By Janet Raloff
As rivers empty into seas, freshwater mixes into the vast briny depths to replace water lost to evaporation. Or that’s what’s supposed to happen. But for the past dozen years, scientists now report, a large share of river inflows and sea-ice melt within a large expanse of the Arctic Ocean has effectively pooled with little mixing.
An unusual and persistent pattern of clockwise winds has corralled at least 7,500 cubic kilometers of freshwater within the Beaufort Gyre off northern Canada, reports Laura de Steur, a physical oceanographer with the Royal Netherlands Institute for Sea Research in Texel. The freshwater pool is roughly twice the volume of Africa’s Lake Victoria, one of the largest freshwater bodies in the world.
Ordinarily, wind patterns might foster periods of freshwater accumulation or heavy mixing on scales of no more than five to eight years, de Steur says.