Modeling of climate tendencies in Arctic seas based on atmospheric forcing EOF decomposition

Abstract

The article analyzes the results of the EOF decomposition of climatic data and assesses the role of its components in the formation of climatic ice tendencies of recent decades. The analysis considers a state vector, which includes sea level pressure, surface air temperature, and surface wind, scaled accordingly. The seasonal cycle variations were also considered. An assessment of the ocean-ice system sensitivity to the time scales of atmospheric processes, based on the SibCIOM model, showed that the rate of decline of the annual ice minimum volume decreases by 2/3 when atmospheric forcing contains no variations of the 8–30-day scale, that is, if the formation of atmospheric blockings is excluded. Applying trend elimination for each of the EOF modes, comparing the results of the simulation with the base experiment which includes all trends, it was possible to estimate the role of each mode in shaping the trend of Arctic ice volume decline. The comparison shows that the first mode, representing the seasonal cycle, forms an integral tendency of ice volume decline by 96% of the original trend. Among other modes, the strongest influence on this trend shows second mode, representing Arctic Oscillations; it forms trend by 17%, and third mode, resulting from inclusion of the surface air temperature into the state vector, by 18%. In the marginal seas, the role of higher modes becomes not so small in comparison with the first mode.