Abstract:

We compare geoid rates over North America from GRACE data to predictions based on glacial isostatic adjustment (GIA). The return flow of mantle material to regions previously covered by the large ice sheets of the last glacial cycle produces one of the largest non-hydrological secular signals present in the GRACE data. Predictions of the geoid rate due to GIA have a characteristic increase centered near Hudson Bay. The observed geoid "rate" has a similar pattern with amplitudes (depending on the GRACE dataset and analysis approach) that are within the range of model predictions. In addition, a broad, lower-amplitude signal south of the previously-glaciated regions is also observed, presumably due to hydrology. We will present preliminary findings regarding the analysis of GRACE data in this region, and describe the ability of current time series to discriminate between ice and Earth models.