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The 8200 yr BP cold event in stable isotope records from the North Atlantic region

Daley, Timothy J.; Thomas, Liz; Holmes, Jonathan A.; Street-Perrott, F. Alayne; Chapman, Mark R.; Tindall, Julia C.; Valdes, Paul J.; Loader, Neil J.; Marshall, James D.; Wolff, Eric; Hopley, Philip J.; Atkinson, Tim; Barber, Keith E.; Fisher, Elizabeth H.; Robertson, Iain; Hughes, Paul.D.M.; Roberts, C. Neil. 2011 The 8200 yr BP cold event in stable isotope records from the North Atlantic region. Global and Planetary Change, 79 (3-4). 288-302. 10.1016/j.gloplacha.2011.03.006

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Abstract/Summary

An abrupt cold event ca. 8200 cal. yr BP, is believed to have been caused by the catastrophic release of ice-dammed meltwater from Lake Agassiz and associated disruption of the Atlantic Meridional Overturning Circulation (AMOC). Previous reviews have highlighted both the “ideal” nature of the 8200 yr event as a target for numerical model validation and the likely geographical restriction of the ensuing cold event to the circum-North Atlantic region but have cited a lack of sufficiently resolved palaeoclimatic records to test this hypothesis. We review the current set of high-resolution stable isotope records from multiple archives (lake, bog, marine and ice cores) in the North Atlantic region for the period 9200–7400 yr BP (present = AD 1950). The isotopic values of terrestrial records are closely linked to isotopic values of palaeoprecipitation. All sites provided evidence for at least one centennial-scale anomaly (beginning ~ 8500–8250 yr BP) that exceeded background variability. No evidence for spatial or temporal transgression of the isotope anomalies was identified, implying that a simultaneous climate signal was observed in the circum-North Atlantic region. Comparison with new simulations using the UK Hadley Centre model HadCM3, which was isotope-enabled to simulate changes in the stable isotope composition of precipitation and forced by freshwater input (“hosing”) of 5 Sverdrups (Sv) (0.005 km3/s), for 1 yr, indicated agreement with the observed decrease in the amplitude of the isotope anomaly with distance from the NW North Atlantic. The model-simulated duration of the event, however, was consistently shorter than that observed in palaeoclimatic records. A review of evidence for forcing additional to the catastrophic release of meltwater from Lake Agassiz (solar variability, sea-ice feedback and longer-term meltwater history) suggested that reduced solar output did not directly coincide with the 8200 yr event, but that a more complex history of meltwater discharges and sea-ice feedback may have conditioned the AMOC for sustained climatic impact.

Item Type: Publication - Article
Digital Object Identifier (DOI): 10.1016/j.gloplacha.2011.03.006
Programmes: BAS Programmes > Polar Science for Planet Earth (2009 - ) > Chemistry and Past Climate
Additional Keywords: Palaeoclimate, Data model comparison
Date made live: 05 Mar 2012 11:51
URI: http://nora.nerc.ac.uk/id/eprint/17073

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