According to both NASA and The National Snow and Ice Data Center (NSIDC), February 2013 marked the fifth lowest sea ice winter in 35 years in the Arctic Ocean. This news follows the striking summertime results for 2012 which revealed that the northern hemisphere’s polar ice coverage shrank to its lowest extent on record last September.
NASA’s satellite data monitors the areas of the Arctic Ocean in which at least 15% of the ocean’s surface is covered in ice. Particular attention is paid to the summer minimum extent and the winter maximum extent, both of which have been in sharp decline over the past 35 years. In fact, between 1979 and 2000 the average extent of ice cover during summertime shrank by approximately fifty percent. Bearing this in mind, many specialists are now predicting that a mere few decades from now, the Arctic Ocean will be ice-free during the summer months.
Newer trends demonstrate that winter ice will soon be in as dramatic a decline as summer ice. In the cold and dark winter months, the sea ice refreezes reaching its maximum extent usually around late February or early March. Yet, nine out of ten of the lowest winter maximums have happened during the last ten years and the winter extent recorded for 2013 is 144,402 square miles below the average annual maximum extent for the last 30 years. Using a methodology which disregards all areas of open water between the ice floes and measures only the surface area of ice, analysts’ found that in winter 2013, the maximum was 5.53 million square miles: also the fifth smallest since 1979.
Scientists attribute the diminishing ice reserves to the effects of global warming. More carbon emissions mean more greenhouse gases pervade the earth’s atmosphere and heat up the overall surface temperature of the earth, causing the ice to melt. The depletion of winter ice is particularly indicative of this. “The Arctic region is in darkness during winter and the predominant type of radiation is long-wave or infrared, which is associated with greenhouse warming,” said Joey Comiso, senior scientist at NASA Goddard Space Flight Center, and a principal investigator of NASA’s Cryospheric Sciences Program. “A decline in the sea ice cover in winter is thus a manifestation of the effect of the increasing greenhouse gases on sea ice.”
Oceanographers are also worried by the trends seen in ‘multi-year’ ice. This type of ice is older and thicker, surviving at least two melt seasons and protecting the polar ice cap from severe melting during the sunny summer months. Despite growing slightly this past winter, this multi-year ice has been rapidly decreasing; its present extent less than half of what it was in the early 1980s.
While Arctic Ice is shrinking, Antarctic Ice has grown by more than 5%. Although this may seem to shed doubt on the global-warming model, specialists say it is actually one of its effects. Warmer water 100m below the surface is causing surface water to cool and thus more ice to form. Richard Bintanja and colleagues at the Royal Netherlands Meteorological Institute have used models and measurements to show that deep warm water is melting the shelves of floating ice that extend from the continent. This, they say, is setting off flotillas of icebergs and creating a layer of cool, fresh water at the ocean’s surface. This has caused disputes between scientists about what the long term effects of this will be. Some think it will result in higher snowfall and that sea levels will actually reduce because more water is kept on land in the form of snow. Others, meanwhile think the opposite: snowfall will decrease, and sea levels will rise.
Either way, both poles are doing their best to show is that climate change is really occurring and that it is likely to continue, propelling the earth towards an ever warmer and more uncertain future.
Sources include: New Scientist; RedOrbit
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