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Abstract:
In recent years, monitoring of changes in the Earth’s gravity field has been carried out mainly by the Gravity Recovery And Climate Experiment (GRACE) and its successor GRACE Follow-On. However, very little information is available on the temporal evolution of the Earth's gravity field prior to the launch of the GRACE mission and through gaps in GRACE K-band data between 2010 and 2019. Fortunately, GRACE and GRACE Follow-On are not the only missions for the Earth's gravity field recovery. For the mass redistribution characteristics in large scales, we may employ Satellite Laser Ranging (SLR) observations to geodetic satellites.
In this study, we derive gravity field changes for Greenland and Antarctica based on SLR data and compare the results to the GRACE, GRACE Follow-On, and Ice sheet Mass Balance Inter-comparison Exercise (IMBIE) data. We propose a set of long-term, continuous solutions, in which the gravity field is expanded up to degree and order 10/10 with a monthly resolution from 1/1995 to 10/2021. We show results from the unconstrained solution, as well as the solution that has been decomposed into normal equations expanded up to degree and order 4, 6, 8, and 10 and stacked, taking advantage of stability and better resolution from lowest and higher-degree expansion. We also propose different types of weighting, degree and order-specific constraining, and different data lengths. The SLR-based solutions are evaluated based on the noise on the oceans and differences to IMBIE and GRACE results for Greenland and Antarctica, which are identified by substantial ice mass loss.
