Arctic sea ice at record low
solonavi
20 September 2007
Global Warming, Habitat
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Even for a society jaded by the continual breaking of climate records, the retreat of Arctic ice this year is stunning.
Sea-ice extent — the total number of 25 x 25 kilometer square sections of ocean covered by at least 15% ice — in the Arctic Ocean melts from about 16 million km2 every March to a minimum sometime in September or October, the exact date normally only being evident in retrospect. The US National Snow and Ice Data Center (NSIDC) says the previous record absolute minimum was 5.32 million km2, set in 2005. This year has already reached 4.14 million km2 — the lowest since records began in the late 1970s.
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Some models suggest that if the current trends continue, we’ll hit a first summer day entirely free of sea ice sometime between 2050 and 2100 1,2 – dates accepted by the Intergovernmental Panel on Climate Change. Other studies predict it could happen even earlier3.
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As well as examining the area over which sea ice is prominent, scientists also look at the actual area of ice. Processing of NSIDC data by researchers at the University of Illinois, Urbana-Champaign, puts the previous 2005 record for area at 4.01 million km2, with this year’s sea-ice area currently at 2.92 million km2.
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Whether global warming should be blamed entirely for this year’s low is not entirely clear. Variation in the factors mentioned by Walsh is not necessarily caused by climate change. But a warmer planet has resulted in thinner ice, which is more vulnerable to warm weather.Â
Initial results from a German survey that were revealed last week show that arctic ice is approximately 50% of its 2001 thickness.
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As well as opening up trade routes, the reduction of sea ice in the north will have consequences on local wildlife too. The most visible example of this will be polar bear populations; newly released reports from the US Geological Survey (USGS) suggest that two-thirds of the bears could be lost within 50 years because of reduced sea ice. Polar bears rely on the ice as a hunting platform and the USGS models predict a 42% loss of habit in the key summer breeding months.
16 Sept 2007: the long-term average summer sea ice extent is shown by the pink line, today’s ice extent is shown in white.
National Snow and Ice Data Center
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