bluuebunny/crossref_metadata_2025 huggingface dataset:
Mineral/Fluid interaction as a potential bias in calcite U-Pb dating
Authors: Lanari Riccardo , Buzenchi Anda , Bragagni Alessandro , Dhuime Bruno , Brilli Mauro , Del Ventisette Chiara , Mattei Massimo , Conticelli Sandro , Avanzinelli Riccardo
Published: February 2023

The application of U-Pb dating method performed on calcite has exponentially increased over the last years, since constraining the age of the crystallization for such syn-kinematic minerals, would provide a specific timing of faults movement. The potential gain of this approach is evident but the robustness of the U-Pb method performed on calcites has been not yet systematically tested.  Here, we firstly demonstrated that a mineral/fluid interaction indeed affects the regression of the 238U/206Pb and 207Pb/206Pb data-points and therefore the age; and secondly, we propose an innovative application of U-Pb dating method and a new strategy to identify and reject analytically robust isochrons.We explore 36 samples, combining U-Pb dating performed with different methods along with carbon and oxygen stable isotopes compositions measured on the same fibres of calcite. The extremely high precision 207Pb/206Pb measured by Thermal Ionisation Mass Spectrometry  revealed that every sample experienced a certain degree of fluid interaction. We find no correlation between 238U/206Pb and the spread in δ18O. The higher spread in δ18O is instead coupled with a remarkable scattered data-points that yield U-Pb ages calculated with the different methods on the same samples with a large variability. In conclusion, our study demonstrates that great care must be taken when considering radiometric ages made on calcite since LA-ICP-MS large uncertainties might obscure the isotopic reorganization.
Sustainability of Pastoralism: Climate Change Risk to Rangelands in Eurasia
Authors: Nandintsetseg Banzragch , Chang Jinfeng , Sen Omer L.
Published: February 2023

Climate change is projected to increase the aridity of semi-arid ecosystems, including Eurasian rangelands (EAR), which provide ecosystem services that support food supply and pastoralist lifestyles. Climate hazards are expected to become more frequent and intense, leading to the most significant risk to pastoralists and impacting their future sustainability. There is an urgent need for research-based interventions that can help herder communities adapt to future risks. However, rigorous impact assessments of climate change on pastoralism-based livelihoods considering region-specific socioeconomic changes in the Eurasian Drylands are relatively neglected research areas with limited knowledge. Thus, we assess the climate change risk to rangelands in Eurasia under regional grazing patterns and intensity across EAR spatial domain (34−56◦ N, 20−130◦ E: West Asia, Central Asia and East Asia) during 1971–2100. We conducted a grid-scale (0.5 °× 0.5°) probabilistic risk assessment of EAR in the context of climate change based on probability theory. Risk is quantified as the product of the probability of a hazardous drought and vulnerability of the ecosystem. The probability of hazardous drought is defined by the Standardized Precipitation–Evapotranspiration Index. Vulnerability is defined as the expected difference in key ecosystem variables between years with and without hazardous conditions. The ecosystem variables were productivity (aboveground biomass, net primary productivity, soil carbon, and leaf area index) and plant-available soil moisture in the root zone, simulated with a process-based ecosystem model ORCHIDEE-GM (Organizing Carbon and Hydrology in Dynamic Ecosystems-Grassland Management) validated with field observations of biomass and soil moisture. Climate data were based on gridded observations and projections of CMIP6 the Coupled Model Intercomparison Project Phase 6) using scenarios ssp1-2.6, ssp3-7.0, and ssp5-8.5. Historical land-use data were based on the number of province-based livestock during 1971–2019. The constant value of 2019 is used to simulate the future impact of grazing on EAR. The results revealed that EAR experienced more frequent hazardous droughts with rapid warming and slight drying during 1971−2020, aggravated by increasing grazing intensity, which resulted in a reduction in soil water availability and grassland productivity, particularly in northeastern areas. In the future, climate change will lead to increased droughts in the EAR under these three scenarios. These great drought hazards increase the risk of rangeland productivity in the EAR, particularly in the western and southern parts of Central and Eastern Asia.
Modeling the 4D coupled dynamics of magma propagation, ground deformation, and gravity changes
Authors: Papale Paolo , Garg Deepak , Longo Antonella , Montagna Chiara
Published: February 2023

We illustrate GALES, a finite element C++ code that we developed during last >10 years. GALES solves the time-dependent 3D thermo-fluid dynamics (4D space-time) of non-Newtonian multicomponent flows (magma) and 2-way coupled elastic structure (rocks). GALES accounts from incompressible to compressible flow regimes, and it is therefore suited to simulate from under-saturated magma conditions deep into the crust to the rapidly accelerating conditions along volcanic conduits including transonic flow regimes leading to explosive volcanic eruptions. The code is implemented with a suite of models describing the real properties of multi-component multiphase magmas, which are locally (in space and time) computed. Magma dynamics are fully coupled with rock elasto-dynamics, allowing computation of the transient signals (deformation, gravity) associated with magmatic flows by accounting for rock heterogeneities, free surface and real topography. Geometrical complexities associated with multiple magmatic reservoirs, connecting dykes, volcanic conduits etc. can all be accounted for, in separate or individual simulations. Typical computational time steps of 0.01 s and simulation lengths of order hours allow confident computation of signal frequencies in the range 0.001 – 10 Hz, which is still under-investigated for magmatic and volcanic systems. The results illustrate several original aspects of magma dynamics and associated signals, such as the association between magma convection and generation of Ultra-Long-Period ground displacement dynamics; the ground deformation patterns associated with complex distributions of overpressure, both negative and positive, reflecting magma transfer across separate reservoirs; the decoupling of gravity and deformation sources associated with buoyancy-driven ascent of magma; the generation of transient explosive events associated with deep arrivals of gas-rich magmas in basaltic open system volcanoes; and many others.
Atmosphere and ocean climate model resolution in resolving Weddell Sea polynyas and their ocean-atmosphere interactions.
Authors: Ayres Holly , Ferreira David
Published: February 2023

The Weddell Sea Polynya is a seasonal opening within the sea ice cover of the Weddell Sea sector, typically found over the Maud Rise and inside the Weddell Gyre. It has been a rare occurrence in the satellite period, appearing in austral spring between 1973 and 1976 and again in 2016/17. The polynya formation has been shown to be complex, requiring a combination of ocean and atmospheric mechanisms to develop. The region is often poorly resolved in global climate models, with little agreement in ocean or sea ice dynamics. When Weddell Sea polynyas have occurred in models without forcing, it is not understood how they occur within the model, or why some models produce frequent polynyas and others produce none. Some studies have shown that increasing horizontal resolution improves the dynamics of the Southern Ocean, allowing for better parameterisation of small-scale features. Here, we use multi-model data of different resolutions, from the PRIMAVERA HighResMIP experiments, to determine how models of different atmospheric and ocean resolution resolve Weddell Sea polynyas. We assess the frequency, size, and location of polynyas in different resolutions, in addition to studying the ocean and atmospheric processes associated with the polynya in these models. Initial results of models that resolve frequent polynya show preconditioning in both the ocean and atmosphere, in addition to a small response to the polynya in the months following.
MaQuIs - Mars Quantum Gravity Mission
Authors: Woerner Lisa , Root Bart , Bouyer Philippe , Braxmaier Claus , Dirkx Dominic , Encarnacao Joao , Hauber Ernst , Hussmann Hauke , Karatekin Ozgur , Koch Alexander , Kumanchik Lee , Migliaccio Federica , Reguzzoni Mirko , Ritter Birgit , Schilling Manuel , Schubert Christian , Thieulot Cedric , von Klitzing Wolf , Witasse Olivier
Published: February 2023

With MaQuIs we propose a mission to investigate the gravitational field of Mars. Observing the gravitational field over time yields information about the planets tectonic lithoshphere, mass distribution, and composition. Consequently, this mission allows to study static and dynamic processes on and under the surface of Mars, including phenomena such as melting cycles and tectonic activity.MaQuIs will deploy quantum mechanical means to measure Mars gravitational field with the highest precision yet. In addition, the nature of the proposed instrumentation achieves high sensitivities without needing more complex satellite constellations. As such, MaQuIs follows successful missions for the Earth and Moon, extending the technology to Mars.In this presentation we will outline the expected scientific merit and explain the underlying technology and planned configuration of the mission.  
Investigating properties of statistical tests for comparing predictive performance with application to probabilistic weather forecasting
Authors: Möller Annette , Grupe Friederike
Published: February 2023

This work investigates several statistical tests in the context of probabilistic weather forecasting and ensemble postprocessing. The tests are commonly used for comparing predictive performance of e.g. two statistical postprocessing models.  In the first part of the analysis a case study is conducted on temperature data consisting of observations and ensemble forecasts. The tests are applied to compare the performance of two probabilistic temperature forecasts at different stations, for different lead times, investigating several standard verification metrics to measure prediction performance. The analysis shows that the tests generally behave consistently in the context of temperature forecasts. However, for certain scenarios some tests might be be preferred over the others. In general, the combination of the original Diebold-Mariano test with the continuous ranked probability score (CRPS) to assess forecast accuracy leads to the most consistent and reliable results.The second part of the analysis uses simulated data to investigate the general behaviour of the tests in different postprocessing scenarios as well as their size and power properties. Again, the original Diebold-Mariano test appears to perform most reliably and shows no noticeable inconsistent behaviour for different simulation settings.
Identification of source regions of the Asian Tropopause Aerosol Layer on the Indian subcontinent in August 2
Authors: Clemens Jan , Vogel Bärbel , Hoffman Lars , Griessbach Sabine , Thomas Nicole , Fadnavis Suvarna , Müller Rolf , Peter Thomas , Ploeger Felix
Published: February 2023

The Asian tropopause aerosol layer (ATAL) is a distinct feature during the Asian summer monsoon season with an impact on the regional radiative balance of the Earth's atmosphere. However, the source regions and the detailed transport pathways of ATAL particles are still uncertain. In our study, we investigate transport pathways from different  regions at the model boundary (MB)  to the ATAL using the two Lagrangian transport models  CLaMS (Chemical Lagrangian Model of the Stratosphere) and MPTRAC (Massive-Parallel Trajectory Calculations), two reanalyses (ERA5 and ERA-Interim),  and balloon-borne measurements of the ATAL performed by the Compact Optical Backscatter Aerosol Detector (COBALD) above Nainital (India) in August 2016.  Trajectories are initialized at the location of the ATAL, as measured by COBALD in the Himalayas, and calculated 90 days backward in time to investigate the relation between the measured, daily averaged, aerosol backscatter ratio and different source regions at the MB. Nine source regions at the MB are distinguished, marking continental and maritime sources in the region of the Asian monsoon. Different simulation scenarios are performed, to find systematic differences as well as robust patterns, when the reanalysis data, the trajectory model, the vertical coordinate (kinematic and diabatic approach) or the convective parameterisation are varied.While there are many robust features, the simulation scenarios also show some considerable differences between the air mass contributions of different source regions at the MB in the region of the Asian monsoon. The contribution to all air parcels from the MB varied between 5% and 40% for the Indo-Gangetic plain, the contribution from the Tibetan Plateau varied between 30% and 40% and contributions from oceans varied between 14% and 43% for different scenarios. However, the robust finding among all scenarios is that the largest continental air mass contributions originate from the Tibetan plateau and the India subcontinent (mostly the Indo-Gangetic plain), and largest maritime air mass contributions in Asia come from the Western Pacific (e.g. related to tropical cyclones such as typhoons).  Additionally, all simulation scenarios indicate that transport of maritime air from the Tropical Western Pacific to the region of the ATAL lowers the backscatter ratio (BSR) of the ATAL, while most scenarios indicate that transport of polluted air from the Indo-Gangetic plain increases the BSR. Therefore, while the results corroborate key findings from previous ERA-Interim based studies, they highlight the variability of the contributions of different MB regions to the ATAL depending on the meteorological input data, vertical velocities and in particular on the treatment of convection within the model calculations.  
The Relationship of Field Geometry, Harvester Size, and Traffic Intensity during Wheat Harvesting
Authors: Augustin Katja , Focke-Martinez Santiago , Duttmann Rainer , Hertzberg Joachim , Kuhwald Michael
Published: February 2023

Investigations of soil compaction in agricultural land often deal with the deployment of heavy, high-performance machinery and their impact on soil structure and functions. The traffic intensity on the field considers the spatial distribution of the number of wheel passes and the wheel load of the machinery. The intensity can vary due to changing machine and field characteristics. However, these dependencies are not analyzed in detail yet.To what extent the machine’s working size and field geometry influence the traffic intensities during wheat harvesting shall be presented in this contribution. A route planning system planned the routes of three different combine harvesters on 59 fields with varying field geometries. With these routes the spatial traffic intensities of the work process were modeled for all variants.To represent the structure of the field geometry, eight shape-indices were calculated. The traffic intensities were divided into classes indicating the percentage area for different threshold values of wheel load and wheel passes.The analysis of the three harvesters showed that the size of the machine has a significant influence on the total trafficked field area and the wheel load distribution. The larger the machine and working width, the more area is affected by high wheel loads, but less total area of the field is passed. Those relations are independent from the field zone (headland, infield or complete field area).The analysis of the field geometry shows that there is a strong correlation between the passed area with more than 5 and 10 wheel passes in the headland and three shape indices. These shape indices are the interior edge ratio (IER), the interior area ratio (IAR), and the mean fractal dimension (MFD). Both the IER and IAR are dependent on the size of the field. It shows that the larger the field area relative to the perimeter and headland area, the bigger the proportion of area in the headland that has been passed more than 5 and 10 times. Analogously, the more complex the field structure, the greater the proportion of area with more than 5 and 10 passes. This increased traffic intensity is probably because a larger field requires more yield transportations from the infield across the headland.The study shows that in wheat harvesting, the geometry of the field and the choice of the machine should be considered if high traffic intensities should be avoided to preserve the soil structure.
Trends and patterns in post-disturbance forest recovery estimated from Landsat and Sentinel-2 data using regression-based spectral unmixing
Authors: Mandl Lisa , Viana-Soto Alba , Seidl Rupert , Senf Cornelius
Published: February 2023

Natural disturbances and post-disturbance recovery are principal drivers of forest ecosystem dynamics and both are sensitive to climate change. While disturbances and their causes and consequences have received considerable attention from the scientific community in recent years, there is – however – a substantial lack of knowledge on post-disturbance recovery. Recovery is considered an essential measure of forest resilience to climate change, especially with regard to ecosystem service provision (e.g., protection from avalanches, water purification). Disturbances remove the top tree canopy, exposing the forest floor composed of different land cover types, such as bare soil, grassland and shrubby vegetation, which will gradually transition to treed vegetation over succession. The assessment of forest recovery by means of medium resolution optical remote sensing data (i.e., ~20 m spatial grain) poses some challenges in analyzing those spatially and temporally heterogenous recovery trajectories. To tackle this problem, we employed a temporally generalized regression-based spectral unmixing approach to dense time series of Landsat and Sentinel-2 data with the aim of characterizing the post-disturbance recovery trajectories across a large study site covering the eastern Alps (~125,000 km²). For training the spectral unmixing approach, we developed a multi-year spectral library for three endmembers: treed vegetation, non-treed vegetation and bare soil. Selection of pure endmembers was based on the LUCAS database, a pan-European disturbance map and Google Earth imageries. Applying the generalized regression-based spectral unmixing approach to a dense time series of Landsat and Sentinel-2 images results in annual fraction maps for the three endmembers, which can be used to characterize recovery trajectories after major disturbance events. Each pixel’s post-disturbance trajectory can thereby be described in a three-dimensional space composed of variable fractions of treed vegetation, noon-treed vegetation and bare soil. To facilitate interpretation of recovery trajectories, we focus on specific disturbance events covering the storms Kyrill (2007), Uschi (2003), and Vaia (2018). This allows for identifying (dis-)similarities between recovery trajectories of the same disturbance event and thus to investigate the full breath of potential recovery patterns after natural disturbances.
Jupiter’s hot spots as observed by JIRAM-Juno: limb-darkening in thermal infrared
Authors: Grassi Davide , Mura Alessandro , Adriani Alberto , Sindoni Giuseppe , Plainaki Christina , Tosi Federico , Olivieri Angelo , Piccioni Giuseppe , Scarica Pietro , Biagiotti Francesco , Bolton Scott
Published: February 2023

The Jupiter InfraRed Auroral Mapper (JIRAM) instrument on board the Juno spacecraft performed multiple observations of the Jupiter North Equatorial Belt (NEB) around the time of 12th Juno pericenter passage on April 1st 2018. The data consist in thermal infrared images (the JIRAM filter has a band pass centred around 4.8 μm) and show, among other atmospheric features, two bright hot-spots.Images of the same areas at different emission angles were used to constraint the trend of the limb darkening function.Comparison against simulated observations computed for different emission angles, total opacities, single scattering albedo ω0 and asymmetry parameter g suggest that ω0 ~ 0.9 and g ~ 0.32 provide best match with data, with the latter parameter only weakly constrained by JIRAM observations. Then, we computed the ω0 and g resulting from different size distributions (exploring the effective radius reff and variance v space), taking into account the complex refractive indices of ammonium hydrosulphide by [1] and [2].Our analysis suggests that neither sets of refractive indices are consistent with JIRAM observations. A more reasonable agreement is found once tholines are adopted, with an effective radius of 0.6 μm. This value is broadly consistent with the mean radius of Hot Spot’s particles estimated by [3] on the basis of Galileo Entry Probe data. While a composition of pure tholine is not realistic for Jupiter conditions, our results indicate that scattering properties of clouds are largely dominated by optical properties of contaminants, as already suggested in [4]. Indeed, a thin (0.01 of total radius) coating of such compound over a NH4SH particle can effectively mask the optical properties of the latter. An effective radius of 0.4 μm for these coated particles produces the ω0 and g derived from JIRAM data. [1] Howett C. J. A. et al., (2007) J. Opt. Soc. Am. B 24, 126-136.[2] Ferraro J. R et al. (1980) Applied Spectroscopy, 34 (5), 525-533.[3] Ragent B. et al, (1998), J. Geophys. Res., 103 (E10), 22891– 22909.[4] Grassi D. et al. (2021) MNRAS, 503(4), 4892-4907. This work was supported by the Italian Space Agency through ASI-INAF contract 2016-23-H.1-2018.
The effect of permeability on the pressure regime in 2D outcrop-to-outcrop submarine hydrothermal flow models
Authors: Kremin Isabel , Guo Zhikui , Rüpke Lars
Published: February 2023

The significant discrepancy between the observed conductive heat flow and predictions by thermal models for oceanic lithosphere younger than 50 Ma is generally interpreted to result from hydrothermal circulation between basement outcrops. Numerical simulations of fluid flow between such outcrops performed in previous studies revealed that establishing horizontal pressure gradients to sustain a hydrothermal siphon requires high aquifer permeabilities and a contrast in the outcrops’ transmittance, which is the product of the outcrop permeability and the area of outcrop exposure. However, most previous studies focused on the model parameters needed to sustain a hydrothermal siphon, while the physical processes that create the horizontal pressure gradients in the first place remain poorly constrained. In order to shed more light on the physics behind outcrop-to-outcrop flow, a simple synthetic 2D model of two outcrops connected by a permeable aquifer was set up. Fluid flow modelling was done by using hydrothermalFoam, a hydrothermal transport model, that is based on the open-source C++ computational fluid dynamics toolbox OpenFOAM. Our initial simulations focus on variations of the permeability of the outcrops and the aquifer. The results reveal two key points that are essential to generate a flow: First, the outcrops permeability has a fundamental effect on its average pressure. High permeabilities lead to a rather "cold" hydrostatic pressure regime with lower temperatures and hence higher average pressures. Lower outcrop permeabilities are accompanied with a rather "warm" hydrostatic pressure regime characterized by higher temperatures and lower average pressures. Secondly, fluid convection in the aquifer is necessary to establish a siphon flow. Therefore, the aquifer permeability must be sufficiently high to overcome Darcy resistance and yet low enough to prevent the flow from being solely diffusive.
NDVI time series filling over wheat fields using the Sentinel-1 data
Authors: Ayari Emna , Kassouk Zeineb , Lili-Chabaane Zohra , Ouaadi Nadia , Baghdadi Nicolas , Zribi Mehrez
Published: February 2023

The Normalized Vegetation Different Index (NDVI) has proved its relevance to describe crop dynamics with a high spatial resolution. Therefore, it’s widely used to monitor and describe vegetation in different agronomic applications such as land use classification, yield forecasting, and biophysical variables’ estimation. As an optical index, the NDVI is limited by weather conditions where the cloud presence impacts the pixel information. In the present study, we retrieve the NDVI values according to wheat growth stages using the normalized polarization ratio (IN) and the estimated coherence in Vertical-Vertical polarization from C-band Sentinel-1 radar data. To estimate the NDVI values, we used empirical equations and the machine learning algorithms such as the support vector regressor (SVR) and random forest (RF). During the two years from 2018 to 2020, we divided the wheat cycle into two periods. The first period is extended between the sowing and heading event. The second one covers physiological maturity which is subdivided into two sub-periods where the NDVI values are lower or higher than 0.4. For the first period, the NDVI estimation is characterized by root mean square of error (RMSE) values varying between 0.07 and 0.1. When the NDVI values are lower than 0.4 through the senescence phase, the RMSE values are lower than 0.06. Throughout the grain maturity (NDVI ≥ 0.4), the RMSE values exceed 0.19 using the calibrated empirical equation as a function of IN against a moderate performance characterizing the use of machine algorithms with the IN and as features. The developed approach to estimate the NDVI according to the wheat development stage was tested on several fields. The overall RMSE values vary between 0.12 and 0.19 with a correlation coefficient fluctuating between 0.64 and 0.87 and a bias value ranging between -0.06 and -0.02. The combination of the radar variables improved the NDVI estimations during the wheat cycle. The developed approach can be tested on other crops and climatic contexts.
Years of deep magmatic upheaval preceding the 2021 eruption at Fagradalsfjall, Iceland
Authors: Kahl Maren , Mutch Euan J.F. , Maclennan John , Morgan Dan , Couperthwaite Fiona , Bali Enikő , Thordarson Thor , Guðfinnsson Guðmundur H. , Walshaw Richard , Buisman Iris , Buhre Stephan , van der Meer Quinten H. A. , Caracciolo Alberto , Marshall Edward W. , Rasmussen Maja B. , Gallagher Catherine R. , Moreland William M. , Höskuldsson Ármann , Askew Robert A.
Published: February 2023

Effective eruption forecasting and volcanic hazard management depend heavily on our ability to detect when a volcanic system switches from a state of unrest into a state of eruption. The 2021 eruption at Fagradalsfjall in SW Iceland, the first deep-sourced eruption on a mid-ocean ridge system monitored with modern instrumentation, presents an ideal opportunity to compare geophysical and petrological datasets to explore processes of deep magma mobilisation and eruption priming. Here we use diffusion chronometry to show that deep magmatic unrest in the roots of volcanic systems can precede apparent geophysical eruption precursors by a few years.  Early phases of magma accumulation and reorganisation in the near-Moho plumbing system, part of the priming for eruption, can occur in the absence of significant increases in shallow seismicity (<7 km depth) or rapid geodetic changes. In contrast, geophysical signals of unrest and crystal records of changing magmatic conditions both show significant increases in intensity in the months and days prior to eruption. This correlation may signal a rapid transition from a state of priming to full scale mobilisation in which magma begins to traverse the upper/ brittle crust. Our findings provide new insights into the dynamics of near-Moho magma storage and mobilisation. 
Largest aftershock nucleation driven by afterslip during the 2014 Iquique sequence
Authors: Itoh Yuji , Socquet Anne , Radiguet Mathilde
Published: February 2023

Megathrust faults are known to host both seismic and aseismic slip. Laboratory experiments and numerical simulations have demonstrated that seismic-aseismic interaction can be involved in the earthquake source process such as nucleation and termination. However, models of seismic-aseismic interaction regarding the source process are still controversial because their observational evidence is limited to the small number of events among instrumentally recorded earthquakes. This is likely due to the low signal-to-noise ratio of observations and/or short duration of the nucleation and termination processes. In this study, we newly report aseismic slip accompanying intriguing seismicity during the 2014 Iquique earthquake sequence by analysing seismicity and high-rate GPS crustal deformation data.We document early postseismic deformation during the 3 days following the M 8.1 mainshock and demonstrate that afterslip started immediately after the mainshock and led 27 hours later to the M 7.6 largest aftershock which located ~120 km further south. The interevent afterslip peaks down-dip of the mainshock with decaying moderate aftershock rate, exhibiting typical postseismic megathrust response. A local peak of the afterslip is inferred between the mainshock and the largest aftershock epicentres. This local peak suggests that this area acted as an aseismic barrier to the southward mainshock rupture propagation so that the two big quakes did not occur simultaneously.The geodetic moment everywhere decreased with time during the 27h interevent stage with different decaying rate. The decay was slower in the afterslip area between the two epicentres than the main down-dip peak. Interestingly, the seismicity rate and associated moment release in this area increased with time during the interevent 27 hours. We propose that the largest aftershock nucleation was driven by the afterslip. Contrary to predictions of some numerical simulation models, our result implies that aseismic slip during the nucleation process does not necessarily accelerate. Our new observational discovery illuminates the mechanical connection between sequential great earthquakes mediated by aseismic slip.
MJO-related China rainfall teleconnections in the MetUM
Authors: Carvalho Maria Joao , Xavier Prince , Furtado Kalli
Published: February 2023

During a Madden-Julian Oscillation (MJO) event, anomalous convection triggers a dynamical response with anomalous large-scale ascent and upper-tropospheric divergence outside the tropics creates interaction between the MJO and the extratropical weather, modes of global circulation and climate variability. The MJO is known to have an impact on China rainfall and regional circulation with enhanced/ suppressed rainfall in South China during the propagation of the MJO from the Indian Ocean into the western Pacific. As the MJO is considered a major source of predictability at subseasonal time scales, it is important to understand how climate models are representing the MJO and its remote effects. This study is aimed to investigate the modelled MJO and associated local effects in China precipitation using the Met Office Unified Model (MetUM). It was found that the response of the rainfall over South China is asymmetric, with the enhancement of rainfall during the Indian Ocean convective phases (phase 2) of the MJO being much stronger than the suppression during the west Pacific phases (phase 6). This response signal was mostly due to the increase in probability of extreme precipitation events rather than the increase in number of rainy days. Analysis of the modelled MJO and associated response shows, although the MJO is more realistically represented in the atmosphere-ocean coupled simulation, the atmosphere-only simulation showed more evidence of MJO-related remote effects in the rainfall patterns over China. The ocean-coupled simulation shows no significant response to the propagation of MJO-associated convection whereas the atmosphere-only simulation shows the correct pattern of enhancement and suppression of rainfall and associated regional circulation pattern changes. The differences found in the representation of remote effects between atmosphere-only and ocean-coupled simulations may be attributed to the air-sea interaction processes and to fundamentally different mean-state biases which affect not only the representation of the MJO but also the propagation of MJO-induced Rossby waves. 
Air Pollution from Agriculture: Using Satellite Observations to Study Ammonia Emissions
Authors: Iorga Adriana , Harrison Jeremy , Moore David
Published: February 2023

Ammonia (NH3) is one of the most common nitrogen gas species and pollutants present in the lower troposphere. Ammonia enters the atmosphere through volatilisation from soils through the usage of nitrogen-based fertilisers in agriculture [1]. Because of its short lifetime (up to a few hours) [2], ammonia is highly reactive and can react chemically with acids in the atmosphere to form fine particulate matter (PM2.5), playing an important role in secondary aerosol formation [3]. Wet and dry deposition of ammonia on soils and water bodies has shown to be detrimental to ecosystem biodiversity as it leads to acidification of the environment [3]. Therefore, observations of ammonia are essential for establishing air quality and environmental regulations for agricultural practices.By using combined satellite measurements from the Infrared Atmospheric Sounding Interferometer (IASI) and the Cross-track Infrared Sounder (CrIS) instruments, we aim to study trends and the diurnal cycle of ammonia on regional scales, particularly in areas subjected to intensive agricultural activity, such as the Indo-Gangetic Plain (northern India). This research makes use of an optimal estimation-based method of monitoring ammonia with satellites called the University of Leicester IASI retrieval Scheme (ULIRS).References:[1] Van Damme M. et al (2021), Environ. Res. Lett., 16 055017[2] Dammers E. et al (2019), Atmos. Chem. Phys., 12261–12293[3] Erisman, J. W. et al (2007), Environ. Pollut., 150, 140– 149
Modeling clod evolution under rainfall according to clod size.
Authors: Vannier Edwige , Dusséaux Richard
Published: February 2023

Determing soil spatial variability is a key point in soil sciences either for soil preparation in precision agriculture, or because of influence on overland flow and erosion. Soil Surface Roughness (SSR) represents the undulation of the surface at small scale, due to the presence of small elevations and depressions. It results from tillage operations and changes over time due to weathering. SSR can be related to clod-size distribution. So, many research has been conducted on monitoring the size and number of clods using photogrammetry method. Nowadays, it is possible to acquire high resolution Digital Elevation Models (DEMs). This study seeks to model the evolution of clod size under rainfall impact with modeling and data processing tools.Seedbed-like soil surface was made in the laboratory by filling a tray with loose soil of silt loam and setting upon pre-sieved clods. It was eroded by controlled laboratory rainfalls. A millimeter DEM was recorded at each stage of the surface with laser-scanner. Wavelet-based clod segmentation leaded to measurement of the volume of individual clods. Clod subsets were formed according to clod size. Normalized mean volume decrease was modelled by exponential function.Greater clods showed swelling (volume increase) and erosion (volume decrease), with cumulated rainfall. These two phenomena being size dependent. Amplitude and slope parameters of the exponential decrease of clod volume could be modelled as a function of mean volume of the clod subset at initial stage. Results obtained with this surface strengthen those previously obtained with less data and basic segmentation. A power law is confirmed for amplitude parameter and a sigmoïd function is highlighted for slope parameter.Modelling and data processing tools are efficient to differentiate and estimate the dynamics of clods depending on their size. Usually, clod size distribution is addressed with statistics of clod diameters obtained by real or numerical sieving. Working on 2.5 D DEMs gives also an acces to the vertical dimension of clods, which is included in their volume. This technique completes the usual roughness description and is promissing for use in precision agriculture or numerical surface generation.
Southeastern Tibetan Plateau growth revealed by inverse analysis of landscape evolution model
Authors: Yuan Xiaoping , Jiao Ruohong , Dupont-Nivet Guillaume , Shen Xiaoming
Published: February 2023

The Cenozoic history of the Tibetan Plateau topography is critical for understanding the evolution of the Indian-Eurasian collision, climate, and biodiversity. However, the long-term growth and landscape evolution of the Tibetan Plateau remains ambiguous, it remains unclear if plateau uplift occurred soon after the India-Asia collision in the Paleogene or later in the Neogene. As the landscape evolution is controlled mainly by mountain uplift and surface processes, the present-day river profiles and the drainage basin geometries preserve important information that can be extracted to infer the long-term history of mountain uplift with numerical models. Here we focus on the southeastern (SE) Tibetan Plateau where three of the world’s largest rivers draining the Tibetan Plateau (the Yangtze, Mekong, and Salween Rivers, i.e., Three Rivers) have incised deep valleys with distinctive geomorphic signatures. We reproduce the uplift history of the SE Tibetan Plateau using a 2D landscape evolution model, which simultaneously solves fluvial erosion and sediment transport processes in the drainage basins of the Three Rivers region. Our model was optimized through a formal inverse analysis with a large number of forward simulations, which aims to reconcile the transient states of the present-day river profiles. The modeling results were ultimately compared to existing thermochronologic and paleoelevation datasets to help decipher between competing tectonic models that predict contrasting topographic evolutions. Our results suggest initially low elevations during the Paleogene, followed by a gradual southeastward propagation of topographic uplift of the plateau margin until present day. The modeling thus does not support Paleogene formation of the SE Tibetan Plateau with a major subsequent degradation via upstream fluvial erosion. The scenario with pre-existing high-elevation plateau or plateau degradation will result in much wider river channels with knickpoints that propagated upstream much further away from the plateau margin compared to observed river profiles. The quantitative constraints on landscape evolution achieved based on drainage patterns in SE Tibet indicate a powerful tool potentially applicable to other regions to infer important implications for the evolution of Indian-Eurasian collision, Asian monsoons, and biodiversity, as well as the geodynamic forces involved in collisional orogens.
Cenozoic tectonic evolution of the Beaufort-Mackenzie fold and thrust belt (Arctic Canada): from orogenic shortening to gravity spreading
Authors: Pinet Nicolas , Duchesne Mathieu J. , Brake Virginia
Published: February 2023

The Beaufort-Mackenzie fold and thrust belt in Arctic Canada corresponds to the offshore part of the Cordilleran orogen in Yukon and Alaska. The main folds are associated with thrusts that root in a basal décollement at depths of ca. 12-15 km. Deformation mainly occurred prior to the deposition of the Richards sequence (late Eocene) and subsequent folding that progressed basinward and continued episodically to the present accounts for < 10% of the total shortening. In the shelf region, normal faults dipping either seaward or landward are located on the apex of anticlines. Detailed analysis on seismic sections of the variations of throw (T) and expansion index (Ei) with depth (z) indicates that despite the clear spatial relationship with anticlines, normal faults initiated after fold development. Normal faulting migrated seaward during the Oligocene to Pliocene (and possibly later) along with the shelf edge that resulted from the progradation of thick sedimentary wedges of clastic sediments. This strongly suggests that normal faulting is not related to tectonics (i.e., linked with the building of the Cordillera), but to gravity spreading due to high sedimentary loading in the Mackenzie delta; i.e. main depocenter for sediments originating from the northeastern Cordillera since the latest Cretaceous. The superimposition of extensional structures on an existing fold and thrust belt shows the complex interplay in time and space between far-field stresses linked with plate-dynamics and stresses associated with sedimentary loading in a delta setting. 
Detachment-parallel recharge explains high discharge fluxes at the TAG hydrothermal field-Insights from 3D numerical simulation
Authors: Guo Zhikui , Rüpke Lars , Tao Chunhui
Published: February 2023

The Earth System appears increasingly interconnected and hydrothermal discharge at back smoker vent sites is not only visually appealing, it also sustains unique ecosystems, generates large polymetallic sulfide deposits, and modulates ocean biogeochemical cycles. At slow spreading ridges, fault zones seem to provide stable preferential fluid pathways resulting in the formation of the ocean’s largest sulfide deposits. The TAG hydrothermal mound at 26°N on the Mid-Atlantic Ridge (MAR) is a typical example located on the hanging wall of a detachment fault. It has formed through distinct phases of high-temperature fluid discharge lasting 10s to 100s of years throughout at least the last 50,000 years and is one of the largest sulfide accumulations on the MAR. Yet, the mechanisms that control the episodic behavior, keep the fluid pathways intact, and sustain the observed high heat fluxes of possibly up to 1800 MW remain poorly understood. Previous concepts involved long-distance channelized high-temperature fluid upflow along the detachment but that circulation mode is thermodynamically unfavorable and incompatible with TAG's high discharge fluxes. Here, based on the joint interpretation of hydrothermal flow observations and 3-D flow modeling, we show that the TAG system can be explained by episodic magmatic intrusions into the footwall of a highly permeable detachment surface. These intrusions drive episodes of hydrothermal activity with sub-vertical discharge and recharge along the detachment. This revised flow regime reconciles problematic aspects of previously inferred circulation patterns and allows to identify the prerequisites for generating substantive seafloor mineral systems.
Hydrological response to anthropogenic activities and climate change in the southern Caspian Sea, Iran
Authors: Sharifi Garmdareh Alireza , Torabi Haghighi Ali , Patro Ritesh
Published: February 2023

Rivers play a vital role in supplying fresh water for various sectors. During the last decades, increasing anthropogenic activities and climate change have altered river flow regimes around the globe. Rivers flow in the southern Caspian Sea in Iran has altered due to water-intensive socio-economic development and climate change. To assess and quantify the impact of anthropogenic activities and climate change on river flow regimes, the elasticity-based methods and the Budyko hypothesis were applied to 40 rivers on the closest gauges to the Caspian Sea were selected. Furthermore, to evaluate spatial/temporal change in hydrometeorological variables, two non-parametric methods, including the modified Mann-Kendall method (MK3) and Innovative Trend Analysis (ITA), were applied. The results showed an alarming trend of increasing temperature and potential evapotranspiration and decreasing rivers’ flow in the southern Caspian sea. Assessing and quantifying the impact of anthropogenic activities and climate change on river flow alteration indicated that anthropogenic activities (accounting for 83.3%) played a dominant role in river flow alteration that led to inflow to the Caspian Sea decline by about 2,412 MCM annually. In addition, the inflow to the Sea has decreased by about 551 MCM every year due to the impact of climate change. Decreasing the inflow to the Caspian Sea can accelerate the declining trend of the Sea level, which leads to boosts eutrophication conditions in the Sea, and negatively affect the ecosystem and economics of the Caspian Sea. Therefore, an appropriate adoption approach must be taken into account to alleviate the environmental and socio-economic issues in the southern Caspian Sea.
Recreation impact on establishment of dune building species
Authors: van Rosmalen Sasja , Homberger Jan-Markus , Riksen Michel , Limpens Juul
Published: February 2023

Sandy shores serve a multitude of purposes; they protect the inland from flooding, support a high biodiversity, and are recreation hotspots. To what extent these functions can coexist or are mutually exclusive is unclear, especially given increasing stressors such as rising sea levels and urbanization. Knowledge on the trade-offs between these functions is important when designing these areas and nature-based solutions to ensure the desired results. We investigated the effect of recreational pressure on the establishment of two common dune building grass species (Ammophila arenaria and Elytrigia juncea). We conducted a field introduction experiment with seeds and rhizomes of both species along increasing distance to a beach entrance. We established a total of 300 plots, following a randomised block design with 4 factorial treatments (species * type diaspore) and 60 replicates for two beaches on the Dutch barrier Island of Terschelling. Plant material was collected from the wild, using local genetic material. Plant seeds were left in their husk to mimic natural dispersal. Plots were georeferenced by means of Real Time Kinematic and left unmarked to enable undisturbed recreation.  

Recreation pressure was assessed by counting the number of people at different beach sections, confirming that anthropogenic pressure increased with distance to the beach entrance. Establishment success was monitored by counting the number of emerged seeds and sprouted rhizomes per plot at regular intervals across the growing season. To control for drivers other than recreation pressure, we also monitored environmental variables, such as the change in beach level. Preliminary results suggest that environmental factors such as erosion and burial are limiting the establishment success for all treatments. Moreover, a positive effect of distance from the entrance on the establishment success of both species can be observed. This is especially clear within the first 100 meters. The strongest effect seems to be for Ammophila arenaria. These preliminary results indicate that both sediment dynamics and recreational pressure play a role in the new establishment of these species on the upper beach. This means that the impact of both should be considered when designing sandy coastal areas. 