Abstract

Antarctica is the coldest continent on Earth, with temperatures above freezing rarely occurring beyond the Antarctic Peninsula and some limited regions along the coast of East Antarctica. However, extreme high temperatures in these areas can have a significant impact on the ice shelves, permafrost, terrestrial biota and logistical activities. The long records of in-situ temperature from the research stations provide a means of investigating the mechanisms responsible for record temperatures and their variability and change over recent decades. We have examined temperatures from 17 stations on the Antarctic continent and nearby sub-Antarctic islands, investigating the variability and trends in the number of extreme temperatures, which we took as daily mean temperatures beyond the 5th and 95th percentiles. The majority of record high temperatures were recorded after the passage of airmasses over high orography, with the air being warmed by the Föhn effect. Counterintuitively, at some stations in coastal East Antarctica the highest temperatures were recorded after air with a high potential temperature descended from the Antarctic plateau, resulting in an airmass 5-7°C warmer than the maritime air. The five Antarctic Peninsula stations examined had all experienced a statistically significant increase (p < 0.01) in the number of extreme high temperatures during the late Twentieth Century, although the number of extremes had decreased in subsequent years.