RAPID CLIMATE-CHANGE IN THE NORTH-ATLANTIC DURING THE YOUNGER-DRYAS RECORDED BY DEEP-SEA CORALS

Research on global climate change has increasingly focused on rapid (c entury-scale and decadal) changes. One such climate shift, the Younger Dryas cooling event(1), took place during the last deglaciation, from 13,000 to 11,700 years BP. Climate records from Greenland ice cores a nd North Atlantic sediment cores show high-frequency fluctuations impl ying significant (>5 degrees C) shifts in temperature at this time, ta king place within 50-100 years (ref. 2), The origin of the Younger Dry as has recently been attributed to a reduction or cessation of deep-wa ter production in the North Atlantic and a concurrent lessening of the heat flux from Low latitudes(3,4), The role of intermediate waters (1 ,000-2,000 m depth) is less certain, however, because climate proxies for this ocean reservoir are rare and ambiguous. Here we report on the use of a new climate archive, deep-sea corals from Orphan knoll (1,60 0 m depth) in the northwestern Atlantic Ocean. The oxygen isotope rati os in the coral skeletons (accurately dated by the Th-230/U-234 chrono metric method) change markedly coincident with the initiation of the Y ounger Dryas, suggesting that there were profound changes in intermedi ate-water circulation at this time.