Scale-dependent relationship between maximum ice extent in the Baltic Sea and atmospheric circulation

Previous studies have demonstrated the importance of large-scale atmospheric circulation on the maximum ice extent (MIE) over the Baltic Sea. The main objective of this study is to gain some understanding of the scale-dependent variability of the MIE in relation to the large-scale atmospheric circulation. Wavelet analysis was applied to the observed and modelled MIE observation to identify the association between them as a function of time scale. The model used is a statistical model linking a set of indices describing the large-scale atmospheric circulation and the MIE. The analysis enables verification of the statistical model regarding its ability to reproduce variability at various time scales. The analysis shows that for the both variables, the amplitudes and frequencies of the variations on all scales vary with time. The correlation between the MIE and the atmospheric circulation is strongest at the longer time scales (>64 years) and weakest at the time scale of 32 years. The correlation at the interannual and decadal scales lies in between and is fairly strong. Further, the linkage on all time scales becomes stronger after 1940.