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Self-Consistent Ice Mass Balance and Regional Sea Level from Time-Variable Gravity

by T. C. Sutterley, I. Velicogna and C.-W. Hsu
Earth and Space Science (2020)

Abstract:
Measurements of time-variable gravity from the Gravity Recovery and Climate Experiment (GRACE) and the GRACE Follow-on (GRACE-FO) missions are an invaluable tool for monitoring changes in mass of the Earth's glaciated regions. We improve upon estimates of glacier and ice sheet mass balance from time-variable gravity by including instantaneous spatiotemporal variations in sea level. Here, a least-squares mascon technique is combined with solutions to the sea level equation to iteratively correct the GRACE/GRACE-FO data for the induced sea level response on a monthly basis. We find that variations in regional sea level affect ice sheet mass balance estimates in Greenland by approximately 4% and in Antarctic by approximately 5%. Since 2002, the Greenland ice sheet has been losing mass at an average rate of 263±23 Gt/yr, and the Antarctic ice sheet has been losing mass at average rates between -90±52 Gt/yr and -122±53 Gt/yr depending on the rate of Glacial Isostatic Adjustment (GIA). The mass losses from both ice sheets represent an increase of 15.6±2.0 mm to global mean sea levels since 2002.

Caption: Spatial pattern of sea level change, dS/dt, in millimeters per year induced fromchanges in glaciers and ice sheets around a) Antarctica and b) Greenlandic Arctic. GIA correction is from Simpson et al. (2009) for the Arctic and Ivins et al. (2013) for the Antarctic. The contour interval is 1 mm/yr, the red contour delineates 0 mm/yr and the blue contour delineatesthe global average (barystatic) rate of each map. Delineations of Antarctic grounded ice are from Mouginot et al. (2017). Delineations of Greenland coastlines are from Henriksen et al. (2009).
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