On the Relation Between Annual Maximum Extent of Ice Cover in the Baltic Sea and Sea Level Pressure as Well as Air Temperature Field

摘要

The annual sea ice cover in the Baltic Sea is a component of the cryosphere which is sensitive to climatic changes. The annual maximum extent of ice cover in the Baltic Sea 1720-1996 (Seinae and Palosuo, 1993) is a suitable time series to estimate the intensity of the ice winter in this sea. The time series shows a significant negative trend. By calculating the correlation coefficient fields between ice time series and air temperature field as well as sea level pressure field, the areas and the periods of maximum correlation could be found. As far as the temperature field is concerned there are significant correlation coefficients in the area around the Baltic Sea from November to April, while the sea level pressure field in the Northern Norwegian Sea and the Western Mediterranean Sea shows significant coefficients from December to March. An exponential regression model containing the mean temperature from November to March of the 10° gridpoint area (55-65° N, 20-30° E) as predictor explains 86% of the variance. An estimate of the future development of the annual maximum extent of ice cover in the Baltic Sea can be obtained with the help of temperature time series of same area and period computed by the coupled General Circulation Model ECHAM4/T42_OPYC3 (Max-Planck-Institute for Meteorology, Hamburg). As to IS92a scenario (IPCC) a drastic decrease in the mean extent of ice cover would follow in the next 100 years.