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Abstract:
Much of the Atlantic coast of North America has been sinking for thousands of years, at a maximum rate of ~20 cm per century, due to solid Earth deformation in response to deglaciation of the Laurentide ice sheet – a process known as glacial isostatic adjustment (GIA). In addition to GIA, other factors, including recent human intervention in water sources (such as excessive groundwater usage and damming) might be significant contributors to vertical land motion (VLM) in the region. The primary aim of this research is to isolate and better understand the contribution of recent hydrological loading to the VLM signal in southeastern Canada and northeastern USA. To this end, we use results from an extensive GIA modelling analysis based on a large ensemble of 14960 Earth-ice model input parameters and two regional paleo RSL data compilations, as well as millennial-scale VLM rates derived from RSL reconstructions, to identify areas where the contemporary VLM rates cannot be explained by long-term processes such as GIA. Preliminary results indicate the presence of significant contemporary signals in Maine (Karegar et al., 2017) and southeastern Hudson Bay (the latter is most likely associated with the James Bay Hydroelectric Project in Quebec). To complement our GIA and GNSS analyses, we will use GRACE observations as well as output from hydrological models to determine whether the residuals are compatible with a recent water loading signal.
