A role for icebergs in the 8.2 ka climate event

Type Article
Date 2010-08
Language English
Author(s) Wiersma Ane P.1, 2, Jongma Jochem I.2
Affiliation(s) 1 : Deltares, Dept Morphol & Sedimentary Syst, NL-3584 CB Utrecht, Netherlands.
2 : Vrije Univ Amsterdam, Fac Earth & Life Sci, NL-1081 HV Amsterdam, Netherlands.
Source Climate Dynamics (0930-7575) (Springer), 2010-08 , Vol. 35 , N. 2-3 , P. 535-549
DOI 10.1007/s00382-009-0645-1
WOS© Times Cited 30
Keyword(s) 8.2 ka event, Climate modeling, Icebergs, Laurentide ice sheet, Hudson Strait, Holocene, Heinrich events
Abstract

We investigate the potential role of icebergs in the 8.2 ka climate event, using a coupled climate model equipped with an iceberg component. First, we evaluate the effect of a large iceberg discharge originating from the decaying Laurentide ice sheet on ocean circulation, compared to a release of an identical volume of freshwater alone. Our results show that, on top of the freshwater effect, a large iceberg discharge facilitates sea-ice growth as a result of lower sea-surface temperatures induced by latent heat of melting. This causes an 8% increased sea-ice cover, 5% stronger reduction in North Atlantic Deep Water production and 1A degrees C lower temperature in Greenland. Second, we use the model to investigate the effect of a hypothetical two-stage lake drainage, which is suggested by several investigators to have triggered the 8.2 ka climate event. To account for the final collapse of the ice-dam holding the Laurentide Lakes we accompany the secondary freshwater pulse in one scenario with a fast 5-year iceberg discharge and in a second scenario with a slow 100-year iceberg discharge. Our experiments show that a two-stage lake drainage accompanied by the collapsing ice-dam could explain the anomalies observed around the 8.2 ka climate event in various climate records. In addition, they advocate a potential role for icebergs in the 8.2 ka climate event and illustrate the importance of latent heat of melting in the simulation of climate events that involve icebergs. Our two-stage lake drainage experiments provide a framework in the discussion of two-stage lake drainage and ice sheet collapse.

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