Air–sea CO2 fluxes on the US Middle Atlantic Bight

One objective of the Ocean Margins Program (OMP) was to quantify air–sea CO2 fluxes on the US Middle Atlantic Bight (MAB). No measurements of the partial pressure of CO2 (pCO2) had been reported for the MAB prior to the 1994 OMP field program. A number of field studies have now taken place that include ship and mooring-based measurements of pCO2 spanning the years 1994–2000. We use these data to quantify the annual air–sea CO2 flux on the MAB. These calculations indicate that the MAB is a net annual sink for atmospheric CO2, with the inner, mid, and outer-shelf regions taking up ∼0.1, 0.7, and 0.2 Mt C yr−1, respectively, for a net uptake of ∼1±0.6 Mt C yr−1. The annual cycle of heating and cooling combined with high winds during the period of undersaturation (winter) appear to account for a significant portion of the uptake. The flux uncertainty is dominated by uncertainty of the gas-transfer velocity parameterization, atmospheric CO2 levels, and coarse spatial pCO2 resolution. Errors due to monthly averaging of wind and pCO2 time-series are relatively small in comparison. Recent results from other ocean margin regions found a significantly larger flux (in mol m−2 yr−1). Unlike the MAB, the increase in pCO2 due to summer heating appears to be counterbalanced by new production and the pCO2 never rises significantly above atmospheric saturation in these areas.