Trackers on Ice

Just because a scientist puts a GPS tracking collar on a wild polar bear does not mean the animal will willingly keep it on.   _______, these huge collars are purposefully loose so that if one becomes annoying, a bear can _______it. But scientists have now found a way to use signals from the discarded(丢弃的)devices.

“These dropped collars_______would have been considered garbage data,” says Natasha Klappstein, a polar bear researcher at the University of Alberta. She and her colleagues instead used_______from such collars, left on sea ice in Canada's Hudson Bay, to track the ice itself. For their study, published in June in The Cryosphere, the researchers _______twenty collars that sent movement data consistent(与······一致的)with ice drift rather than polar bear _______between 2005 and 2015. The resulting records of how melting ice typically drifts in Hudson Bay are unique; there are no easily _______on-the-ground sensors, and satellite observations often cannot _______capture the motion of small ice sheets.

The team compared the discarded collars' movements with widely used ice-drift modeling data from the U.S. National Snow and Ice Data Center (NSIDC). Collar data indicated that the NSIDC model underestimates the speed at which ice moves around in Hudson Bay--as well as the overall _______of drift. Over the course of several months the model could drift away from an ice sheet's location by a few hundred kilometers, the researchers say.

This means the bears may be working harder, when moving against the direction of the ice, than scientists had   ________ .“Since we're underestimating the speed of drift, we're likely underestimating the energetic effort of polar bears," says Natasha Klappstein. The research reveals________insight (洞悉) into how highly mobile ice moves. As melting increases in coming years, such ice will likely become more ________farther north, in the central Arctic. Scientists had known NSIDC data could underestimate drift speeds, but “any time we can find a data ________,it is a good thing.”

Plus,such data could improve predictions about how oil spills or other pollutants may spread in seas ________ with drifting ice, says Walt Meier, a senior NSIDC research scientist,who was not involved in the study. The findings may even ________future NSIDC models. “It's a really nice data set,” Meier says."And certainly one we’ll take consideration.