Reduced meltwater outflow from the Laurentide ice margin during the Younger Dryas

摘要: THE cause of the Younger Dryas cold event, which interrupted last deglaciation, is still a matter debate1. A prevalent hypothesis, proposed by Broecker et al.2 that abrupt climate change was driven decrease in rate North Atlantic Deep Water production, triggered sudden dilution surface water response to diversion Laurentide icesheet melt from Mississippi drainage system St Lawrence river. Here we investigate feasibility this triggering mechanism reconstructing sea-surface temperature, salinity and sea-ice cover records for outlet Gulf into Ocean. These reconstructions—based on dinoflagellate-cyst assemblages3,4 sediment cores region—show reduced meltwater runoff, low temperatures extensive during Dryas, dated here between 10,800 10,300 BP. Meltwater pulses did occur before after event: as early 11,700 BP, development Champlain Sea Lowland, afterwards, until ~ 10,100 At resolution our proxy (0.7‰), preceding not affect off shelf break. constraint outflow through do support al. hypothesis2, unless thermohaline circulation more sensitive small changes than most models suggest23.