Recently, global warming has become a cause of concern to many. Of particular concern is the potential loss of the ice sheets found in the polar regions of the earth. The loss of land ice in Antarctica, Alaska and Greenland would lead to a global rise in sea level, threatening coastal regions around the world with flooding.

In 1980, the meteorological scientists Syukuro Manabe and Ronald Stouffer popularized the phrase Arctic Amplification or Polar Amplification in their study on the possible effects of global warming. The term only applies to warming at the surface of the earth, not higher up in the atmosphere.

The theory behind arctic amplification is that the effects of global warming are more marked in the polar regions than in other areas of the globe. The ice sheets in the polar regions have a high albedo. This causes the polar ice sheets to reflect the sun's rays instead of absorbing them. As the global warming causes the loss of polar ice, more of the sun's energy is absorbed in the polar regions, causing more ice to melt. This sets up a positive feedback loop, amplifying the effects of global warming in the extreme northern and southern latitudes.

In 2005, a report from the Arctic Climate Impacts Assessment (ACIA) examined evidence for this theory from the previous 100 years. It stated, "Over the past 100 years, it is possible (33-66% confidence) that there has been polar amplification, however, over the past 50 years it is probable (66-90% confidence)."

Recently, there has been an increased concern on the possibility that arctic amplification will reach a tip point, resulting in the loss of most of the arctic ice with a resulting rise in sea level. Evidence for these concerns has come from three well-respected sources.

NASA measures the amount of land ice via satellites. Using this data, NASA has estimated that more than 2 trillion tons of land ice has melted since 2003. This ice has been lost from Alaska, Greenland and Antarctica. Of these, Greenland has suffered the greatest loss of land ice from its ice cap.

The World Meteorological Organization, one of the United Nations organizations, maintains a database of measurement of the volume of the arctic ice sheet. In 2008, it reported that the sheet was the thinness since recordkeeping began.

Finally, the National Snow and Ice Data Center based in Colorado has taken temperature measurements during the fall of 2008 in the arctic region north of Alaska. These temperatures are 9 to 10 degrees above the average values expected at that time of year.

Reference sources:

ACIA 2005. Arctic Climate Impacts Assessment, Cambridge University Press, New York, U.S.

US News World Report

AOS Faculty Profile: Syukuro Manabe

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