Room to breathe?
Sea ice in the Arctic is decreasing, right? That’s certainly true overall: 9 percent of the “perennial” ice and 3 percent of the annually formed ice have been disappearing each decade for the past quarter century. But in some areas the ice has been increasing. One such area is Baffin Bay, between Canada and Greenland. The bay is home to the world’s greatest concentration of narwhals, and for them an increase in ice is a big problem.
Narwhals–small whales that live in the High Arctic–are noted for the males’ long, lone tusk. Sensibly, they migrate south in winter. “South,” however, is no farther than the middle of Baffin Bay, which is mostly covered in dense pack ice from December through March. At present the ice still has enough leads and cracks so that the narwhals can breathe. But Kristin L. Laidre and Mads Peter Heide-Jorgensen of the Greenland Institute of Natural Resources have found that the winter ice cover in the narwhals’ northernmost wintering grounds in Baffin Bay increased by 0.04 percent a year between 1978 and 2001.
That may not sound like much, but from mid-January until mid-April less than 3 percent of the narwhals’ wintering grounds are open water. The icing trend could become disastrous for the narwhals. Not only will they run the risk of getting trapped in the ice, but there will also be fewer places from which they can dive for one of their main winter foods: the halibut that live at depths of more than 3,000 feet. (“Arctic sea ice trends and narwhal vulnerability,” Biological Conservation 121:509-17, 2005)
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