pCO(2) variability in the surface waters of the ultra-oligotrophic Levantine Sea: Exploring the air-sea CO2 fluxes in a fast warming region: Exploring the air–sea CO₂ fluxes in a fast warming region

Seasonal pCO(2) variability was studied in the Southeast Levantine (SE-Levantine) during 2009-2015 with the aim of quantifying air-sea CO2 fluxes in this ultra-oligotrophic, warm and highly evaporative marginal sea. Mixed layer pCO(2) varied significantly between 560 +/- 9.0 mu atm in August (summer) and 350 +/- 8.7 mu atm in March (winter). Comparison of pCO(2) to Sea Surface Temperature (SST) yielded a strong positive correlation (n = 135, r(2) = 0.94), suggesting that the seasonal variations are the result of a thermodynamic effect on the carbonate system in seawater. Using the coupling between pCO(2) and SST, we calculated the mean monthly values and the air-sea fluxes in this region. These calculations indicated that this region is a net source of CO2 to the atmosphere over an annual cycle, with an average flux of 845 +/- 270 mmol C m(2) y(-1) (similar to 0.98 Tg C y(-1)). Flux estimation for three other sub-basins of the East Mediterranean (South of Crete) with similar oceanographic conditions, were calculated from mean seasonal SST and wind data (MEDATLAS). The results suggest that these regions may either be a weak source or sink for atmospheric CO2. However, considering the relatively rapid warming trends (similar to+ 1 degrees C/decade) observed in the Levantine basin and the anticipated thermodynamic effect on pCO(2) levels in seawater, these sub basins could become more pronounced sources for atmospheric CO2. Thus, with the fast warming and increased stratification of its surface water the CO2 source of the Eastern Mediterranean is expected to expend spatially.