ABSTRACT: The Lake Agassiz megaflood and 8200 BP cold event: was there a causal link?

CGRG Bibliography of Canadian Geomorphology
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Abstract

The most conspicuous climate event of the past 10,000 years occurred while North American was exiting from the last Ice Age and is commonly known as the “8.2 kyr BP cold event”. The timing of this event appears to coincide with a geologically remarkable flood – the final draining of ice-dammed glacial Lake Agassiz. The volume of released water has been estimated as ~151,000 km3, more than ten times that of Lake Superior, the largest contemporary freshwater lake. Model-based estimates place the peak discharge at ~5 Sv and the duration at ~0.5 yr. The cause of the 8.2 kyr event remains controversial. Earlier abrupt climate change events seem to have been associated with ocean circulation changes in response to freshening of the North Atlantic, either by redirection of deglacial meltwater or by melting of iceberg armadas launched from the Laurentide Ice Sheet. The switching mechanism for which there is the strongest evidence is that associated with changing the operation of the North Atlantic meridional overturning circulation (MOC). The Agassiz megaflood presents a near-ideal case for testing this idea because the volume of released freshwater and rate of delivery are well constrained. Several recent modeling studies, aimed at simulating the 8.2 kyr event, support the idea that the flood triggered a change in the MOC but there is scant evidence in the marine sedimentary record to support this claim. In this paper we combine hydraulic modelling of the flood forcing, with coupled ocean–atmosphere modelling of the climate response to reconcile model predictions with the paleoenvironmental evidence.

Bibliography of Canadian Geomorphology