Arctic areas are heavily affected by climate change. The temperature is increasing, the permafrost is melting, the sea ice is disappearing, and the glaciers are retreating. The elastic response of the changes in the glacier affects the earth crust. Locally on Greenland or Svalbard the uplift can reach several centimetres per year. The ice melting in Greenland is so large that it affects the land uplift in large parts of the Northern hemisphere. The geodetic observatory in Ny-Ålesund is a key station in the global geodetic network. It is the northern most fundamental station, containing all the main geodetic techniques and important for the realisation of the ITRF. However, its stability has been questioned. The observatory experience variations in the uplift on seasonal, inter-annual, decadal and longer timescales. The uplift for a moving window of 5-years periods has increased from below 6 mm/yr in the 1990 to more than 12 mm/yr today. This has challenged the realisation and stability of global and regional reference frames. We have modelled the elastic response of glacier changes based on various glaciological sources. These results will be presented. We will in particular compare the elastic uplift with geodetic time-series from Ny-Ålesund and other GNSS in Svalbard and discuss how this could affect reference frames. Could for instance the VLBI scale issue in ITRF2020 be related to glacial changes? We found that the variations in the uplift can be explained by the glacier changes and close to 50% of the VLBI scale drift can be explained by glacier related accelerating uplift.

Non-Tidal Atmospheric Loading (NTAL) plays a crucial role in the precision and reliability of GNSS-based positioning and geophysical interpretations, particularly in high-latitude regions, sensitive to atmospheric dynamics. This investigation examines the influence of non-tidal atmospheric loading on GNSS time series and velocities derived from them for high-latitude regions. With a dataset from 2020 to 2023, we process a GNSS network across northern Europe, focusing on the Finnish permanent GNSS network (FinnRef). Using GAMIT/GLOBK software, where corrections are applied at the observation level, we incorporate a new atmospheric grid model derived from the European Centre for Medium-Range Weather Forecasts (ECMWF) numerical weather data. This model provides higher spatial resolution compared to previously available models in GAMIT/GLOBK. Temporal variability of NTAL-corrected GNSS time series is reduced by 17% in the vertical component, and by 8% and 2% in the north and east components, respectively, across the FinnRef network. Additionally, our results highlight that NTAL correction lowers vertical trend uncertainty by an average of 33.5%. Besides evaluating metrics such as spectral power density (PSD) and annual amplitude variation, we observe that the spectral index of the vertical component drops from − 1.44 to − 0.9, indicating reduced long-term noise correlation. We also compare this observation-level approach with an alternative method that applies NTAL corrections at the raw-data level and find that the observation-level correction shows slightly better performance. These results demonstrate that significant improvements in the stability of GNSS time series can be expected after NTAL application, especially in the vertical component.

A record-breaking melt season affected the Arctic glaciers of Svalbard in summer 2024 by a substantial margin. Across the entire archipelago, glacier melting corresponded to an anomaly of up to four SD and exceeded any previous observation. The pan-Svalbard mass loss in summer 2024 amounts to ~61.7 ± 11.1 Gt and corresponds to 1% of the total ice volume on Svalbard and is comparable to that of the Greenland ice sheet (55 ± 35 Gt), which occupies an area about 50 times larger. Altogether, Svalbard and other glacier regions surrounding the Barents Sea lost 102.1 ± 22.9 Gt of ice in a single year and contributed 0.27 ± 0.06 mm (of which 0.16 mm alone is due to Svalbard) to global sea-level, putting the circum-Barents region among the strongest contributors to global sea-level rise in 2024. Most of the 2024 glacier melt occurred during a 6-wk period of persistent atmospheric circulation pattern causing record-high air temperatures, an event with an extremely low recurrence interval under current climate conditions. However, future climate projections suggest that such temperature levels will become increasingly commonplace by the end of the 21st century, potentially even surpassing those of 2024. Svalbard's summer of 2024 serves as a forecast for future glacier meltdown in the Arctic, offering a glimpse into conditions 70 y ahead.

This study evaluates noise variance characteristics at configured GNSS stations using a combination of Factor Analysis (FA), stacked Gauss Markov Random Field (GMRF), and Structured Additive Predictor (SAP). FA is employed to decompose the variance in CGNSS time series into station-specific and common components. Shorter correlation times are dominated by specific variance, which accounts for over 60

SUMMARY We analyse Global Navigation Satellite System (GNSS) data from Svalbard to understand how uplift rates are controlled by the elastic and viscoelastic response of the solid Earth to changes in glacier mass on annual, interannual, decadal, centennial and millennial timescales. To reveal local patterns of deformation, we filter the GNSS time-series with an enhanced common-mode filtering technique where the non-tidal loading signal is incorporated. This technique reduces the estimated uncertainties for 5-yr time-series from 0.8 to 0.3 mm yr–1. Analysis of the GNSS data with different software–GAMIT, GipsyX, and GINS–produce consistent results that all indicate large temporal variations in uplift. For example, at the Ny-Ålesund GNSS station, uplift varies between 6 and 12 mm yr–1 for different 5-yr periods, and also shows a significant increase in the last 15 yr. We show that this increase is due to climate change-related ice mass loss in Svalbard. We constrain recent glacier retreat on Svalbard using a series of digital elevation models, and then correct the GNSS-derived uplift records for the elastic signal from these ice mass changes. The residual uplift signal is relatively constant, confirming the hypothesis that current ice mass changes exert a strong influence on GNSS observations. The relatively constant record of residual uplift can be used to constrain other geophysical signals such as the viscoelastic response of the solid Earth to ice loading during the Little Ice Age and the Last Glacial Period. We review uplift results from previous viscoelastic modelling studies and show that the residual signal cannot yet be fully explained. Our new uplift results thus motivate the need for new viscoelastic modelling of the glacial isostatic adjustment process in Svalbard.

We processed time series from seven Global Navigation Satellite System (GNSS) stations and one Very Long Baseline Interferometry (VLBI) station in Svalbard. The goal was to capture the seasonal vertical displacements caused by elastic response of variable mass load due to ice and snow accumulation. We found that estimates of the annual signal in different GNSS solutions disagree by more than 3 mm which makes geophysical interpretation of raw GNSS time series problematic. To overcome this problem, we have used an enhanced Common Mode (CM) filtering technique. The time series are differentiated by the time series from remote station BJOS with known mass loading signals removed a priori. Using this technique, we have achieved a substantial reduction of the differences between the GNSS solutions. We have computed mass loading time series from a regional Climatic Mass Balance (CMB) and snow model that provides the amount of water equivalent at a 1 km resolution with a time step of 7 days. We found that the entire vertical loading signal is present in data of two totally independent techniques at a statistically significant level of 95%. This allowed us to conclude that the remaining errors in vertical signal derived from the CMB model are less than 0.2 mm at that significance level. Refining the land water storage loading model with a CMB model resulted in a reduction of the annual amplitude from 2.1 mm to 1.1 mm in the CM filtered time series, while it had only a marginal impact on raw time series. This provides a strong evidence that CM filtering is essential for revealing local periodic signals when a millimetre level of accuracy is required.

In Fennoscandia, tectonics, Glacial Isostatic Adjustment (GIA), and climatic changes cause ongoing crustal deformation of some millimetres per year, both vertically and horizontally. These displacements of the Earth can be measured to a high degree of precision using a Global Navigation Satellite System (GNSS). Since about three decades, this is the major goal of the Baseline Inferences for Fennoscandian Rebound, Sea-level, and Tectonics (BIFROST) project. We present a new velocity field for an extended BIFROST GNSS network in the ITRF2008 reference frame making use of the GNSS processing package GPS Analysis Software of MIT (GAMIT). Compared to earlier publications, we have almost doubled the number of stations in our analysis and increased the observation time span, thereby avoiding the early years of the network with many instrument changes. We also provide modelled vertical deformation rates from contributing processes, i.e. elastic deformation due to global atmospheric and non-tidal ocean loading, ice mass and hydrological changes as well as GIA. These values for the vertical component can be used for removal of these contributions so that the residual uplift signal can be further analysed, e.g., in the context of local or regional deformation processes or large-scale but low-magnitude geodynamics. The velocity field has an uplift maximum of 10.3 mm/yr in northern Sweden west of the Gulf of Bothnia and subsidence exceeding 1 mm/yr in northern Central Europe. The horizontal velocity field is dominated by plate motion of more than 20.0 mm/yr from south-west to north-east. The elastic uplift signal sums up to 0.7-0.8 mm/ yr for most stations in Northern Europe. Hence, the maximum uplift related to the past glaciation is ca. 9.6 mm/ yr. The residual uplift signal after removal of the elastic and GIA contribution may point to possible improve-ments of the GIA model, but may also indicate regional tectonic and erosional processes as well as local deformation effects. We show an example of such residual signal discussing potential areas of interest for further studies.

The European Plate Observing System (EPOS) is a European project about building a pan-European infrastructure for accessing solid Earth science data, governed now by EPOS ERIC (European Research Infrastructure Consortium). The EPOS-Norway project (EPOS-N; RCN-Infrastructure Programme - Project no. 245763) is a Norwegian project funded by National Research Council. The aims of EPOS-N project are divided into four work packages where one of them is about integrating Norwegian geoscientific data into an e-infrastructure. The other three work packages are: management of the project, improving the geoscientific monitoring in the Arctic and establishing Solid Earth Science Forum to communicate the progress within the geoscientific community and also providing feedback to the development group of the e-infrastructure. Among the six EPOS-N project partners, five institutions are actively participating and providing data in the EPOS-N project – University of Bergen (UIB), University of Oslo (UIO), Norwegian Mapping Authority (NMA), Geological Survey of Norway (NGU) and NORSAR. The data which are about to be integrated are divided into categories according to the thematic fields – seismology, geodesy, geological maps and geophysical data. Before the data can be integrated into the e-infrastructure their formats need to follow the international standards which were already developed by the communities of geoscientists around the world. Metadata are stored in Granularity Database tool and easily accessible by other tools via dedicated API. For now, there are 33 Data, Data Products, Software and Services (DDSS) described in EPOS-N list. We present the Norwegian approach of integration of the geoscientific data into the e-infrastructure, closely following the EPOS ERIC development. The sixth partner in the project – NORCE Norwegian Research Centre AS is specialized in visualizations of data and developing the EPOS-N Portal. It is web-based graphical user interface adopting Enlighten-web software which allows users to visualize and analyze cross-disciplinary data. Expert users can launch the visualization software through a web based programming interface (Jupyter Notebook) for processing of the data. The seismological waveform data (provided by UIB and NORSAR) will be available through an EIDA system, seismological data products (receiver functions, earthquake catalogues and macroseismic observations) as individual datasets or through a web service, GNSS data products (provided by NMA) through standalone files and geological and geophysical (magnetic, gravity anomaly) maps (provided by NGU) as WMS web services or standalone files. Integration of some specific geophysical data is still under discussion, such as georeferenced cross-sections which are of interest especially for visualization with other geoscientific data. Constant user feedback is achieved through dedicated workshops. Various use cases are defined by users and have been tested in these workshops. Collected feedback is being used for further development and improvements of the EPOS-N Portal.

We present the official land uplift model NKG2016LU of the Nordic Commission of Geodesy (NKG) for northern Europe. The model was released in 2016 and covers an area from 49° to 75° latitude and 0° to 50° longitude. It shows a maximum absolute uplift of 10.3 mm/a near the city of Umeå in northern Sweden and a zero-line that follows the shores of Germany and Poland. The model replaces the NKG2005LU model from 2005. Since then, we have collected more data in the core areas of NKG2005LU, specifically in Norway, Sweden, Denmark and Finland, and included observations from the Baltic countries as well. Additionally, we have derived an underlying geophysical glacial isostatic adjustment (GIA) model within NKG as an integrated part of the NKG2016LU project. A major challenge is to estimate a realistic uncertainty grid for the model. We show how the errors in the observations and the underlying GIA model propagate through the calculations to the final uplift model. We find a standard error better than 0.25 mm/a for most of the area covered by precise levelling or uplift rates from Continuously Operating Reference Stations and up to 0.7 mm/a outside this area. As a check, we show that two different methods give approximately the same uncertainty estimates. We also estimate changes in the geoid and derive an alternative uplift model referring to this rising geoid. Using this latter model, the maximum uplift in Umeå reduces from 10.3 to 9.6 mm/a and with a similar reduction ratio elsewhere. When we compare this new NKG2016LU with the former NKG2005LU, we find the largest differences where the GIA model has the strongest influence, i.e. outside the area of geodetic observation. Here, the new model gives from − 3 to 4 mm/a larger values. Within the observation area, similar differences reach − 1.5 mm/a at the northernmost part of Norway and − 1.0 mm/a at the north-western coast of Denmark, but generally within the range of − 0.5 to 0.5 mm/a.

There is a growing need for geodetic reference frames that on a national level support the increasing use of global positioning services. Today, the vast majority of countries have their own national reference frame. In Europe this frame is normally aligned to ETRS89. This system is co-moving with the Eurasian tectonic plate. Global Navigation Satellite Systems (GNSS) and global positioning services are normally aligned to the Earth as a whole through a global reference frame like ITRF2014. Consequently, global positioning services does not give direct access to the national reference frame without a timedependent transformation. A solution is to align the national reference frame directly to a global reference frame. In such a frame, the coordinates of a point fixed to the ground will change with time, a fact leading to the expression dynamic reference frame (DRF). To be prepared for future challenges, the Nordic Geodetic Commission (NKG) initiated a pilotproject on DRF in Iceland. Iceland has a very active and complex geodynamic situation. It is located at the boundary of two tectonic plates and affected by seismic and volcanic activity, recent ice loading changes as well as glacial isostatic adjustment (GIA). Due to this, the traditional concept of a static geodetic reference frame is difficult to maintain at the uncertainty level required by modern applications. Iceland was therefore a natural place to investigate the concept of DRF. This paper focuses on the outcome and conclusions of the DRF project in Iceland. We give ten preconditions for a DRF. Living on an ever-changing Earth, we see that many of these preconditions have to be in place regardless of type of reference frame. Through the work in the Nordic countries and NKG, the Nordic area will be well prepared for the future challenges. However, some legal issues for instance, can be challenging. A two-frame solution combining staticand dynamicreference frames seems like the best alternative in the foreseeable future.

Crustal deformation in the seismically active Nordland area in Northern Norway is estimated based on a combination of data from local episodic epGNSS campaigns (three 5-day campaigns in 1999, 2008 and 2015) and continuously operating cGNSS stations in the area that were mainly established in 2008 and in 2009. To establish a local long-term stable reference frame, which is consistent both with the epGNSS network and the network of newer cGNSS, a three-step procedure for reference frame realization is used to get consistent results from all the stations in the area. Analysis of the main error sources shows that uncertainties for the episodic epGNSS stations are around 0.2mm/yr in the horizontal components and 0.5mm/yr in the vertical component. The results support earlier findings that Ranafjord area of the Nordland is undergoing crustal spreading with horizontal displacement velocities of ca. 1.0±0.2mm/yr, predominantly in the east-west direction. The results also show a gradient in the uplift along the coast of Nordland that is larger than predicted by existing glacial isostatic adjustment models.

This study combines remote sensing data from ground- and satellite-based radar to calculate 3D displacement vectors for the Jettan rockslide, Troms, northern Norway. Using 3D displacement vectors, aspect data and strain rates in conjunction with structure (foliation, faults, fractures), geomorphological elements (ridges, scarps, terraces, depressions), topography and borehole data, we identify zones undergoing displacement, e.g., extension and compression, displacement into- or out-of-the-slope and/or various degrees of tilting. Our results show variable 3D displacement velocities, from north to south, that segment the rockslide into distinct domains. Displacement patterns are structurally controlled, as spatial variation in azimuth and plunge of 3D displacement vectors can be related to variation in attitudes of the host-rock foliation, faults and fractures. In the north, a complex graben system surrounded by orthogonal NW-SE and NE-SW-trending geomorphological elements, shows a repeated stepping 3D displacement pattern. This may indicate a complex fault geometry at depth, including stepped and discontinuous slide surfaces. We interpret 3D displacement into-the-slope in the upper part, and out-of-the-slope in the lower part, to be back-rotation of antithetic blocks with planar fractures becoming curved/listric gliding surfaces with depth. Downslope reduction in velocity indicates compression and stacking of blocks. In the southern area, N-S-trending geomorphological elements are arranged parallel to the hillslope. 3D displacement vectors show a more homogenous displacement pattern indicating movement along planar, hillslope-parallel, fracture sets at depth. We propose a structural controlled slope displacement model including alternate planar- and wedge-failure, in addition to displacement along planar and listric fractures merging into foliation at depth. Using the Jettan rockslide as a case study, we show how remote sensing data may aid examination of structural and topographic controls on rockslide kinematics, thus giving new insights into subsurface geometry

It is well known that satellite radar interferometry (InSAR) is capable of measuring surface displacement with a typical accuracy on the order of millimeters to centimeters. However, when the true deformation vector differs from the satellite line-of-sight (LOS), the sensitivity decreases and interpretation of InSAR deformation measurements becomes challenging.By combining displacement data from extensive ascending and descending TerraSAR-X datasets collected during the summer seasons of 2009–2014, we estimate two-dimensional (2D) InSAR surface displacement. Displacement data are decomposed into vertical and west/east deformation, dip and combined deformation vector, and validated using Global Navigation Satellite System (GNSS) data. We use the decomposed dataset to visualize variations in surface velocity and direction on unstable slopes in a periglacial environment with sporadic permafrost in northern Norway. By identifying areas with uplift and subsidence, and detecting velocity changes (downslope acceleration/deceleration) and related areas of extension and compression, we are able to explain driving and controlling mechanisms and geomorphology in two rockslides and one area with solifluction landforms.

Changes to mean sea level and/or sea level extremes (e.g., storm surges) will lead to changes in coastal impacts. These changes represent a changing exposure or risk to our society. Here, we present 21st century sea-level projections for Norway largely based on the Fifth Assessment Report from the Intergovernmental Panel for Climate Change (IPCC AR5). An important component of past and present sea-level change in Norway is glacial isostatic adjustment. We therefore pay special attention to vertical land motion, which is constrained using new geodetic observations with improved spatial coverage and accuracies, and modelling work. Projected ensemble mean 21st century relative sea-level changes for Norway are, depending on location, from −0.10 to 0.30 m for emission scenario RCP2.6; 0.00 to 0.35 m for RCP 4.5; and 0.15 to 0.55 m for RCP8.5. For all RCPs, the projected ensemble mean indicates that the vast majority of the Norwegian coast will experience a rise in sea level. Norway’s official return heights for extreme sea levels are estimated using the average conditional exceedance rate (ACER) method. We adapt an approach for calculating sea level allowances for use with the ACER method. All the allowances calculated give values above the projected ensemble mean Relative Sea Level (RSL) rise, i.e., to preserve the likelihood of flooding from extreme sea levels, a height increase above the most likely RSL rise should be used in planning. We also show that the likelihood of exceeding present-day return heights will dramatically increase with sea-level rise.