Assessing Global Present-day Surface Mass Transport and Glacial Isostatic Adjustment from Inversion of Geodetic Observations
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Long-term monitoring of global mass transport within the Earth system improves our ability to mitigate natural hazards and better understand their relations to climate change. Satellite gravity is widely used to monitor surface mass variations for its unprecedented spatial and temporal coverage. However, the gravity data contain signals from visco-elastic deformation in response to past ice sheet melting, preventing us from extracting signals of present-day surface mass trend (PDMT) directly. Here we present a global inversion scheme that separates PDMT and visco-elastic glacial isostatic adjustment (GIA) signatures by combining satellite gravimetry with satellite altimetry and ground observations. Our inversion provides global dual data coverage that enables a robust separation of PDMT and GIA spherical harmonic coefficients. It has the advantage to provide estimates of the Earth’s long wavelength deformation signatures and their uncertainties. Our GIA result, along with its uncertainty estimates, can be used in future GRACE processing to better assess the impact of GIA to surface mass change. Our GIA estimates includes rapid GIA uplift in the Southeast Alaska and the Amundsen Sea Embayment, due to the visco-elastic response to recent glacial unloading. We estimate the average surface mass change rate from 2002-2010 to be -203±3 GT·a-1 in Greenland, - 126±18 GT·a-1 in Antarctica and -62±5 GT·a-1 in Alaska. The GIA low degree spherical harmonic coefficients are sensitive to rheological properties in Earth’s deep interior. Our low-degree GIA estimates include geocenter motion and J̇2 which provide unique constraints to understand Earth’s lower mantle and ice history.
