Kaffeklubben Sø, the world's most northerly lake, was entombed
beneath a near-permanent layer of ice some 2400 years ago. Now
it is beginning to thaw – and some of the organisms that
disappeared from its waters are beginning to return. The finding
is the latest evidence that warmer temperatures in polar regions
can result in rapid ecological changes. Located at 83° 37'
north, on the coastal plain of northern Greenland, the
48-hectare Kaffeklubben Sø looks out over the Arctic Sea. "It's
kind of the end of the earth," says Bianca Perren of the
University of Franche-Comté in Besançon, France. One to two
metres of ice cover the lake year-round, but a "moat" of water
forms around the edge of the lake in summer when average
temperatures rise to 1.6 °C. The lake formed about 3500 years
ago when local precipitation increased, says Perren. A few
species of silica-shelled algae called diatoms lived in the
young lake, but their populations declined as regional
temperatures cooled, and they vanished entirely 2400 years a