bluuebunny/crossref_metadata_2025 huggingface dataset:
Hydrogeophysical coupled inversion in coastal aquifers: the Argentona case
Authors: Palacios Andrea , Goyetche Tybaud , Linde Niklas , Carrera Jesús
Published: March 2021

Most, if not all, models of real aquifers go through a calibration process to adjust their hydraulic and solute transport parameters in order to bring the simulations outputs closer to the field observations. In coastal aquifers, the datasets are commonly composed of head time series, solute concentrations from water samples, and water and formation electrical conductivity, these last being of particular importance in coastal settings due to their relevance for seawater detection. Argentona is a well-instrumented field site of a coastal alluvial aquifer located 40 km NE of Barcelona, where a 2-year Cross-Hole Electrical Resistivity Tomography (CHERT) experiment was performed. CHERT provided high resolution electrical resistivity data in depth and allowed the visualization of dynamic aquifer processes. In the present work, we test the calibration of the Argentona SWI model using both the hydrological and the geophysical datasets. To do so, a density-dependent groundwater model was combined with CHERT forward modeling within a parameter calibration framework. In the process we pay attention to the CHERT capacity to recover aquifer salinities, to the coupling of the hydrological and geophysical simulations through petrophysics, to the use of the field specific relations and to the inverse problem parametrization, among other things. Pre-calibration analysis showed the sensitivity of the formation electrical resistivities to the porosities and to the petrophysical parameters, so the inverse problem solves for hydraulic transmissivities, porosities and petrophysical parameters. From the comparison of the preliminary results from the hydrological and the hydrogeophysical calibration, we observe that they point towards a better calibration of model porosities when the electrical resistivity is included in the inverse problem. The results will be compared to other parameter estimation methods, such as laboratory tests, the tidal method and heat tests, also performed at the Argentona site. We will conclude on the added value of the geophysical dataset in the calibration process, the possible improvements and drawbacks of the method.
Relationships between deformation and morphology of forearc wedges and earthquake ruptures
Authors: Cubas Nadaya
Published: March 2021

Over the last decade, we have accumulated evidence that, along subduction zones, a significant part of the seismic cycle deformation is permanently acquired by the medium and reflects the variation of rupture properties along the megathrust. Assuming a persistence of the megathrust segmentation over several hundred thousand years, this permanent deformation and the forearc topography could thus reveal the mechanics of the megathrust. Numerous recent studies have also shown that the megathrust effective friction appears to differ significantly between aseismic or seismic areas. From mechanical modelling, I will first discuss how such differences in effective friction are significant enough to induce wedge segments with varying morphologies and deformation patterns. I will present examples from different subduction zones characterized by either erosive or accretionary wedges, and by different seismic behaviors. Secondly, I will present how this long-lived deformation can in turn control earthquake ruptures. I will show, that along the Chilean subduction zone, all recent mega-earthquakes are surrounded by basal erosion and underplating. Therefore, the deformation and morphology of forearcs would both be partly linked to the megathrust rupture properties and should be used in a more systematic manner to improve earthquake rupture prediction.
Spatiotemporal assessment of heat risk for high-density urban areas: a case study in Dublin, Ireland
Authors: O'Dwyer Barry , Paranunzio Roberta , Dwyer Edward
Published: March 2021

Ireland’s climate is changing and these changes are projected to intensify into the future posing an increasing risk to Ireland’s environment, society and economy. For Ireland and its urban areas in particular, projected changes in the frequency and intensity of heatwaves is considered a moderate but real risk. For example, it is considered likely that Ireland’s capital city Dublin will experience increases in the frequency and intensity of heatwaves under projected climate change. Moreover Ireland’s population is ageing faster than other parts of Europe and becoming increasingly vulnerable to heat stress.

To date, little attention has focussed on heat-related risks for Ireland’s urban areas, focussing primarily on risks associated with sea level rise and changing patterns of precipitation. Through this work, we provide an innovative approach that allows for the integrated assessment of current and future heat risk for the Greater Dublin Area.  Employing a range of modelling approaches, landcover projections have been developed and future changes in urban heat projected, and spatiotemporal variations in level of exposure to heat stress have been calculated using the Universal Thermal Climate Index (UTCI) for current and future periods (2020s – 2050s) under a range of radiative forcing scenarios (RCP4.5 and 8.5).  These assessments are combined with vulnerability information (socio-economic data) to obtain spatially-explicit indexes of heat risk and for different scenarios (RCPs). As a result of projected changes in landcover and temperatures, our assessments show that the level of exposure to extreme heat stress will increase in the coming decades and this is particularly the case for the RCP 8.5 scenario. In combination with assessments of vulnerability, this study identifies significant spatial clusters in the denser urban core of the city and peri-urban areas that are considered to be at relatively high levels of heat risk.

Spatial planning and land use planning are emerging as policy areas that can have significant influence on adaptation to and mitigation of climate change. Through spatial planning, the ways in which cities are designed in order to minimise risks can be re-evaluated and the complexity and uncertainty of climate change tackled.  This study provides spatially explicit information at a fine scale on the evolution of exposure and vulnerability related to thermal heat stress that will support stakeholders to implement strategies and policies aimed at mitigating and adapting to ongoing and future urban heat risk.  

 
On the use of idealised test cases for ocean model development
Authors: Deshayes Julie
Published: March 2021

When comparing realistic simulations produced by two ocean general circulation models, differences may emerge from alternative choices in boundary conditions and forcings, which alters our capacity to identify the actual differences between the two models (in the equations solved, the discretization schemes employed and/or the parameterizations introduced). The use of idealised test cases (idealized configurations with analytical boundary conditions and forcings, resolving a given set of equations) has proven efficient to reveal numerical bugs, determine advantages and pitfalls of certain numerical choices, and highlight remaining challenges. I propose to review historical progress enabled by the use of idealised test cases, and promote their utilization when assessing ocean dynamics as represented by an ocean model. For the latter, I would illustrate my talk using illustrations from my own research activities using NEMO in various contexts. I also see idealised test cases as a promising training tool for inexperienced ocean modellers, and an efficient solution to enlarge collaboration with experts in adjacent disciplines, such as mathematics, fluid dynamics and computer sciences.
Exploring multi-modalities in weather prediction using a univariate graph based on machine learning techniques
Authors: Galmiche Natacha , Blaser Nello , Brun Morten , Hauser Helwig , Spengler Thomas , Spensberger Clemens
Published: March 2021

Probability distributions based on ensemble forecasts are commonly used to assess uncertainty in weather prediction. However, interpreting these distributions is not trivial, especially in the case of multimodality with distinct likely outcomes. The conventional summary employs mean and standard deviation across ensemble members, which works well for unimodal, Gaussian-like distributions. In the case of multimodality this misleads, discarding crucial information. 

We aim at combining previously developed clustering algorithms in machine learning and topological data analysis to extract useful information such as the number of clusters in an ensemble. Given the chaotic behaviour of the atmosphere, machine learning techniques can provide relevant results even if no, or very little, a priori information about the data is available. In addition, topological methods that analyse the shape of the data can make results explainable.

Given an ensemble of univariate time series, a graph is generated whose edges and vertices represent clusters of members, including additional information for each cluster such as the members belonging to them, their uncertainty, and their relevance according to the graph. In the case of multimodality, this approach provides relevant and quantitative information beyond the commonly used mean and standard deviation approach that helps to further characterise the predictability.
Seismic attenuation analysis in the central part of the Leipzig-Regensburg fault zone using the Multiple Lapse Time Window Analysis and Qopen
Authors: van Laaten Marcel , Eulenfeld Tom , Wegler Ulrich
Published: March 2021

Seismic attenuation provides valuable information about the structure of the crust. For the analysis of seismic attenuation in the central part of the Leipzig-Regensburg fault zone in Germany, where numerous areas of intracontinental earthquake swarms are located, we use 18 of the region's strongest earthquakes from the period 2008 to 2019 with a magnitude between 1.4 and 3.0 in the frequency range between 3 and 34 Hz. Two different methods were used to determine the frequency-dependent scattering and the intrinsic attenuation on one hand and to compare the two methods with respect to their results on the other hand. Both methods, the Multiple Lapse Time Windows Analysis (MLTWA) and the Qopen method use the acoustic radiative transfer theory for forward modelling to generate synthetic data and fit them to the observed data. As a by-product of Qopen, we also obtain the energy site amplifications of the stations used in the inversion, as well as the estimated moment magnitudes of the inverted earthquakes. In addition, factors that influence the inversion were investigated. Different combinations of inversion parameters were tested for the MLTWA, as well as the influence of the window length on the result of Qopen. The results from both methods provide similar results within their error bars, with intrinsic attenuation being stronger than scattering and overall, rather low attenuation values compared to other regions.
Acid Mine Drainage (AMD) and Acid Sulphate Soil monitoring using mineral and image spectroscopy: hyperspectral and multispectral approaches
Authors: Kopackova-Strnadova Veronika
Published: March 2021

Mining generates a number of significant environmental impacts, such as increased acidity of the soil/water environment, called mineral Acid Mine Drainage (AMD) being produced when sulphide-bearing material is exposed to oxygen and water.  Similar problem represent acid sulphate soils which are naturally occurring soils containing iron sulphide minerals (predominantly pyrite) or their oxidation products. Once these soils are drained, excavated or exposed to air by a lowering of the water table, the sulphides react with oxygen to form sulfuric acid. For both AMD and acid sulphate soils, there is a lack of historical and update records and, consequently, there is a need for new monitoring techniques allowing systematic analysis. A systematic study on how to map mineral patterns that characterize these acid environments using proximal remote sensing and imaging spectroscopy is presented. Furthermore, the upscaling to the spectral and spatial resolution of the satellite data such as WorldView2/3 and Sentinel-2 is discussed as well as an issue of transferability of the developed methods between the test sites which are characterized by different geographical conditions and environments.
Ion properties of Mercury’s northern cusp under extreme solar wind observed by MESSENGER
Authors: Aizawa Sae , André Nicolas , Raines Jim
Published: March 2021

Mercury’s magnetic cusp allows solar wind plasma to precipitate into the magnetosphere, exosphere, and directly to the surface. This precipitation of solar wind leads to the production of neutrals in the exosphere and/or ions in the magnetosphere and thus it has an important role in shaping Mercury’s space environment. Characterizing the ion properties in the cusp region is important for obtaining a better understanding of the Sun-planet interactions and assessing the solar wind penetration in Mercury’s magnetosphere.

The MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft has observed the northern cusp regularly during its orbital phase. We have analyzed plasma data obtained by the Fast Imaging Plasma Spectrometer (FIPS) onboard MESSENGER under extreme solar wind events and compared the resulting ion properties in the northern cusp with those under non-extreme solar wind events for the first time. We found that (1) flux enhancement is confirmed under the extreme solar wind, and (2) the ion distribution in the cusp has a smaller kappa value than in the magnetosheath, suggesting ion acceleration occurs in the magnetosphere.
Fusing model ensembles and observations together with Bayesian neural networks
Authors: Amos Matt , Sengupta Ushnish , Hosking Scott , Young Paul
Published: March 2021

To fuse together output from ensembles of climate models with observations, we have developed a custom Bayesian neural network that produces more accurate and uncertainty aware projections.

Ensembles of physical models are typically used to increase the accuracy of projections and quantify projective uncertainties. However, few methods for combining ensemble output consider differing model performance or similarity between models. Current weighting strategies that do, typically assume model weights are invariant in time and space though this is rarely the case in models.

Our Bayesian neural network infers spatiotemporally varying model weights, bias and uncertainty to capture that some regions or seasons are better simulated in certain models. The Bayesian neural network learns how to optimally combine multiple models in order to replicate observations and can also be used to infill gaps in historic observations. In regions of sparse observations, it infers from both the surrounding data and similar physical conditions. Although we are using a typically black box technique, the attribution of model weights and bias maintains interpretability.

We demonstrate the utility of the Bayesian neural network by using it to combine multiple chemistry climate models to produce continuous historic predictions of the total ozone column (1980-2010) and projections of total ozone column for the 21st century, both with principled uncertainty estimates. Rigorous validation shows that our Bayesian neural network predictions outperform standard methods of assimilating models.
Observation of ELVES from the International Space Station with the Mini-EUSO telescope
Authors: Casolino Marco , Bertaina Mario , Arnone Enrico , Marcelli Laura , Piotrowski Lech , Battisti Matteo
Published: March 2021

Mini-EUSO is a telescope that observes the Earth from the International Space Station by recording ultraviolet emissions (290 ÷ 430 nm) of cosmic, atmospheric and terrestrial origin with a field of view of 44◦, a spatial resolution of 6.3 km and a temporal resolution of 2.5 mus.

The instrument is based on an optical system composed of two Fresnel lenses and a focal surface composed of 36 multi-anode photomultiplier tubes, 64 channels each, for a total of 2304 channels with single photon counting sensitivity.

Mini-EUSO is a UV telescope launched in 2019   and observing the Earth from the inside the Russian Zvezda module, through a nadir-facing UV-transparent.

It is composed of a Fresnel optics (25 cm diameter, 44 deg field of view) and a Multi Anode Photomultiplier focal surface (2304 pixels, 6km on the surface) with a single-photon counting capability and a sampling rate of 400kHz.

Its scientific objectives include the search for ultra-high energy cosmic rays (E>1e21eV), the study of  meteors and search for interstellar objects and Strange Quark Matter, the  mapping   of the Earth's night-time ultraviolet emissions, the search for space debris.

The characteristcs of the detector make it also well suited for the detection of TLEs, especially ELVES and the study of its development to extract spatial and temporal evolution.  In this article we will focus our attention on the observation of single and multi-ringed elves.
Scale dependent anisotropy of electric field fluctuations in solar wind turbulence
Authors: Deepali Deepali , Banerjee Supratik
Published: March 2021

We study the variation of average powers and spectral indices of electric field fluctuations with respect to the angle between average flow direction and the mean magnetic field in solar wind turbulence. Cluster spacecraft data from the years 2002 and 2007 are used for the present analysis. We perform a scale dependent study with respect to the local mean magnetic field using wavelet analysis technique. Prominent anisotropies are found for both the spectral index and power levels of the electric power spectra. Similar to the magnetic field fluctuations, the parallel (or antiparallel) electric fluctuation spectrum is found to be steeper than the perpendicular spectrum. However the parallel (or antiparallel) electric power is found to be greater than the perpendicular one. Below 0.1 Hz, the slope of the parallel electric power spectra deviates substantially from that of the total magnetic power spectra, supporting the existence of Alfvénic turbulence.
Source to Sea: Transport of organic carbon and iron from forested environments to coastal waters and sediments
Authors: Kellock Celeste , Smeaton Craig , Shah Nadeem , Austin William , Schroeder Christian
Published: March 2021

There is strong evidence that the source of terrestrial carbon and iron geochemistry play an important role in organic carbon transport and preservation in coastal and marine sediments 1,2,3. There is a global drive to increase forestry and Scotland is undergoing a period of afforestation4. A portion of this is being planted in sea loch (fjord) catchments; however the effect of this increase in forestry on coastal carbon transport and storage is poorly understood. Fjord systems have recently been identified as significant terrestrial carbon stores5 therefore understanding how afforestation of these catchments changes the carbon dynamics from source to sea, is key.

In this study Mossbauer spectroscopy, XRD and XRF are used to examine how iron concentration and speciation differs within Scottish fjord sediments. This preliminary data provides insight of the variation in iron speciation in fjord systems, processes controlling iron transport and speciation and potential mineral binding mechanisms in coastal sediments. This enables us to start addressing key knowledge gaps in the transport of organic carbon and iron from land (forested source areas) to sea (fjords). Thus, contributing to our overarching aim of tracing the movement and interactions of organic carbon across the terrestrial - aquatic interface.

Through this project, further analytical techniques such as biomarker analysis, isotopic analysis and SEM, will be used to improve our understanding of source to sea processes in fjord systems throughout the northern hemisphere. This will hopefully enable improved understanding and quantification of local and national carbon stocks. Further insights into carbon and iron burial mechanisms may allow us to tailor land use and management around fjord environments to maximise natural carbon storage.
Modelling coupled fluid flow and solid deformation with the viscoplastic rheology
Authors: Wang Lawrence Hongliang , Yarushina Viktoriya , Podladchikov Yury
Published: March 2021

The coupling between fluid flow and solid deformation plays important roles in earth dynamics at different timescales and length-scales. Related processes include, magma migration and focusing in the Mid-Ocean Ridges, fluid migration after slab dehydration in the subduction zone, channelized fluid flow observed as seismic chimney in the continental margin, as so on. Here we study how localized fluid channels can develop through asymmetric compaction and decompaction processes of the solid matrix by solving coupled two-phase equations with viscoplastic rheology. Previous studies produced fluid channels with decompaction weakening, while negative effective pressure (Pt-Pf) is inevitable due to the simplified rheology formulation. We develop a viscoplastic rheology formulation that considers the effects of shear stress and plastic failure on the volumetric deformation, consistent with experimental data.

Our model results show that this new rheology can produce channelized fluid flow without negative effective pressure in the model. Our numerical results also clarified that it is the flow instability of the coupled two-phase system that cause the formation of fluid channels. The ratio between shear viscosity and bulk viscosity determines how fast the flow instability develops and manifests. The geometry of the Reservoir, on the other hand, can affect where the channels form. We further study the effects of different background and reservoir porosity, different rock layer, permeability exponents, decompaction weakening factor, and so on. These results provide a better understanding of the two-phase system and its potential applications in geological environments.   

 
Repeat Subglacial Lake Drainage and Filling Beneath Thwaites Glacier
Authors: Malczyk George , Gourmelen Noel , Goldberg Daniel , Wuite Jan , Nagler Thomas
Published: March 2021

Active subglacial lakes have been identified throughout Antarctica, offering a window into subglacial environments and their impact on ice sheet mass balance. We use high-resolution altimetry measurements over the Thwaites Glacier to show that a lake system underwent a second episode of drainage activity in 2017, only four years after another substantial drainage event. Our observations suggest significant modifications of the drainage system between the two events, with 2017 experiencing greater upstream discharge, faster lake-to-lake connectivity, and the transfer of water within a closed system. Measured rates of lake recharge during the inter-drainage period are significantly larger than modelled estimates, suggesting processes which drive subglacial melt production are currently underestimated. Our study highlights new methods of exploring subglacial environments through the application of altimetry, with potential applications for studying subglacial lakes across Antarctica
Re-visiting a long-term Free Air CO2 Enrichment (FACE) experiment in a Danish heathland/grassland ecosystem (CLIMAITE) reveals highly dynamic soil carbon 
Authors: Li Qiaoyan , Larsen Klaus Steenberg , Gundersen Per
Published: March 2021

The feedback of the terrestrial carbon cycle to global climate change is among the largest uncertainties in climate change research. To test the potential ecosystem effects of future climate scenarios, a field-scale FACE (Free Air CO2 Enrichment) experiment combined with increased temperatures and extended summer drought was performed in the period 2005–2013 on a temperate heathland/grassland ecosystem in Denmark (the CLIMAITE project). A major finding from the original experiment was that the soil carbon pool increased by approximately 20% under elevated CO2 over the 8 years of the study*.

The FACE treatment was in effect also an in situ labeling experiment because the added CO2 was depleted for 13C （13CO2FACE=-29‰）compared to ambient atmospheric CO2（13CO2AIR=-8‰）. Therefore, the isotopic signal of the remaining soil carbon can be used to investigate the turnover of soil carbon during the time since the end of the original study.

During the growing season in 2020, seven years after the CO2 fumigation experiment was terminated, soil samples were extracted in all plots using the same sampling strategy as in previous samplings. Interestingly, the direct soil C pool measurements showed that the extra soil carbon, which was stored during the eight years with elevated CO2 had been lost again over the course of the following seven years. The isotopic composition of the different soil layers had also changed back towards the values measured in control plots, although still being slightly more depleted for 13C. Still, the convergence of the isotopic composition in the different treatments confirms the trend observed from the direct C pool measurements and also hints that a part of the more recalcitrant carbon taken up during the elevated CO2 experiment is still there while most of the labile/less recalcitrant carbon has been decomposed and reemitted to the atmosphere. The results show that the soil carbon pool in the ecosystem is extremely dynamic and may change fast in response to changes in major ecosystem drivers, and in particular is highly sensitive to the atmospheric CO2 concentration.

*Dietzen CA, Larsen KS, Ambus P, Michelsen A, Arndal MF, Beier C, Reinsch S, Schmidt IK (2019) Accumulation of soil carbon under elevated CO2 unaffected by warming and drought. Global Change Biology, 25: 2970–2977. doi: 10.1111/gcb.14699.
HelioSwarm: The Nature of Turbulence in Space Plasmas
Authors: Spence Harlan , Klein Kristopher , Science Team HelioSwarm
Published: March 2021

Recently selected for phase A study for NASA’s Heliophysics MidEx Announcement of Opportunity, the HelioSwarm Observatory proposes to transform our understanding of the physics of turbulence in space and astrophysical plasmas by deploying nine spacecraft to measure the local plasma and magnetic field conditions at many points, with separations between the spacecraft spanning MHD and ion scales.  HelioSwarm resolves the transfer and dissipation of turbulent energy in weakly-collisional magnetized plasmas with a novel configuration of spacecraft in the solar wind. These simultaneous multi-point, multi-scale measurements of space plasmas allow us to reach closure on two science goals comprised of six science objectives: (1) reveal how turbulent energy is transferred in the most probable, undisturbed solar wind plasma and distributed as a function of scale and time; (2) reveal how this turbulent cascade of energy varies with the background magnetic field and plasma parameters in more extreme solar wind environments; (3) quantify the transfer of turbulent energy between fields, flows, and ion heat; (4) identify thermodynamic impacts of intermittent structures on ion distributions; (5) determine how solar wind turbulence affects and is affected by large-scale solar wind structures; and (6) determine how strongly driven turbulence differs from that in the undisturbed solar wind. 
Protecting Quaternary palaeoenvironmental sites in south-east Arabia: a database approach
Authors: Sayama Kenta , Parton Ash , Viles Heather
Published: March 2021

Quaternary palaeoenvironmental archives are essential for our understanding of past climate changes and humanity’s response to them. In the age of anthropogenic climate change, these sites are not only important scientifically, but also educationally to teach people about the impact of climate change, and the role it played in shaping past communities. 

The landscape of the Arabian Peninsula is highly reactive to even subtle changes in climate and recent research has shown that palaeoenvironmental archives in south-east Arabia (i.e., dunes, fluvial/alluvial and palaeolake deposits, etc.) are crucial for our understanding of the role of climate change in the late-Pleistocene dispersal of early human populations out of Africa. The importance of archaeological sites in this region is increasingly recognised, with many sites benefitting from extensive research and conservation. Similarly, the rich geological history of the region has either been catalogued or protected with integration into national tourism strategies. Despite the the budding initiative of geoheritage conservation in Arabia, however, the protection of Quaternary palaeoenvironmental sites has been entirely disregarded.

With the lack of a protection framework and the continuous economic development of the region, many of these archives are under imminent threat or already destroyed. At present, no assessment has been conducted to examine the possible extent of such loss. Here we propose that a system must be established for scientists to record and highlight the potential threat of destruction of these irreplaceable archives.  Also, to protect these sites effectively, we must develop a conservation strategy with an understanding of the factors that differentiate them from geoheritage sites that already enjoy protection.

For the first time, this study has compiled a database of Quaternary palaeoenvironmental archives in south-east Arabia. A total of ~300 sites in the entire region have been assessed for their risk status, with ~100 sites in the UAE assessed additionally for their scientific and educational values. Preliminary results indicate that more than 10% of sites, mostly in urban or coastal settings, have been destroyed or are under imminent threat.  Furthermore, the prevailing prioritisation of conventional aesthetic values in geoheritage conservation has been identified as a major obstacle in promoting the conservation of these sites. 
Seasonal predictions as a high-resolution large ensemble to study extreme events over recent decades
Authors: Kelder Timo , Slater Louise , Marjoribanks Tim , Wilby Rob , Prudhomme Christel , Wagemann Julia
Published: March 2021

Large ensembles of climate model simulations may be used to assess the likelihood of extreme events, which only have a limited chance of occurring in observed records. In this talk, we discuss how the ECMWF seasonal prediction system SEAS5 can be used to generate a 100-member ensemble over 1981-present. SEAS5 is a global coupled ocean, sea-ice, atmosphere model with a horizontal resolution of 36 km. We introduce an open and reproducible workflow to retrieve Copernicus SEAS5 data and evaluate the ensemble member independence, model stability, and model fidelity. We illustrate how the increased sample size may help risk estimation, detecting trends in 100-year extremes as well as analysing drivers of extreme events that are difficult to discern from limited observational records.
CASRock—a code to simulate THMC processes in fractured geological media
Authors: Pan Pengzhi
Published: March 2021

This work presents the advancement of a self-developed Cellular Automata Software for engineering Rockmass fracturing processes (CASRock, http://en.casrock.cn/) in the applications of thermo-hydro-mechanical-chemical (THMC) processes in fractured geological media. It contains a series of previous developed numerical systems, namely EPCA for simulation of heterogeneous rock failure process, VEPCA for visco elastoplastic analysis, D-EPCA for rock dynamic response simulation, THMC-EPCA for coupled THMC processes in geological media and RDCA for simulation of rock cracking process from continuity to discontinuity. In CASRock, the non-isothermal, unsaturated fluid flow, mechanical process and chemical reaction are sequentially coupled by updating all the state variables using cellular automaton technique and finite difference method on spatial and temporal scale, respectively. The Lagrangian method is used to simulate the particle transport. The control equations, coupling scheme and numerical implementation are briefly introduced. Several applications, including  in the background of high level nuclear waste disposal are provided to show the abilities of CASRock in the simulation of coupling processes between physical fields. These applications include, (1) stability analysis of engineering rockmass under mechanical loading, (2) numerical study on coupled TM processes in hard rock pillar, (3) study on coupled THM processes in engineering barrier, (4) simulation of the THMC process in fractured rock.
SeisBench: A toolbox for benchmarking and applying machine learning in seismology.
Authors: Woollam Jack , Münchmeyer Jannes , Giunchi Carlo , Jozinovic Dario , Diehl Tobias , Saul Joachim , Michelini Alberto , Haslinger Florian , Lange Dietrich , Tilmann Frederik , Rietbrock Andreas
Published: March 2021

Machine learning methods have seen widespread adoption within the seismological community in recent years due to their ability to effectively process large amounts of data, while equalling or surpassing the performance of human analysts or classic algorithms. In the wider machine learning world, for example in imaging applications, the open availability of extensive high-quality datasets for training, validation, and the benchmarking of competing algorithms is seen as a vital ingredient to the rapid progress observed throughout the last decade. Within seismology, vast catalogues of labelled data are readily available, but collecting the waveform data for millions of records and assessing the quality of training examples is a time-consuming, tedious process. The natural variability in source processes and seismic wave propagation also presents a critical problem during training. The performance of models trained on different regions, distance and magnitude ranges are not easily comparable. The inability to easily compare and contrast state-of-the-art machine learning-based detection techniques on varying seismic data sets is currently a barrier to further progress within this emerging field. We present SeisBench, an extensible open-source framework for training, benchmarking, and applying machine learning algorithms. SeisBench provides access to various benchmark data sets and models from literature, along with pre-trained model weights, through a unified API. Built to be extensible, and modular, SeisBench allows for the simple addition of new models and data sets, which can be easily interchanged with existing pre-trained models and benchmark data. Standardising the access of varying quality data, and metadata simplifies comparison workflows, enabling the development of more robust machine learning algorithms. We initially focus on phase detection, identification and picking, but the framework is designed to be extended for other purposes, for example direct estimation of event parameters. Users will be able to contribute their own benchmarks and (trained) models. In the future, it will thus be much easier to compare both the performance of new algorithms against published machine learning models/architectures and to check the performance of established algorithms against new data sets. We hope that the ease of validation and inter-model comparison enabled by SeisBench will serve as a catalyst for the development of the next generation of machine learning techniques within the seismological community. The SeisBench source code will be published with an open license and explicitly encourages community involvement.
Clinoform growth and sediment flux of Late Cenozoic Yinggehai and Qiongdongnan shelf margins, Northern South China Sea
Authors: Chen Si , Wang Hua , Ma Jianghao , Gong Tianhao , Yu Zhenghong
Published: March 2021

This study discusses the sedimentary flux, and sedimentary system source tracking on the shelf margins of Yinggehai (YGH) and Qiongdongnan (QDN) Basins, Northern South China Sea. The shelf margin clinoforms of YGH and QDN Basins, have grown since the Late Cenozoic (10.5 Ma), which generated more than 4 km-thick shelf prism above the T40 surface. By using the core, well drilling data, 2D and 3D seismic surveys, this study aims to: ① demonstrate the geometry morphology and architecture of the clinoforms, while the shelf margin trajectory (including the shelf-edge trajectory and toe of slope trajectory) showing down-flatting and rising patterns where the progradation and aggradation happened through the vertical evolution; ② estimate sediment supply values, load volumes, and their changes since the Late Cenozoic, predict ratio of the sediment flux across shelf-edge during their dynamic processes; ③ investigate the contradiction and correlation among the phenomena that sediments show distinctly increasing in flux, decreasing in grain size, and response delay of flux rate peak since 2-4 Ma. The preliminary results show that the vertical sediment accumulation rate increased significantly across the entire YGH and QDN Basin margin system after 2.4 Ma, with a marked increase in mud content that likely caused by long‐distance, alongshore currents with high content of mud during the Pleistocene. Furthermore, laterally, the estimated total sediment flux onto the margin shows a dramatic decline from west to east while moving away from the Red River depocenter, as well as a decrease in the percentage of total discharge crossing the shelf break in this same direction. The overall margin geometry shows a remarkable change from sigmoidal, strongly progradational and aggradational in the west to weakly progradational in the east of QDN Basin margin. The Late Cenozoic shelf margin growth, with its overall increased sediment flux, responded to global, high‐frequency transgressive‐regressive climate cycles during a falling global sea level and gradual cooling temperature in this icehouse period.
Importance of variable neutral drag coefficients for ocean-ice and air-ice fluxes in polar regions
Authors: Sterlin Jean , Fichefet Thierry , Massonnet Francois , Tsamados Michel
Published: March 2021

Sea ice features a variety of obstacles to the flow of air and seawater at its top and bottom surfaces. Sea ice ridges, floe edges, ice surface roughness and melt ponds, lead to a form drag that interacts dynamically with the air-ice and ocean-ice fluxes of heat and momentum. In most climate models, surface fluxes of heat and momentum are calculated by bulk formulas using constant drag coefficients over sea ice, to reflect the mean surface roughness of the interfaces with the atmosphere and ocean. However, such constant drag coefficients do not account for the subgrid-scale variability of the sea ice surface roughness. To study the effect of form drag over sea ice on air-ice-ocean fluxes, we have implemented a formulation that estimates drag coefficients in ice-covered areas comprising the effect of sea ice ridges, floe edges and melt ponds, and ice surface skin (Tsamados et al., 2013) into the NEMO3.6-LIM3 global coupled ice-ocean model. In this work, we thoroughly analyse the impacts of this improvement on the model performance in both the Arctic and Antarctic. A particular attention is paid to the influence of this modification on the air-ice-ocean fluxes of heat and momentum, and the characteristics of the oceanic surface layers. We also formulate an assessment of the importance of variable drag coefficients over sea ice for the climate modelling community.
What can idealized storm surge simulations tell us about worst case scenarios?
Authors: Andrée Elin , Su Jian , Drews Martin , Dahl Larsen Morten Andreas , Bendix Hansen Asger , Skovgaard Madsen Kristine
Published: March 2021

The potential impacts of extreme sea level events are becoming more apparent to the public and policy makers alike. As the magnitude of these events are expected to increase due to climate change, and increased coastal urbanization results in ever increasing stakes in the coastal zones, the need for risk assessments is growing too.

The physical conditions that generate extreme sea levels are highly dependent on site specific conditions, such as bathymetry, tidal regime, wind fetch and the shape of the coastline. For a low-lying country like Denmark, which consists of a peninsula and islands that partition off the semi-enclosed Baltic Sea from the North Sea, a better understanding of how the local sea level responds to wind forcing is urgently called for.

We here present a map for Denmark that shows the most efficient wind directions for generating extreme sea levels, for a total of 70 locations distributed all over the country’s coastlines. The maps are produced by conducting simulations with a high resolution, 3D-ocean model, which is used for operational storm surge modelling at the Danish Meteorological Institute. We force the model with idealized wind fields that maintain a fixed wind speed and wind direction over the entire model domain. Simulations are conducted for one wind speed and one wind direction at a time, generating ensembles of a set of wind directions for a fixed wind speed, as well as a set of wind speeds for a fixed wind direction, respectively.

For each wind direction, we find that the maximum water level at a given location increases linearly with the wind speed, and the slope values show clear spatial patterns, for example distinguishing the Danish southern North Sea coast from the central or northern North Sea Coast. The slope values are highest along the southwestern North Sea coast, where the passage of North Atlantic low pressure systems over the shallow North Sea, as well as the large tidal range, result in a much larger range of variability than in the more sheltered Inner Danish Waters. However, in our simulations the large fetch of the Baltic Sea, in combination with the funneling effect of the Danish Straits, result in almost as high water levels as along the North Sea coast.

Although the wind forcing is completely synthetic with no spatial and temporal structure of a real storm, this idealized approach allows us to systematically investigate the sea level response at the boundaries of what is physically plausible. We evaluate the results from these simulations by comparison to peak water levels from a 58 year long, high resolution ocean hindcast, with promising agreement.
Inferring suspended sediment carbon content and particle size at high frequency from the optical response of a submerged spectrometer 
Authors: Sehgal Dhruv , Martínez-Carreras Núria , Hissler Christophe , Bense Victor , Hoitink AJF (Ton)
Published: March 2021

Manual and unattended sampling in the field and laboratory analysis are common practices to measure suspended sediment (SS) carbon content and particle size. However, one of the major drawbacks of these ex-situ methods is that they make high frequency measurements challenging. This includes restricted data collection due to limited access to the sampling locations during turbulent conditions or high flows, when the largest amount of sediments is transported downstream, introducing uncertainty in quantification of SS properties (particle size and carbon content) and sediment loads. Knowledge on SS carbon content and particle size is also important to better understand the multi-component form of suspended sediments (i.e. flocs) that directly affect sediment transport and other sediment properties (e.g. settling velocity and density). Moreover, SS carbon content and particle size exert an impact on the optical sensor readings that are traditionally used to measure turbidity. In that respect, high frequency measurements of SS carbon content and particle size could eventually help us to move from ‘local’ calibrations towards ‘global’ dependencies based on in-situ SS characterization.

In this study, we propose to use a submerged UV-VIS spectrometer to infer SS carbon content and particle size. The sensor measures the entire light absorption spectrum of water between 200 nm and 750 nm at sampling intervals as short as 2-minutes. To this end, we first test our approach under controlled conditions with an experimental laboratory setup consisting of a cylindrical tank (40-L) with an open top. An UV-VIS spectrometer and a LISST-200X sensor (to measure particle size distribution) are installed horizontally. A stirrer facilitates the homogeneous mixing of SS and prevents the settling of heavy particles at the bottom. We use the sediments sampled from 6 sites in Luxembourg with contrasting composition and representing different land use types and geological settings. The sampled sediments were wet sieved into 3 size classes to clearly recognize the effect of particle size on absorption. In our investigation, we use specific wavelengths, chemometric techniques and carbon content specific absorbance indices to infer SS composition and particle size from the absorption spectrum. Results are then validated using in-situ field data from two instrumented field sites in Luxembourg. Amid the challenge of associating laboratory and field results, the preliminary results indicate that the absorption spectrum measured with a submerged UV-VIS spectrometer can be used to estimate SS particle size and carbon content.
Analysis of novel shallow geothermal system in coastal fractured limestone aquifer
Authors: Pastore Nicola , Cherubini Claudia , Giasi Concetta Immacolata
Published: March 2021

In shallow geothermal systems natural and forced groundwater movement as well as the temperature driven flow plays an important role on the borehole heat exchanger efficiency.

The analysis of the efficiency of innovative heat exchangers installed in a fractured limestone aquifer was carried out through three-dimensional numerical simulations and experimental investigations on physical models.

The coastal fractured limestone aquifer of the industrial area of Bari (Italy) was chosen as benchmark field site in order to identify the aquifer parameter range and the respective combinations. The role of seawater intrusion on the borehole heat exchanger efficiency was deepen .

The results disclosed that the efficiency of the innovative heat exchangers is strictly dependent on the aquifer transmissivity and groundwater flow under natural and forced groundwater conditions.

Discussion on the performance of the seasonal heat storage and the occurrence of the thermal interference between the borehole heat exchanger was presented.