Lantmäteriet

The glacial isostatic adjustment (GIA) and sea level modeling communities have historically lagged other fields in adhering to the FAIR principles of making model outputs findable, accessible, interoperable, and reusable – a delay that has slowed scientific discovery. While sharing model outputs has improved recently, usability of available outputs continues to be hindered by lack of standardization. Meanwhile, legacy model outputs can be lost as the technology storing them grows obsolete and their creators retire or leave academia.The GIAmachine initiative addresses this problem. GIAmachine aims to make accessible as many published GIA and sea level model outputs as are retrievable bycataloguing and standardizing published GIA and sea level model outputs; contacting authors of published-but-inaccessible models to encourage them to upload their outputs to DOI-minting repositories;partnering with the GHub science gateway to make a long-term home for these newly available outputs;building Jupyter notebooks on GHub that make these models interoperable and easy to use; and encouraging the GIA and sea level modeling communities to follow the FAIR principles. Our poster will introduce the GIAmachine online portal and outline outstanding challenges. We appreciate community input for designing a living resource that meets the specific needs of current and future scientists.

Abstract. We used eight co-located global navigation satellite system (GNSS) stations with different antenna mounts to estimate atmospheric signal propagation delays in the zenith direction and linear horizontal gradients. The gradients are compared with the results from a water vapour radiometer (WVR). The water drops in the atmosphere have a negative influence on the retrieval accuracy of the WVR. Hence, we see better agreement using WVR data with a liquid water content (LWC) less than 0.05 mm compared to when LWC values of up to 0.7 mm are included. We used two different constraints when estimating the linear gradients from the GNSS data. Using a weak constraint enhances the GNSS estimates to track large gradients of short duration at the cost of increased formal errors. To mitigate random noise in the GNSS gradients, we adopted a fusion approach, averaging estimates from the GNSS stations. This resulted in significant improvements for the agreement with the WVR data, a maximum of 17 % increase in the correlation, and a 14 % reduction in the root mean square (RMS) difference for the east gradients. The corresponding values for the north gradients are both 25 %. Overall, no large differences in terms of quality are observed for the eight GNSS stations. However, one station shows slightly poorer agreement for the north gradients compared to the others. This is attributed to the station's proximity to a radio telescope, which causes data loss of observations at low-elevation angles in the south-south-west direction.

Land surface water is a key part in the global ecosystem balance and hydrological cycle. Remote sensing has become an effective tool for its spatio-temporal monitoring. However, remote sensing results exemplified in so-called water indices are subject to several limitations. This paper proposes a new and effective water index called the Sentinel Multi-Band Water Index (SMBWI) to extract water bodies in complex environments from Sentinel-2 satellite imagery. Individual tests explore the effectiveness of the SMBWI in eliminating interference of various special interfering cover features. The Iterative Self-Organizing Data Analysis Technique Algorithm (ISODATA) method and confusion matrix along with the derived accuracy evaluation indicators are used to provide a threshold reference when extracting water bodies and evaluate the accuracy of the water body extraction results, respectively. The SMBWI and eight other commonly used water indices are qualitatively and quantitatively compared through vision and accuracy evaluation indicators, respectively. Here, the SMBWI is proven to be the most effective at suppressing interference of buildings and their shadows, cultivated lands, vegetation, clouds and their shadows, alpine terrain with bare ground and glaciers when extracting water bodies. The overall accuracy in all tests was consistently greater than 96.5%. The SMBWI is proven to have a high ability to identify mixed pixels of water and non-water, with the lowest total error among nine water indices. Most notably, better results are obtained when extracting water bodies under interfering environments of cover features. Therefore, we propose that our novel and robust water index, the SMBWI, is ready to be used for mapping land surface water with high accuracy.

Abstract Coordinates in global reference frames are becoming more and more common in positioning whereas most of the geospatial data are stored in registries in national reference frames. It is therefore essential to know the relation between global and national coordinates, i.e., the transformation, as accurately as possible. Officially provided pan-European transformations do not account for the special conditions in the Nordic and Baltic countries, namely crustal deformations caused by Glacial Isostatic Adjustment. Therefore, they do not fulfill the demands for the most accurate applications like long-term reference frame maintenance. Consequently, the Nordic Geodetic Commission (NKG) has developed customized and accurate transformations from the global ITRF to the national ETRS89 realizations for the Nordic and Baltic countries. We present the latest update, called the NKG2020 transformation, with several improvements and uncertainty estimates. We also discuss its significance and practical implementation for geodetic and geospatial communities.

A sedimentological, geochronological, and geodynamic investigation of detailed micro- and meso-scale soft-sediment deformation structures (SSDS) within internally deformed layers on Gnitz Peninsula, Usedom Island, Germany, was performed in the last years. Five layers with SSDS were described of which four were possibly caused by glacial isostatic adjustment (GIA)-triggered earthquakes mirrored in liquefaction and reliquefaction phenomena (Pisarska-Jamroży et al., 2022). Hence, in line with earlier investigations and suggestions by Hoffmann and Reicherter (2012), the SSDS generation is related to oscillation of the Scandinavian Ice Sheet whose loading cycle caused stress changes likely releasing local earthquakes along pre-existing faults.Optically stimulated luminescence dating indicates a most probable time span of corresponding earthquake occurrence between 23.2 and 14.6 ka (including uncertainty). For the first time, glacially induced Coulomb failure stress changes were modelled for this area with a set of commonly accepted GIA models. They strongly support the interpretation of SSDS trapped in layers as seismites during that time. Using reliable fault parameters of faults in near vicinity of Gnitz Peninsula and suggested stress regimes and directions for northern Germany, the modelling can help indicate the most probable reactivated pre-Quaternary fault(s). If they can be confirmed after detailed palaeoseismological, geomorphological, geophysical, and structural investigations as so-called glacially induced fault(s), this would add another puzzle piece to a geodynamic scenario of glacially triggered faulting having affected an area from northern central Europe to northern Fennoscandia in the Late Pleistocene and Early Holocene.Our presentation will focus on the geodynamic setting of NE Germany, how it was changed during the last glaciation and how potentially reactivated faults can be determined.ReferencesHoffmann, G., Reicherter, K., 2012. Soft-sediment deformation of late Pleistocene sediments along the southwestern coast of the Baltic Sea (NE Germany). Int. J. Earth Sci. 101, 351-363, doi:10.1007/s00531-010-0633-z.Pisarska-Jamroży, M., Belzyt, S., Börner, A., Hoffmann, G., Kenzler, M., Rother, H., Steffen, R., Steffen, H., 2022. Late Pleistocene earthquakes imprinted on glaciolacustrine sediments at Gnitz Peninsula (Usedom Island, NE Germany). Quat. Sci. Rev. 296C, 107807, doi:10.1016/j.quascirev.2022.107807.

Intra-plate faults are a special challenge in seismology, because of the long intervals between individual seismic events and the fact that such faults are often hidden below young sediments. This makes such faults difficult to detect and thus they can be the source of unexpected and fatal earthquakes. The Børglum fault is located in a slowly deforming area in northern Denmark and represents one of the northern boundary faults of the Sorgenfrei-Tornquist Zone. With a length of at least 250 km, it is capable to produce significant seismic events. Previous studies indicated that the Børglum fault is seismically active and this fuelled the demand for further analysis of the fault structure and its seismic hazard potential. Due to excellent coastal outcrops and available high-resolution DEMs, the Børglum fault is a perfect natural laboratory to analyse a hidden active fault. We present a multi-method approach based on outcrop analyses, shear-wave seismic reflection surveys, DEM analysis and numerical simulations of deglaciation-induced Coulomb failure stress change. The 2D seismic surveys show that the analysed segment of the Børglum fault is a complex fault system with a strike-slip component. This interpretation is based on positive flower structures on the seismic surveys, the presence of elongated mini-basins and the geometry of the drainage pattern in the study area. On the basis of soft-sediment deformation structures and disaggregation bands developed in Late Pleniglacial to Lateglacial marine and lacustrine deposits, we derive repeated phases of fault activity with earthquake magnitudes of up to M=7. The geometry of the drainage pattern in the study area indicates a close relationship between fault activity and topography. Based on the timing of fault activity and results from numerical simulations of deglaciation-related lithospheric stress build-up, it is likely that the Børglum fault is a glacially triggered fault and that the analysed part of the Sorgenfrei-Tornquist Zone is susceptible to glacially triggered fault reactivation.

Abstract The redistribution of past and present ice and ocean loading on Earth's surface causes solid Earth deformation and geoid changes, known as glacial isostatic adjustment. The deformation is controlled by elastic and viscous material parameters, which are inhomogeneous in the Earth. We present a new viscoelastic solid Earth deformation model in ASPECT (Advanced Solver for Problems in Earth's ConvecTion): a modern, massively parallel, open‐source finite element code originally designed to simulate convection in the Earth's mantle. We show the performance of solid Earth deformation in ASPECT and compare solutions to TABOO, a semianalytical code, and Abaqus, a commercial finite element code. The maximum deformation and deformation rates using ASPECT agree within 2.6% for the average percentage difference with TABOO and Abaqus on glacial cycle (∼100 kyr) and contemporary ice melt (∼100 years) timescales. This gives confidence in the performance of our new solid Earth deformation model. We also demonstrate the computational efficiency of using adaptively refined meshes, which is a great advantage for solid Earth deformation modeling. Furthermore, we demonstrate the model performance in the presence of lateral viscosity variations in the upper mantle and report on parallel scalability of the code. This benchmarked code can now be used to investigate regional solid Earth deformation rates from ice age and contemporary ice melt. This is especially interesting for low‐viscosity regions in the upper mantle beneath Antarctica and Greenland, where it is not fully understood how ice age and contemporary ice melting contribute to geodetic measurements of solid Earth deformation.

Abstract GNSS/INS applications are being developed, especially for direct georeferencing in airborne photogrammetry. Achieving accurately georeferenced products from the integration of GNSS and INS requires removing systematic errors in the mobile mapping systems. The INS sensor's uncertainty is decreasing; therefore, the influence of the deflection of verticals (DOV, the angle between the plumb line and normal to the ellipsoid) should be considered in the direct georeferencing. Otherwise, an error is imposed for calculating the exterior orientation parameters of the aerial images and aerial laser scanning. This study determines the DOV using the EGM2008 model and gravity data in Sweden. The impact of the DOVs on horizontal and vertical coordinates, considering different flight altitudes and camera field of view, is assessed. The results confirm that the calculated DOV components using the EGM2008 model are sufficiently accurate for aerial mapping system purposes except for mountainous areas because the topographic signal is not modelled correctly.

The Cretaceous basins of the West and Central African Rift System (WCARS) are characterized by sinistral strike–slip movements observed between the Benue and Arabian–Nubian microplates. These basins share a similar basin‐filling structure, history, and tectonic processes. They have attracted a significant interest in the study of their geodynamics and subsurface structure through geophysical exploration methods. Nevertheless, North Cameroon located in this microplate confluence has not yet been investigated in terms of identifying geological structures, such as lineaments and faults. To contribute to a better understanding of the northern Cameroon structural framework and its tectonic context, we investigate the lineaments in northern Cameroon by using the EIGEN‐6C4 gravitational model and a variety of recent processing techniques (Tilt derivative [TDR], Theta Map [TM], Horizontal tilt angle [TDX], and Edge Detector [ED]). Our results show that the lineaments are trending in ENE–WSW, NW–SE, NE–SW, and WNW–ESE directions. These directions are consistent with the Cretaceous Garoua Rift and granitoids of the Cameroon‐Chad line. The presented result clearly delineates continuous architectonic features of the structural edges of the Saharan Metacraton, the Cretaceous Garoua Rift, the Bibemi‐Léré granitoids, and the Adamawa faults.

<p>The lithospheric thickness beneath and around Greenland varies from a few tens of kilometres in offshore regions to several tens of kilometres (up to 200 – 250 km) in land areas. But, due to different datasets and techniques applied in geophysical studies, there are large differences between the different geophysical lithosphere models. As an example, lithosphere models from seismological datasets show generally larger values (above 100 km), while models using gravity or thermal datasets tend to be thinner (values mostly below 100 km). To model the deformation associated with the melting of the Greenland Ice Sheet a detailed lithosphere model is required. Nevertheless, seismologically obtained lithosphere models are the ones usually applied in these so-called glacial isostatic adjustment (GIA) models. Besides, GIA models can be used to provide additional constraints on the lithospheric thickness.</p><p>Results from most 3D GIA models are compared to observed vertical velocities only, while horizontal velocities are known to be sensitive to the lateral variations of the Earth (e.g., lithospheric thickness). But, horizontal velocities from incompressible GIA models, which are commonly used, are not suitable due to the neglect of material parameter changes related to the dilatation. Compressible GIA models in turn can provide more accurate estimates of the horizontal and vertical viscoelastic deformations induced by ice-mass changes. Here, we use a variety of lithospheric thickness models, obtained from gravity, thermal, and seismological datasets, in a three-dimensional compressible GIA Earth model. The GIA model will be constructed using the finite-element software ABAQUS (Huang et al., under review in GJI) and applying recent ice history models Huy3 and GLAC-GR2a for Greenland in combination with the Little Ice Age deglaciation model by Kjeldsen et al. (2015). We will compare various lithosphere models, including their impact on the modelled 3D velocity field, and compare these against independent GNSS (Global Navigation Satellite System) observations.</p><p>