Geological Survey of Finland

Magnetotellurics (MT) images electrical conductivity, a property influenced by fluids, alteration, graphite, and partial melt. Because many different subsurface configurations can explain the MT responses observed in the field, the preferred subsurface conductivity model estimated through inversion is often ambiguous. A central challenge is that a robust stochastic model exploration in 3D, while conceptually the best way to expose such ambiguity, is too computationally demanding to be used as a standard practice. Consequently, most studies report a single deterministic model, which obscures the range of alternative geological structures that are equally consistent with the data.In this work we propose a practical approach to stochastic model exploration in 3D MT inversion. Drawing inspiration from annealing methods, we adopt a Very Fast Simulated Annealing (VFSA) framework, with sparse parameterization that makes the optimisation feasible for large-scale problems. Our inversion algorithm is built around the widely used ModEM forward solver, ensuring compatibility with existing workflows. Instead of producing one definitive model, the workflow can generate a set of plausible models that explain the data equally well. From this ensemble one can compute statistical summaries: a mean model that captures the most consistent structures and quantitative measures of variability that highlight where geometry, depth, or connectivity remain uncertain. This representation enables geologists to make interpretations while being explicitly aware of the uncertainty inherent in the inversion. We demonstrate that the approach works at regional scale using a large-area subset of USArray MT data from Cascadia. This dataset has been extensively studied and previously modelled with deterministic 3D inversion, which allows us to benchmark our results.

<strong class="journal-contentHeaderColor">Abstract.</strong> Groundwater is a critical resource supplying nearly half of the world's drinking water. This study focuses on the Kurikka buried valley aquifer system in western Finland, characterized by complex hydrogeology dictated by the bedrock topography and sediment cover producing artesian conditions in deep aquifers. Using a multitracer approach, the study incorporates hydrogeochemical, isotopic (&delta;³⁴S, ⁸⁷Sr/⁸⁶Sr) and microbial community analyses with residence time indicators (CFCs, SF₆, ³H, ³H/³He). Groundwater samples collected from 10 sites revealed differences in residence times, microbial diversity and community compositions, as well as large variation in the strontium and sulfur isotopic compositions. The bedrock groundwater sample revealed a more evolved water type, consistent with longer residence time, strong water-mineral interactions and typical deep subsurface bacterial members. Groundwater from the superficial unconsolidated<span> </span>aquifers contained a modern water component (&lt;60 years) whereas the deeper buried valley aquifers were characterized by older waters. The information provided by this study is crucial for groundwater management during extensive extraction for municipal water supply.

Abstract This study addresses the crucial detection of offsets in GNSS time series for accurate velocity estimations, vital in geosciences and engineering. Existing methods are challenged by correlated noise and can suffer from over-segmentation or high false positive rates. A novel methodology is proposed that combines a modified bilateral filter and an adapted implementation of the Pruned Exact Linear Time (PELT) algorithm, optimizing the detection of abrupt changes in the presence of complex noise. The technique was evaluated using a set of 3450 synthetic time series and 45 real time series from Global Navigation Satellite System (GNSS) stations located in Northern Europe. In the synthetic time series, the success threshold of 80 % was exceeded for the horizontal component with offsets of 1.2 mm, and the 90 % threshold for offsets of 1.4 mm. For the vertical component, 80 % success was achieved with offsets of 4 mm and 90 % with offsets of 5 mm. Regarding the real time-series, success percentages of 87.1 % were obtained for the East component, 74.4 % for the North component, and 74.2 % for the vertical component (Up). This hybrid technique enhances the identification of real offsets in GNSS time series, simplifying monitoring and paving the way for fully automated workflows.

Among the major challenges facing the mineral processing industry is the simultaneous need to increase productivity while reducing environmental impact. This study explores the potential of polymer- surfactant (PS) mixture composed of short-chain alcohols combined with hydroxypropyl methyl cellulose (HPMC) as a new environmentally friendly frother produced from sustainable sources. Ethanol, pentanol, and octanol were evaluated as surfactant fraction due to their availability and relatively low cost, alongside the polyglycol based commercial frother (Dowfroth 200) as a benchmark. The result demonstrates that longer-chain alcohols are more effective at preventing bubble coalescence, longer-chain alcohol achieving unimodal distributions at lower concentrations. Interestingly, HPMC exhibited unique behavior due to its macromolecular structure, forming a stable yet slow-diffusing layer around bubbles, resulting in bimodal distributions even at higher concentrations. Mixtures of HPMC and alcohols, particularly pentanol and octanol, show synergistic effects that enhance the initial stabilization of the air-liquid interface, facilitating unimodal distributions at relatively low concentrations. These findings offer valuable insights for optimizing frother formulations to improve flotation efficiency.

<strong class="journal-contentHeaderColor">Abstract.</strong> Groundwater is a critical resource supplying nearly half of the world's drinking water. This study focuses on the Kurikka buried valley aquifer system in western Finland, characterized by complex hydrogeology dictated by the bedrock topography and sediment cover producing artesian conditions in deep aquifers. Using a multitracer approach, the study incorporates hydrogeochemical, isotopic (&delta;³⁴S, ⁸⁷Sr/⁸⁶Sr) and microbial community analyses with residence time indicators (CFCs, SF₆, ³H, ³H/³He). Groundwater samples collected from 10 sites revealed differences in residence times, microbial diversity and community compositions, as well as large variation in the strontium and sulfur isotopic compositions. The bedrock groundwater sample revealed a more evolved water type, consistent with longer residence time, strong water-mineral interactions and typical deep subsurface bacterial members. Groundwater from the superficial unconsolidated<span> </span>aquifers contained a modern water component (&lt;60 years) whereas the deeper buried valley aquifers were characterized by older waters. The information provided by this study is crucial for groundwater management during extensive extraction for municipal water supply.

<strong class="journal-contentHeaderColor">Abstract.</strong> The changing Arctic climate alters the dynamics of melting and freezing in the ground. An increasing number of frost quakes have been reported in boreal regions such as Finland and Canada, which can cause damage to infrastructure by fracturing roads and built structures. A methodology has been developed to assess frost quakes by estimating thermal stresses in the soil in Oulu, Finland. Information on temporally and spatially varying soil properties, such as soil temperature and soil ice content, is required to calculate thermal stress. Further developing this methodology on a larger scale, over Finland, is challenging due to a lack of in-situ measurements of these parameters with high spatial and temporal coverage. However, they can be simulated using land surface models, one of which is HydroBlocks. Previously, HydroBlocks has been applied in the contiguous United States. The goal of this paper was to configure the model in subarctic and arctic Finland. HydroBlocks' ability to produce accurate snow accumulation and melt approximations, as well as estimate soil temperature and soil water content at different depths in Finland, has not been evaluated before. In addition, maps and time series of soil ice content in Finland at different depths were produced. The snow model (snow water equivalent) and the modeled soil temperatures and soil water contents were compared with the observational data to evaluate the model performance. From the calibrated model, for six observational SWE stations, the average RMSE and KGE were 43 mm and 0.07, respectively. The worst KGE was -0.88, and the best was 0.78. From the calibrated model, for the three observational soil stations, the soil temperature had an average RMSE and KGE of 2.2 &deg;C and 0.66, respectively. The worst KGE was 0.41, and the best was 0.89. For the soil water content, the average RMSE and KGE were first, 0.15 <span style="border-bottom: 1px solid #000; vertical-align: 50%; font-size: .7em; color: #000;">vol</span><span style="margin-left: -1.3em; margin-right: .5em; vertical-align: -15%; font-size: .7em; color: #000;">vol</span> and -4.88, and after calibration, they were reduced to 0.07 <span style="border-bottom: 1px solid #000; vertical-align: 50%; font-size: .7em; color: #000;">vol</span><span style="margin-left: -1.3em; margin-right: .5em; vertical-align: -15%; font-size: .7em; color: #000;">vol</span> and -0.75, respectively. For the calibrated model, the worst KGE was -2.2, and the best was 0.08. The modelling results emphasize the importance of calibrating the model with local soil hydraulic parameters. The modeling results indicate that outputs from HydroBlocks can generally predict soil conditions in Finland. Furthermore, the obtained soil temperature and soil ice content can be used to calculate thermal stresses in soils and identify frost quake-prone areas regionally across Finland over recent decades, ultimately estimating the risk caused by frost quakes.

Abstract Cold plasma distribution in the ionosphere‐plasmasphere system governs wave‐particle interactions, plasma energization and loss, and radio wave propagation. A longstanding observational gap at altitudes 800–8,000 km has largely prevented studying the coupled dynamics of the two regions. Here, we show that observations by JAXA's Arase mission can bridge this gap. Electron densities inferred from the upper hybrid resonance frequencies measured by Arase are highly consistent with radio occultation profiles from the Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC) mission, with a median difference of 5%. Using the combined COSMIC‐Arase data set, we provide a convenient way to reconcile the two regions in empirical models based on the analytical Chapman function inversion for scale height. Our results enable studying fundamental questions about the ionosphere‐plasmasphere coupling, their transition, and life cycle of cold plasma in near‐Earth space.

<strong class="journal-contentHeaderColor">Abstract.</strong> Groundwater is a critical resource supplying nearly half of the world's drinking water. This study focuses on the Kurikka buried valley aquifer system in western Finland, characterized by complex hydrogeology dictated by the bedrock topography and sediment cover producing artesian conditions in deep aquifers. Using a multitracer approach, the study incorporates hydrogeochemical, isotopic (&delta;³⁴S, ⁸⁷Sr/⁸⁶Sr) and microbial community analyses with residence time indicators (CFCs, SF₆, ³H, ³H/³He). Groundwater samples collected from 10 sites revealed differences in residence times, microbial diversity and community compositions, as well as large variation in the strontium and sulfur isotopic compositions. The bedrock groundwater sample revealed a more evolved water type, consistent with longer residence time, strong water-mineral interactions and typical deep subsurface bacterial members. Groundwater from the superficial unconsolidated<span> </span>aquifers contained a modern water component (&lt;60 years) whereas the deeper buried valley aquifers were characterized by older waters. The information provided by this study is crucial for groundwater management during extensive extraction for municipal water supply.

Abstract. Groundwater is a critical resource supplying nearly half of the world's drinking water. This study focuses on the Kurikka buried valley aquifer system in western Finland, characterized by complex hydrogeology dictated by the bedrock topography and sediment cover producing artesian conditions in deep aquifers. Using a multitracer approach, the study incorporates hydrogeochemical, isotopic (δ34S, 87Sr/86Sr) and microbial community analyses with residence time indicators (CFCs, SF6, 3H, 3H/3He). Groundwater samples collected from 10 sites revealed differences in residence times, microbial diversity and community compositions, as well as large variation in the strontium and sulfur isotopic compositions. The bedrock groundwater sample revealed a more evolved water type, consistent with longer residence time, strong water-mineral interactions and typical deep subsurface bacterial members. Groundwater from the superficial unconsolidated aquifers contained a modern water component (&lt;60 years) whereas the deeper buried valley aquifers were characterized by older waters. The information provided by this study is crucial for groundwater management during extensive extraction for municipal water supply.