NSIDC: Early Sea Ice Melt Onset, Soaring North Pole Temperatures, Presage Rapid 2011 Summer Decline

Daily Arctic sea ice extent as of July 17, 2011, along with daily ice extents for previous low-ice-extent years. Light blue indicates 2011, dashed green shows 2007, dark blue shows 2010, and dark gray shows the 1979 to 2000 average.

As the country swelters, ice and snow melt in the North.   The National Snow and Ice Data Center has just issued an update on this year’s version of the Arctic death spiral, concluding:

Arctic sea ice extent declined at a rapid pace through the first half of July, and is now tracking below the year 2007, which saw the record minimum September extent. The rapid decline in the past few weeks is related to persistent above-average temperatures and an early start to melt.

In fact, “air temperatures over the North Pole were 6 to 8 degrees Celsius (11 to 14 degrees Fahrenheit) higher than normal.”

The NSIDC also published a helpful backgrounder, “Heading towards the summer minimum ice extent, on NSIDC’s new Icelights: Your burning questions about ice and climate.” It quotes NSIDC researcher Walt Meier explaining that while  individual years may  fluctuate, “the overall long-term trend will continue downward.”

Here are more excerpts from the sea ice update:

Overview of conditions
As of July 17, 2011, Arctic sea ice extent was 7.56 million square kilometers (2.92 million square miles), 2.24 million square kilometers (865,000 square miles) below the 1979 to 2000 average. Sea ice is particularly low in the Barents, Kara, and Laptev Seas (the far northern Atlantic region), Hudson Bay and Baffin Bay.

Conditions in context
Arctic sea ice extent declined rapidly through the first two weeks of July, at a rate averaging nearly 120,000 square kilometers (46,000 square miles) per day. Ice extent is now tracking below the year 2007, which saw the record minimum September extent.Early start to Arctic melt

When sea ice starts to melt in spring, small ponds known as melt ponds form on its surface. The small pools create a darker surface (a lower albedo) that fosters further melt. How early sea ice melt starts is one indicator of how much the ice will melt in a given year. New research by Don Perovich and colleagues shows that an early start to sea ice melt increases the total amount of sunlight absorbed through the melt season.Data processed by researchers Thorsten Markus and Jeffrey Miller at the NASA Goddard Space Flight Center reveal that melt began earlier than normal in both the Chukchi Sea, just north of the Bering Strait, and the Barents, Kara, and Laptev seas. Surface melting on the sea ice began from two weeks to two months earlier than the 1979 to 2000 average in these areas. However, in Baffin Bay and Hudson Bay, a cool spring led to a later start for surface melt, especially in Hudson Bay. Subsequent warm conditions have nevertheless led to rapid ice melt.

figure 4: melt onset map of Arctic

This map shows the difference between average date of melt onset, when ice melt starts, and the date of melt onset this year. Red indicates earlier than normal melt, blue shows later than normal melt. The darkest red is an anomaly of 50 days early or more. White areas show no anomaly, that is they melted no earlier or later than normal. The gray area over the North Pole indicates where no data are available.

Low summer snow cover in the Northern Hemisphere
As noted in our May 4 post, snow cover in central Russia retreated early in response to warm conditions this spring. Updated analyses provided by the Global Snow Cover Lab at Rutgers University reveal that snow cover remained very low for May and June. Even though some mountain regions in the U.S. and Canada saw greater-than-normal snow cover, snow cover for the Northern Hemisphere as a whole for May and June was the second lowest since the start of snow cover records in 1966.According to David Robinson, head of the Rutgers Snow Cover Lab, a new pattern is emerging in which the Northern Hemisphere is cloaked in above-average snow during late autumn, winter, and early spring, followed by rapid melt and retreat in May and June. While snow cover varies from year to year, the far north has seen a clear trend towards less spring snow cover over the last thirty years.

The Arctic’s death spiral continues.

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