Role of Polar Amplification in Long-Term Surface Air Temperature Variations and Modern Arctic Warming

This study uses an extensive dataset of monthly surface air temperature (SAT) records (including previously unutilized) from high-latitude (>60 degrees N) meteorological land stations. Most records have been updated by very recent observations (up to December 2008). Using these data, a high-latitude warming rate of 1.36 degrees C century(-1) is documented for 1875-2008-the trend is almost 2 times stronger than the Northern Hemisphere trend (0.79 degrees C century(-1)), with an accelerated warming rate in the most recent decade (1.35 degrees C decade(-1)). Stronger warming in high-latitude regions is a manifestation of polar amplification (PA). Changes in SAT suggest two spatial scales of PA-hemispheric and local. A new stable statistical measure of PA linking high-latitude and hemispheric temperature anomalies via a regression relationship is proposed. For 1875-2008, this measure yields PA of similar to 1.62. Local PA related to the ice-albedo feedback mechanisms is autumnal and coastal, extending several hundred kilometers inland. Heat budget estimates suggest that a recent reduction of arctic ice and anomalously high SATs cannot be explained by ice-albedo feedback mechanisms alone, and the role of large-scale mechanisms of PA of global warming should not be overlooked.