Dead whales tell tales of sea ice decline.By delving deep into whaling records going back to the 1930s, an Australian scientist has discovered evidence of a major decline in the amount of sea ice surrounding Antarctica. The ice-covered sea around Antarctica measures about twice the size of the United States United States, officially United States of America, republic (2005 est. pop. 295,734,000), 3,539,227 sq mi (9,166,598 sq km), North America. The United States is the world's third largest country in population and the fourth largest country in area. , and oceanographers regard it as a climatic canary in a coal mine--a sensitive measure of changing conditions. Because satellite records of sea ice only go back to the 1970s, climate scientists have no direct means of assessing long-term changes in the amount of polar sea Polar Sea may have several meanings:
British writer whose delight in the fantasy world of childhood is reflected in his poems and novels, such as Early One Morning (1935). Noun 1. of the Australian Antarctic Division The Australian Antarctic Division (AAD) is a division of the Department of the Environment and Water Resources. This is the Australian Government agency which manages Australia's Antarctic and sub-Antarctic stations and territories as part of the Australian Antarctic Program - in Tasmania in the Sept. 4 Nature. The International Whaling Commission International Whaling Commission (IWC) An intergovernmental organization created in 1946 to control the rapid escalation of whaling. The original purpose of the IWC was to preserve whale stocks for commercial whalers. has 1.5 million records of whale catches since the 1930s. They include the date, the ship's position, and the species captured. De la Mare surmised that he could use these data to track sea ice because many whales congregate around the ice's edge, an area rich in food. For the period 1930 through 1950, de la Mare finds that the sea ice boundary remained stable, averaging around 61.5 [degrees] S. During the early 1950s, the positions of the southernmost catches started drifting south, indicating a reduction in sea ice coverage. Between 1957 and 1971, whalers Whalers may mean:
tr.v. de·plet·ed, de·plet·ing, de·pletes To decrease the fullness of; use up or empty out. [Latin d populations of large whales. In the early 1970s, whalers returned to the south to pursue the smaller minke whales, which accumulate at the sea ice edge. De la Mare found a big change in whaling reports between the 1940s and the 1970s. During the later period, ships made their southernmost catches on average 2.8 [degrees] farther south than in the earlier period. "This suggests a decline in the area of sea ice of some 25 percent," which equals a loss of 5.65 million square kilometers of sea ice, says de la Mare. Some sea ice researchers remain unconvinced. "I find it hard to believe," says H. Jay Zwally of NASAs Goddard Space Flight Center The Goddard Space Flight Center (GSFC) is a major NASA space research laboratory established on May 1, 1959 as NASA's first space flight center. GSFC employs approximately 10,000 civil servants and contractors, and is located approximately 6.5 miles northeast of Washington, D.C. in Greenbelt, Md. Zwally notes that whalers pursued different prey in the 1970s than they did earlier, perhaps explaining some of the change. Furthermore, de la Mare lacks data for the critical interval during the late 1950s and 1960s, when whalers worked away from the ice edge. De la Mare counters that changes in whaling practice cannot explain the observed southward shift. The ultimate cause of the sea ice decline, he says, remains uncertain. Some computer climate models predict that greenhouse warming should increase the amount of Antarctic sea ice, although other models indicate a decline. |
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