Baltic sea water exchange and oxygen balance

Abstract

The Baltic Sea is surrounded by ten countries with 86 million people living in its drainage basin. Its environmental conditions depend very much on water exchange with the North Sea through the narrow Danish Straits. The strong vertical stratification decouples deep layers from atmospheric influence, and hence renewal of bottom layer water takes place only through inflow of saline water. During earlier decades renewal of the bottom layers has been an irregular phenomenon, but still it has occurred often enough. However, since the 1980s major inflows, able to renew deep bottom layers, have occurred only twice. As a consequence, even major inflows have been unable to remove the hydrogen sulphide from the deep layers. To improve the situation, major inflows would be needed almost annually. It is, therefore, possible that in the future the bottom layers will have a permanent oxygen deficit. © 2012 Springer-Verlag Berlin Heidelberg.