Heinrich events show two-stage climate response in transient glacial simulations

Heinrich events show two-stage climate response in transient glacial simulations

Heinrich events are among the dominant modes of glacial climate variability. During these events, massive iceberg armadas were released by the Laurentide Ice Sheet and sailed across the Atlantic where they melted and released freshwater, as well as detritus, that formed characteristic layers on the...

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Bibliographic Details
Published in:Climate of the past Vol. 15; no. 1; pp. 153 - 168
Main Authors: Ziemen, Florian Andreas, Kapsch, Marie-Luise, Klockmann, Marlene, Mikolajewicz, Uwe
Format: Journal Article
Language:English
Published: Katlenburg-Lindau Copernicus GmbH 24-01-2019
Copernicus Publications
Subjects:
Analysis
Climate
Climate change
Climate models
Climate variability
Cold climates
Cold weather
Computer simulation
Deep water
Detritus
Discharge
Drying
Duration
Elevation
Evaporation
Flood peak
Freshwater
Glacial climates
Glacial erosion
Glaciation
Global climate
Heat transport
Heinrich events
Ice
Ice sheets
Icebergs
Inland water environment
Jet stream
Jet streams (meteorology)
Laurentide ice sheet
Ocean currents
Ocean floor
Oceans
Paleoclimatology
Precipitation
Rainfall
Regrowth
Surface temperature
Variability
Atlantic Ocean
Europe
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Summary:Heinrich events are among the dominant modes of glacial climate variability. During these events, massive iceberg armadas were released by the Laurentide Ice Sheet and sailed across the Atlantic where they melted and released freshwater, as well as detritus, that formed characteristic layers on the seafloor. Heinrich events are known for cold climates in the North Atlantic region and global 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 an internal variability of the model with a recurrence period of 5 kyr, an event duration of 1–1.5 kyr, and a peak discharge rate of about 50 mSv, 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 the post-surge phase. As a direct response to the freshwater discharge during the surge phase, deepwater formation in the North Atlantic decreases and the North Atlantic deepwater cell weakens by 3.5 Sv. 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, which 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.
ISSN:1814-9332
1814-9324
1814-9332
DOI:10.5194/cp-15-153-2019