GRACE‐D accelerometer data show significant bias jumps since one month after the launch of the GRACE Follow‐On (GRACE‐FO) satellites in May 2018, making them inapplicable for correcting GRACE‐FO products for non‐gravitational accelerations. The GRACE‐FO Science Data System (SDS) compensated this issue by transplanting the GRACE‐C accelerometer data toward that of GRACE‐D. Recently, GRACE‐FO SDS implemented an updated transplant method, used in the latest release of GRACE‐FO data. Here, we examine the impact of updated accelerometer transplant data (ACH) on GRACE‐FO measurements at all levels: (a) Level‐1B inter‐satellite laser ranging residuals measured along satellite orbit, (b) Level‐2 time‐variable gravity solutions from all SDS centers (JPL, CSR, and GFZ), and (c) Level‐3 mascon solutions. We show that inter‐satellite laser ranging residuals are modified at low frequencies below 1 mHz, affecting the along‐orbit analysis of large‐scale time‐variable gravity signals. When mapped into monthly Level‐2 spherical harmonic coefficients of geopotential, the low‐frequency change in inter‐satellite ranging residuals leads to substantial improvement of coefficients associated with resonant orders (i.e., 15, 30, 45, etc.) and C30. We also present an improved SLR‐derived C30 which significantly improves the agreement with updated GRACE‐FO C30 at seasonal and interannual timescales. Moreover, we demonstrate the noise reduction in mass change estimates from new GRACE‐FO Level‐2 data over oceans, Greenland, and Antarctica for all SDS solutions. GRACE‐FO mascon solutions show a moderate change in the updated release. Our comprehensive analyses demonstrate high‐quality estimates of non‐gravitational accelerations by the updated transplant method, resulting in more accurate GRACE‐FO time‐variable gravity and mass change observations.

<p>The German Research Centre for Geosciences (GFZ), together with the Technische Universität Dresden and the Alfred-Wegener-Institute (AWI), maintains the ‘Gravity Information Service’ portal (GravIS, gravis.gfz-potsdam.de). GravIS facilitates the dissemination of user-friendly data of mass variations in the Earth system, based on observations of the GFZ and NASA/JPL satellite gravimetry mission GRACE (Gravity Recovery and Climate Experiment, 2002-2017) and its successor mission GRACE-FO (GRACE-Follow-On, since 2018).</p><p>The portal provides mass changes of the Greenland and Antarctic ice sheets on a regular 50 km by 50 km Polar stereographic grid and as basin averages accompanied by empirical uncertainties. Both ice mass balance products rely on the same input data of GRACE/GRACE-FO spherical harmonic coefficients, generated and post-processed by GFZ. Corrections applied to the data include the insertion of estimates of the geocentre motion, replacement of the C20 and C30 coefficients, and the correction for glacial isostatic adjustment with the ICE-6G model.</p><p>The gridded data product is processed with sensitivity kernels, tailored explicitly to resolving mass changes of the ice sheets. A regional integration applies these sensitivity kernels to the unfiltered GRACE and GRACE-FO spherical harmonic coefficients. The sensitivity kernels optimise a trade-off between leakage errors and propagated GRACE solution errors.</p><p>The basin-average product consists of continent-wide estimates of ice sheet mass changes, and basin averages for seven basins in Greenland and 25 basins in Antarctica. The regional time series are calculated using a forward-modelling  inversion approach, which considers the typical spatial anomalies of the surface-mass balance and dynamic ice discharge.</p><p>In addition to the ice mass change data, GravIS provides terrestrial water storage (TWS) variations over the continents and ocean bottom pressure (OBP) variations from which global mean barystatic sea-level rise can be estimated. These data sets are provided either on 1° grids or as regional averages.</p><p>The data sets of all Earth system domains can be interactively displayed with the portal and are freely available for download. This contribution aims to show the features and possibilities of the GravIS portal to cryosphere researchers.</p>

Mass change inferences from GRACE and GRACE-FO typically involve, first, the preparation of spherical harmonic (SH) datasets on global gravity field changes and, second, their subsequent analysis that leads to mass change estimates. This study addresses the second step, which builds on SH input datasets that comprise the monthly gravity field solutions as well as amendments to low-degree components and subtraction or re-addition of certain modeled geophysical signals. A variety of methods have been developed to estimate mass changes from SH input datasets. It remains a challenge to assess and compare different methods adopted by different studies and to understand the mechanisms by which their results differ. Methods are often distinguished as belonging to either the inverse or direct approach. In the inverse approach, mass changes are estimated using a set of predefined spatial patterns. In the direct approach, surface mass density variations are integrated by using a predefined weight function, or sensitivity kernel. In this paper, we recall that sensitivity kernels are inherent not only to the direct approach. They are also inherent and may be made explicit, for inverse approaches. We prove that certain implementations of the direct and inverse approach have identical sensitivity kernels, and are therefore equivalent, under the condition that they rigorously incorporate the same signal and error covariance information. We present sensitivity kernels for the example of four different methods to estimate Greenland Ice Sheet mass changes. We discuss the sensitivity kernels in relation to the underlying differences in the methods. We propose to use sensitivity kernels as a means of communicating, assessing and comparing methods of mass change estimates. Once the sensitivity kernels associated to a method are made explicit, any user can readily investigate the method in terms of leakage effects, error propagation from the input SH datasets, or effects of the choice of the SH input datasets.

<p>The GRACE-D accelerometer data shows large bias jumps starting from 21 June 2018. The GRACE Follow-On (GRACE-FO) Science Data System (SDS) centers (CSR, JPL and GFZ) use a transplant technique applying GRACE-C accelerometer data to replace that of GRACE-D. To improve the accuracy of non-gravitational measurements acting on the satellites, the GRACE-FO SDS centers recently released an updated hybrid-transplant accelerometer data for GRACE-D, which uses measurements from both satellites. Accordingly, updated (RL06.1) Level-2 (L2) monthly gravity solutions using the new accelerometer data are being released. In this work, we will present our results on quantification of the changes/improvements in the RL06.1 L2 solutions from all three SDS centers relative to RL06. We also explore the possibility of validating the changes using independent datasets. We first compare the low-degree harmonic coefficients C_{20} and C_{30} with those from SLR (TN-14) and examine their agreement at seasonal and interannual timescales. Using various spectral-domain analysis tools, we detect the spectral bands of spherical harmonic degrees and orders where the major changes in RL06.1 are observed. We then quantify the impact of such spherical harmonic coefficients on surface mass change estimates over the GRACE-FO period. Moreover, we quantify the noise reduction in monthly mass change solutions from RL06.1 (relative to RL06) over open oceans. For the latter analysis, we also detect the spatial regions as well as months which show the largest noise reduction and discuss the possible causes behind that. Our work is aimed at helping the GRACE-FO SDS to evaluate the improvement by new accelerometer transplant data.</p>