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Meltwater pulse 1A (mwp-1A) was a prominent feature of the last deglaciation, which led to a sea-level rise of ~20 meters in less than 500 years. Concurrent with mwp-1A was the onset of the Bolting-Allerod interstadial event (14,600 years before the present), which marked the termination of the last glacial period. Previous studies have been unable to reconcile a warm Northern Hemisphere with mwp-1A originating from the Laurentide or Fennoscandian ice sheets. With the use of a climate model of intermediate complexity, we demonstrate that with mwp-1A originating from the Antarctic Ice Sheet, consistent with recent sea-level fingerprinting inferences, the strength of North Atlantic Deep Water (NADW) formation increases, thereby warming the North Atlantic region and providing an explanation for the onset of the Boiling-Allerod warm interval. The established mode of active NADW formation is then able to respond to subsequent freshwater forcing from the Laurentide and Fennoscandian ice sheets, setting the stage for the Younger Dryas cold period.
The melting of continental ice sheets during the last deglaciation provided a freshwater source to the ocean that affected global sea level and the strength of the thermohaline circulation. An exceptionally large melting event, inferred from far-field relative sea-level records, occurred ~14,600 years before the present (yr B.P.) wherein global sea level rose by about 20 m in less than 500 years. The ice sheet that served as the source for this event, known as meltwater pulse 1A (mwp-1A), has been the subject of some controversy since mwp-lA was first identified from Barbados coral records (1). The Laurentide Ice Sheet is commonly cited as the most likely source for mwp-1A, but this raises the apparent conundrum of reconciling a large freshwater forcing ~0.5 sverdrup [1 sverdrup (Sv) = 10^sup 6^ m3 s^sup -1^] over several hundred years to the North Atlantic Ocean with an active Atlantic thermohaline circulation and associated warm climate of the Bolling-Allerod warm interval (hereafter B-A) (2). Moreover, a satisfactory mechanism for the onset of the B-A event, conventionally considered as marking the termination of the last glacial period, has not been identified.
Clark et al. (3) provided compelling evidence that the partial collapse of the Antarctic Ice Sheet was responsible for a substantial component of mwp-1A. They noted that the ice-sheet...