Ziemen, Florian Andreas, Kapsch, Marie-Luise, Klockmann, Marlene and Mikolajewicz, Uwe (2019) Heinrich events show two-stage climate response in transient glacial simulations. Open Access Climate of the Past, 15 . pp. 153-168. DOI 10.5194/cp-15-153-2019.

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Heinrich events are among the dominant modes of glacial climate variability. During these events, massive iceberg armadas were released by the Laurentide Ice Sheet, sailed across the Atlantic, and caused large-scale climate changes. We study these events in a fully coupled complex ice sheet–climate model with synchronous coupling between ice sheets and oceans. The ice discharges occur as internal variability of the model with a recurrence period of 5kyr, an event duration of 1–1.5kyr, and a peak discharge rate of about 50mSv, roughly consistent with reconstructions. The climate response shows a two-stage behavior, with freshwater release effects dominating the surge phase and ice-sheet elevation effects dominating in the post-surge phase. As a direct response to the freshwater discharge during the surge phase, the deepwater formation in the North Atlantic decreases and the North Atlantic deepwater cell weakens by 3.5Sv. With the reduced oceanic heat transport, the surface temperatures across the North Atlantic decrease, and the associated reduction in evaporation causes a drying in Europe. The ice discharge lowers the surface elevation in the Hudson Bay area and thus leads to increased precipitation and accelerated ice sheet regrowth in the post-surge phase. Furthermore, the jet stream widens to the north and becomes more zonal. This contributes to a weakening of the subpolar gyre, and a continued cooling over Europe even after the ice discharge. This two-stage behavior can explain previously contradicting model results and understandings of Heinrich Events.

Document Type: Article
Refereed: Yes
Open Access Journal?: Yes
DOI etc.: 10.5194/cp-15-153-2019
ISSN: 1814-9332
Projects: PalMod
Date Deposited: 14 Sep 2018 12:18
Last Modified: 08 Jan 2021 11:08
URI: http://oceanrep.geomar.de/id/eprint/44322

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