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キーワード:
greenland ice
ocean
circulation
records
sediments
event
core
要旨:
The climate system is capable of changing abruptly from one stable mode to another(1-3). Rapid climate oscillations--in particular the Younger Dryas cold period during the last deglaciation--have long been recognized from records throughout the North Atlantic region(4-14), and the distribution of these records at mostly high latitudes suggests that the changes were caused by rapid reorganizations of the North Atlantic thermohaline circulation(6,8,10,15). But events far from the North Atlantic region that are synchronous with the Younger Dryas(16-19) raise the possibility that a more global forcing mechanism was responsible(20). Here we present high-resolution records of laminated sediments of the last deglaciation from the Cariaco basin (tropical Atlantic Ocean) which show many abrupt sub-decade to century-scale oscillations in surface-ocean biological productivity that are synchronous with climate changes at high latitudes. We attribute these productivity variations to changes in or duration of upwelling rate (and hence nutrient supply) caused by changes in trade-wind strength, which is in turn influenced by the thermohaline circulation through its effect on sea surface tempersture(6,21). Abrupt climate changes in the tropical Atlantic during the last deglaciation are thus consistent with a North Atlantic circulation forcing mechanism.
