Variability of the net air-sea CO sub(2) flux inferred from shipboard and satellite measurements in the Southern Ocean south of Tasmania and New Zealand

• Published in: Journal of geophysical research. Oceans Vol. 110; no. C9
• Main Authors: Rangama, Y, Boutin, J, Etcheto, J, Merlivat, L, Takahashi, T, Delille, B, Frankignoulle, M, Bakker, DCE
• Format: Journal Article
• Language: English
• Published: 01-09-2005
• Subjects: Carbon dioxide; Correlation; Estimates; Flux; Marine; Oceans; Partial pressure; Satellites; Southern Ocean; PSE, New Zealand; PSE, Antarctic Ocean; PSE, Australia, Tasmania; PS, Antarctic Ocean
• ISSN: 2169-9275; 2169-9291
• DOI: 10.1029/2004JC002619

We determine the distribution of oceanic CO sub(2) partial pressure (pCO sub(2)) with respect to remotely sensed parameters (sea surface temperature (SST) and chlorophyll (Chl)) in order to gain an understanding of the small-scale (10-100 km) pCO sub(2) variability and to estimate the net air-sea CO sub(2) flux in the region (125E-205E; 45S-60S), which represents 22% of the Southern Ocean area between 45S and 60S. We split the study area into several biogeochemical provinces. In chlorophyll-poor regions, pCO sub(2) is negatively correlated with SST, indicating that pCO sub(2) is mostly controlled by mixing processes. For Chl > 0.37 mg m super(-3), pCO sub(2) is negatively correlated with Chl, indicating that pCO sub(2) variability is mostly controlled by carbon fixation by biological activity. We deduce fields of pCO sub(2) and of air-sea CO sub(2) fluxes from satellite parameters using pCO sub(2)- SST, pCO sub(2)-chlorophyll relationships and air-sea gas exchange coefficient, K, from satellite wind speed. We estimate an oceanic CO sub(2) sink from December 1997 to December 1998 of -0.08 GtC yr super(-1) with an error of 0.03 GtC yr super(-1). This sink is approximately 38% smaller than that computed from the Takahashi et al. (2002) climatological distribution of [delta]pCO sub(2) for the 1995 year but with the same K (-0.13 GtC yr super(-1)). When we correct ocean pCO sub(2) for the interannual variability between 1995 and 1998, the difference is even larger, and we cannot reconcile both estimates in February-March and from June to November. This strengthens the need of new in situ measurements for validating extrapolation methods and for improving knowledge of interannual pCO sub(2) variability.