Thats because the thick ice ridges could prevent ringed seals, the bears major prey, from creating breathing holes they need to survive in the frigid waters, Crockford told CNSNews.com. Prompted by reports of the heaviest sea ice conditions on the East Coast in decades and news that ice on the Great Lakes is, for mid-April, the worst its been since records began, I took a close look at the ice thickness charts for the Arctic, Crockford noted in her Polar Bear Science blog on April 18th. Sea ice charts arent a guarantee that this heavy spring ice phenomenon is developing in the Beaufort, but they could be a warning, she wrote, noting that they "don't bode well" for the Beaufort bears.
What happens is that really thick ice moves in because currents and winds from Greenland and the Canadian islands push it against the shore, Crockford told CNSNews.com. The male seals arrive in the area in early spring to set up breeding territories. They drill a hole through the ice to maintain breathing holes close to the shore. But theres a limit. They can drill through two meters (about seven feet) of ice. But too much beyond that and theyre in trouble. The reason thats important is that seals mate right after the pups, who are born in April, are weaned. So the male seal wants to be there, but he has to have breathing holes. If the ice is too thick, he has to move off someplace else, she explained.
Female polar bear with cubs.
But this is the same time that female polar bears are just emerging with their newborn cubs from maternity dens either on or near the shore. When those bears come out of their dens in the spring, they need to find seals right away because they will have gone six months without eating, Crockford said. If there are no seals, they have to go further out, where theres thinner ice. Spring and early summer are really a critical time for polar bears. Thats when they need to eat as many seals as they can because thats when they put on fat for the rest of the year. If they have trouble doing that in the spring, theyre in big trouble.
There were comparably high levels of spring ice in the Beaufort Sea in 2004 and 2006, when bear counts were one of the pieces of evidence used to have the bears listed as threatened in the U.S., Crockford pointed out. Polar bear biologists were finding some bears quite thin and found a population decline, she said, which they attributed to melting summer ice caused by global warming. But the biologists were not there to see the thick [spring] ice. All they saw was thin bears, she pointed out. They blamed the poor condition of the bears on summer ice, instead of acknowledging that it was likely the condition of the ice in the spring that was the cause of the problem. Female [polar bears] with cubs having trouble feeding are one aspect of the repercussions of thick ice, Crockford added. The other repercussion is that other bears, instead of hanging around and starving, probably left the area. They could have gone to the Chukchi Sea, which is located between the U.S. and Russia near the Bering Strait.
MORE
