PATTERNS OF CHANGES IN AVERAGE ANNUAL WATER TEMPERATURE OF THE RIVERS OF THE ARCTIC ZONE OF RUSSIA ASSOCIATED WITH CLIMATE CHANGE

The paper considers changes in temperature regime of rivers flowing northerner than 60th latitude. The investigation bases on data about average monthly water temperatures from 90 hydrological gages for the period 1960-2012. Annual water temperatures for this period were calculated according to the generally accepted method as average monthly temperature from May to September and according to the proposed in this paper calculation method for the entire period with positive water temperatures. It is shown that the calculation of annual water temperatures only from the average monthly temperatures from May to October, underestimates annual water temperature. The paper estimates changes in the average annual water temperatures calculated by both methods over the period 1991–2012 compared to 1961-1990 These periods cover intensive climate change, as well as the time after the construction of the largest hydroelectric power stations. Statistical analyzes of the obtained series for trends (according to the Spearman rank correlation test) and series uniformity disturbances (Mann-Whitney U-test) were carried out. A significant increase in the average annual water temperatures in rivers on most rivers of the Russian Arctic is shown. The greatest changes are observed in the territories of Yakutia. Significant changes are also noted on the Kola Peninsula. At the same time, the magnitude of the changes depends on various hydrological characteristics of the basin. Significant changes to date have occurred in less than 50% of the investigated rivers.