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Polar Bears Must Work Harder On Faster Sea Ice Treadmill¹ 奔跑吧!北极熊

Polar bears live on floating rafts of sea ice, hunting for seals. But in the Arctic Ocean north of Alaska, the cold polar wind constantly blows that ice from east to west. Which means that the polar bears there are on a kind of treadmill.

北极熊居住在漂浮的海冰上，搜寻海豹。但是在阿拉斯加北部的北冰洋，寒冷的北极风经常将冰块从东边吹到西边。这样北极熊就好像在跑步机上。

“If the bears don’t compensate² that drift, they would all drift to Russia. So over the course of a year they need to walk back against that prevailing³ drift to remain in the Alaska territories.” David Douglas, a biologist with the U.S. Geological Survey in Juneau, Alaska.

“如果北极熊不走回去原地的话，它们就会漂到俄罗斯了。所以一年里，要想呆在阿拉斯加地区，北极熊要走在这些漂浮物上。”大卫·道格拉斯说到。道格拉斯是朱诺，阿拉斯加州美国地质调查局的一名生物学家。

Recently, researchers realized that the ice drift in this part of the Arctic Ocean has accelerated from about three kilometers per day up to five. That’s probably because climate change has made the sea ice thinner and easier for the winds to push. And that means the polar bear treadmill has sped up too.

最近，科学家们意识到，北冰洋地区冰漂浮的距离从每天3公里增加到了5公里。原因可能是因为气候变化让海冰变薄，更易被风吹动。这也就意味着北极熊的跑步机加速啦。

Douglas and his colleagues tracked Alaskan polar bears fitted with radio collars. They found that the animals are working harder than ever to compensate for the faster drift. And just like when we exercise, bears have to eat more food to make up for the extra calories they’re burning—between one and four more seals per year, depending on whether the bears are single or raising cubs⁴.

道格拉斯和同事们跟踪调查了装有无线线圈的北极熊。他们发现动物们比以往更加努力来弥补漂浮速度加快的海冰。这就像当我们锻炼的时候一样，北极熊不得不摄入更多的食物来补充消耗的额外能量——每年捕食的海豹数量增加一到四只，数量主要取决于北极熊是否是单身，还是在哺育幼崽。

“While that may not seem like a lot of seals or a big demand, it also comes at a time when the habitat that they have to hunt in is shrinking. So they have less area on which to hunt seals, at the same time needing to hunt more.”

“似乎也没有大量的海豹，同时北极熊捕食时所占据的栖息地在减少。所以，它们捕猎海豹的地区减少，而它们却需要捕食更多的海豹。”

Douglas, after presenting the research December 15th at the fall meeting of the American Geophysical Union in San Francisco.

道格拉斯，在12月15日旧金山举办的美国地球物理学会秋季会议上呈现了自己的研究结果。

He’s particularly worried that the changes in sea ice may hurt young bears’ chances of survival, especially in the southern Beaufort Sea, north of Prudhoe Bay. Researchers have studied these bears for more than 30 years, and have watched their numbers decline.

道格拉斯担心海冰的变化可能会减少幼小熊宝宝存活的几率，特别是在南波弗特海,北部的普拉德霍湾一带。研究人员已经研究这些北极熊30多年，他们看着这些北极熊的数量在减少。

“We didn’t see this coming three decades ago when we started tracking bears. We thought we were simply getting baseline data on a population, and never foresaw that the Arctic would undergo such dramatic change.” That, like the sea ice, may be accelerating.

30年前我们开始跟踪观察北极熊，我们并没有预料到现在这种情况。我们原来以为自己收集的仅是基线数据，从来没有预测到北极会经历如此大的变化。例如，北极冰在加速融化。