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Arctic sea ice “recovers” to its 6th-lowest extent in millennia

 
Iceberg in Arctic

A lonely Arctic iceberg. Photograph: Delphine Star/Getty images

 

Powered by Guardian.co.ukThis article titled “Arctic sea ice “recovers” to its 6th-lowest extent in millennia” was written by Dana Nuccitelli, for theguardian.com on Thursday 19th September 2013 03.43 UTC

As Suzanne Goldenberg reported in The Guardian yesterday, Arctic sea ice appears to have reached its annual minimum extent, at approximately 5.1 million square kilometers. This is the 6th-lowest extent since the satellite record began in 1979.

But in fact, scientists have also reconstructed Arctic sea ice extent data much further into the past. For example, Drs. Walsh & Chapman from the University of Illinois have estimated sea ice extent as far back as the year 1870 using a vast array of data (for example, records kept by the Danish Meteorological Institute and Norwegian Polar Institute, and reports made from ocean vessels). While climate contrarians will sometimes try to argue that Arctic sea ice extent may have reached similar lows to today’s in the 1920s or 1930s–1940s, the data compiled by Walsh & Chapman tell a very different story.

Summer Arctic Sea Ice Extent

Average July through September Arctic sea ice extent 1870–2008 from the University of Illinois (Walsh & Chapman 2001 updated to 2008) and observational data from NSIDC for 2009–2013.

Going back even further in time, a study published in the journal Nature in 2011 used a combination of Arctic ice core, tree ring, and lake sediment data to reconstruct Arctic conditions going back 1,450 years. The result is shown below.

Arctic Sea Ice Extent

Reconstructed Arctic sea ice extent over the past 1,450 years, from Kinnard et al. (2011)

A study published in 2010 by 18 leading Arctic experts examined Arctic records throughout geologic history and concluded,

“The current reduction in Arctic ice cover started in the late 19th century, consistent with the rapidly warming climate, and became very pronounced over the last three decades. This ice loss appears to be unmatched over at least the last few thousand years and unexplainable by any of the known natural variabilities.”

Thus the scientific data and literature indicate that this year’s minimum Arctic sea ice extent is not just the 6th-lowest in the past 34 years, but most likely the 6th-lowest in at least the past few thousand years.

The current Arctic sea ice decline is remarkably rapid, and often referred to as a “death spiral.” As Dr. Julienne Stroeve from the National Snow and Ice Data Center (NSIDC) told The Guardian,

“Overall, the Arctic has lost about 40% of its sea ice cover since 1980. Most scientists believe the Arctic could be entirely ice-free in the summers by the middle of the century – if not sooner.”

 

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