Temporal variability of the Baltic Sea level based on satellite observations

The main objective of this paper is to determine what are the most important time scales of variability of the sea level in the open Baltic Sea. The study is based on the 7-day resolution multimission global gridded sea level anomalies (SLA) for years 1992-2012 distributed by AVISO. For comparison satellite-derived SLA from the North Sea and North Atlantic, coastal data from the Stockholm tide gauge, the NCEP meteorological data, and river runoff data from the Balt-HYPE model have been also analyzed. We have applied time series analysis algorithms (Bendat and Piersol, 2011). Supporting earlier research, our results show that the variability of the sea level in the open Baltic Sea is highly coherent with the sea level in the North Sea. We have found out that the annual peak is not well pronounced in the open Baltic Sea SLA spectrum, but the semiannual peak is the most prevailing. In contrast, the annual peak is significant in the North Sea SLA power spectrum. The coherence between the open Baltic Sea and the Stockholm SLA is high and the SLA variability in these two locations is in phase. The results of the cross-spectral analysis between the SLA in the Baltic Sea and meteorological parameters (wind stress magnitude, zonal and meridional wind stress components, and barometric pressure at sea level) show that coherence is highest with the zonal wind stress component. Coherence between the river runoff and the SLA in Stockholm is not significant.