Research brief: How deep ocean circulation causes Dansgaard–Oeschger variability

The last glacial period was interrupted by millennial-scale events during which the North Atlantic climate transitioned rapidly between cold (stadial) and warm (interstadial) conditions. This variability, which is referred to as Dansgaard–Oeschger variability, is widely believed to arise from perturbations of the Atlantic Meridional Overturning Circulation.

Evidence for such changes during the longer Heinrich stadials has been identified, but direct evidence for overturning circulation changes during Dansgaard–Oeschger events has proven elusive.

Here we reconstruct changes in bottom water acidity between 62,000 and 10,000 years before present. We find that warm conditions in the North Atlantic are accompanied by a rapid incursion of North Atlantic Deep Water into the deep South Atlantic.

Based on these results and transient climate model simulations, we conclude that the last glacial climate variability was associated with significant changes in the North Atlantic Deep Water formation, that were rapidly transmitted across the Atlantic.

 

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