Warming of polar regions

With global warming, the Arctic and the Antarctic will warm much faster than the Equator as carbon dioxide builds up.

Researchers studying glacial cores from the Greenland Ice Sheet have concluded that local climate shifts occurred with incredible rapidity in the past -- 18 degrees in one three-year stretch. Scientists manning a research station at Toolik Lake, Alaska, 170 miles north of the Arctic Circle, have watched average summer temperatures rise by about seven degrees in the past two decades. It rained briefly at the American base in McMurdo Sound, in Antarctica, during the southern summer of 1997 -- as strange as if it had snowed in Saudi Arabia.

The Arctic tundra has warmed so much that in some places it now gives off more carbon dioxide than it absorbs -- a switch that could trigger a potent feedback loop, making warming ever worse.

Over the past 50 years, the Antartic Peninsula has experienced a sustained atmospheric warming of 4.5 degrees Fahrenheit, sending huge icebergs into the Southern Ocean. In 1995 and 1998, massive pieces of the Larsen Ice Shelf, the size of major cities, broke away. In 2002, th 500 million billion tonne Larsen B ice shelf, with a surface area of 3,250 square km, collapsed in less than a month dumping more ice into the Southern Ocean than all of the previous half century's icebergs combined. Until this event, some 7,700 sq km of coastal ice shelves have disintegrated since 1945 with several major collapses. Two smaller ice shelves, called the Larsen A and the Prince Gustav disintegrated in 1995 after years of shrinking. A smaller ice shelf, the Wordie, disappeared in the late 1980s. Two other ice shelves, the Wilkins and the George VI, are also thought to be on the point of collapse. This progress of break-up is well beyond normal activity and scientiest predict that global warming will melt most of the ice shelves, which border 44 percent of Antartica and cover 580,000 square miles. The production of vast amounts of icebergs is a threat to the world's climate and the way the ocean's function. The fear is that a snowball effect will lead to disintegration of the vast West Antarctic ice shelf, kilometers thick in parts, which would cause the world's oceans to rise by up to five meters.

The Antarctic is normally the source for a large part of the "bottom water" which feeds oxygen to global ocean depths. This dense, rich water has fallen by 20 percent from pre-industrial times. It is predicted that the world's deep ocean circulation system will slow down as a result of global warning. This is expected to cause a 15 percent drop in total global marine phytoplankton production by the end of the century; also in the same time period a halving in the abundance of krill, planktonic crustaceans that are most abundant animal organism on earth and the keystone of the Antarctic ecosystem.