and Abrupt Climate Change
concern about the magnitude and rate of future climate change looms, it becomes increasingly important to understand the mechanisms underlying past abrupt climate change events. A cold event that occurred 8200 years ago, although much less Enhanced online at extreme than some www.sciencemag.org/cgi/...
| Main Authors: | , , , , |
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| Format: | Text |
| Language: | English |
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| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.175.5745 http://pangea.stanford.edu/Oceans/GES205/superlakes.pdf |
| Summary: | concern about the magnitude and rate of future climate change looms, it becomes increasingly important to understand the mechanisms underlying past abrupt climate change events. A cold event that occurred 8200 years ago, although much less Enhanced online at extreme than some www.sciencemag.org/cgi/ events during the Ice content/full/301/5635/922 Ages, is probably most amenable to detailed examination because it is the most recent such event. According to the ice-core record from Greenland, the abrupt cooling 8200 years ago was the largest climate excursion of the past 10,000 years (1, 2): The mean temperature dropped by about 5°C for about 200 years (see the figure, A), snow accumulation decreased sharply, precipitation of chemical impurities increased, and forest fires became more frequent. The event, which affected much of the Northern Hemisphere (3–5), appears to have been triggered by the sudden release of fresh water from a huge, glacierdammed lake that had formed during the deglaciation of North America (6). Changes in the volume and extent of the ice sheets that once covered much of North America directly influenced the freshwater balance of the North Atlantic and are implicated in many abrupt climate events of the past 100,000 years (7, 8). During the last Ice Age, when a kilometers-thick ice sheet covered most of Canada and parts of the northern United States, armadas of icebergs were episodically launched into the North Atlantic. The melting of this freshwater ice and the associated freshening of ocean surface waters are believed to have changed the strength of the oceanic thermohaline circulation (9), thereby causing abrupt climate changes. |
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