Antarctic ice: slippin' and slidin.' (ice sheet movements found irregular in 100,000-year cycle study) (Brief Article)For those worried that global warming global warming, the gradual increase of the temperature of the earth's lower atmosphere as a result of the increase in greenhouse gases since the Industrial Revolution. might send Antarctica's glaciers sliding into the ocean--raising sea levels and provoking massive coastal flooding--there may be good news and bad. A new study suggests rising temperatures may not have any immediate impact on the West Antarctic ice sheet The West Antarctic Ice Sheet (WAIS) is the segment of the continental ice sheet that covers West (or Lesser) Antarctica, the portion of Antarctica west of the Transantarctic Mountains. , the area most prone to collapse. That's good. However, that same study indicates that the ice sheet behaves erratically, sometimes collapsing suddenly without regard to global temperatures.
In an attempt to predict the ice sheet's behavior, Douglas R. MacAyeal of the University of Chicago developed a computer model using data about the ice sheet's underpinnings. He ran his model for 10 consecutive 100,000-year cycles to simulate the impact of changes in surface temperatures and sea levels over 1 million years. MacAyeal was "shocked" to find that the ice sheet collapsed into the ocean at three irregular intervals -- 190,000 years ago, 330,000 years ago, and 750,000 years ago. These collapses did not necessarily correspond with periods of surface warming. "Think of how a yo-yo would behave if you had an uncoordinated un·co·or·di·nat·ed
1. Lacking physical or mental coordination.
2. Lacking planning, method, or organization.
un person operating it," MacAyeal told SCIENCE NEWS. "You'd have a sort of jerky jerky
see biltong. , erratic behavior instead of a nice smooth action. That's what That's What is one of the more idiosyncratic releases by solo steel-string guitar artist Leo Kottke. It is distinctive in it's jazzy nature and "talking" songs ("Buzzby" and "Husbandry"). I saw."
MacAyeal's model uses recently obtained data about the layer of "till" beneath the ice. Till, a muck of ground-up rock and water, acts as a lubricant for the ice sheet, influencing whether it slides into the ocean, he says. The till apparently reacts unpredictably to both surface temperature and heating from inside Earth, MacAyeal reports in the Sept. 3 NATURE.
Polar researcher Cornelis van der Veen at Ohio State University Ohio State University, main campus at Columbus; land-grant and state supported; coeducational; chartered 1870, opened 1873 as Ohio Agricultural and Mechanical College, renamed 1878. There are also campuses at Lima, Mansfield, Marion, and Newark. in Columbus expresses skepticism about the till's role in the ice sheet's behavior. "In [MacAyeal's] model, the velocity of the ice stream is determined by the properties of the till," he says. "Our interpretations indicate that is not the case."