Model-data comparison for the 8.2 ka BP event: confirmation of a forcing mechanism by catastrophic drainage of Laurentide Lakes

To improve our understanding of the mechanism behind the 8.2 ka BP cooling event, we compare proxy evidence with climate model simulations in which the thermohaline ocean circulation is perturbed by a freshwater pulse into the Labrador Sea. Both the proxy-data and model results show a cooling that is mainly concentrated in the North Atlantic region. ranging from more than 5 degrees C cooling in the Nordic Seas to about 0.5-1 degrees C over Europe and less than 0.5 degrees C over the subtropical North Atlantic. Data and model also indicate a weakening of the summer monsoon and generally a drier circum-North Atlantic. Over the South Atlantic Ocean, the model simulates a slight warming (mostly less than 0.5 degrees C), which falls within the uncertainty of proxy data and thus could not be confirmed. To examine in detail the structure of the 8.2 ka BP event, we also compare the modeled climatological evolution at two locations with high-quality records, revealing a generally consistent picture. The good model-data agreement confirms the hypothesis that the 8.2 ka BP event was forced by a freshwater-induced weakening of the thermohaline circulation. Other forcings are unlikely, since they would result in an alternative geographical distribution and expression of the climate response. (c) 2005 Elsevier Ltd. All rights reserved.