B.5 | Multidisciplinary Science

B.5

Multidisciplinary Science
Orals
| Thu, 10 Oct, 15:00–16:30 (CEST)|Lecture Hall, Building H
Posters
| Attendance Wed, 09 Oct, 16:00–17:30 (CEST)|Foyer, Building H
Orals |
Thu, 15:00
Posters
Wed, 16:00
This session is open for science topics which do not properly fit into the other available sessions. Also, if you are unsure about the right session for your abstract, please submit it to this session.

Session assets

Session materials

Orals: Thu, 10 Oct | Lecture Hall, Building H

15:00–15:15
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GSTM2024-39
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On-site presentation
How well can we derive the time-variable gravity field before the GRACE mission based on SLR data? 
Filip Gałdyn, Krzysztof Sośnica, Radosław Zajdel, Ulrich Meyer, and Adrian Jäggi

The precise monitoring of the Earth's water cycle and the mass balance of glaciers and ice caps has become a cornerstone of contemporary geodesy, with satellite gravimetry playing a pivotal role in advancing our understanding of these processes. Before the GRACE era, the determination of monthly gravity field models relied on alternative methods, such as Satellite Laser Ranging (SLR) to passive spherical satellites. While early applications of SLR data were limited to assessing the Earth's oblateness, advancements in satellite constellations, observational techniques, orbit, and background models eventually enabled the derivation of gravity field models to a degree and order 10 of spherical harmonics based on SLR. However, these models still do not match the spatial resolution achieved with GRACE data. Nevertheless, the long-term gravity field models derived from SLR data are a fundamental information source of large-scale global changes in ice mass, ocean and land hydrology, especially for periods predating 2002.

This study addresses the challenge of limited high-resolution satellite gravimetry data available before the GRACE era by leveraging SLR data for large-scale changes and fitting GRACE data using an empirical function with stochastic parameters to enhance spatial resolution. By analyzing these combined datasets, we delimit global areas affected by significant accelerations in water storage and identify the dates for the maxima and minima of the function for the period from 1995 to 2024. We found that in the Svalbard region, ice mass accumulation reached its maximum in the middle of the first decade of the 21st century, followed by a significant acceleration of ice mass loss due to climate warming, which continues to the present day. Such a change in trend cannot be identified using solely GRACE data, therefore, the SLR+GRACE combinations are indispensable. A similar trend is observed in the Gulf of Alaska Glaciers, where ice mass loss has accelerated substantially since the beginning of the observations, particularly intensifying after 2012. In contrast, the Antarctic Peninsula saw a complete deceleration in ice mass loss, with the trend reversing around 2021. The results of our study show strong agreement with external validation datasets, including satellite altimetry and climate parameters such as Sea Surface Temperature Anomalies.

How to cite: Gałdyn, F., Sośnica, K., Zajdel, R., Meyer, U., and Jäggi, A.: How well can we derive the time-variable gravity field before the GRACE mission based on SLR data?, GRACE/GRACE-FO Science Team Meeting, Potsdam, Germany, 8–10 Oct 2024, GSTM2024-39, https://doi.org/10.5194/gstm2024-39, 2024.

15:15–15:30
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GSTM2024-62
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On-site presentation
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Potential links between internal and external geodynamics at periods around 6 years 
Julia Pfeffer, Anny Cazenave, Véronique Dehant, Mioara Mandea, Séverine Rosat, Nicolas Gillet, Dominique Jault, and Henri-Claude Nataf

The GRACEFUL project aims to better understand dynamic processes in the Earth’s deep interior using a combination of satellite observations of the Earth’s magnetic field, gravity field, and rotation. Significant oscillations at periods ranging from 6 to 8 years have been linked to dynamical processes in the fluid outer core and at the core-mantle boundary, influencing the three aforementioned observables. However, the occurrence of a 6-year cycle was also recently evidenced in the climate system, expressed in the global mean surface temperature, zonal winds, precipitation, terrestrial water storage changes, sea level changes, and ice mass changes. This study provides a comprehensive review of the 6-year cycle observed across the entire Earth system, from its deep interior to its fluid external envelopes. We propose several mechanisms that could explain small amplitude variations in geodetic observations, such as the length of day and gravity field, highlighting potential links between internal and external geodynamics at periods of around 6 years.

How to cite: Pfeffer, J., Cazenave, A., Dehant, V., Mandea, M., Rosat, S., Gillet, N., Jault, D., and Nataf, H.-C.: Potential links between internal and external geodynamics at periods around 6 years, GRACE/GRACE-FO Science Team Meeting, Potsdam, Germany, 8–10 Oct 2024, GSTM2024-62, https://doi.org/10.5194/gstm2024-62, 2024.

15:30–15:45
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GSTM2024-4
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On-site presentation
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Broadband assessment of polar motion excitation determined from recent gravity field solutions 
Justyna Śliwińska-Bronowicz, Jolanta Nastula, and Małgorzata Wińska

Variations in Earth's rotation, including polar motion (PM) and changes in the length of the day (LOD), are primarily caused by the varying distribution and movement of mass within the atmosphere, oceans, and hydrosphere. Identifying the different sources of these rotational changes is crucial for understanding processes occurring within the Earth system.

Large-scale mass variations are reflected in changes of spherical harmonic coefficients of geopotential. In the study of variations in Earth's rotation, coefficients of degree two and order one (ΔC21, ΔS21) are particularly important, as they are linearly related to the equatorial components (χ1, χ2) of PM excitation. ΔC21, ΔS21 coefficients can be measured using various techniques, with satellite gravimetry and Satellite Laser Ranging (SLR) being most popular in recent years. Various data centres around the world produce temporal gravity solutions based on data from Gravity Recovery and Climate Experiment (GRACE) and its successor GRACE Follow-On (GRACE-FO). There are currently many solutions available determined from either GRACE/GRACE-FO data alone or their combinations with various techniques such as SLR or satellite-to-satellite tracking.

In this study, we reassess the mass-related excitation of PM computed from various ΔC21 and ΔS21 solutions based on GRACE/GRACE-FO, SLR, and combinations of these techniques. We also provide a combined series of PM excitation achieved by minimizing noise in the input data. All series are analysed for various oscillations, including seasonal, non-seasonal long-term, and non-seasonal short-term variations. They are then evaluated by comparison with geodetic angular momentum obtained from precise geodetic measurements of Earth’s rotation. We show that combining various series of ΔC21 and ΔS21-derived PM excitation enhances its consistency with the observed PM excitation for the studied oscillations.

How to cite: Śliwińska-Bronowicz, J., Nastula, J., and Wińska, M.: Broadband assessment of polar motion excitation determined from recent gravity field solutions, GRACE/GRACE-FO Science Team Meeting, Potsdam, Germany, 8–10 Oct 2024, GSTM2024-4, https://doi.org/10.5194/gstm2024-4, 2024.

15:45–16:00
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GSTM2024-25
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On-site presentation
Global water cycle ‘events’ and global mass redistribution at interannual to decadal time-scales 
John T. Reager

Global mean sea level (GMSL) exhibits an average secular increasing trend of 3.1 +/- 0.3 mm yr-1 over the last 30 years [NOAA, 2023]. However, more than 43% of the variability in the de-trended global satellite sea level record occurs on 2-3 year time scales in rapid global water cycle ‘events’, during which GMSL can rise or fall at more than twice the ambient secular rate, causing changes as large as 12 mm over a relatively short period. This means that rapid changes in the natural movement of water from the oceans to the land, which appear on the continents as strong mass-change hydrologic signals, can be of sufficient amplitude to offset (i.e. equal and opposite) the mass additions to the oceans from the ice sheets over 2-3 year periods, or to offset those contributions by as much as 50% over a decade. In this talk, we examine the long GRACE/GFO record of global mass budget closure to better characterize the history of these global water cycle events, describe their apparent nature, and quantify their future potential impact on apparent GMSL.

How to cite: Reager, J. T.: Global water cycle ‘events’ and global mass redistribution at interannual to decadal time-scales, GRACE/GRACE-FO Science Team Meeting, Potsdam, Germany, 8–10 Oct 2024, GSTM2024-25, https://doi.org/10.5194/gstm2024-25, 2024.

16:00–16:15
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GSTM2024-51
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On-site presentation
Aliasing of atmospheric cloud water in time-variable gravity models from GRACE/-FO and next generation gravity missions? 
Christian Mielke, Anne Springer, and Jürgen Kusche

Temporal aliasing of high-frequency mass variations poses, along with instrument noise, the biggest obstacle to improving the accuracy and resolution of satellite gravimetry products from the GRACE/-FO mission and next-generation gravity missions (NGGM). The current GRACE/-FO data processing strategy includes the removal of tidal and sub-monthly non-tidal mass variations in ocean and atmosphere from the level-1 data using Atmospheric Ocean Dealiasing (AOD) data sets. However, the atmospheric part, based on ERA5 reanalysis and ECMWF operational forecast data, considers only dry air and water vapor, neglecting the mass contribution of liquid and solid cloud water. According to ERA5 data, the total global mass of cloud water is about 0.5% of the atmospheric water vapor mass, which may seem insignificant. However, we found that highly localized mass variations of cloud water can exceed 1Gt during extreme convective weather events, and thus may significantly affect laser ranging interferometer (LRI) measurements of GRACE-FO and NGGM.

In this study, we examine the overlooked cloud water content during hydrometeorological extremes in current AOD products over the entire GRACE/-FO observation time span from 2002 to 2023. By employing a 3D connected component algorithm to quantify the duration, intensity, and affected area of these events using ERA5 cloud water data, we identified over 1,000 events annually that we expect to impact GRACE-FO’s LRI measurements. We also observe that while the duration of these events has decreased over time, their intensity has increased. Most concerning, our findings show that the number of events has doubled over the observation period from 2002 to 2023, which is evident across all continents and the ocean, aligning with what we expect due to rising temperatures and increased atmospheric water-holding capacity. Notably, cloud modeling remains one of the most significant challenges in atmospheric and climate science, as it spans the complexities of microphysics to the dynamics of the global Earth system, and therefore may not meet geodetic accuracy requirements. However, with new and more precise NGGM on the horizon, our findings suggest a growing need to reevaluate AOD strategies that were developed prior to GRACE launch.

This study is part of the research unit New Refined Observations of Climate Change from Spaceborne Gravity Missions (NEROGRAV), funded by the German Research Foundation (DFG) with the objective of improving GRACE/-FO and NGGM data processing strategies.

How to cite: Mielke, C., Springer, A., and Kusche, J.: Aliasing of atmospheric cloud water in time-variable gravity models from GRACE/-FO and next generation gravity missions?, GRACE/GRACE-FO Science Team Meeting, Potsdam, Germany, 8–10 Oct 2024, GSTM2024-51, https://doi.org/10.5194/gstm2024-51, 2024.

16:15–16:30
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GSTM2024-76
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On-site presentation
Benefit of multi-pair quantum satellite gravity missions in Earth science applications 
Juergen Kusche and the QSG4EMT Team

Data from the GRACE and GRACE-FO missions have contributed significantly to our understanding of the Earth system. However, the spatial and temporal resolution, latency, and data quality being heterogeneous over time, render key scientific and operational applications difficult. Simulations indicate that all this will significantly improve with the MAGIC (i.e. GRACE-C and NGGM) mission concept, with even further improvements expected from future multiple-pair missions with novel quantum sensors. 
In this contribution, we assess the potential of multi-pair quantum mission formations as were investigated in ESA’s QSG4EMT study for three areas of application (1) water cycle research, (2) ocean mass change and regional sea level budget, and (3) Earthquake and submarine volcano observation. We explicitly include simulation experiment that involve assimilation of future data products into models, as well as the fusion with other (radar altimetric) data sets.

How to cite: Kusche, J. and the QSG4EMT Team: Benefit of multi-pair quantum satellite gravity missions in Earth science applications, GRACE/GRACE-FO Science Team Meeting, Potsdam, Germany, 8–10 Oct 2024, GSTM2024-76, https://doi.org/10.5194/gstm2024-76, 2024.

Coffee break / end of meeting

Posters: Wed, 9 Oct, 16:00–17:30 | Foyer, Building H

P18
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GSTM2024-13
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Calibration and Characterisation of GRACE-FO Magnetometers 
Ingo Michaelis, Kevin Marcel Styp-Rekowski, Jan Rauberg, Martin Rother, Guram Kervalishvili, and Monika Korte

Magnetic field data from satellite missions play a significant role in characterizing and understanding space weather conditions. Satellite magnetic field observations from different altitudes and local times are necessary to disentangle the complex processes contributing to each observation of Earth’s magnetic field and study the various individual processes. While the dedicated magnetic field satellite missions give good global data coverage at first sight, the coverage is still sparse if simultaneous observations from several different altitudes and with a good local time coverage are desired. Moreover, gaps between dedicated magnetic field satellite missions, such as between the CHAMP and Swarm missions from 2010 to 2013, exist and might occur again in the future. Many satellites non-dedicated for magnetic field measurements, e.g. GRACE-FO, carry so-called platform magnetometers (PlatMags) that are part of the attitude and orbit control system (AOCS). These satellites have a variety of mission goals and the PlatMags are additional instrumentation for navigational use.

Using analytical and machine learning tools and additional satellite telemetry data we can remove artificial disturbances from the satellite magnetometers and calibrate PlagMags for scientific use.

How to cite: Michaelis, I., Styp-Rekowski, K. M., Rauberg, J., Rother, M., Kervalishvili, G., and Korte, M.: Calibration and Characterisation of GRACE-FO Magnetometers, GRACE/GRACE-FO Science Team Meeting, Potsdam, Germany, 8–10 Oct 2024, GSTM2024-13, https://doi.org/10.5194/gstm2024-13, 2024.

P19
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GSTM2024-26
Influence of Laterally Heterogeneous Mantle Viscosity Structure on the Signal of Glacial Isostatic Adjustment in GRACE 
Erin Hightower, Lambert Caron, Felix Landerer, Eric Larour, and Michael Watkins

Geodetic data is essential to understanding interactions between the solid-Earth, ice sheets, and ocean and for accurately measuring ice mass loss and sea level rise. Glacial isostatic adjustment (GIA) – the viscoelastic response of the solid-Earth to changes in ice sheets and sea level – has a strong signal in geodetic datasets, particularly the Earth’s gravity field. Traditional GIA models assume a 1D radial mantle viscosity structure that is often inconsistent with 3D viscosity fields estimated from seismic tomography. However, laterally heterogeneous viscosity affects both the magnitude and spatial pattern of GIA and hence the correction applied for the level-3 GRACE(-FO) data. We quantify the degree to which such variations change the GIA response by systematically increasing lateral heterogeneity away from a 1D model. We model GIA using the spherical finite-element surface loading code CitcomSVE to predict vertical land motion, geoid rates, and equivalent water height (EWH). 3D viscosity structure is derived from seismic tomography and parameterized by an activation parameter that controls the temperature dependence of the viscosity and hence the strength of the lateral variations, which can vary by more than six orders of magnitude. Using a suite of viscosity models and GIA solutions, we assess the biases that arise when using GIA models that neglect 3D viscosity and illustrate the changes in the ocean mass trend that arise from incorporating stronger variations. Compared to models with 3D viscosity, the 1D model currently employed for GRACE(-FO) corrections tends to underestimate uplift rates and EWH changes in the formerly glaciated regions of North America. Differences between 1D and 3D GIA solutions are also pronounced throughout the North Atlantic, where increasingly strong lateral heterogeneity increases the rate of geoid change at present day due to GIA. Such differences may have implications for the interpretation of AMOC trends from the long-term GRACE(-FO) record. From the significant differences in the GIA solutions, particularly at the local and regional level, we propose that 3D viscosity should not be ignored in GIA solutions used for GRACE(-FO). Accurately accounting for GIA in such datasets is essential to estimates of surface water mass balance and projections of sea level rise. Future work will address the optimization and uncertainty quantification of the 3D viscosity structure used in such models.

How to cite: Hightower, E., Caron, L., Landerer, F., Larour, E., and Watkins, M.: Influence of Laterally Heterogeneous Mantle Viscosity Structure on the Signal of Glacial Isostatic Adjustment in GRACE, GRACE/GRACE-FO Science Team Meeting, Potsdam, Germany, 8–10 Oct 2024, GSTM2024-26, https://doi.org/10.5194/gstm2024-26, 2024.

P20
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GSTM2024-28
Supporting GRACE/GRACE-FO gravity field products with GNSS-derived data for improved Earth system monitoring 
Adrian Nowak, Filip Gałdyn, Radosław Zajdel, and Krzysztof Sośnica

GNSS-based low-degree spherical harmonic coefficients are an independent source of information for describing mass changes in the Earth system. In this study, we employ the mass load theory by an inverse GNSS approach to determine the changes in the Earth's gravity field with the spherical harmonic expansion up to degree and order 8, using daily station coordinate estimates from the third data reprocessing campaign of the International GNSS Service. Deriving a reliable series of variations in the Earth's dynamic oblateness terms (C20) and C30 is essential for supporting GRACE-based time-variable gravity field models. Consequently, our study focused on the comprehensive alternative and validation tool for the widely used Satellite Laser Ranging (SLR) series of C20 and C30 coefficients.

The global mean sea level has risen significantly since the 1990s, largely due to mass loss from the Greenland and Antarctic ice sheets. This underscores the importance of continued monitoring of the global changes. Therefore, we conduct a detailed analysis of the impact of incorporating GNSS-derived coefficients into the official gravity field products provided by the GRACE and GRACE-FO missions on changes in the ice sheets of these regions. The findings highlight the benefits of the GNSS-GRACE integration as a crucial element in enhancing gravity models and improving the representation of mass changes within the Earth system. The combination of GRACE/GRACE-FO with the GNSS results in a linear trend in Antarctic ice sheets with a rate of -152 Gt/year between January 2007 and December 2020.

Furthermore, we transform GNSS-based gravity field solutions into equivalent water heights and estimate annual terrestrial water storage (TWS) fluctuations in regions that are crucial for understanding large-scale hydrological dynamics, e.g., the Amazon and Brahmaputra river basins. Our solution is validated with GRACE/GRACE-FO data and global hydrological models, i.e., the Land Surface Discharge Model. The results show that the spatial and seasonal patterns of TWS changes derived from GNSS are consistent with GRACE/GRACE-FO and hydrological model estimates at the single-millimeter level within the range of the GNSS-based TVG model spherical harmonic expansion up to degree and order 5.

How to cite: Nowak, A., Gałdyn, F., Zajdel, R., and Sośnica, K.: Supporting GRACE/GRACE-FO gravity field products with GNSS-derived data for improved Earth system monitoring, GRACE/GRACE-FO Science Team Meeting, Potsdam, Germany, 8–10 Oct 2024, GSTM2024-28, https://doi.org/10.5194/gstm2024-28, 2024.