A series of simulations have been performed using the Hadley Centre GCM, (HadCM3) to investigate the 8.2ka event. A control simulation with 9ka boundary conditions showed that intrinsic variability in the strength of the N. Atlantic Meridional Overturning Circulation (MOC) was greater than in a comparable pre-industrial simulation but these natural variations were not strong enough to replicate the 8.2ka event at any time, consistent with the idea that the event was 'forced' through a freshwater discharge. We therefore investigated the response of the 9ka climate to a freshwater forcing consistent with the final drainage of Lake Agassiz. A 10 member ensemble was performed with 5Sv of freshwater added to the N. Atlantic ocean for 1year at various times of the control run, which led to a reduction in the strength of the MOC and the temperature, precipitation and δ18O of precipitation over the N. Atlantic region. The strength and location of the response agreed well with proxy evidence of the 8.2ka event but the duration was too short in all cases. The response to the freshwater forcing was sensitive to the initial state of the ocean, with better agreement with paleodata when the freshwater was added at a time when the Atlantic MOC was relatively weak. The structure and duration of the δ18Op response was consistent over a large region, and appeared in better agreement with regional precipitation than regional temperature, however there were spatial differences between the maximum δ18Op response and both the maximum temperature and precipitation responses.
- 8.2ka event
- Early Holocene