The stampede is on
The Seattle Times carried a disturbing article recently about Pacific walruses. Seems earlier this year, thousands of walruses were killed in the midst of a stampede brought about, according to scientists, by climate change. The disappearance of sea ice caused the poor creatures to crowd onto the shoreline on the Russian side of the Bering Strait. Apparently, walruses can’t swim for long periods unlike seals. They have to heave themselves up onto ice or land to rest but, as the ice is rapidly disappearing, as many as 40,000 walruses made their way to land where they can become extremely skittish and stampede. A polar bear or a helicopter for example will cause a rush. Scientists estimate that as many as 4000 walruses out of a total population of 200,000 may have been crushed, including calves. They are also saying that the stampede matches predictions of what could happen to walruses should the ice recede, but they’re surprised by the magnitude.
By how much has the sea ice receded? Well, apparently sea ice cover fell to a record minimum in September 2007 – 4.13 million sq km, beating the previous low record set in 2005 by 23%. One specific ice mass that has been studied by scientists has slimmed down from being a 3.3m-thick slab of perennial sea ice to just half a metre. The slab lost 70cm off its top and 2.2m off the bottom, which is apparently 5 times what is normally expected. The amount of ice is not the only issue of concern, it’s also the thickness of the ice.
Arctic Ocean surface temperatures are to blame. They were 3.5C warmer than the historical average and 1.5C than the historical maximum. The warming is most likely caused by ice-albedo feedback, which is the heating up of increasing amounts of open water that absorb the sun’s rays. The more ice, the more the sun’s rays are reflected rather than absorbed.
And so ice-free summers are looking a lot closer than we thought and poor walruses may continue to stampede and die. In fact, the Arctic Ocean could be ice-free by 2012 according to scientists.