Sunday, May 8, 2011

Dramatic sea level rise expected from faster melting of arctic snow and ice

IPCC in the Axis of Logic, via Environment News Network: Sea levels could rise up to 5 feet by the end of this century, driven by warming in the Arctic and the resulting melt of snow and ice, according to a new study by the International Arctic Monitoring and Assessment Program (AMAP). This is more than two and a half times higher than the 2007 projection of a half to two feet by the Intergovernmental Panel on Climate Change.

“The largest and most permanent bodies of ice in the Arctic – multiyear sea ice, mountain glaciers, ice caps and the Greenland Ice Sheet – have all been declining faster since 2000 than they did in the previous decade, ” according to the Arctic study. “The Arctic Ocean is projected to become nearly ice-free in summer within this century, likely within the next thirty to forty years.”

The Arctic temperature increase and the decline of snow and ice feed upon themselves, in an accelerating feedback loop that is causing more rapid melting and sea level rise. The reflective Arctic ice and snow act as a protective shield, sending solar radiation into space. As the ice and snow disappears it is replaced by darker seawater or land, which absorbs more of the incoming radiation. This absorbed energy is released as heat during the summer months, further adding to Arctic warming, which in turn accelerates melting.

Among the feedbacks of greatest concern is the melting of Arctic permafrost (permanently frozen ground). Circumpolar permafrost regions contain the equivalent of about 6,000 billion tonnes of CO2. As more permafrost melts due to increasing Arctic temperatures, more of the gases that were previously trapped in the frozen ground are released.

According to the report, the temperature in the Arctic permafrost has increased by up to 2˚C over the past two to three decades. This warming has caused the southern boundary for melting permafrost to move steadily northward, by 19 to 50 miles in Russia and by more than 80 miles in Quebec.

The combination of these changes could lead to “run-away” feedbacks that could push past other critical tipping points in Earth’s climate system including the loss of Hindu-Kush-Himalaya-Tibetan glaciers, which provide the head-waters for most major river systems of Asia, (the source of freshwater for hundreds of millions of people), and the die-off of the Amazon forest….

A glacier in Greenland, shot by Mila Zinkova, Wikimedia Commons, under the Creative Commons Attribution-Share Alike 3.0 Unported license

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