, transducer 
assembly and a complete electronics chassis were flown to Oporto. Rather than 
attempt to identify the exact cause of the problem it was decided to replace 
the transducer assembly and electronics chassis in total. The power 
conditioning circuit board from the original instrument was retained as this 
included the appropriate connections to the endcap. Before fitting the 
electronics chassis a cast to 2000 metres was performed with just the pressure 
case and transducer assembly to test the water tight integrity. This proved 
successful and the instrument was finally assembled. The complete set of tests 
available from the software suite was run and the instrument passed all 
satisfactorily.

Data logging for both up and down casts was now satisfactory and it was also 
noted that the Ping from the transducers could now be heard or at least sensed 
which was not the case with the original instrument.

c.	DATA PROCESSING

This section briefly outlines the method of LADCP current calculation and the 
data processing path taken on D230. In essence the LADCP measures 
instantaneous relative velocities of scatterers in the water column and these 
can be converted into profiles of absolute currents by an elaborate processing 
path. The scatterer velocities are measured by utilising the Doppler frequency 
shift, phase changes and correlation between coded pulses transmitted and 
received by the four tranducers. The raw data must be scaled to velocity units 
by taking into account the depth and temperature dependent sound velocity 
(from CTD data). The directions can be inferred from trigonometric 
calculations based on the geometry of the transducer set, the orientation of 
the package (measured with a flux gate compass) and the local magnetic 
variation from true north. The depth of the instrument was first calculated by 
integrating the measured vertical velocity and later fine-tuned by matching to 
the CTD time and pressure data.

Velocity data are collected in 16m bins and each ping produces 10 bins which 
make up an ensemble. In order to remove relative velocites introduced by the 
motion of the package during the cast, shear profiles were calculated by 
differentiating the velocities within each ensemble. The data are then 
integrated up over the cast to produce a shear profile with a zero net 
velocity. This process also removes the barotropic component of the velocities 
which must be reinstated either from the ships displacement (from differential 
GPS data) or from the relative motion of the package over the sea floor 
(Bottom Tracking). The final velocity profile is therefore a sum of the 
baroclinic and barotropic components.

The processing of LADCP data is achieved using software developed by Eric 
Firing at the University of Hawaii. His software uses a combination of 'perl' 
scripts and MATLAB 'm' files to process the data, which are stored in a CODAS 
database. The processing stages were those outlined in the SOC LADCP Data 
Processing Manual written by N.Crisp, L. Beal and R. Tokmakian and are 
summarised below.

1)	Extract binary ADCP files from instrument, and scan it using 'scanbb' to 
	give useful information about the cast - e.g. time in water, out of water, 
	number of good ensembles, and the cast depth as an estimate of integrated 
	vertical velocity.
2)	Load the ADCP data into a CODAS database, including magnetic variation 
	(information provided by the Bridge Officer at each station), nominal cast 
	position, and only including good ensembles specified by the previous 
	'scanbb' step. Raw data files (*.000), database files (*.blk), 
	configuration and control files (*.cmd, *.cnt, *.def), scan files (*.scn), 
	and deployment log and test files (*.txt, *.log) were copied to a location 
	on the SUN using PC_NFS. All these files and their original file structure 
	were periodically compressed and archived to an EO before some were 
	removed from the SUN to conserve space. The necessary database and control 
	files remained in individual cast directories on the SUN and were backed-
	up daily along with all cruise data.
3)	The database files from the PC were converted to SUN format CODAS files 
	using the program 'mkblkdir'.
4)	The perl script 'domerge' calculated mean shear profiles (the baroclinic 
	component of the current) and applied corrections and editing options 
	which were kept constant throughout the cruise. Data were averaged into 5m 
	bins. The MATLAB script 'do_abs' calculated absolute velocities, and 
	produced a standard set of profiles. In the first instance the uncorrected 
	data (down, up and mean profiles) were viewed and plotted as unreferenced 
	shear profiles with the depth-averaged component set to zero.
5)	Next the calibrated CTD data were interactively matched to the ADCP 
	vertical velocities within MATLAB (set_***.m), and the true depth 
	information merged into the CODAS database for the cast, together with 
	sound speed data corrected for temperature and salinity (add_ctd then re-
	run domerge and do_abs).
6)	One method of obtaining absolute currents is to use GPS data during the 
	cast to restore the depth-averaged (barotropic) velocity component 
	(equivalent to the ship's displacement) which was removed when first 
	calculating the shear. For all but 7 days of the cruise the GPS GLONASS 1-
	second data stream was used for calculating the ships displacement. For 
	days ??? to ??? the GPS 4000 1-second data stream was used. The GPS data 
	were subjected to a 5-second filter (pfiltr; 30 seconds for GPS 4000) and 
	subsampled every 5 (30) data points to create a global GPS file (ascii 
	file sm.asc, saved as Matlab file sm.mat). The GPS files were created 
	every few days rather than at the end of the cruise, so in total 10 
	sequential sm.mat files were generated. Some GPS files caused 'non-
	monotonic' errors during do_abs so a short Matlab script was written to 
	identify and remove any rogue non-monotonic rows in the sm.mat files. The 
	absolute profiles calculated by do_abs were plotted and saved to file.
7)	Each cast was rotated through the heading of the cruise track to 
	calculate current components normal to the cruise track for comparison 
	with geostrophic shear profiles from the CTD data (rotate.m). This stage 
	also creates an ascii file containing the mean vertical, east, north, 
	along-track and across-track components. The ascii file was imported into 
	pstar (pascin) with position data extracted from the headers of the 
	corrected CTD files (pinq) rather than the uncorrected positions found in 
	the file latlon.asc created by domerge (ladcp.exec).

d.	BOTTOM TRACKING DATA

On Stations 42 to 143 the LADCP was set to Bottom Tracking (BT) mode in order 
to obtain good measurements of the bottom currents particularly in the deep 
western boundary currents. In this mode the LADCP produces alternating pings 
for water tracking and Bottom Tracking when in range of the sea floor. The 
Firing software does not deal with Bottom Tracking data, so new pstar scripts 
were written to process the data. Following is a brief outline of the steps 
taken during the processing:

1)	Ascii data are extracted from the binary BBADCP files (using conversion 
	file D230BT.FMT and program 'bblist'). Variables extracted include 
	ensemble number, time (Julian Day), BT velocities (east/u, north/v, 
	vertical/w, error), water track velocities (east/u, north/v, vertical/w, 
	error) and the BT range from the bottom from Beams 1/2 and 3/4.
2)	Ascii data read are into pstar (pascin), absent data changed from 9999 to 
	-999 (pedita), and time converted into days of the year (JDay plus 1) then 
	seconds (ptime). User inputs the LADCP clock lag in seconds as necessary.
3)	Currents are rotated by the local magnetic variation (pcmca2, pcalib) and 
	the water velocity over ground calculated for each bin (water track 
	velocities minus bottom track velocities) (parith). This step removes the 
	package motion from the velocities.
4)	The data are merged with CTD data on time (pmerg2) in order to match 
	pressure (depth) data with the velocity profiles. No correction for 
	velocity of sound variation has been made. Each 1 second ensemble then has 
	an associated depth, and next the incremental depth of each bin is 
	calculated according to the binsize specified in the LADCP configuration 
	file.
5)	Finally the data are averaged into depth bins (pbins) specified by the 
	user (eg 16m) and can be compared to the absolute velocity profiles 
	derived from the GPS data.

e.	COMPARISON OF SHIPBOARD AND LOWERED ADCP MEASUREMENTS

INTRODUCTION AND SUMMARY

In order to estimate the accuracy of full-depth profiles of horizontal velocity 
obtained from the Lowered Acoustic Doppler Current Profiler (LADCP), we 
undertook a number of comparisons of the LADCP measurements with shipboard ADCP 
measurements in the upper water column and with bottom-tracking estimates of the 
flow in the bottom 200 m of water column during Discovery cruise 230. For 
comparisons in the upper water column at 31 stations, ADCP and LADCP velocity 
profiles exhibit generally similar structure so the difference at each station 
is estimated as an offset plus a standard deviation about the offset between 
ADCP and LADCP east or north velocities. The average absolute offset in east or 
north velocities is approximately 2.4 cm s-1, while the average standard 
deviation for the vertical variability in structures is approximately 1.7 cm s-
1. For the bottom layer comparisons, the vertical structures of the LADCP and 
Bottom Track velocity profiles are very similar, as might be expected since the 
baroclinic structure is measured by the same instrument. More importantly, the 
Bottom Track currents show reasonable agreement with the absolute currents near 
the bottom as estimated by combining baroclinic LADCP velocity profiles with 
ship movement during station. For four stations in the deep western boundary 
current off Greenland where the bottom currents exceed 10 cm s-1, the absolute 
velocity components for the two methods agreed within about 2 cm s-1. Such 
agreement should help put estimates of the transport of the deep boundary 
current on a firmer foundation.

As discussed above, the LADCP measurements are initially processed as shear 
profiles and then vertically integrated to provide baroclinic profiles of east 
and north velocities. Baroclinic profiles are here defined to have zero depth-
averaged values. The depth-averaged velocity components are then obtained by 
combining the movement of the ship during station as determined from GPS 
navigation with the time series of absolute velocities measured by the LADCP. A 
natural question arises as to the accuracy of the resulting absolute LADCP 
velocity profiles.

We have tried to answer this question of accuracy in two ways. First, we 
compare the LADCP velocities in the upper water column with the station-
averaged ADCP velocities measured with the shipboard system. Secondly, we 
compare the estimates of absolute velocities from the LADCP with bottom-
tracking estimates of the near-bottom flow. We also have plans to pursue a 
third approach to compare the overall LADCP velocity structure with 
geostrophic estimates of the baroclinic shear from simultaneous CTD casts, but 
this approach was not undertaken during Discovery 230.

UPPER OCEAN COMPARISONS

The ADCP measurements, as discussed in Section 5, were initially acquired as 
time averages over two minutes. For a typical CTD station lasting 2.5 hours, 
there are approximately 75 vertical profiles of velocity through the upper 
water column down to about 400 m depth by the shipboard ADCP system. In the 
on-station ADCP velocity profiles, there is inherent variability with a 
typical magnitude of 10 cm s-1 due to noise in ship's position which was 
estimated to be between 5m and 20m from time series of positions logged while 
Discovery was at the pier in Vigo and then Porto . An error of 10 m in ship's 
position translates into an error in velocity over two-minutes of 12 cm s-1. 
Because the individual two-minute ADCP profiles penetrate to different depths, 
time-averaged velocities at each depth were considered to be of reasonable 
quality when at least 10 two-minute averaged velocities were available during 
the period of the station. For such averages, the navigation-induced error in 
the ADCP velocities should be less than 2 cm s-1. An overall average velocity 
profile was estimated for the ADCP east and north velocities measured during 
each of 31 stations.

During a station the LADCP transits through the upper 400 m of the water 
column on the downcast over approximately 20 minutes and again on the upcast 
over about 20 minutes. We display the downcast and upcast profiles in addition 
to the average profile to indicate the variability in the LADCP currents. It 
is the average of the up and down LADCP profiles that is compared 
quantitatively to the shipboard ADCP profile for each station (Figure 3.1).

For comparisons at 31 stations, the shipboard ADCP and LADCP velocity profiles 
exhibit broadly similar vertical structure but with a varying mean offset. In 
order to quantify the agreement then, we estimate the mean difference between 
the shipboard ADCP and LADCP profiles and the standard deviation about the mean 
difference for each profile of east or north velocity on each station (Table 
3.1). The average difference over all 31 stations is less than 1 cm s-1 
indicating that there is no substantial bias between the ADCP and LADCP 
velocities. The similarity in vertical structure is apparent from the standard 
deviations about the mean difference for each station which are only 1.58 cm s-
1 for east velocity and 1.81 cm s-1 for north velocity and there are only 3 
instances where the standard deviation exceeds 3 cm s-1. The overall measure of 
agreement which we prefer is the average absolute difference between the 
shipboard ADCP and LADCP velocities. For east and north velocities, the average 
absolute differences are 2.33 cm s-1 and 2.45 cm s-1 respectively. In summary, 
the absolute LADCP velocities exhibit similar vertical structure to the 
shipboard ADCP velocities and the mean offset between the LADCP and ADCP 
velocities measured on station is 2.4 cm s-1.

BOTTOM BOUNDARY COMPARISONS

For most of the LADCP profiles during Discovery 230, the instrument was set up 
to make alternate bottom-tracking pings as the instrument approaches the ocean 
bottom. Such bottom-tracking provides direct estimates of the movement of the 
instrument which can then be added to the velocity profiles relative to the 
instrument to create absolute velocity profiles for the water column within 
about 200 m of the bottom. Such absolute bottom velocities are effectively 
independent of the bottom velocities estimated in the overall absolute 
profiles because any problems in measuring velocity through the water column 
will not influence the Bottom Track velocities but will cause errors in bottom 
currents in the absolute profiles.

We compare absolute LADCP bottom velocities with Bottom Track velocities at 4 
stations in the deep western boundary current off Greenland where the deep 
velocities are larger than 10 cm s-1. For each of these stations, the scatter in 
Bottom Track velocity and the mean Bottom Track velocity profile are compared to 
the absolute LADCP over the bottom 200 m (Figure 3.2). Again we estimate a mean 
offset and a standard deviation about the offset between the absolute LADCP 
velocity and Bottom Track velocity (Table 3.2). The scatter in Bottom Track 
velocities surprised us. In general, the vertical structure of the average 
profiles is very similar, which should not be surprising because the baroclinic 
profile effectively represents the same measurements for each. The offset, 
however, is an independent quantity as discussed above. For these 4 stations in 
strong bottom currents, the offset varies from 0.04 to 4.14 cm s-1 with an 
average absolute offset of 2.5 cm s-1. The perceptive reader might have noticed 
that in 7 out of 8 cases, the offset suggested by these bottom comparisons has 
the same sign as that suggested by the surface comparisons.

CONCLUSION

Based on comparison of absolute LADCP velocities with on-station shipboard 
ADCP velocities in the upper water column and with Bottom Track velocities in 
the bottom 200 m of the water column, we conclude that the present accuracy of 
absolute LADCP velocities is approximately 2.5 cm s-1. Additional Bottom Track 
comparisons are needed to determine if the absolute LADCP velocities can be 
improved by consideration of the combined offsets for the independent surface 
and bottom comparisons.

Penny Holliday, John Smithers, Harry Bryden and Bob Marsh

TABLE 3.1: Upper ocean differences between ADCP and LADCP currents (cm s-1).

	uADCP-		vADCP-	
	uLADCP		vLADCP
Station	mean	std dev	mean	std dev
30	-1.36	2.14	-4.22	1.90
31	 0.96	1.36	-0.35	2.62
32	-3.05	1.69	 0.44	0.90
33	-4.28	0.98	-4.10	2.07
34	 3.32	2.77	 0.63	2.91
35	-2.98	1.94	 0.03	2.09
36	 1.64	1.25	 1.51	0.76
37	-1.00	1.19	 1.14	1.91
38	 3.36	1.57	 7.51	1.51
39	-4.42	0.62	-3.04	1.60
40	-0.85	2.14	 2.46	2.52
41	-0.36	1.87	-1.00	1.60
56	-4.52	1.42	-0.65	1.91
57	-1.21	2.32	 4.67	3.76
60	-1.18	1.43	 0.61	1.16
80	 3.64	0.96	-2.38	0.90
81	 1.71	1.15	 0.76	0.64
82	 2.77	1.22	-4.25	1.25
83	 4.12	1.23	-0.41	1.50
84	 2.65	0.86	-1.66	1.69
85	 5.47	1.16	-5.92	0.84
86	-2.15	1.34	 0.23	1.08
87	 0.97	1.10	 1.10	1.15
88	 1.29	1.25	-1.48	1.84
89	-0.82	2.52	-2.12	1.35
94	 0.42	0.97	-1.54	0.71
95	 1.62	0.68	 3.51	0.60
96	 5.12	0.71	-1.45	1.98
97	 3.47	1.38	-5.10	1.59
98	 0.70	5.28	 1.04	2.91
99	 4.63	2.39	 6.97	6.86
Average	 0.63	1.58	-0.23	1.81
Average
Absolute 2.33		 2.45	
Difference

TABLE 3.2: Comparison of Absolute LADCP and BottomTrack Velocities in Strong 
Currents off Greenland

			uBT-		vBT-	
			uLADCP		vLADCP
Station	uBT	vBT	Mean	Std Dev	Mean	Std Dev
84	 13.62	-15.57	1.10	0.90	-1.47	1.89
94	-12.09	  4.09	3.68	1.48	 4.14	0.98
95	-14.91	 10.40	0.65	0.85	 2.80	0.92
96	 -2.57	 12.57	0.04	1.19	 2.27	1.22

Average Absolute Difference 2.0 cm s-1

Figure 3.1:	VM- and L-ADCP profile comparisons for station 85; VM-ADCP: short 
		dash; L-ADCP: down (chain), up (long dash), mean (solid).

Figure 3.2:	LADCP water track/bottom track comparison: station 85 bottom track 
		velocity scatter plot with 10m bin average (dashed line) and water 
		track velocity (solid line).

4.	NAVIGATION
a.	BESTNAV

A standard PSTAR navigation file was maintained throughout the cruise. This 
was appended daily with the RVS "bestnav" position data at 30 second 
intervals.

Daily processing:

Level 0 acquisition of RVS 'bestnav' navigation data from level A.

b.	GPS AND GLONASS

An Ashtech GG24 GPS-GLONASS receiver configuration (incorporating a Trimble-
4000 receiver) enabled the acquisition of navigation data (ship position, 
heading, speed over ground, satellite fix parameters) from more than one 
source. Data were acquired every second from the GPS satellite constellation, 
and also from the more accurate "mix" of GPS (US, dithered) and GLONASS 
(Russian, undithered) constellations, dubbed "Glos".

Daily processing:

Step 1:	Level 0 acquisition of GPS navigation data (both GPS-4000 and Glos 
	mix);
Step 2:	Level 1 quality control of Glos data: data is deleted wherever 
	poor positioning accuracy is indicated by satellite fix parameters:
	0 > PDOP > 10
	0 > TDOP > 4
	0 > VDOP > 4
	0 > HDOP > 4
Step 3:	Determination of ship velocity and 2-minute averaging. The east 
	and north components of ship velocity over ground were plotted daily to 
	reveal any gaps in the GPS and Glos, and to indicate the timing and nature 
	of ship manoeuvring (a subsequent aid in the manual editting of ADCP 
	absolute velocity datasets, to eliminate spurious currents arising from 
	ship turns, and to separate on station and underway profiles)

UNCERTAINTIES IN SHIP'S POSITION AND VELOCITY DUE TO NAVIGATION

While Discovery was at the pier in Vigo, positions were monitored using both 
GPS and Glos positioning systems. The standard deviation in 2068 10-second GPS 
positions was about 20 m in east and north components while the standard 
deviation in Glos positions was about 10 m (see table 4.1). Because the 
navigation is primarily used in the ADCP processing for determining ship's 
velocity over two-minute averages, 2 minute differences in ship's position at 
the pier were also estimated. For the GPS positioning, the two-minute 
differences had a standard deviation of 25.2 m in north and 17.6 m in east 
components. Such standard deviations would lead to uncertainties in ship's 
velocity over two-minutes of 21.0 cm s-1 in north velocity and 14.6 cm s-1 in 
east velocity. The standard deviations of two-minute differences in Glos 
position were only 5.3 m in north and 5.0 m in east components. Such standard 
deviations would lead to uncertainties in ship's velocity over two-minutes of 
only 4.4 cm s-1 in north and 4.2 cm s-1 in east velocities. An opportunity also 
arose to monitor positions in Porto for 2.5 hours while Discovery was at the 
pier. The standard deviations in position were similar to those in Vigo, 20 m 
for the GPS positions but only 6 m for Glos. Because the Vigo record is longer, 
we use the Vigo position uncertainties as a measure of the uncertainties in 
ADCP velocities due to navigational uncertainties during Discovery Cruise 230.

UNDERWAY CHANGES IN GPS ACQUISITION

We had to alternate between relatively noisy ship positioning, determined from 
the dithered GPS satellite constellation, and the more accurate Glos 
positioning [having accidentally chosen to switch from GPS/GLONASS mix to pure 
GLONASS from 1200 on day 226 to 1800 on day 232].

c.	SHIP GYROCOMPASS

Two S.G.Brown gyrocompass units are installed on the bridge. Ship heading was 
logged every second via a level A microprocessor.

Daily processing:

Step 1:	Level 0 acquisition of gyro heading data (logged every second) from 
	level A.

d.	ASHTECH 3DF GPS ATTITUDE DETERMINATION

The Ashtech 3DF GPS is a system of 4 satellite-receiving antennae mounted on 
the foredeck and bridge roof of the ship, and a receiver unit in the bridge 
house. Every second the Ashtech measures ship attitude (heading, pitch and 
roll) accurately, and this data is used in a post-processing mode to correct 
ADCP current measurements for 'heading error' (as the ADCP uses the less 
accurate but definitely continuous ship gyro headings to resolve east and 
north components of current). Accompanying each attitude are measures of 
maximum measurement rms error (mrms), and maximum baseline rms error (brms).

To set up the Ashtech, the following 'best' parameter values were set using 
menu 4 on the receiver unit:

in the ATTD SETTINGS sub-menu:

max mrms	0.007m	filter		N
max brms	0.060m	max angle	10 deg.
one sec sampling enabled

in the ATTD CONTROL sub-menu:

max cycle 0.20 cyc
Kalman filter reset N

Note however that setting the latter Y enabled acquisition of the first 
successful attitude data on the evening of day 223.

Daily Processing:

Step 1:	Level 0 acquisition of Ashtech data (heading, pitch, roll, mrms, 
	brms, logged every second) from level A;
Step 2:	Level 1 merging of gyro and Ashtech data;
Step 3:	Level 2 basic quality control of Ashtech data, averaging over 2-
	minute periods, and determination of heading error, 'a-ghdg' (correction 
	applied to gyro data as determined from Ashtech-to-gyro comparison):
Step 4:	Plotting the daily time series of gyro heading, a-ghdg, plus pitch, 
	roll and mrms statistics, to enable inspection for remaining outliers and 
	further editing, and linear interpolation of the tidied-up a-ghdg time 	series

The performance of the instrument throughout the cruise was not without 
problems. Unfortunately the Ashtech can be rather temperamental. It must 
maintain good satellite fixes to continue logging. Once fixes are lost for too 
many minutes, logging is interrupted, and it is necessary to switch off and on 
the receiving unit, and to reset the parameters (which re-assume undesired 
default values). Several specific problems arose in the course of the cruise.

Problem 1: On sailing the instrument proved to be badly parameterized. On day 
	224, after five days, having determined appropriate parameters, we finally 
	started to acquire accurate ship attitude data.
Problem 2: Logging stopped at 0300 on day 226, and this was not noticed until 
	0330 on day 227. It was necessary to switch the receiver off, clearing the 
	internal memory, and resetting the appropriate parameters. Thereafter the 
	instrument was carefully monitored, and performed at an acceptable level 
	over the following 10 days.
Problem 3: There was a sudden failure to determine attitude after 1141 on day 
	237 (although position continued to be accurately fixed thereafter), 
	discovered upon daily processing of Ashtech data on day 238 (watch checks 
	only confirmed that Ashtech data was being logged). Initial efforts to 
	solve the problem focussed on rebooting the receiver and resetting 
	parameters, but to no avail. On day 239 it was noted that only three of 
	the four antennae were locking to four satellites (the minimum number of 
	satellites required to compute attitude, but only if locked-onto by all 
	four antennae), raising suspicions that the fault lay with the hardware, 
	specifically an antenna or cable connection. Sequential connection and 
	disconnection, from the receiver, of the four antennae cables confirmed 
	that no information was available from antenna 4. On day 240 the problem 
	was finally traced to a faulty amplifier (which serves to improve signal-
	to-noise ratio) on the cable to antenna 4 (situated starboard on the boat 
	deck). Salt deposits inside and outside the amplifier casing suggested 
	seawater ingress, and tests revealed that the 9V signal from the antenna 
	was being drawn off by the amplifier, reducing it to 5V. With no 
	replacement amplifier available on board, the amplifier was removed and 
	the cable re-terminated. After this renovation the Ashtech successfully 
	continued to compute attitude from 1803 on day 240, having failed, on this 
	occassion, for a total duration 3 days 6 hours 22 minutes.
Problem 4: During days 244 and 245, the Ashtech software hung on three separate 
	occasions, and it was necessary to switch on and off, and, on the second 
	occassion, to clear both the receiver internal memory and the data memory. 
	These problems were accompanied by overheating of the receiver unit, which 
	is in direct sunlight, persuading us to construct and fit a makeshift heat 
	shield. However, the problems also coincided with strong variations in the 
	Earth's electromagnetic fields (evidenced at night by the Aurora 
	Borealis), which possibly interfered sporadically with satellite signals.

Overall the instrument performed acceptably, although considerable effort was 
necessary to maintain attitude determination. Performance (on days when the 
Ashtech logged continuously) are quantified in Table 4.2.

Where we failed to obtain good Ashtech heading data for more than an hour or 
so (as throughout, or for part of, days 220-223, 226, 236-240, 245 and 246), 
the heading error, a-ghdg, was estimated from gyro heading. In order to make 
this estimation, we derived a quadratic relationship between a-ghdg and gyro 
heading, asymmetric about true north, using a scatterplot of a-ghdg against 
heading data (in the manner of King and Cooper, 1993). Working fits were 
determined twice during the cruise, the first fit being based on a-ghdg data 
collected along 41.5N (to estimate a-ghdg over days 220-223 and 226), the 
second fit being based on all data collected upto day 236 (to estimate a-ghdg 
over days 236-240, 245 and 246). The entire cruise dataset will be 
subsequently used to derive a comprehensive relationship between a-ghdg and 
heading, possibly accounting also for latitudinal variations of gyro error.

Bob Marsh

TABLE 4.1: Ship navigation error determined in port.

			Vigo		Porto	
			GPS	Glos	GPS	Glos
sd lat (m)		24.7	9.7	19.4	22.9
sd lon (m)		17.0	11.8	8.3	4.2
sd 2minydif (m)		25.2	5.3		
sd 2minxdif (m)		17.6	5.0		
yvelerror (cm s-1)	21.0	4.4		
xvelerror (cm s-1)	14.6	4.2		

TABLE 4.2: Summary of Ashtech performance statistics.

Julian Day	Number of bad 2-min.	Daily
Number		averaged headings	%GOOD
224		256			61.0
225		281			64.4
228		278			61.4
229		174			75.8
230		237			67.1
231		311			56.8
232		128			82.2
233		211			70.7
234		228			68.3
235		216			70.0
241		163			77.4
242		220			69.4
243		200			72.2
244		319			55.7
247		131			81.8
248		160			77.8
249		 69			90.4
250		259			64.0
251		444			38.3
252		188			73.9
253		214			70.3
254		173			76.0
255		134			81.4
256		166			76.9
257		245			66.0

5.	VM-ADCP MEASUREMENTS
a.	DESCRIPTION AND PROCESSING

The instrument used was an RDI 150 kHz unit, hull-mounted approximately 2 m to 
port of the keel of the ship and approximately 33m aft of the bow at the 
waterline. On this cruise the firmware version was 17.10 and the data 
acquisition software was 2.48. With the exception of a few interruptions (see 
Problems below), the instrument was operated continuously from day 219 (on 
leaving Vigo) to day 258 (after setting course for Southampton). For most of 
this time the ADCP was used in the water tracking mode, recording 2 minute 
averaged data in 64 x 8m bins from 8 m to 512 m water depth. On the 
continental shelves off Iberia, Greenland and Iceland (in water shallower than 
500m), the instrument was switched to a combined water and bottom tracking 
mode, maintaining 64 x 8m bins. While in bottom-tracking mode, a FH-command 
(setting the number of water-track pings between bottom-track pings) of 
FH00001 was entered in the "Direct Control" menu - ensuring one water-track 
ping per bottom-track ping. The ADCP was otherwise operated with a default 
configuration.

Daily processing:

Step 1:	Level 0 acquisition of ADCP water tracking and bottom tracking 
	velocities from level A, and conversion to level C PSTAR format.
Step 2:	Level 1 correction of the times of ADCP velocity profiles, taking 
	account of an approximate -1 second per hour PC clock drift.
Step 3:	Level 2 correction of the east and north components of ADCP 
	velocities, accounting for the gyro heading error (determined as the 
	difference between Ashtech and gyro headings).
Step 4:	Level 3 calibration of the shear profiles, taking account of errors 
	in signal amplitude and transducer alignment, using a working calibration 
	based on bottom tracking into/out of Porto (later confirmed as 
	sufficiently accurate by more extensive bottom-tracking off Greenland and 
	Iceland).
Step 5:	Level 4 merging of profiled velocities of water (relative to ship) 
	with ship velocity determined from GPS [2 versions, depending on whether 
	we had GPS-4000 or a GPS-Glonass mix]
Step 6:	Manual editting to remove spurious currents implied by sudden 
	changes in ship velocity (e.g. coming on/off station), or short gaps in 
	navigation data.

Occassional processing:

Editing of daily absolute velocity files to create on station and underway 
files, to compare with LADCP mesurements and CTD-derived geostrophic 
calculations respectively.

Daily plotting:

1	plotted contoured "percent good" (PCG) over 0-500m, to determine quality 
	of profiling (PCG > 25% is necessary to accept data for processing).
2	plotted 2-minute averaged currents, filtered with filter of width 10 
	minutes, in top 200m, to make first inspection of the raw absolute current 
	data, especially useful for identifying problems with underway (steaming) 
	data.
3	averaged data in bins 13-24, to determine 104-200m average current, 
	averaged this over 10 minutes, and applied top-hat filter of width 50 
	minutes, and plot against latitude and longitude (as did Saunders and 
	King, 1995), to identify features of the circulation.
4	where appropriate (e.g. across acoustic sections, wherever strong 
	features were observed), resolved the east and north components of raw 
	absolute current to along- and cross-track components, plotted contoured 
	cross-track profiles.

b.	CALIBRATING THE ADCP

The ADCP is routinely calibrated to take account of the orientation of the 
transducer on the hull (a misalignment angle - on RRSDiscovery the transducer 
orientation is intended to be fore-aft, pointing in the direction of 
steaming). Calibration exercises are undertaken to determine an amplitude 
factor A and the alignment angle error phi On this cruise we used heading-
corrected bottom tracking data to determine 2-3 hour averages of ship velocity 
(and hence speed over ground and heading), compared with GPS-derived ship 
velocity. The choice of 2-3 hour averaging periods is mindful of the noise in 
GPS-derived ship velocity. Details of when and where we switched from water 
tracking to bottom tracking are as follows:

1	steaming in/out of Porto (to change the LADCP) on day 225;
2	on the Greenland shelf between station 102 (at the coastward termination 
	of the second East Greenland Current section) and station 103 (commencing 
	the Denmark Straits section) on day 248;
3	on the Icelandic shelf, approaching station 111 (commencing the 20W 	
	section) on day 252.

The Greenland shelf bottom tracking was quality controlled and split into six 
approx. 2.5 h duration segments. The bottom tracking south of Iceland was 
likewise quality controlled and split into two approx. 3 h segments. Details 
of the quality control are as follows. Bottom tracking data were not used 
wherever:

(a)	depth exceeded 500 m;
(b)	GPS-derived ship heading changed by more than 10 between 2-minute 
	ensembles
(c)	GPS-derived ship speed changed by more than 10 cm s-1 between ensembles.

The results of the calibration exercises are shown in Table 5.1.

Differences between estimates of A and phi and sizeable standard deviations are 
possibly due to noise in the heading correction. However, note that A and phi 
have changed very little since Discovery cruise 223 (for which A = 1.0054 and 
phi = 3.57; see Leach and Pollard, 1998). We also used bottom tracking data to 
confirm that the Ashtech minus gyro heading correction was correctly 
determined.

c.	ADCP PERFORMANCE

The typical %good on/off station indicated depth penetration, along the 41.5N 
line, of 300 m and 200 m respectively. The ADCP suffered complete 
deterioration of depth penetration on day 236, steaming into heavy seas, and 
occasionally thereafter, notably in transit between the Cape Farewell acoustic 
section and the East Greenland Central Section. When sea conditions were 
favourable, depth penetration improved markedly with latitude, to over 500 m 
during the Cape Farewell acoustic section, implying better back-scatter at 
higher latitude.

Problems encountered:

1.	On three occasions the level A logging failed, and was restarted by RVS:
	(i) at 0800 on day 239 for 3 hours;
	(ii) at 0125 on day 245 for 1 hour 45 minutes (at the end of Cape 
	Farewell acoustic section);
	(iii) at 1150 on day 245 for 3 hours 45 minutes.
	On these occassions ADCP data was later retrieved from the appropriate 
	PINGDATA files, which are saved (one every 9 hours 16 minutes) on the PC.
2.	A hardware failure at around 1800 on day 254, indicated on the PC by 
	errors in all 4 acoustic beams and VERY WEAK TRANSMITTED SIGNAL error 
	message. This was fixed by Dave Jolly of RVS, by reseating the boards in 
	the VM chassis, and profiling resumed at around 1500 on day 255. On this 
	occassion ADCP data was irretrievably lost.
3.	On three occasions the PC was found to have hung and needed a reset:
	(i) at 2335 on day 239 for 25 minutes;
	(ii) at 1252 on day 255, for 4 hours;
	(iii) at 1048 on day 257, for 22 minutes.
	On these occasions ADCP data was irretrievably lost.

d.	GENERAL DESCRIPTION OF OBSERVED CURRENTS

After completion of test CTD station 1 on day 220, the ship steamed eastward 
at 5 kn over the ground along 41.5N, from 12.5W to 9W, in an acoustic 
survey of the eastern boundary. A northward coastal current of up to 30 cm s-1 
was observed between 9W and 10W. Apart from the northward coastal current, 
we measured generally weak, although highly variable, currents along the 
41.5N line. On turning to follow a northwest heading at 20W, currents 
strengthened, and underway profiling indicated a cyclonic feature, about 100 
km across, centred on 26W, 47N, with northward currents, followed by 
southward currents, of up to 40 cm s-1 (associated with temperature and 
salinity anomalies of -0.5C and -1.3 psu). We then encountered a 
southeastward flow of up to 60 cm s-1 between 28.5W, 49N and 29.5W, 50N, 
presumed to be a southern branch of the North Atlantic Current (NAC). The main 
branch of the NAC was observed as a northeastward flow of up to 70 cm s-1, 
between 30.9W, 51N and 31.5W, 51.5N. A northeastward flow of up to 25 cm 
s-1 was encountered between 32W, 52N and 33W, 53N, in the vicinity of the 
Charlie Gibbs Fracture Zone. We thereafter observed strong mesoscale 
variability in currents across the Irminger Sea, before reaching the East 
Greenland Current (EGC). The EGC exhibited southwestward flow of up to 60 cm 
s-1 between 41W, 58.25N and 43.5W, 59.75N, in the approach to Cape 
Farewell, and was very successfully resampled in a subsequent acoustic section 
back to 40.5W 58N. Weaker currents of up to 35 cm s-1 were observed on the 
following EGC transect, between 39W, 62.5N and 40.5W, 63N. Further strong 
southwestward flow was measured in transit between that transect and 
occupation of the Denmark Strait section. On commencement of the Denmark 
Strait section (30-31W, 65-65.5N), strong (> 80 cm s-1) northwestward 
currents were observed. Across the majority of the Strait we observed 
moderately strong (20 - 30 cm s-1) northward surface flow, with the exception 
of strong southward flow centred on 29W, 65N (also measured by LADCP). 
Unfortunately the ADCP hardware failure on days 254-255 coincided with the 
second transit across the NAC (observed on station 121 with the LADCP at 60N, 
20W). Near-surface currents of up to 30 cm s-1 were observed across the 
Rockall Trough, with northward and southward flows respectively on the west 
and east sides of the Anton Dohrn Seamount. Strong eastward currents (up to 70 
cm s-1) were observed at, and between, the final two CTD stations on the 
Hebridean shelf, possibly evidence for the coastal current.

ADCP current measurements along 4X were generally excellent, with very few 
gaps due to heavy seas, and no soft- or hardware related loss of data. Apart 
from problems with instrument reliability, good quality ADCP current 
measurements along the 20W/Ellett section were frequently interrputed by 
heavy seas, and the profiling along this section was generally less successful 
than along the 4X section.

Bob Marsh

REFERENCE

Leach, H. and R. T. Pollard, 1998: Discovery Cruise 230. Cruise Report, in 
	preparation.

TABLE 5.1: ADCP calibration exercise results. A is amplitude scaling factor, phi 
is heading correction in degrees to starboard.

Calibration exercise	A	sd	phi	sd
Porto port call				
incoming		1.0032		3.503	
outgoing		0.9998		3.418	
all data		1.0012		3.454	
Off Greenland				
segment 1		0.9959	0.0122	3.414	0.591
segment 2		1.0004	0.0078	3.393	0.568
segment 3		1.0002	0.0091	3.424	0.624
segment 4		1.0003	0.0065	3.400	0.275
segment 5		1.0008	0.0080	3.487	0.455
segment 6		1.0008	0.0080	3.372	0.548
all data (15h)		0.9997	0.0086	3.415	0.522
South of Iceland				
segment 1		1.0025	0.0095	3.333	0.548
segment 2		1.0018	0.0098	3.408	0.466
all data (6h)		1.0021	0.0097	3.370	0.509

6.	METEOROLOGICAL MEASUREMENTS
a.	SURFACE METEOROLOGY

AIMS

The aims of the surface meteorological measurements during cruise D230 
included:

i	Continuous measurement of mean meteorological variables such as air and 
	sea temperatures, wind speed and wind direction, downwards radiation (long 
	wave, short wave and photosyntheticaly active) and atmospheric pressure.
ii	Determination of the momentum transfer (wind stress) and heat fluxes 
	between the ocean and atmosphere.

All the instruments and logging systems functioned well throughout the cruise, 
and a high quality data set was obtained.

SENSORS DEPLOYED

(a) Mean Meteorology

The GrhoMet meteorological instrumentation system uses the RVS Rhopoint 
network for connection to foremast, hull and laboratory sensors. In addition 
to the normal RVS instrument suite, further JRD/OTD sensors were mounted on 
the foremast and connected into the logging system. A total of 18 variables 
were logged (Table 6.1). These measured air temperature, air pressure, wind 
speed, wind direction, downward long wave, short wave, and photosynthetically 
active radiation (PAR). The system acquired data at 5 second sampling rate and 
generated data files in raw and calibrated format which were written to the 
hard disk of a PC in the main lab. The GrhoMet system also output raw 
(uncalibrated) data via an RS232 link to the level B in SMP format, where the 
data was logged by the RVS computer system. The scientific clock was read 
through a serial port and used to update the PC clock once every 6 hours when 
a new data file was opened.

(b) Wind stress

A Gill Instruments Solent Sonic Anemometer (R2 Asymmetric Model, serial number 
38) was mounted on the starboard side of the foremast platform. The anemometer 
was operated in Mode 1 and the 21 Hz sampled data were logged using a PC 
system situated in the main lab. This recorded the raw data stream on optical 
disk and also calculated and recorded wind speed spectra and spectral levels. 
These were based on about 12 minutes sampling period (n=1024*15) starting each 
quarter hour.

SENSOR PERFORMANCE

(a) Air temperature and Humidity

Four sensors provided dry bulb air temperature data: two psychrometers, the 
RVS air temperature sensor, and the temperature signal from the RVS humidity 
sensor. The air temperature from the humidity sensor was low by almost 1 
degree compared to the data from the other three sensors. It was thought from 
previous cruise comparisons that the two psychrometers may over-estimate the 
dry bulb temperature by up to 0.15C when the downward solar radiation is in 
excess of a few hundred W/m2. However, examination of night-time data showed 
that the RVS air temperature sensor may read low by a similar amount for air 
temperatures of 15C or more. Accurate calibration of the RVS sensor is 
required before the true cause of any trends can be determined. When extremes 
of temperature or large downwards solar radiation were absent, the two 
psychrometers and the RVS sensor agreed well: for downwards longwave radiation 
of less than 100W/m2 and temperatures between 6 and 13C, the mean difference 
was 0.03  0.12C or better. The starboard psychrometer dry bulb readings also 
exhibited an intermittent cold bias, probably due to dripping from the wet 
bulb wick. This problem occurred mainly during the first two weeks of the 
cruise. The mean difference between the wet bulb temperature values from the 
two psychrometers was negligible ( -0.03  0.05C).

The humidity estimates from the two psychrometers were in very good agreement, 
with a mean differences of 0.0  1.0%.

The RVS humidity sensor compared well with the psychrometers: in this case the 
mean difference was 2.0  1.5%.

(b) Radiative fluxes

Examination of night-time data showed that the starboard solarimeter read high 
by about 5 W/m2. The port solarimeter showed a negligible bias. As observed on 
previous cruises, these instruments were sometimes shaded by the foremast 
extension and other instruments mounted nearby. Selecting the highest reading 
from the two instruments is recommended, but is not a complete solution since 
the two sensors were sometimes shaded simultaneously.

The port PAR sensor underestimated by 2.5 W/m2, and the starboard 
overestimated by 1.2 W/m2 (again, night time data only). Use of data from the 
starboard sensor is recommended since it exhibited less scatter.

The comparison between the two longwave sensors showed an underestimate from 
LW2 of 5 W/m2 for the higher values of downward longwave radiation, and 10 
W/m2 for the lower, clear sky values. From past instrument comparisons, LW1 is 
believed to be the more accurate sensor.

(c) Wind velocity and wind stress

Twelve minute averages of the mean relative wind speeds from the R.M. Young 
propeller-vane and the Solent Sonic anemometer were compared. For the entire 
data set, the mean difference was -0.1  0.7 m/s. However, after selecting 
data for periods when the wind was blowing within 30 degrees of the ship's bow 
(i.e. the anemometers were well exposed), the mean wind speed difference was -
0.3  0.5 m/s. The mean 10 minute average wind speed during the cruise was 
about 8m/s; the maximum 10 minute wind speed observed was about 21 m/s. The 
wind stress estimates obtained from the sonic anemometer corresponded to drag 
coefficient values similar to those found on previous cruises.

(d) Sea Surface temperature

The GrhoMet system logged sea surface temperature (sst) data from the hull 
contact sensor which is located in the forward hold at a depth of about 3.5 m. 
The data from the hull sensor were compared to those from the 
thermosalinograph (TSG) which sampled water from an intake located at a depth 
of about 5 m. The TSG sensor produced bad data when the ship was in Oporto 
(day 225.5 to 225.7) and again during day 221. The cause of the latter period 
of bad data is not known. Previous comparisons between the hull sensor and the 
TSG suggested that the hull sensor underestimated sst by 0.5C. Although this 
offset was incorporated in the calibration of the data from the hull sensor, 
the end of cruise comparison between the TSG and hull sensor data showed a 
residual offset which varied with temperature. For temperatures above 11C the 
hull sensor underestimated by 0.12  0.06C, and below 11C the hull sensor 
underestimated by 0.26  0.13C.

Margaret Yelland

b.	SBWR

MEASUREMENT DETAILS

The MK IV version of the Ship borne Wave Recorder (SBWR), developed through a 
collaborative programme between Ocean Technology Division of SOC and W. S. 
Ocean Systems Ltd., has been installed on Discovery since cruise 224. The 
electronic control and processing unit of the MK III system has been replaced 
by a PC running an application developed using LabWindows CVI. This converts 
pressure and accelerometer signals into a wave height value which is 
periodically processed to produce a wave energy spectrum. The logging system 
outputs summary data, such as significant wave height (Hs), to the RVS level 
B. However, this data has not been corrected for instrument response. The 
spectral data were periodically downloaded from the PC hard disk, and 
corrected for instrument response before recalculating Hs. Figure 6.1 shows 
that the uncorrected data underestimates Hs by around 40% on average.

Margaret Yelland

c.	ACOUSTIC RAIN BUOY

An acoustic rain gauge buoy was made available (by G. Quartly of JRD and K. 
Birch of OTD) for deployment trials during the cruise. Two attempts were made 
to deploy the buoy while the ship was hove-to, on station, during days 235 and 
239. These attempts were unsuccessful since the buoy only drifted a few tens 
of meters from the ship, rather than the required 500 m. In order for the buoy 
to stream away from the ship it was necessary for the deployment to take place 
while the ship was steaming at half or one knot. This method was tried 
successfully on days 246 and 249. Some practical problems were encountered 
during these deployments; the rope used was very thin (about 3 mm) which made 
recovery by hand a slow process; the hydrophone cable tended to kink and 
tangle (which could be prevented by use of a "fishing reel" arrangement); it 
was necessary for someone to be on deck to observe the behaviour of the buoy 
throughout the deployment.

Communication with the buoy is relatively straightforward but the supplied 
terminal software has to be used. Several attempts were made to adjust the 
data rates. It should be possible to set up the buoy to output data every 90 
seconds with 7 subsamples in that period. This was achieved on the bench but 
data rates reverted to 1 sample every 90 seconds after a 20 minute period. 
Either the buoy software is not the same as was thought or the manual did not 
provide clear enough instructions to do this. An external communications port 
is necessary to make any changes without having to open the buoy up every 
time. Further time on the bench is required to fully understand all of the 
available options, otherwise the instrument was relatively easy to use and 
communicate with.

Margaret Yelland and John Smithers

TABLE 6.1: Variables and sensors logged by the GrhoMet system. The variable 
names in the data files are shown [thus]. For each instrument (RVS) indicates 
that the sensor is part of the standard ship's system; (JRD/OTD) that the 
instrument was added for the cruise.

------------------------------------------------------------------------------
Variable		Position		Instrument		Note
------------------------------------------------------------------------------
Wet and Dry Bulb 	St'b'd side of 		Psychrometer IO2003 	(1)
[psyptd psyptw]		foremast platform	to day 229.7, IO1030	
			(forward sensor)	thereafter. (JRD/OTD)	
------------------------------------------------------------------------------
Wet and Dry Bulb 	St'b'd side of foremast Psychrometer IO2002 	
[psystd psystw]		platform (aft sensor)	(JRD/OTD)	
------------------------------------------------------------------------------
Humidity & air 		Port side of foremast 	Vaisala HMP 35D 	
temp. [hum humt]	platform		(RVS)	
------------------------------------------------------------------------------
Air temp [atemp]	St'b'd side of foremast Vector Inst. 209 	
			platform		(RVS)	
------------------------------------------------------------------------------
Longwave [lw1]		Top of foremast 	Eppley PIR 31170 	
			(port sensor)		(JRD/OTD)	
------------------------------------------------------------------------------
Longwave [lw2]		Top of foremast 	Eppley PIR 31171 	
			(starboard sensor)	(JRD/OTD)	
------------------------------------------------------------------------------
ShortWave [ptir]	Gimbal mounted on 	Kipp & Zonen CM6B 	
			port side of		962301 (RVS)	
			foremast platform		
------------------------------------------------------------------------------
ShortWave [stir]	Gimbal mounted stbd 	Kipp & Zonen CM6B 	
			side of foremast	962276 (RVS)	
			platform		
------------------------------------------------------------------------------
Photosynthetically 	Gimbal mounted on 	Didcot DRP-1 0151 	
active radiation	port side of		(RVS)	
[ppar]			foremast platform		
------------------------------------------------------------------------------
Photosynthetically 	Stbd side of 		Didcot DRP-1 5143 	
active radiation	foremast platform	(RVS)	
[spar]			(not gimballed)		
------------------------------------------------------------------------------
Wind Speed & 		Port side of 		RM Young AQ 11276 	
Direction [ws1 wd1]	foremast platform	(RVS)	
------------------------------------------------------------------------------
SST [sst1]		Hull mounted approx. 	PRT (RVS)	
			5 meters depth.		
------------------------------------------------------------------------------
Pressure [baro]		Lab			Vaisala DPA21 (RVS)	
------------------------------------------------------------------------------
Time			Lab			Ship's clock (RVS)	
------------------------------------------------------------------------------

Notes: (1) The fan on psychrometer began to fail on day 226, but the 
instrument could not be replaced until calm weather permitted on day 229.


Figure 6.1:	Comparison of Hs corrected (Hs corr) and Hs uncorrected (Hs raw)

7.	CHEMICAL MEASUREMENTS

Samples for salinity, oxygen and nutrients were drawn from all bottles on all 
stations. A summary of the sampling regime for all other quantities described 
below is given in table 7.1, and again in the WOCE format station summary 
table, reproduced here as Appendix 1.

a.	OXYGEN

Dissolved oxygen samples were drawn from each niskin bottle following the 
collection of samples for CFC analysis. Between one and four duplicate samples 
were taken on each cast, from the deepest bottles. The samples were drawn 
through short pieces of silicon tubing into clear, pre-calibrated, wide necked 
glass bottles and were fixed immediately on deck with manganese chloride and 
alkaline iodide dispensed using precise repeat Anachem bottle top dispensers. 
Thanks to Pete Mason for the construction of a reagent stand for use on deck. 
Samples were shaken on deck for approximately half a minute, and if any 
bubbles were detected in the samples at this point, a new sample was drawn. 
The samples were transferred to the constant temperature (CT) laboratory, and 
then shaken again thirty minutes after sampling and stored under water until 
analysis.

The temperature of the water in the Niskin bottles was measured using a hand 
held electronic thermometer probe. The temperature was used to calculate any 
temperature dependant changes in the sample bottle volumes.

Samples were analysed in the CT laboratory starting two hours after the 
collection of samples. The samples were acidified immediately prior to 
titration and stirred using a magnetic stir bar set at a constant spin. The 
Winkler whole bottle titration method with amperometric endpoint detection 
(Culberson, 1987) was used with equipment supplied by Metrohm. The spin on the 
stir bar was occasionally disturbed by the movement of the ship and also by 
the uneven bases on some of the glass bottles, leading to less effective 
stirring of the sample and thus longer titration times, although this probably 
did not effect the accuracy of the endpoint detection. The Anachem dispensers 
were washed out with deionised water, each time the reagents were topped up, 
to avoid any problems caused by the corrosive nature of the reagents.

The normality of the thiosulphate titrant was checked against an in house 
potassium iodate standard of 0.01 N at 20C at the beginning of each 
analytical run and incorporated into the calculations. A total of seven 
standards were used throughout the duration of the cruise. Blank measurements 
were also determined at the start of each run to account for the introduction 
of oxygen with the reagents and impurities in the manganese chloride, as 
described in the WOCE Manual of Operations and Methods (Culberson, 1991). 
Thiosulphate standardisation was carried out by adding the iodate after the 
other reagents and following on directly from the blank measurements in the 
same flask, as on the cruises D223 and D227. Changes in the thiosulphate 
normality are shown in figure 7.1. The thiosulphate normality precision was 
poor initially for the first reagent batch in use. The precision improved for 
the second batch, between stations 027 and 047, although the thiosulphate 
normality was low. From station 048 the thiosulphate normality results 
remained constant despite further changes in reagent batch. Tests were also 
carried out on each batch of alkaline iodide used during analysis, since some 
variability has occured on previous cruises when the iodide batch was changed.

Absolute duplicate differences for each station are shown in figure 7.2a for 
cruise D230, for a sample size of 499 pairs of duplicate measurements. 
Duplicate differences > 1.0 mol/l accounted for 24.25% of these duplicate 
pairs and ignoring these high duplicate differences the mean (SD) duplicate 
difference was 0.3899 ( 0.2566). The duplicate difference achieved was not 
related to the individual calibrated bottle (figure 7.2b) and high duplicate 
differences seemed to occur at random.

PROBLEMS

The diurnal temperature range of the CT laboratory often varied between 18 C 
and 20 C throughout the cruise. The temperature of the laboratory was noted 
for each analytical run.

On station 135 the Anachem dispenser used for the alkaline iodide broke, when 
the bottles fell over during rough weather. The dispenser was replaced and the 
new one used for the rest of the cruise.

REFERENCES

Culberson, C. H. and S. Huang, 1987: Automated amperoteric oxygen titration. 
	Deep-Sea Res. 34 875-880.
Culberson, C. H., 1991: WOCE Operations Manual (WHP Operations and Methods). 
	WHPO 91/1 Woods Hole. 15pp.

Elizabeth Rourke, Sarah K. Brown, Jian Xiong, Sue Holley

b.	NUTRIENTS

SAMPLING PROCEDURES

Samples for the analysis of dissolved inorganic nutrients: dissolved silicon 
(also referred to as silicate and reported as SiO3), nitrate and nitrite 
(referred to as nitrate or NO2+NO3) and phosphate (PO4), were collected after 
the CO2 samples had been taken. All samples were taken into 30 ml plastic 
"diluvial" sample cups which were washed 3 times with sample before filling. 
The samples were transferred immediately to a refrigerator where they were 
stored until analysis. Storage times on D230 varied between 4 hours and being 
analysed immediately after collection. A total of 141 casts were sampled for 
nutrients during the cruise. Samples were transferred into individual 8ml 
sample cups, mounted onto the sampler turntable and analysed in sequence. The 
nutrient analyses were performed using the SOC Chemlab AAII type Auto-Analyser 
coupled to a Digital-Analysis Microstream data capture and reduction system. 
Each sample was analysed in duplicate to ensure accuracy and increase 
precision.

CALIBRATION

The primary calibration standards for dissolved silicon, nitrate and phosphate 
were prepared from sodium hexaflurosilicate, potassium nitrate, and potassium 
dihydrogen phosphate, respectively. These salts were dried at 110C for 2 
hours, cooled and stored in a dessicator then accurately weighed to 4 decimal 
places prior to the cruise. The exact weight was recorded aiming for a nominal 
weight of 0.960 g, 0.510 g and 0.681 g for dissolved silicon, nitrate and 
phosphate, respectively. When diluted using MQ water, in calibrated 500 ml 
glass (or polyethylene for silicate) volumetric flasks these produced 10 
mmol/l standard stock solutions. These were stored in the refrigerator to 
reduce deterioration of the solutions. Only one standard stock solution was 
required for each nutrient for the duration of the cruise, checked daily 
against OSI standards as described later.

Mixed working standards were made up once per day in 100 ml calibrated 
polyethylene volumetric flasks in artificial seawater (@ 40g/l NaCl). The 
working standard concentrations, corrected for the weight of dried standard 
salt and calibrations of the 500ml and 100ml volumetric flasks are shown in 
Table 7.2.

A set of working standard solutions was run in duplicate on each analytical 
run to calibrate the analysis. From station 046 the top standard was also run 
in duplicate at the start of each analytical run as this was found to increase 
the linearity of the standardisation.

The nutrient calibration data (sensitivity, correlation coefficient, standard 
error and percentage drift) was recorded for each analytical run. There was an 
apparent increase in stability of the instrument the longer it was left 
switched on. This will be discussed further in a more detailed report (Holley, 
1998).

SILICON

Dissolved silicon analysis followed the standard AAII molybdate-ascorbic acid 
method with the addition of a 37C heating bath (Hydes, 1984). The colorimeter 
was fitted with a 50 mm flow cell (as the 15 mm cell detector caused problems 
when initially set up) and a 660 nm filter. The gain was adjusted to 2 for 
maximum response at 40 mol/l.

NITRATE

Nitrate (and nitrite) analysis followed the standard AAII method using 
sulphanilamide and naphtylethylenediamine-dihydrochloride with a copperised-
cadmium filled glass reduction column. A 15 mm flow cell and 540 nm filter was 
used with a gain setting of 3.5, adjusted for concentrations of up to 40 
mol/l. Nitrite standards equivalent in concentration to the second nitrate 
standard were prepared each day to test the efficiency of the column. The 
column was topped up only once prior to station 033.

On a previous cruise, D223, there were problems on the nitrate channel after 
the pump tubes had been replaced, with some fluid being sucked back up the 
waste tube through the flow cell. This occurred when the system was re-tubed 
on station 052 possibly due to an increase in pressure in the system. A fine 
dust of Cadmium in the reduction column had a similar effect, this was removed 
using a syringe filled with buffer. Whilst these problems did not directly 
affect the data they caused delays in the analysis. An alternative means of 
keeping the cadmium in the column will have to be found on future cruises.

PHOSPHATE

For phosphate analysis the standard AAII method was used (Hydes, 1984) which 
follows the method of Murphy and Riley (1962). A 50 mm flowcell and 880 nm 
filter were used and the gain set to 9.5 throughout the cruise, measuring 
concentrations of 0 -2 mol/l (the gain was inadvertently changed to 6.5 for 
stations 111-123 resulting in lower phosphate peaks). There was a large amount 
of noise on this channel despite a change of colorimeter prior to the cruise. 
This was thought to be due to the age of the photometer as it had become 
increasingly sensitive to changes in ambient light.

The phosphate channel is particularly sensitive to variations in salinity at 
the flow cell which results in a characteristic 'refractive index' peak shape. 
This was seen at the start of the cruise (stations 003 and 004), a clear 
distinct peak resulted which could be separated out by the software. 
Unfortunately the problem reoccurred from station 126 corresponding to a 
change in NaCl. Despite two more changes in NaCl batch the problem could not 
be resolved and this resulted in falsely high results. This problem will need 
to be addressed and may be resolved by an improvement in the software used. 
Accurate records of the weight and batch of NaCl used should minimise this 
problem on future cruises.

Reagents for each of the nutrients analysed were made up as and when required 
from pre-weighed salts. All measurements were made in the deck laboratory. The 
autoanalyser required periodic maintenance throughout the course of the 
cruise. The tubing on the peristaltic pump was fully replaced prior to 
stations 024, 052 and 115 with further periodic changes of individual tubes as 
necessary to maintain maximum sensitivity in the analysis. The autosampler 
unit randomly mis-sampled up to 3 samples per analytical run from stations 011 
until it was fixed (thanks again to Pete Mason) prior to station 037. Other 
than the problems described above the analyser performed well with regular 
cleaning and maintenance.

PRECISION - DUPLICATE AND QUALITY CONTROL MEASUREMENTS

All samples were analysed in duplicate. The mean absolute differences between 
the duplicate measurements and standard deviations (for the first 100 
stations) were: 0.106 (0.130) mol/l for dissolved silicon, 0.216 (0.212) 
mol/l for nitrate and 0.052 (0.075) mol/l for phosphate. This indicates a 
full scale precision of 0.27%, 0.72% and 2.6% respectively. Only duplicate 
measurements denoted with flag number 2 were used, therefore data that were 
reported as questionable at the time was not included in the above estimate.

Several quality control samples were also analysed on each run. Two quality 
control samples were made up from standard solutions supplied by OSI (prepared 
each day in plastic volumetric flasks using LNSW). New stocks were opened at 
station 050 and 107. The concentrations were adjusted to be equivalent to the 
3rd and 4th working standard concentrations (so the QC material is referred to 
as QC3 and QC4 respectively). In addition a deep water sample was collected 
from ca. 3500 m on station 001. The deep water QC samples were decanted into 
clean rinsed plastic diluvial containers and stored in the cold store until 
required, using 1 per analytical run. Each QC sample was analysed in duplicate 
on every run, variations in the results are shown in Figure 7.3. Where there 
was a marked increase or decrease for all three QC materials a correction 
factor could be calculated and applied to the samples. This was necessary on 
the following occasions as shown in Table 7.3. Causes for these variations 
will be examined in Holley, 1998.

REFERENCES

Holley, S. E., 1998: Report on the maintenance of precision and accuracy of 
	measurements of dissolved inorganic nutrients and dissolved oxygen over 43 
	days of measurements on Discovery Cruise 230 'FOUREX' (07 Aug - 19 Sep 
	1997). SOC Internal Document No. 30, 34 pp.
Hydes, D. J., 1984: A manual of methods for the continuous flow determination 
	of nutrients in seawater. IOSDL Report 177, 40pp.
Murphy, J. and J. P. Riley, 1954: A modified single solution method for the 
	determination of phosphate in natural waters. Anal. Chem. Acta, 27 31-66.

Sue Holley, Jian Xiong

c.	CARBON

The carbon system is defined by four variables: pH, alkalinity, partial 
pressure of carbon dioxide (pCO2) and total inorganic carbon (TIC). The 
knowledge of two of these variables allows to calculate the other two by means 
of a set of equations deduced from the thermodynamic equilibria. During the 
FOUREX cruise, pH was measured by potentiometric and spectrophotometric 
methods whilst alkalinity was measured by potentiotemetric titrations. pH was 
measured in every station by means of potentiometric or spectrophotometric 
methods, sometimes using both, so a comparison between both type of 
measurements will be made. Alkalinity samples were collected every third 
station, according to the sampling strategy.

pH MEASUREMENTS

i) Spectrophotometric method: sampling and analytical methods.

Seawater samples for pH were collected after CFC and oxygen samples from depth 
in the stations listed on table 7.1, using cylindrical optical glass 10 cm 
pathlength cells which were filled to overflowing and immediately stoppered. 
Seawater pH was measured using a double-wavelength spectrophotometric 
procedure (Byrne, 1987). The indicator was a 1 mM solution of Kodak m-cresol 
purple sodium salt (C21H17O5Na) prepared in deionized water with a 20% of 
ethanol content, the absorbance ratio of the concentrated indicator solutions 
(R = A578/A434) varied between 0.8 and 0.9. After sampling all the samples 
were stabilised at 25C, the temperature in the sample cell was monitored with 
a platinum resistance Pt-probe; all the absorbance measurements were obtained 
in the thermostatted (250.5C) cell compartment of a Beckman DU-730 
spectrophotometer. After blanking with the sampled seawater without dye, 100 
l of the dye solution were added to each sample using an adjustable repeater 
pipette calibrated before coming to the cruise. The absorbance was measured at 
three different fixed wavelengths (434, 578 and 730 nm), pH, on the total 
hydrogen ion concentration scale, is calculated using (7.1) (Clayton and 
Byrne, 1993):

(7.1)	pHt = 1245.69/T + 3.8275 + 2.11 x 10-3 (35 - S) + log{(R - 0.0069)/(2.222 
	- 0.133R)}

where R is the absorbance ratio (R= A578/A434), T is temperature in kelvin 
scale and S is salinity. As the injection of indicator perturbs the sample pH 
slightly, we corrected absorbance rations measured in the seawater samples to 
those values that would have been observed in the case of unperturbed 
analyses. This correction was quantified for each batch of dye solution, and 
it is calculated from a second addition of the dye to a series of samples over 
a range of seawater pH, the change in absorbance ratio per ml of added 
indicator (R) is described as a linear function of the value of the 
absorbance ratio (Rm) measured after the initial addition of indicator (i.e., 
R = A + B Rm).

ii) Potentiometric method: sampling and analytical procedure.

Seawater samples were collected for pH analysis after CFCs and oxygen at all 
depths in the stations listed on table 1 in 50 ml plastic bottles, samples 
were filled to overflowing and immediately stoppered. A Metrohm 654 pH meter 
with a Ross (Orion 8104) combination glass electrode was used to measure pH. 
pH measurements were standardised according to the following sequence:

1	calibration of the combined electrode with a pH 7.413 NBS buffer 
	solution;
2	checking of the electrode response with a pH 4.008 NBS buffer solution, 
	as described by Perez and Fraga (1987a);
3	adaptation of the electrode to the strong ionic strength of seawater by 
	means of a pH 4.4 seawater buffer containing 4.0846 g of C8H5KO4 and 
	1.52568 g of B4O7Na2.H2O in 1 kg of CO2-free seawater.

Temperature at the time of measurement was checked using a platinum resistance 
Pt-100 probe to correct the effect of temperature on pH (Perez and Fraga, 
1987a). All pH values were referred to a standard temperature of 15C (pH15).

iii) Potentiometric method: calibrations and corrections.

At each station, pH of seawater substandard (pHsss) was measured before and 
after each series of samples. The seawater substandard is a "quasy-steady" 
surface de-aerated seawater taken from the non-toxic supply and stored in the 
dark into a large container (25 liters) during 2 days before use. From each 
calibration we get the pHis (pH isoelectric), the pH recorded at zero 
potential. This pHis can vary because of real variations in the electrode, 
changes in the buffer and/or an error during the calibration. The pH15 values 
will be corrected using the anomalies of SSS and the variations of pHis at the 
different calibrations inn order to refer them to the same base line. 
Likewise, in order to check the procedure followed during the pH 
determinations, samples of CO2 reference material (CRM) were analyzed during 
the cruise.

ALKALINITY MEASUREMENTS.

i) Sampling and analytical procedure.

Seawater samples for alkalinity were collected after CFCs, oxygen and pH 
samples, in 500 ml glass or 300 ml plastic bottles. Full water column profiles 
were analyzed at the stations showed on table 7.1. Samples were stored at dark 
until analysis, which were carried in one day time after sampling. Alkalinity 
was measured using an automatic potentiomentric titrator "Titrino Metrohm", 
with a Metrohm combination glass electrode. Potentiometric titrations were 
carried out with hydrochloric acid (HCl exact molarity wil be established at 
laboratory) to a final pH of 4.44 (Perez and Fraga, 1987b). The electrodes 
were standardised using NBS buffers of pH 7.413 and the nerstian slope checked 
using a NBS buffer of 4.008. As for pH measurements, a pH 4.4 buffer, made up 
in sea water, was used to adapt the electrodes to the strong ionic strength of 
sea water. Concentrations are given in mmol/kg-sw.

ii) Corrections and calibrations.

Samples of seawater substandard (SSS) and CRM of batch 37 were analysed at the 
beginning and at the end of each batch of analysis. The variations of SSS and 
CRM alkalinity values along the cruise will be used to correct the electrode 
deviations along time so the alkalinity results will be referred to the same 
base line.

REFERENCES

Byrne R. H., 1987: Standardization of standard buffers by visible 
	spectrometry. Analytical Chemistry, 59 1479-1481.
Clayton, T. D. and R. H. Byrne, 1993: Spectrophotometric seawater pH 
	measurements: total hydrogen ion concentration scale concentration scale 
	calibration of m-cresol purple and at-sea results. Deep-Sea Res. 40 2115-
	2129.
Perez F. F. and F. Fraga, 1987a: The pH measurements in seawater on NBS scale. 
	Marine Chemistry, 21 315-327.
Perez F. F. and F. Fraga, 1987b: A precise and rapid analytical procedure for 
	alkalinity determination. Marine Chemistry, 21 315-327.

Marta Rodriguez and Iris Aristegui

d.	HALOCARBONS

The were two main aims to the halocarbon work on D230: The first was to 
collect a comprehensive CFC tracer data set to WOCE standards for CFC-11, CFC-
12, CFC-113 and carbon tetrachloride. Particular emphasis was placed on 
characterising the flow of Mediterranean Water and Antarctic Bottom Water in 
the Eastern North Atlantic, the flows through the Charlie Gibbs Fracture Zone 
and the Denmark Straits and the spread of Labrador Seawater across the entire 
North Atlantic. The second was to make measurements of as many halogenated 
compounds implicated in the ozone depletion and greenhouse gas debate as 
practically possible. The work forms part of a project to look at the natural 
oceanic sources of, for example, methyl bromide, methyl chloride, methyl 
iodide, methylene chloride and bromochloromethane together with the oceanic 
sink of the anthropogenic CFC replacements. Together with the phytoplankton 
speciation and pigment analysis described below, the work is a fundamental 
part of the SOC Sources and Sinks of Halogenated Environmental Substances - 
SASHES. programme. FOUREX is the second in a series of 4 cruises which enable 
cover of winter, summer and spring biological activity.

SAMPLE COLLECTION

Prior to the cruise the 10 litre Niskin bottles were checked for physical 
integrity and chemical cleanliness. Initial checks showed that none of the 
bottles were halocarbon contaminated and no contamination problems developed 
during the cruise. Samples were drawn first from the rosette, directly into 
100 ml ground glass syringes and stored under a continuous flushing stream of 
surface sea water to keep gas tight integrity. Most samples were analysed 
within 12 hours of collection. When a delay did develop due to frequency of 
CTD stations there was no evidence of sample degradation for up to a further 
12 hours.

ANALYSIS

Halocarbon analyses were carried out using a modified version of the GC-ECD 
system described in Boswell and Smythe-Wright (1996). The primary 
modifications were the use of liquid nitrogen and 10 cm x 19 gauge OD traps 
filled with glass beads for the cryogenic trapping of the compounds as this 
gave sharper chromatography, and the replacement of the six port switching 
valve V3 to a 10 port valve. This latter modification totally alleviated the 
pressure surge problem seen on previous cruises. A further improvement was the 
use of a dual gas drying arrangement comprising a Nafion dryer continuously 
flushed with a stream of nitrogen gas from a gas generation system, followed 
by a conventional drying tube containing potassium carbonate rather than 
magnesium perchlorate as a drying agent. On previous cruises there was some 
indication that the perchlorate had an adverse effect on CFC-113 measurent, 
however potassium carbonate on its own does not have the drying efficiency of 
perchlorate. With these modifications the system worked reliably giving high 
quality measurements throughout the cruise. Using a 38 minute chromatography 
run up to 18 compounds of interest were measured in the sea water samples. 
Measurements were made on a total of 119 stations, with approximately half to 
full depth, whilst the others were either to 200 m to measure biogenic gases 
or focused on bottom to mid waters to achieve the CFC tracer aims of the 
cruise.

Two minor problems occurred during the cruise. The first was the ratchet 
system on the gas selection valve became unreliable and needed attention. 
Second the liquid nitrogen supply ran out at station 98, due to poor quality 
gas tanks. The latter was solved by changing to -80C cryogenic trapping on 10 
cm x 1/16th traps filled with Unibeads and desorption at 140C using 
electrical heated metal blocks. Thanks go to RVS technicians for their help in 
fixing the ratchet system and making metal sheaths to facilitate faster 
heating.

A GC-MS system was also used for halocarbon measurement but not routinely 
since its sensitivity was found to be not as good as the GC-ECD system. 
Primarily it was used for halocarbon identification and to establish the 
existence, if any, of coeluting peaks. Some experimental and development work 
was carried out to increase sensitivity and this proved to be helpful for 
future work. However, since the GC-ECD system was functioning exceptionally 
well there was no need to replicate the samples on the GC-MS system.

CALIBRATION AND PRECISION

CFC tracers were calibrated using 20 point calibration from a gas standard 
prepared by the NOAA CMDL laboratory which had been cross calibrated to the 
SIO 1994 scale. Biogenic gases were calibrated using similar techniques but 
with gases supplied by a Kintek gas standards generator. Duplicate 
measurements were made at a number of stations and showed precision and 
accuracy of CFC tracers to be within the WOCE requirements: less than 1% or 
0.005 pmol kg-1 for CFC-11 and CFC-12 at low levels.

FINAL COMMENT

Although the chemistry laboratory on RRS Discovery provides a clean 
environment for halocarbon analysis it is not well ventilated. The lack of 
adequate cooling led to temperatures approaching the upper limit of the tracer 
equipment, particularly in the lower latitudes at the beginning of the cruise. 
The provision of adequate cooling needs to be addressed prior to any further 
cruises, particularly ones to more southerly latitudes.

In addition, it would be much appreciated if a 'dirty' electrical supply of at 
least 6 sockets was installed in the laboratory and that some clean outlets 
had an uninterruptable power supply. Much of the halocarbon equipment is 
ancillary: eg, compressors, pumps, coolers/heaters, which are liable to cause 
power surges and effect the extremely sensitive analytical systems. The latter 
is particularly important to GC-MS and GC-ECD systems where electrical failure 
can severely damage the equipment.

REFERENCE

Boswell, S. M. and D. Smythe-Wright, 1996: Dual-detector system for the 
	shipboard analysis of halocarbons in sea-water and air for oceanographic 
	tracer studies. Analyst 121 505-509.

Denise Smythe-Wright, Steve Boswell and Craig Harris

e.	PHYTOPLANKTON SPECIATION AND PIGMENT STUDIES

There is some evidence to support the idea that phytoplankton are natural 
producers of halocarbons which are either greenhouse gases or cause ozone 
depletion. The work carried out on this cruise forms part of the SASHES 
project, investigating the sources and sinks of halogenated environmental 
substances.

SAMPLE COLLECTION

Pigment analysis focused on the surface layer with the top 6 Niskin bottles 
(usually fired at 200, 100, 50, 25, 10 and 5 m water depth) being sampled at 
stations where halocarbon measurements were made. Samples were collected last 
from the rosette into 5 litre carboys which were rinsed with the sample prior 
to being filled. For HPLC analysis, water samples (0.5 - 2 l) were filtered 
through 25 mm Whatman GF/F filters using a specially developed positive 
pressure filtration unit - TOPPFUN. Duplicates were also taken. The filter 
papers were then immediately placed in cryovials and stored in liquid nitrogen 
for HPLC analysis at SOC.

For chlorophyll analysis, two 100 ml aliquots were filtered through 25 mm 
Whatman GF/F filters at low pressure. The papers were then placed in glass 
vials containing 10 ml of 90% acetone and immediately stored in the dark at -
20C for 24 hrs to extract the chlorophyll. Phytoplankton samples were taken 
for speciation studies at SOC at the surface and at depths corresponding to 
the chlorophyll maximum. Two 100 ml glass bottles, one containing Lugol's 
iodine and the other formalin, were filled at each depth.

In total 103 stations were sampled, with 440 phytoplankton samples collected 
and over 3000 litres of water filtered.

CHLOROPHYLL ANALYSIS

Following the extraction period samples were warmed to room temperature in a 
dark water bath before the fluorescence was measured using a Turner Designs 
Fluorometer. Four drops of 10% Hydrochloric acid were then added to the sample 
and the fluorescence remeasured in order to obtain phaeopigment data.

CALIBRATION AND RESULTS

Standard Chlorophyll solutions covering the expected concentration range of 
the samples were used for calibration. These were made up and measured along 
with blanks for each set of samples. Two primary standards were used to make 
up the calibration standards. The chlorophyll concentrations of these were 
calculated from the absorbance measured before and after acid addition at 665 
and 750 nm using a Camspec UV-visible spectrophotometer.

Chlorophyll and phaeopigment concentrations were calculated using the 
equations from the JGOFS protocols (1994). The concentration ranged from 0.002 
g l-1 to 2.045 g l-1 - the highest concentrations being found in the sub-
polar gyre, around the Greenland coast where there was evidence of a late 
autumn bloom. The chlorophyll maximum also shifted from around 50-100 m in the 
sub-tropical gyre to between the surface and 30 m in the sub-polar gyre.

INACCURACIES

The main areas identified as sources of inaccuracies were filtering leakages 
and the effect the motion of the ship had on the Turner fluorometer where the 
normal readable accuracy of three significant figures was reduced because the 
needle swung with the ship. This could possibly be overcome by turning the 
fluorometer 90 or by placing the instrument on a gimbal table.

Russell Davidson and Cristina Peckett

f.	SALINITY

SAMPLE ANALYSIS

Salt samples were drawn from each bottle for each cast, usually with one 
duplicate sample per station. Samples were analysed on the (ex-IOS) Guildline 
8400A salinometer, modified by the addition of an Ocean Scientific 
International peristaltic-type sample intake pump, in the Discovery's Constant 
Temperature Laboratory in the usual manner. One of the old IOS 8400 
salinometers was carried as a backup, but was not needed. The salinometer was 
standardised at the start of each crate of 24 samples. See section 2.b for 
CTD/sample salinity comparison statistics: achieved accuracy was within WOCE 
standards, ie, better than 0.001. There were five analysts: SB, MY, DJ, MF and 
VT. Salinometer operating temperature was 21C. The CT lab was run at a 
nominal temperature of 19C, but this needed to be watched, as the heating and 
cooling plant operation, improved since D223, still gets a little confused at 
near-ambient temperatures, resulting in actual temperatures more than 1C 
higher than nominal. No difficulties resulted. Four 'duff' ampoules of 
standard seawater (SSW) (salinity > 35) were found and discarded. These were 
all from earlier batches, from a total of about 150 ampoules consumed. This is 
in accord with previous experience: we usually find about 1 in 50 to be high 
salinity, presumed due to imperfect sealing of ampoule. 136 pairs of replicate 
samples were analysed, of which 3 pairs were >0.002 different. Excluding 
these, the mean difference between pairs was -0.0001, standard deviation of 
difference about mean 0.0006.

STANDARD SEAWATER SALINITY

Given the results of the CTD salinity analysis reported in 2.b above, and some 
suspicions generated during the cruise, we decided to look closely at the 
salinometer standardisation history. This was quite tractable given the use of 
one salinometer which appeared to retain good stability throughout the cruise 
(no adjustment to standard dial on salinometer, but this is normal practice), 
and no change to temperature regime (again, normal practice). Four batches of 
SSW were used during the cruise, ranging in production date from July 1995 
(oldest) to April 1997 (newest). They were used (coincidentally) in age 
sequence. Two of each batch were kept back and analysed as samples, 
standardised against the newest batch: see table 7.4 for batch information and 
measurement results. Now SSW is intended to be supplied accurate to 0.001; 
therefore the oldest batch, P128, is out of specification, being >0.002 
different from label salinity, where all the others are <0.001 different.

Further confirmation is provided by the standardisation history of the 
salinometer: see figure 7.4. When treating standards as samples, one must 
impose a standard or reference salinity. In fig. 7.4, we choose the mean 
measured salinity of the P132 batch, because there appears to be no 
significant instrumental drift throughout the use of the batch. The standard 
deviation about the mean of P132 salinity is <0.0004. This mean is then 
subtracted from salinities calculated for all standards. We then plot salinity 
difference, ie, standard salinity minus P132 mean salinity, versus standard 
number (in order of use throughout the cruise). The horizontal full lines show 
label salinity minus P132 mean salinity, and the horizontal broken lines show 
actual mean salinity minus P132 mean salinity. These lines are of course 
coincident for P132 which is standardised on its own mean salinity. Now this 
is not necessarily easy to interpret. All three older batches appear saltier 
than they ought to be; a consistent interpretation is that P132 might be 
0.0005 saltier than specified, so P132 is still in specification (<0.001 
different from label), but the other three are all brought closer to 
specification. This still leaves P128 >0.001 out of specification. Now there 
are no obvious trends, although there are small-amplitude oscillations about 
mean salinities, which would imply changes in the response of the salinometer 
itself, except for the first and earliest batch, P128. The trend, if real, 
implies a change due to salinometer sensitivity change equivalent to about 
0.0005 from start to finish of that batch, within a lot of noise. The safest 
interpretation of fig. 7.4 and table 7.4, combined with the analysis of 
section 2.b, is that batches P130, P131 and P132 are all OK (within 
specification), but that, through aging, P128 has become saltier, to which we 
ascribe a value of +0.0015. Therefore all samples analysed with this batch are 
0.0015 fresh, and so have been corrected by addition of 0.0015 to their 
salinity.

Sheldon Bacon

TABLE 7.1: Summary of chemical sampling regime during cruise. Column headings 
show sample type. CFCs: the number of samples drawn on each station generally 
alternated between full water column (ca. 23) and surface only (5/6) samples. 
C&P = chlorophyll a and phaeopigments; phy = phytoplankton; hpl = samples for 
HPLC analysis at SOC; pHp and pHs = pH by potentiometric and 
spectrophotometric methods, respectively; alk = alkalinity. SB = surface & 
bottom samples only. * = samples drawn, blank = no samples drawn. See text for 
clarification of regime.

Stn	CFC	C&P	Phy	HPL	pHp	pHs	Alk
1							
2					*	*	*
3	7		*	*	*	*	*
4						*	SB
5						*	*
6	18		*	*		*	*
7						*	*
8					*	*	SB
9	6	*	*	*	*		*
10	22	*	*	*			
11						*	*
12							
13	7	*	*	*		*	*
14	23	*	*	*			
15						*	*
16	7	*	*	*			
17	23	*	*	*		*	*
18							
19	11	*	*	*		*	*
20							
21	24	*	*	*		*	*
22							
23							
24	23	*	*	*	*	*	
25	5	*	*	*	*	*	
26	23	*	*	*		*	*
27	5	*	*	*	*	*	
28	23	*	*	*	*	*	
29	5	*	*	*		*	*
30	22	*	*	*	*	*	
31	6	*	*	*	*	*	
32	22	*	*	*	*		*
33	7	*	*	*	*	*	
34	13	*	*	*	*	*	
35	8	*	*	*		*	*
36	23	*	*	*		*	
37	7	*	*	*	*	*	
38	20	*	*	*		*	*
39	6	*	*	*	*	*	
40	18	*	*	*	*	*	
41	7	*	*	*		*	*
42	20	*	*	*	*	*	
43	6	*	*	*		*	
44	20	*	*	*		*	*
45	8	*	*	*	*	*	
46	21	*	*	*	*	*	
47	6	*	*	*		*	*
48	20	*	*	*	*	*	
49	7	*	*	*	*	*	
50	19	*	*	*	*		*
51	7	*	*	*	*	*	
52	17	*	*	*		*	
53	7	*	*	*			*
54	20	*	*	*	*	*	
55	3	*	*	*	*	*	
56	22	*	*	*		*	*
57	6	*	*	*	*	*	
58	23	*	*	*	*	*	
59	6	*	*	*		*	*
60	23	*	*	*	*	*	
61	6	*	*	*	*	*	
62	14					*	
63	23	*	*	*		*	*
64	6				*	*	
65	23	*	*	*		*	*
66	18				*	*	
67					*	*	
68	23	*	*	*		*	*
69					*		
70	20	*	*	*		*	
71	6	*	*	*	*		*
72	18	*	*	*	*		
73	8	*	*	*			
74	19	*	*	*	*		*
75	6	*	*	*		*	
76	20	*	*	*	*	*	
77	5	*	*	*		*	*
78	21	*	*	*	*	*	
79	6	*	*	*	*	*	
80	20	*	*	*		*	*
81	6	*	*	*	*	*	
82	23	*	*	*			
83	6	*	*	*		*	*
84	20	*	*	*			
85	4	*	*	*	*	*	
86	21	*	*	*	*		
87	2				*	*	*
88	17	*	*	*			
89	2				*	*	
90	13	*	*	*			
91					*	*	*
92	7	*	*	*			
93	5	*	*	*	*	*	*
94	22	*	*	*	*	*	*
95	5		*	*	*	*	
96	23	*	*	*	*	*	
97	6			*	*	*	*
98	17	*	*	*	*	*	
99	18	*	*	*	*		
100					*	*	*
101	11	*	*	*		*	
102	9	*	*	*	*	*	*
103	10	*	*	*	*	*	*
104	4				*	*	
105	18	*	*	*	*	*	
106	23	*	*	*	*	*	*
107	17	*	*	*	*	*	
108	4				*	*	
109	18	*	*	*	*	*	*
110	11				*	*	
111	6	*	*	*		*	*
112	11	*	*	*	*	*	
113	14	*	*	*	*	*	
114	16	*	*	*	*	*	*
115	22	*	*	*	*	*	
116	4				*	*	
117	19	*	*	*	*	*	*
118	19	*	*	*	*	*	
119	1					*	
120	13	*	*	*		*	
121	19	*	*	*		*	*
122	2				*	*	
123	4	*	*	*	*	*	
124	20	*	*	*	*	*	
125	13	*	*	*	*	*	*
126					*		
127	10	*	*	*	*	*	
128					*	*	
129	14	*	*	*	*	*	*
130					*	*	
131	10	*	*	*	*	*	
132					*	*	
133	5		*	*	*	*	*
134	10				*	*	
135	8				*	*	
136	21	*	*	*		*	
137					*	*	
138	20	*	*	*	*	*	*
139	10				*		
140	3				*	*	*
141					*	*	
142	7	*	*	*	*	*	
143					*	*	*

TABLE 7.2: Working nutrient standard concentration.

Standard	Silicate	Nitrate	(mol/l)	Phosphate
		(mol/l)	001-45	046-143		(mol/l)
S1		40.132		40.124	30.139		2.006
S2		30.145		30.139	20.034		1.507
S3		20.038		20.034	10.009		1.002
S4		10.011		10.009	 5.000		0.500

TABLE 7.3: Correction factors applied to the nutrient data.

		Stations	Factor
Silicate	046 - 049	0.933
		085 - 089	0.9502
		090 - 093	0.94997
Nitrate		057 - 059	0.8865
Phosphate	046		0.939

TABLE 7.4: Standard seawater salinities

Batch	Measured	Label		Production
	salinity	salinity	date
P128	34.9967		34.994		18-Jul-95
	34.9965		
P130	35.0000		34.999		21-Mar-96
	34.9994		
P131	34.9949		34.994		10-Dec-96
	34.9949		
P132	34.9972		34.997		09-Apr-97
	34.9976		
	34.9976		

Figure 7.1:	Variations in thiosulphate normality

Figure 7.2a:	Duplicate difference at each station

Figure 7.2b:	Comparison of duplicate difference with bottles used

Figure 7.3a:	Silicate QC Deep, QC 3, QC 4.

Figure 7.3b:	Nitrate QC Deep, QC 3, QC 4.

Figure 7.3c:	Phosphate QC Deep, QC 3, QC 4.

Figure 7.4:	Salinity standard history. Broken lines show measured mean over 
		each batch, full lines show mean assuming correct batch label 
		salinity and P132 measured mean correct (same as label).

8.	OTHER MEASUREMENTS
a.	THERMOSALINOGRAPH

Continuous underway measurements of surface salinity and temperature were made 
with a Falmouth Scientific Inc. (FSI) shipboard thermosalinograph (TSG). The 
instrument was run continuously throughout the cruise, with the exception of 
the unscheduled port call at Porto, when the sea water supply was interrupted. 
The TSG comprises two FSI sensor modules, an Ocean Conductivity Module (OCM) 
and an Ocean Temperature Module (OTM), both fitted within the same laboratory 
housing. Sea surface temperature is measured by a second OTM situated on the 
suction side of the non-toxic supply in the forward hold. The non-toxic intake 
is 5 m below the sea surface. Data from the OCM and the OTM modules are passed 
to a PC, which imitates the traditional Level A system, passing it to level B 
at 30 second intervals.

The temperature modules are installed pre-calibrated to a laboratory standard 
and laboratory calibration data are used to obtain four polynomial 
coefficients. A similar procedure is employed for the conductivity module. 
Salinity samples were drawn from the non-toxic supply at approximately four 
hourly intervals for calibration of computed TSG salinity. These samples were 
then analysed on a Guideline 8400A in the usual way. The four-hourly bottle 
salinities from the non-toxic supply are used as true salinity from which to 
calculate an offset to be applied to the TSG salinities. TSG salinity is 
usually calculated from the measured conductivity (cond) and temperature at 
the housing located in the hangar (temp_h). The temperature of the surface 
water is measured by the remote or marine sensor (temp_m).

TSG data was processed on a daily basis in the following steps:

Step 1:	Level 0 acquisition of raw TSG data (temp_h, temp_m, cond) from 
	level A, and conversion to level C PSTAR format (TSGEXEC0);
Step 2:	Level 1 despiking of raw TSG data, averaging to 2 minute 
	intervals, and merging with navigation data from the Bestnav file 
	(TSGEXEC1);
Step 3:	Bottle salinity data are prepared in Excel and saved as a tab-
	delimited text file, which is ftp'ed from a Mac, converting the data to 
	PSTAR format, and (Level 2) time is converted to seconds (TSG.EXEC, 
	TSGEXEC2);
Step 4:	Level 3 merging of bottle salinities and TSG salinities, to 
	determine residual errors in TSG salinity (TSGEXEC3A).

Daily plots of despiked, 2-minute averaged temp_h, temp_m and cond revealed 
the degree of noise in TSG conductivity, and provided near real-time 
information on the location of major fronts and currents. Early in the cruise, 
the conductivity measured by the TSG was noisy or obviously wrong for periods 
from a few minutes up to 24 hours. These data were subsequently made absent 
from final datasets using PEDITB and the gaps interpolated over by PINTRP. 
After 15 days, these errors vanished. In areas of very low salinity, i.e. near 
Greenland and in the East Greenland current, there was some doubt of the 
accuracy of the TSG. The final values for the mean offset of the bottle 
samples from the TSG data (-0.0099) and standard deviation (0.1271) were 
obtained by running PHISTO on the final residual file. TSGEXEC3A was used to 
make this residual file from the 2min averaged TSG data and the four hourly 
bottle samples. This exec calibrates according to conductivity thus 
eliminating the temperature dependence. This program was edited by Penny 
Holliday to include PMDIAN. This was to ensure that single points lying off 
the line of best fit did not affect the calculation of regression. Finally, 
the file containing the residuals was merged with navigation data. 
Calibrations etc will be reworked at SOC when time permits.

Maryke Fox, Bob Marsh and Penny Holliday

b.	PRECISION ECHO SOUNDER

The bathymetry equipment installed on RRS Discovery consists of: Hull mounted 
transducer, Precision Echosounding (PES) 'fish' transducer and Simrad EA500 
Hydrographic Echosounder. The Simrad Echosounder was used during the cruise 
for bottom detection. While in bottom detection mode, the depth values were 
passed via an RVS level A interface to the level C system for processing. The 
transducers were connected to the Simrad equipment via an external switch. A 
uniform sound velocity of 1500 m/s was used during the cruise. A visual 
display of the return echo was displayed on the Simrad VDU. Hardcopy output 
was produced on a colour inkjet printer. The amount of cable submerged whilst 
on station was measured to be approximately 9.6 meters. While steaming, the 
echosounder was 3 meters shallower than on station. So during steaming, the 
measured depth is 3 meters deeper than the real depth.

The PES fish transducer was used throughout the cruise, in preference to the 
hull transducer. This gave good return signals on station and adequate return 
signals whilst steaming at 10 knots. However, there was sometimes significant 
noise. Subsequent processing used Carter Tables corrections to sound speed to 
calculate corrected depth. It was interesting to compare actual depth on 
station with PES-recorded depth. This was done by converting maximum CTD 
pressure on station to depth, and adding the altimeter measurement of distance 
off bottom at closest approach. This depth estimate was then compared with 
corrected depth from the echo sounder; see table 8.1 for results. It is clear 
that the depth as recorded by the echo sounder is fairly accurate except over 
regions of steep bottom topography, occasionally on continental slopes but 
more so over the Mid-Atlantic Ridge, where depth estimates differ by >100 m. 
The average difference (echo-sounder minus CTD) for all 140 points is -10.6 m 
(sd 31.7). Excluding all points with absolute difference greater than 25 m, 
the mean difference is -0.3 m (sd 6.9, N=119). In steep topography, the 
difference is biased negative, ie, the echo sounder is picking up shallower 
side echos.

Virginie Thierry, Sheldon Bacon, Stuart Cunningham

TABLE 8.1: Comparison of actual depth with echo-sounder depth on station. Max 
prs is maximum pressure (dbar) measured by the CTD, max dep is max prs 
converted to depth (metres), alt is altimeter height off bottom at closest 
approach (metres), est dep is max dep plus alt (metres), sim dep is depth 
measured by echo sounder corrected for sound speed variation via Carter's 
Tables, and dif S-E is sim dep minus est dep (metres). -999 indicates missing 
data.

Stn	Max	Max	Alt	Est	Sim	Dif
Nbr	prs	dep		dep	dep	S-E
1	3613	3555	-999	-999	5178	-999
2	5267	5163	10	5173	5178	5
3	197	195	8	203	204	1
4	429	425	10	435	434	-1
5	857	848	5	853	794	-59
6	1561	1543	12	1555	1541	-14
7	2023	1997	12	2009	2006	-3
8	2255	2225	142	2367	2278	-89
9	3033	2988	11	2999	3004	5
10	3211	3162	8	3170	3176	6
11	3533	3477	9	3486	3496	10
12	3395	3342	10	3352	3348	-4
13	3079	3033	5	3038	3038	0
14	3135	3088	10	3098	3100	2
15	3183	3135	24	3159	3148	-11
16	2771	2731	11	2742	2738	-4
17	2985	2941	9	2950	2949	-1
18	3503	3447	7	3454	3444	-10
19	3791	3728	12	3740	3730	-10
20	4409	4330	10	4340	4342	2
21	5001	4905	9	4914	4914	0
22	2055	2029	-999	-999	3434	-999
23	5045	4947	11	4958	4961	3
24	5387	5279	12	5291	5294	3
25	5445	5335	9	5344	5346	2
26	5431	5321	23	5344	5348	4
27	5289	5184	10	5194	5190	-4
28	5151	5050	-999	-999	5348	-999
29	5463	5352	18	5370	5372	2
30	5583	5468	1	5469	5476	7
31	5613	5497	5	5502	5506	4
32	5521	5408	17	5425	5444	19
33	5503	5391	15	5406	5410	4
34	4781	4691	8	4699	4703	4
35	2563	2528	12	2540	2526	-14
36	4041	3972	11	3983	3989	6
37	3927	3860	11	3871	3856	-15
38	2713	2674	8	2682	2690	8
39	2753	2713	15	2728	2721	-7
40	2545	2509	15	2524	2511	-13
41	3933	3866	17	3883	3776	-107
42	4241	4165	12	4177	4155	-22
43	3213	3163	17	3180	3176	-4
44	3245	3194	13	3207	3218	11
45	3201	3151	22	3173	3162	-11
46	3139	3090	17	3107	3104	-3
47	3353	3299	17	3316	3312	-4
48	2987	2941	12	2953	2879	-74
49	2911	2867	13	2880	2870	-10
50	2973	2928	80	3008	2949	-59
51	2649	2610	11	2621	2624	3
52	2829	2786	11	2797	2767	-30
53	2583	2545	11	2556	2522	-34
54	2061	2033	8	2041	2078	37
55	3157	3107	109	3216	3021	-195
56	2503	2467	9	2476	2447	-29
57	2923	2878	12	2890	2815	-75
58	3291	3237	45	3282	3255	-27
59	3487	3429	8	3437	3443	6
60	2807	2764	7	2771	2772	1
61	3409	3352	61	3413	3372	-41
62	3031	2983	10	2993	2983	-10
63	4051	3978	29	4007	3995	-12
64	3173	3122	10	3132	3053	-79
65	4633	4543	9	4552	4554	2
66	3433	3375	10	3385	3358	-27
67	3143	3092	11	3103	3111	8
68	3015	2967	61	3028	2984	-44
69	2841	2797	31	2828	2815	-13
70	2035	2007	10	2017	2014	-3
71	2455	2419	6	2425	2296	-129
72	1925	1899	13	1912	1759	-153
73	1771	1747	16	1763	1650	-113
74	2485	2448	10	2458	2459	1
75	2607	2567	12	2579	2582	3
76	2839	2794	8	2802	2803	1
77	3089	3038	9	3047	2985	-62
78	3317	3261	9	3270	3275	5
79	3269	3214	11	3225	3226	1
80	3273	3218	11	3229	3232	3
81	3239	3184	10	3194	3199	5
82	3177	3124	9	3133	3140	7
83	3001	2952	10	2962	2967	5
84	2773	2729	7	2736	2745	9
85	2513	2475	10	2485	2486	1
86	2247	2214	6	2220	2222	2
87	2049	2020	10	2030	2030	0
88	1771	1747	9	1756	1751	-5
89	1375	1357	5	1362	1354	-8
90	935	924	10	934	917	-17
91	529	523	9	532	528	-4
92	193	191	9	200	198	-2
93	155	153	10	163	168	5
94	2929	2881	8	2889	2892	3
95	2755	2711	8	2719	2722	3
96	2571	2531	5	2536	2538	2
97	2377	2341	10	2351	2352	1
98	2015	1986	7	1993	1990	-3
99	1503	1483	13	1496	1494	-2
100	887	876	10	886	837	-49
101	553	547	4	551	527	-24
102	297	294	6	300	297	-3
103	377	373	4	377	381	4
104	571	564	12	576	574	-2
105	1087	1073	10	1083	1079	-4
106	1559	1538	7	1545	1548	3
107	1903	1876	8	1884	1886	2
108	1345	1327	12	1339	1334	-5
109	1009	996	5	1001	999	-2
110	497	491	9	500	501	1
111	203	201	11	212	214	2
112	591	584	13	597	595	-2
113	1199	1184	11	1195	1202	7
114	1509	1489	11	1500	1504	4
115	1825	1799	10	1809	1813	4
116	1799	1774	6	1780	1771	-9
117	2001	1972	13	1985	1989	4
118	2393	2357	10	2367	2373	6
119	2423	2386	11	2397	2403	6
120	2497	2459	9	2468	2472	4
121	2755	2711	8	2719	2722	3
122	2709	2666	10	2676	2679	3
123	2437	2400	6	2406	2409	3
124	1963	1935	10	1945	1942	-3
125	1557	1536	9	1545	1545	0
126	1005	993	9	1002	1003	1
127	847	837	11	848	846	-2
128	1159	1145	9	1154	1158	4
129	1221	1206	8	1214	1218	4
130	673	665	10	675	680	5
131	461	456	8	464	467	3
132	147	146	10	156	156	0
133	125	124	7	131	135	4
134	1037	1025	3	1028	1017	-11
135	1813	1788	12	1800	1807	7
136	2033	2004	11	2015	2017	2
137	587	581	8	589	588	-1
138	2241	2208	8	2216	2222	6
139	1955	1928	8	1936	1946	10
140	1409	1391	5	1396	1385	-11
141	295	292	14	306	304	-2
142	127	126	9	135	134	-1
143	129	128	8	136	134	-2

9.	COMPUTING

Six Macs and two PCs were available. One of the PCs was dedicated to 
supporting the operation of the LADCP. The other was used for word processing 
and spreadsheets. All the Mac's were used as terminals for the workstations, 
data processing on spreadsheets and word processing. A Sun SPARC ST1 
workstation was also available with a 4 GB disk attached to it. It was mainly 
used for data analysis and interactive editing of the ctd data. Shortage of 
memory on this workstation lead to repeated crashes. The reason was filling up 
of the memory by the screen output. When the non-scrolling option on the 
command shells was selected the problem was eliminated. Two printers an Apple 
Laserwriter II and a colour HP Paintjet were used for the production of CTD 
plots and text printing.

Data processing was based on version 4 of Pexec software; the only other data 
processing package available was MATLAB for which only one licence was 
available on board. Apart from a problem on program pdepth that seems to treat 
missing values as existing, the Pexec programs run reasonably well when the 
demanded formalities were observed.

Data backup was taking place daily (both in frequency and in duration). A tape 
drive that uses 150 MB cartridges stopped working as soon as the ship left 
Vigo. Thereafter the backup was done on Exabyte tapes, the drive of which was 
temperamental, and on optical laser disks. In view of the quantity of the data 
that needed backing up daily the failure of the tape drive was a rather 
fortunate event as both the Exabyte driver and the optical disks are clearly 
more efficient as far as space is concerned. Data archiving was taking place 
on optical disks according to the existing demand. One file was lost and 
recovered. Also two of the archived files had to be recovered. The time to 
actually reprocess the data from level-A would have been, at worse 2 h.

Despite the approximately 15 GB of disk space available this was proven to be 
insufficient at instances where reprocessing of whole sets of data was taking 
place during the later parts of the cruise. This problem was resolved by 
archiving parts of data or asking the users to compress or remove unessecary 
files.

At the end of the cruise two copies of the final form of the existing 
directories were created, which, together with a final backup on Exabyte tapes 
should provide adequate security against data loss.

In conclsion the computing facilities were generally more than adequate in all 
respects but two: a) it is thought unreasonable to provide 15 GB of disk space 
and not a more efficient system of backing it up, and b) availability of at 
least two more licences of matlab or an other data-processing package would 
have been beneficial.

Mickey Tsimplis

10.	TECHNICAL SUPPORT

This report covers the equipment that is the responsibility of the RVS 
Scientific Engineering Group (seg) and was used during this cruise. Being a 
predominantly CTD cruise, the winch systems and the starboard gantry were the 
only equipment handling systems used throughout the cruise. The only other 
(seg) systems used during the cruise were the non-toxic water system and the 
Millipore ultra pure water system.

The winch system operated successfully for the duration of the cruise. The 20 
tonne winch system was used with the deep tow conducting cable for the deep 
CTD stations, the deepest station being about 5500 metres. The CTD package was 
connected to the conducting cable via a TOBI type of conducting swivel. This 
combination of winch, cable, swivel and package proved to be very successful 
and should be borne in mind for future occasions where deep CTDs are required.

The 10 tonne winch system was used with the CTD cable for the shallower 
stations. The CTD cable was connected to the CTD package via a two tonne 
conducting swivel. Prior to its use the cable termination and the conducting 
swivel were subjected to a test load of two tonnes for a duration of five 
minutes. The use of the swivel proved to be successful and its use was 
probably the main contributing factor for eliminating the need to re-terminate 
the cable for the duration of the cruise.

 The starboard gantry was used successfully for the deployment of the CTD 
throughout the cruise. The geometry of the gantry together with its location 
on the ship made it possible to deploy the CTD package safely, even under 
severe weather conditions.

The non-toxic system operated reliably throughout the cruise, providing water 
for the permanent underway systems and for use by specialised equipment 
brought on board for this cruise.

The ultra clean water system was moved from the chemistry lab and installed in 
the after end of the deck lab. The system operated successfully throughout the 
cruise providing ultra pure water as required. During the cruise the RO and Q 
filter packs were changed as a routine measure.

Pete Mason, Richie Phipps and Simon Mitchell

APPENDIX: FOUREX STATION INFORMATION

We show here the standard WOCE format station summary table (WHP/WOCE, 1994). 
Column headings are as follows:

Ship/crs expocode: the cruise code is constructed from the country code 74 
		(U. K.), ship code DI (Discovery), number 230 (cruise number), and 
		extension 1 (leg number).
WOCE sect:	the WOCE section designation for this cruise is A24.
Stn Nbr, Cast Nbr: Station number and cast number.
Cast Type:	designation for cast type is ROS (for rosette plus CTD etc) 
		throughout.
Date:		date format is mmddyy throughout.
UTC Time:	time (UTC, GMT, Z) format is hhmmss throughout.
Event Code:	BE (beginning), BO (bottom), EN (end), referring to each cast.
Lat, Lon:	positions corresponding to each of the above.
Nav:		method of position determination for each of the above; GPS 
		(Trimble_4000 GPS), G24 (Ashtech GG24 GPS / GLONASS). See section 4 
		for details.
Unc Dep:	uncorrected depth (metres) from the echosounder (PES fish).
Ht Bot:		height off bottom (metres) at closest approach as measured by 
		altimeter.
Wire out:	metres of wire deployed at bottom of cast.
Max prs:	maximum CTD pressure recorded on cast.
Nbr btl:	number of rosette bottles sampled on each cast.
Parameters:	chemicals sampled during each cast: 1 (salinity), 2 (oxygen), 3 
		(silicate), 4 (nitrate), 5 (nitrite), 6 (phosphate), 7 (CFC-11), 8 
		(CFC-12), 24 (alkalinity), 26 (pH), 27 (CFC-113), 28 (carbon 
		tetrachloride), 34 (Chl a), 35 (phaeophytin), 36 (halocarbons except 
		CFCs).
Comments:	used for section start / end, CTD instrument identification, test 
		cast identification.

The accompanying figure (A1) shows bottle depths for the whole cruise plotted 
against station number.

Sheldon Bacon

REFERENCE

WHP/WOCE, 1994: WOCE Operations Manual, Volume 3: The Observational Programme; 
	Section 3.1: WOCE Hydrographic Programme; Part 3.1.2: Requirements for WHP 
	data reporting, eds. T. Joyce and C. Corry. WHP Office Report 90-1 
	Revision 2, WOCE Report 67/91, Woods Hole, MA, U. S., 144 pp.

Figure A1:	Bottle depths versus station number for Discovery cruise 230.