Anthropogenic CO2 fluxes in the Otranto Strait (E. Mediterranean) in February 1995

This study presents the distribution and fluxes of dissolved inorganic carbon (CT), total alkalinity (AT) and anthropogenic carbon (Cant) along the Otranto strait, during February 1995. Based on a limited number of properties (temperature, dissolved oxygen, total alkalinity and dissolved inorganic carbon), the composite tracer TrOCA was used to estimate the concentration of anthropogenic CO2 in the Otranto strait. alkalinity exhibits high values and weak variability throughout the water column of the strait, probably associated with the dense water formation processes in the Adriatic basin that induce a rapid transport of the coastal alkalinity to the deep waters. Elevated Cant concentrations and high anthropogenic pH variations are observed in the bottom layer of the strait, associated with the presence of Adriatic Deep Water (ADW). The study shows that large amounts of Cant have penetrated the highly alkaline Eastern Mediterranean waters, thereby causing a significant pH reduction since the pre-industrial era. tes of the transports of CT and Cant through the strait indicate that during February 1995, the Adriatic Sea imports through the Otranto strait natural and anthropogenic carbon and acts as a net sink of carbon for the Ionian Sea. The anthropogenic carbon that is imported to the Adriatic Sea represents less than 1% of the net CT inflow. The Levantine Intermediate Water (LIW) contributes to about one-third of the total CT and Cant inflow. Although the amounts of Cant annually transported by LIW and ADW are almost equal, the contribution of Cant to the CT transported by each water mass is slightly higher in ADW (3.1%) than in LIW (2.6%), as a result of its higher mean Cant concentration. The ADW, despite its weak contribution to the total outflow of Cant, has a vital role for the sequestration and storage of the anthropogenic carbon, as this water mass is the main component of the Eastern Mediterranean Deep Waters and, thus, the anthropogenic CO2 is transferred in the deep horizons of the Eastern Mediterranean, where it remains isolated for many years.