G3.1 | Geodesy for Climate Research
Geodesy for Climate Research
Co-organized by CL5/OS4
Convener: Bramha Dutt Vishwakarma | Co-conveners: Anna Klos, Benoit Meyssignac, Vincent Humphrey, Carmen Blackwood
Orals
| Wed, 17 Apr, 14:00–18:00 (CEST)
 
Room D1
Posters on site
| Attendance Thu, 18 Apr, 16:15–18:00 (CEST) | Display Thu, 18 Apr, 14:00–18:00
 
Hall X2
Orals |
Wed, 14:00
Thu, 16:15
This session invites innovative Earth system and climate studies employing geodetic observations and methods. Modern geodetic observing systems have been instrumental in studying a wide range of changes in the Earth’s solid and fluid layers at various spatiotemporal scales. These changes are related to surface processes such as glacial isostatic adjustment, the terrestrial water cycle, ocean dynamics and ice-mass balance, which are primarily due to changes in the climate. To understand the Earth system response to natural climate variability and anthropogenic climate change, different time spans of observations need to be cross-compared and combined with several other datasets and model outputs. Geodetic observables are also often compared with geophysical models, which helps in explaining observations, evaluating simulations, and finally merging measurements and numerical models via data assimilation.

We look forward to contributions that:​

1. Utilize geodetic data from diverse geodetic satellites including altimetry, gravimetry (CHAMP, GRACE, GOCE and GRACE-FO, SWOT), navigation satellite systems (GNSS and DORIS) or remote sensing techniques that are based on both passive (i.e., optical and hyperspectral) and active (i.e., SAR) instruments.​

2. Cover a wide variety of applications of geodetic measurements and their combination to observe and model Earth system signals in hydrological, ocean, atmospheric, climate and cryospheric sciences.​

3. Show a new approach or method for separating and interpreting the variety of geophysical signals in our Earth system and combining various observations to improve spatiotemporal resolution of Earth observation products.​

4. Work on simulations of future satellite mission (such as MAGIC and NGMM) that may advance climate sciences.​

5. Work towards any of the goals of the Inter-Commission Committee on "Geodesy for Climate Research" (ICCC) of the International Association of Geodesy (IAG).​

We are committed to promoting gender balance and ECS in our session. With author consent, highlights from this session will be tweeted with a dedicated hashtag during the conference in order to increase the impact of the session.

Orals: Wed, 17 Apr | Room D1

Chairpersons: Bramha Dutt Vishwakarma, Benoit Meyssignac, Carmen Blackwood
14:00–14:20
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EGU24-14224
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ECS
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solicited
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On-site presentation
Jessica Fayne

Climate change is driving extreme spatial and temporal variability in surface water resources. This is particularly important for lake and wetland features, which have been under-characterized on the global scale. This under-characterization is largely due to the complex structural properties of these surfaces relative to available remote sensing data.  

The Surface Water and Ocean Topography Mission, as the first-of-its-kind 2D mapping and satellite interferometer using Ka-band SAR, was developed for mapping water surface extents and water surface elevations, providing a significant improvement in how we characterize and monitor surface water. Because of the novelty of the Ka-band SAR data for surface mapping, there have been limited studies of additional utilities SWOT can provide to complement water surface extent and elevation observations.  

First-look images from SWOT over Toulouse, France and Long Island, New York, USA, revealed strong signal returns over non-water surfaces, including agricultural fields and urban regions. Subsequent images highlighted by the SWOT Science Team also demonstrated wind-driven water surface signal variability, akin to NASA-JPL airborne AirSWOT investigations.  

This project provides early assessments of SWOT phenomenology for estimating characteristics that could contribute to novel datasets, such as wind speed, wind direction (for long wave formations), vegetation moisture, vegetation structure, and land surface moisture fraction. This work provides the foundation for a multi-year study to further develop the Ka-band Phenomenology Scattering Model (KaPS), and the wind model Ka-SWOT Model (Ka-SMOD), and will additionally discuss necessary reference datasets, models, and in-situ sampling necessary to complete this these assessments.

This project will increase the utility of the SWOT mission for studying diverse water and land features and significantly improve our understanding of fine-scale terrestrial hydrology. Given the relatively short temporal availability of the preliminary SWOT data, this work will focus on spatial variability across global sites, within the fast-sampling orbit, for observations taken for available dates in 2023. This preliminary analysis of the spatial and temporal variability of SWOT-derived phenomena aims to demonstrate how SWOT can be used in novel ways to study climate change. 

How to cite: Fayne, J.: Climate Change Studies through SWOT Phenomenology Research, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14224, https://doi.org/10.5194/egusphere-egu24-14224, 2024.

14:20–14:30
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EGU24-12785
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On-site presentation
Ole Baltazar Andersen, Steve Nerem, and Bjarke Nielsson

Since the beginning of the precision satellite altimeter era in the early 1990s, efforts have been focused on computing the mean height of the ocean surface for use in various geodetic and oceanographic studies. With 30 years of satellite measurements now available, it is time to rethink how we model the mean sea surface (MSS) in the era of climate change.

There are linear changes in the height of the ocean surface due to melting ice and increasing ocean heat content that will not average to zero when computing the mean. Today, there are places in the ocean that are 15 cm higher than they were at the start of the altimetric era some 30 years ago. Today, conventional MSS models like CLS15/22 or DTU15/21 are roughly 5 cm lower than what is observed by present-day satellites like Sentinel6-MF.

We propose that linear sea level changes are estimated simultaneously and consistently with the mean sea surface computation and added to the definition of the MSS, which is tied to a particular date in time. This is possible because the MSS are tied to the 2003.01.01 period for the DTU MSS models. 

We also investigated the acceleration of sea surface height but found these small and still unstable [Nerem et al., 2018]. We also found that these are still somewhat dependent on the Side A correction of the TOPEX mission. We conclude that a longer time series is needed before a stable map of the accelerations can be computed and applied.

There is considerable evidence that using a 30-year trend pattern in sea surface height is stable and is driven by the “forced response” of Greenhouse gases and aerosols. These patterns will be reasonably persistent as we move forward in time.

Testing a new DTU23MSS mean surface tailored to the year 2023 to our processing of the recently available 2023 SWOT data, we find this new DTU23MSS reduces the spatial variability of the SWOT data which is important to the processing and particularly the roll-error correction applied to the 2D SWOT sea surface height data. Applying the new DtU21MSS to conventional satellites like Sentinel-3A/B and 6 reduces both offset and spatial variability of the data indicating that the new MSS is actually very close to a “present-day mean”

 

How to cite: Andersen, O. B., Nerem, S., and Nielsson, B.: Consistent Mean Sea Surface and sea level change estimation in the Era of Climate Change – application to SWOT processing. , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12785, https://doi.org/10.5194/egusphere-egu24-12785, 2024.

14:30–14:40
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EGU24-16813
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On-site presentation
Marie Bouih, Anne Barnoud, Robin Fraudeau, Gilles Larnicol, Anny Cazenave, Benoit Meyssignac, Alejandro Blazquez, Martin Horwath, Thorben Döhne, Jonathan Bamber, Anrijs Abele, Stéphanie Leroux, Nicolas Kolodziejcyk, William Llovel, Giorgio Spada, Andrea Storto, Chunxue Yang, Sarah Connors, Marco Restano, and Jérôme Benveniste and the SLBC_cci+ team

The closure of the Sea Level Budget (SLB) at monthly, yearly, and interannual scales, with the utmost precision, remains a fundamental challenge in modern physical oceanography. Firstly, this closure is crucial to assert that all major contributors to sea level variability are accurately identified and quantified. Secondly, it serves as a valuable means for cross-validating complex global observation systems, such as the Argo in-situ network, satellite gravimetry missions GRACE/GRACE-FO, and the satellite altimetry constellation, while closely monitoring their performances. Thirdly, this closure proves to be an effective approach for testing the consistency of various observed variables within the climate system, including sea level, ocean temperature and salinity, ocean mass, land ice melt, and changes in land water storage, in accordance with conservation laws, notably those governing mass and energy.

In this presentation, we will share the latest results obtained for the sea level budget, including 1) an up-to-date estimate of the global mean budget closure from 1993 to 2022; 2) advancements in the analysis of regional patterns of each component of the budget, as well as of the budget residuals, allowing the identification of regions where the SLB does not close, with a focus on the North Atlantic and the Arctic Ocean where the residuals are significantly high. When and where the SLB closes, we can interpret the causes of the total sea level variations. The analysis at regional scales allows us to assess the relative importance of the individual components all over the oceans. When the SLB does not close, we investigate in each component the potential errors causing non-closure (e.g., in-situ data sampling, geocenter correction in gravimetric data) and how potential inconsistencies in their processing can impact large-scale patterns (e.g., geocenter and atmosphere corrections).

Future works will address questions related to the structural deficiency of the observing system, inconsistent effective resolution across different observing subsystems (in-situ data, satellite gravimetry, and satellite altimetry), potential measurement errors in a single observing subsystem, and the isolation of errors in terms of time and space. To address these questions, we will assess an SLB using synthetic components derived from oceanic models. This novel approach will enable us to estimate the spatial and temporal resolutions inherent in each observation, thereby enhancing the estimation of their respective uncertainties. We will also analyse the signature of internal climate variability on sea level budget components interannual changes, by using state-of-the-art model simulations and reanalyses.

This work is performed within the framework of the Sea Level Budget Closure Climate Change Initiative (SLBC_cci+) programme of the European Space Agency (ESA).

How to cite: Bouih, M., Barnoud, A., Fraudeau, R., Larnicol, G., Cazenave, A., Meyssignac, B., Blazquez, A., Horwath, M., Döhne, T., Bamber, J., Abele, A., Leroux, S., Kolodziejcyk, N., Llovel, W., Spada, G., Storto, A., Yang, C., Connors, S., Restano, M., and Benveniste, J. and the SLBC_cci+ team: Global mean and local sea level budget from updated observations andresiduals analysis (SLBC_cci+ project), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16813, https://doi.org/10.5194/egusphere-egu24-16813, 2024.

14:40–14:50
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EGU24-11963
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ECS
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On-site presentation
Matthias O. Willen, Bert Wouters, Taco Broerse, Eric Buchta, and Veit Helm

An effective spatial resolution of a few hundred kilometres, typically assessed for mass variations derived from GRACE/GRACE-FO data, is a major limitation for the rigorous investigation of local causes of mass variations. This is crucial for analyzing mass changes of the West Antarctic Ice Sheet, which is one of the tipping elements in the Earth’s climate system. In this region, ice mass changes occur on spatial scales smaller than the typical GRACE/GRACE-FO resolution. Furthermore, this is also the case for the solid-Earth deformation induced by ice load changes, which in turn can affect the glacier flow. Especially in the Amundsen Sea Embayment, mass changes due to the ongoing Glacial Isostatic Adjustment (GIA) have been postulated to vary on spatial scales smaller than 200 km and to feed back significantly on ice flow dynamics. Here, we present results from a data combination approach with a focus on the Amundsen Sea Embayment, West Antarctica. This approach utilizes data from GRACE/GRACE-FO and CryoSat-2 satellite altimetry with regional climate and firn model results over a time span of 10 years from 2011 to 2020. Improved GRACE/GRACE-FO gravity-field processing and a study area in a high latitude region, where the signal-to-noise is high, benefit a high spatial resolution of the results. One processing step is the smoothing of the input data sets in order to unify their different spatial resolution. We find a best fit of the combination results with independent GNSS observations by applying a Gaussian smoother of 135 km half-response width. The weighted rms difference is 3.8 mm/a in terms of estimated bedrock motion. It is almost twice as large when the input data sets are smoothed with a 300 km half-response filter. The determined effects of solid-Earth deformation may be a useful boundary information for GIA modelling in this region, e.g. for testing rheological models or (centennial) glacial histories.

How to cite: Willen, M. O., Wouters, B., Broerse, T., Buchta, E., and Helm, V.: Combination of GRACE/GRACE-FO and CryoSat-2 data resolves Glacial Isostatic Adjustment spatially and temporally in the Amundsen Sea Embayment, West Antarctica, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11963, https://doi.org/10.5194/egusphere-egu24-11963, 2024.

14:50–15:00
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EGU24-11913
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ECS
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On-site presentation
Shuxian Liu and Roland Pail

Since March 2002, the Gravity Recovery and Climate Experiment (GRACE) satellite and its following mission GRACE-FO have measured the time-variable gravity fields of the Earth, by which water shifts around Earth can be captured. Among its innovations, GRACE has monitored the change of ice mass from Earth's ice sheets and glaciers, which is essential for the better understanding of the changing climate system. Over the past few decades, glacier mass loss has been significant across the globe. The European Alps are among the regions experiencing the greatest shrinkage of glaciers, which becomes the main focus of this work.
In this work, we will challenge the information of satellite gravimetry, hydrological models, and satellite geodesy to monitor the ice mass loss in the Alps in central Europe. The temporal variations of total water storage (TWS) in the Alpine region are determined from GRACE- and GRACE-FO-based Level-2 products provided by COST-G and Mascon surface mass change fields calculated by JPL. Furthermore, the correction of GIA effects and hydrological signals in the study area is indispensable to isolate the estimate of glacier melting. For the GIA correction, the GIA model ICE-6G_D and the regional dataset of surface displacements obtained from geodetic observation techniques are applied to GRACE data respectively, resulting in obvious different results. For the hydrological correction, the WaterGAP Global Hydrology Model (WGHM) model and the Global Land Data Assimilation System (GLDAS) model are used to estimate the mass change of the liquid part. In addition, the ice mass loss in the Alps between 2000 and 2014 based on glacier inventory was estimated in another publication, which can be a reference (-1.34 Gt/yr). Glaciers in the Alps lost mass at a rate of around -1.4 Gt/yr and around -2.2 Gt/yr depending on different ways of GIA correction during the 21-year period, which have similar magnitudes with the reference value.

How to cite: Liu, S. and Pail, R.: The estimation of glacier changes in the Alps in 2002-2022 with the use of satellite gravimetry data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11913, https://doi.org/10.5194/egusphere-egu24-11913, 2024.

15:00–15:10
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EGU24-21332
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ECS
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Highlight
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On-site presentation
Athul Kaitheri, Ines Otosaka, and Andrew Shepherd

Ice sheets in Antarctica and Greenland have continued to undergo rapid changes since the 1970s causing a significant rise in global mean sea level. The Ice Sheet Mass Balance Inter-comparison Exercise (IMBIE) community has produced reconciled estimates of ice sheet mass changes for both ice sheets from the 1970s till 2021 by combining more than 50 independent mass balance estimates produced from varied satellite observations. Ice sheet mass changes are driven by competing processes due to their interaction with the atmosphere (surface mass balance) and ocean (ice dynamics). Here, we present an updated IMBIE assessment and partition mass trends into their surface mass balance (SMB) and ice dynamics components. This new assessment shows that Antarctica and Greenland contributed 29.3 mm to the global mean sea level between 1979 and 2021. While in Antarctica, almost all ice losses were driven by ice dynamical imbalance, we find that 60 % of Greenland’s ice losses were caused by increased ice discharge with reduced SMB accounting for the remainder. This exercise reveals the different drivers of Antarctica and Greenland mass changes and highlights their high interannual variability. Finally, we are aiming at producing reconciled regional ice sheet mass balance estimates for the main drainage basins of Antarctica and Greenland for the first time and will be presenting preliminary results for some of the key regions of the ice sheets that have been undergoing rapid changes. Partitioning mass trends and producing regional assessments will contribute to a better understanding of the remaining differences between the different satellite geodesy techniques employed within IMBIE and will provide a key dataset for both the Earth Observation and ice sheet modelling communities. 

How to cite: Kaitheri, A., Otosaka, I., and Shepherd, A.: Mass Balance of Greenland and Antarctic Ice Sheets since the 1970s, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21332, https://doi.org/10.5194/egusphere-egu24-21332, 2024.

15:10–15:20
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EGU24-10483
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ECS
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On-site presentation
Marius Schlaak, Roland Pail, Alejandro Blazquez, Benoit Meyssignac, and Jean-Michel Lemoine

Ocean Heat Content (OHC) is an essential indicator of Earth’s climate state. Climate change is driven by the disequilibrium of Earth’s radiation budget. This abundant energy in the system is the Earth Energy Imbalance (EEI), which is challenging to measure globally. About 90% of EEI is accumulated in the oceans, resulting in an increase in ocean heat content. Therefore, OHC is a suitable proxy for EEI and can be measured globally using a combination of geodetic satellite techniques. By combining satellite altimetry and satellite gravimetry, it is possible to measure the change in global ocean heat content over the mission’s lifetime. While the altimeter record covers several decades, satellite gravity missions have been observing global mass transports for two decades. To steadily estimate the system’s long-term behavior, an extended observation period of the satellite systems is needed. The upcoming satellite gravity mission Grace-C, planned to be launched in 2028 by NASA, is meant to ensure continuity and extension of the data record. At the beginning of the 2030s, an additional inclined pair will be launched by ESA to form together with GRACE-C the Mass change And Geosciences International Constellation (MAGIC), for which higher spatial and temporal resolutions are expected.

This contribution presents the results of multi-decadal closed-loop simulations of current and future satellite gravity observations. It shows the benefit of an increased duration of the observation and an improved observational system while comparing processing strategies for long-term trends in ocean mass changes. The observed climate signal is based on projections of mass change signals of oceans, ice sheets, and glaciers derived from CMIP6 climate projection under a shared socio-economic pathway scenario without drastic reduction of Greenhouse gases emissions (SSP5-8.5). A particular focus here is on the accuracy of long-term ocean trends. The direct estimation of long-term trends benefits from an increasing observation period and allows improved spatial resolution compared to trends estimated from monthly temporal gravity fields. The global ocean heat content is estimated from the steric sea-level change which is derived by subtracting the observed ocean mass change from the overall sea level change. The resulting long-term trends in ocean heat content are then compared to initial inputs to the simulation to illustrate the difference in performance between current and future satellite gravity constellations.

How to cite: Schlaak, M., Pail, R., Blazquez, A., Meyssignac, B., and Lemoine, J.-M.: Resolving the interannual to multi-decadal variability in ocean heat content, a simulation study of current and future satellite gravity missions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10483, https://doi.org/10.5194/egusphere-egu24-10483, 2024.

15:20–15:30
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EGU24-16124
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ECS
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Virtual presentation
Juan Adrián Vargas Alemañy, Isabel Vigo Aguiar, David García García, and Ferdous Zid

Geostrophic currents, driven by the Coriolis and pressure gradient forces, are crucial for understanding ocean circulation. The Antarctic Circumpolar Current (ACC) in the Southern Ocean, encircling Antarctica, has substantial global impact, and its volume transport (VT) remains challenging to measure. We utilize satellite data, combining Altimetry and Gravity Satellite missions, to estimate VT within the ACC. Our study offers a comprehensive spatial and temporal analysis, encompassing barotropic and baroclinic VT components. We validate our results with in-situ measurements from the Drake Passage. Our analysis reveals a steady spatial VT of 210.44 ± 3.4 Sv, with maxima near critical choke points. Temporally, we identify a mean VT of 15.86 ± 0.05 Sv per 1º grid cell, a linear trend of -0.007 ± 0.002 Sv per month, and significant seasonal and biannual signals. Zonal VT predominantly influences total VT, while meridional VT remains near zero. The baroclinic component drives low-frequency variations, while the barotropic component controls high-frequency variations. We propose a specific ACC zonal VT of 201.63 ± 0.71 Sv. In summary, our satellite-based approach offers valuable insights into ACC VT. This methodological extension enhances our understanding of the ACC's ocean circulation dynamics, showcasing the utility and robustness of satellite data in oceanographic research.

How to cite: Vargas Alemañy, J. A., Vigo Aguiar, I., García García, D., and Zid, F.: ACC Volume Transport: A Geodetic Analysis via Satellite Data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16124, https://doi.org/10.5194/egusphere-egu24-16124, 2024.

15:30–15:40
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EGU24-15227
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On-site presentation
Olivier Bock, Ninh Khanh Nguyen, and Emilie Lebarbier

Water vapor plays a key role in the Earth's climate as a dominant greenhouse gas. It is also the most efficient actor of heat transfer from the surface to the atmosphere and from low to high latitudes which shapes the global atmospheric circulation and weather systems. Monitoring and understanding the spatial and temporal variability and changes of water vapor are thus of crucial importance.

This work aims at computing decadal trends of total column Integrated Water Vapour (IWV) from a global network of ground-based GNSS observations. Although GNSS observations are available with high accuracy in all weather conditions, it has been shown that, over long periods of time, changes in instrumentation, in station location and environment, and in processing methods can introduce spurious shifts in the IWV time series and bias trend estimates. Homogenization is a crucial step to detect and correct such non-climatic signals.

We have developed a relative homogenization method which involves three steps.

  • Segmentation. First, change-points are detected from the difference series (GNSS – reference) with the help of the GNSSseg segmentation package (Quarello et al., 2022). The method uses a difference series in order to cancel out the common climatic variations. It also accounts for changes in the variance on fixed intervals (monthly) and a periodic bias (annual) due to representativeness differences between GNSS and the reference (in our case the ERA5 reanalysis). Because the change-points detected in the difference series could be either due to GNSS or to the reference (ERA5), the next step is the attribution.
  • Attribution. Second, the detected change-points are attributed to either GNSS or to the reference (ERA5) using a statistical test based on linear regression and a predictive rule based on the Random Forest learning algorithm (Nguyen et al., 2023). This step requires additional neighbors stations (at least one).
  • Correction. The last step is the correction. Here the initial GNSS series is corrected only for the shifts which are attributed to the GNSS in the second step.

We will present results of the homogenization procedure applied to a global network of GNSS stations and discuss the impact of homogenization on linear trend estimates for stations that have more than 20 years of observations.

Quarello et al., 2022, https://doi.org/10.3390/rs14143379

Nguyen et al., 2023, https://hal-obspm.ccsd.cnrs.fr/IGN-ENSG/hal-04014145v1

How to cite: Bock, O., Nguyen, N. K., and Lebarbier, E.: Homogenization of GNSS IWV time series and estimation of climatic trends, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15227, https://doi.org/10.5194/egusphere-egu24-15227, 2024.

15:40–15:45
Coffee break
Chairpersons: Bramha Dutt Vishwakarma, Anna Klos, Vincent Humphrey
16:15–16:25
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EGU24-8938
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On-site presentation
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Anne Springer, Yorck Ewerdwalbesloh, Helena Gerdener, Kerstin Schulze, and Jürgen Kusche

After more than 15 years of experience with GRACE/-FO data assimilation (DA) into hydrological models, numerous studies have conducted various tests on GRACE product and preprocessing options as well as DA strategies. However, a commonly accepted standard procedure has yet to emerge. This contribution comprises (1) a review on the prevalence of GRACE-DA options based on existing studies together with (2) insights from applying two GRACE assimilating frameworks: the high-resolution CLM-DA framework over Europe and the global WGHM-based calibration and data assimilation framework.

We discuss the selection of different GRACE/-FO products for DA into hydrological models, including spherical harmonics, MASCONS, level 3 products, and the recently evolved along-orbit line-of-sight gravity differences. Additionally, we explore processing choices such as filtering and rescaling, possible corrections for phenomena like glacial isostatic adjustment, large lakes and reservoirs or earthquakes, observation grid representation, and various approaches to handle observation errors. We evaluate the impact of these processing strategies on simulated water storage trends and the representation of selected extreme events.

Through this research, we contribute to understanding optimal strategies in assimilating GRACE/-FO data, addressing critical aspects influencing hydrological model reliability.

How to cite: Springer, A., Ewerdwalbesloh, Y., Gerdener, H., Schulze, K., and Kusche, J.: Strategies for assimilating GRACE/-FO terrestrial water storage anomalies into hydrological models, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8938, https://doi.org/10.5194/egusphere-egu24-8938, 2024.

16:25–16:35
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EGU24-10526
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On-site presentation
Henryk Dobslaw, Laura Jensen, Robert Dill, and Kyriakos Balidakis

Simulated terrestrial water storage (TWS) data from global hydrological models are indispensable for various geodetic applications, e.g., for simulating Earth orientation parameters, deriving time series of deformations of the Earth’s surface needed for the realization of global reference systems, or de-aliasing purposes of GRACE/-FO gravity products. So far, the Land Surface Discharge Model (LSDM) has been routinely used for such tasks at the GFZ. However, the current standard experiment of LSDM is already several years old, and many limitations are known, in particular a limited spatial resolution of 0.5°, which limits the accuracy of crustal deformation predictions close to rivers and lakes. In this contribution, we evaluate the suitability of LISFLOOD (https://ec-jrc.github.io/lisflood/), an open source, high-resolution hydrological rainfall-runoff-routing model, for geodetic purposes.

We compare the performance of various global LISFLOOD model runs for the time period 2000 – 2022 against the current LSDM configuration. In addition to two LISFLOOD model generations, which differ in their spatial resolution (0.1° and 0.05°) and their input land surface parameter data set, we also explore a number of high-resolution (0.05°) model runs with respect to the influence of the soil depth on simulated TWS. Model results are validated against mass anomalies from the satellite gravimetry missions GRACE and GRACE-FO on different spatial and temporal scales. Furthermore, to demonstrate the benefit of the higher spatial resolution of LISFLOOD, we utilize data from selected ground based GNSS stations to validate the models’ performance regarding mass-induced loading.

We find that LISFLOOD significantly outperforms LSDM in many regions, especially on interannual time scales, in terms of various validation metrics (i.e., correlation, root mean squared deviation, and explained variance). Analyzing the different LISFLOOD runs reveals advantages of the new (0.05°) over the old (0.1°) model version, and a large impact of the choice of soil depth on simulated TWS.

How to cite: Dobslaw, H., Jensen, L., Dill, R., and Balidakis, K.: Assessment of global high-resolution water storage simulations from the LISFLOOD hydrological model, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10526, https://doi.org/10.5194/egusphere-egu24-10526, 2024.

16:35–16:45
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EGU24-7669
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ECS
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On-site presentation
Klara Middendorf, Annette Eicker, Laura Jensen, and Henryk Dobslaw

Under the assumption that a warming climate leads to an intensification of the global water cycle, it can be hypothesized that also the occurrence frequency and severity of extreme events such as droughts or floods will increase in the upcoming decades to centuries. Global coupled climate models, which project the future evolution of various variables of the Earth's climate system are important tools for the analysis of such expected changes. To assess the reliability of the models and to identify possible systematic discrepancies, it is essential to evaluate the model output against observations.

In this study, present and future occurrences of extreme events are analysed in water storage time series simulated by coupled global climate models participating in the Coupled Model Intercomparison Project Phase 6 (CMIP6) and compared against spatio-temporal changes in water mass derived from GRACE and GRACE-FO. This comparison is based on Extreme Value Theory, as the exact timing of modelled extreme events cannot be assessed by observations due to the stochastic behavior of climate variability in unconstrained model experiments. From estimated extreme value distributions return levels are calculated, a quantity describing the magnitude or frequency of extreme values.  Challenges that have to be overcome in the analysis are the non-stationary data and the relatively short time span of the GRACE observations. The latter issue is addressed by additionally assessing GRACE-based water storage reconstructions available over many decades.

This study provides insights into the ability of global climate models to model the occurrence of TWS extremes, namely unusual dry and wet phases. It also examines whether the climate model projections predict an increasing intensity of extreme events.

How to cite: Middendorf, K., Eicker, A., Jensen, L., and Dobslaw, H.: Evaluation of extreme events in global coupled climate models by satellite gravimetry, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7669, https://doi.org/10.5194/egusphere-egu24-7669, 2024.

16:45–16:55
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EGU24-8830
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Highlight
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On-site presentation
Eva Boergens, Josefine Wilms, Markus Hauk, Christoph Dahle, Henryk Dobslaw, and Frank Flechtner

NASA and DLR will launch in 2028 GRACE-C (Gravity Recovery and Climate Experiment – Continuation). This mission will again be launched into a polar orbit at 500 km initial altitude and extend the observation of the time-variable Earth’s gravity field from GRACE (2002-2017) and GRACE-FO (GRACE Follow-On, 2018-today). ESA plans to launch a Next Generation Gravity Mission (NGGM) in 2032, which shall fly in a lower and inclined orbit and be based on improved instrumentation. GRACE-C and NGGM will then form the double-pair Mass-Change and Geosciences International Constellation (MAGIC) to significantly increase the spatial and temporal resolution of mass transport products and deduce water mass redistribution over the oceans, ice sheets and continents.

Thanks to the 20+ years period of GRACE and GRACE-FO observations, scientists are able to analyse extreme hydrological events, such as flooding and droughts. However, due to the rather coarse spatial resolution of the GRACE and GRACE-FO data sets of approximately 350 km, finer spatial details of such extreme events are kept hidden. Further, spatial leakage limits the value of these data for smaller-scale regional investigations.

In this contribution, we will employ five years of simulated data for both a single polar pair (GRACE-FO-like) and a MAGIC baseline scenario. Thanks to the simulation, we can also assess the true values of the hydrological input models. Both simulated data sets are filtered with the same DDK filters for comparison. The filter strength can be reduced for the MAGIC baseline scenario without introducing more striping errors.

With these simulated data sets, we investigate extreme hydrological events. For example, the localisation of extreme wet events along the northern coast of Australia is much improved, with less signal leakage into the surrounding ocean.

How to cite: Boergens, E., Wilms, J., Hauk, M., Dahle, C., Dobslaw, H., and Flechtner, F.: Will the MAGIC mission improve the observability of extreme hydrological events?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8830, https://doi.org/10.5194/egusphere-egu24-8830, 2024.

16:55–17:05
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EGU24-7888
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ECS
|
On-site presentation
Daniel Blank, Annette Eicker, and Andreas Güntner

Changes in soil water storage can be studied on a global scale using a variety of satellite observations. With active or passive microwave remote sensing, we can study the upper few centimeters of the soil, while satellite gravimetry allows us to detect changes in the entire column of terrestrial water storage (TWS). The combination of both types of data can provide valuable insight into hydrological dynamics in different soil depths towards a better understanding of changes in subsurface water storage.

We use daily Gravity Recovery and Climate Experiment (GRACE) data and satellite soil moisture data to identify extreme hydroclimatic events, focusing on prolonged droughts. To enhance our comprehension of the subsurface, we utilize not just surface soil moisture data but also integrate information on root zone soil moisture. Original level-3 surface soil moisture data sets of SMAP and SMOS are compared to post-processed level-4 data products (both surface and root zone soil moisture) and a multi-satellite product provided by the ESA CCI.

We analyse the correspondence between high and low percentiles in TWS and soil moisture time series, which allows us to identify extreme events in different integration depths and storage compartments. Furthermore, we compute the rate of change of anomalies to assess how quickly the system accumulates storage deficits during drought conditions and recovers from them for different soil depths. Our investigation focuses on the temporal dynamics of near-surface soil moisture and TWS, highlighting the cascading effects that propagate from the surface into the subsurface. The results we obtained indicate characteristic patterns of the temporal dynamics of drought recovery in varying soil depths. Specifically, our analysis shows that surface soil moisture recovers faster than TWS, and that this recovery process slows down as soil integration depth increases.

How to cite: Blank, D., Eicker, A., and Güntner, A.: From surface to subsurface: Investigating drought cascades and recovery patterns with (daily) satellite observations of soil moisture and terrestrial water storage, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7888, https://doi.org/10.5194/egusphere-egu24-7888, 2024.

17:05–17:15
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EGU24-3658
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ECS
|
On-site presentation
Zachary M. Young, Hilary R. Martens, Zachary H. Hoylman, and W. Payton Gardner

During periods of drought, quantifying the intensity of water loss within hydrologic reservoirs, both on and below the surface, is critical to sustain water resources. Drought intensity is typically characterized using drought indices which are driven by meteorologic observations, such as precipitation. These drought indices provide good insight into the quantity of water entering the hydrologic system, however, they are unable to quantify the amount of water retained in a watershed or the amount lost due to runoff and evapotranspiration. We address this by leveraging the sensitivity of three-dimensional Global Positioning System displacements to local and regional hydrologic-storage fluctuations, and produce a new geodetic drought index (GDI), derived from estimated hydrologic-storage deviations, to directly characterize hydrologic storage anomalies. The GDI is derived comparably to the Standardized Precipitation Evapotranspiration Index such that it may be easily incorporated into current drought management workflows. We directly compare the GDI to hydrologic observations within California and find strong associations between specific time scales of the GDI and groundwater well, artificial-reservoir storage, and stream discharge observations. The GDI is most sensitive to groundwater, exhibiting a correlation coefficient of 0.87 at the 3-month time scale. Both artificial-reservoir storage and stream discharge exhibit peak correlation coefficients when considering the 1-month GDI, at 0.81 and 0.47 respectively. No relationship is observed with soil moisture observations. The correlation coefficients decline rapidly away from the optimal time scale, indicating the 1- and 3-month GDI are strong predictors of hydrologic variation within California. In addition to capturing long-term trends, rapid changes in the GDI initiate during clusters of large atmospheric-river events that closely mirror fluctuations in the hydrologic observations. The GDI provides an opportunity to improve hydrologic models for drought-management and to advance our understanding of the water cycle.

 

How to cite: Young, Z. M., Martens, H. R., Hoylman, Z. H., and Gardner, W. P.: A Geodetic Drought Index Driven by Hydrologic Loading Estimates Calculated from Three-Dimensional GPS Displacements  , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3658, https://doi.org/10.5194/egusphere-egu24-3658, 2024.

17:15–17:25
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EGU24-12650
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ECS
|
On-site presentation
Francesco Pintori and Enrico Serpelloni

Drought is one of the most complex recurring natural disasters, defined by a deficiency of precipitations that causes prolonged water scarcity. Failure to manage drought risk has the potential to have dire consequences for people, livelihoods, economy and ecosystems.
In northern Italy, particularly in the highly productive industrial area of the Po river basin, the 2021-2022 period culminated in the most severe drought of the last two centuries.
In order to evaluate the best policies to address the problems caused by water scarcity, it is crucial to measure and monitor variations in terrestrial water storage (TWS). For drought monitoring, in fact, changes or anomalies in TWS provide direct observations of total water availability, complementing model-based measures such as drought severity indices.
To estimate the quantities and spatial distribution of TWS loss, we analyze vertical ground displacement time-series data from Global Navigation Satellite System (GNSS) stations in the Po river basin.
We use a regularization model, based on L1-norm, to reconstruct the long-term temporal evolution of vertical ground displacement trends. Next, we performed a Principal Component Analysis (PCA) on GNSS time series to extract a spatially consistent signal in vertical ground displacements. The temporal evolution of the first principal component is well-correlated with trend changes of the Po river level and with the  SPEI-12 drought index, with stations moving upward during periods of river/index level decrease and vice versa, indicating that common long-term variations in vertical ground displacements are driven by the hydrology of the area.
The inversion of the displacements associated with the first principal component allows us to estimate variations in equivalent water height (EWH) and find that between January 2021 and August 2022, the GNSS stations underwent uplift, up to 7 mm, which corresponds to ~70 Gtons of water loss. The results are compared with the Global Land Data Assimilation System (GLDAS) model and the Gravity Recovery and Climate Experiment (GRACE) data: while the temporal evolution of the three products, when averaged over the study area, is similar, the spatial distributions are different. This is likely due to the fact that GLDAS only takes surface water into account, and GRACE has a too-coarse spatio-temporal resolution.
Our results show that multi-year changes in water storage can be effectively monitored both in terms of temporal evolution and spatial distribution using space geodetic measurements, such as GNSS. This approach eliminates the need to rely solely on large-scale models or satellite measurements, which cannot reach the spatial resolution required at the scale of river basins such as the Po.

How to cite: Pintori, F. and Serpelloni, E.: Drought‐Induced Vertical Displacements and Water Loss in the Po River Basin (Northern Italy) From GNSS Measurements, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12650, https://doi.org/10.5194/egusphere-egu24-12650, 2024.

17:25–17:35
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EGU24-327
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ECS
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On-site presentation
Adrian Nowak, Radosław Zajdel, Filip Gałdyn, and Krzysztof Sośnica

The distribution of atmospheric, hydrological, and oceanic mass loads on the lithosphere affects the deformation of the Earth's surface over time. Monitoring of the relative displacements of the dense global network of permanent Global Navigation Satellite System (GNSS) stations enables the direct measurement of these loads on a global scale. The application of inverse GNSS methods provides an independent tool to retrieve the time variable gravity (TVG) models of the Earth system and to support hydrogeodesy studies, including the monitoring of the water storage cycle or polar ice mass loss.

The goal of this study is to investigate the effectiveness of using inverse GNSS methods to provide independent C20 and C30 coefficients. These coefficients are essential for deriving highly accurate Gravity Recovery and Climate Experiment (GRACE)-based TVG models. In this study, surface mass variations of low-degree TVG coefficients are derived from the displacements of continuously tracking GNSS sites based on the 21 years (2000-2021) of the Center for Orbit Determination in Europe solutions of the 3rd data reprocessing campaign of the International GNSS Service in the framework of the preparation of the International Terrestrial Reference Frame 2020. The geometrical displacements of the GNSS stations calculated by inverse methods are compared with changes in the gravity field based on independent estimates obtained from the GRACE and GRACE Follow-On (GRACE-FO) satellite missions and the Satellite Laser Ranging (SLR).

As an alternative to the solutions provided by SLR, it is shown that the C20 and C30 coefficients can be derived based on GNSS station displacements. The challenge of the inverse GNSS approach is to properly choose the maximum degree of TVG expansion. Compared with the SLR-based solution, the most consistent GNSS estimate of the temporal gravity variation rate of the C20 coefficient (−1.73 ± 0.10 × 10−11/year) and annual variation (4.7 ± 0.6 × 10−11/43.9° ± 7.5°) was obtained by expansion of the spherical harmonics to degree and order of 8. The GNSS-based C30 series is superior to the SLR-based estimates before the launch of the Laser Relativity Satellite. From August 2016, when the C30 estimates are essential for correcting the GRACE solutions, the root mean square between GNSS and SLR solutions is 4.2 × 10−11. GNSS could potentially support GRACE/GRACE-FO solutions that face problems in deriving C20 and C30, which are fundamental to estimates of ice mass changes in the polar regions. Recovery of mass change in the Antarctic ice sheet from April 2002 to December 2020 based on the coefficients replaced by GNSS estimates results in a linear trend of −111 ± 3 Gt/year. In comparison, the trend for the SLR-based replacement from Technical Note 14 shows a trend of −114 ± 2 Gt/year.

How to cite: Nowak, A., Zajdel, R., Gałdyn, F., and Sośnica, K.: Using Inverse GNSS Methods for the Determination of C20 and C30 Gravity Field Coefficients for the Support of GRACE Solutions   , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-327, https://doi.org/10.5194/egusphere-egu24-327, 2024.

17:35–17:45
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EGU24-17367
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On-site presentation
Alexandre Couhert, Flavien Mercier, John Moyard, and Pierre Exertier

The ever-changing fluid mass (oceans, continental water, snow, atmosphere, …) redistributions on the Earth's surface give rise to a motion of the deformable terrestrial crust, that is its geometrical center-of-figure (CF), with respect to the center-of-mass (CM) of the Earth, about which satellites naturally orbit. This motion, called “geocenter motion”, is the largest scale variability of mass within the Earth system. Yet, non-tidal geocenter motion, which reflects major water and atmosphere mass transports occurring over large regions, is traditionally neglected.

However, new climate-driven precise monitoring of geocenter motion is needed. Indeed, satellite altimetry and gravimetry precise orbits connect sea level and global water budgets to the Earth’s center of mass. As such, the geocenter motion is now the leading error term in Regional Mean Sea Level and mass changes over polar ice sheets estimates. Reliable solutions of geocenter motion are thus crucial for assessing the current status of climate change and its future evolution (e.g., for the Earth’s Energy Imbalance).

Global Navigation Satellite Systems (GNSS) measurement models and derived products are currently aligned to the International Terrestrial Reference Frame (ITRF) origin (which is referenced to the crust), instead of CM. Looking at sub-daily cross-track perturbations estimated with the GNSS receivers on board the Jason-3 and Sentinel-6 MF altimetry satellites during their tandem phase (December 18, 2020 – April 7, 2022) revealed consistent diurnal oscillations with an impressive temporal resolution. These could only be related to the miscentering effect of the constellation solution around the Earth’ CM. In this paper, a parametric model is derived, representing the translation of the GNSS ground station networks with respect to the center of mass of the whole Earth system. This model is estimated with GNSS-based low Earth satellite precise orbits and unambiguously validated with independent altimetry satellite missions (e.g., Sentinel-3A, Sentinel-6 MF, Jason-3). It helps to clearly identify interannual variations in the geocenter motion, as short as a day long.

How to cite: Couhert, A., Mercier, F., Moyard, J., and Exertier, P.: Assessing daily to interannual geocenter motion variations from Low Earth Orbiters, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17367, https://doi.org/10.5194/egusphere-egu24-17367, 2024.

17:45–17:55
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EGU24-14655
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Virtual presentation
Donald Argus, Hilary Martens, Wiese David, Swarr Matthew, Borsa Adrian, Peidou Athina, Nicholas Lau, Dain Kim, Kevin Gaastra, Matthias Ellmer, Zachary Young, Ellen Knappe, Noah Molotch, Sarfaraz Alam, Felix Landerer, Payton Gardner, and Reager John

We are strengthening the application of GPS's capability to estimate change in total water using measurements of elastic displacements of Earth's surface; breaking down total water into its components such as snow, soil moisture, and groundwater; and integrating GRACE gravity data to infer change in total water in groundwater basins.

In California's Sierra Nevada, GPS each day tracks the dumping and dissipation of storm water.  In Water Year 2023, total water increased abruptly during each of two sequences of snow-dominated atmospheric rivers.  Subsurface water, which we take to be total water inferred from GPS minus snow water equivalent, to rise in early January at the time of the first AR sequence, remain constant from late Jan through March (with no increase during the second AR sequence), and rise from April to June as the snowpack melts.  Subsurface water increases in the Sierra Nevada by 0.6 m from Oct 2022 to Jun 2023, 45 per cent of cumulative precipitation of 1.4 m.  Such a big rise in subsurface water begins to rejuvenate the Sierra Nevada critical zone (Earth's living outer layer between the top of the trees and the bottom of groundwater) and to replenish subsurface water lost during the prior 3 years of drought from 2020 to 2022.

Change in total water in California's Central Valley can be determined neither by GRACE alone nor GPS alone.  There GPS records primarily Earth's poroelastic response, from which water change is difficult to infer.  GRACE cannot distinguish water change in Central Valley from water change in the Sierra Nevada without assuming a hydrology model.  We integrate GPS elastic displacements and GRACE gravity to estimate water change in the Central Valley.  In the rigorous inversion, GPS determines water change in the Sierra Nevada and Coast Ranges and the remaining water change from GRACE is placed in the Central Valley.  We find Central Valley groundwater increased by 0.75 m in the first nine months of Water Year 2023 (the biggest gain ever recorded), replenishing more groundwater than lost during the prior 3 years of drought.

How to cite: Argus, D., Martens, H., David, W., Matthew, S., Adrian, B., Athina, P., Lau, N., Kim, D., Gaastra, K., Ellmer, M., Young, Z., Knappe, E., Molotch, N., Alam, S., Landerer, F., Gardner, P., and John, R.: The Big Soak:  Change in Water in 2023 in North America's Pacific Mountain System , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14655, https://doi.org/10.5194/egusphere-egu24-14655, 2024.

17:55–18:00

Posters on site: Thu, 18 Apr, 16:15–18:00 | Hall X2

Display time: Thu, 18 Apr, 14:00–Thu, 18 Apr, 18:00
Chairpersons: Bramha Dutt Vishwakarma, Anna Klos, Benoit Meyssignac
X2.11
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EGU24-5267
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ECS
Carsten Bjerre Ludwigsen, Ole Baltazar Andersen, Christopher Watson, and Matt King

The total mass change of the Earth's land surface precisely offsets the combined changes in the atmosphere and oceans, resulting in a net-zero change for the entire system (land+ocean+atmosphere).

Closing the ocean mass budget is crucial for understanding current and future sea-level changes. Recent efforts to reconcile ocean mass observations from GRACE and GRACE-Follow On satellites (hereafter unitedly referred to as ‘GRACE’) with both steric-corrected altimetry and and land/ice to ocean estimates have revealed a discrepancy in the mass budget (Wang et al, 2022; Barnoud et al, 2022). This finding indicates a concerning misalignment in our global observation system or understanding of earth mass transport.

This study uses GRACE-independent estimates/models of land surface mass changes to validate 20 years of GRACE observations. By calculating the monthly Gravitational, Rotational, and Deformational (GRD) response to 20 years of land mass changes, we reconstruct the global, regional, and seasonal ocean mass changes observed by GRACE from 2003 to 2022.

Over the 20-year period, the ocean mass reconstruction aligns well with the GRACE observations. However, a significant deviation emerges after 2020, with the reconstruction showing a larger ocean mass change than GRACE. We demonstrate that this deviation is likely caused by an underestimation of Western Africa precipitation in the ERA5 reanalysis, commonly used by hydrological models to estimate changes in land water storage. Land mass observations from GRACE further confirmvthis underestimation and shows great alignment between models and observations when excluding sub-Saharan Africa.

Our results show a global agreement between GRACE and GRD-induced ocean mass changes, suggesting that the misalignment between GRACE and steric-corrected altimetry is likely due to errors in the ARGO observing system. A reported 'salinity-drift' is the primary source of error, and together with an error in the wet path delay originating from drift in the radiometer of the Jason-3 satellite explains most of the post-2016 difference between GRACE and steric-corrected altimetry is identified. The remaining differences likely originate from GIA and/or Argo-biases.

How to cite: Ludwigsen, C. B., Andersen, O. B., Watson, C., and King, M.: Reconciling ocean mass changes from 20 years of GRACE and GRACE Follow On observations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5267, https://doi.org/10.5194/egusphere-egu24-5267, 2024.

X2.12
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EGU24-8727
Anny Cazenave, Lancelot Leclercq, Fabien Leger, Florence Birol, Fernando Nino, Marcello Passaro, and Jean Francois Legeais

In the context of the ESA Climate Change Initiative (CCI) Coastal Sea Level project, a complete reprocessing (including retracking of the radar waveforms) of high resolution (20 Hz, i.e. 350 m) along-track altimetry data of the Jason-1, Jason-2 and Jason-3 missions since January 2002 was performed along the world coastal zones. Different versions have been provided so far. The latest release (SL_cci+ coastal altimeter sea level dataset, v2.3) is now available to users. It is an extension in time of the previous data set (v2.2) which covers the period January 2002 to June 2021. A new improved processing for the waveform retracking and computation of the coastal sea level anomalies was developed and a new editing procedure for the coastal sea level trend computation was implemented. This new data set shows spectacular reduction of the data noise compared to previous versions, both in terms of sea level anomaly time series and trends. As a consequence, compared to the previous versions we now obtain an important increase of the number of virtual coastal stations (i.e., the location of the first valid point along the satellite track, with about 1200 sites at an average distance from the coast of about 3 km, including more than 200 stations at less than 2 km from the coast). The coastal sea level anomalies and trends of the altimetry-based virtual stations have been validated with tide gauge data where possible. An example in the Mississippi Delta is presented.

How to cite: Cazenave, A., Leclercq, L., Leger, F., Birol, F., Nino, F., Passaro, M., and Legeais, J. F.: 20-year-long sea level changes along the world’s coastlines from satellite altimetry: a new data set of coastal virtual stations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8727, https://doi.org/10.5194/egusphere-egu24-8727, 2024.

X2.13
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EGU24-891
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ECS
Milaa Murshan, Balaji Devaraju, Nagarajan Balasubramanian, and Onkar Dikshit

Vertical Land Motion (VLM) estimation involves various methods such as Global Navigation Satellite Systems (GNSS), Very Long Baseline Interferometry (VLBI), Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS), and Satellite Laser Ranging (SLR). However, satellite altimetry presents an alternative approach for estimating VLM independently. This study compares altimetry-based VLM estimates with those obtained from Tide Gauge (TG) devices. The VLM is determined by calculating the difference between the linear trends of sea-level time series derived from altimetry-based data Instantaneous Sea Surface Height (ISSH) and TG data. Additionally, VLM can be estimated by comparing the linear trends of altimetry-based Sea Level Anomalies (SLA) and TG SLA time series.
 To estimate VLM, absolute ISSH measurements from satellite altimetry, unaffected by the Earth's crust, are contrasted with relative sea level measurements recorded by TG stations with respect to a fixed land point. By differentiating and aligning temporal pairs of TG and altimetry data, only the linear trend remains, representing the vertical displacement of the TG station relative to the reference surface. Removing satellite altimetry instrumentation drifts enables the extraction of VLM from the difference in linear trends. 
The VLM estimate obtained for the Hadera TG station, covering 1992-2016, shows a positive trend of 0.24 ± 0.07 mm/year. This finding aligns with GNSS-based VLM estimations at the same station, indicating land uplifting in the region. Consequently, the study suggests that there is no immediate concern about the rise of sea level. These findings enhance our understanding of regional geodetic processes and their implications for assessing sea level changes. By providing valuable information on VLM estimation, this research contributes to our knowledge of vertical displacement on land and its significance for future studies.

How to cite: Murshan, M., Devaraju, B., Balasubramanian, N., and Dikshit, O.: Vertical Land Motion Detection Using Satellite Altimetry Data at the Hadera Tide Gauge Station, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-891, https://doi.org/10.5194/egusphere-egu24-891, 2024.

X2.14
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EGU24-11213
Galina Dick, Florian Zus, Jens Wickert, Benjamin Männel, and Markus Ramatschi

Aside from main geodetic applications, the Global Navigation Satellite System (GNSS) is now an established observing system for atmospheric water vapour which is the most important greenhouse gas as it is responsible for around 60% of the natural greenhouse effect. Water vapour is under-sampled in the current climate-observing systems. Obtaining and exploiting more high-quality humidity observations is essential for climate research.

Established in 2006, the Global Climate Observing System (GCOS) Reference Upper-Air Network (GRUAN), is an international reference observing network of sites measuring essential climate variables above the Earth's surface. Currently, this network comprises more than 30 reference sites worldwide, designed to detect long-term trends of key climate variables such as temperature and humidity in the upper atmosphere. GRUAN observations are required to be of reference quality, with known biases removed and with an associated uncertainty value, based on thorough characterization of all sources of measurement.

A complementary small scale regional climate station network is the Austrian WegenerNet, which provides since 2007 measurements of hydrometeorological variables with very high spatial and temporal resolution. GNSS precipitable water vapour (GNSS-PWV) measurement has been included as a priority one measurement of the essential climate variable water vapour to both GRUAN and WegenerNet climate station networks.

GFZ contributes to climate research within GRUAN and WegenerNet with its expertise in processing of ground-based GNSS network data to generate precise PWV products. GFZ is responsible for the installation of GNSS hardware, data transfer, processing and archiving, derivation of GNSS-PWV data products according to GRUAN and WegenerNet requirements including PWV uncertainty estimation. GNSS-PWV products and results of selected validation studies will be presented.

How to cite: Dick, G., Zus, F., Wickert, J., Männel, B., and Ramatschi, M.: GNSS Precipitable Water Vapour for Climate Monitoring, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11213, https://doi.org/10.5194/egusphere-egu24-11213, 2024.

X2.15
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EGU24-11433
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ECS
Alicia Tafflet, Joelle Nicolas, Jean-Paul Boy, Jean-Michel Lemoine, Félix Perosanz, Frédéric Durand, Achraf Koulali, Lissa Gourillon, Agnès Baltzer, and Jérôme Verdun

The Svalbard archipelago in the Arctic is extremely sensitive to climate change. The resulting redistribution of mass, including recent and past ice melt, induces deformations of the Earth's surface and temporal variations in its gravity field, which can be detected by space geodesy. The cross-comparison of different techniques takes advantage of their complementary temporal and spatial resolutions, helping to distinguish between local, regional and global signals. We analyse more than 20 years of GNSS (Global Navigation Satellite System) satellite 3D positionning solutions at 17 permanent sites. The results are compared with deformations computed from time gravity field variations observed by the space gravimetry missions GRACE (Gravity Recovery and Climate Experiment) and GRACE Follow-On. The mean vertical motion is of about 9 mm/year and can reach 15 mm/year. We then compare these GNSS and GRACE datasets with Little Ice Age (LIA) and Global Isostatic Adjustment (GIA) models as well as with satellite altimetry observations from Cryosat-2 and IceSat-2. We infer the various contributions and quantify the impact of the current climate change on Svalbard. In addition to better estimate the acceleration of the current ice melting we apply an innovative seasonal adjustment method. The results are then discussed in relation to in situ observations.

How to cite: Tafflet, A., Nicolas, J., Boy, J.-P., Lemoine, J.-M., Perosanz, F., Durand, F., Koulali, A., Gourillon, L., Baltzer, A., and Verdun, J.: Solid Earth’s response to climate change in Svalbard monitored by space geodesy , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11433, https://doi.org/10.5194/egusphere-egu24-11433, 2024.

X2.16
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EGU24-385
Filip Gałdyn, Krzysztof Sośnica, and Radosław Zajdel

In recent two decades, monitoring of changes in the Earth’s gravity field has been carried out mainly by the Gravity Recovery And Climate Experiment (GRACE) and its successor GRACE Follow-On. However, before the GRACE era,  very little information is available on the temporal evolution of the Earth's gravity field prior to that date. Moreover, through these missions, we have many gaps between 2010 and 2019. Fortunately, GRACE and GRACE Follow-On are not the only missions that can be used to recover variations in the Earth's gravity field. For the recovery of the mass redistribution processes on a large scale, we may employ precise Satellite Laser Ranging (SLR) observations.

We propose a set of long-term, continuous solutions based on SLR data. In our solutions, we use observations from spherical geodetic satellites. The gravity field is expanded up to a degree and order 10 with a monthly resolution from 1/1995 to 10/2021. The main solution has been decomposed into solutions expanded to degree and order 4, 6, 8, and 10 and stacked, taking advantage of the stability of the low-degree expansion and the better resolution of the high-degree expansion. The results show the reduction of the correlations between obtained parameters, stabilization of the ice mass estimates in polar regions – in Greenland and Antarctica, and a reduction of the noise over oceans by a factor of four.

In the GRACE and GRACE Follow-On datasets, the replacement of the spherical harmonics C20 and C30 with SLR-derived data is necessitated by suboptimal quality resulting from thermal effects impacting satellites and accelerometer malfunctions. In both SLR and GRACE solutions, coefficients of the same order and parity exhibit strong correlations. Merely replacing two specific coefficients could introduce bias into the solution. Therefore, we propose a comprehensive approach, combining GRACE with SLR solutions up to a degree and order of 10x10. This strategy ensures a proper consideration of the sensitivity of each technique to gravity field coefficients. The combined solution exhibits reduced noise compared to standard GRACE COST-G solution and effectively address the distinct sensitivities of SLR and GRACE techniques to low-degree time-variable gravity field coefficients.

How to cite: Gałdyn, F., Sośnica, K., and Zajdel, R.: Long-term gravity field changes from SLR data and the combination with GRACE  for improving low-degree coefficients, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-385, https://doi.org/10.5194/egusphere-egu24-385, 2024.

X2.17
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EGU24-8961
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ECS
A GPS hydro-geodesy dataset for monitoring changes in terrestrial water storage during drought and flood periods in California: assessment, validation, and application
(withdrawn after no-show)
Xin Ding, Zhao Li, and Weiping Jiang
X2.18
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EGU24-11918
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ECS
|
Sedigheh Karimi, Amin Shakya, Roelof Rietbroek, Marloes Penning de Vries, and Christiaan van der Tol

Climate change and global warming can affect the water cycle, leading to increased hydrological extremes, such as droughts affecting the environment, agricultural activities, and human life and causing serious social and economic problems worldwide. Therefore, monitoring changes in the water cycle can be helpful for effective water resources management and provide a management plan for sharing with stakeholders, water managers, and local people.

This study focuses on terrestrial water storage changes (e.g., trends and seasonal shifts) that potentially indicate climate change patterns like droughts and large scale flooding events within watersheds across the Horn of Africa.

In this study, an inversion scheme is being developed to process level-2 data obtained from the Gravity Recovery and Climate Experiment (GRACE) and subsequent measurements from GRACE Follow-On (GRACE-FO) spanning the period from 2002 to 2023 considering the variance-covariance matrix (error matrix) of observations for estimating TWS variations monthly at basin scale. We expect that our inversion scheme will be independent of filters, and there will be no need for empirical rescaling factors to amplify the primary signal after filtering and damping effect. The TWS changes estimated from the developed inversion scheme will be compared with the TWS trends of basins that have been derived using the basin averaging standard approach and Mascon solutions TWS changes products. Additionally, the atmospheric reanalysis products will be used, along with hydrological model discharge estimates, to assess the accuracy of time derivatives of TWS changes.

How to cite: Karimi, S., Shakya, A., Rietbroek, R., Penning de Vries, M., and van der Tol, C.: Estimating terrestrial water storage trends by developing a joint inversion scheme using GRACE and GRACE-FO data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11918, https://doi.org/10.5194/egusphere-egu24-11918, 2024.

X2.19
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EGU24-10234
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ECS
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Barbara Jenny, Marcus Jepsen, Sebastian Bjerregaard Simonsen, René Forsberg, and Tim Enzlberger Jensen

GRACE and GRACE-FO have proven valuable for monitoring the health of ice sheets by showing seasonal mass changes along with the decadal trends of mass loss. Two years stand out in the Greenland ice sheet mass loss record with record melt: 2012 and 2019. On the West coast of Greenland, the ice mass fluctuations act on remarkably short time scales during these events, as evident at Ilulissat isbræ, which nearly doubled its ice speed in just one week. Here, we study if these sub-monthly ice mass change variations can be measured using GRACE-FO line-of-sight measurements.

It has been shown several times that using dynamic orbits and Laser Ranging Interferometer (LRI) data, one can calculate residual Line-of-sight gravity signals. This method was primarily used to study hydrological signals such as storm surges or heavy rainfall. In this study, we focus on ice mass changes in Greenland, and we compare these GRACE-FO measurements to the expectation based on the monthly gravity field and the signal from mass change based on IceSat2 data for 2019-2021.

How to cite: Jenny, B., Jepsen, M., Simonsen, S. B., Forsberg, R., and Jensen, T. E.: Sub-Monthly Mass Change Signal in Greenland from GRACE-FO Laser Interferometry Data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10234, https://doi.org/10.5194/egusphere-egu24-10234, 2024.

X2.20
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EGU24-15647
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ECS
Florent Cambier, José Darrozes, Muriel Llubes, Lucia Seoane, and Guillaume Ramillien

Prediction of the trends of ice mass loss in Greenland can help for understanding what occurred during the last 20 years and in the future. The Level-2 GRACE and GRACE-FO solutions provided by the official computing centres CSR and ITSG as well as the combined products of the COST-G project give access to the spatio-temporal variations of the ice mass balance of Greenland from 2002 to present. We first reduce the GRACE data from post-glacial rebound. We propose to analyse these solutions by applying Singular Value Decomposition (SVD) and Empirical Mode Decomposition (EMD) to extract the trend. This trend is then removed from the timeseries for the Fast Fourier Transform (FFT) and 1-D Continuous Wavelet Transform (CWT) analysis. CWT and FFT analysis enable to unravel the long-term trend of the ice loss ranging from 6-9 years, as well as the annual and semi-annual part. The period of 6 to 9 years shows some correlation with meteorological and climate indexes such as North Atlantic Oscillation (NAO). The spatial component of the first SVD mode indicates that the ice melting is the most important along the west and southeast coast at the rate of -30 to -40 Gt/yr. Globally, the trend is not linear, it consist of different phases of acceleration and deceleration with rates between -60 and -340 Gt/yr.

How to cite: Cambier, F., Darrozes, J., Llubes, M., Seoane, L., and Ramillien, G.: Spatio-temporal analysis of the ice mass changes over Greenland from GRACE and GRACE-FO., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15647, https://doi.org/10.5194/egusphere-egu24-15647, 2024.

X2.21
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EGU24-18031
Maik Thomas, Linus Shihora, and Henryk Dobslaw

Estimating oceanic transports of volume, heat, carbon, and freshwater is fundamental to understanding the ocean’s role in the evolving climate system. Unique in this context is the Atlantic Meridional Overturning Circulation (AMOC) that comprises a net northward transport of relatively warm water at depths of ≲1 km throughout the Atlantic basin, compensated at ≳1–5 km by a colder net southward return flow.
While in-situ measurements, such as the RAPID array at 26.5°N, are considered the 'gold standard' to monitore changes in the AMOC, measurements at many latitudes and the detection of e.g. basin-wide modes are non feasible.
However, variations in the overturning are to a good degree accompanied by associated changes in oceanic bottom pressure which opens up new avenues of AMOC monitoring through bottom pressure recorders or even through future satellite gravimetry measurements. 

Here, we investigate the connection between changes in the Atlantic overturning and associated variations in bottom pressure along the western continental shelf in a suite of ocean models. This includes high resolution simulations from a CMIP6 FESOM run by AWI, the regional VIKING20X model by GEOMAR. We investigate to what degree the transport variations can be inferred from bottom pressure signatures alone, limitations of the approach and especially how such signatures could be implemented into a future iteration of the ESA ESM. This would allow the inclusion the these transport-related OBP changes in dedicated simulation studies for future satellite gravimetry missions.

How to cite: Thomas, M., Shihora, L., and Dobslaw, H.: Inferring North Atlantic Deep Water Transports from Ocean Bottom Pressure at the Western Boundary, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18031, https://doi.org/10.5194/egusphere-egu24-18031, 2024.

X2.22
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EGU24-19833
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ECS
Quantifying the impact of wave dynamics, tidal influence, and bathymetric variations on the performance of Coastal Altimetry: a case study in the Indonesian seas
(withdrawn)
Zulfikar Adlan Nadzir, Luciana Fenoglio, and Jürgen Kusche
X2.23
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EGU24-16767
Valerie Ballu, Yann-Treden Tranchant, Denis Dausse, and Laurent Testut

The sudden 2018 volcanic eruption offshore Mayotte, in the western Indian Ocean, demonstrated, once again, the crucial need for means to monitor telluric activity occurring on the seafloor and threatening coastal zones. In the Mayotte case, on-land GNSS stations were of primary importance to detect the subsidence induced by the emptying of a deep magma chamber (Peltier et al. 2022), however they are not adequate to properly characterize and monitor the deformation created by further offshore or shallower processes.

Ocean bottom pressure (OBP) records can be used to monitor seafloor motion. However, detecting small or slow deformation is challenging due to instrumental drift and oceanic variations at different timescales. New Ambient-Zero-Ambient (A0A) pressure systems allow the estimation of the instrumental drift in situ by periodic venting from ocean pressures to a reference atmospheric pressure (Wilcock et al., 2021) and therefore allow access to the accurate monitoring of slow deformation. A A0A drift-controlled pressure gauge has been deployed since 2020 (four successive deployments) to monitor the seafloor vertical deformation on the flank of Mayotte island. The deployment site is located within a seismically active circular-shape zone, called the proximal cluster (Lavayssière et al., 2022). During the last deployment (2022-2023), an additional reference instrument was installed outside the proximal cluster, to allow for differential deformation analysis.

Beside volcanic activity monitoring, the objective of this study is to assess the performance of these new A0A pressure gauges and our ability to reduce the oceanic “noise” in corrected OBP records and characterize seafloor deformation in the Mayotte region. We investigate the use of numerical models, including available global ocean circulation reanalyses (OGCMs) and barotropic simulations, to account for the different oceanic processes contributing to the seafloor pressure variations and therefore limiting our ability to identify crustal deformation in the integrated pressure records.

We also use temperature and salinity profiles from repetitive glider transects to validate OGCMs in the region and quantify the contribution of unresolved fine-scale processes to OBP records. Our results provide valuable insights into the feasibility of using numerical modeling for improving the accuracy of OBP-based monitoring at different timescales, in the context of the Mayotte seismic crisis as well as for other seafloor deformation monitoring. Finally, we present a preliminary work on the combination of sparse regional altimetric data with the glider observations to compute a seafloor pressure series to be compared to the recorded data. Current altimetry spatio-temporal coverage is limited, however, newcoming SWOT observations are likely to provide new perspectives in seafloor geodesy.

Our results bring insights for future A0A deployments, especially in the perspective of the planned MARMOR seafloor cabled observatory offshore Mayotte.

How to cite: Ballu, V., Tranchant, Y.-T., Dausse, D., and Testut, L.: A seafloor deformation study using A-0-A pressure instruments and ocean models to contribute to the monitoring of the Mayotte volcanic crisis., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16767, https://doi.org/10.5194/egusphere-egu24-16767, 2024.

X2.24
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EGU24-14952
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ECS
Sukanta Malakar and Abhishek K. Rai

The Himalayan terrain epitomises continuing convergence and geodetic deformation caused by tectonic and non-tectonic factors. Climate change and induced secondary factors are some of the dominant non-tectonic forces. A small change in stress and pore-fluid pressure caused by precipitation and temperature fluctuations may trigger seismic activity in the vicinity of already critically stressed faults and fractures at local and regional scales. The increase in temperature has also resulted in the melting of mountain glaciers in the Himalayan region and the release of the glacial load, leading to post-glacial rebound and elastic deformation. This study investigates the correlation and causal relationship between climatic parameters and earthquakes in the Himalayas. Further, we study the hydrological loading effect (derived from the GRACE/GRACE-FO satellite) and correlate it with the seismic hazard map. The results show that temperature anomalies have a relatively strong influence (r ~0.36-0.54) on the occurrence of minor-magnitude earthquakes in the Eastern Himalayas. However, the North-western Himalayas show a moderately positive correlation with precipitation anomalies (r ~0.23-0.37). Furthermore, a positive correlation has been found between regional terrestrial water storage (TWS) influence and the seismic hazard, ranging from 0.04-0.45. The result shows higher positive correlation values in the post-monsoon period for the North-western and Eastern Himalayas, whereas the Central Seismic Gap and Eastern Nepal and Sikkim show a higher value for the pre-monsoon period.

How to cite: Malakar, S. and Rai, A. K.: Impact of Climate Change and Terrestrial Water Storage on the Himalayan Seismicity , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14952, https://doi.org/10.5194/egusphere-egu24-14952, 2024.

X2.25
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EGU24-5690
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ECS
A monthly and daily 0.25° groundwater storage dataset in the Yangtze River Basin by assimilating GRACE/GRACE-FO data into the W3RA hydrological model
(withdrawn after no-show)
Xuewen Wan, Nengfang Chao, and Wenjie Yin
X2.26
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EGU24-7127
Mick Filmer, Fardin Seifi, and Sten Claessens

The accuracy of global ocean tide models (OTMs) in shallow waters and along coasts impacts on their numerous applications. For example, the use of OTMs to provide tide corrections (‘de-tiding’) for satellite altimetry observations is required for, e.g., sea level studies and marine gravity field recovery. OTMs are also indispensable in the mitigation of striping errors in GRACE and GRACE-FO time-variable gravity field solutions. It therefore follows that OTM errors in coastal and shelf ocean may then introduce biases into the ‘corrected’ satellite altimetry and gravimetry observations with the potential to impact models using these data. The purpose of our study is to assess the accuracy of two high resolution assimilated OTMs (TPXO9v5, and FES2014b) using an updated set of >100 coastal and shelf tide gauges across the northern Australia and Papua New Guinea region. TPXO9v5 and FES2014b are used here because they have previously compared better than other tidal models in adjacent coastal and shelf areas. This study will also provide insight into the tides in this region which contain a mix of shallow and medium depth waters adjacent to the coast, in addition to land and island barriers that result in a complex tidal regime. This study takes advantage of the large number of short-term tide gauges situated on the coast or offshore islands in Northern Australia and Papua New Guinea. This set of tide gauges have observation periods of >30 days, with a number being more than 90 days long which allows the resolution of the major semidiurnal and diurnal tidal constituents. We use harmonic analysis to estimate tidal constants of major diurnal and semi-diurnal constituents from tide gauges then compare them with corresponding values from TPXO9v5 and FES2014b at the tide gauge location. This comparison identifies improvements and also limitations in these OTMs in this region, and their potential impact on tide corrections provided for satellite altimetry products that may propagate into coastal sea surface, and gravity at the coast. The results also provide additional insight into the local tidal patterns in this region, with particular interest in the Torres Strait and surrounding area.

How to cite: Filmer, M., Seifi, F., and Claessens, S.: Evaluation of ocean tide models in coastal ocean regions of northern Australia and Papua New Guinea using an updated set of short term tide gauges, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7127, https://doi.org/10.5194/egusphere-egu24-7127, 2024.

X2.27
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EGU24-7430
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ECS
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Viviana Wöhnke, Annette Eicker, Matthias Weigelt, Marvin Reich, and Andreas Güntner

Water mass changes at and below the surface of the Earth cause changes in the Earth’s gravity field which can be observed by at least three geodetic observation techniques: ground-based point measurements using terrestrial gravimeters, space-borne gravimetric satellite missions (GRACE and GRACE-FO) and geometrical deformations of the Earth’s crust observed by GNSS. Combining these techniques promises the opportunity to compute the most accurate (regional) water mass change time series with the highest possible spatial and temporal resolution, which is the goal of a joint project with the interdisciplinary DFG Collaborative Research Centre (SFB 1464) "TerraQ – Relativistic and Quantum-based Geodesy".

A method well suited for data combination of time-variable quantities is the Kalman filter algorithm, which sequentially updates water storage changes by combining a prediction step with observations from the next time step. As opposed to the standard way of describing gravity field variations by global spherical harmonics, we introduce space-localizing radial basis functions as a more suitable parameterisation of high-resolution regional water storage change. An estimation environment has been set up for the combination of GRACE/-FO satellite gravimetry with GNSS station displacements. The feasibility and stability of the approach is first demonstrated in a closed-loop simulation to test the setup and tune the algorithm. Subsequently, it is applied to real GRACE and GNSS observations to sequentially update the parameters of a regional gravity field model for Central Europe. The implementation was designed to flexibly include further observation techniques (e.g. terrestrial gravimetry) at a later stage. This presentation will outline the Kalman filter framework and regional parameterisation approach, and addresses challenges such as the relative weighting between the GRACE and GNSS data, and the appropriate choice of the Kalman filter process model and radial basis function parameterisation.

How to cite: Wöhnke, V., Eicker, A., Weigelt, M., Reich, M., and Güntner, A.: Regional modelling of water storage variations from combined GRACE/-FO and GNSS data in a Kalman filter framework, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7430, https://doi.org/10.5194/egusphere-egu24-7430, 2024.

X2.28
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EGU24-13313
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ECS
Kevin Gobron, Paul Rebischung, Roland Hohensinn, Janusz Bogusz, and Anna Klos

Quantifying the uncertainty associated with parameter estimates is crucial for a wide range of geophysical and climate applications. This is particularly important for interpreting the long-term trends of quantities of interest, such as ground displacement, sea level, and water storage (among others), estimated from geophysical time series. Unfortunately, our imperfect understanding of measurement error sources and of the intrinsic stochastic behavior of the quantities of interest often makes it difficult to realistically assess the uncertainty of long-term trend estimates. 

One pragmatic approach to obtaining realistic trend uncertainties is to model all the stochastic variations observed in the time series (that is, the “noise”) by stochastic processes, and then derive the trend uncertainty using the variance propagation law. In practice, such noise models often include unknown stochastic parameters controlling, e.g., the amplitudes or time correlations of the stochastic processes, which need to be estimated from the observations. Estimated stochastic parameters, however, come with uncertainty, just like any estimated quantity. And an uncertainty on the parameters of the noise model implies an uncertainty on the long-term trend uncertainty based on that noise model. In view of trend analysis from geophysical and climate time series data, the importance of considering such “uncertainty on the uncertainty” remains so far to be investigated.

In this study, we address this issue by assessing, using numerical simulation, how the uncertainty of stochastic models derived from sparse geophysical time series (a few hundred data points) translates into the uncertainty of long-term trend uncertainty estimates. We demonstrate that uncertainty in the time-correlation structure can result in significant uncertainty on trend uncertainty estimates. We then discuss the impact of such “uncertainty on the uncertainty” on the assessment of long-term trend significance from geodetic time series and provide recommendations on how to deal with the issue in practice.

How to cite: Gobron, K., Rebischung, P., Hohensinn, R., Bogusz, J., and Klos, A.: On the uncertainty of the uncertainty of long-term trends derived from geophysical and climate time series, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13313, https://doi.org/10.5194/egusphere-egu24-13313, 2024.

X2.29
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EGU24-10138
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ECS
Charlotte Hacker, Jürgen Kusche, Anno Löcher, and Fupeng Li

The Gravity Recovery And Climate Experiment (GRACE) and its follow-on mission, GRACE-FO, have observed global mass changes and transports, expressed as total water storage anomalies (TWSA), for over two decades. However, for climate change attribution and other applications, multi-decadal TWSA time series are required. This need has triggered several studies on reconstructing TWSA via regression approaches or machine learning techniques, with the help of predictor variables such as rainfall or sea surface temperature. Here, we combine such an approach, for the first time, with low-resolution information from geodetic satellite laser ranging (SLR). The reconstruction is formulated on a GRACE-derived empirical orthogonal functions (EOFs) basis and complemented with the Löcher and Kusche (2021) approach, in which global gravity fields are solved from SLR ranges in a GRACE EOF basis for the pre-GRACE time frame. Although our technique works globally, we focus mainly on European basins and reconstruct water storage anomalies from 1992 onward.

How to cite: Hacker, C., Kusche, J., Löcher, A., and Li, F.: Reconstructing GRACE-like TWSA maps from 1992 on by combining data-driven methods with time-variable gravity fields from SLR range analyses, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10138, https://doi.org/10.5194/egusphere-egu24-10138, 2024.

X2.30
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EGU24-18783
Ulrike Sylla, Pia Klinghammer, Antonia Cozacu, Frank Flechtner, Henryk Dobslaw, Julian Haas, Eva Boergens, Josef Zens, and Jörn Krupa

Dedicated satellite gravity missions orbiting the Earth at very low altitudes have greatly improved our knowledge about mass transport processes. That includes the terrestrial water cycle, ice sheet and glacier dynamics, ocean mass variability, and changes deep within the solid Earth, like the adjustment in the upper mantle in response to massive deglaciations since the last ice age. Initiated with the original GRACE (Gravity Recovery and Climate Experiment) mission launched in 2002, the record of monthly gravity fields now spans 22 years and is still being extended by GRACE-FO which has been in orbit since 2018. To enhance the visibility of the missions within society and to inform about the various contributions of GRACE/GRACE-FO to various scientific fields, GFZ  is maintaining a new knowledge portal accessible via www.globalwaterstorage.info.

On the one hand, this new portal provides overview information on satellite technology, various geophysical applications, and the numerous industrial and scientific partners who were vital for the success of the GRACE/GRACE-FO missions with the specific aim of informing European stakeholders. On the other hand, we also work towards developing the portal into a publicity channel for the gravimetry community to highlight recent developments towards future satellite missions or new research insights  based on mission data. International colleagues interested in advertising their latest achievements through a blog post (ca. 5000 characters) in the knowledge portal are kindly invited to contact globalwaterstorage@gfz-potsdam.de.

How to cite: Sylla, U., Klinghammer, P., Cozacu, A., Flechtner, F., Dobslaw, H., Haas, J., Boergens, E., Zens, J., and Krupa, J.: A New Knowledge Portal on Mass Transport Satellite Missions: www.globalwaterstorage.info, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18783, https://doi.org/10.5194/egusphere-egu24-18783, 2024.