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Abstract

Glacial isostatic adjustment (GIA) is the ongoing response of the solid Earth to the deglaciation of the last Pleistocene ice sheet. In North America near Hudson Bay, the remote region has large-scale GIA-induced deformation, and the GIA modeling is constrained by sparse geodetic measurements from leveling, GNSS, and satellite gravimetry. Satellite-based interferometric synthetic aperture radar (InSAR) has been used to constrain GIA modeling in Iceland. However, measuring surface displacements by InSAR is more challenging in southern Hudson Bay because of the lower-gradient pattern. Such low-gradient displacements in time and space are subject to spatial-correlated biases from tropospheric and ionospheric variations, ocean tide loading, and orbit errors. Here we investigate the feasibility of using InSAR to measure GIA-induced deformation in southern Hudson Bay. We used 5-year (2017-2021) summertime Sentinel-1B SAR data and the persistent scatterer InSAR (PSInSAR) method to estimate surface displacements. We used model-based corrections to alleviate the spatial-correlated errors and further applied the spatiotemporal filter to reduce error residuals. The InSAR-derived vertical velocity shows a consistent pattern with the ICE-6G_D GIA model and shows a good agreement with available GNSS observations (RMS difference is at 2.03 mm/yr). The velocity map reveals distinct regional differences with model prediction, at 2-3 mm/yr higher in the northern and southern areas, and 2-3 mm/yr lower in the middle of the Hudson Bay land area study region. The revealed regional inconsistency between the InSAR-derived deformations and the GIA model could advance the understanding of GIA and potentially constrain the Earth's rheology in this region.