Final Technical Report

Title:

Principal Investigator: Charles D. Keeling Period of Report: Award No. 111 Address: Scripps Institution of Oceanography

Oceanic Cot Measurwrente for the WOCE Hydrological Survey h the Pacific Oceaa; Shipboard Alkalinity A n d m During 1991 and 1992

1 February, 1992 through 31 July, 1994

750 qcp/ 6 / 1 /L- - rA University of California, San Diego La Jolla, CaMornia 92093-0220

S w of Progrers

By thia grant, our resestch group contributed titration alkalinity analyses to tra;aeecte of the WOCE Eydmbgicd Survey during 1W1 and 1992. The resulta have been t r d t t e d to the Carbon Dioxide Idomnation and Analyeis C e a k (CDIAC) of the Department of Energy in a techniccsl data report hsving two papt8:

Oceanic COz Measurements for the WOCE Hydrographic Survey of the Pacific Ocean, 1990-1991: Shipboard Atralyea During I991 and 1692, Part 1. Alkalinity Me~vements on TUNES, Leg 3,1991 Oceanic CO, Measurements fo: the WOCE Hydmgraphic Survey of the Pacific Oceaa, 1990.1891: Shipboard hdy- During 1991 and 1992, Part 2. Akkalinity Meaaumsnents on CGC92, Lega 1 and 2,1992

Part 1 waa sent to CDUC on 14 October, 1884 and Part 2 waa sent on 24 October, 1994. Part 1 involves data for a tr-t from Tahiti to Hawaii along WOCE Line Pl8C while Part 2 invoiverr WOCE Line PI3 from Dutch Harbor, A l d a to Noumea, New Cdedonia. The grant elso covered the coet of analy~es of Diseolved hiorganic Carbon on Cru'k CGC92, carried out by the laboratory of Dr. Andrew Dieteon of the Scripp Institution of Oceaoogrsphy. A Find Teehai- cal Report on DIC wiI1 be eent to CDUC as ~ o o n as pcmdble.

No journal publications bsve yet been submitted with respect to thie grant.

This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or use- fulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any spe- cific commercial product, process, or smite by trade name, trademark, manufac- turer, or otherwise dots not necessarily constitute or imply its endorsement, recom- mendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.

DISCLAIMER

Portions of this document may be illegible electronic image products. Images are produced from the best available original document.

Total dissolved inorganic carbon measurements made on WOCE leg P13 (NOM CGC'92) Andrew 6. Dlckson

A summary of tht mcasu~mctab of total dissolved inorganic carbon nrrrde on th is expedltlon (Aug 3 - Oct 21,1992) mdng thc SOMMA instrumeat. A brief description of how thew ~&easur#nents w e n made and calibrated has been provided dong with a statement of the quallty of the measurements. The data themrehw have been sent to ORNL CDIAC for archival and dktribotion.

Table of Contents

CJtUISE BACKG~OUND 2 Xntmduc tion 2 Leg 1 Expocode 322OCGC9U1

Leg 2. EXPOcode 322QCGC!W2

2

2

MEASUREMENT OF TOTAL Drsso~vm INORGANIC CARBON 3 Introduction 3 Stations sampled for C02 measurements 3 Sampllag Andysh technique

Otder ot analyses

Celibrattan of the enalyses

Measurement data quolity 6 DATA ARCRIVAL INFORMATION 7

R~SFERENC~S 8

1

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Int roducllon

Cruise Backgmund

This cruise was carried out on the U. S. registcrcd research vessel RNJohn K Wckrs. This vessel was opemced by the University of southern Colifornia together with officers from the NOAA corps.

Thr god of the cruisc was to c m y out a World Ocean Circulation Expcriment (WOCE) one-time hydrographic section: the onc dcsignated PI3 which runs daw, the line of lotigitudz 165"E from the Kamchatka peninsula to New Cddonitl. The cruise was split into two legs for logistical regions

Leg 1 EXPOcode 3220CCaCW1

The chief scientist for Leg 1 ol'the cruise was Dr. John Bullivter froni YO& 'DMEL. The Vickers left Dutch Harbor (Alasko) on 16 August, 1992 to car- out the cruise, and curivcd at Kwajalein (Marshall Islands) on 15 Szpember, 1992.

Leg 1 consisted of 51 stations (Sa. 5-55). The first station on this leg (Station 5 ) was a test CTDlrosette cast m d c in the Bering Sea. dong thc transit from Dutch Harhor to the start of the PI3 line near the Kmchatka Peninsula. Sampling of the PI3 section began nn 2 1 August 1992 near the 200 meter isobeth off Kamchetka. A sdes of stations werc occupied on Y southwtward trapsit down the continental slop and across the Kmchatka Trench. The section turned directly southward at about 51 O 30' N, 165" E, and continued along the 165" E meridion for the remainder of Jieg 1. Nominal station spacing was 30 nautical miles from the start of tbc section to about 40" N. Due to a series of delays during the first part of Leg 1 a decision was made at about 36" N to smtch nominal station spacing for thc remainder of Leg 1 (36' N - 10" N) to 40 nautical miles.

Duc to concerns about possible structural deformation to Vickers. and concern over failure of a water-tight door to close proprtly, work on the P13 CTD/tosette section was halted on 9 September 1992 at about 30" N, and flckers was ordered to steam directly to Kwajalein. We were unable to wcupy any stations along the emergency unnsit to Kwajalein.

Leg 2. EXPOcode 322OCGC92t2

The chief scientist For the second Icg of the cruise (Sep 26, 1992 - Oct 21,1992) was Dr. B N C ~ Taft from N O W E L

Vic&ers remained at the dock in Kwajalein for an eatended period of time for evdwdtinn of structural inlcgrity by two tnlvinc architects and for =pair. ViCRers I& Kwajalein on 26 September 1992 and began steaming back to the break-off point EO continue work on the P13 section.

Contact was made with TOGA-COARE investigatorv (the group scheduled to use vickers following the completion of the P13 section) to negotiatc an extension For

t . Fortions of this narrative arc based on the Chief Scientist's repon which is available from the WOCE Hydrographic Propm Ofice at the Scripps Institution of Ocennography: http://whpc.ucsd.eBu/data/onctime/pacific/pl3/gl3a/pl3ado.txt

2 Total di.rst?lved inorganic carbon mearurements made on WOCE leg P I 3 (NOM

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c

Introductlon

Stetlons earnpted kt C02 measurement8

k g 2, which would allow us a reasonable chance to complete the PI 3 section. After direct neEotiationr with TOGA-COARE investigators over the revised Vickers schedule, we were unable to come up with a niutually satisfactoly agreement. The. position held by TOGA-COARE at the end of these negotiations (requiring V i c h to be in port in Noumea on 21 October 1992) did not allow us enough time to complete the WOCE PI3 section 10 even minimum WHP specifications. Since an aggrecmcnc could not k rcichcd between rbc 2 progrrunu, the final dccivion wcw rnadc by the Director of NOAA's Office of Global Programs, who sent instructions to USC that Vickers should arrive in Noumea on 21 October for TOGA-COARE staging.

With the remaining allocated time. Vickers occupied CTDImsctte stations at a nominal spacing of about 2" from 28" N to 4" N, and closer spacing from 4" N to 4" 30' S. Lowered ADCP measurements were m d e on stations between 4 N and 4 S. The section was terminated on 17 October 1y92 at 4" 45' S 164" 0' E in order to arrivc in NC-mca by the 21 October Jcadline. A t o d of 32 sutiona (Sta 56-88) wete occupied during Lcg 2 (one station Sta. 60 was aborted and not included in the listings).

Measurement of Total Dissolved Inorganic Carbon

The sampling and analysis for total dissolved inorganic carbon w a pcrt'ormcd in conjunction with the sampling and turafysis for measurements of total alkalinity. The pcrsonnel involved were:

Leg 1 : Total elkplinity: Peter Guenther (SIO), Guy Emanuele (SIO) Total carbon diolside: Oeorge Anderson (SIO), Ron Cictennan (Batwlle, PNL)

Lcg 2: Total alkalinity: Andrew Dickson (SIO), Guy Emanuele (SIO) Total carbon dioxide: Llomine Bell (SIO), Ron Citterman (Battelle. PNL)

A full depth profile was not sampled at every station occupied. This was bccauvc an individual analysis of totii! dissolved inurganic carbon analysis took about 25 min, and consequendy P complete station, rogethcr with the various quality control fiamples and thc instrument set-up (new cell, wait for good background) took about 22 hours !n all.

We thus measured as often as we could - approximately every third sti~tic~n when stations had the normal WOCE spacing - and we also analyzed R surface samplr; takcn at the intervening stations. Full profiles we available for the following stations.

Leg I: 5,8, 11, 13, 17,20,24,26,29,32, 36,3#, 41,45,47,49,51,52.53,54.55

Leg2: 57,59,62,63,64,65,66,67,68,69,70,71,73,75. 78, 81. 83. 87

The exact locations of these stations are given in the main WOCE cruisc rcporl and data files which are available from the WOCE Hydrographic Program Office: h t t p : / / w h p o . u c s d . e d u / d e t a / t a b l e s / o n e t i m e a c . h t m

Total dissolved inorganic carbon measurements made on WOCE leg PI 3 (NOM CCC'92)

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Sampling

Analyele technique

Order of analyses

Measurement of Tobl Obeolvad Inorgenie Carbon

The samples for total dissolved inorganic carbon were taken in 500 mL borosilicate @..E bottles in accordance with the procedure specified in SOP 1 of the DOE (1994) Handbook of Methods an earlier version of which was available ~t the time (DOE, 1991). The Eatnples were thus poisoned with mercuric chloride to minimizc biological activity prior to analysis.

"bo duplicate samples were taken and analyzed for each p~filr;: one in sutfacc water (near the top of the cast) and one in deep water (ncar the bottom of the cast). Thesc are used to assist in the msessmcnt of thc mcasurcmcnt quality.

The samples were analyzed using a Single Operator Multiparame~ Metabolic Analyzer (SOMMA) dcveloped by Mr, Ken Johnson (Johnson d af., 1985; 1987). The procedure using this spcific instrument i s described in detiiil in the S O W Operating Manual (Johnson, 1991 ), it description of the procedure is available in the DOE (1994) Handbook of Methods (SOP 2).

"%e principle behind this analysis is as follows: a known amount of seawater is dispensd into a stripping chamber where it is acidified and purged with an inert gas. The presence of solid carbonates, such as CaC0.3, thus constitutes an interfercncc in thc method. The amount of CO, in tbe resulting gm-streatn is determined by absorbing the CO, in an absorbent containing ethanolamine and titrating coulometrically the hydroxycthylcarbamic acid that is formcd. The pH of the solution is monitored by measuring the transmittance of thymolphthalein indicator at approximately 61 0 nm. Hydroxide ions are generated by the coulometer circuitry so as to maintain the bmsmittance of the solution at a constant value. The relevant chemical rcactims occumng in the solution are:

CO, + HO(CHz)2NH, + HO(CH2)zNHCOO- + H+

and

H++oH-+H,o.

Thc hydroxide ions used are generated at the cathode by electrolyzing water:

while silver is dissolved at the mode:

Ag(s) 4 Ag+ + e-.

The overall efficiency of thc coulomevic proccdun: is calibrated using known amounts of COZ gas, either fiom gas loops or fiom sea water based reference materials.

The samples were analyzed in the order surface to deep - this gavc time lor the cooler deep samplcv to come to room temperature before they were analyzed. However, this rncans that i t i s not possible to ascertain from the analytical measurements alone if there

4 Total dissolved inorganic carbvn meaxumtnents made on WOCE leg P13 (NOM

Yoeruremcmt of Total D l r ~ ~ h d inorganic Cerbon

means chat it is not possible to asccrtain from the analytical measurements done if there i s a systematic variation in the calibration with the life of the coulometric cell (&e section “Calibration of the analyses“ on page 5).

Cellbratlon d the anelywa The calibration of the andyses reported here was problcmtltic. The original plan was to usc gas loops to calibrate: the coulometer system, and to check the ptrforrnance of the analyses using certified reference materials (CRM Batch 13 - certified C, value 201 5.1 3 pnol kg‘’). Unfortunately, 8 post-mise examination of the resulu showed that the calibration factor calculated for gas Imps was unexpectedly variable; an examination of the calibration factor that would have been cakulakrl from the analyses of the certified reference materials also showed similar variability (equivalent to 8 standard deviation of measurement uf 2.4 pnol kg-’).

A more detailed examination showed that the variability was restricted to those’ measurements drat had been made in the early stages of a cell’s lifetime: tneasuremcnts on gas loops (Figure 1) or on reference materials (Figure 2) made later in the cell’s

FIQURE 1. CaUbrntion Pectord hpm “gns loops” - exprwrsed aa countdpmol.

lifetime were much more stable as wcll as being lower (countdpmol) than the initial mcasurements.

The reason for this oppzanr to be that the cell was not adequetdy ccmditioncd prior to being calibrated and used (Ken Johnson, personal communicarion). Consequently, measurements made early in the cell lifetime arc suspect. These include all of the initial gas loop calibrations as well 3s the initial measurement of the reference material. The early meawremenrs - made on watcr fiom the upper mean - may dso he somewhat degraded (see “Measurement data quality” on page 6).

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Total dissolved inorganic carbon mearummerits made on WOCE leg PI3 (NOM CGC’92)

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Meaeurement data quality

~

Meaeurement oltolal Moiolved Inorganic Carbon

4860

4740

FIQURE 2 Callbrntioa factors h m cccRMs” - expressed (u cOuaWpnol.

Thc calibration approach uscd to cafculere the results presented here was AS follows: The calibration of an individual coulomctcr was ssumed to remain stable from day to day throughout its period of use. This assumption reflects the experience of m s r inve,dgators (see Dickson, 1992) and is also borne out by the memummntsfmm thig cruise nude later in the cell I @ {Figute I arui Figure Z}. Note that a single coulometer unit was used throughout Leg 1, and for part of Leg 2; it was exchanged during Leg 2 on October 3, 1932 prior to nieesuring samples from Station 65. Thus the measurements on rt-ference materials wen: divided into two groups: one prior to station 65. the other from station 65 to the end of the cruise, and a mean calibration factor was ralcufatcd separately for each group of analyses (based on the measurements made on reference materials - later in the cell lifetimc). This universai (coujoaeter dependent) calibration factor (i.e. based on the C R M s ) was used to calibrate h e measurements made on individual sea water samples.

Bccausc of tho difficulty in assigning B mcdngful calibration to the malyscs of t o d dissolved inorganic carbon made on this cruise, it is hard to assess the dab quality of the meawrernents presented here. Althougb it is apparent that analyses made “later in the coulometric cell’s lifetime” are less variable (Figure 1 & Figure 2). it is less clear when the meaurhg system “settles down”. Thw the meauurcments that 3re m d r early in the cell lifetime are also necessarily suspect (this is discussed in more detail below).

One indication of the potential accuracy of thc mcasumnent systcm is thc dcgrcc oi agreement between the calibration factors b w d on gas loops end tbosc blwcd on CRMs. The average difference is of the order of 0.1% (kg 1: 0. I4%, Lcg 2; 0.06%) thus indicating that the gas loops had the potential of providing an accurate calibration if the cell had been adequately conditioned.

6 Total dissolved inorganic carbon measun?menis made on WOCE leg PI3 (NOM

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Data Archival Intonnetton

The precision of measurement is harder to assess. Duplicarc: samples were taken at each full station. These were typically a surfwe sampk (in the top 10 m) and a deep sample (usually the from one of the two dccpcst NiYkin bottles). The duplicates were analyzcd wtth the surfncc pair being analyzcd at thc beginning of a run, and the deep pdr bdng split hetween the beginning and end of a mn.

The standard deviation of a single measurement calculated from these duplicates was:

For the “surface” samples (analyzed together) - 1.3 pnol kg-’. For the “deep” samples ( a n J y d at thc y t a t and end of a run) - 2.0 p o l &g-l

Howevcr, the standard deviation figures are somewhat misleading. The mean difference for the surface samples (first - second) is 0.4 p o l kg-’; that for the deep samples is 1.2 pmol kg-’. This suggests that even during the measurement of thew Cuplic: Y the “calibration” OF the cell is changing in the direction shown in Figure 1 and Figure 2. Hcncc the measurements on the samples done in rhc first patt of a run - those from the uppor mean - may. on occasion. be biased low by thc USE of a calibration factor more appropriate to the “later” measurements. An examination of the data on duplicates indicates that the extent of this bias is unlikely to exceed 4 pmol kg-’ and may on many occasions be less than That. ThC measurements on the later (deep) samples would bc expected to have a precision hat similar to that found for the later CRh4s: 8 s w n h d deviation of 1.1 pmd kg-’, ie. a similar magnitude to that found for those duplicate measurements that were run side-by-side at the beginning of the run.

Data Archival Information The actual memuremenis madc on his cruise are not included in this document. A copy of the full data set - together wilh a copy of this document which constitutes the necessary metadata - has been sent separately to the Ctvbon Dioxide Information and Analysis Center (CDIAC) in Oak Ridge, Tennessee whcrc the total carbon measurements will be combined with the total alkalinity measurements and the final WOCE data set and then made avdablc for distribution as a Numeric Data Package.

Total dissolved inorganic carbon measuremenismorle on WOCE leg Pf 3 (NOAA CGC‘Y2)

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References

Dickson A. G. (1992) The dttertninarion of total dissolved imrpttic carbon in sea water using extrnction/coulometryryr the first stage of a colhbomtive study. U. S. Depsrtment of Energy Report No. DOE/RUOI 830T-Hl4

DOE ( 1991) Handbook of methods for the analysis of rhe various pummefers uf the carbm dioxide system in sea water: edited by A. G. Dickson & C. Goyet (Manuscript version distributed to DOE Scicncc Team).

DOE { 1994) Handbook of nlethodv for rhe Mcrlysis of the various parameters of the carbon dioxide system in sea water. (Version 2), A. a. Dickson & C. Goyet, e4s. OWCDIAC!-74.

Johnson K. M., A. E. King and J. M. Sieburth (1989) Coulometric TC02 analyses for mluiru: studice; An introduction. Marine Chembrry 16,6142.

Johnson K. M. and J. M. Sieburth (1987) Coulometric total carbon dioxide analysis for marine studies: Automation and calibration. Marine Chemistry 21, 117-133.

.', - -1

Rekmncea

8 Total dissolved inorgwiic carbon measuremenfs mu& on WOCE leg Y13 (NOM

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