PRELIMINARY CRUISE REPORT 
mod. 14 April 2004


A.  CRUISE NARRATIVE (A20_2003a) 

A.1  HIGHLIGHTS 

                        WHP CRUISE SUMMARY INFORMATION

                WOCE section designation  A20_2003a
       Expedition designation (ExpoCode)  

Chief Scientist(s) and their affiliation  Dr. John Toole/WHOI
                                          Dr. Alison MacDonald 

                                   Dates  22 September 2003 - 20 October 2003
                                    Ship  R/V Knorr
                           Ports of call  Woods Hole, Ma. - Port of Spain, Trinidad
                                          
                      Number of stations  

                                                      4314.98'N
         Stations' Geographic boundaries  6138.8'W              5036.97'W
                                                      658.63'N

            Floats and drifters deployed  
          Moorings deployed or recovered  

                    Contributing Authors  None listed
                                          
 
                              Data Submitted by:
      Oceanographic Data Facility  Scripps Institution of Oceanography 
                         La Jolla, Ca.  92093-0214


SUMMARY

A hydrographic survey consisting of LADCP/CTD/rosette sections and float 
deployments in the western North Atlantic was carried out September to October 
2003.  The R/V Knorr departed Woods Hole, Ma. on 22 September 2003.  A total 
of 88 LADCP/CTD/Rosette stations were occupied, and 5 profiling ARGO floats 
were deployed from 24 September - 18 October.  Water samples (up to 36), LADCP 
and CTD data were collected in most cases to within 10 meters of the bottom.  
Salinity, dissolved oxygen and nutrient samples were analyzed from every 
bottle sampled on the rosette.  The cruise ended in Port of Spain, Trinidad on 
20 October 2003.  

INTRODUCTION

Knorr cruise 173 was conceived to reoccupy two meridional hydrographic 
sections in the western North Atlantic as part of the CLIVAR/Global Carbon 
Program of repeat hydrography.  The section designated "A20" by the World 
Ocean Circulation Program that lies nominally along 5220'W was sampled during 
leg 1.  The return leg to Woods Hole reoccupied the A22 section along 66W.  
Meridional hydrographic sections near 52W had been made on three occasions 
prior to our cruise: in the 1950's, 1980's, and in 1997.  The sampling plan 
for the 2003 occupation was simply to make a full-depth hydrographic station 
at (virtually) each site sampled in 1997.  (The extremely tight station 
spacing at the northern end of the section done in 1997 was relaxed slightly 
in 2003.)

A sea-going science team gathered from ten oceanographic institutions around 
the U.S. participated on the cruise.  Several other science programs were 
supported with no dedicated cruise participant.  The science party and their 
responsibilities are listed below:

SCIENCE PARTY AND RESPONSIBILITIES

      John Toole                ChiefScientist            WHOI
      Alison Macdonald          Co-Chief Scientist        WHOI
      Rebecca Zanzig            Student participant       UW

HYDROGRAPHIC OPERATIONS AND DATA ANALYSIS

      Scott Allen                                         SIO
      Ruth Curry                                          WHOI
      Frank Delahoyde                                     SIO
      Carl Mattson                                        SIO

WATER SAMPLE ANALYSTS

      John Calderwood           Oxygen                    SIO
      Bettina Sohst             Oxygen                    UCSC
      Susan Becker              Nutrients                 SIO
      Erik Quiroz               Nutrients                 U. Southern Miss.  
      Deborah LeBel             CFC                       LDEO
      James Happell             CFC                       RSMAS
      Eugene Gorman             CFC                       LDEO
      Ryan Ghan                 CFC                       LDEO
      Marilyn Roberts           DIC                       PMEL
      Kevin Sullivan            DIC                       AOML
      George Anderson           TALK                      SIO
      J. Martin Hernandez Ayon  TALK                      SIO
      Josh Curtis               He-3/Tritium              WHOI
      Norm Nelson               CDOM, DOC, DON            UCSB
      Jonathan Klamberg         CDOM, DOC, DON            UCSB
      Stuart Goldberg           CDOM, DOC, DON            UCSB
      Tim Newberger             LADCP                     LDEO
    
R/V KNORR SCIENCE TECHNICIANS    
    
      Robert Laird    
      Amy Simoneau    
    
OTHER SCIENCE PROGRAMS

      Eric Firing               Shipboard ADCP            U. Hawaii
      Jules Hummon              Shipboard ADCP            U. Hawaii
      Ann McNichol              Surface C14               WHOI
      Robert Key                Surface C14               Princeton
      Paul Quay                 C13 profiles              UW
      Allyn Clarke              Profiling ARGO floats     BIO, Canada
      Wilf Gardner              Transmissometer profiles  TAMU
                  
                  


CRUISE NARRATIVE

Skirting Hurricane Fabian during her transit from the Mediterranean, the R/V 
Knorr arrived back in Woods Hole on schedule and was available for loading 
during the week of September 15.  Most groups took full advantage of this time 
to set up and test their instrumentation.  For tunately the threat that 
Hurricane Isabel would disrupt these activities was averted when that storm 
passed well inland of the Cape.  Departure from Woods Hole occurred at 1300 
local on September 22 in fine weather.  

Unlike in 1997 when the section was staged out of Halifax, Nova Scotia, we 
were immediately faced with a 3-day transit to the head of the section at the 
southern tip of the Grand Banks.  Enroute to the Banks, a full-depth test 
station was occupied in approximately 4000 m of water on Sept. 24.  Station 1 
of the A20 section was occupied in the evening of September 25.  

Study of satellite-derived sea surface temperature images, both relayed from 
shore and captured directly aboard Knorr with the Terascan system, suggested 
the presence of a warm water flare extending north from the Gulf Stream that 
nearly paralleled our planned station track.  We therefore diverged from the 
1997 station plan at station 11, orienting the next set of casts along 5148' 
W to sample east of the flare.  After grazing the western edge of a small Gulf 
Stream Ring, the section extended south on this meridian within a trough 
(southward meander) of the Stream until intersecting the "North Wall" at 
station 17.  Shipboard ADCP data showed strong surface currents directed to 
the Southeast here, and so the station track was adjusted to the Southwest to 
cross the Gulf Stream more-or-less perpendicularly to the flow.  As the 
surface currents turned more zonal with distance south, the section track was 
oriented more meridionally.  

Profiling drifting floats supplied by Allyn Clarke (Bedford Institute of 
Oceanography) were deployed at predetermined sites along this segment of the 
A20 track.  During this period, Hurricane Juan formed and moved north to our 
west, eventually striking Haifax, Nova Scotia.  

By station 26 at Lat. 35.5N we were across the main core of the Gulf Stream 
and back on the 1997 station plan that placed stations every 40 nmi through 
the center of the subtropical gyre.  But intensifying to our east was 
Hurricane Kate that forecasts showed would soon intersect our cruise track.  
Hoping to extend south of her projected course, station spacing was widened to 
80 nmi (skipping every other planned station) between latitudes 34.8 and 
33.5N (Stas .27-29).  Facing increasing winds and swells, the planned station 
at 3051'N was deferred and we ran south to escape the storm.  

Sampling resumed with Station 30 situated at 26.2N on the nominal A20 
meridian, with subsequent stations directed back to the north at 40 nmi 
spacing.  By adjusting weight on the water-sampler frame and reducing 
lowering/raising rates on the sea cable, we were able to slowly work our way 
back to the deferred station site despite rather confused swell and wave 
conditions.  Sea cable re-terminations were required after several of these 
stations to remove wire kinks presumably caused by snap loading of the sea 
cable caused by ship roll/heave.  Upon completion of the station at 3051' N 
(number 37) we transited back south to resume working the line.  During the 
transit (referred to by one New Englander as a "school snow day") many of the 
science party and crew put up with very poor radio reception to cheer the Red 
Sox to victory in Game 5 against the A's.  Station 38 at Lat. 25.5N was 
occupied in the late afternoon of October 7 in much improved weather and sea 
conditions.  

The station work was continued south as planned along the nominal A20 
longitude to station 64 in excellent weather conditions.  Thereafter, the 
cruise track was directed to the southwest in order to perpendicularly cross 
the bathymetric contours off the Surinam coast.  At this time, tropical 
storm/hurricane Nicholas began to form east of our track about Longitude 48W.  
Fortunately it was far enough west and north of our position that it did not 
impact our sampling.  However, dense cloud cover and rain were experienced for 
the first time on the cruise, impacting the UCSB incubation experiments.  

During the up-cast of Station 66, one of the electrical conductors in the sea 
cable developed a short to ground.  The underwater package was recovered and 
operations were shifted to the other winch/wire system.  A second cast was 
made at this site to pick up the upper-ocean water samples that were missed 
after the wire problem.  Just landward of Station 66, we crossed into the 
territorial waters of Surinam.  All underway data files were closed and 
reopened at this point to facilitate delivery of territorial-waters data to 
Surinam.  During station work on the evening of October 17/18 the R/V Knorr 
contingent of Red Sox Nation was agonized by their team's loss of ALCS game 7 
to the Yankees.  Hydrographic sampling on the A20 line was completed on 
October 18 at 02:51 GMT with station 88 at 659.0' N, 5334.2' W in 77 m of 
water.  The vessel was then directed to Trinidad, arriving off Port O'Spain in 
the morning of October 20.  R/V Knorr was secured quayside by 09:10 and was 
cleared shortly thereafter.  

Apart from the three stations that were skipped about the middle of the 
subtropical gyre when we were running from Hurricane Kate, all other planned 
hydrographic stations were successfully occupied.  The science parties and the 
officers and crew of the R/V Knorr are to be commended for their hard work and 
careful measurements.  All of the sampling teams were briefed on the schedule 
for submitting preliminary and final data sets and agreed to meet the target 
submission dates.  



1.  DESCRIPTION OF MEASUREMENT TECHNIQUES

1.1.  CTD/HYDROGRAPHIC MEASUREMENTS PROGRAM

The basic CTD/hydrography program consisted of salinity, dissolved oxygen and 
nutrient measurements made from bottles taken on CTD/rosette casts, plus 
pressure, temperature, salinity, dissolved oxygen and transmissometer from CTD 
profiles.  Atotal of 92 CTD/rosette casts were made, usually to within 10 
meters of the bottom.  No major problems were encountered during the 
operation.  The distribution of samples is illustrated in figures 1.1.0 - 
1.1.3.  


FIGURE 1.1.0:  Sample distribution, stations  1-27.  
FIGURE 1.1.1:  Sample distribution, stations 27-38.  
FIGURE 1.1.2:  Sample distribution, stations 38-52.  
FIGURE 1.1.3:  Sample distribution, stations 52-88.  


1.2.  WATER SAMPLING PACKAGE

LADCP/CTD/rosette casts were performed with a package consisting of a 36-
bottle rosette frame (ODF), a 36-place pylon (SBE32) and 36 10-liter Bullister 
bottles (ODF).  Underwater electronic components consisted of a Sea-Bird 
Electronics (SBE) 9plus CTD (ODF #474) with dual pumps, dual temperature 
(SBE3), dual conductivity (SBE4), dissolved oxygen (SBE43), transmissometer 
(Wetlabs C-Star) and fluorometer (Seapoint Sensors); an SBE35RT Digital 
Reversing Thermometer, RDI LADCPs (Workhorse 300khz/Broadband 150khz) and a 
Simrad 1007 altimeter.  

The CTD was mounted horizontally along one side of the bottom center of the 
rosette frame.  The SBE sensors and pumps were deployed horizontally along the 
CTD pressure case, as were the transmissometer and fluorometer.  The LADCP 
battery pack was mounted alongside and outboard from the CTD.  The LADCPs were 
vertically mounted inside the bottle rings on the opposite side of the frame 
from the CTD and LADCP battery pack, with one set of transducers pointing 
down, the other up.  The SBE35RT temperature sensor was mounted horizontally 
on a support strut, within 0.25 meters of the CTD pump intakes.  The altimeter 
was mounted on the inside of support strut outboard from the LADCP battery 
pack.  

The rosette system was suspended from a UNOLS-standard three-conductor 0.322" 
electro-mechanical sea cable.  The R/V Knorr's starboard-side CTD winch was 
used on stations 1-11 and 30-66.  This winch developed mechanical problems on 
cast 11/1, and a sea cable short on cast 66/1.  The port-side CTD winch was 
used on stations 12-29 and 66-88.  The sea cable on this winch developed 
numerous kinks due to storm surge twisting, particularly on cast 36/1.  
Several sea cable reterminations were made on this cruise.  

The deck watch prepared the rosette 10-20 minutes prior to each cast.  All 
valves, vents and lanyards were checked for proper orientation.  The bottles 
were cocked and all hardware and connections rechecked.  Once stopped on 
station, the LADCP was turned on and the rosette moved into position under the 
starboard boom via an air-powered cart and tracks.  As directed by the deck 
watch leader, the CTD was powered-up and the data acquisition system started.  
Two stabilizing tag lines were threaded through rings on the rosette frame, 
and syringes were removed from the CTD sensor intake ports.  The deck watch 
leader directed the winch operator to raise the package, the boom and rosette 
were extended outboard and the package quickly lowered into the water.  The 
tag lines were removed and the package was lowered to 10 meters.  The CTD 
console operator then directed the winch operator to bring the package close 
to the surface, pause for typically 30 seconds and begin the descent.  

Each rosette cast was lowered to within 10-20 meters of the bottom (with a few 
exceptions).  

Each Bottle on the rosette had a unique serial number.  This bottle 
identification was maintained independently of the bottle position on the 
rosette, which was used for sample identification.  No bottles were changed or 
replaced on this leg, although parts of a few of them were replaced or 
repaired.  

Recovering the package at the end of the deployment was essentially the 
reverse of launching, with the additional use of poles and snap-hooks to 
attach air tugger-powered tag lines for added safety and stability.  The 
rosette was moved into the CTD hangar for sampling.  The bottles and rosette 
were examined before samples were taken, and anything unusual noted on the 
sample log.  

Routine CTD maintenance included soaking the conductivity and CTD DO sensors 
in distilled water between casts to maintain sensor stability.  Rosette 
maintenance was performed on a regular basis.  O-rings were changed as 
necessary and bottle maintenance was performed each day to insure proper 
closure and sealing.  Valves were inspected for leaks and repaired or replaced 
as needed.  


1.3.  UNDERWATER ELECTRONICS PACKAGES

CTD data were collected with a SBE9plus CTD (ODF #474).  This instrument 
provided pressure, dual temperature (SBE3), dual conductivity (SBE4), 
dissolved oxygen (SBE43), transmissometer (Wetlabs C-Star), fluorometer 
(Seapoint Sensors) and altimeter (Simrad 1007) channels.  CTD #474 supplied a 
standard Sea-Bird format data stream at a data rate of 24 frames/second (fps).  


TABLE 1.3.0:  A20 ROSETTE UNDERWATER ELECTRONICS.  

Sea-Bird SBE32 36-place Carousel Water Sampler  S/N 0187
Sea-Bird SBE35RT Digital Reversing Thermometer  S/N 0034
Sea-Bird SBE9plus CTD                           S/N 09P9852-0474
Paroscientific Digiquartz Pressure Sensor       S/N 69008
Sea-Bird SBE3plus Temperature Sensor            S/N 03P-4138 (Primary)
Sea-Bird SBE3plus Temperature Sensor            S/N 03P-2359 (Secondary)
Sea-Bird SBE4C Conductivity Sensor              S/N 04-2419 (Primary)
Sea-Bird SBE4C Conductivity Sensor              S/N 04-1908 (Secondary 1/1-1/17) 
Sea-Bird SBE4C Conductivity Sensor              S/N 04-2572 (Secondary 18/1-57/1) 
Sea-Bird SBE4C Conductivity Sensor              S/N 04-2319 (Secondary 58/1-88/1)
Sea-Bird SBE43 DO Sensor                        S/N 43-0255
Wetlabs C-Star Transmissometer                  S/N 507DR
Seapoint Sensors Fluorometer                    S/N 2273
Simrad 1007 Altimeter                           S/N 0201075
RDI Workhorse 300khz LADCP                      S/N 3898-XR
RDI Workhorse 300khz LADCP                      S/N 3898-VXR
RDI Workhorse 300khz LADCP                      S/N 149
RDI Workhorse 300khz LADCP                      S/N 150
RDI Workhorse 300khz LADCP                      S/N 754
RDI Broadband 150khz LADCP                      S/N 1546
LADCP Battery Pack


The CTD was outfitted with dual pumps.  Primary temperature, conductivity and 
dissolved oxygen were plumbed on one pump circuit and secondary temperature 
and conductivity on the other.  The primary temperature and conductivity 
sensors (T1 #4138 and C1 #2419) were used for reported CTD temperatures and 
conductivities on casts 1/1 - 1/57.  The secondary temperature and 
conductivity sensors (T2 #2359 and C2 #2319) were used on casts 58/1 - 88/1.  

The SBE9 CTD and the SBE35RT Digital Reversing Thermometer were both connected 
to the SBE32 36-place pylon providing for single-conductor sea cable 
operation.  All 3 sea cable conductors were connected together to improve 
reliability.  Power to the SBE9 CTD, SBE32 pylon, and SBE35RT was provided 
through the sea cable from the SBE11plus deck unit in the main lab.  The 
Simrad altimeter and LADCP were powered by battery packs.  


1.4.  NAVIGATION AND BATHYMETRY DATA ACQUISITION

Navigation data were acquired (at 1-second intervals) from the ship's Seanav 
GPS receiver by one of the Linux workstations beginning September 22.  Data 
from the ship's Knudsen 320B/REchosounder (12 KHz transducer) were also 
acquired, corrected using Carter tables [Cart80] and merged with the 
navigation.  The Knudsen bathymetry data were noisy and subject to washing out 
on station when the bow thrusters were engaged.  

Bathymetric data from the ship's multibeam (SeaBeam) echosounder system were 
also logged by the R/V Knorr's underway system.  


1.5.  REAL-TIME CTD DATA ACQUISITION SYSTEM

The CTD data acquisition system consisted of an SBE-11plus deck unit and four 
networked generic PC workstations running RedHat 9 Linux.  Each PC workstation 
was configured with a color graphics display, keyboard, trackball, 60 GB disk, 
CD-R and CDRW drives.  Two of the four systems also had 8 additional RS-232 
ports via a Rocketport PCI serial controller.  The systems were networked 
through 2 100BaseTX ethernet switches which were also connected to the ship's 
network.  These systems were available for real-time operational and CTD data 
displays, as well as providing for CTD and hydrographic data management and 
backup.  Hardcopy capability was provided by a networked HP 1600CM color 
printer.  

One of the workstations was designated the CTD console and was connected to 
the CTD deck unit via RS-232.  The CTD console provided an interface for 
controlling CTD deployments as well as real-time operational displays for CTD 
and rosette trip data, GPS navigation, bathymetry and the CTD winch.  

CTD deployments were initiated by the console watch once the ship was stopped 
on station.  A console operations log was maintained by the watch containing a 
description of each deployment, a record of every attempt to close a bottle 
and any pertinent comments.  The deployment software presented the operator 
with a short dialog instructing them to turn on the deck unit, examine the on 
screen raw data display for stable CTD data and to notify the deck watch that 
this was accomplished.  When the deck watch was ready to put the rosette over 
the side, the console watch was notified and the CTD data acquisition started.  
Time, GPS position and bottom depth were automatically logged at 1 second 
resolution.  Both raw and processed (2 Hz time-series) CTD data were 
automatically backed up by one of the other workstations via ethernet.  The 
deployment software display changed to indicate that a cast was in progress.  
A processed data display appeared, as did a rosette bottle trip display and 
control for closing bottles.  Various real-time plots were then initiated to 
display the progress of the deployment.  

Once the deck watch had deployed the rosette, the winch operator would 
immediately lower it to 10 meters.  The CTD pumps were configured with an 8 
second startup delay, and would be on by this time.  

The console operator would check the CTD data for proper operation, then 
instruct the winch operator to bring the package to the surface and then 
descend to a target depth (wire-out).  The lowering rate was normally 60 
meters/minute for this package, depending on sea cable tension and sea state.  

The console watch monitored the progress of the deployment and quality of the 
CTD data through interactive graphics and operational displays.  Additionally, 
the watch decided where to trip bottles on the up cast, noting this on the 
console log.  The altimeter channel, CTD depth, wire-out and bathymetric depth 
were monitored to determine the distance of the package from the bottom.  The 
on-screen winch and altimeter displays allowed the watch to refine the target 
wire-out relayed to the winch operator and safely approach to within 10-20 
meters of the bottom.  

Bottles were closed on the up cast by operating a "point and click" graphical 
trip control button.  The data acquisition system responded with trip 
confirmation messages and the corresponding CTD data in a rosette bottle trip 
window on the display.  All tripping attempts were noted on the console log.  
The console watch then directed the winch operator to raise the package up to 
the next bottle trip location.  

The console watch was also responsible for creating a sample log for the 
deployment which was used to record the correspondence between rosette bottles 
and analytical samples taken.  

After the last bottle was tripped, the console watch directed the deck watch 
to bring the rosette on deck.  

Once on deck, the console watch terminated the data acquisition, turned off 
the deck unit and assisted with rosette sampling.  


1.6.  CTD DATA PROCESSING

ODF CTD processing software consists of over 30 programs running in a Unix 
run-time environment.  The initial CTD processing program (ctdr td/ctdba) is 
used either in real-time or with existing raw CTD data to:

   Convert raw CTD scans into scaled engineering units, and assign the data 
    to logical channels
   Filter various channels according to specified criteria
   Apply sensor- or instrument-specific response-correction models
   Decimate the channels according to specified criteria
   Store the output time-series in a CTD-independent format

Once the CTD data are reduced to a standard format time-series, they can be 
manipulated in various ways.  Channels can be additionally filtered.  The 
time-series can be split up into shorter time-series or pasted together to 
form longer time-series.  Atime-series can be transformed into a pressure-
series, or into a larger-interval time-series.  The pressure, temperature and 
conductivity laboratory calibration coefficients are applied during the 
creation of the initial time-series.  Oxygen conversion equation coefficients 
and any adjustments to pressure, temperature or conductivity are maintained in 
separate files and are applied whenever the data are accessed.  

The CTD data acquisition software acquired and processed the data in real-
time, providing calibrated, processed data for interactive plotting and 
reporting during a cast.  The 24 Hz data from the CTD were filtered, response-
corrected and decimated to a 2.0 Hz time-series.  Sensor correction and 
calibration models were applied to pressure, temperature, conductivity and O2.  
Rosette trip data were extracted from this time-series in response to trip 
initiation and confirmation signals.  The calibrated 2.0 Hz time-series data, 
as well as the 24 Hz raw data, were stored on disk and were backed up via 
ethernet to a second system.  At the end of the cast, various consistency and 
calibration checks were performed, and a 2-db pressure-series of the down cast 
was generated and subsequently used for reports and plots.  

CTD data were examined graphically at the completion of deployment for 
potential problems.  The two CTD temperature sensors were compared, 
intercompared with the SBE35RT Digital Reversing Thermometer and checked for 
sensor drift.  CTD conductivity sensors were compared and monitored by 
examining differences between CTD values and check-sample conductivities.  
Additionally, deep theta-salinity comparisons were made between down and up 
casts as well as adjacent deployments.  The CTD O2 sensor data were calibrated 
to bottle check-sample data.  

The sea cable/winch problems on this cruise did not significantly affect the 
CTD data, any noise being filtered out during the data acquisition.  No 
additional filtering was done on any of the CTD data.  

The initial 10 M yo in each deployment resulting from lowering then raising 
the package to the surface to start the pumps was removed during the 
generation of the 2.0 db pressure-series.  

Density inversions can be induced in high-gradient regions by ship-generated 
vertical motion of the rosette.  Detailed examination of the raw data shows 
significant mixing can occur in these areas because of "ship roll".  To 
minimize density inversions, a "ship-roll" filter which disallowed pressure 
reversals was applied during the generation of all 2.0 db pressure-series 
down-cast data.  


1.7.  CTD LABORATORY CALIBRATION PROCEDURES

Laboratory calibrations of the CTD pressure, temperature and conductivity 
sensors were used to generate Sea-Bird conversion equation coefficients 
applied by the data acquisition software at sea.  

Pressure calibrations were last performed on CTD #474 at the ODF Calibration 
Facility (La Jolla) 26 August 2003, immediately prior to A20_2003a.  

The Paroscientific Digiquartz pressure transducer (S/N 69008) was calibrated in 
    a temperature-controlled water bath to a Ruska Model 2400 Piston Gauge 
    Pressure Reference. Calibration curves were measured at 4 temperatures from 
    -1.38 to 29.30C to two maximum loading pressures (1191 and 6081 decibars). 

The SBE3plus temperature sensors (primary S/N 03-4138, secondary S/N 03-2359) 
    were calibrated at SBE on 08 August 2003. 

The SBE4 conductivity sensors (primary S/N 04-2419, secondaries S/Ns 04-1908, 
    04-2572 and 04-2319) were calibrated on 08 August 2003, 08 August 2003, 08 
    August 2003 and 03 May 2003 at SBE respectively. 

The SBE35RT Digital Reversing Thermometer (S/N 0034) was calibrated on 05 April 
    2002 at SBE.  

Laboratory pressure, temperature and conductivity calibrations will be 
repeated post-cruise.  


1.8.  CTD SHIPBOARD CALIBRATION PROCEDURES 

CTD #474 was used for all A20_2003a casts.  Secondary temperature and 
conductivity sensors served as calibration checks for the primary temperature 
and conductivity on casts 1/1-57/1, and were used for reported data (the 
primary temperature and conductivity sensors serving as calibration checks) on 
casts 58/1 - 88/1.  The SBE35RT Digital Reversing Thermometer served as an 
independent temperature calibration check.  In-situ salinity and dissolved O2 
check samples collected during each rosette cast were used to calibrate CTD 
conductivity and dissolved O2.  


1.8.1.  CTD PRESSURE

Pressure sensor conversion equation coefficients derived from the pre-cruise 
pressure calibration were applied to raw pressures during each cast.  No 
additional adjustments were made to the calculated pressures, but the pressure 
was lagged (tc=1.4 secs) on casts 1/1 - 57/1 to better match the T1/C1 
response due to pump alignment problems.  

Residual offsets at the beginning and end of each cast (the difference between 
the first/last pressures in-water and 0) were monitored during the cruise to 
check for shifts in the pressure calibration.  All residual differences were 
0.5 decibar or less.  There was no apparent shift in pressure calibration 
during the cruise.  This will be verified by a post-cruise laboratory pressure 
calibration.  


1.8.2.  CTD TEMPERATURE

Temperature sensor calibration coefficients were derived from the pre-cruise 
calibrations and applied to raw primary and secondary temperatures.  

Two independent metrics of calibration accuracy were examined.  The primary 
and secondary temperatures were compared at each rosette trip, and the SBE35RT 
and primary temperatures were compared at each rosette trip.  These 
comparisons are summarized in figures 1.8.2.0 and 1.8.2.1.  


FIGURE 1.8.2.0:  Primary and secondary temperature comparison, p>1000db.


The comparison between primary and secondary temperatures shows a small 
(0.00011C) mean calibration offset, well within the reported accuracy of the 
SBE temperature calibrations.


FIGURE 1.8.2.1:  Primary and SBE35RT temperature comparison, p>1000db.


The comparison between SBE35RT and T1 temperatures shows a distinct linear 
trend as well as a mean difference of -0.00098C.  Given the age of the SBE35 
calibration (05 April 2002) and the unlikelihood that both T1 and T2 would 
track so closely if they were both drifting, these differences are attributed 
to the SBE35RT.


1.8.3.  CTD CONDUCTIVITY

Conductivity sensor conversion equation coefficients were derived from the 
pre-cruise calibrations and applied to raw primary and secondary 
conductivities.  

Three secondary conductivity sensors were used on A20: #1908 (1/1 - 17/1), 
#2572 (18/1 - 57/01) and #2319 (58/1 - 88/1).  The first two secondary sensors 
were replaced because of excessive noise and drift.  

The third sensor was stable.  Prior to cast 58/1 C1-C2 conductivity 
differences were not a useful metric of calibration accuracy.  

The primary conductivity sensor (#2419) was fairly stable and noise-free.  
Comparisons to bottle salinities showed a mean conductivity correction slope 
of -0.000309376 and well-behaved offset groupings.  The conductivity 
correction offsets are summarized in figure 1.8.3.0.  


FIGURE 1.8.3.0:  Primary conductivity correction offsets.  


Comparisons of the stable secondary conductivity sensor (#2319) to bottle 
salinities showed no significant conductivity correction slope and a minor 
constant offset of 0.00021 mS/cm.  

A systematic uniform offset of 0.0015 PSU between downcast and upcast C1 
salinities was observed prior to cast 58/1.  This was attributed to the sensor 
and pump configuration (horizontal) and the location of the P1 pump exhaust 
port (30 from vertical, per SBE specs).  Both P1 and P2 pumps were rotated 
so that the exhaust ports were aligned horizontally and the C1 salinity offset 
was reduced to 0.0007 PSU.  

C2 exhibited almost no offset.  This discrepancy was perhaps due to the 
inclusion of the SBE43 DO sensor in the P1 circuit.  As a result of this 
experiment, T2 and C2 were used for reported salinities and temperatures on 
casts 58/1 - 88/1.  Correcting T1/C1 salinities for casts 1/1 - 57/1 was done 
by applying a lag (tc=1.4 seconds) to pressure.  

The salinity residuals after applying the shipboard calibration are summarized 
in figures 1.8.3.1 and 1.8.3.2.  


FIGURE 1.8.3.1:  C1 and C2 salinity residuals by pressure, p>500db.  
FIGURE 1.8.3.2:  C1 and C2 salinity residuals by station,  p>500db.  
FIGURE 1.8.3.3:  C1 and C2 salinity residuals by station,  p>2000db.  


Excluding thermocline and gradient values (early and late stations were 
shallow and also excluded), figure 1.8.3.3 represents an estimate of the 
salinity accuracy of CTD #474.  The 95% confidence limit is 0.0019 PSU, in 
agreement with the generally accepted limit of repeatability for bottle 
salinities (0.002PSU).  


1.8.4.  CTD DISSOLVED OXYGEN

One SBE43 dissolved O2 (DO) sensor was used for this cruise (#43-0225).  The 
sensor was plumbed into the P1/T1/C1 intake line in a horizontal configuration 
after C1 and before P1 (per SBE spec).  

One characteristic of this type of sensor (membrane-covered polarigraphic 
oxygen detector or MPOD) is a flow dependence.  Non-pumped sensors of this 
type exhibit a significantly decreased response at bottle stops.  The pumped 
SBE43 reduces but does not eliminate this problem, perhaps due to pump or flow 
rate variations in the primary sensor circuit.  DO sensor calibration to check 
samples is somewhat problematic as sensor data from the bottle stop does not 
provide a representative comparison.  

The DO sensor calibration method used for this cruise was to match down-cast 
CTD DO data to up-cast bottle trips along isopycnal surfaces, then to minimize 
the residual differences between the in-situ check sample values and CTD O2 
using a non-linear least-squares fitting procedure.  Since this technique only 
calibrates the down-cast, only the 2.0 pressure series downcast data contain 
calibrated CTD O2.  

A small (<0.02 ml/l) but significant non-linearity apparent in the O2 
residuals as a function of pressure was corrected with an additional empirical 
4th-order polynomial pressure correction.  The explanation for this non-
linearity requires further investigation.  

Figures 1.8.4.0, 1.8.4.1 and 1.8.4.2 show the residual differences between 
bottle and calibrated CTD O2 for all points excluding the thermocline and 
surface gradients.  Figure 1.8.4.3 shows the residual differences for 
pressures >1000 db.  


FIGURE 1.8.4.0:  O2 residuals by station number.  
FIGURE 1.8.4.1:  O2 residuals by pressure.  
FIGURE 1.8.4.2:  O2 residuals by temperature.  
FIGURE 1.8.4.3:  O2 residuals by station number, p>1000db .  


The standard deviations of 0.050 ml/l for all oxygens and 0.027 ml/l for deep 
oxygens are only intended as indicators of how well the up-cast bottle O2 and 
down-cast CTD O2 match.  ODF makes no claims regarding the precision or 
accuracy of CTD dissolved O2 data.  

The general form of the ODF O2 conversion equation follows Brown and Morrison 
[Brow78] and Millard [Mill82], [Owen85].  ODF models membrane and sensor 
temperatures with lagged CTD temperatures.  In-situ pressure and temperature 
are filtered to match the sensor response.  Time-constants for the pressure 
response tp, and two temperature responses tTs and tTf are fitting parameters.  
The Oc gradient, dOc/dt, is approximated by low-pass filtering 1st-order Oc 
differences.  This gradient term attempts to correct for reduction of species 
other than O2 at the sensor cathode.  The time-constant for this filter, tog, 
is afitting parameter.  Oxygen partial-pressure is then calculated:


                                      (c3 Pl +c4 Tf +c5 Ts +c6 dOcdt)
Opp = [c1 Oc + c2 ]  fsat (S,T,P)  e                                          (1.8.4.0)

where:

    Opp =           Dissolved O2 partial-pressure in atmospheres (atm);
    Oc =            Sensor current (mamps);
    f sat (S,T,P) = O2 saturation partial-pressure at S, T, P (atm);
    S =             Salinity at O2 response-time (PSUs);
    T =             Temperature at O2 response-time (C);
    P =             Pressure at O2 response-time (decibars);
    Pl =            Low-pass filtered pressure (decibars);
    Tf =            Fast low-pass filtered temperature (C);
    Ts =            Slow low-pass filtered temperature (C);
    dOc
    --- =           Sensor current gradient (mamps/secs).
    dt 


1.9.  BOTTLE SAMPLING

At the end of each rosette deployment water samples were drawn from the 
bottles in the following order:

   CFCs
   O2
   He3
   DIC/Total Alkalinity
   DOC/DON/DCNS/CDOM
   Tritium
   I129
   C13 and C14
   Nutrients
   Salinity

The correspondence between individual sample containers and the rosette bottle 
from which the sample was drawn was recorded on the sample log for the cast.  
This log also included any comments or anomalous conditions noted about the 
rosette and bottles.  One member of the sampling team was designated the 
sample cop, whose sole responsibility was to maintain this log and insure that 
sampling progressed in the proper drawing order.  

Normal sampling practice included opening the drain valve and then the air 
vent on the bottle, indicating an air leak if water escaped.  This observation 
together with other diagnostic comments (e.g., "lanyard caught in lid", "valve 
left open") that might later prove useful in determining sample integrity were 
routinely noted on the sample log.  Drawing oxygen samples also involved 
taking the sample draw temperature from the bottle.  The temperature was noted 
on the sample log and was sometimes useful in determining leaking or mis-
tripped bottles.  

Once individual samples had been drawn and properly prepared, they were 
distributed for analysis.  

Oxygen, nutrient and salinity analyses were performed on computer-assisted 
(PC) analytical equipment networked to the data processing computer for 
centralized data analysis.  


1.10.  BOTTLE DATA PROCESSING

Bottle data processing began with sample drawing, and continued iteratively 
until the data were considered to be problem-free.  One of the most important 
pieces of information, the sample log sheet, was filled out during sample 
drawing and served both as a sample inventory and as a guide for the 
technicians in carrying out their analyses.  Any problems observed with the 
rosette before or during the sample drawing were noted on this form, including 
indications of bottle leaks, out-of-order drawing, etc.  Additional clues 
regarding bottle tripping or leak problems were found by individual analysts 
as the samples were analyzed and the resulting data processed and checked.  

The next stage of processing began after individual analyses were associated 
with rosette bottles and their CTD-derived parameters (pressure, temperature, 
conductivity, etc.).  The rosette cast and bottle numbers were the primary 
identification for all ODF-analyzed samples taken from the bottle.  At this 
stage, bottle tripping problems were usually identified and resolved, 
sometimes resulting in changes to the pressure, temperature and other CTD 
properties associated with the bottle.  All CTD information for each bottle 
trip (confirmed or not) was retained, so resolving bottle tripping problems 
consisted of correlating CTD trip data with the rosette bottles.  

Diagnostic comments from the sample log, and notes from analysts and data 
processors were associated with each deployment as part of the quality control 
procedure.  Sample data from bottles suspected of leaking were checked to see 
if the properties were consistent with the CTD profile and with adjacent 
stations.  The analysts reviewed and sometimes revised their data as 
additional calibration or diagnostic results became available.  

Quality coding of CTD and water samples was done using a coding scheme 
developed for the World Ocean Circulation Experiment (WOCE) Hydrographic 
Programme (WHP) [Joyc94].  Based on the outcome of investigations of the 
various comments in the quality files, WHP water sample codes were selected to 
indicate the reliability of the individual parameters affected by the 
comments.  WHP bottle codes were assigned where evidence showed the entire 
bottle was affected, as in the case of a leak, or a bottle trip at other than 
the intended depth.  


WHP WATER BOTTLE QUALITY CODES WERE ASSIGNED AS DEFINED IN THE WOCE OPERATIONS 
MANUAL [JOYC94] WITH THE FOLLOWING ADDITIONAL INTERPRETATIONS:

2 | No problems noted.  
  |
3 | Leaking.                   An air leak large enough to produce an 
  |                            observable effect on a sample is identified by a 
  |                            code of 3 on the bottle and a code of 4 on the 
  |                            oxygen.  (Small air leaks may have no observable 
  |                            effect, or may only affect gas samples.)
  |
4 | Did not trip correctly.    Bottles tripped at other than the intended depth 
  |                            were assigned a code of 4.  There may be no 
  |                            problems with the associated water sample data.  
  |
5 | Not reported.              No water sample data reported.  This is a 
  |                            representative level derived from the CTD data 
  |                            for reporting purposes.  The sample number 
  |                            should be in the range of 80-99.  
  |
9 | The samples were not drawn from this bottle.  


WHP WATER SAMPLE QUALITY FLAGS WERE ASSIGNED USING THE FOLLOWING CRITERIA:

1 | The sample for this measurement was drawn from the water bottle, but the 
  |                            results of the analysis were not (yet) received.  
  |
2 | Acceptable measurement.  
  |
3 | Questionable measurement.  The data did not fit the station profile or 
  |                            adjacent station comparisons (or possibly CTD 
  |                            data comparisons).  No notes from the analyst 
  |                            indicated a problem.  The data could be 
  |                            acceptable, but are open to interpretation.  
  |
4 | Bad measurement.           The data did not fit the station profile, 
  |                            adjacent stations or CTD data.  There were 
  |                            analytical notes indicating a problem, but data 
  |                            values were reported.  Sampling and analytical 
  |                            errors were also coded as 4.  
  |
5 | Not reported.              There should always be a reason associated with 
  |                            a code of 5, usually that the sample was lost, 
  |                            contaminated or rendered unusable.  
  |
9 |                            The sample for this measurement was not drawn.  


WHP WATER SAMPLE QUALITY FLAGS WERE ASSIGNED TO THE CTDSAL (CTD SALINITY) 
PARAMETER AS FOLLOWS:

2 | Acceptable measurement.  
  |
3 | Questionable measurement.  The data did not fit the bottle data, or there 
  |                            was a CTD conductivity calibration shift during 
  |                            the up-cast.  
  |
4 | Bad measurement.           The CTD up-cast data were determined to be 
  |                            unusable for calculating a salinity.  
  |
7 | Despiked.                  The CTD data have been filtered to eliminate a 
  |                            spike or offset.  


WHP WATER SAMPLE QUALITY FLAGS WERE ASSIGNED TO THE CTDOXY (CTD O2)PARAMETER 
AS FOLLOWS:

1 | Not calibrated.            Data are uncalibrated.  
  |
2 | Acceptable measurement.  
  |
3 | Questionable measurement.  
  |
4 | Bad measurement.           The CTD data were determined to be unusable for 
  |                            calculating a dissolved oxygen concentration.  
  |
5 | Not reported.              The CTD data could not be reported, typically 
  |                            when CTD salinity is coded 3 or 4.  
  |
7 | Despiked.                  The CTD data have been filtered to eliminate a 
  |                            spike or offset.  
  |
9 | Not sampled.               No operational CTD O2 sensor was present on this 
  |                            cast.  Note that CTDOXY values were derived from 
  |                            the down-cast pressure-series CTD data and 
  |                            matched to the up-cast bottle data along 
  |                            isopycnal surfaces.  If the CTD salinity is 
  |                            footnoted as bad or questionable, the CTD O2 is 
  |                            not reported.  


1.11.  SALINITY ANALYSIS

EQUIPMENT AND TECHNIQUES

Two Guildline Autosal Model 8400A salinometers (S/N 57-263 and 57-266) located 
in the forward analytical lab were used for measuring salinity on all stations 
(57-263: 1/1 - 1/8, 11/1 - 30/1, 53/1 - 59/1; 57 - 266: 10/1, 31/1 - 52/1, 
60/1 - 88/1).  The salinometers were modified by ODF to contain an interface 
for computer-aided measurement.  The water bath temperatures were set and 
maintained at a value near the laboratory air temperature.  They were set at 
24C for the entire leg.  

The salinity analyses were performed after samples had equilibrated to 
laboratory temperature, usually within 16-36 hours after collection.  A 
temperature-controlled waterbath was used to assist sample equilibration.  The 
salinometer was standardized for each group of analyses (1-7 casts, up to ~50 
samples) using at least one fresh vial of standard seawater per group.  A 
computer (PC) prompted the analyst for control functions such as changing 
sample, flushing, or switching to "read" mode.  The salinometer cell was 
flushed and results were logged by the computer until two successive 
measurements met software criteria for consistency.  These values were then 
averaged for a final result.  

Sampling and Data Processing Salinity samples were drawn into 200 ml Kimax 
high-alumina borosilicate bottles, which were rinsed three times with sample 
prior to filling.  The bottles were sealed with custom-made plastic insert 
thimbles and Nalgene screw caps.  This assembly provides very low container 
dissolution and sample evaporation.  

Prior to collecting each sample, inserts were inspected for proper fit and 
loose inserts were replaced to insure an airtight seal.  The draw time and 
equilibration time were logged for all casts.  Laboratory temperatures were 
logged at the beginning and end of each run.  

PSS-78 salinity [UNES81] was calculated for each sample from the measured 
conductivity ratios.  The difference (if any) between the initial vial of 
standard water and one run at the end as an unknown was applied linearly to 
the data to account for any drift.  The data were incorporated into the cruise 
database.  

2530 salinity measurements were made and approximately 60 vials of standard 
water were used.  The estimated accuracy of bottle salinities run at sea is 
usually better than 0.002 PSU relative to the particular standard seawater 
batch used.  

LABORATORY TEMPERATURE

The temperature in the salinometer laboratory varied from 20.9 to 25.8C, 
during the cruise.  The air temperature change during any single run of 
samples was less than 1.2C.  Standards IAPSO Standard Seawater (SSW) Batches 
P-140 and P-141 were used to standardize all salinity measurements.  


1.12.  OXYGEN ANALYSIS

EQUIPMENT AND TECHNIQUES

Dissolved oxygen analyses were performed with an ODF-designed automated oxygen 
titrator using photometric end-point detection based on the absorption of 
365nm wavelength ultra-violet light.  The titration of the samples and the 
data logging were controlled by PC software.  Thiosulfate was dispensed by a 
Dosimat 665 buret driver fitted with a 1.0 ml buret.  ODF used a whole-bottle 
modified-Winkler titration following the technique of Carpenter [Carp65] with 
modifications by Culberson et al. [Culb91], but with higher concentrations of 
potassium iodate standard (~0.012N) and thiosulfate solution (~65 gm/l).  

Pre-made liquid potassium iodate standards were run at the beginning of each 
session of analyses, which typically included from 1 to 3 stations.  
Reagent/distilled water blanks were determined every other day or more often 
if a change in reagents required it to account for presence of oxidizing or 
reducing agents.  

The auto-titrator generally performed well.  A leak in the thiosulfate 
delivery tubing affected samples on 26/1 - 28/1, 30/1, 32/1 - 33/1 and 38/1.  

SAMPLING AND DATA PROCESSING

Samples were collected for dissolved oxygen analyses soon after the rosette 
was brought on board.  

Using a Tygon and silicone drawing tube, nominal 125ml volume-calibrated 
iodine flasks were rinsed 3 times with minimal agitation, then filled and 
allowed to overflow for at least 3 flask volumes.  The sample draw temperature 
was measured with a small platinum resistance thermometer embedded in the 
drawing tube.  Reagents were added to fix the oxygen before stoppering.  The 
flasks were shaken twice (10-12 inversions) to assure thorough dispersion of 
the precipitate, once immediately after drawing, and then again after about 20 
minutes.  

The samples were analyzed within 1-6 hours of collection, then the data were 
incorporated into the cruise database.  

Thiosulfate normalities were calculated from each standardization and 
corrected to 20C.  The 20C normalities and the blanks were plotted versus 
time and were reviewed for possible problems.  

As samples warmed up to room temperature they would occasionally degas which 
would cause a noisy endpoint due to gas bubbles in the light path.  2503 
oxygen measurements were made.  

The blank volumes and thiosulfate normalities were smoothed (linear fits) at 
the end of the cruise and the oxygen values recalculated.  

VOLUMETRIC CALIBRATION

Oxygen flask volumes were determined gravimetrically with degassed deionized 
water to determine flask volumes at ODF's chemistry laboratory.  This is done 
once before using flasks for the first time and periodically thereafter when a 
suspect bottle volume is detected.  The volumetric flasks used in preparing 
standards were volume-calibrated by the same method, as was the 10 ml Dosimat 
buret used to dispense standard iodate solution.  

STANDARDS

Liquid potassium iodate standards were prepared and bottled in ODF's chemistry 
laboratory prior to the cruise.  The normality of the liquid standard was 
determined at ODF by calculation from weight.  A single standard batch was 
used during A20_2003a.  Potassium iodate was obtained from Acros Chemical Co.  
and was reported by the supplier to be >99.4% pure.  All other reagents were 
"reagent grade" and were tested for levels of oxidizing and reducing 
impurities prior to use.  


1.13.  NUTRIENT ANALYSIS

EQUIPMENT AND TECHNIQUES

Nutrient analyses (phosphate, silicate, nitrate and nitrite) were performed on 
an ODF-modified 4-channel Technicon AutoAnalyzer II, generally within one hour 
after sample collection.  Occasionally samples were refrigerated up to 4 hours 
at ~4C.  All samples were brought to room temperature prior to analysis.  

The methods used are described by Gordon et al. [Gord92].  The analog outputs 
from each of the four colorimeter channels were digitized and logged 
automatically by computer (PC) at 2-second intervals.  

Silicate was analyzed using the technique of Armstrong et al. [Arms67].  An 
acidic solution of ammonium molybdate was added to a seawater sample to 
produce silicomolybdic acid which was then reduced to silicomolybdous acid (a 
blue compound) following the addition of stannous chloride.  Tartaric acid was 
also added to impede PO4 color development.  The sample was passed through a 
15mm flowcell and the absorbance measured at 660nm.  

A modification of the Armstrong et al. [Arms67] procedure was used for the 
analysis of nitrate and nitrite.  

For the nitrate analysis, the seawater sample was passed through a cadmium 
reduction column where nitrate was quantitatively reduced to nitrite.  
Sulfanilamide was introduced to the sample stream followed by N-(1-
naphthyl)ethylenediamine dihydrochloride which coupled to form a red azo dye.  
The stream was then passed through a 15mm flowcell and the absorbance measured 
at 540nm.  The same technique was employed for nitrite analysis, except the 
cadmium column was bypassed, and a 50mm flowcell was used for measurement.  

Phosphate was analyzed using a modification of the Bernhardt and Wilhelms 
[Bern67] technique.  An acidic solution of ammonium molybdate was added to the 
sample to produce phosphomolybdic acid, then reduced to phosphomolybdous acid 
(a blue compound) following the addition of dihydrazine sulfate.  The reaction 
product was heated to ~55C to enhance color development, then passed through 
a 50mm flowcell and the absorbance measured at 820nm.  

Sampling and Data Processing Nutrient samples were drawn into 45 ml 
polypropylene, screw-capped "oak-ridge type" centrifuge tubes.  

The tubes were cleaned with 10% HCl and rinsed with sample 2-3 times before 
filling.  Standardizations were performed at the beginning and end of each 
group of analyses (typically one cast, up to 36 samples) with an intermediate 
concentration mixed nutrient standard prepared prior to each run from a 
secondary standard in a low-nutrient seawater matrix.  The secondary standards 
were prepared aboard ship by dilution from primary standard solutions.  Dry 
standards were pre-weighed at the laboratory at ODF, and transported to the 
vessel for dilution to the primary standard.  Sets of 6-7 different standard 
concentrations were analyzed periodically to determine any deviation from 
linearity as a function of concentration for each nutrient analysis.  
Acorrection for non-linearity was applied to the final nutrient concentrations 
when necessary.  

After each group of samples was analyzed, the raw data file was processed to 
produce another file of response factors, baseline values, and absorbances.  
Computer-produced absorbance readings were checked for accuracy against values 
taken from a strip chart recording.  The data were then added to the cruise 
database.  

Nutrients, reported in micromoles per kilogram, were converted from micromoles 
per liter by dividing by sample density calculated at 1 atm pressure (0 db), 
in situ salinity, and an assumed laboratory temperature of 25C.  

2540 nutrient samples were analyzed.  The pump tubing was changed 2 times.  

STANDARDS

Primary standards for silicate (Na2 SiF6)and nitrite (NaNO2)were obtained from 
Johnson Matthey Chemical Co.; the supplier reported purities of >98% and 97%, 
respectively.  Primary standards for nitrate (KNO3)and phosphate (KH2 PO4)were 
obtained from Fisher Chemical Co.; the supplier reported purities of 99.999% 
and 99.999%, respectively.  The efficiency of the cadmium column used for 
nitrate was monitored throughout the cruise and ranged from 99-100%.  

No major problems were encountered with the measurements.  The temperature of 
the laboratory used for the analyses ranged from 20.9C to 25.5C, but was 
relatively constant during any one station (1.5C).  



REFERENCES

Arms67. 
    Armstrong, F.A.J., C.R. Stearns and J.D.H. Strickland, "The measurement 
    of upwelling and subsequent biological processes by means of the Technicon 
    Autoanalyzer and associated equipment"  Deep-Sea Research, 14, pp. 381-389 
    (1967). 

Bern67. 
    Bernhardt, H. and A. Wilhelms, "The continuous determination of low level 
    iron, soluble phosphate and total phosphate with the AutoAnalyzer"  
    Technicon Symposia, I, pp. 385-389 (1967). 

Brow78. 
    Brown, N.L. and G.K. Morrison, "WHOI/Brown conductivity, temperature and 
    depth microprofiler"  Technical Report No. 78-23, Woods Hole Oceanographic 
    Institution (1978). 

Carp65. 
    Carpenter, J.H., "The Chesapeake Bay Institute technique for the Winkler 
    dissolved oxygen method"  Limnology and Oceanography, 10, pp. 141-143 

Cart80. 
    Carter, D.J.T., "Computerised Version of Echo-sounding Correction Tables 
    (Third Edition)"  Marine Information and Advisory Service, Institute of 
    Oceanographic Sciences, Wormley, Godalming, Surrey. GU8 5UB. U.K. (1980). 

Culb91. 
    Culberson, C.H., G. Knapp, M.Stalcup, R.T. Williams, and F.Zemlyak, "A 
    comparison of methods for the determination of dissolved oxygen in 
    seawater"  Report WHPO 91-2, WOCE Hydrographic Programme Office (Aug 1991).

Gord92.
    Gordon, L.I., J.C. Jennings-Jr., A.A. Ross, and J.M. Krest, "A suggested 
    Protocol for Continuous Flow Automated Analysis of Seawater Nutrients in the 
    WOCE Hydrographic Program and the Joint Global Ocean Fluxes Study"  Grp. 
    Tech Rpt 92-1, OSU College of Oceanography Descr. Chem Oc. (1992). 

Joyc94. 
    Joyce, T., ed. and C. Corry, ed., "Requirements for WOCE Hydrographic 
    Programme Data Reporting"  Report WHPO 90-1, WOCE Report No. 67/91, pp. 52-
    55, WOCE Hydrographic Programme Office, Woods Hole, MA, USA (May 1994, Rev. 
    2). UNPUBLISHED MANUSCRIPT. 

Mill82. 
    Millard-Jr., R.C., "CTD calibration and data processing techniques at WHOI 
    using the practical salinity scale"  Proc. Int. STD Conference and 
    Workshop, p.19, Mar. Tech. Soc., La Jolla, Ca. (1982).

Owen85.
    Owens, W.B. and R.C.,Millard-Jr., "A new algorithm for CTD oxygen 
    calibration"  Journ. of Am. Meteorological Soc., 15, p.621 (1985).

UNES81.
    UNESCO, "Background papers and supporting data on the Practical Salinity 
    Scale, 1978"  UNESCO Technical Papers in Marine Science, No. 37, p. 144 
    (1981). 


2.  LADCP

Lowered Acoustic Doppler Current Profiler Velocity profiles were obtained during 
the standard hydrographic casts of the Knorr A20 cruise using self contained 
ADCPs (Acoustic Doppler Current Profilers) attached to the CTD rosette. Dual 
WH300 ADCPs (RDI Instruments Inc.) were used for Stations 1 through 37 and the 
test station 999. A single broadband 150 khz ADCP (RDI Instruments Inc.) was 
used for stations 38 through 84. Lowered ADCP data for stations 85 through 88 
was not collected given that these stations were too shallow to obtain 
meaningful information. An experimental high power version of the WH300 ADCP was 
used on casts 1-11 and initially exhibited promising (higher range) results. 
Unfortunately a failed transducer on that instrument required that it be 
replaced with a standard WH300 ADCP for subsequent casts. 

Based on the instrument range and the magnitude of the error associated with 
the velocity estimates, the dual WH300 ADCPs performed well in the high back-
scatter region on the northern portion of the transect.  The range of these 
instruments declined steadily and the velocity error increased as the ship 
proceeded south into lower back-scatter waters, requiring the switch to the 
higher powered broadband 150 khz instrument after station 37.  While the 
performance of the broadband 150 khz instrument was adequate in the low back-
scatter waters of the main gyre, the range and velocity error steadily 
improved as the ship made progress south.  Poor velocity estimates in the 
upper 200 meters of the water column is common when profiling with a single 
ADCP and is not entirely understood.  This proved to be the case when the 
single BB150 ADCP was used during this cruise.  The hull mounted ADCP data 
will be used to fill in for the poor surface data that was obtained while 
using the single BB150 ADCP.  Additional post processing will be done to 
optimize the threshold settings that will allow our bottom tracking routines 
to decrease the error in the velocity estimates when the paired WH300 ADCPs 
were used.  However, preliminary examination of the velocity profiles 
indicates good correlation with the geostrophic velocities computed from the 
temperature and salinity data.  



3.  CHROMOPHORIC DOM

Our goals are to determine chromophoric dissolved matter (CDOM) distributions 
over a range of oceanic regimes on meridional sections of the CO2/CLIVAR 
Repeat Hydrography survey, and: to quantify and parameter ize CDOM production 
and destruction processes with the goal of mathematically constraining the 
cycling of CDOM.  CDOM is a poorly characterized organic matter pool that 
interacts with sunlight, leading to the production of climate-relevant trace 
gases, attenuation of solar ultraviolet radiation in the water column, and an 
impact upon ocean color that can be quantified using satellite imagery.  We 
believe that the global distribution of CDOM in the open ocean is controlled 
by microbial production and solar bleaching in the upper water column.  We are 
testing these hypotheses by a combination of field observation and controlled 
experiments.  We are also interested in the deep-sea reservoir of CDOM and its 
origin and connection to surface waters and are making the first large-scale 
survey of the abundance of CDOM in the deep ocean.  


3.1.  ACTIVITIES ON A20 AND A22:

We are collecting samples of seawater for absorption spectroscopy on one deep 
ocean cast (24 depths) each day.  CDOM is typically quantified as the 
absorption coefficient at a particular wavelength or wavelength range (we are 
using 325 nm).  We determine CDOM at sea by measuring absorption spectra (280-
730 nm) of 0.2um filtrates using a liquid waveguide spectrophotometer with a 
200cm cell.  We are concurrently collecting samples for bacterial abundance, 
dissolved organic carbon, dissolved organic nitrogen (see below), and 
carbohydrates to compare the distribution of these quantities to that of CDOM.  

In surface waters (<300m) we are also estimating bacterial productivity of 
field samples by measuring the uptake of bromo-deoxyuridine (BRDU).  At 
selected stations (continental slope, subtropical, and tropical stations) we 
will collect extra seawater for a) microbial culture experiments and b) solar 
bleaching experiments.  In these experiments we will examine the rate of CDOM 
production relative to microbial productivity in culture, and quantify the 
rate of solar bleaching of CDOM near the surface.  Because of the connections 
to light availability and remote sensing, we are collecting samples for 
pigment analysis (HPLC), chlorophyll a (fluorometric), and particulate 
absorption (spectrophotometric) when possible.  We are also deploying a 
Satlantic free-fall profiling spectroradiometer (ca. once per day) to quantify 
the underwater light field, and we have a Satlantic surface irradiance meter 
continuously logging the solar spectrum during daylight hours.  Fluorometric 
analysis is being done at sea after 48 hour extractions.  

ALSO:

We are collecting samples for dissolved organic carbon and dissolved organic 
nitrogen analysis, which are a core part of the CO2/CLIVAR project.  The PIs 
for this part of the study are D. Hansell (U.Miami) and C. Carlson (UCSB), who 
can provide more details.  We are collecting and freezing approximately 150ml 
(each) from 24 depths on each A cast.  Samples in the upper 1000m are filtered 
(using GF/F glass fiber filters) at the time of collection.  These samples 
will be analyzed at UCSB after the end of the A22 leg.  



4.  DISSOLVED INORGANIC CARBON (DIC)

The DIC analytical equipment was set up in a seagoing container modified for 
use as a shipboard laboratory.  The analysis was done by coulometry with two 
analytical systems (PMEL-1 and PMEL-2) used simultaneously on the cruise.  
Each system consisted of a coulometer (UIC, Inc.) coupled with a SOMMA (Single 
Operator Multiparameter Metabolic Analyzer) inlet system developed by Ken 
Johnson (Johnson et al., 1985, 1987, 1993; Johnson, 1992) of Brookhaven 
National Laboratory (BNL).  In the coulometric analysis of DIC, all carbonate 
species are converted to CO2 (gas) by addition of excess hydrogen to the 
seawater sample, and the evolved CO2 gas is carried into the titration cell of 
the coulometer, where it reacts quantitatively with a proprietary reagent 
based on ethanolamine to generate hydrogen ions.  These are subsequently 
titrated with coulometrically generated OH-.  CO2 is thus measured by 
integrating the total change required to achieve this.  

The coulometers were each calibrated by injecting aliquots of pure CO2 
(99.995%) by means of an 8-port valve outfitted with two sample loops.  The 
instruments were calibrated at the beginning, middle, and end of each station 
with a set of the gas loop injections.  

Secondary standards were run throughout the cruise on each analytical system; 
these standards were Certified Reference Materials (CRMs) consisting of 
poisoned, filtered, and UV irradiated seawater supplied by Dr. A. Dickson of 
Scripps Institution of Oceanography (SIO), and were determined shoreside 
manometrically.  Despite equipment problems in the beginning of the cruise, 
the overall accuracy and precision for the CRMs on both instruments combined 
was 1.01.7 mol/kg respectively (n=88).  

Preliminary DIC data reported to the database have not yet been corrected to 
the Batch 61 CRM value, but a more careful quality assurance to be completed 
shoreside will have final data corrected to the secondary standard on a per 
instrument basis.  

Samples were drawn from the Niskin-type bottles into cleaned, precombusted 
500-mL Pyrex bottles using Tygon tubing.  Bottles were rinsed once and filled 
from the bottom, overflowing half a volume, and care was taken not to entrain 
any bubbles.  The tube was pinched off and withdrawn, creating a 5-mL 
headspace, and 0.2 mL of saturated HgCl2 solution was added as a preservative.  
The sample bottles were sealed with glass stoppers lightly covered with 
Apiezon-L grease, and were stored at room temperature for a maximum of 12 
hours prior to analysis.  

Over 1600 samples were analyzed for DIC; full profiles were completed at the 
'A' stations, with replicate samples taken from the surface, oxygen minimum, 
and bottom Niskin-type bottles.  At a minimum, replicate surface samples were 
taken at every 'B' stations, and when time permitted, additional depths to 
1000m were sampled.  The replicate samples were run at different times during 
the station analysis for quality assurance of the integrity of the coulometer 
cell solutions.  No systematic differences between the replicates were 
observed.  


REFERENCES: 

Johnson, K.M., A.E. King, and J.McN. Sieburth (1985): Coulometric DIC analyses 
    for marine studies: An introduction.  Mar. Chem., 16, 61-82.

Johnson, K.M., P.J. Williams, L. Brandstrom, and J.McN. Sieburth (1987): 
    Coulometric total carbon analysis for marine studies: Automation and 
    calibration.  Mar. Chem., 21, 117-133.

Johnson, K.M. (1992): Operator's manual: Single operator multiparameter 
    metabolic analyzer (SOMMA) for total carbon dioxide (CT) with coulometric 
    detection.  Brookhaven National Laboratory, Brookhaven, N.Y., 70 pp.

Johnson, K.M., K.D. Wills, D.B. Butler, W.K. Johnson, and C.S. Wong (1993): 
    Coulometric total carbon dioxide analysis for marine studies: Maximizing the 
    performance of an automated continuous gas extraction system and 
    coulometric detector.  Mar. Chem., 44, 167-189.

Wilke, R.J., D.W.R. Wallace, and K.M. Johnson (1993): Water-based gravimetric 
    method for the determination of gas loop volume.  Anal. Chem. 65, 2403-2406.  



5.  ARGO FLOAT DEPLOYMENTS

At the request of Dr. Allyn Clarke of the Bedford Institute of Oceanography, 
five free-drifting, profiling floats were launched during the 2003 A20 
occupation.  A total of eight Metocean Provor floats were shipped to Woods 
Hole one week prior to our departure.  ABIO technician, Murray XXXX traveled 
to WHOI and initiated the floats' operation program.  A subset of 5 of these 
were deployed on A20; the others are to be launched during A22.  
Operationally, the units were activiated during the up-cast of pre-selected 
stations by the removal of a magnet from the instrument pressure vessel.  
Then, as the R/V Knorr began to move off the station, the float was lowered 
into the sea using a slip line off the vessel stern.  Though awkward to carry 
out given the Knorr's deck arrangement, we belive that all five systems were 
succesfully deployed.  

The table below gives launch details:

       Serial no.  Date    Time   CTD no.  Latitude    Lonongitude  
       ----------  ------  -----  -------  ----------  -----------
       MT-111      Sep 26  1524Z     8     42 25.79 N  51 18.51 W
       MT-107      Sep 27  0521Z    11     41 50.22 N  51 46.96 W
       MT-116      Sep 27  2319Z    14     41  3.52 N  51 46.60 W
       MT-109      Sep 29  1645Z    20     38 56.52 N  52 15.08 W
       MT-110      Oct 01  0325Z    25     36 13.91 N  52 24.01 W 



______________________________________________________________________________
______________________________________________________________________________



WHPO/CCHDO DATA PROCESSING NOTES

Date      Contact   Data Type  Data Status Summary  
--------  --------  ---------  --------------------------------------------------
10/29/03  Delahoyd  CTD        Submitted/include the following headers  
          Format for A22 2db pressure-series downcast CTD data:
            Pressure              (decibars)
            Temperature           (ITS-90 Deg C)
            Salinity              (PSS-78)
            Dissolved O2          (uM/kg)
            Potential Temperature (ITS-90 Deg C)
            Sigma Theta
            Transmissometer       (0-5Volts)
          
02/11/04  Delahoyd  BTL        Submitted; These data were provided by:

            PARAMETER/PROGRAM   NAME                    EMAIL ADDRESS
            -----------------   ----                    --------------
            CHIEF SCIENTIST     JOHN TOOLE-WHOI         jtoole@whoi.edu
            CO-CHIEF SCIENTIST  ALISON MCDONNALD-WHOI   amacdonald@whoi.edu 
            CTDO/S/O2/Nutrients James Swift-SIO         jswift@ucsd.edu
            DIC                 Dick Feely- PMEL        feely@pmel.noaa.gov
            CFC                 William Smethie-LDEO    bsmeth@ldeo.columbia.edu
            TALK                Andrew Dickson-SIO      adickson@ucsd.edu
            CDOM, DOC, DON      Craig Carlson-UCSB      carlson@lifesci.ucsb.edu
            He/Tr               William Jenkins-WHOI    wjenkins@whoi.edu
            Surface C14         Ann McNichol-WHOI       amcnichol@whoi.edu      
            Surface C14         Robert Key-Princeton    key@princeton.edu
            C13 profiles        Paul Quay-UW            pdquay@u.washington.edu

          The data included in these files are preliminary, and are subject to 
          final calibration and processing. They have been made available for 
          public access as soon as possible following their collection. Users 
          should maintain caution in their interpretation and use. Following 
          American Geophysical Union recommendations, the data should be cited 
          as: "data provider(s), cruise name or cruise ID, data file name(s), 
          CLIVAR and Carbon Hydrographic Data Office, La Jolla, CA, USA, and 
          data file date." For further information, please contact one of the 
          parties listed above or whpo@ucsd.edu. Users are also requested to 
          acknowledge the NSF/NOAA-funded U.S. Repeat Hydrography Program in 
          publications resulting from their use.
          
03/10/04  Diggs     Cruise ID  Data File Relocated  
          The A20 data is formally online at a new location:
          http://whpo.ucsd.edu/data/co2clivar/atlantic/a20/a20_2003a/index.htm
            You'll notice that the expocode for the WHPO website is now 316N200309 
            (was 316N173/1). This is consistent with the way the WHPO/CCHDO now 
            keeps records and assigns expedition codes. Each cruise has an NODC 
            shipcode, then the 4-digit year and the 2-digit month taken from the 
            first date of the cruise. We realize that this may cause problems for 
            individuals who refer to A20 by the old expocode. 
          
04/14/04  Kappa     DOC        Updated Cruise Report as follows:
          Produced an ASCI version of the original PDF report
          Added WHPO/CCHDO Summary pages to PDF and ASCI reports
          Added internal links to figures and WHPO/CCHDO sections in PDF report
          Added he WHPO/CCHDO-generated Station Location Plot to PDF report
          Added these Data Processing Notes to the PDF and ASCI reports
         


