| Summary: | [1] The last deglaciation, between 21 thousand years BP (kyr BP) and 8 kyr BP, was punctuated by a series of climatic oscillations, both in the Northern and Southern Hemispheres, often attributed to changes in ocean circulation. These oscillations are explored with an Earth system model of intermediate complexity, including a synchronous coupling between atmosphere, ocean, and ice sheet dynamics. We focused more particularly on the impact of Heinrich Event 1 (HE1) on the deglaciation process. Representation for HE1 was achieved by a parameterization of iceberg discharge included in the ice sheet model, based on paleoceanographic evidence. The model simulates the following sequence in response to the HE1: (1) The thermohaline circulation is drastically reduced as soon as HE1 starts, causing a sharp cooling in the North Atlantic and a smooth warming in the Southern Hemisphere. (2) Circulation restarts abruptly at the end of HE1, producing an intense warming in both hemispheres (up to 10°C warming in the Greenland-North Atlantic area, with a rapidly decreasing amplitude as one moves southward). (3) Along with this warming, the melting of the North American and Eurasian ice sheets is enhanced, producing a small freshwater discharge to the North Atlantic, but there is no significant impact on Atlantic salinity and thermohaline circulation. (4) A few decades after the post-Heinrich warm event, both the southern Atlantic and Antarctica entered a prolonged cold period caused by the reactivation of the thermohaline circulation. (5) Finally, about 1500 years later, depending on sensitivity experiments, meltwater flowing into the North Atlantic through the Hudson Strait and the Barents Sea causes a gradual vertical stratification of the northern North Atlantic. The presented simulations are compared to paleoarchives by taking into account the limits inherent to the model structure. One of the conclusions is that there is probably no direct link between the meltwater pulse 1A observed in sea level data and the onset of the Younger Dryas.
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