bluuebunny/crossref_metadata_2025 huggingface dataset:
Convective Mixing: an Energetically Consistent Non-Local Parameterization
Authors: Perrot Manolis , Lemarié Florian
Published: March 2024

         During shallow and deep oceanic convection, eddy-diffusivity parameterizations are known to fail since advection by non-local plumes is the primary source of turbulent transport. Integration of the Mass-Flux concept to correct Eddy-Diffusivity approaches has long been studied and applied for parameterizing convection in atmospheric models, and very recently in ocean models. This closure involves breaking down vertical turbulent fluxes into two components: a diffusion term that addresses local small-scale mixing in an near isotropic environment, which intensity is typically scaling with turbulent kinetic energy (TKE) ;
a mass-flux transport term, that accounts for the non-local transport due to vertically coherent plumes within the environment.
We expose an energetically consistent coupling of Eddy-Diffusivity Mass-Flux (EDMF) schemes with TKE schemes, in order to model oceanic convection.To achieve such a goal, we reexamine PDE-based derivations from first principles relying on multi-fluid averaging techniques. This approach offers several key advantages. Firstly, it allows to establish fully consistent local and global energy budgets between resolved and subgrid scales, effectively rectifying energy biases present in prior EDMF schemes. Notably, it facilitates a clear separation of convective and turbulent small-scale energy reservoirs. This is a significant departure from traditional schemes used in ocean modeling to account for non-local effects (e.g. KPP). It also provides a lucid description of boundary terms in order to remedy double-counting errors.Secondly, when compared to existing oceanic schemes, our model demonstrates performance in reproducing mean fields as well as higher-order moments such as TKE, vertical fluxes, and turbulent transport of TKE. It is validated against Large Eddy Simulation (LES) and observational data of oceanic convection.Thirdly, during the theoretical development of the scheme, we maintain transparency regarding underlying assumptions, and systematically assess their validity in the light of LES data. Thus our framework exhibits the flexibility to formally relax scale assumptions, leading toward scale-awareness.
The Evolution of Positioning Accuracy and Linear vs. Non-linear Motions of the Earth
Authors: Freymueller Jeffrey
Published: March 2024

The precision and accuracy of GPS/GNSS positioning has improved by considerably more than an order of magnitude over the course of my career, and the amount of data readily available (GNSS sites) has increased by several orders of magnitude. Over the last 40 years, geodesists have exploited this dramatic (and still continuing) increase in measurement capability to discover and study an ever-increasing set of phenomena. In the 1980s and early 1990s, the GPS satellite constellation was incomplete and there was only a sparse global tracking network. As a result, measurement noise limited rate accuracy to a few to several mm/yr, whereas today we are approaching accuracies of a few tenths of 1 mm/yr for long-term rates, and likely approaching the limit at which variability in surface loading makes motions fundamentally non-linear.In this talk I will take a historical perspective, highlighting the improvement in measurement capabilities and our understanding of tectonic and other earth processes. At the beginning of my career, we focused on estimating rates of steady processes like rigid plate motions, the distribution of strain across rapidly-deforming plate boundary zones, or the displacements due to large earthquakes. We thought that over most of the Earth, motion and deformation mostly occurred linearly with time. The noise level in position solutions at that time was very high, and most non-linear variations in observed time series were considered to be noise either due to positioning error or to unstable geodetic monuments. While the deformation due to changing surface loads was recognized as a physical signal, knowledge of the changing loads was rudimentary and the signal was below the noise level in most cases. Today we recognize a wide variety of signals that produce a mix of linear and non-linear motions of the Earth, and positioning geodesy has become the essential tool for studying most of them. I have had the good fortune to work on measuring and understanding many of these processes, and I will discuss some of the highlights of the evolutionary path of positioning geodesy along with future perspectives. We have reached, or nearly reached, the point at which the approximation of linear motion breaks down because the measurement precision is now comparable to or smaller than the non-linear surface loading deformation over most of the planet. The coming years should see more exciting discoveries, but we must think broadly about the full range of geophysical signals that are contained within our data.
Investigating Interactions between Subduction Initiation and Plate Reorganizations From A Global Perspective
Authors: Zhou Xin , Coltice Nicolas , Tackley Paul
Published: March 2024

Subduction initiation (SI) creates new subduction zones and provides driving forces for plate tectonics, being a key process of theplate tectonic regime on Earth. Although SI has been extensively studied in 2D regional numerical models, obtaining a global perspective on SI remains elusive. Geological observations and plate reconstructions both suggest that SI is coeval with the global or local plate reorganizations. The tectonic plate reorganizations are marked by rapid changes of plate motions occurring over a few million years and are recurrent throughout Earth’s history.  One of the most well-known plate reorganization events occurred at approximately 53-47 Ma ago, characterized by the bending of Hawaii-Emperor Seamount Chain. Simultaneously, several SI events occurred in the Pacific Plate, such as Izu-Bonin-Mariana (~52 Ma) and Tonga-Kermadec (~50 Ma). The relationship between SI and plate reorganizations, as well as their collective impacts on continental evolution, is poorly understood. It is also unclear whether these processes are dominated  by a “top-down” or “bottom-up” mechanism. This study is committed to exploring the interaction between SI and plate reorganizations using 3D global mantle convection models. We reproduce SI coeval with plate reorganizations in these numerical models. We analyze the changes of stress distribution in the lithosphere during the plate reorganizations and their effects on SI. A variety of different interplays between SI and tectonic plates reorganizations have been identified based on their chronology and driving mechanisms. We also investigate their influences on the supercontinental breakup and assembly. Two major plate reorganization events, occurring at 100 Ma and 50 Ma ago respectively, are used to compare with the numerical modeling results. The effects of key parameters, such as lithosphere thickness and strength, will be examined. Plate reconstruction models will also be included to study the interaction between SI and plate reorganizations in the future.
The economic and environmental impacts of UK meat imports post-Brexit
Authors: Wang Kaixuan , Liu Lirong , Chenoweth Jonathan , Morse Stephen
Published: March 2024

The United Kingdom (UK), a high consumer of meat, has traditionally relied heavily on the European Union for its meat imports. However, with the advent of Brexit, the UK now faces the imperative of identifying potential meat-importing nations. The choices of different meat import countries not only impact the economy and environment of the UK but also other countries around the world. This study builds the UK Meat Trade-centred World Input-Output Model (UK-MTWIO), incorporating diverse import data within various scenarios. With different scenarios considering costs, GHG emission and animal welfare, this study analyzes the economic, environmental and animal welfare impacts on the UK and other countries worldwide. The novelty involves the comprehensive consideration of scenario setting, the application of RAS method as well as the animal welfare analysis with the method of world input-output model. The study reveals that beef imports have the most significant impact on the imports of the lamb and pork. Meanwhile, the changes in the UK's meat trade may change the trade partners of some major meat-importing countries. In terms of environment, some import scenarios have the potential to contribute to GHG emissions reduction in the global agricultural sector: CHN, MEX, and JPN are typical countries that are significantly impacted. The results of this study provides valuable insights for policymakers making meat trade decisions post-Brexit.
DEBRA: A multi-rheological 2D steep shallow water finite volume scheme for debris flow propagation in mountain areas
Authors: Bonomelli Riccardo , Pilotti Marco , Heidarian Payam
Published: March 2024

In steep mountain areas, rapid mass movements such as avalanches and debris flows are surface processes which are characterized by large masses of granular material flowing at high speed. These processes may pose a serious threat whenever their path crosses populated areas, or damage key infrastructures. Numerical methods describing the motion of granular material coupled with remote sensing are the only option to assess run-off distance, velocity and depositional height, ultimately used to construct hazard maps. State of the art numerical modelling include three-dimensional and multiphase description of the phenomena. Despite the technical advancement provided by these implementations, which tend towards a complete model, in which both solid and liquid phases are considered, complexity, computational burdens and calibrating parameters scale accordingly. However, due to the intrinsic unknowns connected to debris flows (e.g. rheology, availability of sediments, liquid discharge), in the context of hazard mapping using a monophasic assumption regarding the physics of the flow is still a viable option because of the relatively low model complexity and computations times, allowing the user to perform multiple simulations to account for uncertainties. In the literature there are various numerical codes able to describe monophasic granular flow on complex topography both commercial (e.g. RAMMS, FLO-2D), and open source (e.g. HEC-RAS Mud and Debris flow), with different rheologic assumptions. Most models solve the classical Shallow Water Equations (SWE) which may not be valid in steep mountain bathymetry. Furthermore defining the flow depth orthogonally to the bottom may lead to practical difficulties in some situations, only solvable by introducing laborious pre- and/or post- processing calculations which may be complex on irregular topography. In this contribution we present some advances on a shock-capturing finite volume numerical scheme able to solve the recently introduced monophasic 2D Steep Slope Shallow Water Equations (SSSWE) on an unstructured grid using a set of different rheological laws (Manning, Voellmy and O’Brien). The use of an unstructured grid allows the user to capture in a simplified way the interaction between the flow and the buildings or channel beds naturally present in the computational domain regardless of the mesh size used. Furthermore, we present a novel analytical solution of a dam break test case on a sloping channel in presence of the O’Brien rheology, useful to benchmark existing numerical models. The numerical model implemented is called DEBRA (Debris-flow Evolution and Behaviour for Risk Assessment) and we assess its performance against other widely used commercial software for debris flow simulation.
Hot Flow Anomalies Delimiting Traveling Foreshocks
Authors: Kajdic Primoz , Blanco-Cano Xochitl , Rojas Castillo Diana , Archer Martin , Turc Lucile , Pfaum-Kempf Yann , LaMoury Adrian , Liu Terry , Raptis Savvas , Vinicius Marcos , Lee Sun , Shutao Yao , Hao Yufei , Sibeck David , Zhang Hui , Omidi Nojan , Wang Boyi , Lin Yu , Escoubet Philippe
Published: March 2024

Transient upstream mesoscale structures (TUMS) are an important topic in the field of research of the near-Earth environment. These events form upstream of the Earth's bow shock and can perturb regions downstream it, i.e. magnetosheath and magnetopause. They can even affect the magnetosphere and ionosphere causing a range of space weather phenomena during periods without noticeable solar activity. There is still much to learn about the TUMS and the way they interact with the near-Earth environment. We are only beginning to understand how the different types of the TUMS relate to each other. In the past it has been shown that traveling foreshocks may contain foreshock cavitons, spontaneous hot flow anomalies and foreshock compressional boundaries (FCB). Here we present the first evidence, that traveling foreshocks may be bounded on at least one of their edges by hot flow anomalies (HFA) and by events that look like hybrids between HFAs and FCBs. We show two case studies observed by the Cluster and MMS constellations. Such studies enable us to better understand all the ways in which the solar-terrestrial interactions occur.
Mapping Tidal Flat Changes and Determining Drivers in China's Coastal Zones: An Efficient and Reproducible Remote Sensing Method
Authors: Hu Yuekai , Yuan Lin , Fan Huifang , Pang Yuwen , Li Yao , Ding Qiannan , Liu Juntian , Tian Bo , Zhou Yunxuan
Published: March 2024

The dynamic coastal zones, marked by rich biodiversity and rapid transformations due to human activities, present a challenging environment for monitoring and management. Tidal flats, a key natural feature of these zones, are increasingly subjected to anthropogenic stress, rising sea levels, and various environmental pressures. This study addresses the critical need for a robust, large-scale remote sensing approach to monitor these changes over time, particularly under fluctuating tides and evolving coastal landscapes. Using the three decades of Landsat 5 and Landsat 8 data (1990-2020), we developed an innovative approach for the automatic acquisition of low-tide imagery. Our method, which incorporates knowledge-based of tidal flat extraction, achieved a classification accuracy of over 95%. This technique effectively mitigates the impact of clouds, fog, and waves on image analysis, enabling precise and rapid delineation of large-scale intertidal zones. As a result, we produced the most extensive dataset on tidal flat areas in China's coastal zone, updated at three-year intervals. The spatial analysis results showed the primary distribution of tidal flats in Liaoning, Shandong, Jiangsu, Zhejiang, and Guangxi, which collectively account for over 70% of China's tidal flat areas. We observed distinct patterns of tidal flat evolution, with rapid changes in regions like the Liaohe River Delta, Yellow River Delta, Yangtze River Delta, and the Jiangsu Coast. These changes are closely linked to increased reclamation activities and salt marsh vegetation expansion. In contrast, coastal areas like Tianjin and Zhejiang showed a swift expansion of intertidal zones initially, followed by a stabilization post-2010, constrained by limited development space. Our study's approach to rapid tidal flat extraction has shown promising applications in other global river deltas. The comprehensive tidal flat mapping and data generation presented here offer valuable insights and support for the monitoring, management, and sustainable development of coastal wetlands.
Learning from the past to shape the future: Environmental change, health and ecosystem services of Lake Malawi
Authors: Junginger Annett , Schrenk Friedemann , Albrecht Christian
Published: March 2024

Freshwaters and their biodiversity are in a state of crises across the world. Yet, these ecosystems are of global significance and provide resources on which, unlike in Europe, the livelihoods of millions of people depend in sub-Saharan Africa. Academics and African universities, however, lack experts for meeting multifold challenges of saving hotspots of aquatic biodiversity. Two consecutive three-week field schools, funded by Volkswagen Foundation, have been conducted in Malawi between 2022 and 2023 and were based on a sustainable network of African and German partnerships initiated during previous field schools. For the first time, the field schools were initiated and conceptualized by former African participants, who now have been acting as field school lecturers. These field schools aimed at training M.Sc. and Ph.D. students from DR Congo, Zambia, Sierra Leone, Malawi, Tanzania, Uganda and Germany in paleo-limnology, aquatic ecosystem science, human health, sustainable resource use and conservation. All participating countries have important freshwater ecosystems often shared with neighboring countries experiencing strong and multifold anthropogenic pressure. The magnitude of these impacts can only be understood by a combination of paleo-limnological methods with actualistic ecological water analyses. The field schools have covered major aspects ranging from a) reconstructing past conditions, b) assessing the present state to c) planning the future. A One Health framework has been adopted, making use of a citizen science approach to translate our field work findings into public outreach projects. The ultimate goals of the field schools were: a) Establishment of permanent network of interdisciplinary collaboration in paleo-environmental and aquatic sciences between African and German universities, b) Establishment of a sustainable teaching and research program in paleo-environmental and aquatic sciences applicable at African universities such as in Malawi, and c) Initiation of a long-term collaboration and of joint research and teaching projects between African scientific partners in the participating countries. This collaborative approach opens new perspectives on further research for the sake of better management of African inland waters in general. Most importantly, this cooperation exposed and equipped young researcher with skills for further research work in their own countries.
The dissolution pattern of the flattened otolith of Pacific cod using the stepwise acid dissolution method
Authors: Aonuma Keito , Yokoyama Yusuke , Miyairi Yosuke , Chimura Masayuki , Hamatsu Tomonori , Sakai Osamu , Plaza Guido
Published: March 2024

The inner ear of fish contains calcium carbonate (CaCO3)-based crystals called otoliths, which play an essential role in hearing and balance. During otolith formation, new calcium carbonate is deposited in layers on the surface of the existing part and the part is no longer affected by metabolism. This feature means that each layer of the otolith retains the trace element ratios and isotope ratios it had at the time of formation. By analysing this preserved information, it is possible to make estimates about the environment and habitat at that time.The stepwise acid dissolution method has been used in several studies as a technique for analysing the radiocarbon isotope ratios preserved in otoliths. In this method, phosphoric acid is used to dissolves the otolith from the outermost to the innermost layers. It has the advantage that a large amount of carbon can be collected from a single otolith, compared to the mechanical methods for the calcium carbonate sampling from each layer of the otolith.However, this method involves dissolving the otolith in acid and the pattern of dissolution cannot be controlled minutely by the experimenter. Pacific cod (Gadus macrocephalus) otolith used by us is flattened and the dissolution pattern of such otoliths is not yet known. Furthermore, no direct observation of the otolith dissolution process has been made in relation to previous studies.In this study, we dissolved three Pacific cod otoliths in phosphoric acid to directly confirm the process of otolith dissolution in the stepwise acid dissolution method. We removed each otolith from the acid one or more times during the dissolution process, weighed it and observed the change in the shape of the otolith and the layer structure exposed on the otolith surface. As the dissolution progressed and the otoliths became smaller, we polished them to check that the internal layered structure had not been destroyed by acid penetration.As a result, we found that the serrated structures present on the outer edges of the otoliths are maintained when they are dissolved from the outside by acid. We also confirmed that acid dissolution from the outside does not destroy the inner layer structure, even microstructures such as daily rings. The validity of the stepwise acid dissolution method would be strengthened by these results. On the other hand, the otoliths were thinner as a result of acid dissolution, exposing the more inner layers on the flat surface. This is due to the thin vertical thickness of the flattened otoliths. This observation suggests that the collected carbon may be mixed with the carbon collected from more inner layer. This carbon mixing is able to be taken into account with future work. In addition, care should be taken when using this method near the nucleus, as the final stage of dissolution results in multiple holes in the otolith.
Redrawing early human dispersal patterns with cosmogenic nuclides 
Authors: Jansen John D. , Knudsen Mads F. , Garba Roman , Andersen Jane L. , Buylaert Jan-Pieter , Kameník Jan , Kurbanov Roger N. , Lachner Johannes , Lukyanycheva Mariya , Margold Martin , Murray Andrew S. , Nørgaard Jesper , Olsen Jesper , Rugel Georg , Stübner Konstanze , Usik Vitaly , Ylä-Mella Lotta
Published: March 2024

Burial dating with two cosmogenic nuclides (e.g. 26Al and 10Be) is unveiling the last 5 million years of the sedimentary record. There is no dating method of comparable reliability for the fragmentary records typical of terrestrial settings. For the first time, we can explore events on the same timescale as mountain-building, we can reconstruct landscapes that predate the initiation of the northern hemisphere glaciations, and we can explore milestones in the evolution of our species. Here we focus on illustrating the latter: two field sites in which 10Be-26Al burial dating has reshaped our understanding of early human dispersal in Eurasia. Both are well known Palaeolithic sites hosting Mode-1-type stone tools that despite being intensively studied have not been dated conclusively by other methods.At Korolevo on the Tysa River in western Ukraine, alluvium containing stone tools is dated to 1.42 ± 0.10 Ma using the burial dating model, P-PINI (Particle-Pathway Inversion of Nuclide Inventories). Korolevo stands as the earliest securely dated hominin presence in Europe and bridges the spatial and temporal gap between the Caucasus (~1.85–1.78 Ma)and southwestern Europe (~1.2–1.1 Ma). Our findings advance the hypothesis of colonisation of Europe from the east well before the Middle Pleistocene Transition.At Diring Yuriakh on the Lena River in eastern Siberia, stone tools are buried by aeolian sand sheets. We combine optically stimulated luminescence dating with the P-PINI burial dating model to yield an age of 417 ± 82 ka, which is at least 300 kyr earlier than the previously documented earliest human presence north of 60 degrees. This timing overlaps with exceptional warmth across the High North during the ‘super-interglacial’ MIS 11c (426–396 ka), suggesting that warm climate intervals permitted human migration well beyond widely accepted territorial bounds.Reflecting on these advances, we evaluate the pros and cons of burial dating relative to other widely used dating approaches in archaeology and palaeoanthropology.
Multi-year and first-year ice from RCM for assimilation in ECCC ice type analysis system
Authors: Komarov Alexander , Caya Alain , Buehner Mark
Published: March 2024

Arctic sea ice type information is essential for various operational and scientific applications including the support of marine users and guiding ice thickness retrieval algorithms operating with SMOS and CryoSat-2 data for improved sea ice prediction. A sea ice type analysis system developed at Environment and Climate Change Canada’s (ECCC) generates pan-Arctic ice type analyses at 5 km resolution every 6 hours. The ice type analysis system assimilates ice type information provided by passive microwave (AMSR2, SSMIS) and scatterometer (ASCAT) data, but assimilation of these observations is not reliable in the areas near land and in the narrow channels of the Canadian Arctic Archipelago due to their low spatial resolution of ~20-50 km. Therefore, assimilation of high-resolution ice type observations from synthetic aperture radar (SAR) is highly desired.In this study, we extended our approach for automated detection of winter multi-year ice (MYI) and first-year ice (FYI) at 1.6 km scale from RADARSAT-2 to RCM data. To this end, we collected more than 2,000 RCM images and corresponding image analyses products that were manually generated by the Canadian Ice Service (CIS) ice experts for the period of time between July 1, 2020 and July 31, 2023. From these RCM images we extracted SAR information for more than 30,000 pure MYI and more than 619,000 pure FYI data samples under no melt conditions as identified by the CIS image analyses.We demonstrated that separability measures for MYI and FYI classes in the spaces of the two predictor parameters (HV/HH polarization ratio and standard deviation of HV signal) are consistent with those we previously observed for RADARSAT-2. Furthermore, we found that our RCM-based MYI/FYI detection approach allows us to classify 60% of the winter CIS ice data samples with the accuracy of 99.6%. Preliminary results of assimilating RCM-based MYI/FYI high-resolution retrievals in combination with passive microwave and scatterometer data in the ECCC ice type analysis system will be also presented.
Revealing Redox Variability in the lithospheric mantle: Insights from Mg-chromite inclusions in diamonds from the Udachnaya kimberlite pipes
Authors: angellotti antonio , Marras Giulia , Logvinova Alla , Mikhailenko Denis , Stagno Vincenzo
Published: March 2024

The study of mineral inclusions trapped within lithospheric diamonds stands as one of the fundamental approaches to directly study the Earth’s interior, enhancing our comprehension of its chemistry and deep geological processes. The inclusions provide crucial insights into the pressure (P), temperature (T), and redox conditions (fO2) occurring during the diamond nucleation and growth. Among the various mineral inclusions observed in lithospheric diamonds, those characterized by a peridotitic mineral assemblage (P-type), frequently exhibit the presence of Mg-chromite (Stachel et al., 2022) that suggests their involvement in redox-driven diamond formation from CO2-bearing melts. Since the current understanding of the Earth’s interior redox state primarily relies on peridotite samples from the shallow upper mantle based on the Fe3+ content of spinels (Ballhaus et al., 1991), investigating the chemistry of spinel mineral inclusions in diamonds would extend the knowledge of the mantle redox state to greater depths. In this study, we focused on a suite of nine diamonds extracted from the Udachnaya kimberlite pipes, located within the Siberian craton. These diamonds show multiple dark and transparent inclusions with sizes between 30 and 200 µm in diameter. The selected diamonds are polished to expose some of the inclusions. The chemical composition was determined by electron microprobe while textural features were observed by scanning electron microscopy. The Fe3+/ΣFe ratios of both encapsulated and polished inclusions were measured by in situ synchrotron Mössbauer spectroscopy at the ID18 beamline of the ESRF synchrotron (Grenoble, France), employing a 6 x 15 µm2 focused beam. The analyzed Mg-chromites exhibit FeO contents of 15-17 wt% and Cr# and Mg# of 0.85-0.92 and 0.54-0.61, respectively. The Mössbauer data collected on the Mg-chromites show a large variability with Fe3+/ΣFe ratios ranging from 0.07 to 0.28. Interestingly, variable chemical composition for the Mg-chromites among inclusions trapped in the same diamond along with fO2 ranging within 2 log units below the fayalite-magnetite-quartz buffer suggest possible changes in the chemistry of the diamond growth medium providing, therefore, evidence of redox heterogeneities in the lithospheric mantle underneath the Siberian platform.
Prediction of sunspot number using Gaussian processes
Authors: Frigo Everton , Gonçalves Italo
Published: March 2024

The solar activity has various direct and indirect impacts on human activities. During periods of high solar activity, the harmful effects triggered by solar variability are maximized. On a decadal to multidecadal time scale, solar variability exhibits a main cycle of around 11 years known as the Schwabe solar cycle, leading to a solar maximum approximately every 11 years. The most commonly used variable for measuring solar activity is the sunspot number. Over the last few decades, numerous techniques have been employed to predict the time evolution of the solar cycle for subsequent years. Recently, there has been a growing number of studies utilizing machine learning methods to predict solar cycles. One such method is the Gaussian process, which is well-suited for working with small amounts of data and can also provide an uncertainty measure for predictions. In this study, the Gaussian process technique is employed to predict the sunspot number between 2024 and 2050. The dataset used to train and validate the model comprises monthly averages of sunspots relative to the period 1700-2023. According to the results, the current solar cycle, currently at its maximum, is anticipated to last until 2030. The subsequent solar maximum is projected to occur around the end of 2033, with an estimated maximum sunspot number of approximately 150. If this prediction holds true, the next solar cycle's maximum will resemble that observed in the current one.
Fiber seismic tomography of the Long Valley volcanic system
Authors: Biondi Ettore , Zhu Weiqiang , Li Jiaxuan , Williams Ethan , Zhan Zhongwen
Published: March 2024

High-resolution tomographic imaging of the subsurface structures beneath volcanic systems is fundamental to better assess their hazard and potentially estimate the amount of eruptive materials. However, obtaining such images represents a major challenge for multiple reasons. The significant velocity contrasts commonly present within volcanic systems require accurate wave simulations or traveltime modeling to correctly account for wavefield triplications and ray bending. Moreover, station coverage and temporary deployments usually cannot achieve the requirements needed to meet high-resolution imaging targets.We demonstrate how distributed acoustic sensing (DAS) data recorded on existing telecommunication fiber cables and employed within an accurate and efficient matrix-free Eikonal tomography workflow can overcome these limitations. Specifically, we produce high-resolution tomographic images of the Long Valley caldera system in California, which in recent years has been undergoing significant inflation and seismic unrest. Our results reveal a distinct separation between the large magma chamber at approximately 10 km depth and the shallow crust. We interpret this separation as an upper-crust lid confining the pressurized volcanic fluid released through the crystallization of the magma reservoir over time. Our study highlights the potential of DAS for advancing volcano science; from providing insights into subsurface structures to monitoring dynamic processing due to fluid and magma movements through these complex systems.
Process-based modelling of long-term carbon dynamics in a temperate swamp peatland
Authors: Afolabi Oluwabamise , He Hongxing , Strack Maria
Published: March 2024

Temperate swamps hold substantial carbon (C) in their standing biomass and can potentially accumulate peat. In Southern Ontario, Canada, swamp peats are estimated to store ~1.1 Pg C, with this C accumulation supported by distinct hydroclimatic conditions. Previous studies on swamps C fluxes are mostly based on short-term (30 years) interactions and feedbacks that exist between temperate swamp C flux and biophysical conditions. In this study, we adopted a process-based model (CoupModel, www.coupmodel.com) to simulate daily plant processes, energy, water, and C fluxes in one of the most well-preserved swamps in Southern Ontario, Beverly Swamp, over a 40-year period (1983-2023). CoupModel reproduced the measured C flux and controlling variables with (coefficient of determination, R2) values of 0.75, 0.94 & 0.6 for soil respiration, surface soil temperature (0-5 cm) and water table depth, respectively. Analysis of the interrelationships (R2 values) between the simulated carbon flux and biophysical conditions showed that 88%, 51%, 31%, 68% of soil respiration rates were explained by soil surface temperature, soil volumetric moisture contents (0-30 cm), water table depth and gross primary productivity, respectively.  Our model simulation showed the swamp’s C uptake capacity, as net ecosystem exchange, dwindled over the simulated period but it was a net C sink in most years. This decreasing trend can be attributed to warmer and drier conditions in the region, which may be exacerbated with future climate change predictions. Overall, the study shows that processed-based models (CoupModel) are effective tools for improving our understanding of long-term C dynamics of temperate forested wetlands and the interactions that exist between C flux components and abiotic conditions. This has implications for informed decision-making on the management of temperate swamp ecosystems and the C stored within them.
Incorporating ontological characteristics for global landform classification based on 30 meters DEM
Authors: Yang Xin , Zhou Chenghu , Li Sijin , Ma Junfei , Chen Yang , Zhou Xingyu , Li Fayuan , Xiong Liyang , Tang Guoan , Meadows Michael
Published: March 2024

Landform classification and mapping provide fundamental data for Earth science research, natural resource management, environmental monitoring, urban planning, and various other domains. Despite the availability of DEMs with 1-arc second resolution, global-scale studies on landform classification and mapping are inconsistent in terms of general classification systems and methods.Landforms represent not only assemblages of morphological characteristics but also encompass the human understanding of the Earth, which is constrained by the nature and scale of quantitative analysis. Here, we propose a novel framework for global landform mapping to significantly improve the quantitative evaluation of geomorphological features.The proposed framework incorporates geomorphological ontology that takes account of their conceptualization to construct classified objects. We propose the accumulated slope (AS) and mountain uplift index (MUI) to emphasize the integrity and continuity of geomorphological units, providing more precise results compared to traditional methods. Aggregating local terrain features into global metrics, AS effectively overcomes the potential negative influence of increased resolution on landform integrity. MUI aligns better with human perception of mountainous morphology and surpasses the limitations of window-based computing.In presenting the new framework, we have developed and made available a public dataset, Global Basic Landform Unit (GBLU), which incorporates a comprehensive set of objects that constitute the range of landforms on Earth. In emphasizing the integration of classification with quantitative analysis, GBLU highlights the connection between natural objects and human understanding in geomorphology and the Earth sciences. The GBLU outperforms previous datasets (the basic landform classification and global mountain assessment) in expressing landform details. GBLU can be downloaded at https://geomorph.deep-time.org. It serves as a valuable resource in facilitating a deeper understanding of landform spatial distribution and evolution, and supporting research in a diverse range of fields.
Bottom-heavy charge structure and lightning discharges in Tibetan Plateau thunderstorms
Authors: Qie Xiushu , Sun Zhuling , Li Fengquan , Wei Lei , Sun Chunfa , Zhu Kexin , Yuan Shanfneg , Liu Dongxia , Jiang Rubin
Published: March 2024

The main charge region in thunderstorms over Lhasa city with an elevation of 3700 m is investigated by using a VHF interferometer, incorporating with fast antenna, weather radar and cloud-to-ground lightning location. The evolution of charge structure and its effects on lightning discharges were discussed in a bottom-heavy thunderstorm. During the early developing stage, the thunderstorm exhibited an inverted dipolar charge structure with negative charge center over the positive, and lower negative intracloud (IC) lightning occurred in between. Then an upper positive charge region appeared as the convection intensifying, and the charge structure exhibited obvious tripolar pattern and with large lower positive charge center (LPCC), and fewer positive IC discharges occurred in the upper dipole but lower negative IC lightning still dominated. As the thunderstorm entered the later mature stage, both negative IC between the lower dipole and positive IC between the upper dipole observed simultaneously. With gradually depleting of the positive charge carriers by precipitation, the LPCC weakened, the positive IC lightning between the upper dipole dominated, and two negative CG flashes were able to occur. In the later stage, positive IC dominated, although not much.  The study further confirms the previous conclusion (Qie et al., GRL, 2005) that weak thunderstorms are characterized by a bottom-heavy charge structure, and in the vigorous stage of thunderstorm, it may exhibit tripolar charge structure with a large LPCC, which has a significant impact on lightning types.
Evolution of Silurian to Devonian magmatism associated with the Acadian orogenic cycle in Newfoundland Appalachians: Evidence for a three-stage evolution characterized by episodic hinterland- and foreland-directed migration of granitoid magmatism
Authors: Wang Chaoyang , Wang Tao , Cees van Staal , Hou Zengqian , Lin Shoufa
Published: March 2024

The migration and character of magmatism over time can provide important insights into the tectonic evolution of an orogen. We present evidence for three separate episodes of compositionally distinct granitoid magmatism associated with the Acadian orogenic cycle in the eastern and southern Newfoundland Appalachians. The interpretations are based on new zircon U-Pb ages, geochemical data, and Sr-Nd-Hf-O isotopic data for 18 samples from 15 Silurian and Devonian granitoid plutons, combined with previously published data. The three episodes outline hinterland and foreland-directed migration trends and represent subduction (435-420 Ma), syn-collision (415-405 Ma), and post-collision (395-370 Ma) settings in the Acadian orogenic cycle. The Silurian plutons (435-420 Ma) consist mainly of quartz diorite, tonalite, granodiorite, monzogranite, and syenogranite, with high-K calc-alkaline and enriched Sr-Nd-Hf-O isotopic compositions (e.g., εNd[t] = -5 to -2; εHf[t] = -3 to -1; δ18O = +6 to +8). They are interpreted to record the subduction of oceanic lithosphere of the Acadian seaway that separated the leading edge of composite Laurentia represented by the Gander margin and Avalonia. The Early Devonian plutons (415-405 Ma), containing more voluminous monzogranite and syenogranite, have calc-alkaline to high-K calc-alkaline features, adakite-like compositions, and more-depleted Sr-Nd-Hf-O isotopic compositions (e.g., εNd[t] = -6 to 0; εHf[t] = +1 to +3; δ18O = +5 to +6). This stage occurs mostly to the northwest of the Silurian, indicating a regional scale northwestward (hinterland-directed) migration of magmatism with a rate of > 9 km/Ma. The migration is interpreted to be related to the progressive shallow underthrusting of Avalonia beneath the Gander margin (composite Laurentia) at least as far as 90 km inboard. The Middle to Late Devonian plutons (395-370 Ma) consists mainly of monzogranite, syenogranite, and alkali-feldspar granite, which are silica- and alkali-rich with large negative Eu anomalies. These rocks are concentrated along both sides of the Dover - Hermitage Bay fault zone, which represents the boundary between Avalonia and composite Laurentia, to the southeast of the Silurian-Early Devonian igneous rocks. This stage of magmatism represents a foreland-directed (retreating) migration. The Early Devonian and Middle to Late Devonian magmatism were separated by a gap between 405 and 395 Ma, and recorded an evolution from (high-K) calc-alkaline to alkaline compositions, which is ascribed to partial delamination of Avalonian lithospheric mantle in a post-collisional setting.
The transition from marine to terrestrial in the Early Permian : Evidence from the Early Carboniferous-Late Permian sedimentary records of the eastern margin of the Ordos Basin, North China
Authors: Peng Sizhong , Feng Congjun
Published: March 2024

The sedimentary successions provide direct evidence of climate and environment, which offer clues to the cause of the great transition from marine to terrestrial in the Early Carboniferous-Late Permian in the Ordos Basin. The eastern Ordos Basin's early Carboniferous-late Permian strata are sequentially stratified in ascending order as the Benxi Formation of the early Carboniferous, the Taiyuan Formation of the late Permian, and the Shanxi Formation of the late Permian. The Benxi Formation is composed of mudstone with a large number of siderite concretions, carbonaceous mudstone, rhythmic layers of siltstone and mudstone, and coal. The rhythmic layers indicate depositional products of lagoon and tidal flat. The Taiyuan Formation comprises carbonate and clastic sedimentary record, which lithology is mainly biological detrital limestone, limestone with chert nodules, mudstone, coal, and locally sandstone, indicating a shallow-sea shelf depositional environment. The lower part of the Shanxi Formation is a lithological combination of black mudstone, and purple-red sandy mudstone rhythmic layers interbedded with sandstone and coal seams. The black shale contains both marine biological detrital and terrestrial plant fragments. The sandy mudstone rhythmic layers have developed a large number of tidal beddings (such as flaser bedding, wave bedding, and lenticular bedding). The upper part of the Shanxi Formation is mainly depositional in the delta front-plain system. The lithology is mainly fine-coarse grained sandstone, sandy mudstone interbedded with carbonaceous mudstone containing plant fossils and coal seams. Overall, the palaeoenviroment changes from humid-semihumid to arid-semiarid are recorded by the transition from shallow-sea shelf to tidal flat-lagoon to delta deposition records. This study has established the sedimentary facies sequence of the late Carboniferous-early Permian by investigating five typical outcrops on the eastern margin of the Ordos Basin, and analyzed the paleoenvironmental characteristics of the Benxi Formation-Shanxi Formation based on geochemical methods. In addition, we believes that the Shanxi Formation has not completely transformed into terrestrial deposits in the southeastern part of the basin, and it is still in a transitional marine-terrestrial depositional environment.
Plutonium reactive transport in fractured granite: Multi-species experiments and simulations
Authors: Zhang Xiaoying
Published: March 2024

Plutonium (Pu) in the subsurface environment can transport in different oxidation states as an aqueous solute or as colloidal particles. The transport behavior of Pu is affected by the relative abundances of these species and can be difficult to predict when they simultaneously exist. This study investigates the concurrent transport of Pu intrinsic colloids, Pu(IV)(aq) and Pu(V-VI)(aq) through a combination of controlled experiments and semi-analytical dual-porosity transport modeling. Pu transport experiments were conducted in a fractured granite to elucidate sorption processes and their scaling behavior. In the experiments, Pu(IV)(aq) was the least mobile of the Pu species, Pu(V-VI)(aq) had intermediate mobility, and the colloidal Pu, which consisted mainly of precipitated and/or hydrolyzed Pu(IV), was the most mobile. The semi-analytical modeling revealed that the sorption of each Pu species was rate-limited, as the sorption could not be described by assuming local equilibrium in the experiments. The model was able to describe the sorption of the different Pu species that occurring either on fracture surfaces, in the pores of the rock matrix, or simultaneously in both locations. While equally good fits to the data could be achieved using any of these assumptions, a fracture-dominated process was considered to be the most plausible because it provided the most reasonable estimates of sorption rate constants. Importantly, a key result of this work is that the sorption rate constant of all Pu species tends to decrease with increasing time scales, which implies that Pu will tend to be more mobile at longer time scales than observations at shorter time scales suggest. 
Combining Earth System Modeling and Machine Learning to Investigate Volcanic Sulfate Deposition in Polar Ice Cores
Authors: Maas Malcolm , Tsigaridis Kostas , Van Lier-Walqui Marcus
Published: March 2024

Volcanic eruptions emit large amounts of sulfur dioxide (SO2), water, and other chemicals into the atmosphere, both in the troposphere and the stratosphere. Most of the SO2 is converted to sulfate aerosol, which is eventually deposited following long-range transport. The deposits from large eruptions are potentially detectable in ice cores, but there are many cases in which sulfate layers have not been linked to their source volcanoes. As volcanoes can act as significant shocks to the global climate system, we are interested in locating these eruptions in order to increase understanding of the volcanic record. To narrow down the search, we performed 140 simulations of volcanic eruptions using the GISS ModelE Earth system model. We varied the latitude, longitude, Julian day, plume top, plume bottom, and injected SO2 and H2O amounts using a Latin hypercube sampling approach, and analyzed correlations between these parameters and sulfate depositions at ice core sites in Antarctica and Greenland. Using machine learning and parameter estimation, we generated probability distributions and maximum likelihood estimates for the parameters given sulfate deposition data, which can predict latitude with some skill. We find that the volcano latitude and SO2 content are best correlated with sulfate depositions at each pole, while longitude, Julian day, and H2O have small or insignificant effects. Plume altitude and thickness are important because they determine how much of the SO2 is injected into the stratosphere, which has implications for sulfur transport and lifetimes.