Changing impact of large-scale atmospheric circulation on the wind climate of the Baltic Sea area for the period 1948/1949-2018/2019

Abstract:

Changes in the warming trend of the Baltic Sea area since the mid-1980s are found to be associated with changes in the large-scale atmospheric circulation over the North Atlantic (Lehmann et al. 2011). From the analysis of sea level pressure (SLP) fields in winter several changes in the atmospheric circulations have been revealed. At first the storm tracks have intensified and shifted north-eastward together with the North Atlantic Oscillation (NAO) centres of action. Additionally, a seasonal shift of strong wind events from autumn to winter and early spring for the Baltic area was found. As atmospheric circulation controls to a large extent patterns of water circulation, then this kind of changes in the atmospheric circulation regimes force different circulation patterns in the Baltic Sea, that brings along changes in vertical distribution of temperature and salinity. The last may severely impact the trophic structure and functioning of marine food webs (Hinrichsen et al. 2007).

The further analysis of recent changes/shifts of the large-scale atmospheric conditions and their impact on the wind climate over the Baltic Sea area is feasible due to additional 20 years of NCEP/NCAR reanalysis data available. The EOF analysis of winter SLP anomalies shows that the NAO centres of action have shifted back to the more western position at the beginning of the twenty-first century. The variability in North Atlantic storm track intensity is very high, that causes also high variability in regional scale wind patterns in the Baltic Sea area. However, during NAO⁺/NAO^- DJF winter conditions the mean wind increases/decreases due to the dominance of a particular regime.

These results confirm that if we want to understand processes linking the marine environment and climate variability, we should investigate atmospheric circulation in the larger area with varying resolution in time and space.

Hinrichsen, H.-H., Lehmann, A., Petereit, C., Schmidt, J., 2007. Correlation analysis of Baltic Sea winter water mass formation and its impact on secondary and tertiary production. Oceanologia, 49(3), 381–395.

Lehmann, A., Getzlaff, K., Harlaß, J., 2011. Detailed assessment of climate variability on the Baltic Sea area for the period 1958 to 2009. Climate Research 46, 185–196.