Freshwater outflow of the Baltic Sea and transport in the Norwegian current: A statistical correlation analysis based on a numerical experiment

Abstract

Based on the results of a numerical ocean model, we investigate statistical correlations between wind forcing, surface salinity and freshwater transport out of the Baltic Sea on one hand, and Norwegian coastal current freshwater transport on the other hand. These correlations can be explained in terms of physics and reveal how the two freshwater transports are linked with wind forcing, although this information proves to be non-sufficient when it comes to the dynamics of the Norwegian coastal current. Based on statistical correlations, the Baltic Sea freshwater transport signal is reconstructed and shows a good correlation but a poor variability when compared with the measured signal, at least when data filtered on a two-daily time scale is used. A better variability coherence is reached when data filtered on a weekly or monthly time scale is used. In the latest case, a high degree of precision is reached for the reconstructed signal. Using the same kind of methods for the case of the Norwegian coastal current, the negative peaks of the freshwater transport signal can be reconstructed based on wind data only, but the positive peaks are under-represented although some of them exist mostly because the meridional wind forcing along the Norwegian coast is taken into account. Adding Norwegian coastal salinity data helps improving the reconstruction of the positive peaks, but a major improvement is reached when adding non-linear terms in the statistical reconstruction. All coefficients used to re-construct both freshwater transport signals are provided for use in European Shelf or climate modeling configurations.