Inflow dynamics of North Sea water into the Baltic Sea – Major Baltic Inflows
Major barotropic inflow events (MBI – Major Baltic Inflow) transport large volumes of salt water from the North Sea into the Baltic Sea within a short period of time. They are the only source of deep-water aeration in the central Baltic Sea basins and largely control the environmental conditions below the halocline. The time series of barotropic inflow events measured and analysed at the IOW starts 1886 and is updated annually. Exceptionally large inflow events occurred, for example, in January 2003 and December 2014.

Suboxic and anoxic areas in the deep water of the Baltic Sea

Due to the limited water exchange with the North Sea and permanent salinity stratification, periods of stagnation regularly occur in the deep waters of the central Baltic Sea, leading to nitrate depletion, increasing concentrations of ammonium and phosphate in the deep waters, decreasing oxygen concentrations, and the formation of hydrogen sulfide. The distribution of suboxic and anoxic zones in the deep water of the Baltic Sea is determined during monitoring cruises (February, March/April, May, July/August, October/November) and has been mapped since 1969.