Title: Scenarios of Multi-Annual Simulations of the Coupled North Sea - Baltic Sea system
Authors: STIPS AdolfBOLDING KRISTENSEN KarstenLILOVER Madis
Citation: Proceedings of the 13th International Workshop on Physical Processes in Natural Waters - ISBN 978-88-903895-0-4 p. 1-9
Publisher: University of Palermo
Publication Year: 2010
JRC Publication N°: JRC53419
URI: http://publications.jrc.ec.europa.eu/repository/handle/JRC53419
Type: Contributions to Conferences
Abstract: The Baltic Sea is a brackish semi-enclosed sea having a very limited water exchange with the more saline North Sea. The limited water exchange and large river runoff lead to typical two-layer salinity stratification with a permanent halocline located at about 60-70 meters below the sea surface. The aim of the present study is to make scenario simulations of the coupled North Sea - Baltic Sea system using the GETM (http://getm.eu) hydrodynamic model. Specifically we want to test the influence of different model settings, parameterization schemes, initial conditions and of a variety of forcing conditions on the occurrences and strength of salt water inflows. The model area covers the connected Baltic Sea and North Sea, therefore no prescribed barotropic sealevel forcing in the Kattegat area is applied. Initial conditions and 3D boundary conditions are derived from climatological data. The tidal forcing is applied at the open boundaries in the English Channel and at the open North Sea. Different relatively coarse data sets for the meteorological forcing were used (ERA40, ERAIN, CLM). Despite of that coarse spatial resolution the main features of the inflow dynamics could be qualitatively reproduced. For the river inflow we used climatological data for the 30 most important rivers within the model area. Factors that influence the water exchange comprise the large scale air pressure fields, the corresponding wind fields specifically in the channel area, the fresh water run off to the Baltic Sea, water level (filling state) of the Baltic Sea, tides, the exact bathymetry determining the cross sectional area and the related bottom friction as well as the vertical and horizontal mixing processes A first assessment of the long term effect of the saltwater exchange is performed by comparing the salinity changes at the Gotland Deep from the different simulations. We established that the most critical forcing component is the strength of the actual wind forcing, followed by the importance of the fresh water flux. The role of the air pressure field and of the tidal forcing is smaller, but they cannot be neglected for achieving realistic simulations. The most important GETM internal model characteristic appeared to be the used internal pressure gradient parameterization scheme, followed by the turbulence parameterization and the applied advection scheme.
JRC Institute:Institute for Environment and Sustainability

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