Word: broecker
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Dates: during 1994-1994
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...number of theories have been floated to explain these irregular, rapid variations. The leading one, advanced by Lamont-Doherty's Wallace Broecker and George Denton of the University of Maine, involves a kind of cyclic ocean current that has been likened to a conveyer belt. Broecker and Denton note that a stream of unusually salty (and thus especially dense) water flows underneath the Gulf Stream as it moves from the tropics to the North Atlantic. When this salty stream reaches the far north, it is forced to the surface as water above it is blown aside by the winds...
...this current, argue Broecker and Denton, that keeps the Arctic relatively warm and glacier free. When it stops running, an ice age -- or a cold spike -- begins. What causes a turnoff? An influx of fresh water might do it, by diluting the saltiness and density of the current, preventing it from sinking and heading back to the tropics. There is evidence that at just the time the Younger Dryas began, a huge North American lake (which no longer exists) began dumping Amazonian quantities of fresh water into the North Atlantic. The discharge stopped about 1,000 years later...
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