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Friday, March 20, 2009

Arctic sea ice minima and conditions discussed by experts: W. Maslowski, Peter Wadhams, David Phillips, Walt Meier,

Recent expert statements concerning Greenland and the Arctic sea ice


Associate professor Carl Egede Bøggild, University Centre in Svalbard was quoted by The New York Times as saying the melting rate of Greenland’s ice sheet could be as high as 80 cubic miles per year.

Leif Toudal Pedersen of the Danish National Space Center commented about Arctic sea ice: “The strong reduction in just one year certainly raises flags that the ice (in summer) may disappear much sooner than expected….” The International Ice Charting Working Group issued a statement that the Arctic sea ice in September 2007 had reached the lowest extent “in the history of ice charting.”

Arctic Sea Ice September Trend 1979-2007, showing the historic September 2007 minimum (from NSIDC)

A 2007 study by Professor Wieslaw Maslowski at the U. S. Naval Postgraduate School, Monterey, California, predicted that the Arctic Ocean may be free of ice during summer by as soon as 2013. The study used data sets from 1979 to 2004 and did not include the more recent record low ice minima set in 2005 and 2007. Maslowski suggested that other researchers seriously underestimated some key melting processes, producing models that predict an ice free Arctic Ocean to first occur from 2040 to 2100.

Professor Peter Wadhams from University of Cambridge, UK, agreed that some models have not been taking proper account of the physical processes occurring in nature. He said that Maslowski’s model is more efficient because it takes account of processes that happen internally in the ice. Wadhams predicted that, in the end, the Arctic ice will just melt away quite suddenly, perhaps not as early as 2013 but much earlier than 2040.

In December 2007, the Canadian Press selected Arctic shrinkage as Canada’s biggest environmental story of the year. Environment Canada senior climatologist David Phillips summed it up: “This huge chunk of ice the size of Ontario vanished within one year.”


Arctic Sea ice age in February 2008, (right), compared to the average for 1985-2000, (left) (NASA)

Arctic Sea ice composition by age 1985-2008 (NASA)

These maps show the date of first melting of the sea ice in the Arctic Ocean for the years 2005, 2006, 2007, and 2008 up to June 18. They show that in 2008 the sea ice started melting sooner than previous years, including 2005 and 2007 which saw the sea ice melt to a record minimum extent. From NSIDC

According to Walt Meier of the National Snow and Ice Data Center (NSIDC), NASA satellite data shows that there has been a 50% decrease of perennial Arctic ice between February 2007 and February 2008.

While the cold winter did allow ice to re-cover much of the Arctic Sea surface area during the Winter of 2007/2008, conditions were far from normal as the pair of NASA images to the right reveals. The February 2008 ice pack contained much more young ice than the long-term average, and the total volume was arguably the lowest on record. In the past, more ice survived the summer melt season and had the chance to thicken over the following winter. In the mid- to late 1980s, over 20% of Arctic sea ice was at least six years old; in February 2008, just 6% of the ice was six years old or older.

NSIDC says

Arctic sea ice extent during the 2008 melt season dropped to the second-lowest level since satellite measurements began in 1979, reaching the lowest point in its annual cycle of melt and growth on September 14, 2008. Average sea ice extent over the month of September… was 4.67 million square kilometers… The record monthly low, set in 2007, was 4.28 million square kilometers… the now-third-lowest monthly value, set in 2005, was 5.57 million square kilometers… The 2008 season strongly reinforces the thirty-year downward trend in Arctic ice extent. The 2008 September low was 34% below the long-term average from 1979 to 2000 and only 9% greater than the 2007 record… Because the 2008 low was so far below the September average, the negative trend in September extent has been pulled downward, from –10.7 % per decade to –11.7 % per decade.

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