Longterm Changes In Arctic Air Temperature

Anomalies of mean annual surface air temperature (SAT) in the zone from 70-85°N for the period from 1900 to 2003 were used to analyze climatic changes observed in the Arctic Seas throughout the last century. The anomalies were calculated on the basis of the archive of mean monthly air temperature in a grid consisting of cells (5° of latitude x 10° of longitude) drawn in the area from 20°N to 85°N for 1891-2000. These data are based on the SAT charts of the Northern Hemisphere constructed at the Main Geophysical Observatory in St. Petersburg, Russia, using all known data published in various climatologic summaries. In the late 1970s, the air temperature data were digitized by the USSR Hydrometeorological Center and updated using Hydrometeorological Center and AARI Department of Long-Range Weather Forecasting data.

Periodic cooling and warming events are evident in air temperature fluctuations in the Arctic during the twentieth century, similar to the changes in the ice cover

AT/C

AT/C

1900 1910 1920 1930 1940 1950 1960 1970 1960 1990 2000

Figure 4.1. Changes in mean annual air temperature anomalies (AT) in °C in the 70-85oN zone in the twentieth and early twenty-first centuries and their polynomial trend.

1900 1910 1920 1930 1940 1950 1960 1970 1960 1990 2000

Years

Figure 4.1. Changes in mean annual air temperature anomalies (AT) in °C in the 70-85oN zone in the twentieth and early twenty-first centuries and their polynomial trend.

discussed above (Figure 4.1). A cool period at the beginning of the century was replaced by warming in the 1920s-1940s that is referred to in climatic literature as the "Arctic warming period." Then, a relatively cooling trend was observed from the late 1950s to the late 1970s, which was in turn replaced by a new warming trend at the end of the century when the temperature reached its maximum in the late 1990s to the early 2000s. The trend seen in Figure 4.1 approximated by a polynomial to the sixth power, suggests that the duration of this cycle is about 50-60 years.

The interpretation of a 50-60 year cycle as the main climatic fluctuation in the Arctic in the twentieth century is also supported by the wavelet-spectrum of mean annual air temperature anomalies, from which a linear trend was deduced (Figure 4.2, see color section). Figure 4.2 quite clearly shows the main features of surface air temperature variability in the high-latitude zone with alternation of cold and warm phases in a 60-year cycle.

Fluctuations of mean air temperature in the Northern Hemisphere (Minobe, 1997, Klyashtorin and Lyubushin, 2004), the Earth's rotation speed (Rudyaev et al., 1985), ice export from the Arctic Basin (Gudkovich et al., 2007), and other indicators also reflect this cycle. Their global nature is apparent in paleoclimate data from ice cores collected at Vostok station in Antarctica, which were analyzed for the isotopic composition of atmospheric precipitation for the last 200 years. (Lipenkov et al., 2002, 2003; Figure 4.3).

Figure 4.1 shows the changes in mean annual twentieth century air temperature anomalies in the high-latitude zone of the Northern Hemisphere as well as "60-year"

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