Antarctic climate cooling and terrestrial ecosystem response

The average air temperature at the Earth's surface has increased by 0.06degreesC per decade during the 20th century(1), and by 0.19degreesC per decade from 1979 to 1998(2). Climate models generally predict amplified warming in polar regions(3,4), as observed in Antarctica's peninsula region over the second half of the 20th century(5-9). Although previous reports suggest slight recent continental warming(9,10), our spatial analysis of Antarctic meteorological data demonstrates a net cooling on the Antarctic continent between 1966 and 2000, particularly during summer and autumn. The McMurdo Dry Valleys have cooled by 0.7degreesC per decade between 1986 and 2000, with similar pronounced seasonal trends. Summer cooling is particularly important to Antarctic terrestrial ecosystems that are poised at the interface of ice and water. Here we present data from the dry valleys representing evidence of rapid terrestrial ecosystem response to climate cooling in Antarctica, including decreased primary productivity of lakes (6-9% per year) and declining numbers of soil invertebrates (more than 10% per year). Continental Antarctic cooling, especially the seasonality of cooling, poses challenges to models of climate and ecosystem change.