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Processing Choices Affect Ocean Mass Estimates From GRACE
Author(s) -
Uebbing B.,
Kusche J.,
Rietbroek R.,
Landerer F. W.
Publication year - 2019
Publication title -
journal of geophysical research: oceans
Language(s) - English
Resource type - Journals
eISSN - 2169-9291
pISSN - 2169-9275
DOI - 10.1029/2018jc014341
Subject(s) - post glacial rebound , altimeter , geodesy , sea level , satellite , inverse , inversion (geology) , climatology , climate change , environmental science , geology , oceanography , mathematics , physics , geomorphology , geometry , structural basin , astronomy
Accurate estimates of ocean mass change are necessary to infer steric sea level change from sea level changes measured with satellite altimeters. Published studies using the GRACE satellite mission indicated a large range in trends (∼1–2 mm/y) with reported standard errors of 0.1–0.3 mm/y. Here, we show that a large part of this discrepancy (up to 0.6 mm/y) can be explained by which model is used to account for the effect of glacial isostatic adjustment. The second-largest contribution (0.3–0.4 mm/y) is related to the way how different studies have restored atmospheric and oceanic signals which have been removed during the GRACE gravity estimation process. Here, two processing strategies, which previously resulted in differing ocean mass trends are considered. The ’direct’ method uses the standard GRACE Stokes coefficients, while the ’inverse’ method applies a joint inversion of data from GRACE and altimetry. After accounting for differences in processing corrections, global mean ocean mass estimates from the direct, the mascon and inverse approach agree with each other on global scales within less than 0.1 mm/y. Using the A et al. [2013] GIA model, we provide a reconciled monthly time series of global mean ocean mass, which suggests that ocean mass has increased by 1.43 mm/y over 2002.6– 2014.5, with an amplified rate of 1.75 mm/y over 2002.6-2016.5 which covers almost the complete GRACE time span. However, we note that estimates as low as 1.05 mm/y cannot be ruled out when other published GIA corrections with lower mass-equivalent signals over Antarctica are used.