Current switching as the cause of rapid warming at the end of the last Glacial Maximum and Younger Dryas

Abstract

The sudden termination of the last Glacial Maximum probably resulted from an intensification of the global thermohaline circulation, but the extraordinary rapidity of warming and increased precipitation over Greenland, O(10) years, has been difficult to explain. Using a simple laboratory model we argue that a salinity-driven positive feedback that accelerates the production and export of North Atlantic Deep Water, which unlike Intermediate Water is not dynamically blocked to the North Atlantic, will lead to a water mass deficit at high latitudes. This loss is rapidly signaled south in the form of topographic and planetary waves, to which the Gulf Stream responds by sending salty water north along a topographically defined path, thereby reinforcing deep water production; the positive feedback that accelerates the process. The Gulf Stream's rapid switch from its glacial zonal to present meridional course led to the abrupt warming observed in the Greenland ice record.