An automated sampling and analysis system was developed to determine t
he total inorganic carbon (TCO2) in seawater. Measurements are perform
ed on subsamples taken from the shipboard flowing seawater line. The f
lowing TCO2 system (FTCO2) automatically acidifies and strips the CO2
out of a known volume of sea water and determines the concentration by
integrating the infra red (IR) absorbance. Laboratory results have de
monstrated an analytical precision of 2-5 mu M in TCO2 for this system
, Intercomparison of TCO2 measurements with the FTCO2 system and the S
OMMA (single operator multimetabolic analyzer) agreed within their res
pective uncertainties. The TCO2 in surface seawater was determined con
tinually on the flowing seawater line aboard the R/V Thompson in the A
rabian Sea. The average difference between the TCO2 determined on surf
ace seawater with the flowing system and the SOMMA was 6.5 +/- 8.7 mu
M. Measurements made with the flowing system on CRMs agreed to +/-3 mu
M with the assigned value. TCO2 in surface waters in the Arabian Sea
varied by as much as 40 mu M on short spatial and temporal scales. Alt
hough the accuracy of the present design of the FTCO2 system is not as
good as the SOMMA, the surface TCO2 variability with time and space i
s captured with the FTCO2 system and is completely missed by discrete
measurements made on CTD casts. Continual measurements of TCO2 will be
valuable in characterizing the temporal and spatial changes in the ca
rbon dioxide system in surface ocean waters. (C) 1998 Elsevier Science
B.V.