A report from the National Snow and Ice Data Center (http://nsidc.org) has determined that the recent accelerated melting of the Arctic sea ice cap is continuing. The NSIDC said its “Sea Ice Extent” project is “currently tracking at 5.8 million square kilometers (2.24 million square miles), with daily extents running at 700,000 square kilometers (270,272 square miles) below previous daily record lows, a significant decline from past years,”
The report and the accompanying bulletin illustrate the extent to which the ice disappears during summer months with graphs and charts, comparing present and past conditions.
“In September 2005, after four years of lower-than-average fall sea ice extent, scientists using satellite data determined that the Arctic sea ice extent had reached a new record low: 5.32 million square kilometers (2.09 million square miles) versus the long-term average of 7.7 million square kilometers (2.97 million square miles),” said the bulletin.
“In September 2006 sea ice extent was also well below average: 5.9 million square kilometers (2.3 million square miles). Although the 2006 minimum did not break the annual record low, June and July of 2006 set new monthly records–until they were broken this year.”
However, weather patterns in 2007 indicate that the sea ice could be reduced to a lower level than in 2005. “The Arctic is experiencing an unprecedented sixth consecutive year with much less sea ice than normal,” the bulletin continued. The NSIDC also warned that “this year’s sea ice melt season may herald a new and steeper rate of decline.”
The bulletin explained that “sea ice minimum” usually refers to “the month that has the lowest monthly average sea ice extent (all the days of the month averaged together).” In most cases September is the lowest. “However, scientists also watch the absolute minimum, or the day of the year with the lowest ice extent.” This usually happens during the second week of September. “But as of only August 9, sea ice has already sunk below that mile-marker,” said the report. “In fact, the daily extent fell below the long-term average absolute minimum back in mid-July.”
After discussing the rapidity with which the Arctic’s sea ice is melting the NSIDC asked rhetorically – “Why has the melt season progressed so quickly? The answer lies in a combination of high temperatures, changes in the age and thickness of ice, and fluctuations in atmospheric circulations.” The scientists asked readers of the report to “please check back—we’ll address these factors in detail as the melt season progresses.”
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