Spatial variability of the CO2 sink in the Sargasso Sea

Abstract

Spatial elds of the partial pressure of carbon dioxide (pCO ) were derived for the entire Sargasso Sea from three-day composite satellite images of sea-surface temperature (SST) and established empirical relationships between surface pCO and SST. Application of the retrieval method from summer of 1994 through fall of 1996 faithfully reproduced the annual cycle of surface pCO at the US JGOFS Bermuda AtlanticTime-Series Study (BATS) site, with a cross-validated root-mean-square (rms) error of 11 }14atm. Estimates of air}sea CO exchange were made using satellite-derived surface pCO and surface wind distributions from global analysis products. Present estimates of air}sea CO exchange at the BATS site agreed well with previous determinations made using in situ data sets. The Sargasso Sea o!shore of the Gulf Stream was found to be a net annual sink for CO (north of 293N at the western end of the study area, and north of &263N at the eastern end). Interannual variability in the net CO exchange was not large ((5%) when integrated over the entire study area, but signicant interannual di!erences existed in the meridional and zonal gradients of CO #ux. These were largely driven by interannual di!erences in seasonal spatial wind distribution. The BATS site was found to be in a region of the strongest spatial gradients of air}sea CO #ux. The present study illustrates the importance of spatial data sets to extrapolating point determinations of the CO #ux to regional scales. 2001 Elsevier Science Ltd. All rights reserved.