Abstract
AbstractMascon products derived from Gravity Recovery and Climate Experiment satellite gravimetry data are widely used to study the Greenland ice sheet mass balance. However, the products released by different research groups—JPL, CSR, and GSFC—show noticeable discrepancies. To understand them, we compare those mascon products with mascon solutions computed in‐house using a varying regularization parameter. We show that the observed discrepancies are likely dominated by differences in the applied regularization. Furthermore, we present a numerical study aimed at an in‐depth analysis of regularization‐driven biases in the solutions. We demonstrate the ability of our simulations to reproduce 60%–80% of biases observed in real data, which proves that our simulations are sufficiently realistic. After that, we demonstrate that the quality of mascon‐based estimates can be increased by a proper modification of the applied regularization: no correlation between mascons is assumed when they belong to different drainage systems. Using both simulations and real data analysis, we show that the improved regularization mitigates signal leakage between drainage systems by 11%–56%. Finally, we validate various mascon solutions over the SW drainage system, using trends from (i) the GOCO‐06S model and (ii) the Input‐Output Method as control data. In general, the in‐house computed trend estimates are consistent with the trends from CSR and JPL solutions and the trends from the control data.
Highlights
The Gravity Recovery and Climate Experiment (GRACE) satellite mission, which was launched in 2002, allowed mass anomalies at the global and regional scale to be estimated until June 2017 (Tapley et al, 2004, 2019)
The GRACE-based mascon solutions offered by the Jet Propulsion Laboratory (JPL RL06 v01) (Watkins et al, 2015), the Goddard Space Flight Center (GSFC v2.4) (Luthcke et al, 2013; Rowlands et al, 2005), and the Center for Space Research (CSR RL06 v01) of The University of Texas at Austin (Save et al, 2016) are widely used
The mascon approach exploited by GSFC, CSR, and JPL, which deals with the GRACE Level-1B data, ensures a global mass conservation during the estimation of a global set of mascons with the relevant constraint equation that the sum of all mascons is equal to zero
Summary
The Gravity Recovery and Climate Experiment (GRACE) satellite mission, which was launched in 2002, allowed mass anomalies at the global and regional scale to be estimated until June 2017 (Tapley et al, 2004, 2019). The GRACE-based mascon solutions offered by the Jet Propulsion Laboratory (JPL RL06 v01) (Watkins et al, 2015), the Goddard Space Flight Center (GSFC v2.4) (Luthcke et al, 2013; Rowlands et al, 2005), and the Center for Space Research (CSR RL06 v01) of The University of Texas at Austin (Save et al, 2016) are widely used. GSFC used an exponential function describing correlations in time and space between mascon pairs (Luthcke et al, 2013), JPL used temporal and spatial constraints, which were extracted from geophysical and hydrological models (Watkins et al, 2015), and CSR used a temporally and spatially variable zero-order Tikhonov regularization, which implies no correlations in the spatial and time-domain (Save et al, 2016). From a mathematical point of view, all constraints can be considered as special variants of Tikhonov regularization (Tikhonov, 1963a, 1963b)
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