World View of Global Warming

POLAR THAW: Global Warming in the Arctic and Antarctic (continued)

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Climate Change Around the Poles

(continued)  Scientists have extracted cores from deep inside the Antarctic ice cap at Vostok, Siple Dome, Dyer Plateau and elsewhere that show that Antarctica as a whole is relatively stable, with a very slight recent warming. Analyzing these cores of ancient ice reveals there is a strong positive correlation between global atmospheric temperature and carbon dioxide levels. The Vostok record also shows the current level of CO2 -- about 370 ppmv --is higher than it has been for 420,000 years (This is the limit of the ice core, at a depth of about 3700 meters. Other climate records hint there has not been a higher CO2 level for 20 million years).

While the center of Antarctica remains relatively stable, along the peninsula, temperature is much more volatile. Interlocking temperature records estimated from ice cores, ocean sediments, penguin rookery changes, and real-time temperature readings show a very steep temperature rise over the last 50 years - overall 2.50° C, and nearly 5.0° C in the winter. One concern is the apparent increase in the breakup of ice shelves that float over the ocean from the ice cap. The Larsen Ice Shelf, for example, has lost great chunks into the Weddell Sea.

Geologist Eugene Domack and others have extracted deep cores of sediment showing there have been previous periods of ice shelf formation and melt back, but that the current warming trend is very steep.

A big worry about Antarctic warming is that the continent contains most of the fresh water on Earth. Mass melting of continental glaciers could raise oceans many feet. That does not appear imminent, but the giant chunks calving off the ice shelves are possible early warnings. A recent study by scientists using JPL/NASA satellite data shows some glaciers in the Pine Island area of West Antarctica are thinning and melting enough over ten years to add to the global rise in sea level.

The extreme warming during winter has reduced the extent and persistence of Antarctic sea ice, which is critical for biologic activity, especially plankton quantity. Studies are showing that krill, the shrimp-like staple of the Southern Ocean, develop under pack ice, feeding on rich algae and plankton. Thus reduced pack may result in smaller, fewer krill. Less sea ice in summer also means more evaporation from open water leading to more snow on some penguin nesting areas.

Penguins are reacting to these changes, as documented by Dr. Bill Fraser at Palmer Station, the U.S. base on the Peninsula. Adelies are losing population while the number of Chinstraps is increasing along a visible boundary between the species ranges. In the Ross Sea and elsewhere to the south, however, warming has led to an increase in the number of Adelies. In addition, climate change has forced Antarctica's only two vascular plants, to adjust their range and rate of growth.

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