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Thursday, January 7, 2010

Joseph Romm: Where on Earth is it unusually warm? Greenland and the Arctic Ocean, which is full of rotten ice

Where on Earth is it unusually warm? Greenland and the Arctic Ocean, which is full of rotten ice

New study supports finding that "the amount of [multi-year] sea ice in the northern hemisphere was the lowest on record in 2009"

by Joseph Romm, Climate Progress, January 6, 2010 Arctic warmth
Map of air temperature anomalies for December 2009, at roughly 3,000 feet above surface, Areas in orange and red are warm anomalies, areas in blue and purple are cool.
It’s cold here and in northern Eurasia, but it’s been positively toasty ar0und the Arctic circle — thanks to an extreme negative phase of the Arctic Oscillation, as the National Snow and Ice Data Center (NSIDC) explained in their online report yesterday.
The temperatures reported by NSIDC show some Arctic anomalies exceeding 7°C (13°F)!  That’s not good news for the kind of re-freezing one wants to see in the otherwise rapidly melting Greenland ice sheet (see Nature: “Dynamic thinning of Greenland and Antarctic ice-sheet ocean margins is more sensitive, pervasive, enduring and important than previously realized”).  It’s also one reason “December 2009 had the fourth-lowest average ice extent for the month since the beginning of satellite records, falling just above the extent for 2007. The linear rate of decline for December is now 3.3% per decade.”
Significantly, a new study, “Perennial pack ice in the southern Beaufort Sea was not as it appeared in the summer of 2009” by Barber et al. finds that all the crowing by the anti-science crowd about the supposed “recovery” of Arctic sea ice was quite premature:

In September 2009 we observed a much different sea icescape in the Southern Beaufort Sea than anticipated, based on remotely sensed products. Radarsat derived ice charts predicted 7 to 9 tenths multi-year (MY) or thick first-year (FY) sea ice throughout most of the Southern Beaufort Sea in the deep water of the Canada Basin. In situ observations found heavily decayed, very small remnant MY and FY floes interspersed with new ice between floes, in melt ponds, thaw holes and growing over negative freeboard older ice. This icescape contained approximately 25% open water, predominantly distributed in between floes or in thaw holes connected to the ocean below. Although this rotten ice regime was quite different that the expected MY regime in terms of ice volume and strength, their near-surface physical properties were found to be sufficiently alike that their radiometric and scattering characteristics were almost identical.
Yes, satellite (and other) measurements of Arctic sea ice extent were apparently deceived.   You might even say that an unfortunate trick of Nature helped hide the decline of Arctic ice:
This case of mistaken identity is physically explained by the factors which contribute to the return to Radarsat-1 from the two surfaces; both ice regimes had similar temperature and salinity profiles in the near-surface volume, both ice types existed with a similar amount of open water between and within the floes, and finally both ice regimes were overlain by similar, recently formed new sea ice in areas of negative freeboard and in open water areas. The fact that these two very different ice regimes could not be differentiated using Radarsat-1 data or in situ C-band scatterometer or microwave radiometer measurements, has significant implications for climate studies and for marine vessel navigation in the Canada Basin.
I had blogged on Barber’s work when it was first reported by Reuters in November (see “Arctic ice reaches historic seasonal low; “We are almost out of multiyear sea ice in the northern hemisphere”):
The multiyear ice covering the Arctic Ocean has effectively vanished….
“I would argue that, from a practical perspective, we almost have a seasonally ice-free Arctic now, because multiyear sea ice is the barrier to the use and development of the Arctic,” said Barber [Canada's Research Chair in Arctic System Science at the University of Manitoba].
Barber and his team thought they’d find “a huge multiyear ice pack that should have been in the Beaufort Sea” but
Instead, his ice breaker found hundreds of miles of what he called “rotten ice” — 50-cm (20-inch) thin layers of fresh ice covering small chunks of older ice.
“I’ve never seen anything like this in my 30 years of working in the high Arctic … it was very dramatic,” he said.
And now we have the Geophysical Research Letters paper by Barber et al., which concludes:
Our results are consistent with ice age estimates (Fowler and Maslanik, that show the amount of MY sea ice in the northern hemisphere was the lowest on record in 2009 suggesting that MY sea ice continues to diminish rapidly in the Canada Basin even though 2009 areal extent increased over that of 2007 and 2008.
This study suggests that the Arctic continues to lose area — and, more importantly, volume — at a much more rapid pace than any major climate models had suggested.  I’ll end with this figure of mean monthly Ice Volume for the Arctic Ocean from a release by several scientific institutions:
Arctic Volume
I still like my odds on a 90% ice free Arctic by 2020 (see “Another big climate bet — Of Ice and Men“).  By then, I assume they’ll have figured out how to deal with Nature’s sea-ice-decline-hiding trick — or there will simply be too little ice for anybody to be fooled.
For more, see “Looking for Above Normal Temperatures? They are in the Arctic.
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