Friday, September 2, 2011

The Arctic, Interrupted

We are now in September, the month when the Arctic ice extent typically reaches a minimum.  Time to head north and take a look.

As analyzed by the National Snow and Ice Data Center, the current Arctic sea ice extent at the end August was virtually the same as it was in 2007, when the record minimum of the satellite era was set.

Here's another perspective, showing the current ice extent relative to the 1979–2000 median.

In mid-August, the NSIDC reported that the southern route of the Northwest Passage appeared to largely ice free, although there may have been ice concentrations up to 20% along portions of the route.

Even though 2011 is similar to 2007 in terms of ice extent, the total ice volume depends on both the extent of the areal coverage of the ice and it's thickness.  There is no way to measure volume directly, so computer models are used for estimates.  Because the Arctic sea ice is now thinner, the PIMAS model developed by the University of Washington suggests that the total Arctic sea ice volume will reach an all-time low this year, if it hasn't already.

Here's another way to look at it, where we plot the difference (or anomaly) of the sea ice volume relative to the long-term mean for each day of the year.  This removes the seasonal cycle so we can see the long-term trend.  This clearly shows that 2007 was an impressive minimum at the time, but we are well into new territory in the 2010s.

Little wonder that the race for Arctic treasure has begun.  The Arctic, as humans have known it, is moving into new territory.

For more information, see the NSIDC Arctic Sea Ice News & Analysis and University of Washington Polar Science Center Arctic Sea Ice Volume web pages.  Kudos to these sites for putting such great analyses at our fingertips.

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