Geochemical constraints on the Laurentide Ice Sheet contribution to Meltwater Pulse 1A

Planktonic and benthic dO records adjacent to the runoff outlets of the Laurentide Ice Sheet (LIS) indicate that the LIS contributed to the abrupt w20 m rise in sea level w14.6 ka, Meltwater Pulse 1A (MWP-1A). However, the magnitude of the LIS contribution still remains unresolved. Here, I use a freshwater runoff–ocean mixing model to calculate the LIS meltwater required to explain the decreases in planktonic and benthic d18O observed during MWP-1A at the southern, eastern and northern runoff outlets of the LIS. Maximum LIS contributions in equivalent sea level rise for a 500-year long MWP-1A are 2.7 m discharged into the Gulf of Mexico as a combined hyperpycnal and hypopycnal flow, 2.1 m discharged into the North Atlantic, and 0.5 m into the Arctic Ocean, for a total LIS contribution of 5.3 m. A LIS contribution of <30% to MWP-1A supports the hypothesis that a significant component of this MWP was sourced from the Antarctic Ice Sheet. 2009 Elsevier Ltd. All rights reserved.