Description: The impact of elastic vertical land movement (VLM) on relative sea levels along the world's coastlines is significant. In Northern Europe, VLM is mainly due to the effect of Glacial Isostatic Adjustment (GIA). However, the rapid melting of ice in the Arctic is causing a substantial elastic uplift with both a local, but also a long-range footprint of 1000-3000 km from the point of ice loss. When VLM estimates from GNSS are unavailable, sea-level studies based on tide gauges often rely on a GIA-only VLM model to correct any ongoing uplift, but in Arctic regions, this can lead to underestimation of the uplift or overestimation of the absolute sea-level change due to significant changes in present-day ice loading (PDIL). Here, a high-resolution time-varying elastic VLM model (5x5 km) is developed from high-resolution estimates of glacial and Greenland Ice Sheet mass balance is presented. The elastic VLM model is combined with a GIA model to create a complete VLM model that is comparable with GNSS-measured VLM rates (in a center of mass frame). Additionally, far-field elastic effects from the Antarctic and Terrestrial Water Storage are included to create a complete vertical deformation map for the Northern Hemisphere, that can complement sea level studies in areas with few or no GNSS measurements.

Description: The newest DTU global high-resolution global marine free air gravity field called DTU21 is presented in this presentation and the first evaluation against marine and airborne gravity is performed. A total of 14 years from geodetic missions including (7 years of Cryosat-2 (369 days repeat mission) as well as 3 years of Jason-1+2 end-of-life missions and 4 years of SARA/AltiKa drifting geodetic mission). Older geodetic missions (ERS-1 and GEOSAT) are now nearly retired. All Geodetic missions have been fully retracked using the 2-pass retracker developed by Sandwell and Smith, (2005) to increase the range precision. Subsequently, we derive 2-Hz altimetric observations from the 20/40 Hz retracked data using the Parks McClellan filter to avoid spectral leakage degrading the 10-40 km wavelength which is an effect of the box filter normally used to compute 1 Hz data. In the Arctic Ocean, we will present results from several new developments in high-resolution gravity field modelling. One is a new dual-pass retracking of SARAL/AltiKa together with a new physical retracking system for Cryosat-2 derived at ESA called SAMOSA+. This was retracked using the ESA GPOD service. A new medium wavelength correction based on altimetry and GOCE has been introduced to deal with problems in the older remove restore technology based on EGM2008. This is particularly important for Cryosat-2 due to its ability of provide new accurate sea surface height information for gravity field determination all the way up to 88N where no altimeters have measured before.

Description: The ocean mass budget plays a crucial role in predicting future changes in ocean mass and sea level. In recent efforts to reconcile observations from GRACE and GRACE-Follow On satellites with steric-corrected altimetry and models of contributions from land and ice a discrepancy in the mass budget has been reported (Wang et al, 2022; Barnoud et al, 2022), in particular in the period following the launch of GRACE-Follow On. In this study, we aim to compare 20 years of GRACE-observed mass changes with steric-corrected altimetry and GRD-induced sea level changes resulting from landmass changes. To accomplish this, we produce monthly 3D global mass change products with a spatial resolution of 0.5 degrees, covering the period from 2003 to 2022. We improve the processing steps for steric-corrected satellite altimetry by accounting for ocean bottom deformation, removing the global mean contribution of halosteric sea level change, and replacing the radiometer-based wet tropospheric correction with a model-based correction. Our results indicate that both the steric-corrected altimetry and ocean mass reconstruction from GRD-induced sea level change is in agreement with the GRACE observations on both long-term and seasonal time scales and regional scales. We also find that a recent slowdown in GRACE-observed mass change during the GRACE-FO period can be attributed to terrestrial water storage variability driven by a long phase of La Nina and a deceleration in the mass loss of Greenland and Antarctic ice sheets.