Simulation of the cold climate event 8200 years ago by meltwater outburst from Lake Agassiz



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Bauer, E. and Ganopolski, A. and Montoya Redondo, María Luisa (2004) Simulation of the cold climate event 8200 years ago by meltwater outburst from Lake Agassiz. Paleoceanography, 19 (3). ISSN 0883-8305

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The cold climate anomaly about 8200 years ago is investigated with CLIMBER-2, a coupled atmosphere-ocean-biosphere model of intermediate complexity. This climate model simulates a cooling of about 3.6 K over the North Atlantic induced by a meltwater pulse from Lake Agassiz routed through the Hudson strait. The meltwater pulse is assumed to have a volume of 1.6 x 10^14 m^3 and a period of discharge of 2 years on the basis of glaciological modeling of the decay of the Laurentide Ice Sheet ( LIS). We present a possible mechanism which can explain the centennial duration of the 8.2 ka cold event. The mechanism is related to the existence of an additional equilibrium climate state with reduced North Atlantic Deep Water (NADW) formation and a southward shift of the NADW formation area. Hints at the additional climate state were obtained from the largely varying duration of the pulse-induced cold episode in response to overlaid random freshwater fluctuations in Monte Carlo simulations. The model equilibrium state was attained by releasing a weak multicentury freshwater flux through the St. Lawrence pathway completed by the meltwater pulse. The existence of such a climate mode appears essential for reproducing climate anomalies in close agreement with paleoclimatic reconstructions of the 8.2 ka event. The results furthermore suggest that the temporal evolution of the cold event was partly a matter of chance.

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© 2004 by the American Geophysical Union.
This work was supported by the Research Grant 01 LG 9906 of BMBF. The work benefited from discussions with Reinhard Calov, Stefan Rahmstorf, and Sushma Prasad. The time series from GRIP and NorthGRIP were kindly provided by Sigfus Johnsen. The authors thank Hans Renssen and the anonymous Referee for their valuable comments on the manuscript.

Uncontrolled Keywords:Laurentide ice-sheet; North-Atlantic climate; Last glacial cycle; Fresh-water input; Holocene climate; Thermohaline circulation; Intermediate complexity; Hydrological changes; Oxygen-isotope; Younger dryas
Subjects:Sciences > Physics > Astrophysics
Sciences > Physics > Astronomy
ID Code:37957
Deposited On:01 Jun 2016 14:57
Last Modified:10 Dec 2018 15:05

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