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Studies of the global sea-level budget (SLB) and the global ocean-mass budget (OMB) are essential to assess the reliability of our knowledge of sea-level change and its contributors. Here we present datasets for times series of the SLB and OMB elements developed in the framework of ESA's Climate Change Initiative. We use these datasets to assess the SLB and the OMB simultaneously, utilising a consistent framework of uncertainty characterisation. The time series, given at monthly sampling and available at 10.5285/17c2ce31784048de93996275ee976fff (Horwath et al., 2021), include global mean sea-level (GMSL) anomalies from satellite altimetry, the global mean steric component from Argo drifter data with incorporation of sea surface temperature data, the ocean-mass component from Gravity Recovery and Climate Experiment (GRACE) satellite gravimetry, the contribution from global glacier mass changes assessed by a global glacier model, the contribution from Greenland Ice Sheet and Antarctic Ice Sheet mass changes assessed by satellite radar altimetry and by GRACE, and the contribution from land water storage anomalies assessed by the global hydrological model WaterGAP (Water Global Assessment and Prognosis). Over the period January 1993–December 2016 (P1, covered by the satellite altimetry records), the mean rate (linear trend) of GMSL is 3.05 ± 0.24 mm yr -1. The steric component is 1.15 ± 0.12 mm yr -1 (38 % of the GMSL trend), and the mass component is 1.75 ± 0.12 mm yr -1 (57 %). The mass component includes 0.64 ± 0.03 mm yr -1 (21 % of the GMSL trend) from glaciers outside Greenland and Antarctica, 0.60 ± 0.04 mm yr -1 (20 %) from Greenland, 0.19 ± 0.04 mm yr -1 (6 %) from Antarctica, and 0.32 ± 0.10 mm yr -1 (10 %) from changes of land water storage. In the period January 2003–August 2016 (P2, covered by GRACE and the Argo drifter system), GMSL rise is higher than in P1 at 3.64 ± 0.26 mm yr -1. This is due to an increase of the mass contributions, now about 2.40 ± 0.13 mm yr -1 (66 % of the GMSL trend), with the largest increase contributed from Greenland, while the steric contribution remained similar at 1.19 ± 0.17 mm yr -1 (now 33 %). The SLB of linear trends is closed for P1 and P2; that is, the GMSL trend agrees with the sum of the steric and mass components within their combined uncertainties. The OMB, which can be evaluated only for P2, shows that our preferred GRACE-based estimate of the ocean-mass trend agrees with the sum of mass contributions within 1.5 times or 0.8 times the combined 1 σ uncertainties, depending on the way of assessing the mass contributions. Combined uncertainties (1 σ) of the elements involved in the budgets are between 0.29 and 0.42 mm yr -1 , on the order of 10 % of GMSL rise. Interannual variations that overlie the long-term trends are coherently represented by the elements of the SLB and the OMB. Even at the level of monthly anomalies the budgets are closed within uncertainties, while also indicating possible origins of remaining misclosures. [ABSTRACT FROM AUTHOR]

We constrain viscoelastic Earth rheology and recent ice‐mass change in the northern Marguerite Bay region of the Antarctic Peninsula. Global Positioning System (GPS) time series from Rothera and San Martin stations show bedrock uplift range of ∼−0.8–1.8 mm/year over 1999–2005 and 2016–2020 but ∼3.5–6.0 mm/year over ∼2005–2016. Digital elevation models reveal substantial surface lowering, but at a lower rate since ∼2009. Using these data, we show that an elastic‐only model cannot explain the non‐linear uplift of the GPS sites but that a layered viscoelastic model can. We show close agreement between GPS uplift changes and viscoelastic models with effective elastic lithosphere thickness and upper‐mantle viscosity ∼10–95 km and ∼0.1−9 × 1018 Pa s, respectively. Our viscosity estimate is consistent with a north‐south gradient in viscosity suggested by previous studies focused on specific regions within the Antarctic Peninsula and adds further evidence of the low viscosity upper mantle in the northern Antarctic Peninsula. Plain Language Summary: Over the last few decades, the glaciers of the Antarctic Peninsula have thinned tens to hundreds of meters. This unloading of the solid Earth has produced a viscoelastic response of the solid Earth. By observing this response and comparing it to viscoelastic models combined with ice unloading models, we may infer the viscoelastic properties of the Earth in this region. In this study, we estimate ice mass changes over 15 years using satellite images. Then we analyze estimates of solid Earth displacement from continuous Global Positioning System (GPS) stations attached to bedrock. When compared to the predictions of deformation from viscoelastic models with different Earth properties and ice mass change rates, we find the rate of glacier thinning must have slowed since around 2009–2010 and suggests a thin elastic lithosphere with a lower‐viscosity upper mantle underneath this region. Key Points: GPS‐measured time‐varying uplift rates ranging between ∼1.6 ± 0.8 and ∼6.0 ± 0.6 mm/year over 1999.1–2016.0 in Northern Marguerite BayGlaciers in the region generally show a reduced rate of surface lowering since ∼2009Comparing GPS and modeled viscoelastic deformation suggests a lower‐viscosity upper mantle for this region with possible thin lithosphere [ABSTRACT FROM AUTHOR]

Studies of the global sea-level budget (SLB) and the global ocean-mass budget (OMB) are essential to assess the reliability of our knowledge of sea-level change and its contributions. Here we present datasets for times series of the SLB and OMB elements developed in the framework of ESA's Climate Change Initiative. We use these datasets to assess the SLB and the OMB simultaneously, utilising a consistent framework of uncertainty characterisation. The time series, given at monthly sampling, include global mean sea-level (GMSL) anomalies from satellite altimetry; the global mean steric component from Argo drifter data with incorporation of sea surface temperature data; the ocean mass component from Gravity Recovery and Climate Experiment (GRACE) satellite gravimetry; the contribution from global glacier mass changes assessed by a global glacier model; the contribution from Greenland Ice Sheet and Antarctic Ice Sheet mass changes, assessed from satellite radar altimetry and from GRACE; and the contribution from land water storage anomalies assessed by the WaterGAP global hydrological model. Over the period Jan 1993–Dec 2016 (P1, covered by the satellite altimetry records), the mean rate (linear trend) of GMSL is 3.05 ± 0.24 mm yr−1. The steric component is 1.15 ± 0.12 mm yr−1 (38 % of the GMSL trend) and the mass component is 1.75 ± 0.12 mm yr−1 (57 %). The mass component includes 0.64 ± 0.03 mm yr−1 (21 % of the GMSL trend) from glaciers outside Greenland and Antarctica, 0.60 ± 0.04 mm yr−1 (20 %) from Greenland, 0.19 ± 0.04 mm yr−1 (6 %) from Antarctica, and 0.32 ± 0.10 mm yr−1 (10 %) from changes of land water storage. In the period Jan 2003–Aug 2016 (P2, covered by GRACE and the Argo drifter system), GMSL rise is higher than in P1 at 3.64 ± 0.26 mm yr−1. This is due to an increase of the mass contributions (now about 2.22 ± 0.15 mm yr−1, 61 % of the GMSL trend), with the largest increase contributed from Greenland. The SLB of linear trends is closed for P1 and P2, that is, the GMSL trend agrees with the sum of the steric and mass components within their combined uncertainties. The OMB budget, which can be evaluated only for P2, is also closed, that is, the GRACE-based ocean-mass trend agrees with the sum of assessed mass contributions within uncertainties. Combined uncertainties (1-sigma) of the elements involved in the budgets are between 0.26 and 0.40 mm yr−1, about 10 % of GMSL rise. Interannual variations that overlie the long-term trends are coherently represented by the elements of the SLB and the OMB. Even at the level of monthly anomalies the budgets are closed within uncertainties, while also indicating possible origins of remaining misclosures. [ABSTRACT FROM AUTHOR]

We consider the viscoelastic rheology of the solid Earth under the Antarctic Peninsula due to ice mass loss that commenced after the breakup of the Larsen-B ice shelf. We extend the previous analysis of nearby continuous GPS time-series to include five additional years and the additional consideration of the horizontal components of deformation. They show strong uplift from ∼2002 to 2011 followed by reduced uplift rates to 2018. Modelling the GPS-derived uplift as a viscoelastic response to ongoing regional ice unloading from a new ice model confirms earlier estimates of low upper-mantle viscosities of ∼0.3–3 × 1018 Pa s in this region but allows a wide range of elastic lithosphere thickness. The observed and modelled north coordinate component shows little nonlinear variation due to the location of ice mass change to the east of the GPS sites. However, comparison of the observed and modelled east coordinate component constrains the upper-mantle viscosity to be less than ∼9 × 1018 Pa s, consistent with the viscosity range suggested by the uplift rates alone and providing important, largely independent, confirmation of that result. Our horizontal analysis showed only marginal sensitivity to modelled lithospheric thickness. The results for the horizontal components are sensitive to the adopted plate rotation model, with the estimate based on ITRF2014 suggesting that the sum of residual plate motion and pre-2002 glacial isostatic adjustment is likely less than ∼±0.5 mm yr−1 in the east component. [ABSTRACT FROM AUTHOR]

Redistribution of mass over the Earth and within the mantle changes the gravity field whose variations are monitored at high spatial resolution by the presently flying GRACE space gravity mission from NASA or, at longer wavelengths, by the Satellite Laser Ranging (SLR) constellation. In principle, GRACE data allow one to study the time evolution of various Earth phenomena through their gravitational effects. The correct identification of the gravitational spatial and temporal fingerprints of the individual hydrologic, atmospheric, oceanographic and solid Earth phenomena is thus extremely important, but also not trivial. In particular, it has been widely recognized that the gravitational estimates of present-day ice mass loss in Greenland and Antarctica, and the related effect on sea level changes, depend on an accurate determination of the Postglacial Rebound (PGR) after Pleistocene deglaciation, which in turn depends on the assumed solid Earth parameters and deglaciation model. Here we investigate the effect of the uncertainty of the solid Earth parameters (viscosity, litospheric thickness) and of different deglaciation processes on PGR in Greenland and Antarctica. We find that realistic constraints to the trend in ice mass loss derived from GRACE data determine a range of variation substantially wider than commonly stated, ranging from an important ice loss of −209 Gt yr−1 to an accumulation of +88 Gt yr−1 in Antarctica, and Greenland ablation at a rate between −122 and −50 Gt yr−1. However, if we adopt the set of most probable Earth parameters, we infer a substantial mass loss in both regions, and −101 ± 22 Gt yr−1 for Antarctica and Greenland, respectively. [ABSTRACT FROM AUTHOR]

West Antarctica (WA) has the second largest ice mass loss in the world, with the potential to trigger animportant interaction with the solid Earth as observed in Amundsen Sea Embayment (ASE). There, the largemass loss is exciting a large and fast movement of the bedrock allowing us to geodynamically constrain alow viscosity in the mantle beneath. Seismic tomography and gravimetry find thermal anomalies underneathASE and even hotter areas elsewhere below WA, and recent studies suggest a plume below Marie ByrdLand (MBL). It is therefore natural to wonder if other areas in WA are characterized by low viscosity.However hot mantle does not necessarily imply low viscosity. And the geodynamic response of the Earthrequires a significantly large mass loss in order to produce measurable mantle and bedrock movement.In WA, the mass loss outside ASE is relatively small, and the GPS velocities are also quite small withrelatively large errors almost everywhere, and previous studies attributed those small velocities to the GIAcaused by the Holocene deglaciation. In addition, the elastic velocity signal produced by the ice masschanges is comparable with the observed GPS signal, leaving small room for an additional signal comingfrom low viscosity mantle displacement triggered by recent ice changes.Nonetheless, by using low viscosity Earth models we are able to assess whether the relatively small icemass loss in other areas (e.g. MBL and Bellingshausen Sea coast) could trigger a visible GPS signal. Toimprove the accuracy of our analysis we use for the first time high resolution monthly ice mass changes tocompute the time series of the Earth response to be analysed together with the GPS time series instead ofthe GPS velocity. In this way we can avoid the errors in the trend due to the variability in the time series.We find that even small ice changes could trigger measurable low viscosity GIA signal, and based on this weshow the modelled displacements assuming low viscosity mantle in regions nearby ASE and the comparisonwith the observed GPS time series. From this preliminary analysis it appears that the elastic time series hasa good correlation with the observed GPS time series, with not much room for a viscoelastic signal in theareas under study except for ASE. [ABSTRACT FROM AUTHOR]