Climatic Changes of Thermal Conditions in the Pacific Subarctic at the Modern Stage of Global Warming

Abstract

Purpose. The study is aimed at identifying the regional features of the surface air temperature in the coastal zone and over the Pacific Ocean (to the north of 40° N) manifested as a result of global climate changes at the turn of the XX–XXI centuries, and at assessing their trends and possible causal relationships with the processes in the atmosphere and on the ocean surface. Methods and Results. Based on the Global Meteorological Network and NOAA reanalysis data, the regional features of interannual oscillations of the surface air temperature and their relationship with variations in the fields of pressure, wind and water temperature on the ocean surface, and with climate indices over the past 4 decades were identified. In order to determine the temperature field spatial-temporal structure and to zone the water area according to the features of climate changes, the methods of cluster, correlation analysis and the apparatus of empirical orthogonal functions were used. The results obtained made it possible to characterize the degree of heterogeneity of the studied area response to the ongoing global changes, to identify different domains and to assess quantitatively the warming rate in these water areas. Conclusions. The tendencies of modern warming are manifested in the trends of interannual air temperature variability, on the average, by ~0.20°C/10 years in the subarctic, and indicate significant regional differences (1.5–2 times) in the ongoing changes. In the west of the region, the warming rate is higher than in the east, where the temperature trends are minimal or statistically insignificant. In the warm period of a year, their values are higher than those in the cold period. The alternation phases of the warm and cold periods are consistent with the variation tendencies in the characteristics both of the atmospheric action centers and various climatic parameters. The corresponding correlations are most widely manifested in variations in the empirical orthogonal functions modes of the H500 geopotential field, and the PDO, NP, SOI, PTW, AD and EP/NP indices. Stable anomalies and trends of the ocean surface temperature in the North Atlantic also play an important role in formation of the Та anomalies in the western subarctic.