Impact of low ice area in Arctic on atmospheric circulation and climate extremes in mid to high latitudes of the Northern Hemisphere

The Arctic region has undergone a substantial climatic changes in recent years with dramatic sea-ice loss, evident particularly in late summer and early autumn. According to many findings the near-surface temperature in high latitudes of the Northern Hemisphere has been rising at rates double that of the lower latitudes and was amplified by rapid loss of sea ice in the Arctic through the snow and ice albedo feedback. Open, free of ice water has a smaller albedo than ice, absorbs more energy incoming from the Sun, resulting in much faster increase in temperature than other areas. The abrupt acceleration in Arctic warming well seen since the middle 1990s coincides with changes in climate in the mid-latitudes. The aim of this paper is to analyse the changes in atmospheric circulation in the mid to high latitudes in the response to low extent of ice cover  in Arctic in the preceding months.

To analyze the variability of sea ice cover in Arctic region we used daily sea-ice fraction data which are defined as the fraction of a grid box which is covered by sea ice. These data were multiplied by field of each grid box. After summing up all recalculated grid points, a new parameter named – area ice cover (AIC) was defined. We analyzed the AIC variability in the whole Artcic and in three sectors Atlantic - from 75°W to 60°E, Asian - from 60.25°E to 189.75°W and American - from 170°W to 75.25°W.

Then AIC index was correlated to selected northern hemisphere teleconnection: North Atlantic Oscillation (NAO), the Scandinavian pattern (SCAND), East Atlantic (EA), Polar/Eurasia index (POL). The Monthly NAO, SCAND, EA and POL values were provided by U.S. National Centers for Environmental Prediction (NCEP). The AIC preceded circulation indices by 1 to 12 months.

In regions and periods of significant correlation, composite maps of temperature anomalies, sea level pressure and geopotential altitude of 100 and 200 hPa in the years with low icing were created and analysed.

The analysis showed that the greatest changes in AIC are observed in Asian sector of Arctic and they have the strongest impact on the atmospheric circulation. AIC changes modulate circulation in both winter and summer period. However the nature of the impact is clearly different. A sensitive regions turns to be Barents and Kara Seas and Novaya Zemlya.