Modelling of Baltic Sea inflow events and deep water currents

Abstract

Both medium and strong intensity inflow events into the Baltic Sea contribute to the ventilation of the Baltic Sea deep water. The present study is an attempt to perform realistic model simulations of the Baltic Sea in order to quantify natural mixing of dense bottom flows. The numerical simulations are carried out using the General Estuarine Transport Model (GETM) for a twelve year period from the beginning of 1995 until 2006. Simulation results are compared to the field observations from the Baltic Environmental Database (BED) for selected stations at quite different locations in the Baltic Sea, namely Anholt (AN), Arkona (AR), Bornholm (BO) and Gotland (GO) stations. A medium resolution (2D } 2D) spherical grid bathymetry and adaptive terrain-following vertical coordinates have been applied. The model validation against observations shows that the results agree rather well. The build-up of the stratification is well reproduced, however, with an underestimation of the mixed layer depth. All significant inflow events are reproduced throughout the twelve years of simulations. The timing of the inflow events has been simulated with acceptable accuracy. The seasonal temperature variation is well represented as well as the occasional decrease/increase of the near-bottom temperature due to the winter/summer inflow.