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Publikasjonar frå instituttet
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Denton, C. Adeene; Asphaug, Erik; Baijal, Namya & Melikyan, Robert E.
(2026).
Collisional Capture of an Intact Moon Depends on Strength.
Astrophysical Journal Letters.
ISSN 2041-8205.
1008(1).
doi:
10.3847/2041-8213/ae91e9.
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Sjur, Anna Lina Petruseviciute; Isachsen, Pål Erik; Nilsson, Johan & Allen, Susan Elizabeth
(2026).
Nonlinear dynamics of time-variable slope circulation.
Ocean Science.
ISSN 1812-0784.
22(5),
s. 3055–3078.
doi:
10.5194/os-22-3055-2026.
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Bottom topography strongly constrains ocean circulation in the Arctic, and both theory and numerical modeling suggest that nonlinear flow–topography interactions influence slope-following currents. Yet, how such interactions modify the circulation response to time-variable surface forcing remains poorly understood. Using idealized shallow-water simulations of flow over a corrugated slope in a re-entrant channel, we investigate how nonlinear features arise and evolve under oscillatory forcing. We observe both a prograde flow bias (aligned in the direction of topographic Rossby wave propagation) relative to linear estimates, and retrograde flow (opposing wave propagation) exhibiting flow strength saturation once the flow reaches sufficiently strong velocities. To identify the mechanisms responsible for these behaviors, we evaluate integrated momentum budgets. Which terms appear as dynamically relevant, in addition to linear surface and bottom frictional stresses, depends on the choice of integration path: when integrated along isobaths, the nonlinear dynamics appear as a cross-slope relative vorticity flux, whereas integration along straight transects instead highlights momentum flux convergence and topographic form stress. These perspectives can be unified under quasi-geostrophic scaling as describing a flux of potential vorticity (PV). This PV flux is predominantly down-slope and strongest during retrograde phases, resulting in the prograde bias. When retrograde velocities approach the arrest speed of topographic Rossby waves with wavelengths comparable to the corrugation wavelength, the flux increases sharply, halting further acceleration and producing the observed asymmetry. The interplay between forcing timescale and frictional timescale shapes how these nonlinear effects manifest: when the forcing period is comparable to the dampening timescale, the response is strongly low-pass filtered, whereas for much longer forcing periods the flow has time to adjust toward distinct prograde and retrograde states. These results show how flow–topography interactions shape time-variable slope circulation, biasing the flow toward prograde states and limiting retrograde flow strength. Such effects are likely under-represented in coarse-resolution numerical simulations, and highlight the need for improved representations of unresolved topographic interactions.
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Domeier, Mathew Michael; Gallo, Leandro C.; Marcilly, Chloé M. & Torsvik, Trond H.
(2026).
Quadrupolar sea level fluctuations reveal episodes of rapid polar wander.
Science.
ISSN 0036-8075.
394(6819),
s. 87–90.
doi:
10.1126/science.aec8423.
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True polar wander (TPW) is presently occurring at a rate of ~10 centimeters per year, exceeding the mean rate of differential plate motion. Whether this rate is transient and negligible on geological timescales or whether Earth has experienced rapid TPW lasting millions of years is unclear. Paleomagnetic evidence has been used to propose fast episodes of TPW, but limitations of the paleomagnetic record have precluded definitive results. Rapid TPW will induce global sea level fluctuations associated with relative changes in centrifugal potential, offering an independent test. We evaluated this prediction using continental flooding reconstructions and identified multiple robust quadrupolar patterns since 320 million years ago, confirming that protracted rapid TPW has occurred on Earth and that couplings among Earth’s rotational dynamics, mantle processes, and surface environments can be strongly episodic.
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Barna, Danielle Marie; Engeland, Kolbjørn; Kneib, Thomas; Thorarinsdottir, Thordis Linda & Xu, Chong-Yu
(2026).
Regional flood frequency analysis at multiple durations: A comparison of duration consistency in quantile and parameter regression techniques.
Hydrology Research.
ISSN 1998-9563.
57(5).
doi:
10.1016/j.hydrch.2026.100002.
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Wolf, Eva; Stutzmann, Eléonore; Metaxian, Jean Philippe; Nanni, Ugo; Miesen, Floreana M. & Jenkin, Matt
[Vis alle 8 forfattere av denne artikkelen]
(2026).
Locating a complex subglacial drainage network using seismic arrays on Glacier d’Otemma, Switzerland.
Journal of Glaciology.
ISSN 0022-1430.
72.
doi:
10.1017/jog.2026.10200.
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Glaciers actively store and release meltwater with significant impacts on glacier flow velocity and downstream environments. The evolution of this drainage system is a key component in understanding glacier dynamics. In temperate alpine glaciers, the change of the subglacial drainage network from distributed to channelised is theoretically known, but lacks empirical documentation. As subglacial channels are extremely difficult to access, it is important to test innovative methods for locating them. Here, we use surface seismic monitoring, which enables us to identify the location of multiple subglacial channels below Glacier d’Otemma, Valais, Switzerland. We calculate time delays between pairs of seismic sensors and backtrack source locations. Using matched field processing and beamforming analysis, we obtain spatial and temporal patterns of seismic noise produced by the glacier. This allows us to interpret a possible evolution of the subglacial drainage network from a distributed to an efficient one and locate three distinct subglacial channels in close proximity.
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Heyerdahl, Håkon
(2026).
Influence of long-term rainfall on the stability of an unsaturated slope in Norway–a case study.
Georisk: Assessment and Management of Risk for Engineered Systems and Geohazards.
ISSN 1749-9518.
doi:
10.1080/17499518.2026.2716834.
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Bredal, Marie Bergvik; Rouyet, Line; Wendt, Lotte; Hindberg, Heidi; Stødle, Daniel & Lauknes, Tom Rune
[Vis alle 14 forfattere av denne artikkelen]
(2026).
Brief communication: InSAR Svalbard Ground Motion Service – observing surface displacements in the High Arctic.
Earth Observation (EO).
1(1),
s. 121–128.
doi:
10.5194/eo-1-121-2026.
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The InSAR Svalbard Ground Motion Service (GMS) provides open-access surface displacement maps and time series in the Svalbard archipelago, derived from Sentinel-1 Interferometric Synthetic Aperture Radar (InSAR). The service provides seasonal products capturing short-term 2016–2024 displacements and interannual products documenting long-term 2018–2024 velocity trends. InSAR Svalbard covers five areas on Spitsbergen Island (Longyearbyen, Ny-Ålesund, Svea, Hornsund and Kapp Linné). The service consists in a web-based visualisation tool at https://svalbard.insar.no/ (release date: 2 February 2026, last access: 22 September 2026). The products are also distributed at https://doi.org/10.5281/zenodo.18442696 (Bredal et al., 2026a). InSAR Svalbard establishes a foundation for geohazard assessment in Arctic regions and interdisciplinary research on permafrost dynamics, ground stability, and environmental changes.
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Aspaas, Andreas Grøvan; Bievre, Grégory; Lacroix, Pascal; Langet, Nadege; Aga, Juditha & Skrede, Ingrid
[Vis alle 9 forfattere av denne artikkelen]
(2026).
Seasonal and inter-annual evolution of the deformation of two Arctic landslides.
Earth Surface Dynamics.
ISSN 2196-6311.
14(5),
s. 729–761.
doi:
10.5194/esurf-14-729-2026.
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Landslides in glacial and periglacial environments are increasingly affected by climate change, with sudden failures reported in high mountain regions and the Arctic. The complex mechanisms behind these events are often poorly understood due to a lack of dense in situ data. We investigate two slow-moving landslides in Arctic Norway (70° N), the Jettan and Gámanjunni landslides, located approximately 10 km apart: Jettan, a complex slide in micaschist and calcite marble situated below the permafrost boundary, and Gámanjunni, a rotational slide in micaschist situated above the permafrost boundary. Using over a decade of multi-physics observations, including geodetic, borehole, seismic, and hydrological data, we examine surface and subsurface deformation. Both landslides display similar seasonal surface velocity patterns, with peaks in spring and autumn, likely influenced by pore-water infiltration. At Jettan, twelve years of inclinometer data in boreholes reveal a transition from steady state to seasonal deformation in two shear zones. Since 2020, spring accelerations have intensified in years coinciding with deeper snowpacks and associated melt. These observations, together with statistical modeling, suggest that the shear-zones are becoming increasingly localized and sensitive to pore-water pressure. Conversely, autumn acceleration is not seen in localized shear zones but manifests as distributed volumetric deformation. Seismic velocity variations within the landslide body also exhibit seasonal patterns that correspond with geodetic velocity, interpreted as changes in landslide rigidity due to water infiltration. This integrated analysis of surface and subsurface data offers new insights into the evolving deformation of Arctic landslides, emphasizing the influence of hydrological forcings on both seasonal and long-term deformation processes.
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Kierulf, Halfdan Pascal; Maria, Kern, Lisa; Conrad, Clinton Phillips; Kirkvik, Ann-Silje; Hana, Krásná, & Moholdt, Geir
[Vis alle 7 forfattere av denne artikkelen]
(2026).
Effects of glacial loading in Svalbard on the VLBI scale realisation.
Journal of Geodesy.
ISSN 0949-7714.
100.
doi:
10.1007/s00190-026-02121-1.
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In the realisation of the International Terrestrial Reference System in 2000, and in the realisations since 2008, the scale of the International Terrestrial Reference Frame (ITRF) has been defined based on Very Long Baseline Interferometry (VLBI) and Satellite Laser Ranging (SLR) solutions, whereas ITRF2005 relied solely on VLBI. In the latest ITRF realisation, i.e. ITRF2020 with its first and second updates, VLBI sessions after September 2013 are excluded from the ITRF scale definition due to a detected drift in the VLBI solution with respect to the average scale trend computed from September 1997 until September 2013. Ny-Ålesund station in Svalbard, the northernmost fundamental geodetic station hosting all major techniques, plays a key role in ITRS realisation due to its location. Crustal motion measurements at Ny-Ålesund reveal nonlinear vertical motion, largely explained by elastic deformation caused by thinning glaciers. In the ITRF2020 updates (u2023 and u2024), a discontinuity in August 2016 was introduced for the VLBI station to account for the increasing uplift, reducing the detected scale drift relative to ITRF2020 by approximately 50%. In this study, we analyse the nonlinear vertical motion at Ny-Ålesund, compare it with predicted elastic loading signals arising from glacier thinning, and assess its impact on the VLBI scale estimates. Over the past 25 years, the land uplift rate increased from about 6 mm/year to 14 mm/year, indicating that the vertical displacement through time is not well described by a constant-rate model. The record also shows substantial interannual variability, of which the glacier loading model explains only about 50%. Including a nonlinear station motion model—based on Global Navigation Satellite System (GNSS) observations or loading predictions—for the VLBI station in Ny-Ålesund reduces the relative scale drift by 30–60%. Finally, we discuss alternative approaches to mitigate the negative effects of nonlinearity, such as modelling the elastic glacier signal or better integrating VLBI station motion with GNSS-derived displacement.
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Sereinig, L. & Herbort, O.
(2026).
SCoRE: The surface composition of rocky exoplanets.
Astronomy and Astrophysics (A & A).
ISSN 0004-6361.
713,
s. 323–323.
doi:
10.1051/0004-6361/202659706.
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Context. The crust composition of rocky exoplanets with a substantial atmosphere cannot be observed directly. However, recent developments are starting to allow for the observation and characterisation of their atmospheres. Understanding the link between atmospheres and crusts could allow for constraints on the crusts’ composition based on atmospheric observations. Aims. We aim to understand the link between the thermal stability of specific condensates and atmospheric compositions. This allows constraints on the mineralogical composition of the surface by potentially observable atmospheric features. In order to achieve this, a grid study of atmospheric and crustal compositions is conducted. Methods. We use a diverse range of total element abundances inspired by various rock compositions as the compositional base for our crust-atmosphere models, for which thermo-chemical and phase equilibrium is assumed. In this work, we investigate a temperature range of 500K to 1000 K and a surface pressure of 1 bar. The resulting atmospheric compositions are classified using atmospheric types based on the most abundant gas-phase elements C, H, N, O, and S. Results. Some of the changes in surface mineralogy coincide with changes in atmospheric type, independent of the given total elemental abundances. In total, a link has been revealed between 23 thermally stable minerals and their corresponding atmospheric types, which is independent of the ratio of the refractory elements present. Especially, the sulphur chemistry of the minerals and the average iron oxidation state can be constrained by the corresponding atmospheric type.
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Giannicor, Guido M.; Gianni, Conrado; Gallo, Leandro C.; Sippl, Christian; Arvizu, Harim & Ramos, Victor
(2026).
Mid-ocean ridge extinctions as amplifiers of plate-tectonic change.
Earth-Science Reviews.
ISSN 0012-8252.
s. 105685–105685.
doi:
10.1016/j.earscirev.2026.105685.
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Plate-tectonic reorganizations involve rapid shifts in plate motions, boundary forces, and tectonic regimes, yet the role of mid-ocean ridge extinctions (MOREs) remains unclear. Here we show that MOREs can amplify reorganizations by removing divergent boundaries, coupling formerly independent plate domains, and enabling stress transmission across extinct ridges. We illustrate this mechanism through four Cenozoic examples closely associated with plate reorganizations: the Wharton, Pacific–Farallon, Shikoku, and Sandra–Malpelo ridges. These cases indicate that, when extinct ridges are incorporated into larger plate circuits undergoing reorganization, they can transmit stresses generated elsewhere in the network toward neighboring margins, consistent with cascading plate-to-plate reorganizations. Strength-profile calculations show that substantial post-MORE strengthening can develop within a few million years after extinction. However, the early coupling inferred from the natural examples is best explained if this strengthening acts on ridge systems already mechanically preconditioned before shutdown, particularly by terminal slow- to ultraslow-spreading that produces a relatively thick axial brittle lithosphere. We therefore propose that inherited preconditioning enables early stress transmission, while subsequent thermo-mechanical strengthening progressively consolidates the extinct boundary. MOREs thus represent evolving mechanical structures that influence how plate-boundary forces are transmitted during plate-network reorganization.
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Galland, Olivier; Chiacchiera, Sabina; Cal, Hernán de la; Jerram, Dougal Alexander; Lombardo, Ezequiel & Palma, J. Octavio
[Vis alle 12 forfattere av denne artikkelen]
(2026).
The impacts of volcanism on hydrocarbon-bearing sedimentary basins - Examples from the world-class Neuquén Basin case study, Argentina.
Global and Planetary Change.
ISSN 0921-8181.
257.
doi:
10.1016/j.gloplacha.2025.105218.
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The last two decades of research have highlighted that volcanism occurring in sedimentary basins can have substantial effects on sedimentary formations. In particular, igneous intrusions can trigger the generation of large amounts of greenhouse gases in organic-rich host rocks, leading to dramatic climate change and mass extinctions. Volcanism can also have significant impacts on hydrocarbon-bearing sedimentary basins. The Neuquén Basin, Argentina, is a well-studied example of a hydrocarbon-producing sedimentary basin hosting massive volcanism. The combination of substantial industry subsurface data and high-quality outcrops makes the Neuquén Basin an exceptional geological object to study magma-sedimentary rock interactions and their implications to hydrocarbon systems. This contribution reviews well-studied examples from the Neuquén Basin that illustrate: (1) thermal effects of sills on maturation of the organic matter of the source rock, (2) fracturing processes in igneous intrusions and the host rock, (3) sills as producing fractured reservoirs, (4) intrusion-induced doming as structural trap or as potential fractured reservoir, (5) fluid migration along igneous intrusions, (6) reservoir compartmentalization induced by dykes, (7) generation of bitumen dykes in vicinity of intrusions, and (8) improvement of geophysical imaging using large-scale outcrops.
All in all, our review documents various effects of magma-rock interactions in hydrocarbon-bearing sedimentary basins, and highlights the significant scientific value of the Neuquén Basin as a world-class case study for unravelling processes of magma-rock interactions in hydrocarbon-bearing sedimentary basins.
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Biswas, Uddalak; Galland, Olivier & Carlson, Andreas
(2026).
Laponite® RD and hydroxyethyl cellulose as host rock and magma analogue to simulate a wide range of rheological combinations in the volcanic plumbing system.
Tectonophysics.
ISSN 0040-1951.
937.
doi:
10.1016/j.tecto.2026.231351.
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Analogue modelling is essential for understanding magma emplacement in the Earth’s crust and requires strict geometric, kinematic and dynamic scaling. Therefore, material selection must satisfy the scaling laws to reproduce the natural rheological variability. Although often represented by end-member rheologies, crustal rocks in nature exhibit complex rheological behaviour. In this study, we analysed two complex materials, Laponite® RD (LRD) and hydroxyethyl cellulose (HEC), to assess their effectiveness as geological analogues for country rock and magma in dyke emplacement experiments. We provide a detailed characterisation of LRD, highlighting its tuneable rheological properties via curing time (t_c). To characterise the complex rheology of the LRD gels, rotational and oscillatory tests, including flow, amplitude, frequency sweep, and creep and recovery tests, were performed at curing times (t_c) ranging from 30 to 240 min. We tested the rheology of aqueous HEC solutions at concentrations of 0.50, 0.75, and 1.00 wt%. Additionally, this study highlights the significant role of surface tension in laboratory analogue experiments, demonstrating the need to minimise interfacial tension by selecting an appropriate magma analogue fluid when using a viscoelastic host. The rheological test results showed that the storage modulus (G^') and yield stress (τ_y) increased systematically with increasing t_c. The flow and surface tension test results indicate that HEC hydrous solutions serve as robust magma analogues, offering variable viscosities with minimal alterations in surface tension and density. Combining the rheological analysis results of LRD and HEC, we propose a new methodology for simulating a wide range of rheological conditions by systematically varying the LRD curing time and employing different concentrations of HEC as a magma analogue. Our approach emphasises precise rheological characterisation together with control of magma-analogue density and surface tension, minimising the interfacial tension and buoyancy contrast with the host for accurate scaling in analogue models of volcanic plumbing systems.
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Kwafo, Samuel; Meert, Joseph G.; Pandit, Manoj K.; Sinha, Anup K. & Verma, Nirmal Kant
(2026).
Searching for the age of the upper Vindhyan basin, India: A view from paleomagnetism and geochronology.
Geoscience Frontiers (GSF).
ISSN 1674-9871.
17(1).
doi:
10.1016/j.gsf.2025.102168.
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The closure age of the Proterozoic Vindhyan basin is a long-standing puzzle, unresolved due to inconsistencies between paleontological, geochronological, and paleomagnetic data. Some fossil findings from the Upper Vindhyan basin suggest an Ediacaran closure age, Pb-Pb dating of carbonate units yield dates ranging from ∼750–910 Ma, and detrital zircon data generally support a Kleisian (800–1000 Ma) closure age. In this study, we review published detrital zircon data and apply a statistically robust method to estimate the maximum depositional age (MDA) of the upper Vindhyan Kaimur, Bhander, and Rewa groups. Additionally, we present new paleomagnetic data from the folded Bhander sandstones near the Great Boundary fault to establish the primary nature of the Bhander-Rewa paleomagnetic pole. Our analysis reveals an MDA of 945 ± 7 Ma, which aligns closely with the youngest zircon population in the spectra. This MDA also corresponds to the onset of the Delhi Orogeny to the west of the Vindhyan basin; collisional orogenesis in the Central Indian Tectonic Zone to the south; and more distal high-grade metamorphism and collisional tectonism in the northern Eastern Ghats belt providing a geologically meaningful context for the basin closure age. Our paleomagnetic data offers a robust field test for the Vindhyan pole and we demonstrate that proposals for terminal Tonian closure of the basin (∼850–770 Ma) are incompatible with extant paleomagnetic data from India.
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Yi, Zhiyu; Huang, Ziyu; Yang, Silin; Wang, Fei; Meert, Joseph G. & Zhao, Qian
[Vis alle 8 forfattere av denne artikkelen]
(2026).
Testing the Pangean mega-monsoon hypothesis: New insights from a Late Triassic climatic record from the Zigui Basin, South China.
Palaeogeography, Palaeoclimatology, Palaeoecology.
ISSN 0031-0182.
693,
s. 113807–113807.
doi:
10.1016/j.palaeo.2026.113807.
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Two end-member climate models, the mega-monsoon and the zonal climate pattern, offer competing explanations for the climate of Pangea. Climatic records serve as direct proxies for evaluating these models. This study presents isotopic age and paleoclimatic data from a Late Triassic sequence in the Zigui Basin, South China, to elucidate environmental changes in East Asia and test the climatic models. Multi-proxy records indicate a significant climatic shift from arid to humid conditions within the upper Badong Formation. Usingle bondPb dating of a carbonate layer directly above this climatic transition yields an age of 224.6 ± 5.6 Ma, postdating the Carnian Pluvial Episode. Comparison of the Triassic climatic records across East Asia reveals diachronous humidification. The prolonged aridity in the South China Block (SCB) during the Early to Middle Triassic, coupled with an earlier onset of humidification in the North China Block relative to the SCB, challenges the Pangean mega-monsoon hypothesis.
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Meert, Joseph G.; Pandit, Manoj K.; Sinha, Anup K.; Kwafo, Samuel; Williams, Megan & Panigrahi, Bhagirathi
[Vis alle 10 forfattere av denne artikkelen]
(2026).
Quarter century of Indian Precambrian paleomagnetism: The assembly of Peninsular India and its role in proterozoic supercontinents.
Earth-Science Reviews.
ISSN 0012-8252.
281.
doi:
10.1016/j.earscirev.2026.105600.
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Over the past 25 years, Precambrian paleomagnetic research in Peninsular India has grown significantly. The quality of data from these studies has improved markedly, resulting in more than a dozen highly reliable paleomagnetic poles from the five cratonic nuclei and the platformal successions that overlie them. This paper provides a comprehensive, site-by-site review of the published paleomagnetic record from the region, including corrections to earlier studies, most of which involve clerical errors in the original publications. In addition, we present previously unpublished paleomagnetic results from the Semri Group (Vindhyan Basin) as well as select new data from the Bastar Craton. Despite these advancements, significant challenges remain, primarily due to poor age constraints within the sedimentary sequences. Numerous paleomagnetic poles from India indicate anomalously high paleolatitudes, particularly from carbonate rocks across six major basins, suggesting widespread remagnetization or unusual climatic conditions. India’s position within Rodinia and Columbia remains uncertain, with existing paleomagnetic data conflicting with recent models. Tonian paleomagnetic data from India and South China suggest a possible linkage between the two regions independent of Rodinia and were interpreted as recording a large-scale episode of true polar wander between ca. 0.82 and 0.77 Ga.
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Hellevang, Helge; Nooraiepour, Mohammad; Sednev-Lugovets, Anton & Dziadkowiec, Joanna
(2026).
Crystal Growth in Porous Media.
InterPore Journal.
3(3).
doi:
10.69631/9kd53x06.
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Crystalline silicate minerals and carbonates make up 90% to 95% of the Earth's lithosphere, the rigid outermost shell comprising the crust and uppermost solid mantle. Crystalline materials are continuously modified by fluid–rock interactions including crystal growth occurring along fractures and within pore spaces. Crystals form under conditions dictated by extrinsic factors, such as temperature, pressure, fluid composition, and pore confinement, as well as intrinsic factors such as crystal structure, chemical bonding, and anisotropy. While the thermodynamic stability and structure of crystals are well established, their rates of heterogeneous nucleation and growth remain poorly constrained. This is particularly true in porous media, where nucleation is frequently a distinct and rate-limiting step rather than a negligible precursor to growth, especially where non-classical pathways preclude a single, well-defined interfacial free energy.
In this commentary, we outline how crystal nucleation and growth in porous media control pore-scale structure, flow, and transport, and we evaluate how these processes can be represented in numerical models across scales. We examine the distinct roles of nucleation pathways, growth kinetics, interfacial and confinement effects, and crystallization pressure in governing transient porosity, stress localization, and self-organized crystalline networks. Furthermore, we discuss how fluid flow and mixing modulate where and when these processes occur. These principles are illustrated through examples spanning well-controlled synthetic crystal growth in materials science to geo-energy and geoscience applications, such as basaltic CO2 mineralization, where probabilistic nucleation, reactive transport, and evolving pore architecture jointly control macroscopic behavior.
Finally, we assess the potential of machine learning and surrogate modeling approaches to bridge the persistent gap between molecular-scale mechanisms and field-scale predictions. By emphasizing mechanistic understanding over system-specific details, our goal is to help porous media scientists judge when crystallization is likely to matter, and to guide the selection of modeling approaches that remain both physically grounded and computationally tractable.
WHY THIS PAPER MATTERS
Crystal nucleation and growth can progressively clog pore spaces, redirect fluid pathways, and transform the mechanical and transport behavior of porous rocks across scales. Is it possible to use information we have about nanoscale processes to predict reservoir-scale changes? This InterPore Commentary article synthesizes how confinement, interfacial free energies, and crystallization pressures control where crystals appear, how fast they grow, and when they damage or seal flow networks in natural and engineered systems. It then outlines how machine learning can be used to connect molecular, pore, and field scales for predictive modeling.
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Virkkala, Anna-Maria; Wargowsky, Isabel; Vogt, Judith; Kuhn, McKenzie A.; Madaan, Simran & Windholz, Tiffany
[Vis alle 269 forfattere av denne artikkelen]
(2026).
ABCFlux v2: Arctic–boreal CO2 and CH4 monthly flux observations and ancillary information across terrestrial and freshwater ecosystems.
Earth System Science Data.
ISSN 1866-3508.
18(9),
s. 6357–6409.
doi:
10.5194/essd-18-6357-2026.
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Measurements of surface-atmosphere carbon dioxide (CO 2 ) and methane (CH 4 ) fluxes have been relatively sparse across the Arctic tundra and boreal biomes, causing significant uncertainties in carbon budget estimates from the region. While the availability of Arctic-boreal carbon flux data has increased substantially over the past decade, the data have remained spread across different repositories, scientific articles, and unpublished sources, making it difficult to leverage. Here we present a new dataset of monthly Arctic-boreal carbon fluxes (ABCFlux v2) across terrestrial (wetlands and uplands) and freshwater (lakes and rivers) ecosystems compiled from previous syntheses including the Arctic-boreal CO 2 flux database (ABCFlux v1), the Boreal-Arctic Wetland and Lake Methane Dataset (BAWLD-CH4), and the Global River Methane Database (GRiMeDB). In addition, we consider data from general-purpose (e.g., Zenodo) and flux network repositories, literature, and site principal investigators. The dataset includes surface-atmosphere CO 2 fluxes of gross primary production (GPP), ecosystem respiration (Reco), and net ecosystem exchange (NEE), alongside CH 4 fluxes. For aquatic ecosystems, we split CH 4 fluxes into diffusive and ebullitive flux pathways, and included potential emissions from transient storage in the water column (“storage fluxes”), alongside CO 2 and CH 4 concentrations dissolved in the surface water. Fluxes are measured through a variety of methods including chamber and eddy covariance techniques alongside bubble traps, ice-surveys, and concentration-based turbulence-driven modelling in aquatic ecosystems. The monthly flux data are reported together with supporting methodological and environmental metadata. The resulting ABCFlux v2 has 23 847 flux site-months, 8182 concentration site-months, and 199 seasonal observations from 1024 sites, and includes 56 139 reported fluxes (i.e. sum of GPP, Reco, NEE, and CH 4 fluxes) from the years 1984 to 2024. The majority of monthly observations occurred after 1999. Wetlands had the highest number of site-month observations (8758), followed by boreal forest (6981), lotic ecosystems (6275), lentic ecosystems (3799) and upland tundra (3308). Measurements of CO 2 dominated the dataset across most ecosystem types (25 222) except for lentic ecosystems, where CH 4 flux site-months (3098) were more frequent than CO 2 flux site-months (2915). Overall, ABCFlux v2 includes 160 % more site-months for terrestrial CO 2 flux data compared to ABCFlux v1. Integrating and updating BAWLD-CH4 flux data from growing season averages to monthly fluxes resulted in 5671 site-months of chamber CH 4 data compared to 762 site-years. This collaborative initiative, involving contributions from over 260 researchers, provides a comprehensive overview of the current state of the Arctic-boreal carbon flux network and its data, and serves as an important step in reducing uncertainties in Arctic-boreal carbon budgets and in enhancing our understanding of climate feedbacks. The data can be accessed at ORNL DAAC at https://doi.org/10.3334/ORNLDAAC/2448 (Virkkala et al., 2026).
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Dar, Shaakir; Silantyeva, Olga; Ala-aho, Pertti; Walter, Benjamin; Hulth, John & Hyöky, Valtteri
[Vis alle 8 forfattere av denne artikkelen]
(2026).
Snow Structure Modulates the Isotopic Imprint of Sublimation.
EGUsphere.
doi:
10.5194/egusphere-2026-2589.
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Abstract. Sublimation modifies the stable isotopic composition of snow. The physical controls governing this imprint, particularly the interplay between isotopic fractionation, snow structure, and airflow, remain poorly constrained. Current surface-exchange models commonly treat sublimation fractionation as a function of atmospheric forcing and boundary-layer exchange, with limited explicit representation of snow structural state. Here, we present controlled wind-tunnel experiments examining sublimation-driven isotopic changes (δ¹⁸O, δ²H, and d-excess) in three contrasting snow types (laboratory snow, fresh natural snow, and old natural snow) under varied airflow regimes, ambient humidity, and basal-to-air temperature contrasts. We show that airflow is the dominant experimental control on sublimation mass loss, but bulk isotopic change does not scale directly with mass loss, revealing a partial decoupling between sublimation magnitude and isotopic modification. High airflow produced the smallest isotopic change per unit mass loss, consistent with strong turbulent exchange reducing the isotopic imprint of sublimation. However, absolute isotopic change varied systematically with snow structural state, scaling strongly with bulk porosity in natural snow. This structural dependence weakened after mass normalization for δ¹⁸O and δ²H, but persisted for d-excess, suggesting that properties associated with porosity influence effective kinetic fractionation in addition to cumulative isotopic change. Laboratory snow deviated from this behavior: despite overlapping the porosity range of natural snow, it showed no porosity-isotopic change relationship. This suggests that bulk porosity alone is insufficient to capture the structural controls on isotopic response to sublimation. Within a relative snow-type comparison, the Craig–Gordon model systematically overpredicted δ¹⁸O and δ²H enrichment and underpredicted the range of d-excess change. The systematic nature of these discrepancies suggests that parameter uncertainty alone is unlikely to explain the mismatch and points to missing representation of internal vapor transport through the snow pore network. Our study shows that sublimation rate alone is insufficient to predict isotopic modification; snow structural state must be considered alongside atmospheric forcing in models of sublimation-driven isotopic evolution. Snow structural state can therefore impose a systematic overprint on isotopic signals in snow archives and meltwater that structure-independent models are likely to misrepresent.
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Figowy, Sarah; Caracas, Razvan & Avice, Guillaume
(2026).
Retention of noble gases in the deep Earth: Kinetic trapping or stable bonding?
Science Advances.
12(33).
doi:
10.1126/sciadv.aee3254.
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The bonding potential of noble gases in high-pressure silica-bearing solids and melts remains debated, yet it is a central question for understanding their retention behavior and evaluating the role of silicate-bearing phases in the transport and storage of noble gases originally present in the atmosphere. Here, we assess the chemical behavior of noble gases in three silicates: quartz, seifertite, and perovskite. Using the electron localization function and Bader charge analysis, we find no evidence of stable covalent or ionicbonding. The very slow intracrystalline diffusion of heavy noble gases governs their trapping in silicates during crystal growth. Noble gases are more likely to reside in melts or grain boundaries than in silicate crystal lattices.
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Stoutenburg, Emma R.; Caracas, Razvan & Campbell, Andrew J.
(2026).
Immiscibility between hydrogen and molten iron in planetary cores.
Earth and Planetary Science Letters.
ISSN 0012-821X.
678,
s. 119851–119851.
doi:
10.1016/j.epsl.2026.119851.
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Hydrogen is a likely light element candidate in planetary cores. A hydrogen solubility limit in molten iron could determine the maximum amount of hydrogen possible in the core of a rocky planet. Here, we use ab initio molecular dynamics to investigate the liquid iron-hydrogen system at 10, 50, and 136 GPa and at high temperatures where iron is molten. We calculate Gibbs free energy of mixing at several compositions, from pure iron to hydrogen, using thermodynamic integration. We find that at 10 GPa and 3000 K, there is a liquid-liquid miscibility gap; iron and hydrogen unmix to form Fe0.34H0.66 and H2. At 50 GPa, >2500 K and at 136 GPa, >3500 K, the melts are fully miscible. We extrapolate the Gibbs free energy of mixing to estimate the iron-hydrogen phase diagram down to 1 GPa and in the 1500–6000 K temperature range. As pressure increases, the liquid-liquid miscibility gap shrinks: the solubility limit of hydrogen in liquid iron increases and the closure temperature decreases. At 1 GPa, we estimate the solubility is 18 at% (0.38 wt%) hydrogen at 1500 K. The gap has completely closed by 38 GPa and 3000 K, 69 GPa and 2000 K, and 94 GPa and 1500 K. Thus, small bodies like moons, planetesimals, Mercury, and Mars, which have core-mantle boundary pressures under 30 GPa, are the most limited in the amount of hydrogen their cores can accommodate. On the other hand, iron and hydrogen are fully miscible at the core conditions of larger planets like Earth, Venus, super-Earths, and sub-Neptunes, so their hydrogen concentrations will be limited by sources during formation rather than a thermodynamic limit.
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Okuda, Yoshiyuki; Ohta, Kenji; Mohn, Chris Erik; Nishihara, Yu; Takaichi, Goru & Kawaguchi-Imada, Saori
[Vis alle 8 forfattere av denne artikkelen]
(2026).
Geophysical evidence of a nearly dry bridgmanite in the Earth’s lower mantle.
Nature Communications.
17.
doi:
10.1038/s41467-026-76621-1.
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Water in Earth’s mantle plays a crucial role in shaping geological and geochemical processes. While previous electrical conductivity measurements on major mantle minerals have constrained water content in the Earth’s mantle down to the mantle transition zone, the water content of the lower mantle remains experimentally unconstrained. This study measures the electrical conductivity of hydrous (Fe,Al)-bearing bridgmanite, synthesized with Fe and Al compositions representative of peridotitic lithology, at pressures up to 47 GPa and temperatures up to 2210 K. The results demonstrate that proton conduction is the predominant charge transport mechanism in hydrous (Fe,Al)-bearing bridgmanite under the investigated pressure-temperature conditions. Water incorporation markedly enhances the electrical conductivity of bridgmanite, increasing it by approximately an order of magnitude relative to that of dry samples. Extrapolation of the experimental data suggests that bridgmanite in the lower mantle contains less than 40–70 wt. ppm H 2 O near the top and at mid-mantle depths. These findings offer insight into potential hidden water reservoirs in Earth’s lower mantle.
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Backhouse, Nicholas; Thomson, Andrew; Brodholt, John Peter; Hrubiak, Rostislav; Crichton, Wilson & Hao, Ming
[Vis alle 9 forfattere av denne artikkelen]
(2026).
Seismic Velocity of Chlorite Under High Pressure and Temperature and Implications for the Lesser Antilles Subduction Zone.
Journal of Geophysical Research (JGR): Solid Earth.
ISSN 2169-9313.
131(9),
s. 1–13.
doi:
10.1029/2025jb032997.
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Abstract Chlorite is thought to be one of the major water‐carrying phases in subduction zones, both within the slab and in the mantle wedge. Its presence has previously been linked to common seismological observations at subduction zones, including P and S wave anisotropy as well as high V P / V S ratios (>1.8) in the mantle wedge. However, at present, there are very few high pressure and temperature measurements of the seismic velocity of chlorite at subduction zone conditions, hampering accurate seismological interpretations. This study presents seismic velocities and PVT equation of state measurements of two natural monomineralic chlorite schists, at conditions extending up to ∼5 GPa and 773K. One major finding is the anomalously high V P / V S ratio of these samples, which increase >3 at 5 GPa and 773 K. This result suggests that only a small amount of chlorite (<10%) is required in mantle peridotite assemblages to reproduce the observed V P / V S anomalies >1.8, such as those in the Lesser Antilles subduction zone, and that regions with high V P / V S are not necessarily diagnostic of a free fluid.
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Senger, Kim; Ammerlaan, Fenna; Betlem, Peter; Gaina, Carmen; Galland, Olivier & Grundvåg, Sten-Andreas
[Vis alle 21 forfattere av denne artikkelen]
(2026).
A Field Guide to the High Arctic Large Igneous Province in and Around Isfjorden, Svalbard.
Tektonika.
3(2),
s. 176–216.
doi:
https:/tektonika.online/index.php/home/article/view/124/197.
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The High Arctic Large Igneous Province (HALIP) is a major tectono-magmatic element that affected large parts of the Arctic during the Cretaceous (magmatism occurred from 126
to 78 million years ago [Ma]). In Svalbard, HALIP intrusive and extrusive rocks are grouped and classified as the Diabasodden Suite. Sills and dykes are present throughout Svalbard, emplaced in units stratigraphically ranging from crystalline basement to Jurassic-Cretaceous siliciclastics. Time-equivalent lava flows are exposed on Kong Karls Land in eastern Svalbard. In this contribution, we firstly define and introduce major features of the circum-Arctic HALIP. Secondly, we zoom into Svalbard where we document and summarize the attributes of HALIP outcrops (i.e., the Diabasodden Suite) located in and around Isfjorden, the most accessible location that is reachable on day trips using boats from Longyearbyen. For each of the 15 sites we focus on specific aspects of HALIP characterization, including geochronology, geochemistry and geometry of volcanic and intrusive rocks. We complement field descriptions of the sites with digital geoscientific data, including digital outcrop models and photospheres. Finally, we synthesize the Isfjorden study area in the context of data and knowledge gaps for the HALIP in general. We hope that this contribution will stimulate further HALIP research in Isfjorden and beyond.
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Saha, Chitradeep; Owens, Mathew; Lockwood, Mike; Barnard, Luke; Brehm, Nicolas & Dalla, Silvia
[Vis alle 9 forfattere av denne artikkelen]
(2026).
Physics-Constrained Reconstructions of Sunspot Number from Millennial-Scale Annual Heliospheric Modulation Potential.
Solar Physics.
ISSN 0038-0938.
301(9).
doi:
10.1007/s11207-026-02731-0.
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Abstract Long-term solar magnetic variability governs the space climate conditions. These variations also modulate the galactic cosmic ray influx reaching Earth and subsequently regulate the production of cosmogenic isotopes in Earth’s atmosphere. By harnessing the multi-millennial records of the abundances of these radio-isotopes stored in natural terrestrial reservoirs, such as tree wood and ice sheets, it is possible to reconstruct past solar magnetic activity predating the telescopic era. However, existing regression-based reconstruction methods using isotope data from time series extracted from the reservoirs are often applied to conditions outside the valid parameter range. This can result in a number of problems, including negative sunspot numbers during low solar activity phases, which correspond to statistically permissible extrapolation artefacts but have no physical meaning. To address this, we developed a Monte-Carlo inversion framework consisting of a sequence of physics-based semi-empirical forward models, supplemented by an Approximate Bayesian Computation-based posterior selection, to infer the most plausible temporal evolution of solar magnetic parameters. Our approach produces physically consistent, uncertainty-quantified reconstructions of annually resolved parameters, including sunspot numbers. We apply the method to two modulation potential datasets, namely geomagnetic record from 1845 – 2020, and an annual 14 C estimate over the period 971 – 1932. Our new reconstruction method is designed to yield strictly non-negative sunspot numbers and shows close agreement with direct observations within uncertainty during the telescopic era. These results offer valuable insights into long-term solar variability and provide improved constraints for long-term solar dynamo modelling. The annual-scale reconstructions are also directly usable for solar irradiance estimation, terrestrial climate modelling, and studies of long-term Sun-Earth coupling.
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Zhang, Yiming; Swanson‐Hysell, Nicholas L.; Domeier, Mathew Michael; Gallo, Leandro; Sapienza, Facundo & Afanador, Diego Alberto Osorio
(2026).
Enriching Paleogeographic Reconstruction Through the Integration of Bayesian Age Models Into Site‐Based Apparent Polar Wander Paths.
Journal of Geophysical Research (JGR): Solid Earth.
ISSN 2169-9313.
131(9).
doi:
10.1029/2026jb034561.
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Apparent polar wander paths (APWPs) synthesized from paleomagnetic data are foundational to our understanding of the long‐term motions of lithospheric plates. Recent progress has highlighted the advantages of developing such paths from paleomagnetic sites that provide individual snapshots of the ancient geomagnetic field. This approach contrasts with traditional methods that rely on study‐level mean poles—through which it is challenging to incorporate positional and temporal uncertainty. A benefit of the site‐based approach is the flexibility in incorporating temporal information. Rather than relying on a single age assigned to a mean paleomagnetic pole that groups sites together, varied ages can be assigned to individual sites. It also allows the incorporation of stratigraphic superposition constraints, which would otherwise be discarded. We show how probabilistic stratigraphic age models can be integrated into the development of site‐based APWPs. Through resampling from the posterior distributions of such age models, temporal uncertainty can be incorporated while honoring stratigraphic superposition. We illustrate this approach using volcanic and sedimentary successions with U‐Pb age constraints from the late Mesoproterozoic Midcontinent Rift of North America combined with contemporaneous lavas and intrusions from southwestern Laurentia. The result is a site‐based APWP of the Keweenawan Track with significantly higher temporal resolution than a traditional running mean. The high‐resolution path gives insights into motion rates and constrains the timing of change in path direction without requiring additional assumptions. This framework demonstrates how probabilistic treatment of age and positional uncertainties can strengthen quantitative tests of tectonic models.
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Escartín, Javier; Sautter, Benjamin; Gaina, Carmen; Granot, Roi; Petersen, Sven & Pubellier, Manuel
(2026).
Global geometry of mid-ocean and back-arc ridge systems: Ridge segments, transform faults, and non-transform offsets.
Earth-Science Reviews.
ISSN 0012-8252.
281,
s. 105633–105633.
doi:
10.1016/j.earscirev.2026.105633.
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The total length of the global mid-ocean ridge system length is currently estimated at 50000 to 100000 km. To define in detail the complex structure of divergent plate boundaries, and to accurately evaluate its length and the geometry of ridge offsets, we present the MAPRIDGES database. It provides the first comprehensive global compilation of mid-ocean ridge geometry interpreted from multibeam bathymetry, encompassing in detail individual ridge segments, transform faults, and non-transform offsets (NTOs). The database includes 262 transform faults and 10 transform zones, totalling ∼28.000 km. We quantify for the first time both overlapping and underlapping NTOs at divergent plate boundaries and find a cumulative lateral offset of ∼9.000 km, representing one-third of the cumulative length of transform offsets. The database incorporates 1471 ridge segments reaching a total length of ∼71200 km, while the global ridge length corrected for NTOs overlaps and underlaps amounts to ∼67900 km.
Mid-ocean ridge spreading rate exerts a first-order control on the geometry and nature of mid-ocean ridge segmentation. We document that at rates below a spreading rate threshold of ∼80-100 mm/yr, the proportion of overlapping NTOs increases with spreading rate, while the cumulative lateral offset decreases. At rates above this spreading rate threshold there is no apparent dependence of NTOs geometry on spreading rate. We also document that the lateral offset of NTOs and transforms show a significant overlap, with numerous transforms displaying offset lengths below 40 km, and NTOs exceeding 50 km. NTOs affect about 10% of the oceanic crust along-axis, reshaping the lithosphere with tectonic deformation, volcanism, hydrothermal activity and alteration. Consequently, these non-transform discontinuities, together with transform faults, should be systematically included in global assessments of lithospheric accretion, alteration, and associated fluxes of fluids and elements at mid-ocean ridges. We suggest that ridge segmentation and the nature of discontinuities are influenced by multiple factors beyond spreading rate, including mantle temperature, melt supply, and ridge obliquity, in addition to local intra- and inter-segment variability. Analyses of the patterns reported here might help understanding the nature and evolution of magmatic vs. tectonic-dominated ridge segments and their terminations.
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Pharaoh, Tim C.; Rushton, Jeremy; Condon, Dan; Chenery, Simon; Horstwood, Matt & Sahy, Diana
[Vis alle 12 forfattere av denne artikkelen]
(2026).
The Wash Igneous Complex of eastern England: A candidate Avalonian source for Sandbian tephra in Baltoscandia and implications for closure of the Tornquist Sea.
Geological Society of America Bulletin.
ISSN 0016-7606.
doi:
10.1130/b38831.1.
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The Wash Igneous Complex (WIC) is a component of a Sandbian (Late Ordovician) calc-alkaline magmatic arc that extends from the Lake District in northern England to the Brabant Massif of Belgium, associated with fast subduction of Tornquist ocean crust separating Avalonia (upper plate) and Baltica (lower plate). Buried beneath the East Midlands and The Wash of eastern England, the WIC is likely to comprise an extensive nested caldera system, underlain by a granite batholith, inferred from geophysical data. New whole-rock geochemical data confirm the calc-alkaline character of the WIC and elucidate relationships with other calc-alkaline magmatic complexes in eastern England. Detailed petrographic and geophysical data indicate that the WIC had the capacity to generate super-eruptions. Evidence for ultraplinian volcanism comes from contemporary, regionally distributed and thick metabentonite tephra in Baltoscandia. New, high-precision U-Pb isotopic (chemical abrasion−isotope dilution−thermal ionization mass spectrometry; CA-ID-TIMS) ages of 454.45 ± 0.13/0.23/0.54 Ma and 454.40 ± 0.11/0.22/0.53 Ma (2σ, Sandbian, Late Ordovician) are reported for zircons from a heterolithic dacitic tuff-breccia and a subvolcanic microgranite respectively, recovered from two deep boreholes that intersect the WIC. These dates are identical, within their analytical uncertainties, with equivalently high-precision U-Pb zircon dates for the Kinnekulle Metabentonite (KKMB; Baltoscandia). A population of younger grains from the breccia yielding a CA-ID-TIMS age of 453.70 ± 0.17/0.26/0.55 Ma (2σ) may correlate with the Lower Grimstorp Metabentonite. The matching U-Pb dates and closely comparable apatite microphenocryst chemistry from WIC rocks and the Baltoscandian tephra suggest the WIC as a primary candidate for much of the composite KKMB.
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Marcilly, Chloe M. & Torsvik, Trond H.
(2026).
Palaeogeography and palaeoelevation through time: controls on weatherability and long-term CO2 evolution.
Geological Society Special Publication.
ISSN 0305-8719.
565(1).
doi:
10.1144/gslspecpub2025-135.
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Palaeogeography plays a fundamental control on Earth's long-term climate by regulating the efficiency of silicate weathering, the primary negative feedback stabilizing atmospheric CO 2 over geological timescales. Accurate reconstructions of past land distribution, topography and shelf geometry are therefore essential for quantifying weatherability and modelling deep-time climate–carbon cycle interactions. In this study, we present a new Paleozoic palaeogeographic and palaeoelevation model that can be extended for the whole Phanerozoic. Using updated plate tectonic models, fossil-constrained land–sea boundaries, climatically sensitive lithologies and physically informed elevation classes derived from modern Earth statistics, we produce global 10 Myr-interval maps that include seven topographic layers from deep shelves (−200 m) to high mountains (>4 km). Our approach improves estimates of exposed land area, shallow and deep continental shelves, and regions of high weatherability. We show that differences in land distribution within ±10° of the equator and within climatically defined high-weatherability zones, strongly affect CO 2 predictions in carbon-cycle models, particularly during the Early Paleozoic and the Devonian. The new reconstructions refine Paleozoic sea-level estimates and reveal how evolving continental elevations modulated silicate weathering intensity and contributed to transitions between greenhouse and icehouse states, including the initiation and termination of the Late Paleozoic Ice Age.
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Aalstad, Kristoffer; Alonso-González, Esteban; Pirk, Norbert; Westermann, Sebastian; Willmes, Clarissa & Yang, Ruitang
(2026).
Evolving beyond collapse: an adaptive particle batch smoother for cryospheric data assimilation.
Geoscientific Model Development.
ISSN 1991-959X.
19(18),
s. 8565–8596.
doi:
10.5194/gmd-19-8565-2026.
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We present a new adaptive particle-based data assimilation scheme for cryospheric applications that leverages promising developments in importance sampling. The proposed approach seeks to combine some of the advantages of two widely used classes of schemes: particle methods and iterative ensemble Kalman methods. Specifically, it extends the Particle Batch Smoother (PBS) that is commonly used in cryospheric data assimilation, with the Adaptive Multiple Importance Sampling algorithm. This adaptive formulation transforms the PBS into an iterative scheme with improved resilience against ensemble collapse and the ability to implement early-stopping strategies. As such, computational cost is automatically adapted to the complexity of the problem at hand, even down to the grid-cell and water year level in distributed multiyear simulations. In homage to the schemes that it builds on, we coin this new algorithm the Adaptive Particle Batch Smoother (AdaPBS) and we test it across a range of scenarios. First, we conducted an intercomparison of some of the most commonly used cryospheric data assimilation algorithms using Markov Chain Monte Carlo (MCMC) simulation as a costly gold-standard benchmark in a simplified temperature index model assimilating snow depth observations. We further evaluated AdaPBS by assimilating snow depth observations from the ESMSnowMIP project at 6 different sites spanning 3 continents, using an ensemble of simulations generated with the more complex Flexible Snow Model (FSM2). Our results demonstrate that AdaPBS is a robust and reliable tool, outperforming or at least matching the performance of other commonly used algorithms and successfully handling complex cases with dense observational datasets. All experiments were carried out using the open-source Multiple Snow Data Assimilation System (MuSA) toolbox, which now includes AdaPBS and MCMC among the growing list of available cryospheric data assimilation methods. Beyond our cryospheric focus, the scheme has the potential to be applied directly to the closely related fields of land surface and hydrological data assimilation as well as more general geoscientific Bayesian inference problems.
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Jewitt, David; Luu, Jane & Kim, Yoonyoung
(2026).
Investigation of Split Comet 240P/NEAT.
Astronomical Journal.
ISSN 0004-6256.
172(2).
doi:
10.3847/1538-3881/ae83ac.
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We present time-series observations of the split comet 240P/NEAT near perihelion, obtained using the Nordic Optical Telescope. The brighter component, 240P-A, has an estimated radius in the range 400─600 m, and loses dust at the peak rate 130 kg s^−1. The ejected dust has characteristic size ∼50 μm, is expelled sunward at ∼25 m s^−1, with a total ejected mass in the period of observation ∼1.5 × 10^9 kg. Mass loss from the fainter component, 240P-B, peaks at ∼35 kg s^−1 and the total ejected mass was 2.3 × 10^8 kg. The radius of 240P-B is uncertain, with a best estimate ∼300 m and an absolute lower limit 50 m. 240P-A and 240P-B are currently separating at about 1 m s^−1, a speed that is likely accelerating as a result of differential outgassing forces, and have a separation age of >3 yr. The splitting of 240P is incompatible with the action of tides, impact, and internal pressure build up. 240P fits a developing picture, in which small comets are destroyed by rotational instabilities triggered by outgassing torques, an explanation that can be tested in 240P by future observations.
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Mack, Laura & Pirk, Norbert
(2026).
Reddy: An Open-Source Toolbox for Analyzing Eddy-Covariance Measurements in Heterogeneous Environments.
Boundary-Layer Meteorology.
ISSN 0006-8314.
192(9).
doi:
10.1007/s10546-026-01003-5.
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Land–atmosphere exchange is mediated by turbulent fluxes that can be quantified with eddy-covariance (EC) measurements. EC has been widely used to measure ecosystem-scale vertical exchange between atmosphere and vegetation, and to test and refine atmospheric turbulence theories, thereby improving the representation of turbulent fluxes in land surface models. Traditionally, research has focused on idealized, homogeneous and flat surfaces, but recent work increasingly targets turbulent exchange in complex, heterogeneous environments under non-ideal conditions, where challenges include advective fluxes, mesoscale circulations between contrasting surface types, and non-stationary nighttime turbulence. Here, we introduce the open-source R package Reddy, which integrates multiple EC analysis methods into a single modular framework. Reddy enables users to tailor post-processing choices to site-specific conditions by integrating turbulence diagnostics and flux calculations in an iterative re-evaluation spiral, where processing choices are adapted step-by-step. The package supports station management and facilitates detailed scientific analyses, and is accompanied by an extensive documentation and hands-on EC processing tutorials. We demonstrate Reddy using measurements from three Norwegian sites: (1) a morning transition following a strongly stably stratified night at an alpine tundra valley, (2) spectral and ogive analysis before and after ice-cover transition at a boreal lake, and (3) fitting flux–variance relations at a permafrost-affected palsa peatland. Comparison with EddyPro shows close agreement for carbon dioxide fluxes derived from closed-path systems, but increased scatter for near-zero methane fluxes derived from open-path systems. Reddy extends existing EC software and helps bridging micrometeorology and ecology in heterogeneous, real-world environments.
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Herbst, Konstantin; Dalla, Silvia; Engelbrecht, N. Eugene; Muscheler, Raimund; Owens, Mathew & Zheng, Minjie
(2026).
Assessing uncertainties in the numerical modelling of cosmogenic radionuclide production.
Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences.
ISSN 1364-503X.
384(2329).
doi:
10.1098/rsta.2025.0348.
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Abstract The terrestrial production of cosmogenic radionuclides such as 10Be, 14C and 36Cl is triggered by spallation reactions of high-energy particles with atmospheric constituents such as oxygen, nitrogen and argon. After being produced and transported within the atmosphere, these radionuclides are deposited in natural archives, storing, for example, solar information over thousands of years. Therefore, records of 10Be, 14C and 36Cl can be used to reconstruct solar activity back in time. However, to understand the underlying physical processes that dominate production and interpret the observations, numerical modelling is crucial. Here, we shall discuss the dependencies of the numerically derived production rates on a variety of factors that include the effects of the choice of the local interstellar spectrum (LIS), the geomagnetic field and the production cross-sections available in the literature. We show that the investigated factors have modest to significant impacts on the modelled production rates of cosmogenic radionuclides and identify the discrepancies in the available cross-sections as the most crucial factor. This article is part of the Theo Murphy meeting issue ‘Radiocarbon and cosmic radiation events’.
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Dalla, Silvia; Herbst, Konstantin; Muscheler, Raimund & Owens, Mathew J.
(2026).
Radiation doses during extreme solar energetic particle events.
Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences.
ISSN 1364-503X.
384(2329).
doi:
10.1098/rsta.2025.0259.
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Abstract Ions and electrons accelerated to high energies during flares and coronal mass ejections at the Sun may escape the solar atmosphere and, guided by the interplanetary magnetic fields, propagate through space to near-Earth locations. These Solar Energetic Particles (SEPs) can be detected directly by spacecraft instrumentation. The highest energy SEPs may also propagate through the geomagnetic field and precipitate to low atmospheric heights, producing secondary particles including neutrons and protons that trigger the formation of cosmogenic radionuclides. The space weather effects associated with the SEP ion population (for the most part protons) consist principally of radiation risk to aviation, humans in space and spacecraft. This paper focuses on the risks to aviation and astronauts and emphasizes how the parameters of the SEP event, including fluence and spectrum, affect radiation doses. Space weather effects for events that took place in recent decades, for which a large body of measurements and models exist, are discussed. SEP events of extreme magnitudes, such as those extrapolated from radionuclide data from the distant past are then considered and first estimates of the associated radiation at aviation altitudes and in space presented. These are worst-case estimates derived within the assumption that the radionuclide spike was caused by a single SEP event and that the particle spectrum and geomagnetic conditions were the same during all events. This article is part of the Theo Murphy meeting issue ‘Radiocarbon and cosmic radiation events’.
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Kleber, Gabrielle E.; Mannerfelt, Erik Schytt; Schloemer, Stefan; Senger, Kim; Magerl, Leonard & Hensgens, Geert
[Vis alle 11 forfattere av denne artikkelen]
(2026).
Subglacial geology and thermal conditions regulate methane emissions from Svalbard glaciers.
Nature Communications.
17,
s. 1–12.
doi:
10.1038/s41467-026-77190-z.
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Melt rivers from valley glaciers and ice sheets release methane by transporting microbial or geologic methane from beneath glaciers, making it available for atmospheric emission. However, the mechanisms and magnitude of such methane release remain poorly understood due to limited studies. Here, we show how subglacial geology and glacier thermal conditions control methane supersaturation in meltwaters from 19 valley glaciers across central Svalbard. We find that all sampled meltwaters are supersaturated with methane, with peak concentrations up to 425-times atmospheric equilibrium. The carbon isotopic compositions of the methane and the presence of ethane and propane indicate that the methane is largely of thermogenic origin. Ground-penetrating radar surveys show that the extent of temperate ice at the glacier bed plays a critical role in facilitating methane acquisition, particularly in regions underlain by organic-rich, shale-dominated geological formations. This mechanistic insight is relevant for glaciated regions worldwide with organic-rich geology and suggests that accelerated glacier melt may amplify methane mobilization from beneath glaciers.
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