Watts Up With That?
Wednesday, August 19, 2009
From NSIDC sea ice news
During the first half of August, Arctic ice extent declined more slowly than during the same period in 2007 and 2008. The slower decline is primarily due to a recent atmospheric circulation pattern, which transported ice toward the Siberian coast and discouraged export of ice out of the Arctic Ocean. It is now unlikely that 2009 will see a record low extent, but the minimum summer ice extent will still be much lower than the 1979 to 2000 average.
Figure 2. The graph above shows daily sea ice extent as of August 17, 2009. The solid light blue line indicates 2009; the solid dark blue line shows 2008; the dashed green line shows 2007; and the solid gray line indicates average extent from 1979 to 2000. The gray area around the average line shows the two standard deviation range of the data. Sea Ice Index data.
Figure 1. Daily Arctic sea ice extent on August 17 was 6.26 million square kilometers (2.42 million square miles). The orange line shows the 1979 to 2000 median extent for that day. The black cross indicates the geographic North Pole. Sea Ice Index data. About the data. <!–Please note that our daily sea ice images, derived from microwave measurements, may show spurious pixels in areas where sea ice may not be present. These artifacts are generally caused by coastline effects, or less commonly by severe weather. Scientists use masks to minimize the number of “noise” pixels, based on long-term extent patterns. Noise is largely eliminated in the process of generating monthly averages, our standard measurement for analyzing interannual trends. Data derived from Sea Ice Index data set. –>
Note: This mid-monthly analysis update shows a single-day extent value for Figure 1, rather than the usual monthly average. While monthly average extent images are more accurate in understanding long-term changes, the daily images are helpful in monitoring sea ice conditions in near-real time.
Overview of conditions
On August 17, Arctic sea ice extent was 6.26 million square kilometers (2.42 million square miles). This is 960,000 square kilometers (370,000 square miles) more ice than for the same day in 2007, and 1.37 million square kilometers (530,000 square miles) below the 1979 to 2000 average. On August 8, the 2009 extent decreased below the 1979 to 2000 average minimum annual extent, with a month of melt still remaining.
Conditions in context
From August 1 to 17, Arctic sea ice extent declined at an average rate of 54,000 square kilometers (21,000 square miles) per day. This decline was slower than the same period in 2008, when it was 91,000 square kilometers (35,000 square miles) per day, and for the same period in 2007, when ice extent declined at a rate of 84,000 square kilometers (32,000 square miles) per day. The recent rate of ice loss has slowed considerably compared to most of July. Arctic sea ice extent is now greater than the same day in 2008.
AMSRE from JAXA shows similar extent conditions:
As does NANSEN:
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