**CRUISE REPORT**

Ocean Atmosphere Carbon Exchange Study

AOML/OACES designation:

GAS EX-98

State Department designation:

97-118, RONALD H. BROWN, May 7-July 7, 1998

Cruise designator: RB-98-02

7-May to 7-July 1998

I. ABSTRACT

This cruise was designed to support research sponsored by the NOAA
Climate and Global Change Program under the Ocean-Atmosphere Carbon
Exchange Study (OACES), The OACES objective for this study was to
determine the air-sea fluxes of CO2 in the North Atlantic. In specific
the field components involved:

[COMPONENT]{.underline} [METHOD]{.underline}

• Direct flux measurements of CO2 -Co-variance

-Gradient

-Eddy Accumulation

• Validation/Verification -Dual deliberate tracer

\- CO2 balance water column

Biology

Advection

-O2 balance

-Halocarbon thermal disequilibrium

-Direct fluxes other gases

• Parameterization of gas fluxes -Wind speed

(gas transfer velocities) -Friction velocity

-Surface turbulence

-Whitecaps

• Opportunistic work -Utilize tracer patch for study of

CH3Br and halocarbon dynamics

-Utilize gas transfer velocities

-Intercomparison

II\. OVERVIEW OF CRUISE AND ITINERARY

[Summary:]{.underline}

Arrive Miami May 2, 1998

In port

Depart Miami May 7

[LEG 1]{.underline} OPERATIONS

Arrive Lisbon May 20

In port May 21

Depart Lisbon May 25

[LEG 2]{.underline} OPERATIONS

Arrive Ponta Delgada June 26

In port June 27

Depart Ponta Delgada June 28

[LEG 3]{.underline} OPERATIONS

Arrive Miami July 7

In port/destage July 8-10

The 3-legged cruise consisted of a leg originating in Miami, Florida on
May 7 and arriving in Lisbon, Portugal, May 20; a process study leg
between Lisbon and Ponto Delgada, Portugal from May 25- June 26; and a
return leg from Ponto Delgada to Miami from June 28-July 7, 1998.

III\. CRUISE PERSONNEL

[A. Chief Scientists]{.underline}

Leg 1. Jim Butler, CMDL

Leg 2 Rik Wanninkhof, AOML/co-chief Jim Butler, CMDL

Leg 3 Shari Yvon-Lewis, AOML

[B. Cruise Personnel GAS EX-98]{.underline}

[LEG 1]{.underline}

[Name]{.underline} [Affiliation]{.underline} [Project]{.underline}

Robert Castle NOAA/AOML SF6 tracing/pCO2/DIC

Craig Neill NOAA/AOML SF6 tracing

David Ho Columbia U./LDEO SF6 tracing

Jim Smith NOAA/CMDL closed path dry CO2 flux

Michael Hahn NOAA/CMDL closed path dry CO2 flux

James Butler NOAA/CMDL Halocarbons

Daniel King NOAA/CMDL Halocarbons

Shari Yvon-Lewis NOAA/AOML Halocarbons

Alexander Soloviev Nova U. surface turbulence

Anatoli Arjannikov Nova U. surface turbulence

Terry Thompson NSU and Exploration Technologies, Inc. surface turbulence

Walt McKeown NRL interferometry

Jennifer Hanafin RSMAS/ U. Miami interferometry

Jon Ware WHOI closed & open path CO2 flux

Jeff Hare NOAA/ETL heat & momentum

Andrew Jessup APL/U. Wash IR Imaging

Chris Zappa APL/U. Wash IR Imaging

Jesse Davis APL/U. Wash IR Imaging

Gary Wick APL/U. Wash IR Imaging

Patricial Matrai Bigelow CH3Br/production

Brian Yocis Bigelow CH3Br/production

Wayne Grosko Bigelow CH3Br/production

Heather Wright Bigelow CH3Br/production

Ryszard Tokarczyk RSMAS/ U. Miami CH3Br/degradation

Kevin Sullivan RSMAS/ U. Miami CH3Br/degradation

Michael Reynolds BNL Underway radiance

[LEG 2]{.underline}

Rik Wanninkhof NOAA/AOML SF6 tracing

Robert Castle NOAA/AOML SF6 tracing/pCO2

David Ho Columbia U./LDEO SF6 tracing/data/buoy

Kitack Lee NOAA/CIMAS SF6 tracing/data/buoy

Craig Neill NOAA/AOML SF6 tracing

Geoffrey Samuels U. Miami/CIMAS CTD

Marilyn Roberts NOAA/PMEL DIC

Dana Greeley NOAA/PMEL pCO2

Jia-Zhong Zhang NOAA/AOML Nutrients

George Berberian NOAA/AOML Oxygen

Amy Ritchie Bermuda bio. DOC

Jim Smith NOAA/CMDL closed path dry CO2 flux

Michael Hahn NOAA/CMDL closed path dry CO2 flux

James Butler NOAA/CMDL Halocarbons

Daniel King NOAA/CMDL Halocarbons

Shari Yvon-Lewis NOAA/AOML Halocarbons

Alexander Soloviev Nova U. surface turbulence

Anatoli Arjannikov Nova U. surface turbulence

Richard Sikorski RSMAS/ U. Miami interferometry

Goshka Szczodrak RSMAS/ U. Miami interferometry

Jim Edson WHOI heat & momentum

Jeff Hare NOAA/ETL heat & momentum

Mike Ohmart APL/U. Wash IR Imaging

Jesse Davis APL/U. Wash IR Imaging

Wade McGillis WHOI Closed & open path CO2 flux

John Dacey WHOI Closed & open path CO2 flux

Jeff Evan Hamilton College Heat & momentum

Heather Wright Bigelow CH3Br/production

Brian Yocis Bigelow CH3Br/production

Wayne Grosko Bigelow CH3Br/production

Ryszard Tokarczyk RSMAS/ U. Miami CH3Br/degradation

Kevin Sullivan RSMAS/ U. Miami CH3Br/degradation

Robert Moore Dalhousie, Canada Discrete halocarbons

Phil Morneau Dalhousie, Canada Discrete halocarbons

[LEG 3]{.underline}

Craig Neill NOAA/AOML Underway CO2

Daniel King NOAA/CMDL Halocarbons

Shari Yvon-Lewis NOAA/AOML Halocarbons

Ajoy Kumar RSMAS/ U. Miami interferometry

Ed Kearns RSMAS/ U. Miami interferometry

Jim Smith NOAA/CMDL closed path dry CO2 flux

Michael Hahn NOAA/CMDL closed path dry CO2 flux

Anatoli Arjannikov Nova U. surface turbulence

Heather Wright Bigelow CH3Br/production

Brian Yocis Bigelow CH3Br/production

Wayne Grosko Bigelow CH3Br/production

Ryszard Torarczyk RSMAS/ U. Miami CH3Br/degradation

Bruce Garrett Amanda, Ohio Teacher at sea

Addresses:

Bermuda Bio. : 17 Biological Lane Ferry Reach Bermuda

Bigelow: Bigelow Laboratory for Ocean Science/University of New England
180 McKown Point W. Boothbay Harbor, ME 04575-475

BNL: Brookhaven National Laboratory, Upton NY 11973

CIMAS: 4600 Rickenbacker Causeway, Miami, FL 33149

Columbia U./LDEO: Route 9W, Palisades NY 10964

NOAA/AOML: 4301 Rickenbacker Causeway, Miami, FL 33149

NOAA/CMDL: 325 Broadway Boulder CO 80303

NOAA/PMEL : OCRD, 7600 Sand Point Way N.E. Seattle WA 98115

Nova U. : Oceanographic Center, 8000 North Ocean Drive, Dania FL 33004

RSMAS/U. Miami: 4600 Rickenbacker Causeway, Miami, FL 33149

APL/U. Wash.: Applied physics laboratory. 1013 NE 40th Street, Seattle,
WA 98105

WHOI: Applied physics & Engineering 98 Water Street Woods Hole MA 02543

NRL: Naval Research Laboratory Stennis Space Center, MS 39529

IV\. OBSERVERS: None

V. CLEARANCE COUNTRIES: Portugal

VI\. OPERATIONS:

a\. Operational summary:

86 Conductivity-Temperature-Depth (CTD) stations during leg 2.

102 Expendable Bathythermograph (XBT) deployments.

Continuous along-track ADCP current profiles.

Continuous along track thermosalinograph records.

Continuous along track measurements of partial pressure of CO2,
halocarbons, total dissolved inorganic carbon (DIC), and chlorophyll.

Four times a day samples for Oxygen, DIC, and chlorophyll from underway
sampling line.

b\. Conductivity-Temperature-Depth-Oxygen Stations: 86 stations were
occupied, see below for details. A Sea-Bird model 9/11+ CTD was used on
the cruise. A 24 bottle Sea-Bird Rosette equipped with nineteen 10-l
bottles was used to collect water samples.

c\. Niskin Bottle water samples: between six and nineteen bottles were
tripped at each CTD station. The chemical and biological analyses on the
water are outlined in section VII.

d\. Continuous shipboard Acoustic Doppler Current Profiler measurements:
hull mounted ADCP data were collected continuously along the track. A
hull-mounted RD Instruments 150 Khz narrow-band acoustic Doppler current
profiler operated continuously. Velocity data, averaged in earth
coordinates using gyrocompass heading, were logged in five-minute
(approximately 300 pings) ensembles using RDI Data Acquisition Software
version 2.48. Vertical bin size was 8 meters. Range varied from 200 to
400 meters, depending primarily on sea-state. A user exit program (UE4
provided by Eric Firing, U. Hawaii) was used to interface navigation and
heading systems. Position was logged at the beginning and end of each
ensemble from a Trimble Centurion P-code GPS receiver (estimated
position accuracy of 5-10 meters). Mean gyrocompass corrections for each
ensemble were recorded from an Ashtech 3DF GPS attitude determination
system; 3DF array orientation was calibrated using P-code GPA and ADCP
bottom track comparison. These data are used in post-processing to
calculate mean ship velocity to reference ensemble means and to
compensate for dynamic gyrocompass errors. Estimated errors for an
ensemble are 1-2 cm/s for relative velocity and 3-4 cm/s for ship speed
errors due to position inaccuracy; errors induced by heading
inaccuracies are reduced to less than 1 cm/s using GPS heading data.
This total error of 4-6 cm/s over a five minute ensemble is further
reduced by averaging during post-processing; fifteen minute averages
commonly used represent an average over five kilometers for typical
cruising speed, and should be accurate to 1-3 cm/s.

e\. Continuous thermosalinograph measurements: continuous TSG
measurements were taken along the track-lines

f\. Underway measurements: continuous underway pCO2, DIC, halocarbon,
and chlorophyll measurements were taken along the track-lines. A
description of methods and procedures can be found in section VII.

g\. Co-variance measurements: The direct covariance flux system (DCFS)
combined the motion corrected velocities from a sonic anemometer with
the sonic virtual temperature, a LI-COR CO2/H2O analyzer, an Ophir
infrared hygrometer, and an Oak Ridge CO2/H2O sensor to compute
estimates of the momentum, buoyancy, moisture, and CO2 fluxes during leg
2. The system was mounted at a height of approximately 18 meters above
the sea surface on the forward jackstaff.

h\. Bow bridle: Sensors were installed on the bow of the vessel at 1.7-m
depth, using a specially designed bow frame. An initial problem with
scratching noises produced by the side cables was largely eliminated for
the end of leg 2. Three variants of the bow sensor system were tested
during Leg 1: bow sensors from TOGA COARE, Chelsea Aquapack CTD with
Alpha-Fluorometer, and Mark 317 CTD Idronaut. Most of the observations
during leg 2 were performed with the Mark 317 CTD. The frame of the
bridle broke during leg 3 and sampling had to be discontinued.

i\. Free-Rising Profiler (FRP): The profiler connected with the
\`shuttle\' (winged frame) was deployed from stern of the R/V Ronald H.
Brown using a metal frame as launch pad. After leaving the metal frame,
the profiler fell into the water and slid outside the ship\'s wake. At a
distance of about 15 to 35 meters from ship\'s wake it reaches it
maximum depth. At the desired depth (20-25 m) the pressure release
mechanism released FRP from the \`shuttle\' and the profiler turned to a
vertical orientation to measure temperature, conductivity and turbulence
in the upper 25 m.

VII\. PROJECT SUMMARY:

**Leg 1 overview by Jim Butler**

Leg 1 of GAS EX-98 was a 14-day transit from Miami to Lisbon. Science
conducted during this leg focused upon (1) mapping saturation anomalies
for CO2 and over 20 halocarbons across the North Atlantic Ocean and (2)
testing instruments and procedures for use during Leg 2. Halocarbon
saturation anomalies are to be compared with those obtained during Leg
3, after two months warming of the gyre and central ocean waters, to
obtain an estimate of the integrated air-sea exchange coefficient.
During most of this leg, the ship maintained speeds of 13 kts. or
greater over the ground with an eastward flowing current of about 1 kts.
and strong following winds. The relative wind speed was often aft of the
beam during this leg.

Equilibrium mixing ratios of gases dissolved in the surface waters were
obtained by use of two Weiss-design equilibrators, one of which was
dedicated to analyses of CO2 by the non-dispersive infrared technique,
the other dedicated to halocarbon measurements by two automated GCMS
systems. The first few days of measurements were compromised to some
extent by leaks in the equilibrator systems and by contamination from
the ship. Questions about the integrity of some of the water
measurements ultimately necessitated moving the halocarbon equilibrator
from the main lab to an outside bulkhead aft of the lab. Realized or
not, the potential for contamination by CBrClF2, CHClF2, and CH3Br,
among other gases, was higher inside the lab than outside.

All air measurements, taken from Dekabon lines extending to the bow were
compromised to some extent by the following relative winds, which tended
to blow stack gases (and leaky refrigerants?) from the ship toward the
inlets. These conditions persisted during the middle of the leg, during
which CO2 measurements were temporarily halted. Atmospheric
concentrations of many gases, however, were not influenced significantly
by relative wind direction, thus allowing reliable measurements of air
concentrations and saturation anomalies.

Slow-down time was allocated toward need and readiness of the various
experiments needing dead time or slower speeds, and by the
appropriateness of sea-state conditions for the various experiments.
Following an initial test of the CTD on the first day, after which a
number of scientists returned ashore, about 70% of the slow-down time
(dead-stop equivalent) was allocated to surface water microstructure
measurements, namely installing and re-installing the bow bridle,
testing the free rising profiler, and conducting experiments with
catamaran-suspended temperature sensors. The remaining 30% was split
evenly between requirements for testing the gradient boom and collecting
biological samples (plankton tows and bucket samples).

Considerable effort was put into trouble-shooting the infrared and
visible imagers maintained on the bow tower. By the time Lisbon was
reached, these systems were working properly.

Overall, most of the work conducted on this leg was successful, with
many of the bugs and quirks of initial operation of instruments and
sampling systems at sea worked out. This allowed many of the
investigators to begin sampling almost immediately during Leg 2, thus
allowing the simultaneous measurement of physical and chemical
properties in the air and water with minimal interruption.

Notes on the ship during leg 1:

1\. The crew has been fantastic during this entire leg. Given the
pressure they were working under from Brooklyn to Miami and finally
getting us going at sea, they were always there for scientists making
and changing requests. All of the scientists were impressed with the
sense of cooperation, helpful spirit, and competence of the crew. Also
the Captain and officers were accommodating for all of our requests, no
mater how often we had to change plans. The ship itself was an excellent
platform with almost all of our needs being met easily. A few items
recommended for improvement are included in this list.

2\. The ship\'s compressed air needs a greater delivery at higher
pressure. 40 psi isn\'t enough to do much of anything. The line with 100
psi, strung for those in the main lab was apparently attached to a small
reservoir, as we experienced some problems when instruments drew air
simultaneously.

3\. Raw power (in fact all power) in main lab (and throughout ship)
seems sufficient for now. Well see how this plays during Leg 2 with a
full complement of scientists aboard and running their instruments full
time. (Note: Power was fine during leg 2)

4\. Seawater system flow seems adequate for two Weiss-type equilibrators
and is apparently well insulated. Warming of water through the ship is
around 0.3 C at a water temperature of about 17 C. A higher flow (\>100
Liters per minute) would decrease warming substantially and would be
desired.

5\. Drains in the main lab and the hydrolab are extremely slow;
essentially inadequate. Floor drain in main lab smells like sewer. Once
plugged with duct tape, no problem, but no drain either.

**Leg 2 overview by Rik Wanninkhof**

Leg 2 of Gas Ex--98 was a process study in which a water parcel was
tagged with the gaseous deliberate tracers sulfur hexafluoride and the
isotope He-3. The tracers were both used as a water mass marker and to
determine the gas transfer velocity from the change in concentrations of
the gases with time.

Leg 2 got underway on Monday May 25 after a chaotic in-port in Lisbon.
Guided by altimetry imagery kindly provided by Gustavo Goni of AOML, we
steamed to our projected study site near 46 N, 21.5 W. After a day of
surveying a water mass with low currents, stable salinities, surface
XCO2 values hovering near 285 ppm (yielding us a 85 ppm sink), and 15-20
m mixed layer depths was selected as study site. Surface nutrients were
near zero and high chlorophyll values suggested that the region had
passed the height of the bloom.

The SF6/He-3 tracer mixture was injected on May 29 in a 3-mile streak
along with the deployment of the two pCO2 CARIOCA buoys and a GPS
drifter. Following the injection, a low speed survey was performed.
During the survey the bow harness with T, S, and O2 sensors for near
surface measurements was deployed. The harness was used whenever
conditions (low speeds) permitted.

The halocarbon groups found several anomalies in biogenic trace gases.
The most noteworthy was the large supersaturation of methyl bromide
throughout the area. En route to the study site patches with saturation
anomalies of greater than 100% were encountered.

After a week of moderate winds, the first storm has hit the study area
during the second week of the process study. From a scientific
perspective it was the \"perfect storm\", greatly changing the
conditions in water and air. The persistence of the winds facilitated
comparison of bulk versus instantaneous flux measurements under stormy
conditions. The near constant winds at 12-14 m/s made it possible to
obtain extensive measurements of friction velocity and drag coefficients
under these conditions. Water mixed layer depth increased from less than
20 m to over 30 m. For the first time during the study appreciable
amounts of nitrate and silicate were observed at the surface. The
entrainment also increased total carbon and decreased the air-water pCO2
gradient from -90 to -70 uatm. Surface water halocarbon saturation
anomalies, which were for the most part high and well developed,
decreased considerably with entrainment of air from above and water from
below. The discrete halocarbon measurements also showed that the
halogenated by- products of respiration, previously trapped just below
the mixed layer, found their way to the surface water.

The buoy trajectories and tracer patch completed a complete
counterclockwise circle of about 30 km radius during the first ten days
suggesting a warm core eddy with a cold top (SST was 0.2-0.3 lower here
compared to surrounding waters). The drogued buoys roughly followed the
patch movement. Deliberate tracer (SF6) concentrations decreased
dramatically by downward mixing, gas exchange and dispersion. Rather
than a well-defined Gaussian patch, large areas of homogeneous SF6
levels were observed that decreased nearly a factor of two every day.

The last week on site offered opportunities to study certain processes
in detail and apply some innovations to our measurements techniques. Air
CO2 gradient measurements were perfected by measuring CO2 concentrations
continuously at a fixed reference level while the gradients were
determined making it possible to account for the influence of larger
scale eddies. The CO2 co-variance measurements performed by the WHOI
group showed a very strong correlation with wind speed (friction
velocity) and good agreement with the "Wanninkhof" wind speed-gas
exchange relationship. This is the first time that co-variance
measurements agree well with the water side isotopic results.

An intensive 18-hour Lagrangian study was performed during the last week
to study diel variations in the carbon and nutrient cycles in the patch.
During the study there was a balance between potential pCO2 increases to
due to day-time heating and pCO2 decreases due to increased
photosynthesis. The trace levels of nutrients disappeared within an hour
after the sun broke out around mid-day

Methyl iodide and isoprene showed huge supersaturation anomalies (\>2000
%) in surface water throughout the experiment with decreasing trends
during stormy weather, likely caused by loss due to air-sea gas exchange
and downward mixing. Robust production, consumption and flux estimates
for methyl bromide were obtained throughout the study.

At the end of the study, the tracer patch had an estimated 20-km
diameter and SF6 tracer concentrations had dropped 3 orders of
magnitude. However, concentrations were still easily measurable at fifty
times higher than background. pCO2 levels increased rapidly en route to
the Azores, from undersaturations of --80 uatm at the study site at 46 N
to supersaturations of +10 uatm at 39 N.

NOAA ship BROWN completed the process study phase of GAS EX-98 and
headed for the Azores on June 26. Preliminary investigations of the rich
dataset indicate an extremely successful cruise that has yielded several
important breakthroughs in our understanding of air-sea fluxes of CO2
and the biogeochemical cycles of a variety of halogenated compounds.
While much of the interpretation and analyses is just beginning some of
the highlights of the process study are summarized below:

• The choice process study sites can be much enhanced by use of remote
sensing. For our study, altimeter data proved very valuable. As
corollary, these sensors will prove very useful to determine
biogeochemical mesoscale variability in the surface ocean.

• Tagging water parcels with deliberate tracers and seeding them with
drifters appears to be a near essential prerequisite to perform a
Lagrangian process study. The tracers can clearly delineate a
homogeneous water parcel for the first two weeks or so. At later stages
when the patch includes larger chemical heterogeneity, addition
(natural) tracers such as salinity and pCO2 are necessary.

• During this study most of the carbon and nutrient input into the mixed
layer could be directly related to storm events. It appears that these
episodic events to large extent control the evolution of the spring
blooms and (pCO2) in the area.

• Direct measurement of friction velocity, u\* and bulk estimates agreed
very well suggesting that robust large scale extrapolation of CO2 fluxes
is feasible using u\*

• Under the optimal conditions of this study with large CO2 fluxes and
small latent heat fluxes the isotopic and micrometeorological flux
measurements can be reconciled.

• The ocean plays a non-negligible role in the fluxes of a variety of
halogenated tracer species including methyl bromide, isoprene, and
methyl iodide.

**Leg 3 overview by Shari Yvon-Lewis**

The ship left Ponta Delgada, Azores with 8 groups continuing work that
had begun on Legs 1 and 2. These measurements included underway pCO2
with DIC, DOC, and 13C, underway halocarbon saturation anomalies, methyl
bromide production, methyl bromide degradation, interferometry, direct
flux measurements, and fine thermohaline structure. Bucket samples were
collected daily for the methyl bromide degradation and production
studies. The underway systems were all performing well as the ship left
the Azores.

The bow bridle frame was not strong enough to withstand the constant
pounding associated with pitching in the large long-period swell we
encountered the first couple of days out of the Azores. On 30 June, the
frame snapped at the welds along the backbone. The sensors were
undamaged and the both pieces of the frame were successfully recovered
thanks to the hard work of Pat Quinanola and the rest of the deck
department.

Later in the leg, the direct flux measurement systems, eddy accumulation
and eddy correlation, came online and were collecting data for the rest
of the leg. On 6 July, the ship stopped for 7 hours pointing bow into
the wind to allow for an intensive sampling period for the direct flux
measurements. During this time fluxes were measured by the eddy
accumulation system.

Overall, the third leg of this ambitious cruise was a success.

OVERVIEW OF INDIVIDUAL PROJECTS.

Sulfur hexafluoride analyses, \[SF6\] leg 2 only (Rik Wanninkhof PI,
AOML; Kitack Lee; Craig Neill; and David Ho): SF6 samples were drawn
from most of the 10-bottle CTD casts at every station to map the
horizontal and vertical extent of the tracer patch. The patch exhibited
homogeneous vertical concentrations down to the depth of the mixed
layer. The horizontal extent of the patch was determined with an
underway SF6 system drawing water from the bow-intake at two minute
intervals using a novel high efficiency equilibrator/stripper. The
horizontal extent of the patch was about 15 km in diameter by the end of
the experiment. The results from underway system were cross checked
using discrete samples every couple of hours from the same bow intake.

The concentrations in the surface water were about 1000 ppt (parts per
trillion by volume) at the start of the experiment and decreased by
about a factor of 2 per day till the third week at which point the
concentrations decreased much slower. We hypothesize that this was
caused by the patch reaching the size of the mesoscale eddy at which
point lateral advection diminishes. Final concentrations at the end of
the process study were about 1 ppt, or about 50 times background level.

Helium-3 Samples, \[3He\] (Rik Wanninkhof PI, AOML; David Ho; and Craig
Neill): 97 3He samples (with volume about 40 cc) were drawn from
selected CTD casts. The 3He will be used in conjunction with SF6 to
calculate the gas-transfer velocity and to determine the extent of
horizontal and vertical mixing. The samples were stored in copper tubes
closed tightly at both ends by means of special stainless steel
pinch-off clamps. In the laboratory at Columbia University\'s
Lamont-Doherty Earth Observatory, gases will be extracted from the
copper tubes using a vacuum extraction system and the helium isotopes
will be measured on a mass spectrometer. Neon will be separated from
helium before mass spectrometric measurement using a cryogenic cold
trap. Precision of the 3He measurement is approximately ± 2 %. Sampling
was seized after about three weeks at which point we believe that the
He-3 samples were close to background.

CTD OPERATIONS, leg 2 only (Rik Wanninkhof, AOML, PI; Geoffrey Samuels,
Dana Greeley, and Jon Shanahoff): CTD casts were conducted using a
Sea-Bird SBE 911plus CTD unit equipped with a rosette containing
nineteen 10-l Niskin bottles. The CTD unit was equipped with dual
temperature and conductivity sensors (there was no oxygen sensor).
Post-cast processing using software provided by Sea-Bird produced one
decibar pressure averages of in-situ temperature, conductivity,
salinity, potential density and potential temperature for both sets of
sensors. No bottle salinities were taken. The rosette worked well with
an occasional non-trip because of sticky release mechanisms. The problem
was remedied by spraying the mechanism with fresh water. The mistrips
occurred almost exclusively during the first four days of CTD casts.
After the fourth CTD cast, it was discovered that the water flow
connections to the Sea-Bird sensor pumps were backwards. This problem
was corrected, but the temperature and conductivity data for the first
four casts should be considered suspect. Relatively large displacements
of the thermocline (two to five meters) between downcasts and upcasts
were observed. Investigations have shown no malfunction of the pressure
sensor or of the temperature and conductivity sensors so the
displacements are probably a real phenomenon. A summary of casts is
given below:

> Date JD Casts Num Cum. Total
>
> 05/26 146 132 - 133 2 2
>
> 05/27 147 134 1 3
>
> 05/28 148 135 - 140 6 9
>
> 05/29 149 141 - 144 4 13
>
> 05/30 150 145 1 14
>
> 05/31 151 146 - 149 4 18
>
> 06/01 152 150 - 153 4 22
>
> 06/02 153 154 - 156 3 25
>
> 06/03 154 157 1 26
>
> 06/04 155 158 - 161 4 30
>
> 06/05 156 162 - 164 3 33
>
> 06/06 157 165 - 166 2 35
>
> 06/07 158 167 - 169 3 38
>
> 06/08 159 170 - 172 3 41
>
> 06/09 160 173 - 174 2 43
>
> 06/10 161 175 - 177 3 46
>
> 06/11 162 178 - 179 2 48
>
> 06/12 163 180 - 182 3 51
>
> 06/13 164 183 - 188 6 57
>
> 06/14 165 189 1 58
>
> 06/15 166 190 - 193 4 62
>
> 06/16 167 194 - 197 4 66
>
> 06/17 168 198 - 199 2 68
>
> 06/18 169 200 - 202 3 71
>
> 06/19 170 203 1 72
>
> 06/20 171 204 - 206 3 75
>
> 06/21 172 207 - 212 6 81
>
> 06/22 173 213-214 2 83
>
> 06/23 174 215-216 3 86

Fine Thermohaline Structure and Gas Exchange in Near-Surface Layer of
the Ocean (Alexander Soloviev, Nova Southeastern University\'s
Oceanographic Center and Peter Schluessel, Meteorologisches Institut,
Universitaet Muenchen, PI's; Anatoli Arjannikov, Terry Thompson).

The near-surface microstructure measurements were performed under
leadership of Arjannikov, Soloviev, and Thompson. Schluessel will
retrieve from satellite data the boundary-layer parameters and surface
fluxes for a time period covering the Gas-Exchange Experiment at the
University of Muenchen.

Bow measurements:

The sensors were installed on the bow of the vessel at a 1.7-m depth,
using a specially designed bow frame. An initial problem with scratching
noises produced by the side cables were largely eliminated (it, however,
might still exist at extreme conditions of full ship speed and rough
seas).

Three variants of the bow sensor system were tested during Leg 1: bow
sensors from TOGA COARE, Chelsea Aquapack CTD with Alpha-Fluorometer,
and Mark 317 CTD Idronaut. Most of observations during Leg 2 were
performed with the Mark 317 CTD. The main technical characteristics of
Mark 317 CTD with redundant temperature and conductivity sensors are
given in Table 1.

TABLE 1. Main technical characteristics of Mark 317 CTD Idronaut

  -------------- -------------- -------------- -------------- --------------
                 Range          Accuracy       Resolution     Time Constant

  -------------- -------------- -------------- -------------- --------------

  -------------- -------------- -------------- -------------- --------------
  Pressure       0-10 dbar      0.15% full     0.03%          50 ms
                                scale                         

  -------------- -------------- -------------- -------------- --------------

  -------------- -------------- -------------- -------------- --------------
  Temperature 1  -3..+33 oC     0.003 oC       0.0005 oC      50 ms

  -------------- -------------- -------------- -------------- --------------

  -------------- -------------- -------------- -------------- --------------
  Conductivity 1 0.. 70 mS/cm   0.003 mS/cm    0.001 mS/cm    50 ms

  -------------- -------------- -------------- -------------- --------------

  -------------- -------------- -------------- -------------- --------------
  Temperature 2  -3..+33 oC     0.003 oC       0.0005 oC      50 ms

  -------------- -------------- -------------- -------------- --------------

  -------------- -------------- -------------- -------------- --------------
  Conductivity 2 0.. 70 mS/cm   0.003 mS/cm    0.001 mS/cm    50 ms

  -------------- -------------- -------------- -------------- --------------

  -------------- -------------- -------------- -------------- --------------
  Oxygen         0.. 500%sat    1% sat         0.1% sat       0.9 s or 3 s

  -------------- -------------- -------------- -------------- --------------

The data acquisition rate is 10 samples per second. The data taken with
Mark 317 in Leg 2 in binary format have the following volume: 30 May
(25.8 MB), 31 May (22.8 MB), 1 Jun (87.6 MB), 2 Jun (32.6 MB), 3 Jun
(88.5 MB), 4 Jun (45 MB), 5 Jun (83.1 MB), 6 Jun (106 MB), 7 Jun (58.3
MB), 11 Jun (81.3 MB), 12 Jun (108 MB), 13 Jun (205 MB), 14 Jun (80.6
MB), 15 Jun (135 MB), 16 Jun (155 MB), 17 Jun (34.8 MB), 18 Jun, 20 Jun,
21 Jun, 22 Jun, 23 Jun (volume of data after 18 June has not yet been
estimated). At stations or at very low ship speeds, the bow data can be
disturbed by the reciprocal water motions. Undisturbed data will be
selected later, using the ship speed information. Preliminary analysis
shows that the bow temperature data are useful to calculate the vertical
temperature and salinity profiles, the temperature, salinity and density
contour plots, and the turbulent mixing coefficient in the upper 3 m
layer of the ocean.

Two external channels were reserved for additional fast-response
dissolved oxygen (DO) sensors. In total, we had two DO sensors of
membrane types (Idronaut and AMT) and a microhole DO sensor
(UH/Sea-Bird). Our preliminary conclusion is that the microhole sensor
is most suitable for the towing purposes. It, however, has a slow drift
and therefore should be used with a slow response membrane-type DO
sensor for calibration reference. The CTD DO data from upper bottle are
also useful for periodical calibration of the fast response DO sensors.
Preliminary analysis of the bow data suggests a close correlation
between the fine thermohaline structure and DO features in near-surface
layer of the ocean.

Free-Rising Profiler (FRP):

The measurements with FRP were made from the drifting ship. The profiler
connected with the \`shuttle\' (winged frame) was deployed from stern of
the R/V Ronald H. Brown with help of a metal frame. After leaving the
metal frame the profiler falls into the water and slides outside the
ship\'s wake a distance of about 15 to 35 meters from ship\'s wake as it
sinks. At the desired depth (20-25 m) the pressure release mechanism
released FRP from the \`shuttle\' and the profiler turned to a vertical
orientation. The FRP then ascended to the surface with a vertical
velocity of 2.5 m s-1. The data acquisition rate is 400 samples per
second.

Main technical characteristics of FRP are given in Table 2.

TABLE 2. Main technical characteristics of free-rising profiler

  ----------- ---------- ----------- ------------- ------------ ------------
              Range      Accuracy    Stability     Resolution   Time
                                     during one                 Constant or
                                     profiling                  Spatial
                                                                Resolution

  ----------- ---------- ----------- ------------- ------------ ------------

  ----------- ---------- ----------- ------------- ----------- ------------
  Pressure    0-25 dbar  0.1 m       0.01 m                    0.01 m

  ----------- ---------- ----------- ------------- ----------- ------------

  ------------- ---------- ----------- ------------- ----------- ------------
  Temperature   14.. 34 oC 0.1 oC      \<0.01 oC     0.005 oC    35 ms

  ------------- ---------- ----------- ------------- ----------- ------------

  ----------- ---------- ----------- ------------- ----------- ------------
  Fast Temp.  -2.. 35 oC 0.1 oC      0.01 oC       0.005 oC    3 ms

  ----------- ---------- ----------- ------------- ----------- ------------

  -------------- ---------- ----------- ------------- ----------- ------------
  Conductivity   1.. 6,2    0.01 S/m    \<0.001 S/m   0.0008 S/m  \~1 cm
                 S/m                                              

  -------------- ---------- ----------- ------------- ----------- ------------

  ----------- ---------- ----------- ------------- ----------- ------------
  Fluct.      +/-0.25    5%          1 mm/s        0.6 mm/s    \~1 cm
  Velocity    m/s                                              

  ----------- ---------- ----------- ------------- ----------- ------------

  -------------- ---------- ----------- ------------- ----------- ------------
  Acceleration   +/- 6 m/s2 5%                                    

  -------------- ---------- ----------- ------------- ----------- ------------

  ------------- ---------- ----------- ------------- ----------- ------------
  (own                                                           
  vibrations)                                                    

  ------------- ---------- ----------- ------------- ----------- ------------

The total number of casts performed on Leg 2 is 98. Of those, 65 casts
can be used for the turbulence analysis. The data with FRP was taken on
3 Jun (4 casts), 5 Jun (12 casts), 6 Jun (12 casts), 13 Jun (12 casts),
16 Jun (10 casts), 19 Jun (9 casts), 21 Jun (23 casts), and 22 Jun (15).
4 Casts on 31 May were done for testing purposes only. Only 1 cast on 19
Jun can be used for turbulence analysis because of problems with
pressure release mechanism. 1 Cast on 20 Jun was to test the pressure
release mechanism. The obtained data demonstrate dependence of the
dissipation rate of the turbulent kinetic energy and the mixing
coefficient in near-surface layer on the wind/wave conditions and on the
near-surface stratification.

Direct Covariance (Jim Edson, Woods Hole Oceanographic Institute (WHOI),
Wade McGillis, WHOI, Chris Fairall, ETL, PI's; Jeff Hare, NOAA/ETL): The
direct covariance flux system (DCFS) combines the motion corrected
velocities from a sonic anemometer with the sonic virtual temperature, a
LI-COR CO2/H2O analyzer, an Ophir infrared hygrometer, and an Oak Ridge
CO2/H2O sensor to compute estimates of the momentum, buoyancy, moisture,
and CO2 fluxes. The system is mounted at a height of approximately 18
meters above the sea surface on the forward jackstaff. The system also
logs all the mean meteorological measurements required for the bulk
aerodynamic method, including wind speed and direction, air temperature,
sea temperature, relative humidity, solar and long-wave radiation, and
pCO2 concentrations in the air and sea. The data set also includes
measurements of the significant wave height using a bow mounted
altimeter; and salinity, conductivity and dissolved oxygen using a YSI
probe in the sea-water intake line. These systems have been run almost
continuously during the cruise. Preliminary results indicate that the
momentum flux estimates from the direct covariance and bulk methods are
of very high quality. After removal of runs with relative wind
directions greater than +/- 90 degrees and heading changes greater than
40 degrees, these estimates agree to within 20 % with a systematic
offset of approximately 5%. Preliminary calculations of the transfer
velocity from the CO2 flux measurements are encouraging.

Profile Flux Measurements (John Dacey, WHOI; Wade McGillis, WHOI PI's;
Jeff Evans, Hamilton College): The profile system measured vertical
profiles of dimethyl sulfide (DMS), CO2 and water vapor. The DMS
measurements were made using a micro-GC deployed on the front of the
ship, while the CO2 measurements were made using two additional LI-COR
sensors. The profile measurements were made by moving the sensor inlets
at the end of tubes to various locations well above and/or well outboard
of the ship\'s bow (\~7m to port). Measurements extended to 4-5 m below
the profiling boom, which is approximately 3-2 meters about the mean
water surface. Additional measurements of the DMS concentration in the
near surface water were made using a chemiluminescence detector. The DMS
measurements show the expected large gradients.

The difficulty in measuring the small CO2 gradients has been offset
somewhat through use of two sensors: one unit at a fixed height and
other measuring the concentration at the moveable inlet. Referencing the
mobile tube to the fixed unit has allowed the measurements of
differences on the order of 5-200 ppb (CO2) and 0.001-0.8 ppt (H2O). As
expected, water vapor profiles are most pronounced in low humidity
(\<80% RH) conditions, while CO2 profiles are most consistent at high
humidity (80-95% RH) where the fluctuations due to the \"Webb
correction\" are minimized. Preliminary calculations of the transfer
velocity from these flux measurements are also encouraging.

IR Remote Sensing (Adrew Jessup and William Asher PI, Applied Physics
Laboratory, UW; Jesse Davis, Mike Ohmart, Applied Physics Laboratory,
UW): Infrared radiometry was used to obtain sea surface temperature
measurements continuously. Four radiometers measured SST while three
radiometers provided a sky temperature correction for the imperfect
emissivity of water. A constantly towed thermistor provided the bulk
temperature at one meter. Infrared imagery was used to determine the
bulk-skin temperature difference. IR imagery is a powerful technique due
to its ability to resolve thermal structure and turbulent processes
involved in heat flux. Our use of imagery emphasizes the observation
microscale breaking waves and their role in air-sea heat flux. Results:
200 GB of raw data that we have not yet reviewed. A real whitecap
coverage was also measured continuously. We also tried to obtain an
temperature-depth profile in the upper one meter. The platform was the
\'Husky Cat,\' a small catamaran equipped with an assembly of Sea Bird
thermistors, at depths of 15 cm, 50 cm, and 1 m. Conditions made routine
deployment of this unit impractical, but on a calm day during Leg 1, we
measured a thermocline of 1 C in the upper meter alone.

NUTRIENTS \[NO3-, NO2- , NH4+, PO43- and H4SiO4\] (Jia-Zhong Zhang, PI,
AOML): During the Gas-Exchange 98 cruise, over 1100 samples from 63 CTD
casts were analyzed for nitrate (NO3), nitrite (NO2), ammonium (NH4),
phosphate (PO4) and silicic acid (H4SiO4). Samples were collected from
the 10-l Niskin bottles in acid washed 25-ml high density polyethylene
bottles which were rinsed at least 3 times with sample and analyzed
within 1 hour of sample collection. Nutrient concentrations were
determined using a shipboard AlpKem Flow Solution Auto-Analyzer and
modified EPA's methods (Zhang et al, 1997).

Low nutrient seawater used for wash and preparation of standards was
collected from the surface of the Sargasso Sea after the spring bloom
during first leg of this cruise. Standardizations were performed prior
to each sample run with standard solutions prepared from pre-weighed
high-purity grade standard chemicals.

Nitrite (NO2 ) was determined by diazotizing with sulfanilamide and
coupling with N-1 naphthyl ethylenediamine dihydrochloride to form an
azo dye. The color produced was measured at 540 nm and was proportional
to the nitrite concentration. A liquid waveguide capillary flowcell in
conjunction with a modified 510 monochromator was employed for high
sensitivity nitrite detection. The detection limits for nitrite were 0.5
nM. The average relative standard deviation of nitrate analysis for
these samples was 0.2%.

Samples for nitrate (NO3) analysis were passed through a home-made
copperized cadmium column, which reduced nitrate to nitrite and the
resulting nitrite concentration was then determined as described above.
The reduction efficiency of column was monitored during analysis and
replacement was made in due cause to ensure 100% efficiency. The
detection limits for nitrate were 5 nM. The average relative standard
deviation of nitrate analysis for these sample was 0.4%.

Ammonium (NH4 ) was determined by indophenol method. Ammonium ion in
seawater samples was reacted with phenol and NaDTT in the present of
nitroferricyanide as a catalyst in basic solutions to form indophenol
blue. Citrate and EDTA were used as complexing reagents to prevent the
precipitation of seawater at the high pH. reaction temperature was
controlled at 60 oC by a heater. The indophenol blue was measured at 640
nm. The detection limit for ammonium was 10 nM. The average relative
standard deviation of ammonium analysis for these sample was 1.6%.

Silicic acid in the sample was analyzed by reacting with molybdate in a
acidic solution to form B-molybdosilicic acid. The B-molybdosilicic acid
was then reduced by ascorbic acid to form molybdenum blue. The
absorbance of the molybdenum blue, measured at 660 nm, was linearly
proportional to the concentration of silicic acid in the sample, with a
detection limit of 0.01 uM. The average relative standard deviation of
silicate analysis for replicate samples was 0.2%.

Phosphate in the samples was determined by reacting with molybdenum (VI)
and antimony (III) in an acidic medium to form an
antimonyphosphomolybdate complex. This complex was subsequently reduced
with ascorbic acid to form a blue complex and the absorbance was
measured at 710 nm. The detection limit was 5 nM and the average

relative standard deviation of phosphate analysis for replicate samples
was 0.9%.

Reference

Zhang et al, 1997, Determination of nitrate and nitrite in estuarine and
coastal waters by gas segmented continuous flow analysis. Methods for
analysis of chemical substances in estuarine and coastal waters samples,
EPA.

Dissolved oxygen (Rik Wanninkhof, PI, AOML; George Berberian):
Approximately 920 discrete dissolved oxygen samples were drawn and
analyzed from designated depths on the 2nd Leg of the GAS EX-98 Cruise
in order to characterize the distribution of dissolved oxygen. Samples
were properly drawn and analyzed from approximately 58 CTDs, utilizing
the modified Winkler titration methodology.

Most samples were collected from the tracer patch, and some samples were
also gathered and analyzed from outside the patch. A very cursory
examination of a few of the profiles indicated that the surface waters
outside the patch are slightly higher (10-12 umol/l) than the surface
waters inside the patch. Also, oxygen values were slightly higher in the
waters of 160 to 350 meters, (10-15 umol/l) outside the patch. These
kinds of differences are usually attributed to phytoplankton growth,
which can cause oxygen saturation in the upper layers of the ocean.
However, a thorough examination of the distribution of dissolved oxygen
will give us a better understanding of the mechanism and effects of the
area studied. Complete set of the distribution of dissolved oxygen,
depth profiles and duplicated sample results will be available after
examining the data in the NOAA/AOML office.

TOTAL DISSOLVED INORGANIC CO2 \[DIC\] (Richard Feely, PI, PMEL; Marilyn
Roberts; Kitack Lee; and Bob Castle): In order to constrain the gas flux
determination, DIC (Dissolved Inorganic Carbon) was measured. Two
systems were operated during the cruise: an underway system took samples
every 30 minutes during all legs, and two units for discrete samples
were used for Leg 2. Both the underway and discrete DIC analyses
utilized coulometers coupled with SOMMA (Single Operator Multi-parameter
Metabolic Analyzer) inlet systems. Approximately 750 DIC samples were
taken from CTD casts on Leg 2. These samples were typically taken
throughout the water column to 450m with emphasis on the mixed layer,
but occasionally the profiles extended to as deep as 1000m to aid in
integration of the data. Subsurface waters showed DIC increasing below
the mixed layer to about 2100 umol/kg. In addition, more than 100
discrete samples were drawn and analyzed from the underway water lines
to assist in comparison of the underway DIC analyses. On Leg 1 surface
values were 2040 umol/kg in the Western Atlantic region and values
decreased to 1960 umol/kg as the ship progressed eastward. Surface
waters during the process study on Leg 2 changed over a narrow range
with highest values encountered immediately after a storm event. The
accuracy of the coulometers was checked twice a day using reference
water supplied by Dr. Dickson of Scripps (Batch 42). The discrete DIC
systems yielded the following accuracy and precision: \"PMEL-1\" gave an
average value of 1981.1+/- 1.5 umol/kg (n=26) while \"PMEL-2\" gave a
value of 1983.6 +/-1.7 (n=40). The underway DIC system (AOML 1) gave an
average value of 1981.8+/-2.4 umol/kg (n=40) The manometric value
determined at Scripps was 1985.1 +/-1.4 umol/kg. A secondary reference
material was analyzed frequently throughout the course of the cruise,
and those analyses had a precision of within 2.8 umol/kg (n=60) on both
the discrete and underway systems.

PARTIAL PRESSURE OF CO2 \[pCO2\] (Rik Wanninkhof, PI, AOML; Dana
Greeley): Approximately 700 discrete pCO2 taken and analyzed on leg 2
using a analysis system with an infrared (IR) detector. pCO2 was
measured in the headspace of a 500 mL volumetric flask at constant
temperature of 20 C. Overall precision was 1 uatm over the observed
range of 200 to 700 uatm. Discrete pCO2 values showed a similar pattern
as DIC suggesting near constant alkalinities in the survey area. Sixty
replicates were drawn with a precision of 0.277574%

UNDERWAY pCO2 measurements (Rik Wanninkhof, PI; Bob Castle):
Quasi-continuous samples were taken of air and water pCO2 using an
automated system with sampling lines connected to the bow air intake and
the continuous bow water supply. During leg 1 the CO2 was slightly
undersaturated compared to the atmosphere. A small leak in the system
caused the values to scatter. The leak was fixed at the beginning of leg
2 and the values will be corrected for. At the process site the values
reached an undersaturation of --90 uatm, the largest deficit we have
encountered to date over the ocean. The system operated with minimal
operator intervention

CARBON-13 SAMPLING \[DIC-13\] (Paul Quay, PI, U. Washington; Marilyn
Roberts; Craig Neill): The primary goal of the sampling plan for the
carbon isotopic ratio of DIC (DIC-13) was to determine the distribution
of the 13C/12C in the North Atlantic and to study the evolution of C-13
over time in the tracer patch. DIC-13 samples were collected every 3
degree spacing on the transit legs. Full depth profiles were taken at 5
stations during the process study. The total samples collected was 200.
The samples have been fixed, sealed and prepared for transit. The
samples will be stored in a temperature controlled environment on the
BROWN until they can be shipped back to Seattle for analysis.

Dissolved Organic Carbon and Nitrogen (Dennis Hansell PI, Bermuda
Biological Station for Research; Amy Ritchie, Bermuda Biological Station
for Research).

Water column profiles of DOC were determined using the high temperature
catalytic oxidation method. The DOC reservoir is an important factor in
determining the overall mass carbon balance. DOC and DON samples were
obtained from CTD stations occupied on the second leg. An average of 15
depths were collected from the tracer patch during each day, in addition
to 5-10 depths collected within each survey site. Initial DOC values
appear to be relatively high within the mixed layer, although due to
inconsistent concentration resolution, all samples have been archived
for further analysis in the lab.

Organohalogen measurements, \[CFC\'s\] (Dr. Robert Moore PI, Dalhousie
University and Phil Morneau): The objectives of this study are to
determine whether the ocean is a source to the atmosphere of a number of
volatile organochlorine compounds and to determine whether their
distribution in the water column is indicative of production by
biological processes.

The compounds, which included methyl chloride, bromide and iodide,
dichloromethane, chloroform, tri- and tetra-chloroethylene, were
measured in water samples collected from depths of 0 to 450m. Analyses
were done by purge-and-trap and GC-MS techniques and calibration was
done with gravimetric gas standards. The same compounds were measured in
8 incubation experiments, designed primarily to quantify methyl bromide
production.

Methyl iodide showed variable but typically high concentrations in
surface and near-surface waters, and methyl bromide was supersaturated.
Trichloroethylene was found to be supersaturated, with concentrations
increasing with depth in the water column to at least 450m; its profiles
are not similar to those normally associated with biogenic gases, such
as methyl bromide, methyl chloride and isoprene.

After 23 days of measurements, high levels of noise in the
mass-selective detector precluded further analyses.

HALOCARBON THERMAL DISEQUILIBRIUM FLUX MEASUREMENTS (James Butler, CMDL,
PI, Dan King, CMDL/CIRES,): The saturation states of a number of
conservative and reactive halocarbons including CH3Br were measured
continuously during Legs 1, 2, and 3. Water from the continuous underway
seawater system flowed through an equilibrator, where headspace samples
were collected periodically for analysis by a gas chromatograph/mass
spectrometer system (GC/MS). Air was also continuously pumped from an
inlet located on the jackstaff, and samples were collected alternately
with the equilibrator headspace samples for analysis by the GC/MS
system. The difference between the water and air values is a measure of
the saturation of a given trace gas. There were some difficulties with
the equilibrator during the early part of Leg 1, but the problems were
solved by the last quarter of that Leg.

During the course of this cruise, the waters being sampled warmed due to
radiative heating. The warming was approximately +1.5 ºC during leg 2 in
the intensive study area, and the warming of an area near the Azores
that was sampled during Leg 1 and re-sampled at the end of Leg 2 was
+2.5ºC. This warming affected the solubility of the halocarbons. The
change in solubility is faster than escape to or invasion from the
atmosphere. The continuous measurement of the saturation state and the
degree of warming that occurred will allow us to calculate the
time-averaged air-sea transfer velocities for the conservative trace
gases. For the reactive halocarbons, where the temperature and salinity
dependent degradation rates are known, similar calculations that include
this additional loss in the surface water will be made.

METHYL BROMIDE SATURATION ANOMALIES (Shari Yvon-Lewis, AOML, and James
H. Butler, CMDL, PI's, Dan King, CMDL/CIRES): Atmospheric CH3Br, which
is of both natural and anthropogenic origin, has been identified as a
Class I ozone-depleting substance in the amended and adjusted Montreal
Protocol on Substances that Deplete Stratospheric Ozone. The role of the
ocean in regulating the atmospheric burden of this gas is still somewhat
uncertain. Saturation anomalies for methyl bromide (CH3Br) were measured
with the technique described above. The results from these measurements,
when combined with the CH3Br production CH3Br degradation, and
organohalogen depth profile measurements made on this cruise, are
twofold. First, the surface ocean budget for this class I ozone
depleting trace gas is now well defined for the study area at this time
of year. Second, by closing the budget, we can apply calculations
similar to those mentioned in the thermal disequilibrium section to
calculate air-sea transfer velocities for CH3Br.

Methyl bromide production (P. Matrai, PI, Bigelow Laboratory for Ocean
Science; B. Yocis, W. Groszko, H. A. Wright): Incubations of surface and
deep water were carried over 48h periods semi-continuously during all 3
Legs; methyl bromide and chlorophyll a levels were followed on board.
Discrete samples for methyl bromide were analyzed on board with a GC-ECD
system; four time points were determined for each incubation and whole
water as well as filtered (1 um and 0.2 um) water were monitored in
parallel. During each incubation, samples have also been collected for
phytoplankton identification, bacterial enumeration, and particulate
organic carbon. Surface water was obtained from the bow intake at 5 m
depth as well as from CTD casts and as bucket samples; comparisons from
all 3 sources yielded no significant differences. Deep samples were also
collected during Leg 2 at various depths, determined according to either
physical, chemical, or biological characteristics of the water column.
During Leg 1, 30 incubations were performed; emphasis was on spatial
coverage as well as on sampling, experimental, and analytical
replication. Analytical difficulties dramatically slowed our progress
during the first half of Leg 2 but were solved, allowing 50 incubations
to be done. We expect to do ca. 20 incubations during Leg 3, emphasizing
spatial coverage as was done during Leg 1. In addition, during Leg 2,
vertical profile samples were collected for chlorophyll and particulate
organic carbon. Preliminary results show a slight or no net production
of methyl bromide in these seawater incubations while net disappearance
of methyl bromide was less common; the data need to be further analyzed
back in the laboratory before final conclusions can be drawn.

METHYL BROMIDE DEGRADATION (Eric Saltzman, RSMAS/U. of Miami, PI,
Ryszard Tokarczyk, Kevin Sullivan): The rates of degradation of 13-C
labeled methyl bromide were measured in the surface water of Atlantic
Ocean during the legs 1, 2 and 3. Typically, 2 samples were collected
each day and spiked with 13-C methyl bromide to the concentration of
about 500 pM and incubated at the same temperature as they were
collected. One of the samples was usually filtered prior to spiking
through 0.2 micron Anatop filter, second was spiked without any
pretreatment. During the leg 1 and 3 water was collected with the bucket
directly from the surface. During leg 2 samples were collected from
Niskin bottles, typically from 2 depth -- about 5 and 20m. A few samples
were collected in the deeper layer between 200-500m. An influence of the
diurnal cycle at the degradation abilities of water collected at the
same sampling site was examined twice during the leg 2.

27 incubation were performed during leg 1. Degradation rates ranged from
8 % per day for open Atlantic waters (37 46 N, 50 33 W, temp 20 C, sal.
36.4) to 66% per day for warm waters of Gulf Stream current (27 C, 36.3
salinity), with the majority of samples falling into the range of about
15-20% per day. The degradation rates observed in filtered samples were
usually lower then those observed in untreated ones.

75 incubations were performed during leg 2. The temperature and salinity
of surface water remain nearly constant (temperature vary from 15-16 C,
salinity from 35.7-35.9). The observed degradation rates were lower then
those observed during leg 1, and varied from 6% to 17% per day, with
10-12% as average. The differences between filtered and unfiltered
samples were negligible. The results of the diurnal cycle study exhibit
that degradation rates were significantly higher in the samples
collected late at the day in comparison to samples collected early in
the morning.

13 incubations were performed during leg 3. The degradation rates varied
from about 10% for open ocean waters to 27% per day for warmer (25 C,
36.4 salinity) waters of west Atlantic.

HALOCARBON GRADIENTS (James Butler, CMDL, PI, Shari Yvon-Lewis, AOML,
and Dan King, CMDL/CIRES): Halocarbon vertical profiles were measured
with a gas chromatograph/mass spectrometer (GC/MS) system. The sample
collection system consisted of a set of flasks that were flushed with
air, each from an inlet at a different height above the sea surface. The
flasks were closed simultaneously and analyzed sequentially with the
GC/MS. The system was completely automated. From 6 to 8 profiles were
collected and analyzed per day during Leg 2. Occasional bad weather
necessitated removing the lower inlets and pulling in the sampling boom.
Therefore, there were some days when gradient measurements were not
possible. Post cruise data analysis will determine which of the measured
gases are most suitable for calculating gas transfer velocities.

DIRECT FLUX MEASUREMENTS (Pieter Tans, CMDL, PI, Jim Smith, Atmospheric
Observing Systems, Michael Hahn, CMDL/CIRES): The objective was direct
measurements of the flux of carbon dioxide from the ocean\'s surface by
three separate techniques. Each is based on the same kind of
electro-optic analyzer with different methods to process the acquired
air streams. All measurements were differential, and the two air streams
were always filtered at the source, dried to low dew point corresponding
to \< 100 ppm water vapor and equilibrated to common temperature and
pressure before analysis. Sensitivity ranged from \~10 to 1 ppb in one
hour of integration, depending on the stability on the ship. All
measurements are in mixing ratio units referred to dry air.

Technique #1 : The Profiler:

Concentrations of CO2 were measured from inlets held at discrete heights
above the ocean surface by a rigid boom extending approximately 5 meters
from the port side of the ship. A range of discrete heights was possible
depending on the ship speed and state of the ocean\'s surface.
Possibilities were -20, -15, -10, 0, and +25\' relative to the height of
the gunnell. We detected approximately 100 concentration differences
from pairs of inlets. Artifacts were evaluated successfully by doing
null measurements with pairs of inlets at a common height. The
concentration differences, combined with ongoing measurements of
momentum transfer, can be used to determine the CO2 flux. Site of
measurements was van on deck 02 and back 25 meters from bow.

Technique #2 : The Accumulator:

The continuous air sample was brought to the accumulator through a
single gust tube with inlet at the site of the sonic anemometer 25\' up
jack staff. Air stream was separated into up and down parcels as
directed by the anemometer, accumulated into separate cells for 20 min.
and then analyzed for CO2 concentrations. This concentration difference,
combined with ongoing measurements of the standard deviation of the
vertical wind, is a measure of flux. Site of measurements was main lab
during leg #3. Can report on 4 days of almost continuous operation.

Technique #3 ; The Correlator:

Like the accumulator, single gust tube brings unbroken stream of air
from site of anemometer into main lab at \~24 slpm. But unlike the
accumulator where analysis can be slow, the correlator measures fast CO2
fluctuations in the stream. The rate is 2 Hz. Simultaneous with the CO2
measurements, the sonic anemometer is measuring fluctuations in the
vertical wind. They are logged continuously by a second computer. The
two time series, CO2 and wind, are multiplied and then summed to provide
the measure of flux. The correlator ran alongside the accumulator in the
main lab for the last three days of leg #3. Our experiment ended with
the ship at stop for seven hours to provide exceptionally low noise
measurements with both instruments.

INTERFEROMETRY (Peter Minnet, PI, Jennifer Hanafin, Walt Mckeown,
Richard Sikorski, Goshka Szczodrak, Ed Kearns, and Ajoy Kumar): For this
project, a Marine Atmospheric Emitted Radiance Interferometer (MAERI)
was mounted topside to collect a running record (2 minute sampling
interval) of the ambient light field emitted both from the sky and the
sea surface. These data may be used to derive a variety of useful
parameters, not the least of which is the skin temperature of the sea
surface. Approximately 150 Mb of data per day, for the periods 5/7/98 to
5/20/98, 5/25/98 to 6/25/98, and 6/28/98 to 7/7/98, were collected (a
total of over 6 GB). A continuous record of the sky/clouds conditions
were recorded by a time lapse VCR (1 frame every 17 sec) connected to a
camera/fish-eye mirror arrangement which was mounted forward on the 03
deck. Regular radiosonde balloon launches were conducted twice a day
over the entire period at sea. These radiosonde profile data were saved
along with the ship\'s meteorological and thermosalinograph data for
merging with the MAERI data during later analyses. During periods when
the ship\'s speed was 8 knots or less and the sea state was at least
moderate (45 times during the course of the cruise), a thermistor was
lowered to the water\'s surface off of the ship\'s starboard bow,
providing a continuous, independent bulk estimate of the sea surface
temperature (4 Mb total).

VIII\. ACKNOWLEDGMENTS:

The officers and crew of the RONALD H. BROWN performed in an excellent
manner as summarized in the attached memorandum to the Captain.

The success of the cruise can, to a large extent, be attributed to hard
work and utmost cooperation of scientists with diverse backgrounds. The
good interactions and free exchange of preliminary data by the physical,
biological, and chemical oceanographers and meteorologists facilitated
the creation of a high quality data set.