The exchange of dissolved inorganic carbon between the Baltic Sea and the North Sea in 2006 based on measured data and water transport estimates from a 3D model

The Baltic Sea is one of the largest estuarine systems on earth. Two narrow straits, Öresund and The Belt Sea, together with a large transition area consisting of Kattegat and Skagerrak hamper interactions with the North Sea. The Baltic Sea water is low in salinity due to the large freshwater input from river runoff to the Baltic Sea but has an excess of inorganic carbon from dissolution of carbonate minerals in the river drainage basins. In this study we use dissolved inorganic carbon data from the Baltic Sea and the Kattegat together with modelled water transport to evaluate the dissolved inorganic carbon exchange between the Baltic Sea and the North Sea during 2006. The total inorganic carbon export from the Baltic Sea in the straits area is 5.5 ± 0.3 Tg C year−1, or 0.45 ± 0.03 1012 mol year−1. These numbers are about 1/3 lower than earlier reported export values and will hence have a corresponding effect on budget computations of the connected seas.