Antarctic Lake Warming

Freshwater lakes at Signy Island, South Orkney Islands, Antarctica. © British Antarctic Survey

According to new findings in a report in the January 25, 2002 issue of Science, winter lake temperatures on an Antarctic island increased by up to 1.3 º C. between 1980-1995, causing extremely fast changes in the lakes' ecology. Signy Island lies at the confluence of the ice-bound Weddell Sea and the warmer Scotia Sea, and its climate is governed by the interaction of cold and warm air masses from the two areas.

Its location, low altitude, and a relatively thin, low-density ice-cap make it sensitive to environmental change. The increase in winter lake temperatures during this time period was three times greater than that of local air temperature, researchers from the U.K. and Canada report.

The amount of time the lakes were frozen over decreased by more than four weeks, allowing the lake water and sediments to absorb more solar energy--which would otherwise have been reflected by the ice. Nutrient levels also rose, Wendy C. Quayle and colleagues report, probably because streams have recently been running over thawed ground, rather than ice. Lake phytoplankton numbers are up as well, the authors found. These trends "indicate that local climate change has been translated into extreme ecological change," they write.

The journal Science is published by the American Association for the Advancement of Science (AAAS).

-- Becky Ham