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Saturday, May 21, 2011

Arctic sea ice volume: The death spiral continues. One-year-old ice in Beaufort Sea now a foot thinner than in 2009

One-year-old ice in Beaufort Sea now a foot thinner than in 2009

by Joseph Romm, Climate Progress, May 19, 2011

In November, Rear Admiral David Titley, the Oceanographer of the Navy, testified that  “the volume of ice as of last September has never been lower…in the last several thousand years.” Titley, who is also the Director of Navy’s Task Force Climate Change, said he has told the Chief of Naval Operations that “we expect to see four weeks of basically ice free conditions in the mid to late 2030s.”

Wieslaw Maslowski of the Naval Postgraduate School has “projected a (virtually) ice-free fall by 2016 (+/- 3 yrs).” Contrary to some reporting, that projection has been unchanged for years, though Maslowski is in the process of creating a more sophisticated model that he expects “will improve prediction of sea ice melt,” as he explained to me recently.

Until then, we have some new observational data of Canadian sea ice thickness and this remarkable figure of sea ice volume since 1979 from Neven’s Arctic Sea Ice Blog, based on data from the University of Washington’s Polar Science Center [click to enlarge]:

Arctic sea ice volume by month in cubic kilometers (with simple quadratic trend lines projecting to zero volume, details here).  The bottom (red) line is September volume.
Compare this to Maslowski’s March 2010 PowerPoint:

Maslowski SMALL
Maslowski’s linear projection is based on a combined model and data trendline focusing on ice volume.  By “ice-free,” Maslowski tells me he means more than an 80% drop from the 1979-2000 summer volume baseline of ~200,000 km³.  Some sea ice above Greenland and Eastern Canada may survive into the 2020s (as the inset in his figure shows), but the Arctic as we’ve known it will be gone.  And irreversibly so — again contrary to some misreporting (see “Polar bear, Arctic sea ice all-but doomed: Misleading Nature cover story misleads the media, public”).

Last month, Maslowski emailed me: “...the sea ice behaviour during the 2009-2011 does not provide arguments to change this projection based on volume trend.”  But he also noted, “There is some indication from the QuickScat data that 2nd and 3rd year ice has increased somewhat in the past couple of years which may imply not so linear decline of arctic ice volume.”

Relatedly, this week, the research aircraft Polar 5 of the Alfred Wegener Institute for Polar and Marine Research “returned from Spring Measurements in the High Arctic” with these observations:
One of the key aspects of the expedition were large-scale sea ice thickness measurements in the inner Arctic, in which researchers of the Alfred Wegener Institute and the University of Alberta cooperated closely. For this purpose they used a four metre long electromagnetic ice thickness sensor, called EM Bird. The Polar 5 towed the sensor on an 80-metre-long rope at a height of 15 metres above the ice surface for the surveys. 
A preliminary evaluation of the measurement results shows that one-year-old sea ice in the Beaufort Sea (north of Canada/Alaska) is about 20-30 cm thinner this year than in the two previous years. In 2009 the ice thickness was 1.7 m on average, in 2010 1.6 m, and in 2011 around 1.4 m. “I expect that this thin, one-year-old sea ice will not survive the melting period in summer,” Dr. Stefan Hendricks assesses the situation.
So we may have some more 2nd and 3rd year ice, but at least some of the Arctic ice is thinner than before.

Whether the Arctic goes virtually ice-free by 2019 — or whether it takes another decade — the outcome is now all but inescapable.  In September, National Snow and Ice Data Center’s director, Mark Serreze, said, The volume of ice left in the Arctic likely reached the lowest ever level this month” and “I stand by my previous statements that the Arctic summer sea ice cover is in a death spiral. It’s not going to recover.”

The death spiral is real — and quite consequential for humanity.  in September, a first-of-its-kind analysis by an international team of 18 top scientists found “less ice covers the Arctic today than at any time in recent geologic history” and this ice loss is “unexplainable by any of the known natural variabilities.”  They concluded:
Reviewed geological data indicate that the history of Arctic sea ice is closely linked with climate changes driven primarily by greenhouse and orbital forcings and associated feedbacks. This link is reflected in the persistence of the Arctic amplification, where fast feedbacks are largely controlled by sea-ice conditions.
A 2008 study led by David Lawrence of the National Center for Atmospheric Research (NCAR) concluded (see “Tundra 4: Permafrost loss linked to Arctic sea ice loss”):

We find that simulated western Arctic land warming trends during rapid sea ice loss are 3.5 times greater than secular 21st century climate-change trends. The accelerated warming signal penetrates up to 1500 km inland...
In other words, if it continues, the recent trend in sea ice loss may triple overall Arctic warming, causing large emissions in carbon dioxide and methane from the tundra this century (for a review of recent literature on the tundra, see “Science stunner: Vast East Siberian Arctic Shelf methane stores destabilizing and venting”; NSF issues world a wake-up call: “Release of even a fraction of the methane stored in the shelf could trigger abrupt climate warming”).  Indeed, Lawrence himself said, “Our study suggests that, if sea-ice continues to contract rapidly over the next several years, Arctic land warming and permafrost thaw are likely to accelerate.”

A February study by NSIDC with conservative assumptions concluded, “Thawing permafrost feedback will turn Arctic from carbon sink to source in the 2020s, releasing 100 billion tons of carbon by 2100.”  The paleoclimate record is not reassuring (see “The methane hydrate feedback revisited”).

The time to act is a while ago, but now is better than later.

h/t Grinzo who notes “The month with the lowest volume, September, has declined from roughly 18,000 km3 to around 4,000 km3….  Remember that 1 km3 of ice weighs 1 billion metric tons.”

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