bluuebunny/crossref_metadata_2025 huggingface dataset:
Surface reaction kinetics of volcanic materials at hydrothermal conditions – an in-situ experiment at the Surtsey volcano
Authors: Peter Mathias , Bach Wolfgang , Kahl Wolf-Achim , Luttge Andreas , Turke Andreas , Jorgensen Steffen Leth
Published: March 2020

Surface reaction kinetics of volcanic materials at hydrothermal conditions – an in-situ experiment at the Surtsey volcano

The diversity and functioning of microbial life is a key research topic in the field of marine geochemistry and geobiology. For understanding biological processes at the temperature limit of functional life, it is necessary to gain insights about microbe-rock-fluid interactions under natural hydrothermal conditions within the basaltic ocean crust. Although there has been research in the field of biological interactions on olivine and tephra surface in laboratories and samples from volcanos ([1], [2]), the kinetics of microbe-rock-fluid interactions has not been systematically evaluated by in-situ experiment in a natural reservoir.

During the ICDP SUSTAIN Expedition 5059 at the Surtsey volcano off the southern coast of Iceland in 2017, a borehole was endowed with a subsurface observatory to analyze the evolution of olivine (Fo90) and volcanic glass surfaces embedded in PEEK containers at fixed temperatures ranging from 25°C to 125°C for two years ([3]). This incubation experiment delivers novel data of surface reaction kinetics under defined conditions in a natural setting.

In-depth analysis of the sample surface with vertical scanning interferometry, atomic force microscopy as well as Raman spectrometry provides insights into solid-fluid reactions of volcanic minerals. On the one hand, this analysis delivers a quantitative and qualitative breakdown of the chemical and physical alteration of natural matter below the oceanic crust. On the other hand, the in situ experiment facilitates a validation of a range of experiments that have been performed in laboratories under similar conditions. The possibility to gain knowledge about dissolution and precipitation on the interface of common seafloor materials within a natural hydrothermal system is critical step towards understanding submarine microbial life.

 

[1] Konhauser, K. O., Schiffman, P., and Fisher, Q. J., Microbial mediation of authigenic clays during hydrothermal alteration of basaltic tephra, Kilauea Volcano, Geochem. Geophys. Geosyst., 3( 12), 1075, doi:10.1029/2002GC000317, 2002.

[2] Malvoisin, B., Brunet, F., Carlut, J., Rouméjon, S., and Cannat, M. (2012), Serpentinization of oceanic peridotites: 2. Kinetics and processes of San Carlos olivine hydrothermal alteration, J. Geophys. Res., 117, B04102, doi:10.1029/2011JB008842.

[3] Türke, A., et al. (2019). "Design of the subsurface observatory at Surtsey volcano, Iceland." Sci. Dril. 25: 57-62.
Considerations on Parameter and State Estimation with Ensemble Data Assimilation Methods – A Case Study with a Nonlinear Oscillator
Authors: Banerjee Arundhuti , Vossepoel Femke
Published: March 2020

This study investigates the effect of erroneous parameter values for state and parameter estimation using data assimilation. The numerical model chosen for this study solves the van der Pol equation, a second-order differential equation that can be used to simulate oscillatory processes, such as earthquakes. In the model, discrepancies in the parameter values can have a significant influence on the forecasted states of the model, which is even more significant if its behaviour is highly nonlinear. When observations of the state variables are assimilated to update the parameters along with the state variables, this improves the quality of the state forecasts. The results suggest that corrections in the model parameter not only recover the actual parameter values but also reduce state-variable errors after a certain time period. However, data assimilation that updates the state variables but not the parameter can lead to erroneous estimates as well as forecasts of the oscillation. Since the study is performed on a simplified nonlinear model framework, the consequences of these results for data assimilation in more realistic models remains to be investigated.
Explicit inclusion of connectivity in geostatistical facies modelling.
Authors: Manzocchi Tom , Walsh Deirdre , Marcus Carneiro , López-Cabrera Javier , Kishan Soni
Published: March 2020

Irrespective of the specific technique (variogram-based, object-based or training image-based) applied, geostatistical facies models usually use facies proportions as the constraining input parameter to be honoured in the output model. The three-dimensional interconnectivity of the facies bodies in these models increases as the facies proportion increases, and the universal percolation thresholds that define the onset of macroscopic connectivity in idealized statistical physics models define also the connectivity of these facies models. Put simply, the bodies are well connected when the model net:gross ratio exceeds about 30%, and because of the similar behaviour of different geostatistical approaches, some researchers have concluded that the same threshold applies to geological systems.

In this contribution we contend that connectivity in geological systems has more degrees of freedom than it does in conventional geostatistical facies models, and hence that geostatistical facies modelling should be constrained at input by a facies connectivity parameter as well as a facies proportion parameter. We have developed a method that decouples facies proportion from facies connectivity in the modelling process, and which allows systems to be generated in which both are defined independently at input. This so-called compression-based modelling approach applies the universal link between the connectivity and volume fraction in geostatistical modelling to first generate a model with the correct connectivity but incorrect volume fraction using a conventional geostatistical approach, and then applies a geometrical transform which scales the model to the correct facies proportions while maintaining the connectivity of the original model. The method is described and illustrated using examples representative of different geological systems. These include situations in which connectivity is both higher (e.g. fluid-driven injectite or karst networks) and lower (e.g. many depositional systems) than can be achieved in conventional geostatistical facies models.
Seismic Hazard Assessment and Numerical Modeling for Seismic Microzonation purpose of Dushanbe, Tajikistan
Authors: Hakimov Farkhod , Havenith Hans-Balder , Ischuk Anatoly , Pilz Marco , Reicherter Klaus
Published: March 2020

Seismic hazard assessment of urban areas is an important and extremely challenging task. It is so important because without the knowledge of the influence of local soil conditions and properties, of the changing layer thickness in urban areas, and without considering multiple possible scenario earthquakes for this territory, engineers do not have enough information on how to design and construct seismically safe buildings. The particular challenge of this task is due to the great uncertainty affecting the prediction of the spatially (and sometimes even temporally) changing seismic properties of soils with respect to urban development.
Dushanbe is the capital of Tajikistan, a mountainous country marked by high to very high seismic hazard. The reason for the high seismic hazard specifically near Dushanbe is related to its location between two fault systems: South Gissar fault and Ilek-Vaksh fault.  Estimation of the seismic hazard of the urban areas in Tajikistan is very important because they had developed in a very short time and many high buildings are being constructed now Existing seismic action estimations are based on the old approaches when the main factors of the local soil conditions only consider general engineering-geological features of the territory as well as macro-seismic observations data. An additional problem is the building code in Tajikistan; it uses the estimation of the ground motions in terms of the MSK-64 scale, but does not enough take into account the variety of the soil conditions in the Dushanbe city area. Existing seismic hazard estimation of the area of Tajikistan is based on the so-called “The map of general seismic zoning of the territory of Tajikistan”, that was produced in 1978 in terms of MSK-64 scale. The seismic microzonation map of the Dushanbe city area was made in 1975 in terms of MSK-64 scale as well and was based on the engineering-geological approach mostly. This map does not represent the highly variable soil conditions of the Dushanbe city area which are partly due to the anthropogenic influence of the large city. Therefore, earlier seismic zonation maps assigned an intensity of IX to most districts of the city. However, those previous studies did not sufficiently quantify the local effects of soils on the seismic hazard, mainly the macro-seismic conditions (the relative distance of districts to fault lines) were considered for the zonation. 
This study describes and implements a number of new approaches to the evaluation of maximum seismic impact and site effect values. 
Benchmark of multiple geophysics tools to study the voids in the upper levels of a decommissioned iron mine
Authors: Bouteille Simon , Bitri Adnand , Dietz Michel , Gance Julien
Published: March 2020

Absorption muon imaging is a technique that can measure density variations underground down to a few hundred meters. Then, it can prove to be useful in a mining environment: to help assess the ore bodies volumes and/or to monitor the underground for natural hazards that can happen at the surface because of the mining exploitation. Here we report the result of an experiment designed to test the capabilities and resolution power of a cosmic muon measurement in a mining environment compared to other standard geophysics tools: gravimetry and seismic studies. It consists of three independent measurement of a subset of the decommissioned iron mine of May-sur-Orne (France). The first one was made using a 50x50cm² micromegas based muon telescope installed at the deepest non-submerged level (50m underground) during 3 months. The second one is a gravimetry survey of the surface area inside the muon telescope acceptance cone. And the third one is a study of refracted and reflected seismic waves along a single line above the muon telescope location. The investigation volume was chosen because of the presence of surface risks (neighborhood), the unknown of some uncharted volume and the presence of an ore storage volume of several meter cubed that was used during the mine exploitation and which filling state is unknown.

The data analysis showed that while muon tomography is able to detect the negative density anomaly of the storage volume, the gravimetry measurement is not sensible to it. However, the seismic study was able to detect the volume as well and its location and extension is compatible with the muon measurement.
Synrift subsidence and magmatism of the Central South Atlantic passive margins based on long term 2-D thermo-mechanical modelling
Authors: Theunissen Thomas , Huismans Ritske , Despinois Frank , Ringenbach Jean-Claude , Sapin François
Published: March 2020

Here we use observations from the central South Atlantic conjugate margins to constrain the structural style of rifting and its relation with sedimentary basin evolution during the syn and early post-rift. Three synthetics transects from North (Gabon-Brazil) to South (Angola-Brazil) are used to constrain fault distribution, margin width, crustal thickness, distribution of magmatism, syn-rift sedimentary section thickness and paleo-environment from the start of rifting in the Berriasian (145 Ma) until the early post rift in the Aptian (113 Ma). This integrated study aims to understand variations in along strike structural style, magmatic output, and sedimentary basin evolution to assess the contribution of mantle processes on topography using forward 2-D thermo-mechanical modelling. We design a model setup that reproduces South Atlantic central segment main characteristics before rifting. We then explore scenarios of lithospheric thinning where strain weakening mechanisms, degree of depletion of lithopsheric mantle and crustal rheology are the main variables. The model accounts for decompression melting with feedbacks on temperature, viscosity and density of the mantle. The subsidence in the thermo-mechanical models is calibrated with a reference ridge elevation, where a 6 km thick oceanic crust is predicted, and explained by the different contributions on buoyancy of rifted passive margin during rifting. We discuss conditions to get magma-poor margins with/without exhumed mantle at the seafloor and conditions to reach a small topographic gradient and shallow water environment between the proximal and distal domains over more than 200 km of the wide margin during most of the syn-rift.
Assessment of cereal production and food security under climate change in the Euro-Mediterranean Region
Authors: Mereu Valentina , Costa Saura José Maria , Trabucco Antonio , Spano Donatella
Published: March 2020

Future climate projections indicate a northward shift of suitable agricultural areas with a potential intensification of cropping systems in northern Europe, and a decrease in crop productivity in southern Europe mainly due to extreme temperatures and reduction in precipitation and water availability. Furthermore, the uncertainty in projecting climate change impacts on agricultural productivity at the regional scale affects the choice of appropriate adaptation strategies.

The main objective of this study is to assess the potential risk for cereal production and food security in the Euro-Mediterranean area and North Africa due to climate change, integrating multiple factors. Simulations were carried out using the CSM-CERES-Wheat and CSM-CERES-Maize crop models implemented in the DSSAT (Decision Support System for Agrotechnology Transfer) software. A spatially distributed routine integrating DSSAT with large geodatasets characterizing the environment (climate and edaphic) conditions and management options (e.g. agronomic practices, irrigation, fertilization) was applied to perform the simulation of grain yield for durum wheat, common wheat, and maize in each grid cell. An ensemble of climate projections from ISIMIP (Inter-Sectoral Impact Model Intercomparison Project) were used as input to the crop models. The uncertainty and model agreement of projected changes in crop yield, under current and future CO2 values (according to RCP8.5) were evaluated and new potential and high risk areas for cereal production were identified. Moreover, socio-economic indicators were considered to evaluate the exposure and adaptive capacity of the system and estimate the potential risk for cereal production. The result is a four dimensions single map that combine the selected variable and indices. Results show a potential decrease in cereal production per capita in the west Mediterranean area, North Africa and Turkey. However, the potential risk differ across these regions, according with the adaptive capacity of each area. Results also show a potential increase in cereal production per capita in north eastern Europe. Overall, there is high agreement across models.
Assessing sediment transport energetics with instrumented particles for above threshold of motion turbulent flows
Authors: Al-Husban Zaid , Valyrakis Manousos
Published: March 2020

Despite the fact sediment transport has been studied for decades, there is still a need to gain a further insight on the nature and driving mechanisms of bed particle motions induced by turbulent flows, for the low transport stages where the particle transport is relatively intermittent. A custom designed and prototyped instrumented particle, embedded with inertial sensors is used herein to study its transport over hydraulically rough bed surfaces. The calibration and error estimation for its sensors is also undertaken before starting the experiments, to ensure optimal operation and estimate any uncertainties.

The observations and results of this research are obtained from experiments carried out at the University of Glasgow 12 meters long and 0.9 meters wide, tilting and water recirculating flume. The flume walls comprise of smooth transparent glass that enables observing particle transport from the side (also with underwater video cameras) and the bed surface generally is layered with coarse gravel.

The particle is initially located at the upstream end of the test configuration, fully exposed to the uniform and fully developed turbulent channel flow. The top and side cameras are set in their suitable positions to monitor and study the behaviour of particle motion by capturing the dynamical features of sediment motion and to not interfere with flow field that pushes particle downstream. 

Using the sensor data to calculate the kinetic energy for a range of sets of sediment transport experiments with varying flow rates and particle densities, the probability distribution functions (PDFs) of particle transport features, such as particle’s total energy, are generated which give information about particle interaction with the surface bed during its motion. In addition, the effects of different flow rates, particle densities on particle energy are assessed.
On the design of the dewatering system of a large excavation in Barcelona (Spain) used for the construction of the high speed train tunnel
Authors: Pujades Estanislao , Jurado Anna , Carrera Jesús , Vàzquez-Suñé Enric
Published: March 2020

Underground constructions in urban environments are more and more frequent, and usually, they are undertaken below the water table. The interaction between groundwater and underground constructions is a relevant topic that has to be carefully considered because unforeseen incidents may appear during these constructions. This paper shows the methodology used to design the dewatering system of a large excavation below the water table in a high populated urban area. The excavation was required for the construction of the assembly shaft of the tunnel boring machine that was used to excavate the high speed train tunnel below Barcelona (Spain). This methodology was useful to design an efficient dewatering systems that allowed constructing the assembly shaft in safe conditions and without producing appreciable impacts around the construction site. The most important step of the proposed method was the hydrogeological characterization of the soil because this allowed building a realistic and representative numerical model. This work shows the importance of interdisciplinary approach because the dewatering system was designed combining field work, classical analytical solutions and numerical methods.
Changes in soil quality indices at different land uses in Semirom area
Authors: Chavoshi Borujeni Sattar , Chavoshi Elham , Nouri Hamideh
Published: March 2020

Background and Objectives: Assessment of soil quality indices is important for identifying the effect of land use on soil function. Soil organic matter (SOM) is a major indicator of soil quality due to its capacity in affecting soil structure by enhancing aggregation. The aim of this study was to quantify the soil quality changes in pasture and agricultural lands around the Semirom city.

Materials and Methods: The study was conducted in a completely randomized design with five different levels including pastures, orchards, rain fed farming, irrigated cultivations of wheat and barley with 6 repetitions. A composite random soil sampling was done from the depth of 0-15 cm. Soil properties such as electrical conductivity (EC), pH, wet aggregate stability, particulate organic matter (POM), soil organic carbon (SOC) and carbohydrates were measured in each land use.

Results: The results showed that organic carbon (OC) and particulate organic carbon (POC) increased significantly in irrigated cultivation as compared to pasture. However particulate organic carbon was lower in rain fed farming compared with pasture. POC content were at least 2 times greater than those values in pasture and rain fed wheat farmlands. The highest carbohydrate amounts were observed in the irrigated wheat field (2 g kg-1) while the lowest values were belonged to the rain fed wheat cultivations (0.94 g kg-1). The content of carbohydrate had an increase of 40% in irrigated wheat field and a decrease of 50% in rain fed wheat field compared with pasture.The orchard and irrigated wheat and barley land uses had the highest mean weight diameter (MWD) of soil aggregates and the lowest values were obtained in the rain fed wheat and barley farming.

Conclusion: Overall, the survey results indicate a better soil quality of the orchards and irrigated farmlands, whereas the rain fed farmlands had more feeble soil quality as compared to other investigated land uses. Particulate organic carbon and carbohydrate showed greater sensitivity to land use changes. Therefore, these parameters are better indicators as compared to other investigated indicator for evaluating soil quality in the studied area.
Enhancing Precipitation Prediction Algorithm by Data Assimilation of GPM Observations
Authors: Miyoshi Takemasa , Kotsuki Shunji , Terasaki Koji , Otsuka Shigenori , Chen Ying-Wen , Kanemaru Kaya , Satoh Masaki , Yashiro Hisashi , Tomita Hirofumi , Kondo Keiichi , Okamoto Kozo , Kalnay Eugenia , Kubota Takuji
Published: March 2020

In precipitation science, satellite data have been providing precious, fundamental information, while numerical models have been playing an equally important role. Data assimilation integrates the numerical models and real-world data and brings synergy. We have been working on assimilating the GPM data into the Nonhydrostatic ICosahedral Atmospheric Model (NICAM) using the Local Ensemble Transform Kalman Filter (LETKF). We continue our effort on “Enhancing Precipitation Prediction Algorithm by Data Assimilation of GPM Observations” funded by JAXA, following successful completion of the 3-year project titled “Enhancing Data Assimilation of GPM Observations” from April 2016 to March 2019. The project first started in April 2013 on “Ensemble-based Data Assimilation of TRMM/GPM Precipitation Measurements”, where we developed a global data assimilation system NICAM-LETKF from scratch. This presentation will provide a summary of the past 7-year effort with more emphasis on the recent achievements, including JAXA’s near-real-time analysis called NEXRA (NICAM-LETKF JAXA Research Analysis) and new theoretical developments of Local Particle Filter to treat highly non-Gaussian distributions of precipitation variables in data assimilation.
Development of Drought Risk Assessment Index for Local Comparisons
Authors: Jee Heewon , Kim Hyeonju , Kim Daeho , Kang Tae-Ho , Kim Young-Oh
Published: March 2020

Numerous drought indices assess only hazard; however, very few indices take account into potential vulnerability and risk. Even though drought is one of the natural disasters that affect the socio-economic sphere, these indices do not reflect social capabilities. As an alternative, we proposed Drought Risk Index (DRI) developed by combining frameworks from Intergovernmental Panel on Climate Change(IPCC) and World Risk Index(WRI). DRI consists of three components such as Hazard, Exposure, Capacity. Hazard represents the reason factor causing damage and computed mainly by climate characteristics (e.g. monthly precipitation) while Exposure considers the objects exposed to disaster and calculates by the amount of the water demand (agricultural, industrial, and municipal sectors). In the case of Capacity, it indicates the ability of society to prepare or handle disasters and subdivides into adaptive and coping capacities; the adaptive capacity is calculated by institutional & financial abilities, and coping capacity by water resource facilities and response abilities. The proposed framework for DRI was tested under the specific focus on the local scale comparison of drought risk as a disaster at the Korean Peninsula. We aim at providing the basic tools for national drought management policies and plans.
A new MHD model for Io's and Europa's plasma interaction
Authors: Blöcker Aljona , Roth Lorenz , Ivchenko Nickolay , Chané Emmanuel , Keppens Ronny
Published: March 2020

Io and Europa are embedded in Jupiter’s magnetosphere and the moons’ surfaces and atmospheres interact with the surrounding moving magnetized plasma forming a complex plasma interaction. The interaction scenarios for both moons are characterized by inhomogeneities in the atmospheres from local outgassing. These inhomogeneities affect the electromagnetic environment but can also lead to localized features in the moons' auroral emissions. The moons’ aurora in turn is sensitive to the energy or temperature of the exciting electrons in the plasma. To simulate the interaction scenarios including atmospheric inhomogeneities and aurora generation, we expand the magnetohydrodynamic code MPI-AMRVAC by implementing a self-consistent description of the electron temperature and the electron density where the cooling by inelastic collisions between the magnetospheric electrons and the atmosphere, and the electron heat flux from the magnetospheric plasma to the moons’ ionosphere are included. Furthermore, the numerical schemes of MPI-AMRVAC are able to handle discontinuities that arise from the atmospheric inhomogeneities. Here, we demonstrate the implementation of the physical effects and first modeling results of Io’s and Europa’s plasma interaction with the advanced MHD code.
Efficient POD-Kriging Surrogate Models for Rainfall Forecasting
Authors: Cabrera Gutiérrez Citlali , Jouhaud Jean Christophe
Published: March 2020

Complex models calculations can be very expensive and time consuming. A surrogate model aims at producing results which are very close to the ones obtained using a complex model, but with largely reduced calculation times. Building a surrogate model requires only a few calculations with the real model. Once the surrogate model is built, further calculations can be quickly realized.

In this study, we propose to build surrogate models by combining Proper Orthogonal Decomposition (POD) and kriging (also known as Gaussian Process Regression) for immediate forecasts. More precisely, we create surrogate models for rainfall forecasts on short deadlines. Currently rainfall forecasts in France are calculated for 15 minutes time laps using the AROME-PI model developed by M ́et ́eo-France. In this work, we show that the results obtained with our surrogate models are not only close to the ones obtained by AROME-PI, but they also have a better time resolution (1 minute) and a reduced calculation time.
The seismic broad-band antenna of the Low Noise Underground Laboratory (LSBB, Rustrel, France): a tool for measuring the rotation ground motion.
Authors: Sèbe Olivier , Gaffet Stéphane , Rusch Roxanne , Decitre Jean-Baptiste , Lallemand Charly , Boyer Daniel , Cavaillou Alain , Koenig Jean-Marc , Olivier Serge , Schindele François
Published: March 2020

In the last 20 years, seismologists have recognized that a better sensing of the seismic wavefield is obtained by considering the rotational ground motions in addition to the translation measurements usually provided by seismometers. Even though recent technological developments have resulted in new portable rotation sensors with a sensitivity and a bandwidth suited to seismological applications requirements, the ground rotations have for a long time been estimated indirectly by dense seismic arrays.

The Low Noise Underground Laboratory (LSBB) includes a dense 3D seismic antenna composed of 6 STS2 broad-band seismometers since March 2005. From 2016, this array has been upgraded by the installation of about 10 new seismometers at the surface and inside the galleries of the laboratory. Thanks to these dense and small aperture seismic networks, the vertical and horizontal rotations of the ground motion have been estimated by finite difference approximation of the spatial derivatives of the local ground motions. These measurements provide the opportunity to conduct six degree of freedom (6DOF) analysis (3C translations and 3C rotations) to find out the direction of the wave propagation and to estimate the seismic wave local phase velocity.

The performance of this seismic array in deriving the local spatial gradient of the seismic wavefield, as well as the rotation tensor, will be illustrated by several selected seismic records such as the 2016 central Italy crisis (Amatrice and Norcia events) as well as the recent local Teil earthquake. In addition, the Array Derived Rotations (ADR) from the LSBB antenna are compared with the rotations measured by different kinds of rotation sensors including 2 prototypes of the new BlueSeis3A and a Lily Borehole Tiltmeter.
MAPPY : Multisectoral Analysis of climate and land use change impacts on Pollinators, Plant diversity and crops Yields
Authors: Antoine Maurine ,   Maurine Antoine(1)
Published: March 2020

The impacts of climate change on natural systems and biodiversity are known and already visible in some regions. With regard to agronomic systems, the effects of climate change have also been widely studied. However, some processes are still poorly understood, such as the links between pollinators and climate change or land use change. The feedbacks between different systems under climate change and land use change are still very little explored and require a multidisciplinary approach. It is within this framework that the MAPPY project fits.

The overall objective of the MAPPY project, funded by the AXIS program of JPI-Climate, is to study quantitatively feedback processes linking pollinators, plant diversity and crop yields in the context of climate and land use changes. A set of complementary models will be assembled, iteratively, to capture the dynamics of this complex system at regional level. Dynamic vegetation models and species distribution models will be used to assess the impacts of future climate change. Then, an agent-based model will be used to derive detailed land use and land cover change scenarios for the future at the scale of studied regions. The results of this combination of models will make it possible to assess the potential impacts on pollinator communities, which will make it possible to refine crop models. Finally, the socio-economic impacts of these forecasts will be assessed.

Several case study regions are defined in Europe. The entire study will be undertaken with local stakeholders who will identify the most relevant topics to be addressed. Indeed, stakeholders are asking more and more questions about climate change impact on crop yields, fruit crop damage, pollinator decline. Therefore, they will help us select the results that will be useful to them. Finally, a web platform will be developed with online tools allowing exploration of project results. The platform will be designed by involving stakeholders from the start of the project.
Taking into account granular bed resistance in turbulent bedload transport with arbitrary slope and particle shape
Authors: Maurin Raphaël , Monthiller Remi , Lacaze Laurent
Published: March 2020

Turbulent bedload transport has a major influence for riverbed evolution and is still lacking a general understanding for realistic configurations with arbitrary slopes and sediments shapes. In this contribution, we explore the importance of the granular bed resistance to the fluid flow. Based on the work of Maurin et al (2018), we show that a generalized version of the repose angle of the granular material can be defined, and is able to characterize the slope influence on sediment transport rate for particle scale simulations (Maurin et al, 2015) over a large range of slopes and fluid forcing (i.e. Shields number). Extending the configuration to arbitrary particle shapes, the sediment transport rate is shown to be correlated to the variation of the granular media repose angle (Monthiller 2019), and the relevance of the latter is discussed.

Maurin, R., Chauchat, J., Chareyre B. & Frey, P. (2015). A minimal coupled fluid-discrete element model for bedload transport, Physics of Fluids, 27, 113302
Maurin, R., Chauchat, J., & Frey, P. (2018). Revisiting slope influence in turbulent bedload transport: Consequences for vertical flow structure and transport rate scaling. Journal of Fluid Mechanics, 839, 135-156. doi:10.1017/jfm.2017.903
Monthiller, R. (2019), Particle shape influence on turbulent bedload transport, Master thesis ENSEEIHT/Toulouse Univ.
Fine scale study of major and trace elements in the Fe-Mn nodules from the South China Sea and constraints on their formation processes
Authors: Guan Yao
Published: March 2020

The marine Fe-Mn polymetallic nodules contain relatively high concentrations of Mn, Cu, Ni, Zn, Co and rare earth elements plus yttrium (REY), with a growing economic potential interest in their exploitation. To determinate the metallogenic processes and occurrence phases of the economic metals in the Fe-Mn nodules, we have undertaken high resolution mineralogical and geochemical studies of Fe-Mn nodules collected from the South China Sea (SCS).
The whole-rock mineralogical and chemical compositions of the SCS Fe-Mn nodules indicate hydrogenetic origin. The Mn mineral phases mainly are composed of nanocrystalline vernadite with interlayered 10 Å and 7 Å phyllomanganates, such as todorokite, birnessite, and buserite. Fe(-Ti) oxides/hydroxides are intergrown and essentially X-ray amorphous feroxyhyte and goethite. But we recognize two main types of internal microlayers in the SCS Fe-Mn nodules: Layer type A of suboxic diagenetic precipitates with extremely high Mn/Fe ratio and concentrations of Cu, Ni, Zn, Ba, Li and Mg; Layer type B of oxic hydrogenetic accretions with low fractionation of Mn and Fe and high contents of Co, REY, Ti, Sr and Pb. Furthermore, the elemental mapping indicates that the enrichment of Co and REY mainly associated with Fe mineral phases rather than Mn mineral phases, which are enriched in Mg, Cu, Ni, Zn, Li and Ba. Two mineralization processes and distributions of metals in the individual microlayers respectively are controlled and occurred by the different mineral phases. The increasing occurrence of 10 Å and 7 Å phyllomanganates present in the Layer type A are typically enriched in trace metals such as Ni, Cu, Zn, Li, Ba, and Mg, whereas the metals associated with the Layer type B include Co, Ti, Pb, Sr, REY, which might be carried by the intergrown of Fe(-Ti) oxyhydroxides and vernadite. Thus, hydrogenesis is more beneficial to the enrichment of Fe, Co, Ti, Sr, Pb and REY, while diagenesis is more favorable for the enrichment of Mn, Ni, Zn, Cu, Li, Ba and Mg during the metallogenic processes of the SCS nodules.
Cold ion dynamics and interaction with EMIC waves near the Earth's magnetopause
Authors: Toledo-Redondo Sergio , Lee Justin , Vines Sarah , Turner Drew , Allen Robert , Li Wenya , Boardsen Scott , Andre Mats , Fuselier Stephen , Lavraud Benoit , Gershman Daniel , Viñas Adolfo , Lecontel Olivier , Giles Barbara , Burch James
Published: March 2020

The Earth’s magnetosphere is constantly supplied by plasma coming from the solar wind and from the ionosphere. The ionospheric supply is typically cold and contains heavy ions, which can be often found in most parts of the magnetosphere.

Electromagnetic Ion Cyclotron (EMIC) waves occur in the outer magnetosphere, often in association with ionospheric ions, and serve as a coupling mechanism to the ionosphere and inner magnetosphere. Using the MMS spacecraft, we investigate the dynamics of these waves when ionospheric ions are present, and resolve their motion and energy exchange with the electromagnetic fields below the ion scale. We find that ring current ions and ionospheric ions have different dynamics inside an EMIC wave packet near the magnetopause, affecting the dispersion relation of the wave. We compare the observations to linear dispersion theory, and find excellent agreement between both. Cold ions are accelerated and drain energy from the wave packet, and modify the intrinsic properties such as the wave normal angle and the polarization of the wave.

 

 

 

 
Sea ice in the Weddell Sea: use of moderate resolution imagery to summarize inter-annual variation in conditions and support operational ship survey
Authors: Benham Toby , Christie Frazer , Dowdeswell Julian
Published: March 2020

The distribution and concentration of sea ice presents a significant challenge to shipping and scientific expeditions in high-latitude regions. In addition to achieving safe navigation, information about likely sea ice conditions is needed for expedition planning, and the deployment and retrieval of scientific instruments and their data. In areas where time series of passive microwave data exist, broad-scale analysis of sea ice concentration can be readily achieved. However, the spatial resolution of these data does not permit detailed investigations of sea ice conditions, including near-shore lead development.

Here we present a new methodology for processing moderate resolution multispectral and thermal satellite imagery to summarise inter-annual differences in the probability of sea ice observation. By using multiple daily imagery sources (Terra and Aqua MODIS; Suomi-NPP VIIRS), and averaging resultant concentration maps over longer time periods, we reduce the impediment of cloud cover to characterising sea ice using this type of imagery. Our processing provides a higher-resolution depiction of sea ice conditions and their variability than that afforded by passive microwave data. By estimating a sub-pixel concentration for all pixels identified as ‘Ice’, we capture further nuances of narrower water/thin ice inclusions within the ice cover.

The utility of this new methodology to support operational ship survey in polar regions is demonstrated using examples from the Weddell Sea, Antarctica. Our description of sea ice cover agrees well with that derived from very high-resolution imagery from the Operation Ice Bridge DMS camera system, and with experience of the actual sea ice conditions encountered during the Weddell Sea Expedition in early 2019.
Assessment of the effect of including information on the water level of surface water bodies into large scale hydrological modelling – Case study Amazon basin
Authors: Niemann Christoph , Wissenbach Sabrina , Döll Petra
Published: March 2020

State of the art global hydrological models (GHMs) are able to assess continental water storages and fluxes. Different current GHMs provide conflicting estimates of e.g. evapotranspiration or discharge, resulting in differing water availability or climate change impact estimates. The Global Calibration and Data Assimiliation project (GlobalCDA) aims at enhancing our understanding of global freshwater resources by combining state-of-the-art hydrological modelling with new data assimilition and calibration methods using multiple geodetic and remote sensing data.

This study is part of the hydrological model development efforts within GlobalCDA and analyzes the effect of the adaptation and implementation of an existing dynamic floodplain model (Adam, 2017) into WaterGAP2.2d, a state-of-the-art GHM. The implemented floodplain model approach combines the modeling of a two-way river-floodplain interaction, downstream water transport within river and floodplain and flood-plain-groundwater interactions.

The effect of information on the water level of surface water bodies on the model results is assessed using the Amazon basin as study area. Observed river discharge is used to assess the changes in model efficiency as floodplains and other wetlands have a strong impact on river discharge dynamics. This study shows the value of the modeling of large floodplains and wetlands for an improved estimation of terrestrial water cycle components.
Fluvial incised networks on top of late Ordovician interglacial valley buried hills as the result of post glacial isostatic rebound; 3D seismic input
Authors: Rubino Jean-Loup , Larcher Charlotte , Bourget Julien
Published: March 2020

It is classically assume that prior to deep glacial valleys incision below large scale ice cap, often interpreted as the results of ice flow melting during tidewater period, the initial glacial topography was flat or very low angle and created during a major phase of cold glaciers advance as suggested by quaternary studies. Therefore up to now we have assume that the top of late Ordovician buried hills separating major glacial valleys was the remains of this flat surface truncating the pre-glacial Ordovician Hawaz series, later on flooded by the Lower Silurian. Surprisingly by reinterpreting 3D seismic cubes using spectral decomposition technics on the Murzuk basin in SE Libya, it appears that the top of buried hills are not at all characterized by a flat erosional surface, but it is strongly irregular and shows the development of narrow valley networks displaying the classical dendritic erosional pattern diagnostic of fluvial erosion. These small valleys are organized into a tributary network and don’t flow toward the ice margin, i.e. toward the N-NW but most of the time flow at right angle toward the adjacent main glacial valleys which are pointing toward the NW. These narrow valley networks in this context could be either glacial tunnel valleys located at the periphery of the ice cap in close relationships with glacial fronts (their common settings) or could correspond to fluvial valleys developed later on, in a subaerial setting at some distance from glacial fronts; we retain this second interpretation because in addition to the geomorphic features: (1) they flow parallel to the fronts that we have already recognized, Moreau et al. (2005), Rubino et al.  2007 and (2) they are suspended in the sense that these lateral networks do not reach the bottom of the main glacial valley but, they appear to be connected within the upper part of the glacial infill, immediately below the early Silurian post glacial flooding characterized by the well-known Rhuddanian hot shales. As a result, the incision of the valley network appears quite late in the ice cap melting history. It is why we tend to interpret these valleys erosion as the result of post glacial melting during ice retreat at some distance from the ice front and strongly enhanced by isostatic rebound. Some possible modern analogs of such valley fringing highs may exist in Artic Canadian islands.
Understanding eddy field in the Arctic Ocean from high-resolution satellite observations
Authors: Kozlov Igor , Artamonova Anastasia , Petrenko Larisa , Plotnikov Evgeny , Manucharyan Georgy , Kubryakov Arseny
Published: March 2020

The Arctic Ocean is a host to major ocean circulation systems, many of which generate eddies that can transport water masses and corresponding tracers over long distances from their formation sites. However, comprehensive observations of critical eddy characteristics are currently not available and are limited to spatially and temporally sparse in situ observations.

Here we use multi-mission high‐resolution spaceborne synthetic aperture radar (SAR) measurements to detect eddies over open ocean and marginal ice zones (MIZ) of Fram Strait and Beaufort Gyre regions. We provide the first estimate of eddy properties, including their locations, size, vorticity sign and monthly distribution during summer period (from June to October). The results of historical Envisat ASAR observations for 2007 and 2011 are then compared to Sentinel-1 and ALOS-2 PALSAR-2 measurements acquired in 2016 and 2018, to infer the possible changes in the intensity and locations of eddy generation over the last decade.

The most prominent feature of the obtained results is that cyclonic eddies strongly dominate over anticyclones. Eddies range in size between 0.5 and 100 km and are frequently found over the shelf and near continental slopes but also present in the deep basin. For MIZ eddies, the number of eddies clearly depends on sea ice concentration with more eddies detected at the ice edge and over low ice concentration regions. The obtained results clearly show that eddies are ubiquitous in the Arctic Ocean even in the presence of sea ice and emphasize the need for improved ocean observations and modeling at eddy scales.

A special focus is also given to infer eddy dynamics over the Arctic marginal ice zones. The use of sequential Sentinel-1 SAR images enables to retrieve high-resolution velocity field over MIZ on a daily basis and observe eddy-driven MIZ dynamics down to submesoscales. The obtained eddy orbital velocities are in agreement with historical observations and may reach up to 0.5-0.7 m/s. We believe that this information is critical for better understanding of the key dynamical processes governing the MIZ state, as well as for improving and validation of sea ice and coupled ice-ocean models.

The analysis of eddies in this work was supported by RFBR grant 18‐35‐20078. Processing and analysis of Sentinel‐1 and ALOS‐2 Palsar‐2 data were done within RSF grant 18‐77‐00082. Software development for data analysis in this work was made under the Ministry of Science and Higher Education of the Russian Federation contract 0555‐2019‐0001.
Dispersion in small-scale discrete fracture networks with internal fracture roughness: Challenges for site-scale modelling
Authors: Frampton Andrew , Zou Liangchao
Published: March 2020

There is a need for improved understanding of the mechanisms controlling solute transport in fractured crystalline rocks in order to address long-term safety analysis of repositories for spent nuclear fuel. In this contribution, flow and transport in three-dimensional discrete fracture networks with internal heterogeneity in aperture and permeability is investigated using a numerical DFN model. The fracture networks are obtained using field data of sparsely fractured crystalline rock from the Swedish candidate repository site for spent nuclear fuel. Then, heterogeneity textures with different correlation length and variance are created and mapped to each individual fracture of the network to represent internal fracture roughness. We demonstrate how the structure and variability of textures on the scale of individual fractures leads to different transport and dispersion behaviour at the scale of the network. Key thresholds for cases where flow dispersion is controlled by single-fracture heterogeneity versus network-scale heterogeneity are identified. Furthermore, we highlight enhanced flow channelling for cases where small-scale structure continues across intersections in a network, and highlight challenges for extension to large scale and site-specific modelling.
Impacts of climate change and glacier retreat on water resources and society in the Xinjiang Uyghur Autonomous Region
Authors: Li Hong
Published: March 2020

The Xinjiang Uyghur Autonomous Region is the area on Earth which is most remote from any ocean and the annual precipitation is only 50 mm. Water availability for e.g. agriculture, water supply, and hydropower production is limited in this area. The area has ~20 000 glaciers and they are the main source for water resources. However, since the 1950s, the glaciers are continuously retreating by 20-30%, and result reductions runoff in the lower reaches of some rivers. In this study, we use a widely used hydrological model (HBV) with a glacier retreat module to study the impacts of climate change and glacier retreat on water resources. An ensemble of climate projections up to the end of the century will be explored and the WEAP (Water Evaluation And Planning) model system will be used to analyze impacts on the society.