Alkalinity of the Mediterranean Sea

Total alkalinity (AT) was measured during the Meteor 51/2 cruise, crossing the Mediterranean Sea from west to east. AT concentrations were high (similar to 2600 mu mol kg(-1)) and alkalinity-salinity-correlations had negative intercepts. These results are explained by evaporation coupled with high freshwater AT inputs into coastal areas. Salinity adjustment of AT revealed excess alkalinity throughout the water column compared to mid-basin surface waters. Since Mediterranean waters are supersaturated with respect to calcite and aragonite, the excess alkalinity likely reflects alkalinity inputs to coastal areas close to regions of deep and intermediate water formation. An alkalinity budget shows that main alkalinity inputs come from the Black Sea and from rivers, whereas the Strait of Gibraltar is a net sink. The major sink appears to be carbonate sedimentation. The basin-average net calcification rate and CaCO(3) sedimentation was estimated to be 0.38 mol m(-2) yr(-1). The estimated residence time of AT is similar to 160 yr.