Winter Air Temperature Change over the Terrestrial Arctic , 1961 – 1990

We evaluate two approaches to spatially interpolating winter surface air-temperature fields over the terrestrial Arctic from available weather-station records. We then examine 30 yr (1961–1990) of winter air-temperature change over the terrestrial Arctic through a timetrend analysis of interpolated winter air-temperature fields. We used monthly average air temperatures from 4984 Arctic station records that were available for the period 1961– 1990. The two spatial interpolation procedures employed were ‘‘traditional’’ interpolation and a method that makes use of spatially high-resolution digital-elevation information, called ‘‘DEM-assisted’’ (DAI). The Arctic average winter air temperature obtained from the traditionally interpolated 1961–1990 climatology is over 98C colder than the mean winter station temperature, illustrating the considerable warm bias in Arctic weather station locations. The DAI-based average is 18C colder, further emphasizing the importance of spatial interpolation prior to spatial averaging. Over the 30 yr, increases in winter air temperature appear across western Canada and in parts of central Asia, with decreasing trends apparent over eastern Canada. Much of the Arctic exhibits no clear trend, with low explained variances. In western Canada, however, warming trends are on the order of 0.1 to 0.48C yr 1 when the fields analyzed were traditionally interpolated or interpolated using DAI. Explained variances (rs) are higher where trends are largest: approximately 0.2 to 0.4 in western Canada and slightly higher (albeit spuriously) in an isolated area of central Asia. Over the entire terrestrial Arctic, mean winter air temperature has increased at a rate of about 0.058C yr 1 based on traditional interpolation and DAI.