Spatial variability of the CO2 sink in the Sargasso Sea

Spatial fields of the partial pressure of carbon dioxide (pCO(2)) were deri ved for the entire Sargasso Sea from three-day composite satellite images o f sea-surface temperature (SST) and established empirical relationships bet ween surface pCO(2) and SST. Application of the retrieval method from summe r of 1994 through fall of 1996 faithfully reproduced the annual cycle of su rface pCO(2) at the US JGOFS Bermuda Atlantic Time-Series Study (BATS) site , with a cross-validated root-mean-square (rms) error of 11-14 mu atm. Esti mates of air-sea CO, exchange were made using satellite-derived surface pCO (2) and surface wind distributions from global analysis products. Present e stimates of air-sea CO, exchange at the BATS site agreed well with previous determinations made using in situ data sets. The Sargasso Sea offshore of the Gulf Stream was found to be a net annual sink for CO, (north of 29 degr eesN at the western end of the study area, and north of similar to 26 degre esN at the eastern end). Interannual variability in the net CO, exchange wa s not large( < 5%) when integrated over the entire study area, but signific ant interannual differences existed in the meridional and zonal gradients o f CO, flux. These were largely driven by interannual differences in seasona l spatial wind distribution. The BATS site was found to be in a region of t he strongest spatial gradients of air-sea CO, flux. The present study illus trates the importance of spatial data sets to extrapolating point determina tions of the CO, flux to regional scales. (C) 2001 Elsevier Science Ltd. Al l rights reserved.