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Slowing the Atlantic Conveyor
The Gulf stream, first mapped by Timothy Folger, Benjamin Franklin's cousin, brings warm water to the north Atlantic and especially to England. That is why London, which is as far north as the southern tip of Hudson's Bay, is warmer than Boston in the winter. It is part of the Atlantic Conveyor shown below. About 10,000 years ago, this shut down and cause a relapse of the last ice age. It is believe that melting polar ice can lead to a shutdown. Not much is know yet about how likely this is, but current models seem to indicate a complete shutdown is quite unlikely this century.
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The result would be more or stronger hurricanes caused by the warmer tropical waters. Because hurricane formation is so sensitive to sea temperature (one degree F may nearly double annual hurricane energy) the impact could be significant.
Europe, and especially England, will become cooler if the Gulf Stream shuts down, and the tropical part of the Atlantic warmer because less warm water will be sent north. Increasing flows of cold fresh water from the melting Arctic are thought to block the northern path of the warm Gulf Stream.
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What Can We See?
Glaciers are melting faster. In 1996, the amount of water produced by melting ice in Greenland was about 90 times the amount consumed by Los Angeles in a year. Last year, the melted ice amounted to 225 times the volume of water that city uses annually. This cold, fresh water of the melting glaciers blocks the gulf stream.
New measurements by NASA satellites of the Antarctic ice sheet show it losing 36 cubic miles of ice a year. Although minimal in terms of rising sea level, it is not what was predicted by an earlier study. "That's a wake-up call. We better figure out what's going on," one glaciologist said.
'Drift ice', which usually closes ports in northern Japan for several months a year, has shrunk by 40 percent. Masaaki Aota, director of the Okhotsk Sea Ice Museum of Hokkaido, said he believed that the most likely cause was global warming, though he added that there was no conclusive evidence. "I don't think this is a problem particular to this place," he said. NYTimes
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What Might Happen?
A slowing of the conveyor currents would the diminish the entire marine food chain. The warm nutrient-rich water encourage plankton production, feeding larger fish. A 20% loss of the humble phytoplankton would have a major repercussions all the way up to the human food supply.
Rising temperatures are also affecting such things as plant and animal habitats, coral reefs' health, hurricane severity, droughts, and globe-girdling currents that drive regional climates.
Drought in the Amazon Changing Atlantic currents may also be among the causes of increases in desertification in Africa, of drought in the Amazon basin.
A cooler Europe could lead, as it did in the "Little Ice Age" to the Thames freezing so thoroughly that people held winter fairs on the ice in London. There were serious crop failures, famines and disease due to the cooler climate.
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http://zfacts.com/p/190.html | 01/18/12 07:18 GMT
Modified: Tue, 18 Apr 2006 00:54:43 GMT
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