Glacial isostatic adjustment under a changing groundwater load since the Last Glacial Maximum

During the last deglaciation, the retreating Laurentide Ice Sheet made way for massive proglacial lakes to form and then drain. In a similar fashion, dramatic changes in climate over the deglaciation were reflected in changing groundwater storage through time. We evaluate the impacts of these long-term changes in water storage on Glacial Isostatic Adjustment (GIA) in North America. To do so, we couple the Water Table Model (WTM) – which simulates depth to water table – with a gravitationally self-consistent GIA model to find both changing lake and groundwater storage volumes, and the impacts that these have on changing GIA. 

Our WTM results show an evolving water table that includes proglacial and pluvial lakes consistent with the geological record. Lake and groundwater loading deflect topography by tens of metres at some locations. Because depth to water table is topography-dependent, we repeat our WTM simulation using updated topographic inputs and find that water table depth is modified by several metres at some locations. The results are highly heterogeneous, reflecting that GIA and hydroclimate together drive long-term water-table change.