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

• Published in: Global and Planetary Change
• Main Authors: Daley, T.J., Thomas, E.R., Holmes, J.A., Street-Perrott, F.A., Chapman, M.R., Tindall, J.C., Valdes, P.J., Loader, N.J., Marshall, J.D., Wolff, E.W., Hopley, Philip J., Atkinson, T., Barber, K.E., Fisher, E.H., Robertson, I., Hughes, P.D.M., Roberts, C.N.
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Elsevier 2011
• Subjects: Earth and Planetary Sciences; North Atlantic; Sea ice
• Online Access: https://eprints.bbk.ac.uk/id/eprint/4009/; https://doi.org/10.1016/j.gloplacha.2011.03.006

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.