Autumn 2012    #17
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Year-round Arctic Ice Set to Disappear in your Lifetime

Map: Record-low extent of sea ice (white) on Arctic waters in September 2012. Purple line: average extent for this month, 1979–2000. Black cross marks the North Pole. Credit: National Snow and Ice Data Center (NSIDC)

        The world of science was astounded when a record amount of ice had melted on the Arctic Ocean by September 2007. But even more ice melted away this year, and by September 16 only 1.4 million square miles of ice cover remained on the Arctic Ocean. That is 49% less than the long-term average for September in the years 1979–2000 (the first twenty years of satellite observation).

       The coastlines of Siberia and Russia, Scandinavia, Alaska, and most of Canada became ice-free by the end of last summer (first figure at left). Compare this summer’s ice cover (white) with the average location of the ice edge from 1979 to 2000 (purple curve), to appreciate the magnitude of the change. Monitoring of ice cover in the Arctic and Antarctic is done by the National Snow and Ice Data Center.

       The volume of Arctic ice has declined faster than its area has, as the thick, multi-year ice rapidly disappears. On the next figure (below, left), the amount of ice is depicted by age class from 1 to 5+ years. The older and thicker ice enables part of the ice pack to survive the summertime melting season. The ice that is 5 or more years old has now largely disappeared. Compared to1983, there is practically no “old ice” left. When spring arrives, more of the Arctic ice pack is thinner than before, and is more prone to melt in the summer.

       The University of Washington estimates that the volume of sea ice has reached an all-time low. Even after more new ice is added in the upcoming winter, they estimate that in 2013 there will only be 20% of the amount of five-year-old ice that was present in 1983.

South of the Equator . . .
       Only ten days after the record low ice cover was observed in the Arctic, an all-time high ice pack was seen in the Southern Ocean. Of course, it’s winter in the South Polar region when it is summer in the far North. The Southern Ocean pack ice surrounding Antarctica has been expanding for years, not so much because the temperature is shifting but because ever-faster winds in the southern hemisphere caused the pack ice to expand northward. Loss of ozone in the stratosphere over Antarctica (the famous "ozone hole") is believed to have caused a stronger jet-stream, which ultimately ramped up wind speeds in the lower atmosphere in that region.

       Let’s compare the changes in ice cover at the two poles. While the Southern Ocean ice cover has grown, the increase has been +6200 square miles per year over the last 32 years, an addition somewhat larger than the state of Connecticut each year. Meanwhile, the Arctic lost 35,500 square miles of ice each year, about the size of the state of Indiana. And the loss has been much faster since the year 2000.

Snow cover in the North has dwindled even faster than sea ice
       While disappearing sea ice has been in the spotlight since 2007, snow cover has been declining in the spring even more rapidly than the summertime ice has in northern latitudes. According to a new report2 by Chris Derksen and Ross Brown, record low snow cover has been observed each spring in the Eurasian Arctic for every successive year since 2008, and in four of the last five years in Arctic Canada and Alaska. The loss of snow in May and June is statistically significant. The decline of June snow cover since 1979 (–21.5% per decade) is twice the rate of loss of Arctic sea ice in September (–11% per decade). Most climate models have not successfully reproduced nor predicted the accelerating snowmelt in the springtime, just as they have not reproduced the recent melting of Arctic sea ice.

        The consequences are not hard to imagine. Wherever and whenever ice or snow covers the surface, they refrigerate the neighborhood where they exist, and effectively counteract global warming by reflecting 80 to 90% of the incoming solar energy back to space. So most of the incoming energy is then lost forever. With less snow on the land in May and June, and less ice covering Arctic waters in late summer, the season when the surface is dark becomes longer than before. Dark surfaces warm up when they absorb sunlight and pass this warmth to the air above. Voila! More global warming ensues in a previously cold region, over a longer summer season. The warming observed in the Arctic has been greater than what was predicted by a variety of global climate models. The consequences of these polar climatic changes are more far-reaching than one might think at first.

1. “Poles apart: A record-breaking summer and winter” at National Snow and Ice Data Center, Boulder, Colorado: .

2. “Spring snow cover extent reductions in the 2008-2012 period exceeding climate model projections” by Chris Derksen and Ross Brown (2012), Geophysical Research Letters, vol. 39, 19, 10 oct. 2012, doi:10.1029/2012GL053387.

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Climate News, October 2012

Record Loss of Sea Ice on Arctic Ocean: Feature article

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Credit La Niña: Sea Level actually fell in 2011 !

CO2 will make West Coast waters too acidic for shellfish, some marine life

       By 2050, in the California current on the US west coast, more than half of the surface waters are projected to become too acidic for shell-building marine life to thrive or survive at certain times of the year. Essentially all water in the bottom layer will not be able to support oysters and shell-building organisms, according to a team of Swiss scientists.

Full Story

Above: Trend of area of ice cover on the Arctic Ocean in five age classes from 1-year-old to 5 (or more) years-old, from 1983 to 2012. The oldest ice has virtually vanished. CREDIT: National Snow and Ice Data Center, Boulder, CO.

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Published at Portland, Oregon, USA
Copyright 2012

 Chief Editor:  Michael A Fortune, Ph.D.


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