bluuebunny/crossref_metadata_2025 huggingface dataset:
Does thicker ice cover cause stronger glacially triggered earthquakes? - A case study from the southwestern Baltic Sea
Authors: Seidel Elisabeth , Steffen Holger , Steffen Rebekka , Ahlrichs Niklas , Hübscher Christian
Published: March 2024

Increasing and decreasing ice masses cause an isostatic adjustment of the crust, which can trigger fault reactivation. It could be assumed that the higher the ice load, the stronger the glacially induced fault reactivation, leading to stronger earthquakes. Here we focus on glacially triggered fault reactivation in the southern Baltic Sea over the past 200,000 years (since the Upper Saalian). Our study area comprises the Caledonian Suture Zone between the East European Craton and the West European Platform as well as the trans-regional Tornquist Zone. Consequently, it reflects a polyphase tectonic history. The fault zones and systems in this geoarchive have been mapped and studied through several reflection seismic investigations. They display variations in their characters, strike and dip directions, age, and depths, documenting the complex evolution.We focus on faults indicating reactivation during the Quaternary, determined by the seismic sections. After documenting their fault properties, we calculated the glacially induced Coulomb Failure Stress changes (∆CFS) at the faults over the past 200,000 years using finite-element simulations of various glacial isostatic adjustment models. The results show significant local and temporal differences in fault reactivation. We observe that shorter ice advances and lower ice loads correlate with higher ∆CFS, suggesting a higher potential for fault reactivation, which could potentially lead to stronger earthquakes if released in one event. Moreover, we will discuss if the lateral ice thickness gradient or the steepness of the flanks of the ice sheet might play a major role.
Different Approaches to the Impacts of Climate Change, with a Common Goal: a Healthy Planet
Authors: Tchiguirinskaia Ioulia , Qiu Yangzi , Schertzer Daniel
Published: March 2024

This work has benefited from a multidisciplinary scientific and technical contributions geared by the HM&Co Lab of the Ecole des Ponts ParisTech (hmco.enpc.fr) towards the sustainable, desirable, and resilient city. The deepening of the Universal Multifractal (UM) concepts and the encouragement of their operational applications have been linked to several initiatives launched in recent years to better integrate the heterogeneity/intermittency into public policy practices. Considering the complex, dynamic interactions between geophysical and anthropogenic fields within a conurbation such as the Ile de France region, a transition towards the shared value economy has been considered to best stimulate sober and collaborative development, and there exist at least 3 ways to approach today’s discussions about future transformations. Their intercomparison is the core of this presentation.Following the United Nations 2030 Agenda, the first most conventional approach is based on notions of sustainable development, supported by appropriate adaptation and mitigation of climate change.Combining the notions of extreme variability and complexity would require linking together geophysical and urban scales within extreme variability, and therefore considering geosciences, and not just geophysics! Such a synergistic and integrative approach would help move beyond traditional silo thinking, addressing the complexity of data- and/or theory-driven urban geosciences.Finaly, combining the notions of scaling and nonlinear variability would ultimately require linking cascades, multiplicative chaos, and multifractals. This would initiate a break with linear stochastic models towards stronger heterogeneity / intermittency, which would in turn lead to a plausible clustering of field and activity fluctuations. The appearance of multifractal phase transitions then becomes possible, considerably amplifying the impact of any action, and would make future transformations fully efficient, effectively imitating the way in which Nature acts. This will be finally illustrated using several examples of so-called Nature Based Solutions (NBS).
Buoyant gravity currents triggered by a collapsing mid-latitude submesoscale front
Authors: Boskamp Grete , Holtermann Peter , Umlauf Lars
Published: March 2024

Sharp fronts with temperature differences of approximately 0.5°C across a remarkably small lateral scale of order 10 m were observed in a subtropical region with strong mesoscale and submesoscale activity in the southeast Atlantic at 34°S, 6.5°E, far away from any coastal freshwater sources. These fronts were formed at the leading edge of a buoyant gravity current of 20-40 m thickness that propagated at a speed of order 0.1 m/s relative to the colder and thus denser surrounding waters. High-resolution turbulence microstructure observations revealed strongly enhanced turbulence inside the nose of the gravity current, while turbulence in the trailing bulk region was mainly wind- and convectively-driven and showed a strong diurnal modulation. Satellite and meteorological data suggest that the gravity current was triggered by the mesoscale strain-induced sharpening and final collapse of a larger-scale front at the edge of a mesoscale eddy during a period with decaying winds. In contrast to previous studies that have identified similar buoyant gravity currents in the equatorial ocean, our data suggest that they can also form at a mid-latitude location where rotational effects are strong. This suggests that even balanced fronts can decay into gravity currents under certain conditions, indicating a potentially important pathway for mesoscale energy dissipation and mixing.
Bayesian Inference of Rheological Parameters from Observations Before and After the Tohoku Earthquake
Authors: Govers Rob , Marsman Celine , Vossepoel Femke , van Dinther Ylona , D'Acquisto Mario
Published: March 2024

Geodetic data covering different phases of the earthquake cycle provide a great opportunity to improve our understanding of the processes and parameters governing the dynamics at subduction margins. However, quantifying the individual contributions of physical processes such as viscoelastic relaxation, afterslip, and (re)locking throughout the earthquake cycle remains challenging. Moreover, it is relevant to account for these processes within a rheological framework that is consistent over the entire earthquake cycle. We address this using Bayesian inference in the form of an ensemble smoother, a Monte Carlo approach that represents the probability density distribution of model states with a finite number of realizations, to estimate geodynamic model parameters. Prior estimates of the imperfect physical model are combined with the likelihood of noisy observations to estimate the posterior probability density distribution of model parameters. We construct a 2D finite element seismic cycle model with a power-law rheology in the mantle. A priori information, such as a realistic temperature field and a coseismic slip distribution, is integrated into the model. Model pre-stresses are initialized during repeated earthquake cycles wherein the accumulated slip deficit is released entirely. We tailor the last earthquake to match the observed co-seismic slip of the 2011 Tohoku earthquake. The heterogeneous rheology structure is derived from the temperature field and experimental flow laws. Additionally, we simulate afterslip using a thin, low-viscosity shear zone with a Newtonian rheology. We focus on constraining power-law flow parameters for the mantle, and the shear zone viscosity. We assimilate 3D GEONET GNSS displacement time series acquired before and after the 2011 Tohoku earthquake. The data require separate viscoelastic domains in the mantle wedge above and below ~50 km depth, and in the sub-slab mantle. Power-law viscosity parameters are successfully retrieved for all three domains. The trade-off between the power-law activation energy and water fugacity hinders their individual estimation. The wedge viscosity is >1019 Pa·s during the interseismic phase. Postseismic afterslip and bulk viscoelastic relaxation can be individually resolved from the surface deformation data. Afterslip is substantial between 40-50 km depth and extends to 80 km depth. Bulk viscoelastic relaxation in the wedge concentrates above 150 km depth with viscosities
Benchmarking FastIce, a new massively parallel thermomechanical ice flow solver
Authors: Utkin Ivan , Räss Ludovic , Quarenghi Filippo , Werder Mauro
Published: March 2024

Efficient modeling of ice sheets involves considering multiple coupled physical processes, including thermomechanical interactions. While using a Full-Stokes model for ice flow in Greenland and Antarctica provides most accurate results, it is can be extremely costly on a large scale with existing software, justifying the use of various reduced models.Some important features of ice sheets, such as ice streams, are inherently three-dimensional. Accurate stress distribution, particularly around topography features comparable to ice thickness and near a grounding line, can only be achieved with a full stress tensor. In addition, a reference Full-Stokes solver for regional to ice sheet scale simulations can be a valuable tool for calibrating reduced models.We introduce FastIce, a novel ice flow model for massively parallel architectures, written in Julia. Leveraging GPUs (Nvidia, AMD) and supporting distributed computing, FastIce includes a thermo-mechanically coupled Full-Stokes ice flow model and a novel conservative energy formulation for describing thermal effects. FastIce is written to be easily extensible, and its core is fully differentiable, enabling data assimilation pipelines using adjoint sensitivities and automatic differentiation (AD).We validate FastIce through ISMIP-HOM benchmark tests and assess the coupled thermomechanical solver using the method of manufactured solutions. Our results showcase the thermo-mechanical instability arising from the non-linear interaction between temperature-dependent viscosity of ice and shear heating, reproducing existing analytical results. We present the performance testing of FastIce in single-node and distributed scaling benchmarks on LUMI, the largest European supercomputer.
Intensification of the Indonesian Throughflow in a Coupled GCM During the Last Interglacial
Authors: Wei Sihua , Zheng Weipeng , Du Jinlong , Yu Yongqiang , Tian Jun
Published: March 2024

       The Indonesian Throughflow (ITF) plays a pivotal role in large-scale ocean-atmosphere interactions in the tropics, regulating the heat and freshwater budget between the Pacific and Indian Oceans. In the context of global warming in the 21st century, The Indonesian Throughflow are projected to be weaken (medium confidence) by CMIP6 simulations. As an analog of possible future warming, the Last Interglacial (LIG, Marine Isotope Stage 5e or Eemian), with global surface temperature reached about 2 °C above present, serves as an outstanding period to explore the climate response to the external forcing and the mechanisms behind it.       We use the model outputs from a set of Last Interglacial snapshot simulations carried out by CAS-FGOALS (the Chinese Academy of Sciences Flexible Global Ocean–Atmosphere–Land System model) under the protocol of PMIP for four time periods at 130, 128, 125, and 115 ka. Compared to the piControl simulations (the annual mean ITF flux is 18.46Sv), an annual mean ITF flux increase of about 30.6% - 35.9% was found in the LIG snapshot simulations (24.11 - 25.08Sv). During the LIG, the tropical western Pacific Ocean thermocline was deepened while the tropical eastern Indian Ocean thermocline was relatively shallowed, which was closely tied to the strengthening of the surface easterlies above the tropical western Pacific. Correspondingly, the gradient of the sea surface height between the tropical western Pacific and the tropical eastern Indian Ocean increased, causing pressure contrast between the two basins and probably contribute to the ITF strengthening. We also find that the thermocline gradient between the tropical western Pacific and tropical eastern Pacific was increased, suggesting a La Niña-like state during the LIG. Comparisons of models and proxies further support our conclusions. An examination of the changes in the thermocline water temperature (TWT) record from the eastern Indian Ocean found an enhancement of ITF during MIS 5. Besides, the Maritime Continent was supposed to be more humid by pollen records from west Java and sediment composition from Halmahera Sea.       Further analysis suggested that the strengthened ITF during the LIG is inconsistent with the weakened one in the 21st century. While the future global warming is primarily driven by increased CO2 levels, the climate changes during the LIG were principally caused by changes in orbital parameters.
Mapping Glacier Hydrology in 3D: Novel GPR Acquisition and Processing Techniques
Authors: Klahold Johanna , Schwarz Benjamin , Bauer Alexander , Racz Gabriela Clara , Ruols Bastien , Irving James
Published: March 2024

Ground-penetrating radar (GPR) has become a well-established tool in the field of glaciology thanks to its capacity for high-resolution imaging and the excellent propagation characteristics of radar waves in snow and ice. In this context, 3D surveying and processing techniques hold significant promise for examining the internal structure and dynamics of glaciers, yet 3D studies are rarely done due to time and cost constraints. In particular, the field of glacier hydrology could immensely benefit from the acquisition and dedicated processing of high-density 3D GPR data sets, as observations of hydrological conditions inside the glacier and at its base are of critical importance for model calibration and validation.In this contribution, we attempt to exploit the full potential of high-resolution 3D GPR data to study glacier hydrology. A novel drone-based GPR acquisition system enables us to collect high-density 3D data with unprecedented spatial coverage. Our corresponding processing scheme considers two complementary components: the prominent reflected arrivals, and the faint (often neglected) diffracted wavefield. Reflection amplitudes at the ice-bedrock interface are used to delineate subglacial channels, whereas diffraction imaging methods borrowed from exploration seismology facilitate the localization of englacial conduits.We present results from two case studies in the Swiss Alps: the Haut Glacier d’Arolla and the Glacier d’Otemma. Our workflow provides complementary maps of the subglacial drainage system and of well-developed englacial channels. For the Glacier d’Otemma, we combine these results with supplementary methods (photogrammetry, dye tracing, time lapse cameras, steam drilling, and hydrological modeling) to obtain a more comprehensive characterization of the drainage system.
Reconciling late Cenozoic spatio-temporal patterns of Alpine topographic changes from low-temperature thermochronology and glacial morphometric signatures 
Authors: Wapenhans Isabel , van der Beek Peter , Bernard Maxime , Colleps Cody , Amalberti Julien
Published: March 2024

Improving our understanding of the timing, rates and distribution of erosion across mountains and valleys plays a key part in resolving longstanding debates on how landscape dynamics are influenced by the interactions between climate, tectonics and erosion. In particular, the onset of glaciations and more variable climate in the Pliocene-Quaternary have been invoked to explain the observed global increase in erosion rates, arguing that glaciers are more efficient at eroding bedrock than rivers. But questions about the temporal and spatial impact of glacial erosion and potential feedback remain. To contribute to resolving this debate, we conducted a local-scale thermochronological study in the Tauern Window, Eastern European Alps, with the aim to compare our findings to patterns in the wider region and the Western Alps. The Tauern Window presents an ideal natural laboratory to isolate these interdependent effects due to its well constrained tectonic history of rapid uplift until ∼8 Ma. Comparatively, the western Alps have experienced similar glaciation but a different tectonic history, and show significantly higher geodetic uplift rates and millennial-timescale erosion rates. Thus, an East-West comparison could help shed light on the dominant controls on the laterally variable Alpine morphology.Here, we present new apatite (U-Th)/He (AHe) data distributed along elevation profiles through several glacial valleys: the Italian Ahrntal and the Austrian Floitental, Krimmler Achental and Windbachtal. The low closure temperature of the AHe system is sufficiently sensitive to enable correlating recorded exhumation/denudation to surface processes and landscape-shaping dynamics, and allows us to examine the late-Cenozoic thermal history of the area. AHe dates range from ~3.4 to 12.5 Ma; the youngest dates are thus time congruent with the onset of glaciation.Our data indicate variations in erosion rates with elevation down these valleys, which we suggest can be attributed to altitude-dependent glacial erosion intensity. These patterns are compared to a hypsometric analysis of the Eastern Alps, to determine possible links between observed denudation over the last few million years and present-day markers of glacially reshaped topography. This study also provides initial insight into the best suited locations for a future higher-resolution investigation using 4He/3He thermochronometry, which promises to be able to resolve the area’s denudation history into the Quaternary and allow for a more direct comparison to modern hypsometry. These findings will also inform a future focused investigation into landscape-shaping couplings discernible from thermochronological data used alongside landscape analysis via thermal-kinematic modelling in PecubeGUI.
Nanoscale experiments of intergranular dissolution-precipitation to understand deformation mechanisms in the upper crust.  
Authors: Billarent-Cedillo Andrea , Jefferd Mark , King Helen E. , Hangx Suzanne , Plümper Oliver
Published: March 2024

In the upper crust, rock deformation commonly occurs in the presence of aqueous fluids, which are known to alter the material's response to stress. These fluids facilitate dissolution and precipitation, driving changes in the mineral composition and texture. The interaction between dissolution-precipitation and deformation in the upper crust has been studied in various natural geological cases, through experimentation, and modeling. Recently, there has been increased emphasis on understanding the role of fluids in deformation at the nanoscale. This experimental study aims to comprehend the effects of deformation on dissolution and precipitation at the nanoscale, specifically at the boundary between individual mineral grains.Our research has focused on understanding quartz dissolution and precipitation at the grain boundary scale at hydrostatic pressures and temperature conditions representative of the upper 5 km of the crust. We report preliminary findings from our experiments on nano-milled quartz crystals, representing natural grain boundary geometry, in contact with different aqueous solutions in a closed system. The pH, salinity, and concentration of Si in solution were systematically altered to assess their impact on dissolution rates. By using 18O-doped solutions, coupled with nanoscale secondary ion mass spectrometry and atomic force microscopy, we can track the dissolved and re-precipitated material, and monitor the changes in the geometry of the nano-milled quartz surface. This constitutes the initial step in our effort to further explore and quantify the effects of differential stress at the grain boundary. Additionally, we present results from a pilot study designed to test how differential normal stress impacts asperity dissolution within quartz-quartz contacts. These experiments aim to improve our understanding of dissolution rates in relation to pressure solution, a significant deformation mechanism in sedimentary and fault rocks.This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie initial training network (FluidNET) grant agreement no. 956125. 
Unravelling the Tectonic History of an Intraplate Region: A Geochronological Study of the Danube Fault, Bavarian Forest, Germany
Authors: Ludat Alina Lucia , Friedrich Anke M. , Hofmann Florian , Bolhar Robert , Hahn Torsten
Published: March 2024

Deformation in the Earth’s upper crust is typically accommodated by faults, which can range from microscopic displacements to regional tectonic features. Despite being located in the continental interior of the Eurasian plate, Central Europe displays notable evidence for recent activity, including active faulting, even along fault lines previously presumed inactive. This intraplate region has experienced multiple phases of fault reactivation, which provide the basis for debate regarding the underlying causative deformation mechanisms and driving forces. Determining the timing of episodic fault activity and their deformation rates is crucial to investigating the mechanisms behind Cretaceous to Paleocene exhumation and its relationship to more recent fault activity.An excellent region for this purpose is the Bohemian Massif, which is characterized by a complex structural and lithological architecture recording a long history of deformation. This area hosts significant fault zones, such as the NW–SE-striking Pfahl and Danube faults. Despite being one of the largest faults in Central Europe with a prominent scarp and young morphology, the ages of inception and reactivation of the Danube fault remain poorly constrained. Furthermore, therefore, seismic risks associated with these significant intraplate faults are difficult to include in earthquake hazard catalogs.To determine the timing of fault-slip and re-activation of the intracontinental Danube fault system in the Bavarian forest, we designed a sampling strategy involving multiple radiometric geochronometers and judiciously sampled transects across minor faults exposed in numerous quarries. We are currently dating authigenic and synkinematically recrystallized minerals, including U-Pb dating of slickenfiber calcite and K-Ar dating of illite. We also employ 40Ar/39Ar thermochronology and multi-domain diffusion modeling of potassium-bearing minerals of the granitoid host rocks to determine the timing of exhumation and re-setting of this system due to fault activity.The earliest time constraint for the initiation of the Danube fault was established by using published U-Pb zircon ages of deformed granites (310 to 342 Ma) (Klein et al. 2008 Lithos 102). We anticipate the K–Ar ages of illite and U–Pb ages of calcite to be significantly younger, which would confirm potential phases of reactivation accompanied by fluid alteration during cataclastic deformation. These fluid-infiltration events could potentially serve as markers for dating various phases of fault reactivation, which, along with information from frictional resetting, offer insights into the dynamic evolution of the Danube fault over time.
Remote, long-term auroral kilometric radiation observations as a geomagnetic indicator of substorm onset
Authors: Waters James , Lamy Laurent , Coxon John
Published: March 2024

Auroral kilometric radiation (AKR) is a cyclotron maser instability generated radio emission that occurs in the region above the auroral oval; the observed intensity increases with the growth rate of the instability, indicating an active source region and the presence of accelerated electrons, while the emission frequency is inversely proportional to the altitude of a source along a field line. Remote observations can thus provide a direct insight into the spatial development of the primary coupling region between the magnetosphere and ionosphere during energetic phenomena. During substorms in particular, the auroral acceleration region has been shown to increase in altitude and increase the low-frequency power of the AKR spectrum, particularly towards dusk (Morioka et al. 2007, Waters et al. 2022). However, AKR is beamed anisotropically, which makes it difficult to observe global variability of the emission when a spacecraft is not in an ideal position, namely at dayside local times.With an automatic extraction of AKR observations from the Wind spacecraft, we have access to nearly 30 years of data from a variety of viewing positions. The latest 20 years of observations are made from the  dayside, near L1. To evaluate the efficacy of the AKR observations as an indicator of substorm dynamics and further constrain the visibility effects, we compare AKR bursts from Wind (Fogg, Jackman, Waters et al. 2022) to a published list of substorm events derived from the SuperMAG magnetometer network. We calculate the binary classification statistics in four local time sectors with more than 10 years of AKR observation. When evaluated over a 2 hour window, AKR bursts observed from the nightside and duskside have a good (> 0.6) recall of substorm events, while the duskside observations have a more favourable false alarm probability (< 0.4). Dayside observations have a high miss rate (~0.8), but a high specificity (> 0.9), thus exhibiting a reliable proxy for substorm activity. Observations from all local time sectors except the nightside have positive forecast skill as determined by the Heidke skill score. Occurrence distributions of AKR burst frequencies from each local time sector and event group highlight the components present in each local time sector. This work lays the foundations for further parameterisation of the visibility of AKR sources at different locations within the inner magnetosphere by Wind when observing from L1, where the effects of the frequency, magnetic local time and magnetic latitude of the source can be examined more finely. Such work is useful for providing context for past AKR observations, as well as for the interpretation of future radio observations (with the JUICE flyby of Earth, for example), observation scheduling or planning of future missions.
Arctic sea ice freeboard during summer – a new Cryo-TEMPO product
Authors: Braakmann-Folgmann Anne , Landy Jack , Dawson Geoffrey , Ricker Robert , Hendricks Stefan , Gilbert Lin , Brockley David , Rinne Eero
Published: March 2024

Arctic sea ice thickness impacts various physical and biogeochemical processes at the air-ice-ocean interface. For example, it determines how much sunlight reaches the base of the ice – a key parameter for primary production. It is also an essential variable for sea ice forecasts, shipping and other marine activities. During the summer months (May-September) melt ponds complicate the retrieval of sea ice thickness compared to winter. On the other hand, summer sea ice thickness observations are particularly important as this is when most shipping and biological production happen. Summer sea ice thickness estimates are also crucial to extend predictions by many months.In this study, we present the novel summer sea ice Cryo-TEMPO product. Cryo-TEMPO is a set of easily accessible thematic products derived from CryoSat data targeted at both expert and non-expert users. The summer sea ice product contains freeboard measurements and smoothed freeboard, which are calculated at each lead position along the altimetry tracks. The product covers the whole Arctic and the full CryoSat lifetime since 2010. It will be updated operationally from summer 2024 onwards. Comparisons against various airborne and mooring data were conducted for validation and will be presented, too.
Measurement of atmospheric methane and ethane at a suburban site using mid-IR absorption spectroscopy
Authors: Mohn Joachim , Zeyer Kerstin , Müller Michelle J , Schlauri Paul , Vollmer Martin K. , Brito Melo Daniela , Henne Stephan
Published: March 2024

Methane (CH4) is the second most significant greenhouse gas after carbon dioxide. The concentration of methane in the atmosphere has been continuously increasing for several years and is currently at almost 2000 ppb. Methane emissions arise from a variable mix of thermogenic sources, such as oil, natural gas, and coal mining, or biogenic sources, such as wetlands and agriculture. Co-emitted gases such as ethane (C2H6) and other hydrocarbons can be utilised as a tracer to discern thermogenic (co-emission of ethane) and biogenic (no ethane is emitted) methane sources (Commane et al., 2023, https://doi.org/10.5194/amt-16-1431-2023).Ethane concentrations in the Northern hemisphere were decreasing between 1970 and 2010, which was attributed to better emission controls from oil and gas production, storage, and distribution, as well as exhaust emissions from cars and trucks. However, emissions are currently on the rise once again, linked to additional emissions from oil and gas production for example from the Eastern USA, (D Helmig et al., 2016, https://doi.org/10.1038/ngeo2721).In November 2023 we started CH4 / C2H6 measurements in ambient air from a rooftop air inlet (approx. 15 m above ground) at the Empa research campus in Dübendorf, Switzerland using a MIRA Ultra analyser (AERIS Technologies, USA). To correct for drift effects and to calibrate the analyser, two cylinders of compressed air were analysed in regular time intervals. To minimize interferences of water vapour, sample and calibration gases were dehumidified. Concentration measurements were compared to results of a CRDS analyser (model 2401, Picarro, USA) for CH4 and to a GC-MS system (model 5975C, Agilent Technologies, USA) for C2H6.Compressed air measurements demonstrate that the MIRA Ultra gas analyser meets the manufacturer's specifications of sensitivity for CH4 and C2H6 of < 1 ppb/s and < 500 ppt/s, respectively. We will present a comparison of C2H6/CH4 data from the MIRA ULTRA analyser and GC-MS / CRDS. We foresee to complement CH4/C2H6 measurements with CH4 isotope analysis (δ13C, δD-CH4) by TREX-QCLAS and relate temporal variations to differences in CH4 source contributions by means of FLEXPART simulations.
Origin of brittle deformation and microseismicity in the ‘ductile’ mantle on oceanic transform faults
Authors: Cécile Prigent , Jessica Warren
Published: March 2024

Seismicity studies on both fast- and slow-spreading ridge systems have found along-strike variations in mantle mechanical behavior on oceanic transform faults (OTFs), at pressure and temperature conditions above the long-term brittle-ductile transition of peridotites at ~700°C. Plate motion on some sections of the fault is accommodated by aseismic slip only (ductile deformation), whereas motion on other sections is by slip and deep swarms of microearthquakes (semi-brittle deformation) of mantle rocks (e.g., McGuire et al., 2012; Yu et al., 2021). To explore the mechanisms responsible for lateral variations in mantle mechanical behavior and the occurrence of this deep mantle microseismicity, we carried out an integrated study on peridotite mylonites dredged from two OTFs on the Southwest Indian Ridge that record deformation at 700-1000°C.The samples show variable degrees of deformation, ranging from proto- to ultra-mylonitic textures. The most deformed zones of the mylonites are characterized by an increase in the proportion of fine grained (
Orogeny and mantle dynamics : Holmes (1931) revisited
Authors: Faccenna Claudio
Published: March 2024

Orogeny, i.e. the formation of mountains, represents perhaps the most spectacular surface expression of plate tectonics. Orogenic belts are regions in the continental lithosphere where horizontal shortening results in crustal thickening, accompanied by magmatism, metamorphism, and the formation of Earth's highest topographic reliefs. The search for the dynamic mechanisms underlying orogeny has been ongoing since the early days of geology.Building upon the influential work of Holmes (1931), we delve into the relationship between orogeny style and mantle dynamics. Here, I propose to distinguish between two types of orogeny: "subduction orogeny," associated with one-sided upper mantle subduction, and "mantle orogeny," linked to larger mantle convection cells. Extreme crustal thickening is a hallmark of the latter. Our proposition suggests that mantle orogeny is triggered by the penetration of slabs into the lower mantle, altering convection length scales. Numerical dynamic models support this idea, demonstrating that upper plate compression is linked to slab penetration into the lower mantle. Slabs can further induce buoyant plume upwelling intensifying whole mantle convection and upper plate compression.To validate this model, we examine the geological and topography evolution record. Present-day compressional backarc regions often coincide with slabs subducting into the deep lower mantle. The temporal evolution of Nazca and Tethyan slabs, along with associated Andean Cordillera and Tibetan-Himalayan orogenies, suggests that extreme crustal thickening beneath Bolivia and the Tibetan plateau occurred during slab penetration into the lower mantle. This thickening in the Tertiary period bears similarities to Pangea assembly events. We propose that Late Paleozoic large-scale compression is related to a shift from transient slab ponding in the transition zone to lower mantle subduction. If our model holds true, the geological record of orogeny in continental lithosphere can be a valuable tool for understanding time-dependent mantle convection. Episodic lower mantle subduction may, in turn, be causally linked to the supercontinental cycle.
Energy spectra of Solar Energetic Electron Events Observed with Solar Orbiter
Authors: Fedeli Annamaria , Dresing Nina , Gieseler Jan , Vainio Rami , Gómez-Herrero Raúl , Espinosa Francisco , Warmuth Alexander , Schuller Frederic
Published: March 2024

The identification of the phenomena responsible for the acceleration of solar energetic particles (SEP) still challenges current research and limits our forecasting abilities of SEP events. Even the most recent space missions, such as Solar Orbiter and Parker Solar Probe, are still not reaching close enough distances to the Sun to be able to make direct measurements of the acceleration processes without the effects of transport mechanisms.The analysis of SEP spectra is crucial to infer the underlying acceleration mechanisms of SEPs as different mechanisms are characterised by different spectral shapes and features. Making this connection can, however, be challenging as transport effects are also known for altering spectral shapes, and these processes are not fully understood either.Our analysis focuses on solar energetic electrons (SEEs). The acceleration of SEEs, especially by shocks, still raises multiple questions in our field. In our analysis we use the novel measurements of the Energetic Particle Detector (EPD) on boardthe Solar Orbiter spacecraft. EPD detects energetic particles with unprecedented time and energy-resolution (1-second resolution covering energies from the suprathermal to relativistic range). This data product, together with Solar Orbiter’s varying distances to the Sun, allows us to characterise features of the energy spectra of SEEs better than ever before and to pin down transport effects.We determine the peak intensity spectra of more than 200 SEE events using newly developed techniques, taking into account velocity dispersion as well as the pitch angle coverage of the instruments. We determine and characterise the spectral features of each event by fitting the spectra with multiple mathematical models.We will present the results of our statistical analysis and discuss which spectral features can be associated with acceleration or transport effects.
How the representation of microphysical processes affects the tropical energy budget in a global storm-resolving model
Authors: Naumann Ann Kristin , Esch Monika , Stevens Bjorn
Published: March 2024

Cloud microphysics are a prime example of processes that remain unresolved in atmospheric modelling with storm-resolving resolution. In this study, we explore how uncertainties in the representation of microphysical processes affect the tropical energy budget in a global storm-resolving model (SRM). We use the global SRM ICON with a one-moment or a two-moment microphysics schemes and do several sensitivity runs, where we vary one parameter of the applied microphysics scheme in its range of uncertainty. We find that the two microphysics schemes have distinct signatures, e.g., in how condensate is distributed among the different hydrometeor categories or in the intensity distribution of precipitation, but their tropical mean cloud fraction and total condensate profiles are rather robust. Precipitation efficiency sets the amount of condensate in the atmosphere and thereby links microphysical processes to the radiative properties of the atmosphere. Uncertainties in the representation of microphysical processes cause substantial spread in the top-of-the-atmosphere (TOA) energy balance. In agreement with the robustness of the cloud fraction, changes in the radiative balance at TOA are dominated by changes in the radiative properties of cloudy points. A shift towards higher cloud-ice concentrations in simulations with the two-moment microphysics scheme leads to more reflected shortwave radiation that is not fully compensated by less outgoing longwave radiation and results in a slight cooling of the atmospheric column. Overall, microphysical sensitivities at storm-resolving resolution are substantial and resemble part of the inter-model spread of a multi-model ensemble.
Rate of soil denudation from plot scale to river system in different social and physical environments
Authors: Cerdan Olivier , Bizeul Rémi , Evrard Olivier , Foucher Anthony , Gaillot Arthur , Grangeon Thomas , Landemaine Valentin , Minella Jean , Pak Lai Ting , Salvador-Blanes Sébastien
Published: March 2024

The negative effects of soil erosion vary widely including pollution and siltation of water bodies, reduced crop yields, organic matter loss, diminished water storage capacity. These adverse effects generate significant consequences on developing as well as modern societies, possibly leading to land abandonment and the decline of rural communities and therefore posing fundamental social challenges. While protection of the soil resources is rightfully considered an important target of environmental policy, it is crucial to accurately understand the impacts of soil erosion and allocate funds for mitigation. Achieving this requires a precise assessment of erosion rates and their geographical distribution. as well as the targeting of funds to remedy soil erosion requires a correct assessment of the amount of erosion that is occurring and of its geographical distribution. Accurate quantification of soil erosion is not only essential for environmental policy but also holds scientific significance. Recent studies stressed the importance of comprehending human-induced impacts on sediment fluxes as well as their potential effects on global biogeochemical cycles. This need is even accentuated in a context where there is a demand to assess with reasonable confidence the impact of rapid climate and land use changes on these budgets. This crucial information is often lacking.To measure the rates and geographical extent of soil erosion, both indirect and direct methods have been used. Indirect methods generally measure soil profile truncation or sediment accumulation relative to a reference soil horizon, exposed or buried reference object (such as roots, foundations…), or to the loss or accumulation of tracers. These methods are more suitable for studying historical erosion. To assess current erosion rates, direct methods, typically plot or catchment monitoring and field-based measurements (e.g. mapping of erosion features) are preferred. Among these, field-based methods are most effective.Based on the application of different monitoring methodologies in various social and physical environments, this study aims at bringing some insights into the causes of soil erosion rate variations across these different environments. The methodologies employed will range from long-term high-resolution monitoring at plot or catchment and river system scales to dating sediment cores in reservoirs. The relative importance of climatic against physiographic and anthropogenic factors will also be discussed.
Snow accumulation patterns from 2023 Airborne Laser Scanning data in Trail Valley Creek, Western Canadian Arctic
Authors: Hollenbach Borges Daniela , Grünberg Inge , Hammar Jennika , Rutter Nick , Krumpen Thomas , Boike Julia
Published: March 2024

Snow cover plays a pivotal role in the Arctic's climate, hydrology, and ecology, making the understanding of its deposition and accumulation dynamics crucial. Snow depth and its duration can directly influence soil temperature: the insulating properties of snow increase with greater snow depth, which prevents soil temperatures from declining in winter.  Trail Valley Creek, NWT, Canada, is located at the northern boundary of the tundra-taiga transition zone, approximately 45 km north of Inuvik, and is underlain by continuous permafrost. The region’s rapid warming points to a trend of vegetation changes such as shrub expansion northwards into the tundra.Topography and vegetation cover are the main drivers of spatial variation of snow depth across different landscapes, while wind significantly influences snow redistribution. This reallocation causes snow to accumulate preferably in terrain features such as valleys and leeward sides of ridges, and taller vegetation, as their height and intricate structure can favour snow trapping. Understanding the relationships among snow distribution, topography features, and vegetation types is vital, though it is often limited by the scarcity of high-resolution data with broad spatial cover.To investigate the spatial snow distribution in Trail Valley Creek, we analyzed how snow depth varies according to different topography classes and slope aspects, as well as the region’s different vegetation classes and heights. For this purpose, we explored records from Aerial Laser Scanning (ALS) collected during both winter and summer of 2023, covering an area of over 170 km2. We generated a high-resolution Digital Elevation Model (DEM) from the winter snow-covered surface (2023-04-02), a Digital Terrain Model (DTM) from the summer snow-free terrain (2023-07-10), and by combining both, created a 1-m resolution snow depth map of the area. Additionally, we used 3129 Magnaprobe ground-based snow depth measurements for validation (2023-03-26 to 2023-03-29). For the topography analysis, we classified the slope aspects, and subdivided the terrain into 10 geomorphological classes using the geomorphons approach. This method calculates terrain forms, such as plateaus, slopes, ridges and valleys, and their associated geometry using a machine vision approach. To analyze the role of vegetation cover, we used a 13-class map that categorizes land-cover features and vegetation types, such as graminoids, shrubs and trees, and vegetation height rasters, derived from the ALS summer data.Snow is the main driver of the hydrological system in Trail Valley Creek, and the outcomes of this study will provide insights in the important interplay between vegetation, snow depth and terrain characteristics in a permafrost landscape.
Dynamic changes in the landscape of bare sand patches in sandy grasslands
Authors: Wu Zifeng , Hasi Eerdun
Published: March 2024

Desertification is a major environmental problem in arid and semi-arid areas with fragile ecosystems and land degradation. Desertification of sandy grasslands in the arid and semi-arid areas of northern China is characterized by vegetation degradation and bare sand patches. The overall landscape of the sandy grassland is characterized by a mosaic distribution of vegetation patches and bare sand patches. This article selects 8 sample areas in two areas that are both located in sandy grasslands but have different landform expressions and uses Landsat data from 7 periods in 1990, 1995, 2000, 2005, 2010, 2015, and 2020. The distribution and changes of other landscape types such as bare sand patches in the past 30 years; further analysis of their landscape index; comparative analysis of dynamic changes of bare sand patches in the two regions using climate elements and socioeconomic data in the same period. The results show that: (1) In the past 30 years, the area of ​​bare sand patches dominated by dunes has decreased while the area of ​​bare sand patches dominated by blowout has increased (2) Index changes of bare sand patches dominated by blowout The amplitude is greatly expanded and the connectivity is more obvious. (3) Both areas are greatly affected by human activities. These findings can provide an important method for comparing the desertification process of the desert and also meaningful information for the prevention and control of desertification and sustainable development for the arid regions.Keywords: Bare sand patch, Landscape, influencing factors.
Prospects and challenges of simulating organic matter turnover and stabilization in soil systems
Authors: Pagel Holger , Streck Thilo , Sircan Ahmet , Manzoni Stefano
Published: March 2024

Understanding the turnover and stabilization of soil organic matter (SOM) is the key to highly productive agriculture and to climate change mitigation. Understanding and predicting biogeochemical matter and energy flows in soil systems is challenging due to persisting knowledge gaps regarding biological and energetic controls of SOM turnover and limited knowledge integration of informative data with process-based models. We present modeling concepts of microbially explicit soil organic matter models and shed light on integrating trait-based ecological frameworks in process-based models and the use of advanced data-model fusion approaches. We highlight some insights from applying process-based models and challenges we need to address to acquire robust predictions.
Chronology of deformation and metamorphism of an inverted passive margin: evidences of pre-orogenic peak-metamorphic conditions in Taiwan and Palawan island (The Philippines).
Authors: Mesalles Lucas , Lee Yuan-Hsi
Published: March 2024

We present new zircon fission-track age and RSCM peak-metamorphic temperature estimates from the Taiwan slate-belt and northern Palawan. The two regions represent the conjugate margins of the South China Sea that have undergone inversion during two separate collisional episodes, from the latest Miocene until present-day (Taiwan) and in the Middle Miocene (Palawan). In both regions the slate/phyllite and (meta-) sandstone stratigraphic successions have undergone green-schist and sub-green-schist facies peak metamorphic temperatures with a consistent positive correlation between stratigraphic age and metamorphic grade. A similar pattern is observed in the resetting degree of ZFT-ages, with shallow stratigraphic levels displaying unreset to partially-reset ZFT ages, while older strata exposed at the core of regional anticlines are fully reset. Importantly, ZFT young-peak ages (i.e. pooled age of the youngest ZFT grain-age population) and fully reset ZFT-ages are consistent within error, and constrain the initiation of rock cooling and exhumation to 5.9±1.5Ma (weighted mean of 6 pooled ages) in the section studied in the Northern Hsuehshan Range (Taiwan), and to 14.7±0.5Ma (weighted mean of 7 pooled ages) in Northern Palawan. Taken together our data indicates that peak-metamorphic conditions in both regions were reached before the main exhumation event and precede thrust-stacking and topographic growth.  Metamorphism is possibly related to basinal evolution (“burial metamorphism”) during the opening of the South China Sea or to some other tectonothermal events unrelated to the late Cenozoic mountain building processes. Our findings have important implications for the commonly assumed orogenic origin of low-grade metamorphic belts, as this assumption is implicitly included in the tectonic evolutionary models of orogenic development and in models of orogenic gold deposits typically found in slate belts, to name a few.