| Summary: | Freshwater fluxes into the North Atlantic are known to have caused catastrophic shifts in climate by weakening the formation of North Atlantic Deep Water (NADW). During the end of the last glacial period, several large freshening events were recorded in the geologic record within the Champlain Sea, indicating that large volumes of freshwater from pro-glacial lakes, such as Lake Agassiz and others in the Great Lakes Region, likely routed out into the North Atlantic. This study utilizes a two-dimensional estuarine model of the Champlain Sea during two flood events at 11.4 and 13.0 ka BP to estimate the durations and magnitudes of these freshwater flooding events, the later being of particular note as it closely predates the Younger Dryas cooling episode. Values of pre and post-flood paleo-salinity within the current-day Lake Champlain are used as constraints within the model to determine the amount and duration of freshwater fluxes required to cause the observed salinity changes. Paleo-salinity during the 11.4 ka BP event changed from 25 ppt to 8 ± 3 ppt, which requires flood volumes in excess of 5,500 km3 to inundate the region over timescales of less than two weeks. The model could not reproduce the observed freshening of the Champlain Sea (25 to 0 ± 3 ppt) for reasonable flood volumes, which may reflect model limitations in strongly sloping bathymetry and narrow channels, as well as uncertainties in the bathymetric reconstruction. These constraints on the fluxes of freshwater into the North Atlantic are useful in understanding what may have caused partial or total shutdowns of NADW during the end of the last ice age.
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