Partial pressure and air–sea CO 2 flux in the Aegean Sea during February 2006

Abstract

Data on the distribution of fCO 2 were obtained during a cruise in the Aegean Sea during February 2006. The fCO 2 of surface water ( fCO 2 sw) was lower than the atmospheric fCO 2 ( fCO 2 atm) throughout the area surveyed and Δ fCO 2 values varied from −34 to −61 μatm. The observed under-saturation suggests that surface waters in the Aegean represent a sink for atmospheric CO 2 during the winter of 2006. Higher fCO 2 sw values were recorded in the ‘less warm’ and ‘less saline’ shallow northernmost part of the Aegean Sea implying that the lower seawater temperature and salinity in this area play a crucial role in the spatial distribution of fCO 2 sw. A first estimate of the magnitude of the air–sea CO 2 exchange and the potential role of the Aegean Sea in the transfer of atmospheric CO 2 was also obtained. The air–sea CO 2 fluxes calculated using different gas transfer formulations showed that during February 2006, the Aegean Sea absorbs atmospheric CO 2 at a rate ranging from −6.2 to −11.8 mmol m −2 d −1 with the shipboard recorded wind speeds and at almost half rate (−3.5 to −5.5 mmol m −2 d −1) with the monthly mean model-derived wind speed. Compared to recent observations from other temperate continental shelves during winter period, the Aegean Sea acts as a moderate to rather strong sink for atmospheric CO 2. Further investigations, including intensive spatial and temporal high-resolution observations, are necessary to elucidate the role of the Aegean Sea in the process of transfer of atmospheric CO 2 into the deep horizons of the Eastern Mediterranean.