This session aims to attract research that further advances our ability to accurately quantify hydrological mass loads across different temporal and spatial scales, and involving different hydrological compartments (e.g., groundwater, surface water, snow, ice). We invite studies focusing on innovative measurement and modeling approaches and reconciling observations from different geodetic measurement techniques used to study hydrological loading as well as the disentangling of cryospheric and hydrologic signals. Research that assesses the strengths and limitations of each approach and that proposes strategies for a seamless and accurate integration, particularly of cryospheric processes, is highly encouraged. Additionally, we seek studies that conduct intercomparisons of different hydrological model data (land surface, hydrological models) and geodetic measurement techniques to understand their relative strengths, weaknesses, and accuracies.
Orals: Mon, 4 May, 14:00–15:45 | Room 0.15
Vertical displacements of Earth’s crust recorded by a set of permanent stations of Global Positioning System (GPS) antennas are used to infer the gridded changes in Terrestrial Water Storage (TWS) using elastic loading theory. Spatial resolution of the resulting gridded TWS changes is dependent on the number of displacement observations available for the region. For several regions around the world, including Europe, dense networks of GPS stations may guarantee high spatial resolution of the inferred gridded TWS changes, far exceeding the spatial resolution of gridded TWS changes that can be obtained from the Gravity Recovery and Climate Experiment (GRACE) observations. Similarly, the daily temporal resolution of gridded TWS changes that we can infer using daily GPS displacements is extremely competitive with monthly GRACE solutions. Both improvements allow for the analysis of regional sub-monthly TWS changes. In this presentation, we showcase a dataset of daily gridded TWS changes over Europe, inferred from vertical displacements measured by more than 4,000 GPS stations across Europe, for a period of 1994-2023. We use the vertical displacements provided by the Nevada Geodetic Laboratory (NGL) and analyze them thoroughly to eliminate the displacements showing apparent changes unrelated to hydrology. We then divide the displacements into three temporal scales of short-term, seasonal and long-term changes to enhance a better understanding of the resulting gridded TWS changes and classify this set of GPS stations into hydrological benchmarks. We then use this benchmark dataset and invert the displacement time series into gridded TWS changes over Europe. We perform several comparisons on regional and local spatial scales with GRACE, hydrological models, and other datasets, and prove that the resulting TWS changes may enhance future analyses of regional hydrological changes.
How to cite: Klos, A., Lenczuk, A., and Bogusz, J.: A dataset of long daily TWS changes over Europe, inferred from vertical displacements measured by GPS, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6604, https://doi.org/10.5194/egusphere-egu26-6604, 2026.
The rapid human-driven depletion of groundwater resources across the Indian subcontinent poses a critical threat to long-term water and food security. The Northwestern Indo-Gangetic Alluvial Plain (NIGAP) is experiencing persistent groundwater depletion due to the combined effects of intensive agricultural and industrial demands. This region, situated on the seismically active Himalayan Foreland Basin, relies heavily on its vast Quaternary alluvial aquifer system. In this study, we integrate multiple geodetic approaches to quantify the secular mass loss in this water-stressed region and partition it into changes in total water and groundwater storage (TWS and GWS).
We analyze time series of TWS changes observed at 300-400 km spatial resolution by the Gravity Recovery and Climate Experiment (GRACE/GRACE-FO) missions from 2002 to 2024. These basin-scale mass estimates are compared with hydrological mass change signals inferred from high-resolution vertical land motion (VLM) derived from Interferometric Synthetic Aperture Radar (InSAR), complemented by continuous Global Positioning System (GPS) measurements. The vertical deformation field derived from InSAR and GPS data across NIGAP reveals aquifer compaction driven by pore pressure decline, enabling the quantification of GWS loss through poroelastic compaction models. However, regions outside the aquifer system exhibit elastic uplift of the Earth’s crust in response to reductions in TWS at and beneath the surface. To convert this elastic response into an equivalent TWS change, we implement an inverse elastic half-space model that incorporates observed surface deformation, along with the known elastic and hydrogeological properties of the study area.
Keywords: Groundwater Depletion, Geodetic Measurements, Elastic Half-Space, Indo-Gangetic Plain.
How to cite: More, S., Werth, S., Tiwari, V., and Tiwari, A.: Quantifying Groundwater Storage Loss in The Northwestern Indo-Gangetic Alluvial Plain Using Integrated Geodetic Measurements and Geophysical Modelling, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1643, https://doi.org/10.5194/egusphere-egu26-1643, 2026.
Variations in surface temperature and groundwater pressure within aquifer systems generate internal thermoelastic and poroelastic strain in the shallow subsurface, producing surface deformation and crustal stress perturbations. We develop a general mathematical framework to compute surface displacements and stresses at depth driven by internal strain, accounting for realistic mechanical properties of the Earth, including depth-dependent layering and lateral heterogeneities.
We show that variations in surface temperature induce deformation below layers affected by internal strain and surface horizontal displacements that scale with the Young’s modulus of the shallow layers where internal strain occurs. Because these layers generally have weak elastic moduli across continental regions (soils, weathered rock, etc.), long-wavelength thermoelastic horizontal deformation is predicted to be negligible. In contrast, vertical displacements driven by thermal expansion within shallow weak layers are expected to reach the millimeter level, implying that thermoelastic effects should be considered when interpreting GNSS signals, in particular at the annual timescale.
At regional scale, lateral contrasts in elastic properties, such as transitions from bedrock to sedimentary basins or across fault damage zones, can produce annual thermoelastic horizontal displacements up to a few mm. The associated annual thermoelastic stress perturbations at depths of a few km may reach several kPa, locally exceeding stresses induced by seasonal hydrological loading, suggesting a potential contribution of surface temperature forcing observed seasonal modulation of seismicity. Over longer timescales, progressive climate-driven warming may also cause non-negligible stress perturbations in intraplate regions.
Using the same formalism, we investigate deformation and stresses induced by poroelastic pressure variations in aquifer systems. We show that for 10 m variations of the water table, vertical displacements of a few mm to a few cm are expected and lateral variations of elastic properties can generate horizontal deformation of a few mm and crustal stress perturbations of several kPa.
How to cite: Chanard, K. and Fleitout, L.: Thermoelastic and poroelastic deformation of the solid Earth driven surface temperature and groundwater level variations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20492, https://doi.org/10.5194/egusphere-egu26-20492, 2026.
Active volcanoes often deform by magmatic activities at depth. Here we report that they deform also by hydrological activities induced by rains. By analyzing the daily coordinates of global navigation satellite system stations deployed around the Fuji volcano, the highest mountain of the country in central Japan, we detected transient surface uplift of 1-2 centimeters correlated with heavy rains. We consider they were caused by the expansion of shallow aquifers within Shin-Fuji lava layers. Such hydrological inflation of the volcano, lasting for a day or two, occurs within ~25 km from the summit. The uplift gradually decays with distance and is replaced with large-area subsidence by rainwater loading beyond the end of these lava layers. Subsidence is proportional to daily rains, rather than cumulative rains, suggesting dynamic equilibrium of precipitation and run-off. Understanding such ‘cold’ deformation of active volcanoes would help us correctly interpret ‘hot’ ones by magmatic activities.
How to cite: Heki, K., Zheng, S., Chen, J., Zhang, Z., and Yan, H.: Uplift and subsidence by heavy rains: Hydrogeodesy of Mt. Fuji, Japan, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9175, https://doi.org/10.5194/egusphere-egu26-9175, 2026.
The quantification of inland surface water storage anomaly (SWSA) and its spatial-temporal variability across rivers, streams, lakes, reservoirs, floodplains, and wetlands is crucial for understanding the role of continental water in the global hydrological and biochemical cycles. Such knowledge is also essential for sustaining human societies and ecosystems. For more than a decade, significant efforts have been devoted to characterising SWSA in some major river basins and globally for only some types of water bodies. However, global SWSA for all surface water bodies simultaneously has not yet been quantified, and its long-term behavior has not yet been investigated.
Here, we present the first global estimates of SWSA and investigate its long-term behaviour from 1992 to 2020. This is achieved by benefiting from the integration of multi-mission global satellite products, including satellite-derived Surface Water Height (SWH) from nadir altimeters and Surface Water and Ocean Topography (SWOT). Two methods have been coupled to estimate SWSA over each type of surface water body. The first one, a hypsometric curve method, consists of the combination of surface water extent (from the Global Inundation Extent from Multi-Satellite (GIEMS-2 dataset)) with topographic data from the global Digital Elevation Model (DEM), namely Forest And Buildings removed Copernicus DEM (FABDEM). The second one, based on the lake water level – area storage model, combined the simultaneous lake surface water extent and SWH. Our new SWSA dataset agrees well with other existing regional SWSA estimations.
Our results highlight the relevance of the Caspian Sea system in driving the recent global SWSA decline. At the global scale, results including the Caspian Sea provide a significant negative trend of -14 km3 yr-1. Conversely, the exclusion of the Caspian Sea shows a positive trend at 6 km3 yr-1.
The newly developed global satellite observation-based SWSA dataset enables novel insights as a new source of information for hydrological and multidisciplinary sciences, including data assimilation, land–ocean exchanges, and water management. Moreover, this global dataset is a benchmark of SWOT-based storage products and their evaluation and validation.
How to cite: M. Kitambo, B., J. Tourian, M., Saemian, P., Elmi, O., Wongchuig, S., Moreira, D., C.R Cordeiro, M., Santos Fleischmann, A., M. Tshimanga, R., Frappart, F., Prigent, C., and Papa, F.: The Caspian Sea defines the recent global inland surface water storage decline, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20281, https://doi.org/10.5194/egusphere-egu26-20281, 2026.
Total Drainable Water Storage (TDWS) represents the fraction of terrestrial water storage that can drain naturally from a basin. It is a key indicator of basin-scale hydrological responses, acting as a proxy for a basin’s water-retention capacity and availability for ecosystems and society. Satellite gravimetry provides a unique observational constraint on terrestrial water storage changes by sensing gravity variations caused by the redistribution of water mass on and beneath the land surface. While current missions such as GRACE and GRACE-FO successfully observe total water storage anomalies, they do not measure absolute water storage or any proxy of it. TDWS must therefore be inferred by interpreting gravity-based storage changes through the storage–runoff relationship, which governs how storage variations translate into drainage and river discharge. However, the limited effective spatial resolution of current gravity missions restricts robust analyses to large river basins and prevents investigations of smaller basins and sub-basin-scale hydrological processes. These limitations lead to the question of what improvements in TDWS estimation can be expected from next-generation gravity missions with enhanced spatial resolution and sampling.
In this study, we assess the potential impact of next-generation gravity missions, specifically NGGM and MAGIC, on the global-scale estimation of TDWS. We use simulated gravity observations, with two generations of the ESA Earth System Model (ESM2.0 and ESM3.0) providing the Total Water Storage Anomaly (TWSA) as the reference signal. TDWS is then estimated using a storage–runoff relationship, with TWSA representing storage and runoff taken from in situ observations. All mission scenarios, including GRACE-C, NGGM, and MAGIC, are processed using an identical TDWS estimation framework, ensuring that differences in the resulting TDWS parameters arise solely from mission design characteristics such as spatial resolution, temporal sampling, and noise levels.
Mission performance is evaluated at the basin scale by comparing basin-averaged total water storage anomalies and TDWS-related parameters against ESM reference values. The impact of each mission is quantified in terms of (i) accuracy, defined as the closeness of mission-based parameters to the model reference, and (ii) parameter uncertainty, assessed through confidence intervals derived from the storage–runoff fitting. The analysis is further stratified by basin size, storage–discharge coupling, and hydrological complexity.
The results show that NGGM and MAGIC reproduce basin-scale TDWS parameters more accurately than a GRACE-C–like scenario, particularly for smaller basins. Comparison with the ESM reference demonstrates that future missions reduce parameter errors, tighten confidence intervals, and better capture differences in hydrological behavior across basins. At the same time, the study demonstrates that improved gravity observations must be complemented by physically meaningful storage–runoff relationships to fully exploit the potential of future missions. A comparison between results obtained from ESM2.0 and ESM3.0 is therefore required to assess how advances in the representation of basin-scale hydrological processes affect the evaluation of future mission impacts on complex hydrological behavior.
This work was carried out within the SING project, funded by the European Space Agency under the ‘NGGM and MAGIC Science and Applications Impact Study’ ESA Contract No. 4000145265/24/NL/SC.
How to cite: Sobouti, A., Tourian, M. J., Saemian, P., Xiao, C., Kitambo, B., and Sneeuw, N.: Assessing the Potential of Next-Generation Gravity Missions for Estimating Total Drainable Water Storage, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5720, https://doi.org/10.5194/egusphere-egu26-5720, 2026.
Arctic coasts are among the most vulnerable landscape on Earth, where periglacial terrain undergoes thermal contraction and expansion through seasonal freeze–thaw cycles. Along the Utqiaġvik (formerly Barrow), Alaska coastline, shifting thermal regimes have accelerated ice wedge degradation, influenced by the evolution of polygonal trough networks. However, accurately mapping trough structure, variability, and hydrologic connectivity across spatial scales remains challenging. This study integrates high-resolution remote sensing and terrain modeling to investigate the relationship between surface hydrology and ice wedge polygon morphology. Using a 0.5 m resolution LiDAR-derived digital elevation model (DEM), ice wedge polygons were manually delineated and compared with Thiessen (Voronoi) polygons to evaluate differences in structure, spatial extent, and representation of natural variability. Intersection analyses revealed significant discrepancies in boundary alignment and area estimates between the two approaches. Hydrologic influences on polygon development were assessed through compound terrain analysis, drainage network extraction, and surface flow modeling. Results show strong spatial correspondence between modeled flow paths and mapped trough networks, indicating that surface hydrology plays a key role in ice wedge thaw and trough evolution. Calculated hydrologic and morphometric parameters suggest high runoff potential, driven by flat terrain, permafrost-limited infiltration, dense drainage networks, and short overland flow paths. High TWI (> 12) and SPI (> 60) values mark zones of concentrated surface saturation and flow accumulation, often coinciding with trough depressions. Despite high runoff potential, minimal gradients lead to slow-moving flow and persistent surface ponding, contributing to widespread wetland formation. This integrated approach demonstrates the value of combining high-resolution topographic data with hydrologic modeling to improve detection and interpretation of permafrost terrain features. The framework developed offers a scalable method for monitoring Arctic terrain dynamics and enhances remote sensing applications for assessing permafrost vulnerability.
How to cite: Richards IV, D., Merrick, T., Liang, R., Abelev, A., Vermillion, M., Maciel-Seidman, M., and Grossman, S.: Remote Sensing-Based Framework for Detecting and Interpreting Permafrost Terrain Hydrologic Connectivity, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22109, https://doi.org/10.5194/egusphere-egu26-22109, 2026.
The Kerguelen Islands (49°S, 69°E), a volcanic archipelago in the southern Indian Ocean, have experienced substantial environmental change over recent decades, including significant retreat of the Cook ice cap. The rapid ice loss is expected to induce measurable crustal deformation.
In this study, we use the complete archive of Sentinel-1 SAR imagery acquired since 2015 to examine the present-day deformation field of the Kerguelen Islands. Our small-baseline InSAR time-series analysis reveals a broad ~ 100 km-wide pattern of crustal uplift centered on the Cook ice cap, reaching up to ~ 6 mm/yr.
To investigate the physical processes driving this uplift, we combine observed change in ice elevation inferred from multiple Digital Elevation Model over the 2015-2025 period with local estimates of shallow elastic properties derived from seismic experiments. Using a layered Cartesian elastic Earth model, we predict the surface deformation resulting from present-day unloading of the Cook ice cap, and compare model predictions to the InSAR-derived deformation field.
We then explore time-dependent deformation scenarios by considering viscoelastic deformation of the solid Earth induced by a range of plausible ice-loss histories over recent decades, and show that recent ice melting in the Kerguelen island can be used to place constraints on the rheology of the Earth’s upper mantle at decadal timescales. Finally, given the volcanic setting of the Kerguelen Islands, we also investigate whether magmatic sources could contribute to the observed long-wavelength uplift pattern.
Overall, this work highlights the potential of InSAR observations in remote subpolar environments to quantify ice-driven deformation and to infer solid Earth rheological properties on decadal timescales.
How to cite: Spriet, C., Chanard, K., Grandin, R., Berthier, É., Gobron, K., Gauer, L.-M., and Fleitout, L.: Crustal uplift in the Kerguelen Islands from Sentinel-1 InSAR : A consequence of recent ice melting?, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17316, https://doi.org/10.5194/egusphere-egu26-17316, 2026.
The Antarctic Peninsula (AP), encompassing the ice sheet and its peripheral glaciers, is a highly dynamic component of the cryosphere, disproportionately contributing to sea level rise. However, a large spread remains between the mass changes estimated using gravimetry, altimetry and the input/output method. Among these techniques, the satellite (radar or laser) altimetry method has a resolution of, at best, 1 km, which is too coarse to resolve the complex pattern of changes in the Peninsula. Therefore, we use digital elevation models (DEMs; 30x30 m) to map elevation changes for the entire Peninsula, combining 476 DEMs derived from SPOT5-HRS satellite images (2006-2008) and 2525 strips of the Reference Elevation Model of Antarctica (2020-2022) to provide a comprehensive 14-year record. We bias-corrected each DEM using near-synchronous ICESat/-2 laser altimetry measurements.
Our observations cover 70% of the AP ice sheet and 60% of its peripheral glaciers, including for regions of the Peninsula poorly studied to date and decipher a spatially complex pattern of elevation changes. After correction with different models of firn air content and solid-earth response, we find that between 2007 and 2021, the AP ice sheet lost -27 ± 9 Gt/yr while its peripheral glaciers lost -14 ± 2 Gt/yr. For the AP ice sheet, our new estimate is 4 to 5 times more negative than the one obtained in IMBIE using purely altimetry data (-6 ± 6 Gt/yr from 2006 to 2018) and in better agreement with gravimetry and the input/output method. Our study highlights the importance of resolving fine scale elevation changes of glaciers and ice sheets.
How to cite: Bernat, M., Berthier, E., Dehecq, A., Hugonnet, R., Belart, J. M., Ochwat, N., Scambos, T., Kuipers Munneke, P., Case, E., Gauer, L.-M., and Youssefi, D.: Mass Loss of the Antarctic Peninsula ice sheet and its peripheral glaciers from 2007 to 2021, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16776, https://doi.org/10.5194/egusphere-egu26-16776, 2026.
Determining the mass balance of Antarctica by satellite gravimetry, altimetry and input-output methods is still suffering from large discrepancies between methods, especially for East Antarctica. Error sources for the different estimation methods include GIA for GRACE/GRACE-FO, firm compaction for satellite altimetry, and poorly known interior snow fall and grounding line mass flux for outlet glaciers in the input-output method. To narrow down uncertainties for the latter, an international SCAR project “RINGS” was initiated in 2023, aiming as a primary goal to cover all major unmapped outlet glaciers with new radar ice thickness data in the coming years. A unique multi-disciplinary airborne remote sensing RINGS campaign was carried out as part of a first circumnavigation of Antarctica 2024/25, using a Twin-Otter as dedicated science aircraft. The airborne campaign instruments included a 30 GHz deep ice sounding radar, a 5 GHz broadband snow radar, along with scanning lidar, nadir and side-looking imagery, and gravimetry, as well as atmosphere monitoring sensors for chemistry and aerosols. In the presentation we outline the results of the RINGS airborne campaign, the impact on the input-output method of the new outlet glacier thicknesses, and compare the changes to current GRACE/GRACE-FO mass balance results.
How to cite: Forsberg, R., Leuschen, C., Stokholm, A., Li, J., Jensen, T., Arnold, E., and Rodriguez-Morales, F.: Enhanced mass balance of Antarctica from RINGS airborne grounding line survey, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18216, https://doi.org/10.5194/egusphere-egu26-18216, 2026.
All geodetic technique observations (DORIS, GNSS, SLR and VLBI) have been processed up to the end of 2024 in order to compute the second update of the International Terrestrial Reference Frame 2020, namely ITRF2020-u2024 (https://itrf.ign.fr/en/solutions/ITRF2020-u2024). Following the IERS conventions, no environmental loading corrections have been applied besides ocean tides.
We also compute daily GNSS solution using the GINS software in iPPP (precise point positioning with integer ambiguity resolution) for the 2000-2025 period, and orbit/clock products from the CNES/CLS analysis center.
In parallel, the IERS Global Geophysical Fluid Center has provided atmospheric, induced oceanic and hydrological loading estimates for all permanent stations based on the latest ECWMF reanalysis (ERA5) and the barotropic ocean model TUGO-m (http://loading.u-strasbg.fr/ITRF2020/).
In this paper, we present a comparison of both the combined ITRF2020-u2024 and our daily GNSS residual displacements to environmental (atmosphere, ocean and continental hydrology) loading estimates. In more details, we show that the ERA5-based reanalyzes are in better agreement with the geodetic observations than the MERRA2 (Modern-Era Retrospective Analysis for Research and Applications, Version 2) reanalysis. We also show the improvement of the ERA5-land, a re-run of the land component of the ECMWF ERA5 climate reanalysis, versus the original ERA5 hydrological component.
Finally, we also show that a dynamic ocean response to pressure and wind is more suitable to model high frequency ocean non-tidal loading effects than the classical inverted barometer (IB) approximation.
How to cite: Boy, J.-P., Rebischung, P., and Altamimi, Z.: Comparison of GNSS residuals displacementswith environmental loading models, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11420, https://doi.org/10.5194/egusphere-egu26-11420, 2026.
GFZ provides elastic surface deformation estimates caused by atmospheric surface pressure, ocean bottom pressure, terrestrial water storage, and barystatic sea level variations on global grids. To keep those loading deformations consistent with the latest GRACE de-aliasing products AOD1B R07 we updated the loading products by using ECMWF ERA5 atmospheric forcing, the latest MPIOM ocean model, and the latest hydrological model release from LISFLOOD. We present some statistics on the new ESMGFZ loading deformation products to demonstrate its enhanced long-term stability and suitability for the realization of future high accurate terrestrial reference systems. Especially the hydrological loading component benefits now from the new LISFLOOD terrestrial water storage estimates forced with ECMWF ERA5 atmospheric data and simulated on a global high spatial resolution grid of 0.05° to resolve high deformation amplitudes in the vicinity of large rivers, lakes, and dams. The new ESMGFZ loading products cover the period 1960 to the present.
How to cite: Dill, R., Dobslaw, H., and Jensen, L.: New ESMGFZ loading products for global long-term stable elastic surface deformations consistent with ECMWF ERA5 and GRACE de-aliasing AOD1B 07, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17254, https://doi.org/10.5194/egusphere-egu26-17254, 2026.
Seasonal deformation related to mass redistribution on the Earth’s surface can be recorded by continuous global positioning system (GPS) and simulated by surface loading models. In this study, we compared the three-dimensional seasonal deformation from 27 continuous GPS stations and surface loading models in Yunan, China. A good consistency of vertical seasonal variations can be observed between GPS and loading models, while obvious discrepancies exist in the horizontal seasonal deformation between them, especially for the East component. The reduction ratios of the median amplitudes of GPS annual variations obtained with loading corrections are 39.37%，-18.01% and 56.39% for the North, East and Up components respectively. We found that the significant difference in horizontal annual deformation between GPS and loading models is primarily attributed to the discrepancies of GPS annual phases at different stations. Seasonal vectors are employed to discriminate loading at different spatial scales. The results suggests that the large-scale load is concentrated in the southwest of Yunnan, the disordered horizontal annual phase may be related to local-scale mass loading. In addition, after removing the loading deformation from GPS time series, GPS vertical velocity uncertainties are significantly reduced, with the mean reduction ratio about 9%.
How to cite: Niu, Y., Su, G., Li, L., Zhan, W., Li, M., and Wu, Y.: Analysis of Three-Dimensional Seasonal deformation induced by GPS and loading models in Yunnan, China, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8530, https://doi.org/10.5194/egusphere-egu26-8530, 2026.
Changes in terrestrial water storage (TWS) induce measurable elastic deformation of the Earth’s surface, known as hydrological loading. GNSS observations quantify these surface deformations and, despite being point measurements, they contain the full spectrum of the hydrological loading. Likewise, GRACE and GRACE-FO satellite missions support the monitoring of these hydrological loads, but their coarse spatial resolution (i.e., long-wavelength components) limits the characterization of short-wavelength and localized hydrological processes. Given these two different yet complementary geodetic remote sensing technologies, recent efforts have been made to combine them for recovering high-resolution TWS fields.
Building on these recent efforts, we adopted a remove-restore framework, a widely used technique in regional gravity field modeling, to invert TWS variations from GNSS-derived vertical displacements. In this framework, GRACE-based hydrological loading is first synthesized into vertical deformation up to degree and order 60, and then removed from GNSS observations, isolating residual displacements dominated by sub-GRACE-scale hydrological signals (i.e., short-wavelength components). These residuals are then inverted using a modified elastic Green’s functions to recover residual high-resolution TWS anomalies, which are subsequently restored with the long-wavelength GRACE signal to obtain high-resolution TWS anomaly fields. We applied the method to Chile, a region characterized by strong hydro-climatic gradients and significant tectonic activity, which served as a challenging testbed for the inversion of hydrological loading into high-resolution TWS.
Our results showed that the remove–restore approach enhances both the spatial detail and amplitude of TWS variations compared to GRACE alone, while preserving consistency with large-scale mass changes. Comparisons with land surface and hydrological model outputs indicated improved representation of regional and local hydrological variability. Overall, this exercise demonstrates the potential of integrating GNSS and GRACE/GRACE-FO through a remove-restore strategy to reconcile complementary geodetic observations and better resolve multi-scale water storage dynamics.
How to cite: Ferreira, V., Zeng, Z. B., and Montecino, H.: High-resolution terrestrial water storage from GNSS vertical deformation using a remove–restore hydrological loading framework: Application to Chile, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6155, https://doi.org/10.5194/egusphere-egu26-6155, 2026.
Hydrological monitoring methods usually observe water storage changes in specific depths or for a limited number of storage compartments and are often representative for a small volume only. In contrast, gravity measurements are sensitive to mass changes as a spatially integrated signal. This makes them a valuable complementary tool for monitoring total water storage changes. The hydrological contribution to the time-variable gravimetric signal often plays a major role for the overall signal dynamics. Nevertheless, there is still a lack of understanding the influence of the local hydrological dynamics at many terrestrial gravity stations. Thus, advancing the hydrological corrections of gravity signals is highly valuable for improving the interpretation of gravity measurements with respect to other processes of interest, e.g., geodynamic, atmospheric or ocean-loading effects. At the same time, high-precision gravity measurements provide a reliable validation to mass-variations as represented by hydrological models.
In this case study, we consider the Geodetic Observatory Wettzell (GOW), located in the river Regen catchment in a low mountain range in East Bavaria, Germany. Here, long-term stable records of superconducting gravimeters (SGs) are available at three different points at the observatory within a distance of about 200 meters. Moreover, an extensive hydrological sensor network has been operated at GOW for more than a decade, which allows for a precise consideration of local effects. Dividing the hydrological effects into local, regional and global contributions, the regional component is calculated based on the mesoscale Hydrologic Model (mHM, Helmholtz Centre for Environmental Research – UFZ), implemented for the river Regen catchment with a spatial resolution of one kilometer and forced with national and global meteorological data sets. Global contributions are considered from various models, including MERRA-2 and several GLDAS solutions.
To assess the efficiency of a small-scale versus a large-scale approach for hydrological corrections, we evaluate all hydrological contributions against gravity residuals, after precise removal of tides, atmospheric, non-tidal ocean loading and polar motion effects. We focus on the consistent combination of each contribution and the impact of local influences, e.g., finely resolved topography in the vicinity of the gravimeters and the effect of buildings. First results show that changing the approach for, or neglecting the local contribution can easily double the total hydrological effect. This emphasizes the importance of carefully considering local effects in the hydrological gravity modelling, in particular at stations with a marked subsurface complexity and heterogeneity like GOW.
How to cite: Winter, A., Reich, M., Yeste, P., Antokoletz, E. D., Güntner, A., and Wziontek, H.: Evaluating different-scale hydrological corrections against high-precision terrestrial gravity time series at the Geodetic Observatory Wettzell, Germany, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20596, https://doi.org/10.5194/egusphere-egu26-20596, 2026.
Modelling crustal loading deformations is crucial for various geodetic applications, including the realization of precise and stable terrestrial reference frames. Commonly, hydrological, atmospheric and oceanic models are used to predict surface deformations. But also cryospheric deformations are not negligible considering the accelerating melting of glaciers, and glacier models exist to estimate cryospheric mass variations. However, it is not appropriate to just complement the existing hydrological model with the glacier model estimates as part of the glacier induced deformations are already taken into account by the hydrological model via simplified snow routines, which would lead to double-counting of masses.
A consistent way to consider glacier mass variations in deformation studies would be to couple a hydrological model with a glacier model. While on a basin scale this has been done before, large-scale or even global coupling approaches are still rare partly due to the heterogeneous glacier behavior and relatively small extent of glaciers (often smaller than the grid cell size of the global model). The Open Global Glacier Model (OGGM) is designed for global glacier modelling, and thus, a suitable candidate for a global coupling. Here we present first steps towards coupling OGGM with OS LISFLOOD, an open-source global hydrological model running with a global 0.05° spatial resolution previously used for geodetic applications.
As a first case study, we chose the Fraser river basin in North America. We initially conduct model runs separately with OGGM for selected glaciers contained in the study area, and with OS LISFLOOD to obtain mass storage estimates particularly for the snow compartment. Comparison of both model results gives an impression of the potential double-counting of mass if both models were applied separately, and reveals challenges in a possible coupling workflow. For example, OGGM output is stored per glacier, and thus has to be summed per grid cell in order to pipeline it to grid-based OS LISFLOOD. Furthermore, OS LISFLOOD would have to be adjusted to take input from OGGM in glaciated regions with varying extent.
How to cite: Dobslaw, H., Dill, R., and Jensen, L.: Towards the coupling of a glacier and a hydrological model (OGGM and OS LISFLOOD) for improved loading estimations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21216, https://doi.org/10.5194/egusphere-egu26-21216, 2026.
Glaciers are vulnerable to the impacts of climate change, making them a dynamic and rapidly transforming element of the Earth system. The consequences of these changes extend far beyond the polar and mountain regions, affecting ecosystems and water resources globally. Challenges such as flood risks and hazards like rock moraines underscore the importance of understanding this part of the ecosystem. Monitoring and measuring glacial environments are essential not only for mitigating risks but also for advancing scientific knowledge. By studying the dynamics of glaciers, scientists can gain a deeper understanding of their interactions with the Earth's climate system and better predict future changes.
The alpine glaciers have been research areas of several institutes for different geodetic sensors for over 150 years. The current challenge lies in leveraging observational data to develop a glacier model that can assimilate geodetic observations. This research aims to design an optimized geodetic sensor network that enhances the integration of field observations into glacier modeling. Both simulations and real-data processing should be considered. Sensitivity studies evaluate first the data products themselves and second the model’s response to various data inputs, identify observation errors, and refine the network design.
At this stage, a framework for a closed-loop simulation environment tailored to the Hintereisferner is presented. This environment should enable systematic assessment of sensor performance, network accuracy, and future scalability on a simulation basis. Spatial and temporal resolution of the ground truth and the observation methods are discussed. Different sensors are introduced in terms of spatial resolution and measurement accuracy. Initial results from sensitivity studies using different sensors are presented. Additionally, challenges in implementing the simulation environment are discussed.
How to cite: Lechner, K., Rückamp, M., and Pail, R.: First Results for Simulation Environment using Multi-Sensor Network Observing Hintereisferner , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5221, https://doi.org/10.5194/egusphere-egu26-5221, 2026.
During summer 2025, an Absolute Quantum Gravimeter (AQG, manufactured by Exail) was deployed for one week in western Greenland to explore the potential of quantum gravimetry for geodetic observations in an Arctic environment - under remote and harsh field conditions - and to evaluate the sensitivity of absolute gravity measurements to mass redistribution processes associated with glacier dynamics and solid Earth deformation.
For most of the week, the AQG collected measurements at an established gravity point in the hangar of Ilulissat airport (ILUL). For one day, the instrument was transferred by helicopter to another established gravity point in the bedrock near the Greenland Ice Sheet, approximately 50 km inland along the Ilulissat ice stream. The point is co-located with the Kangia North (KAGA) permanent GNSS station, enabling a direct link between absolute gravity, surface deformation and cryospheric mass change signals. The station is located in proximity of the calving front of the Ilulissat glacier, one of the fastest-flowing and most dynamically active glaciers in Greenland.
In this contribution, we present preliminary results from the 2025 campaign and compare them with previous absolute gravity measurements obtained using an absolute A10 gravimeter at both sites. These time-separated absolute gravity observations provide a basis for assessing the potential of AQGs to monitor gravity variations associated with ice and water mass changes together with Glacial Isostatic Adjustment (GIA). We discuss the significance of the observed values, compare them with predicted gravity trends, and assess the credibility and uncertainty of the results under Arctic field conditions. The AQG observations are evaluated as a complement to GNSS and classical absolute gravimetry as a geodetic method for long-term cryospheric monitoring, with the 2025 campaign serving as a baseline for future repeated measurements. The expedition serves as a pilot study for repeated quantum gravimetry observations in Greenland, planned to be continued with a similar instrument in summer 2028.
The campaign was carried out within the project EQUIP-G (funded by the European Commission under the Horizon Europe program, grant number 101215427) and with support from the Danish Climate Data Agency.
How to cite: Jensen, T. E., Dykowski, P., and Ciesielski, A.: Terrestrial Quantum Gravimetry for Climate Monitoring: First Measurements in Greenland, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14041, https://doi.org/10.5194/egusphere-egu26-14041, 2026.
