Air‐sea CO2 fluxes on the U.S. South Atlantic Bight: Spatial and seasonal variability

Abstract

The partial pressure of carbon dioxide (pCO2) in surface seawater on the South Atlantic Bight (SAB) of the United States was measured during six cruises from January 2005 to May 2006. The high‐resolution pCO2 data allow us to create the first maps of the sea surface pCO2 over the SAB for all seasons. Contrary to an earlier study that was based on limited spatial and seasonal coverage, this study shows that the SAB is a net sink of atmospheric CO2 on an annual basis (−0.48 ± 0.21 mol m−2 a−1). The inner shelf is a source of +1.20 ± 0.24 mol m−2 a−1, while the middle and outer shelves are sinks of −1.23 ± 0.19 and −1.37 ± 0.21 mol m−2 a−1, respectively. Seasonally, the SAB shifts from a sink for atmospheric CO2 in winter to a source in summer. The annual cycle of sea surface temperature plays a dominant role in controlling the seasonal variation of the pCO2. Wind speeds are seasonally anti‐correlated with the air‐sea pCO2 differences, and this is an important factor in contributing to the net annual air‐sea CO2 exchange. Factors related to the estimates of CO2 fluxes in the coast ocean, such as the choice of wind speeds, the correction of gas transfer equations with nonlinearity coefficients, the effect of diel variations of pCO2, the spatial extrapolation of the pCO2 to the nearshore area, and the seasonal interpolation are also discussed.