Preliminary Cruise Report

Nordic Seas Expedition

Knorr 166/11

[Chief Scientist]{.underline}: William M. Smethie, Jr.

Lamont-Doherty Earth Observatory

PO Box 1000

Palisades, New York 10964

Phone: 845-365-8566

Fax: 845-365-8176

e-mail: <bsmeth@ldeo.columbia.edu>

**[Ship]{.underline}:** R/V Knorr, Captain Carl Christensen

**[Ports of Call]{.underline}:** Reykjavik, Iceland

Glasgow, Scotland

**[Dates]{.underline}:** 30 May 2002 -- 1 July 2002

**[Cruise Track]{.underline}:** see Figure 1

**[Sampling and Measurements Overview:]{.underline}** A total of 159
CTD/Rosette stations were taken. Vertical profiles of temperature and
salinity were measured at each station using the CTD and vertical
profiles of current velocity were measured using a lowered ADCP.
Vertical profiles of water samples were collected at each station for
salinity, oxygen, nutrients, CFCs, Total CO2, alkalinity, and SF6.
Samples were also collected at a subset of these stations for tritium,
3He, 18O, 129I, noble gases, and 13C. Underway measurements were made
between stations for surface water pCO2 and pH and for current velocity
using the hull mounted ADCP.

**[Principle Investigators]{.underline}:**

+-----------------------+-----------------------+-----------------------+
| Investigator          | Parameter             | Affiliation           |
+-----------------------+-----------------------+-----------------------+
| Ala Aldahan           | I-129                 | University of Uppsala |
|                       |                       |                       |
|                       |                       | SWEDEN                |
+-----------------------+-----------------------+-----------------------+
| Richard Bellerby      | CO2                   | University of Bergen  |
|                       |                       |                       |
|                       |                       | NORWAY                |
+-----------------------+-----------------------+-----------------------+
| Steve Emerson         | Noble gases           | University of         |
|                       |                       | Washington USA        |
+-----------------------+-----------------------+-----------------------+
| Jean-Claude Gascard   | I-129                 | LOYDC                 |
|                       |                       |                       |
|                       |                       | FRANCE                |
+-----------------------+-----------------------+-----------------------+
| Marie-Jose Messias    | SF6                   | University of East    |
|                       |                       | Anglia                |
|                       |                       |                       |
|                       |                       | UNITED KINGDOM        |
+-----------------------+-----------------------+-----------------------+
| Paul Quay             | C-13                  | University of         |
|                       |                       | Washington            |
|                       |                       |                       |
|                       |                       | USA                   |
+-----------------------+-----------------------+-----------------------+
| Grant Raisbeck        | I-129                 | CSNSM-ORSAY           |
|                       |                       |                       |
|                       |                       | FRANCE                |
+-----------------------+-----------------------+-----------------------+
| Peter Schlosser       | Tritium, He-3, O-18   | LDEO                  |
|                       |                       |                       |
|                       |                       | USA                   |
+-----------------------+-----------------------+-----------------------+
| William M. Smethie,   | CFCs                  | LDEO                  |
| Jr.                   |                       |                       |
|                       |                       | USA                   |
+-----------------------+-----------------------+-----------------------+
| James H. Swift        | CTD-hydrography       | SIO                   |
|                       |                       |                       |
|                       |                       | USA                   |
+-----------------------+-----------------------+-----------------------+
| Dan Torres            | LADCP, ADCP           | WHOI                  |
|                       |                       |                       |
|                       |                       | USA                   |
+-----------------------+-----------------------+-----------------------+
| Francoise Yiou        | I-129                 | CSNSM-ORSAY           |
|                       |                       |                       |
|                       |                       | FRANCE                |
+-----------------------+-----------------------+-----------------------+

**[Cruise Participants]{.underline}:**

+-----------------------+-----------------------+-----------------------+
| Participant           | Duties                | Affiliation           |
+-----------------------+-----------------------+-----------------------+
| Vassile Alfimov       | I-129, Be-10, SF6     | University of Uppsala |
|                       |                       |                       |
|                       |                       | SWEDEN                |
+-----------------------+-----------------------+-----------------------+
| George C. Anderson    | Nutrients             | SIO                   |
|                       |                       |                       |
|                       |                       | USA                   |
+-----------------------+-----------------------+-----------------------+
| Frank B. Bahr         | LADCP, ADCP           | WHOI                  |
|                       |                       |                       |
|                       |                       | USA                   |
+-----------------------+-----------------------+-----------------------+
| Richard G.J. Bellerby | CO2                   | University of Bergen  |
|                       |                       |                       |
|                       |                       | NORWAY                |
+-----------------------+-----------------------+-----------------------+
| John K. Calderwood    | Oxygen                | SIO                   |
|                       |                       |                       |
|                       |                       | USA                   |
+-----------------------+-----------------------+-----------------------+
| Anthony Dachille      | Tritium, He-3, O-18   | LDEO                  |
|                       |                       |                       |
|                       |                       | USA                   |
+-----------------------+-----------------------+-----------------------+
| Sandra De Sequeiro    | SF6, I-129            | LOYDC                 |
|                       |                       |                       |
|                       |                       | FRANCE                |
+-----------------------+-----------------------+-----------------------+
| Ryan N. Ghan          | CFCs                  | LDEO                  |
|                       |                       |                       |
|                       |                       | USA                   |
+-----------------------+-----------------------+-----------------------+
| Eugene P. Gorman      | CFCs                  | LDEO                  |
|                       |                       |                       |
|                       |                       | USA                   |
+-----------------------+-----------------------+-----------------------+
| Irina Gorodetskaia    | CTD - hydrography     | LDEO and SIO          |
|                       |                       |                       |
|                       |                       | USA                   |
+-----------------------+-----------------------+-----------------------+
| Scott M. Hiller       | CTD/Rosette, ET       | SIO                   |
|                       |                       |                       |
|                       |                       | USA                   |
+-----------------------+-----------------------+-----------------------+
| Mary C. Johnson       | CTD data processing   | SIO                   |
|                       |                       |                       |
|                       |                       | USA                   |
+-----------------------+-----------------------+-----------------------+
| Guy G. Mathieu        | CFCs, noble gases,    | LDEO                  |
|                       | C-13                  |                       |
|                       |                       | USA                   |
+-----------------------+-----------------------+-----------------------+
| Carl W. Mattson       | CTD/Rosette, ET,      | SIO                   |
|                       | Technical group       |                       |
|                       | leader                | USA                   |
+-----------------------+-----------------------+-----------------------+
| Marie-Jose Messias    | SF6                   | University of East    |
|                       |                       | Anglia                |
|                       |                       |                       |
|                       |                       | UNITED KINGDOM        |
+-----------------------+-----------------------+-----------------------+
| Benoit Mignon         | CO2                   | University of Bergen  |
|                       |                       |                       |
|                       |                       | NORWAY                |
+-----------------------+-----------------------+-----------------------+
| David A. Muus         | Bottle data           | SIO                   |
|                       | processing,           |                       |
|                       |                       | USA                   |
|                       | Water sampling        |                       |
+-----------------------+-----------------------+-----------------------+
| Gisle Nondal          | CO2                   | University of Bergen  |
|                       |                       |                       |
|                       |                       | NORWAY                |
+-----------------------+-----------------------+-----------------------+
| Ronald G. Patrick     | Oxygen                | SIO                   |
|                       |                       |                       |
|                       |                       | USA                   |
+-----------------------+-----------------------+-----------------------+
| Erik W. Quiroz        | Nutrients             | SIO                   |
|                       |                       |                       |
|                       |                       | USA                   |
+-----------------------+-----------------------+-----------------------+
| Sarah C. Searson      | CFCs                  | LDEO                  |
|                       |                       |                       |
|                       |                       | USA                   |
+-----------------------+-----------------------+-----------------------+
| William M. Smethie,   | Chief Scientist       | LDEO                  |
| Jr.                   |                       |                       |
|                       |                       | USA                   |
+-----------------------+-----------------------+-----------------------+
| Helen B. Smith        | SF6                   | University of East    |
|                       |                       | Anglia                |
|                       |                       |                       |
|                       |                       | USA                   |
+-----------------------+-----------------------+-----------------------+
| James H. Swift        | Co-Chief Scientist    | SIO                   |
|                       |                       |                       |
|                       |                       | USA                   |
+-----------------------+-----------------------+-----------------------+

**[Cruise narrative]{.underline}:**

**[Preliminary CTD report (J. Swift, M. Johnson)]{.underline}:**

**[Preliminary LADCP and ADCP report (F. Bahr)]{.underline}:**

**[Preliminary oxygen report (J. Swift, R. Patrick)]{.underline}:**

**[Preliminary nutrient report (G. Anderson)]{.underline}:**

**[Preliminary CFC report (W. Smethie)]{.underline}:**

# Methods

Water samples were collected in 10-l Bullister style rosette bottles.
CFC samples, the first samples taken from the bottles, were drawn into
100-cc precision ground glass syringes and stored in a sink continuously
flushed with clean surface seawater until analysis. Samples were stored
for no longer than 8 hours. Air samples were collected by pumping air
from the bow directly to the CFC analysis system during periods when the
bow was into the wind.

The CFC samples were analyzed using an automated purge and trap system
interfaced to a gas chromatograph with an electron capture detector for
CFCs 11, 12, and 113. The column arrangement for the gas chromatograph
consisted of a yyy x 1/8 inch diameter precolumn of zzzz, a yyy x 1/8
inch diameter main column of zzzz and a yyy x 1/8 inch diameter post
column of molecular sieve 5A. The precolumn and main column were
operated at 95°C and the post column at ddd°C. The post column separated
N2O from CFC-12 and was valved out of the gas stream before CFC-11 and
CFC-113 eluted. The precolumn and main column provided good separation
between the CFCs methyl iodide. Chromatograms were acquired didgetly on
a PC and the CFC peak areas determined using HP Chemstation software.

Calibration curves were run at the beginning and end of the cruise and
every 3-4 days in between. A gas standard with known amounts of CFCs 11,
12 and 113 in nitrogen in seawater ratios was used for calibration. This
standard was prepared about one month prior to the cruise and since we
had no history on its stability, it was calibrated several times during
the course of the cruise against a standard kindly provided to us by
John Bullister of PMEL/NOAA. From our initial analysis of these results,
our standard appeared to be stable and a more careful analysis of these
results will be carried out after the cruise. The standards are on the
SIO 98 calibration scale.

Two CFC analysis systems were used which enabled greater than 90% of the
water samples collected to be analyzed. Duplicates were collected nearly
every station for comparison of the two systems and for determination of
the precision for each system. Preliminary calibration curves were fit
to the calibration data and preliminary CFC concentrations calculated
after the completion of each station. These preliminary data were merged
with the preliminary hydrographic data at sea and made available for
everyone on the cruise.

# Results

About 3000 water samples were analyzed for CFCs 11, 12 and 113 and air
samples (5 replicates per analysis) were measured daily. Both systems
worked very well with little down time. A high quality and rich data set
was obtained. Some of the prominent features in the data are given
below.

The highest CFC concentrations were observed in the cold surface and
near surface water of the Iceland Sea. This feature was connected
isopycnally to a subsurface maximum of CFC concentrations in the
southern Norwegian Sea. In the central Greenland Sea relatively high
concentrations were mixed down to about 1500 m indicating recent
convection to that depth. There was also a hint of slightly higher CFC
concentrations at the bottom relative to the low concentrations in the
bottom few hundred meters of the Greenland Sea. There was a distinct
difference in the CFC-11:CFC-12 ratio between ambient water in the
Nordic seas and recent inflow of near surface Atlantic water. The warm
Atlantic water had a lower ratio than the cold Nordic seas water.
Recently formed dense water from xxx Fjord in the Barents Sea was
observed as a high CFC feature along the continental slope off Svalbard.
The CFC concentration in Iceland-Scotland Overflow Water was relatively
low indicating its origin from a density horizon within the Norwegian
Sea that is not rapidlly ventilated.

# Acknowledgements

This work was supported by National Science Foundation grant OCE
01-xxxxx.

**[Preliminary CO2 report (R. Bellerby)]{.underline}:**

**1. Rationale**

The Nordic Seas play an important role in the transfer of carbon from
the surface ocean to the intermediate and deep waters of the North
Atlantic Ocean. The surface waters that enter the Nordic Seas from the
North Atlantic are fully loaded with their anthropogenic quota of carbon
and, generally, take up more 'natural' carbon from the atmosphere due to
cooling and biological productivity on the journey northwards.

Factors that control the surface CO~2~-system properties of the Nordic
Seas are poorly understood due to the scarcity of high quality data and
intermittency of multi-parameter expeditions. The North Atlantic
Oscillation has been shown to play an important role in determining the
flux of carbon between the atmosphere and ocean in this area (Olsen *et
al.* submitted) primarily by determining the wind-speed and route of
storm tracks (Nondal, 2002). The transport fate of this carbon depends
on many factors including: the surface propagation route across the
Nordic Seas; the extent and timing of biological activity; and the deep
and intermediate water formation rates in, primarily, the Greenland Sea.

The Nordic Seas have shown considerable change since the 1980s
reflecting increases in the flow of deep water from the Arctic and a
reduction in the influx of surface North Atlantic waters. This is
generally assumed to be linked to a reduction in the deep-water
convection in the Greenland Sea, although the cause is still a matter of
speculation, reducing the southward meridional transport of carbon into
the subsurface waters of the North Atlantic and also altering the
biogeochemical characteristics of the waters entering the Barents Sea
and the Arctic Ocean.

Finally, the increase in atmospheric carbon concentrations is reflected,
to some extent, in the surface pH of the oceans. Predicted surface pH
decreases will have a deleterious effect on the physiology of some,
particularly calcareous, marine organisms and may alter the efficiency
of the biological pump due to changing the plankton community structure
and it's carbon utilisation efficiency.

The aim of the CO~2~ system study is thus multi-faceted:

1.  To gather surface *p*CO~2~ and pH~T~ data to model the mechanistic
    controls on the surface CO~2~ system. The pH measurements will be
    the first extensive survey of the study area and will provide a
    benchmark from which future pH decreases may be determined.

2.  To determine basin-wide, full profile characteristics of the CO~2~
    system, through TCO~2~ and total alkalinity measurements and the
    determination of meridional and zonal carbon transfer rates. These
    will be compared to previous studies onward from the TTO-NAS and
    through the ESOP, IMCORP and NORCLIM campaigns.

3.  The long term monitoring of the CO~2~ system in waters associated
    with the deliberately released tracer SF~6~ (see section on SF~6~
    measurements) will be continued and used to determine the movement
    and rate of carbon transport in the tagged patch. In association
    with other biogeochemical measurements within the tagged water, the
    regeneration rate of biologically derived nutrients, including
    carbon, will be possible if there is sufficient variation with the
    surrounding waters to enable mixing rates to be determined.

**2. Methods and preliminary results**

## 2.1. Total inorganic carbon

Discrete measurements of total inorganic carbon (TCO~2~) were made from
water samples from Niskin bottles on the CTD rosette. The SOMMA (Single
Operator Multiparameter Metabolic Analyzer) system was used (Johnson *et
al.* (1993)) where acidification of a known volume of seawater releases
the TCO~2~ as CO~2~ gas which is bubbled through an organic solution to
form a titratable acid. The titration is performed against a colour
indicator by electrolytically generated hydroxyl ions and the total
current required gives a direct value of the amount of carbon titrated.
All samples were measured within 24 hours of collection. The precision
of the instrument during the test station was 1.3 mol.kg^-1^ (*n = 20*)
based on multiple measurements on samples from same-depth rosettes. The
accuracy of the method is assured against certified reference materials
(CRMs) from Prof. Andrew Dickson's laboratory at SIO. CRM Batch 56 was
used for both TCO~2~ and total alkalinity calibration. In total xxxx
samples were measured for TCO~2~. Specimen depth profiles are shown in
Figure 1 for stations 5,6 and 10 in the Iceland Sea.

1.  *Total alkalinity*

Total alkalinity was measured in the remaining sample after the TCO~2~
measurement. A known amount of sample was titrated, potentiometrically,
against 0.05M HCl in 0.6M NaCl using GRAN titration with sample
temperature measured during each electrode potential reading. Analyses
at the same-depth CTD test station resulted in a poor precision due to
insufficient 'warming-up' of the system. However, the final Niskin
showed a precision of ± 1.7 mol.l^-1^ (*n=6*) and replicate analysis of
CRMs show that this precision was obtained, or exceeded throughout the
majority of the cruise. Due to a leak in the acid burette water jacket,
it was not possible to thermally regulate the acid prior to addition.
Therefore, it is possible that there may be some inaccuracy incurred due
to room temperature variations between sample and CRM measurements.
Following an unprecedented number of sample measurements it was
necessary to make up new acid with table salt as the NaCl base (due the
unavailability of NaCl on the ship). The salt was re-crystallised to
increase purity prior to use. Due to the crossing of cruise tracks, it
was possible to compare the analysis of similar surface waters measured
with the two acids and the obtained alkalinities agreed to 1 mol.l^-1^.
There was an offset between the two acid batches used and this has been
partially ascribed to the salt containing traces of carbonate. The acid
will be thoroughly analysed back in the laboratory. In total xxxx
samples were measured for total alkalinity. Specimen depth profiles are
shown in Figure 1 for stations 5,6 and 10 in the Iceland Sea.

2.  *Partial pressure of carbon dioxide*

The partial pressure of CO~2~ (*p*CO~2~) was measured using an
adaptation of the traditional moored role of the Submersible Autonomous
Moored Instrument for CO~2~ (SAMI-CO~2~) (DeGrandpre *et al.*, 1993;
DeGrandpre and Bellerby, 1995). Seawater *p*CO2 was measured on
seawater, in a specially designed hat, from the shipboard seawater
supply following equilibration of CO~2~ gas, across a *Figure 1. Depth
profiles of TCO~2~ and total alkalinity for stations 5, 6 and 10 in the
Iceland Sea. The data is preliminary but shows that, contrary to earlier
studies of the Nordic Seas, the deep water CO~2~ system is not
monotonous but shows distinct features that are common between stations.
The profile detail and inter-profile congruency also suggest that the
precision of the instrumentation declared in the text (and shown as the
error bar in each diagram box) may have been underestimated.*

![](media/image1.pct){width="6.375in" height="3.8854166666666665in"}

silicone membrane, with a solution of bromothymol blue. The resultant pH
of the solution was determined photometrically and *p*CO~2~ calculated
from a predetermined *p*CO~2~/pH dependency of the solution and the
measurement temperature. *p*CO~2~ measurements are reported every 30
minutes. The data is logged on an internal computer and the indicator
solution will be recalibrated back in the laboratory.

*2.4. Spectrophotometric pH~T~*

Seawater pH~T~ was measured on-line from the ship's underway laboratory
seawater supply via a constant header tank. The multi-wavelength
spectrophotometric method of Bellerby *et al*. (2002) was employed where
the change in absorption of a seawater sample is measured after the
addition of the pH-sensitive sulfonephthalein indicator thymol blue. The
method has a measurement frequency of 20 samples per hour and a
precision of 0.0007 pH units. pH is reported on the total hydrogen ion
scale with an estimated accuracy of 0.003 units.

Problems with light levels meant that seawater pH was not measured
through the Iceland Sea. However, surface pH~T~ was measured for the
duration of the cruise resulting a dataset consisting of an estimated
15000 data points. Significant post cruise analysis is required, such as
recalculation of pH~T~ using *in situ* salinity and temperature, so no
data is ready for reporting at present.

### 

### Acknowledgements

We would like to acknowledge the excellent support from the Captain and
crew of the *RV Knorr*. The outstanding input from the SSSG,
particularly at the onset of the study, made the instrument setup go
smoothly. We were encouraged by the stimulating scientific discussions
with the Chief Scientist Bill Smethie, Jim Swift and the rest of the
science team. The contribution of George Anderson to the well being of
the TCO~2~ and total alkalinity instrumentation (and for the insight
into the use of a NaCl substitution) can never be overstated. This
research was funded by Grants \# xxxx and XXXX; blah blah

#### References

Bellerby R.G.J., Olsen A., Johannessen T. and Croot P., 2002. The
Automated Marine pH Sensor (AMpS): a high precision continuous
spectrophotometric method for seawater pH measurement. *Talanta.*

Degrandpre M.D., Hammar T.R., Smith S.P. and Sayles F.L., 1995. *In
situ* measurements of seawater *p*CO2. *Limnology and Oceanography*, 40,
969-975.

DeGrandpre M.D. and Bellerby R.G.J., 1995. Chemical Sensors in Marine
Science. *Oceanus*, 38(1), 30-32

Johnson K.M., Willis K.D., Butler D.B., Johnson W.K. and Wong C.S.,
1993. Coulometric total carbon dioxide analysis for marine studies:
maximizing the performance of an automated gas extraction system and
coulometric detector. *Marine Chemistry,* 44, 167-187.

Nondal G., 2002. Great Sea Journeys -- a survival guide. *Oddas Tidene*,
July 2002, p6.

Olsen A., Bellerby R.G.J., Johannessen T., Omar A. And Skjelvan I.,
2002. Interannual variability in the wintertime flux air-sea flux of
carbon dioxide in the North Atlantic 1981-2001, and the relation with
the North Atlantic Oscillation. *Deep-Sea Research I*, in revision.

**[Preliminary SF6 report (M.J. Messias)]{.underline}:**

# Introduction and objectives

The Greenland Sea (GS) is believed to be one of the most important
regions to ventilate the world oceans, and convective processes there is
regarded to be an important contributor to drive the general
thermohaline circulation of the oceans. For this reason, in August 1996,
a tracer release experiment was launched in the intermediate-depth
waters (GAIW) of the central Greenland Sea, to study convection,
vertical mixing, lateral dispersion, and exchange with the surrounding
seas and current systems. The tracer, 320 kg of sulfur hexafluoride, was
injected on the 28.049 potential density surface (300m) in the center of
the Greenland Sea Gyre at 75 N and approximately 3 W. Since then, the
evolving tracer distribution has been documented in time and space from
the Greenland Sea to the surrounding oceans by a survey at least once a
year (1996-1998: EU project ESOP2, 1999-2000: UK NERC project ARCICE,
2001-2003: EU project TRACTOR).

Sulphur hexafluoride (SF6) is an excellent tracer (non-toxic,
conservative and inert anthropogenic compound) of large-scale
experiments because it has an exceptional low limit detection in sea
water at \~0.01 fmol/l (1fmol=10^-15^ mol) and the release of only few
hundreds of kilograms in the open ocean can last up to several years and
cover hundreds of kilometres.

The experiment, specifically designed to enable study of regional as
well as large-scale circulation, focuses on water mass transformations
associated with dense water production and contributing to the Northern
component of the global thermohaline circulation. The objective of the
SF6 survey conducted from R/V KNORR was to document the lateral and
vertical extent of the patch over the Nordic Seas and the
Iceland-Shetland outflow 6 years after release, to determine the
important processes/routes allowing tagged Greenland Intermediate Waters
to spread through the Nordic Seas into the North Atlantic Ocean, and to
measure the amount of tracer that had reached the Boreas Basin and the
Fram Strait to the north, the Icelandic Sea to the southwest and the
Norwegian Sea /Iceland-Scotland system to the southeast. The Knorr
cruise was carried on in conjunction with the icebreaker Oden cruise
that was in charge of the survey of the East Greenland Current system
from Fram Strait to south of the Denmark Strait and complete the
coverage of the April-June 2002 Nordic Seas survey.

Work at Sea

SF6 was sampled at 153 of the 159 stations occupied during the cruise,
from most of the rosette bottles tripped at these stations. Sampling
depths were chosen to obtain 100-meter spacing in the tracer patch. The
water samples for SF6 were sampled into 500-ml glass bottles (BOD) in
third position after CFCs, helium and oxygen. Samples were run, usually
within 3-6 hours of being taken, by electron-capture gas chromatography.
If not run immediately, the samples were stored at low temperature in
cool boxes on deck. The number of rosette samples successfully analyzed
for SF6 during the 30-day cruise was 2554. Preliminary concentration
data were calculated using a set of 4 secondary gas standards (10.6 ppt,
15 ppt, 33 ppt, 51 ppt) and plotted during the cruise as individual
profiles. Back at UEA, these standards will be calibrated against a
primary standard provided to UEA by NOAA in May 2002 and subsequently a
corrected SF6 data set will be calculated.

Preliminary Results

SF6 from the tracer patch was found at every station reaching potential
density anomalies greater than 28.025 kg/m\^3. The scatter plots of all
the SF6 data for the all cruise versus σ~θ~ (range 27.5 to 28.01) is
presented Figure 1. The vertical distribution of the main tracer patch
still appears symmetrical around relatively sharp peaks with maximum
concentrations found between potential density anomalies of 28.03 and
28.058 kg/m\^3. Six year after the release, the higher concentration of
the tracer still resides in the Greenland Sea basin but a large part of
it appeared to be now in transit to/within the other ocean basins
(Boreas basin, Icelandic Sea, Norwegian Sea, Arctic Ocean and North
Atlantic). Figure 2 gives an illustration of the SF6 profiles measured
in the basins surveyed during section 1 from Iceland to Spitzbergen and
across the East Greenland Current at 70N. Station 40, located in an area
of the GS not affected by winter convection, presents peak concentration
greater than 4.5 fM (1 fM = 10\^-15 moles/L). High tracer concentrations
around 4 fM were also found, however, over the Boreas basin (ST29) and
at ST33 into the West Spitzbergen Current at the Fram Strait, indicating
a major direct route for the intermediates waters from the GS (and the
Boreas Basin) to the Arctic. To the southwest, concentrations appeared
lower, falling to 2.5 fM in the Icelandic Sea (ST7) and the ECG at 70N
(ST93/94/95). High concentrations greater than 3 fM were found again
along the Jan Mayen Ridge (ST87 at 70N and then ST 103 at 66N) spreading
into the Norwegian Sea and southeast towards the overflows in the
Iceland-Faroe-Shetland ridges. Inside the Faroes-Schetland Channel
tracer had clearly penetrated into the western side of the channel (ST
154, figure 3).

Figure 4 presents the SF6 profiles in the GS Abyssal Plain itself. At
the level of the injection, the tracer patch appears to be redistributed
over the water column from 300 to 1500 dbars as the result of winter
convection. The enrichment of SF6 at the bottom of the Greenland Sea was
first observed 1 year after the release with concentration 0.8 fmol/l.
It was likely due to SF6 that was misinjected during the release and
fell to the bottom before dissolving. Six years later this tracer is
still measureable with concentrations at the bottom of approximately 0.3
fM (toward the background level below 0.1 fM).

The lateral distribution will be used to provide important information
on the contribution, the pathways and their rate of speed of the tagged
GS water spreading towards the Nordic Seas and its outflows. The
distribution of the tracer across density surfaces has been well
resolved. It will be used to estimate rates of diapycnal dispersion due
to convection and to shear-induced turbulence. 6 year after the release,
the rate of spread will enable to test if it has been accelerated by
boundary mixing as the tracer entered regions with topographic features.
The distribution of the tracer patch at the bottom of the GS when
compared to measurements from previous years, should provide estimates
of the diapycnal diffusivity in the GS bottom boundary layer. The
SF6/CFCs data association may be of special interest in investigating
the renewal (diffusion/downslope motion in the bottom boundary layer) of
bottom and deep waters of the GS.

Acknowledgements

Cruise coordinators and chief scientists were Bill Smethie and Jim
Swift. Many thanks are due to the captain and crew of the Knorr and in
particular to the electrician engineer for his productive assistance.
Thanks are also due to Vassili Alfimov for his help in sampling and
cooperation. The present work is funded by the European Project Tractor
(Tracer and Circulation in the Nordics Seas region, European commission
under the fifth framework programme, contract number EVK2-2000-00080).

![](media/image2.png){width="5.924305555555556in"
height="4.438888888888889in"}

Figure 1: Scatter plot of SF~6~ versus potential density

![](media/image3.pct){width="3.9569444444444444in"
height="2.970138888888889in"}

Figure 2: SF6 versus pressure in the Iceland Sea (ST7), north of Jan
Mayen (St15), in the Boreas basin (ST29), in the Fram Strait (ST33), in
the GS basin (ST40) and in ECG at 70N (ST94).

![](media/image4.pct){width="3.9569444444444444in"
height="2.970138888888889in"}

Figure 3: SF6 versus Pr at the Faroe-Shetland chanel: The profile
(ST154) in the western part of the channel clearly shows the SF6 signal
from the release at 850 dbars depth in opposite to the profile (ST155)
in the eastern part of the channel.

![](media/image5.pct){width="3.9569444444444444in"
height="3.0104166666666665in"}

Figure 4: SF6 versus pressure in the Greenland abyssal plain: the tracer
peak appears to be redistributed over the water column from 300 to 1500
dbars as the result of winter convection.

**[Preliminary I-129 report]{.underline}:**

**I-129 and Be-10 samples collected by the University of Uppsala (V.
Alfimov)**

The project will aim to establish data series for the radioactive
isotopes ^129^I and ^10^Be in ocean water and sediments of the Nordic
Seas (Iceland, Norwegian and Greenland Seas), which can serve as:

1)  basic information (temporal and spatial) about pattern and sources
    of water mass exchange routes and rates within the Nordic seas and
    between the North Atlantic and Arctic Oceans. For example, tracing
    the East Greenland Current and its branches (Jan Mayen Current, East
    Icelandic Current), the different water masses of the interior
    basins of the Nordic Seas and details of inflow and outflow of the
    Nordic Seas, mainly in the eastern Fram Strait, the Denmark Strait
    and the Iceland-Scotland sill.

2)  means of quantifying further contributions from anthropogenic
    (bomb-tests, nuclear accidents and nuclear reprocessing facilities)
    releases.

3)  a tool for understanding of preservation and/or dissipation and
    cycling behaviour of radioactive isotopes between the oceans and
    ocean sediment which is crucial knowledge for tracer modelling.

4)  basic data about the interaction between chemical entities that
    share the same environment (the ocean), but have variable
    geochemical behaviour.

The use of chemical tracers (natural and anthropogenic) has expanded our
understanding of circulation pattern and ventilation rates in the ocean.
For example, tritium (^3^H), helium (^3^He) and chlorofluorocarbons
(CFCs) were valuable tools for estimating age and ventilation in the
North Atlantic, among other oceans. Numerous studies have, however,
shown that we are still far away from complete understanding of most
oceanic processes and further development in tracer technology can,
without doubt, substantially increase our knowledge.

In addition to basic oceanographic research, two issues have strongly
increased the interest in oceanic tracers. These are: 1) significant
influence of the ocean circulation on climate and 2) the fate of
man-made pollution in the environment. Recent studies indicate that even
the pristine environment of the Arctic Ocean has not been spared from
man-made pollution and evidently this process is rapidly increasing.
This dilemma needs to be evaluated or at least carefully understood with
all possible scientific methods and tracer technology provides important
approaches to resolve problems related to the temporal and spatial
variability of oceanic processes. Three problems are generally faced
during such approaches: 1) sensitivity of the tracer and analytical
techniques 2) origin of the tracer and 3) the span of time window to be
used. To overcome these problems, we plan to investigate,
simultaneously, the distribution of two radioactive tracers (^129^I and
^10^Be) and to compare them with other tracer data from the Odin-Knorr
cruises.

The radioactive isotopes to be used in this study are ^129^I (half-life
15.7 million years) and ^10^Be (half-life 1.5 million years). These
isotopes have different source, geochemical cycle and residence time in
the ocean and thus form a strong base for integration of oceanic
processes. Although these isotopes are produced by interaction of cosmic
rays with the Earth\'s atmosphere and surface, ^129^I is also naturally
produced by the spontaneous and neutron-induced fission of ^238^U. From
the middle of the last century ^129^I is produced anthropogenically.
This latter source has apparently contaminated large areas of the oceans
and lands and elevated the natural ratio of ^129^I/^127^I from about
10^-12^ to as much as 10^-7^-10^-10^. ^129^I is usually incorporated in
the organic cycle, but not ^10^Be. The latter is more common in
nonbiogenic particles such as clay minerals and Fe-Mn compounds.

Our interest in ^129^I is to trace spatial and temporal distribution, of
presently the voluminous release path of this isotope, from the
discharges of the nuclear fuel reprocessing facilities at Sellafield in
the United Kingdom (operating since 1954) and La Hague in France
(operating since 1965). These facilities have released up to 95% of
total anthropogenic ^129^I in the environment. This ^129^I is
transported into the North Sea, then with the Norwegian Coastal Current
to the Nordic Seas and further to the Arctic Ocean.

^129^I occurs in the biological cycle and thus forms an important tracer
in all components of the ocean (water, organisms and sediments). To
utilise chemical features of these isotopes and their ultra-sensitive
concentrations (at the levels of \<10^-8^ µg per liter of ocean water or
gram of sediments), we shall measure their distribution in different
compartments of the Nordic Seas (Iceland, Norwegian and Greenland Seas).
This approach can provide an effective tool for understanding
interactions between the North Atlantic and Arctic Oceans. The Nordic
Seas act as a mediator for the exchange of flow between the two oceans
and thus form a priority target for our investigation.

**[Measurements of ^129^I and ^10^Be at the Uppsala AMS
system]{.underline}**

The Accelerator Mass Spectrometry (AMS) is an ultra-sensitive method for
the analysis of isotopic ratios. In this method atoms are ionised from a
sample, then they are accelerated to high energies and separated
according to their momentum, energy and charge. This gives the
discrimination between ions of interest and interfering ions. At the end
every ion is individually counted on the detector and identified by its
atomic number and mass. Typical AMS energies are located in millions of
electron volts (MeV) region, whereas traditional mass spectrometry deals
with thousands of electron volts (keV). Such high energies of AMS are
necessary for obtaining the proper sensitivity for isotopic analysis; at
isotopic ratio of 10^-15^ that is about 5 orders of magnitude more
sensitive than in most conventional mass spectrometry systems.
Additional features of AMS are much faster analytical time and smaller
amount of sample.

The investigation of ^10^Be and ^129^I at Uppsala was started in 1990
and 1995 respectively with the necessary technical development of the
accelerator and detection system. Chemical separation procedures of the
isotopes from water and solid materials (sediment, rocks and variety of
organic matters) were developed.

**[Data and co-operation]{.underline}**

Data of the project are expected to be ready within the years 2003/2004.

The project will benefit from collaboration with the other research
groups attended the cruise in particular with Jean-Claude Gascard's
group in order to have complete coverage of the main oceanographical
features of the Nordic Seas.

# 

# Sampling locations 

# 

In order to comply with the selected objectives, samples of the seawater
(Oden, Knorr) and rainwater (Knorr) were taken.

Surface samples were taken from almost all stations, but the deep water
sampling program was carried out on the following stations

The Iceland Sea -- 4, 7, 9, 11

The Jan Mayen Current -- 15

The Greenland Sea -- 17, 18, 20, 24, 26, 29

The eastern part of the Fram Strait: 33, 35, 36, 37, 39

Section 75 20N (from the Greenland Sea to the West Spitsbergen Current):
41, 43, 45, 48

Section 18 E (from Spitsbergen to Norway): 54, 56, 59, 61, 63, 65, 67

> Section 70 N (the Norwegian Sea, the Iceland Sea, the East Greenland
> Current): 68, 70, 71, 73, 75, 79, 84, 88, 91, 94, 95

Section 66 N (the Norwegian Sea): 101, 103, 108, 111, 114, 123

Section Station M-Faeroe (the Norwegian Sea): 129, 131, 132, 133, 134.

Iceland-Faeroe: 139, 141, 142, 144, 145, 146

Faeroe Bank Channel: 149

Faeroe-Shetland: 153, 154, 155, 157, 158, 159

A total of about 430 samples were collected

**I-129 samples collected by LOYDC (J.-C. Gascard)**

Iodine 129 (I^129^) is a powerful tracer for improving our understanding
of the general circulation in the North Atlantic subpolar gyre and the
Arctic Ocean (pathways and residence time). This is mainly due to
several factors.

\(1\) the main sources for this tracer are well known : 2 nuclear wastes
reprocessing facilities in Europe, La Hague (France) and Sellafield
(UK). The annual discharges from both nuclear reprocessing plants are
well known. These discharges have increased drastically during the mid
90s and have levelled since then.

\(2\) our ability using AMS technic to measure very low level of Iodine
129 (ratio I^129^/I^127^ = 10^-10^) from small volume samples (250
cm^3^). The sampling technic is straightforward and does not need any
special care as for sampling gases for instance.

The main contribution of our group to the Odden-Knorr joint cruises in
the NORDIC SEAS are twofold :

A/ on the short term it mainly concerns warm waters of atlantic origin :

(1) to estimate the transfer of Iodine 129 from the Norwegian Coastal
    Current into the North Atlantic Current between 60°N and 70°N

(2) to estimate the amount of Iodine 129 transported northward by the
    Norwegian Atlantic Current across Knorr section 5 (70°N) and Knorr
    section 6 (66°N), west of Norway

(3) to estimate the amount of Iodine 129 transported northward by the
    West Spitsbergen current across Knorr sections 4 and 3 (Fram
    Strait).

(4) to estimate the amount of Iodine 129 transported into the Barents
    Sea across Knorr section 4 via the Norwegian Coastal Current and via
    the Atlantic Current entering the Barents Sea south and north of
    Bear island.

(5) to compare these estimations based on samples collected in 2002 from
    R/V Knorr with similar measurements (400 samples) taken in 2000
    during MAIA (Monitoring the Atlantic Inflow towards the Arctic), in
    light of the large increase of Iodine 129 discharge occuring during
    mid and late 90s from the 2 main nuclear wastes reprocessing
    facilities in Europe

A publication resulting from measurements collected during MAIA (EU
5^th^ framewrok program) is underway.

B/ on the longer term it mainly concerns cold waters of polar (surface)
and subpolar (deep) origins:

(1) to estimate the transfer of Iodine 129 in the other cold and deep
    compartments of the North Atlantic Subpolar gyre and in particular
    via the east Greenland current and via the deep overflows (Denmark
    Strait- Faeroe-Shetland channel) in the North Atlantic.

(2) To compare the situation in 2002 with Iodine 129 concentrations
    measured in 600 samples taken during previous experiments in cold
    waters (ESOP 1 1993-1996 ESOP 2 1996- 1999, GINS august 1999) and
    more recently (250 samples) in the Irminger Sea during the OVIDE
    program

We are expecting a fruitful cooperation with the group based in Uppsala,
Sweden as far as Iodine 129 is concerned (PIs : Ala Aldahan and Vassili
Alfimov) and also with other groups attending both cruises as far as
other tracers (SF~6~, PIs : M-J. Messias and A. Watson and CFCs) and
hydrological parameters (T,S) are concerned. During the Marion Dufresne
cruise in august 1999 (GINS program) we already started a cooperation
with another swedish group from Goteborg University (PI A. Olsson) and a
first publication is underway. The data collected recently in the
Irminger sea during the experiment OVIDE on board the french research
vessel Thalassa, is a cooperation with a group in Brest (PI : H.
Mercier).

A total of about 450 samples were collected.

**[Preliminary Tritium, He-3, O-18 report (W. Smethie)]{.underline}:**

**[Preliminary noble gas report (W. Smethie)]{.underline}:**

**[Preliminary C-13 report (W. Smethie)]{.underline}:**