bluuebunny/crossref_metadata_2025 huggingface dataset:
Seismic anisotropy in metamorphic rocks from the COSC-1 borehole, Sweden: A cross-scale investigation from thin section analysis to seismic scales
Authors: Kästner Felix , Pierdominici Simona , Zappone Alba , Morales Luiz F. G. , Schleicher Anja M. , Wilke Franziska D. H. , Berndt Christian
Published: March 2021

Metamorphic and deformed rocks in thrust zones show particularly high seismic anisotropy causing challenges for seismic imaging and interpretation. A good example is the Seve Nappe Complex in Jämtland, Sweden, an exhumed orogenic thrust zone characterized by a strong but incoherent seismic reflectivity and considerable seismic anisotropy. However, only little is known about the origin of the anisotropy in relation to composition, structural influences, and implications for measurements at different seismic scales. We present an integrative study of the seismic anisotropy at different scales combining mineralogical composition, microstructural analyses and seismic laboratory experiments from samples of the 2.5 km-deep COSC-1 borehole. While there is a pronounced crystallographic preferred orientation in most of the core samples, variations in anisotropy correlate strongly with bulk mineral composition and dominant core lithology. Based on three major lithologic different facies (felsic gneiss, amphibole-rich rocks, and mica schists), we propose an anisotropy model for the full length of the borehole, which indicates two prevailing anisotropic units. Comparison of laboratory seismic measurements and electron-backscatter diffraction (EBSD) data reveals a strong scale-dependence, which is more pronounced in the highly deformed, heterogeneous samples. This highlights the need for comprehensive cross-validation of microscale anisotropy analyses with additional lithological data when integrating seismic anisotropy through seismic scales.
Ohmic and viscous damping of the Earth's Free Core Nutation
Authors: Triana Santiago , Rekier Jeremy , Trinh Antony , Dehant Veronique , Zhu Ping
Published: March 2021

The cause for the damping of the Earth's Free Core Nutation (FCN) and the Free Inner Core Nutation (FICN) eigenmodes has been a matter of debate since the earliest reliable estimations from nutation observations were made available. Numerical studies are difficult given the extreme values of some of the parameters associated with the Earth's fluid outer core, where important dissipation processes can take place. We present a linear numerical model for the FCN that includes viscous dissipation and Ohmic heating. We find an asymptotic regime, appropriate for Earth's parameters, where viscous and Ohmic processes contribute equally to the total damping, with the dissipation taking place almost exclusively in the boundary layers. By matching the observed nutational damping we infer an enhanced effective viscosity matching and validating methods from previous studies. We suggest that turbulence caused by the Earth's precession can be a source for the FCN's damping. 
Modelling the Impact of Future Climate on Mountainous Watershed Nitrogen Cycling 
Authors: Weierbach Helen , Maavara Taylor , Woodburn Erica , Bouskill Nicholas
Published: March 2021

Terrestrial nitrogen cycling plays an important role in regulating the export of nitrogen to surface waters. Terrestrial nitrogen transformations, however, are sensitive to changes in climate and disturbances, including altered temperature and precipitation patterns, snowpack depth, or wildfires. Thus, understanding how changing climate impacts terrestrial nitrogen cycling and the corresponding export of N to surface waters is an important part of understanding the impact of climate change on Earth’s freshwater resources. In this study, we investigate the short-term impacts of changing temperature, water partitioning and wildfire in the mountainous East River Watershed (ERW) located in the Upper Colorado River Basin. We use the High Altitude Nitrogen Suite of Models (HAN-SoMo), a course resolution semi-distributed ensemble of process based models developed for the ERW, to model changes in N through the vadose zone, surface waters and groundwater. HAN-SoMo was developed and calibrated against over 1600 N concentration measurements in the ERW to explore equifinality in parameter combinations. Three calibration scenarios were developed which explore the importance of different N sources and sinks throughout the watershed. Results of the most probable calibration suggest that the N cycling in the ERW is dominated by instream transformations and recycling of cow and plant matter. Additionally, results suggest that geogenic N from weathering of Mancos shale accounts for about 12% of N sources in the watershed. Here we will use the most probable HAN-SoMo calibration to explore possible changes in nitrogen cycling (key sources and sinks, N fluxes, etc.) under perturbations in temperature, water sources and wildfire.

 
Dry days, associated temperature anomalies and inter-annual variations in spring phenology
Authors: Calanca Pierluigi
Published: March 2021

The imprint of recent climate change on plant phenology has been the subject of several investigations during the last few decades. Results of such studies have repeatedly documented the advances of key phenological stages in spring. More recently, they have also shown that global warming has induced changes in temperature sensitivity and led to more uniform phenology across elevations. While awareness of trends in phenology undoubtedly contributes to inform ecosystem management, the provision of ecosystem services also necessitates knowledge and understanding of how spring phenology varies from year to year. For instance, in view of growing exposure of grassland ecosystems to summer drought, in Alpine countries forage production increasingly relies on exploiting at best spring growth, which in turn requires an accurate timing of field operations, depending on the progress of herbage development.

Employing long-term phenological observations on forest trees and grassland plants and weather records from Switzerland, in this contribution I examine year-to-year variations in spring phenology in light of anomalies in the seasonal mean temperature for the months of February to April, and reflect on how the latter can be related to number of dry days and associated temperature anomalies. Based on these findings and results from other studies, I discuss possible implications of future climate change for the variability of spring phenology.
Temporal variability of methane emissions from a closed landfill at Denmark
Authors: Kissas Konstantinos , Ibrom Andreas , Kjeldsen Peter , Scheutz Charlotte
Published: March 2021

Methane (CH4) emissions from landfills contribute to global warming, impacting significantly the environment and human health. Landfill CH4 emissions strongly depend on changes in barometric pressure, inducing short-term CH4 emission variation of several orders of magnitude. Estimating the temporal variability of CH4 emitted into the atmosphere could help us reducing the uncertainties of annual emission estimates from landfills. In this study, we focus on the temporal variability of CH4 emissions under the impact of barometric pressure changes.

CH4 emissions of a closed landfill (Skellingsted, Western Zealand, Denmark) were measured with two different methods from December 2019 to June 2020; continuously with the eddy covariance method (EC) and discretely with the dynamic tracer dispersion method (TDM). The EC method allows continuous measurements from a confined surface area, with most likely limited representativeness of the whole landfill site due to the considerable horizontal heterogeneity. The TDM method is able to quantify the emission from the whole site insensitive of the topography with the limited representativeness for the temporal variability.

CH4 emissions to the atmosphere measured by the TDM and fluxes measured by the EC ranged from to 0 to almost 100 kg h-1 and from 0 to 10 μmol m-2 s-1, respectively. The CH4 fluxes measured continuously using the EC method were highly correlated with the emissions from the periodic measurements using the TDM and fluctuated according to the pressure tendency. Under decreasing barometric pressure the highest CH4 emissions where observed, while increasing barometric pressure suppressed them almost to 0.

Our results demonstrate the value of implementing two different complementary measurement techniques in parallel that will help to quantify total annual CH4 emission from a landfill. EC method provides continuous measurements describing accurately the temporal variation of emissions, while TDM method is able to quantify emissions from the whole site.
3D Seismic Wave Simulations of Mantle Heterogeneity and Shear Wave Splitting Phases 
Authors: Creasy Neala , Bozdag Ebru
Published: March 2021

Constraining the pattern and properties of seismic anisotropy in the Earth can help reveal relationships between mineral physics, mantle convection, and seismology. Sources of anisotropy in the lithosphere as frozen-in anisotropy, transition zone, and D" complicate shear wave splitting measurements, resulting in shear wave splitting that can differ from plate motion. If we better understand seismic anisotropy sourced in the lithosphere, we could also better constrain D" anisotropy, which requires correcting for the upper mantle to some extent. The goal of this work is to investigate the effect of 3D mantle and crustal structure on waveforms based on 3D wave simulations and adjoint data sensitivity kernels. We will explore the common phases (SKS, SKKS, S, ScS, PKS, etc.) and the common distance ranges used for mantle shear wave splitting with a resolution down to 9 s by conducting numerical simulations via 3D global wave propagation solver SPECFEM3D_GLOBE. We show results for a 1D mantle model (i.e., PREM [Dziewonski and Anderson, 1981]) and at least three 3D mantle models (S20RTS [Ritsema et al., 2011], GLAD-M15 [Bozdag et al., 2015], GLAD-M25 [Lei et al., 2020]). We calculate a number of data sensitivity kernels for travel time, amplitude, and anisotropy for our phases of interest over a variety of event depths and distance ranges. This work will help improve the measurements of shear wave splitting. The long-running goal is to use shear wave splitting in global full waveform inversion by addressing appropriate parameterization to describe body-wave anisotropy in the mantle during the inversion process. All simulations were conducted on a Research Allocation on the high-performance computing environment of XSEDE resources (TACC Stampede2).
The CHE global nature run: A high-resolution simulation providing realistic global carbon weather for the year of the Paris Agreement
Authors: Agusti-Panareda Anna , McNorton Joe ,   CHE nature run team
Published: March 2021

High resolution simulations of carbon dioxide, methane and carbon monoxide (CO2, CH4 and CO) have been produced as part of the CO2 Human Emissions (CHE) project in order to assist carbon-cycle research and applications, such as the design of a CO2 Monitoring Verification Support (CO2MVS) capacity in support of the Paris Agreement. This dataset provides realistic variability of the carbon tracers in the atmosphere modulated by the weather and the underlying surface fluxes as shown by comparison with independent observations. It can therefore provide a reference for atmospheric inversion systems that use atmospheric observations from satellites and in situ networks to derive natural surface fluxes and anthropogenic emissions of CO2, CH4 and CO. Additional tagged tracers are used to identify the atmospheric enhancements associated with the different surface fluxes. These flux enhancements can shed light into the potential of new satellites to detect the emission signals in the atmosphere. As satellites observe the mean concentration of carbon tracers over a partial/total atmospheric column, the CHE nature run is also used here to assess the contribution of total column variability from different layers in the atmosphere. We find that the variability in the free troposphere is often dominating the variability of the total column for CO2, CH4 and CO, highlighting the role of long-range transport to represent variability of carbon tracers in the atmosphere, as well as the importance of assessing the accuracy of long-range transport in chemical transport models used in atmospheric inversions.
New insights into the age and metamorphic evolution of the Irumide orogeny in Malawi
Authors: Böhme Sofia C. , Boger Steven D.
Published: March 2021

Metapelitic rocks of the Irumide Domain in central Malawi contain detrital and metamorphic zircons. U-Pb zircon geochronology yielded two age populations, which have been dated at c. 1995 Ma and 1050 Ma. The ages demonstrate that the precursor sediments to these rocks were derived from erosion of the Palaeoproterozoic Ubendian Domain, which is adjacent to the north, and at a later stage were affected by the Irumide orogeny. The metapelitic rocks are characterised by garnet + sillimanite + biotite ± muscovite ± K-feldspar mineral assemblages. Phase equilibria modelling shows that they equilibrated under pressure-temperature conditions of about 7 kbar and 700–740˚C.  In combination with the metamorphic ages this is interpreted to record late Mesoproterozoic (c. 1050 Ma) accretion of a juvenile island arc, the South Irumide Domain, to the southern margin of the Tanzania-Congo Craton.
CO2 spatial distribution over Mexican urban centers from satellite observations
Authors: Campos-Pineda Mixtli , Taquet Noémie , Stremme Wolfgang , Bezanilla Alejandro , Lauvaux Thomas , Ramonet Michel , Grutter Michel
Published: March 2021

The Mexico City Metropolitan Area (MCMA), located in proximity to an active volcano, is the largest urban center in North America and there is great interest to better characterize carbon emissions of this and other major urban centers in the country. NASA’s Orbiting Carbon Observatory (OCO-3) was installed in the International Space (ISS) in 2019. The inclusion of a Pointing Mirror Assembly (PMA) in this third iteration allows for a new mode of data collection that samples an area of ~80 x 80 km in approximately 2 minutes. This mode is used to collect map-like data, called Snapshot Area Maps (SAMs), over areas of interest (e.g. volcanos or urban areas). The OCO-3 module has collected SAMs over the MCMA (and the Popocatépetl volcano) throughout 2020, and also of the metropolitan areas of Guadalajara and Monterrey throughout the second half of 2020.

Using data from the public release of OCO-3 Level 2 (L2) “Lite EarlyR” product, available at the Goddard Earth Sciences Data and Information Services Center (GES DISC), we have built maps of the spatial distribution of xCO2 for these regions. Data is filtered according to the reported quality flag in the data product, compared with ground-based FTIR measurements of column xCO2 over the MCMA region and averaged with an oversampling method. Surface pressure data with the averaged xCO2 is used to calculate the concentrations within the mixed layer (xCO2ML) in order to compensate for the effects of the complex terrain.  This product is also used  for comparison with CO spatial distributions obtained from TROPOMI data products and a simple xCOML/xCO2ML ratio is obtained and mapped for the three urban centers. This work showcases the utility of SAMs in cooperation with ground-based measurements to produce detailed descriptions of the spatial distribution of CO2 for a wide variety of applications, as well as the importance of frequent soundings over important emission sources around the world.
Comparison of the Uzboi Vallis and Nirgal Vallis (Mars) using swath analysis
Authors: Szilágyi-Sándor András , Székely Balázs
Published: March 2021

The presumably fluvially affected surfaces of Mars provide evidence of the variety of surface processes of the past of the planet. Throughout its history, the climate has enabled the presence of liquid water several times (perhaps periodically). Watercourses and mega-river systems have ruled the surface; their tracks are still recognizable in many places. The Argyre Crater might have served as the source of such a huge river system: the Uzboi–Ladon–Morava River System (ULM), during the Late Noachian. (Dohm et al 2015) ULM is therefore fundamentally different from most of the valleys and channels of Mars as it is not an amphitheatre-headed valley, it is composed of various types of sections, and its source is connected to a large crater. In this study Uzboi Vallis, a section of ULM was studied using data from the Mars Global Surveyor's Mars Orbiter Laser Altimeter (MOLA) data. A comparison is presented of Uzboi Vallis and its tributary, Nirgal Vallis. In addition to creating the stream orders of the valleys and traditional elevation profiles, we used the swath profile analysis method. The swath analysis is fundamentally different from elevation profiles that enhance the specific Martian conditions (impact cratering, the complete absence of the biosphere, less gravity). In addition to the swath analysis completely covering the two studied areas, several regions of the catchment were specifically analyzed. According to the results obtained, the Uzboi Vallis is at least partly tectonically modified. Based on these observations, in the northeastern part, half-graben structures are hypothesized. The method of swath profile analysis, previously not applied to Martian data, proved to be useful and provided interpretable data for the surface of a planet other than Earth.

Geomorphometric studies on terrain models are found to provide interesting information paving the way towards an in-depth understanding of this mega river system. Further analysis of the ULM is planned in the near future.

Dohm, J.M., Hare, T.M., Robbins, S.J., Williams, J.-P., Soare, R.J., El-Maarry, M.R., Conway, S.J., Buczkowski, D.L., Kargel, J.S., Banks, M.E., Fairén, A.G., Schulze-Makuch, D., Komatsu, G., Miyamoto, H., Anderson, R.C., Davila, A.F., Mahaney, W.C., Fink, W., Cleaves, H.J., Yan, J., Hynek, B., Maruyama, S. (2015): Geological and hydrological histories of the Argyre province, Mars. Icarus 253:66–98.
Role of SST for the predictability of summer atmospheric teleconnections in the Euro-Atlantic region with Self-Organising Maps
Authors: Carvalho Oliveira Julianna , Borchert Leonard , Koul Vimal , Baehr Johanna , Zorita Eduardo
Published: March 2021

We investigate the seasonal predictability of the two dominant atmospheric teleconnections associated with the North Atlantic Jet: the Summer North Atlantic Oscillation (SNAO) and East Atlantic Pattern (EAP). We go beyond standard forecast practices by combining an ensemble predictions system with a machine learning approach. Specifically, we combine on the one hand a 30-member hindcast ensemble initialised every May between 1902 and 2008 in the Max Planck Institute Earth System Model in mixed resolution (MPI-ESM-MR), with on the other hand a neural network-based classifier Self-Organising Maps (SOM) in the ERA-20C reanalysis. We use the SOM to identify a sub-ensemble in which simulated North Atlantic sea surface temperatures (SST) at the initialisation of the prediction system (i.e. April) are linked to atmospheric modes.

While we find for summer climate at 3-4 months lead time only limited predictive skill in the ensemble mean of MPI-ESM-MR, we find significant predictive skill over many areas in the SOM-based sub-ensemble. Our results suggest that the predictive skill of European summer temperatures can be linked to the predictive skill of SNAO and EAP, which stems in turn from the – with skill predictable - temperature gradient between subpolar and subtropical gyres. We also demonstrate the predictive skill is time dependent, with high skill over the late half of the time series (1955 - 2008) and low skill in the early period (1902 - 1954).
Variability of the North Atlantic Oscillation in the 20th century
Authors: Düsterhus André , Borchert Leonard , Koul Vimal , Pohlmann Holger , Brune Sebastian
Published: March 2021

The North Atlantic Oscillation (NAO) has over the year a major influence on European weather. In many applications, being it in modern or paleo climate science, the NAO is assumed to varying in strength, but otherwise often understood as being a constant feature of the pressure system over the North Atlantic. In recent years investigations on the seasonal-predictability of the winter NAO has shown that the prediction skill is varying over time. This opens the question, why this is the case and how well models are able to represent the NAO in all its variability over the 20th century.

To investigate this further we take a look at a seasonal prediction of the NAO with the Max Planck Institute Earth System Model (MPI-ESM) seasonal prediction system, with 30 members over the 20th century. We analyse its dependence of prediction skill on various features of the NAO and the North Atlantic system, like the Atlantic Multidecadal Variability (AMV). As such we will demonstrate, that the NAO is a much less stable system over time as currently assumed and that models may not be in the position to predict its full variability appropriately.
On the necessity of including vapor kinetics to model the specific surface area evolution in snow
Authors: Karpova Anna , Lehning Michael , Löwe Henning
Published: March 2021

Vapor fluxes in snow are often inferred from the temperature field by assuming vapor concentrations in local thermodynamic equilibrium with the temperature. Here we give evidence that, at the pore scale, this picture is in clear contradiction with the observed evolution of the specific surface area (SSA) under temperature gradient metamorphism. To this end, we have calculated pore-scale temperature fields using the Finite Element Method on micro-tomography images. Subsequently, we utilized the exact volume-averaged evolution equation for the SSA to infer that the disagreement stems from the employed diffusion-limited growth law which manifests in local thermodynamic equilibrium of vapor and temperature. Via sensitivity studies we confirm that this conclusion is not affected by the involved image analysis and numerical procedures. We outline how and why attachment kinetics may resolve the observed contradiction.
Geochemical study in situ (LA-ICP-MS) of ore minerals from Paleoproterozoic layered PGE intrusions in the north-eastern Fennoscandian Shield
Authors: Drogobuzhskaya Svetlana , Bayanova Tamara , Novikov Andrey
Published: March 2021

The laser ablation inductively-coupled plasma mass spectrometry (LA-ICP-MS) is a unique method for local analysis that allows studying mineral grains in situ. The aims of these geochemical researches are to estimate concentrations and distributions of PGE and other siderophilic and chalcophilic elements in ore minerals from complex deposits in the Arctic region (Fennoscandian Shield), using the LA-ICP-MS local analysis of trace elements. Pyrite, pentlandite, pyrrhotite and other sulfides are important for determining platinum-group elements.

In situ analyses of sulfide crystals were carried out on polished thin sections by ICP-MS. The electron (LEO-1415) and optic (LEICA OM 2500 P, camera DFC 290) spectroscopy was applied to study the morphology of the samples. Analytical points on sulfide minerals were selected using microelectronic and optical images.

PGE and other elements (As, Bi, Cd, Cr, Co, CuFe, Ni, Se, S, Sn, Sb, Pb, Re, Te, Tl, Zn, Hf, Th, U, REE) were measured by ICP-MS, using an ELAN 9000 DRC-e (Perkin Elmer) quadrupole mass spectrometer equipped with a 266 nm UP-266 MAСRO laser (New Wave Research). NIST 610, NIST 612 and tandem graduation (using solutions), considering sensitivity coefficients of isotopes were used to check the accuracy of estimations. Fe, Ni and Cu were used as internal standards, being most evenly distributed elements in minerals, when concentrations of elements in sulfides were calculated. The estimates were carried out, using inter-laboratory standards of chalcopyrite, pentlandite and pyrrhotite, which had been preliminarily prepared and studied using microprobe analysis (Cameca MS-46).

Data on concentrations of PGE, Au and Ag in sulfides, including data on their distribution in minerals, are crucial in studying the origin of noble metals in sulfide ores and interpreting formation settings of complex deposits. Estimated concentrations of other trace elements provide an essential supplement to geochemical data. Received data are new data (LA-ICP-MS) of Pt-Pd and Cu-Ni reefs of the Monchegorsk ore areas (2.5 Ga) with prospected commercial deposits. Elaborated LA-ICP-MS techniques were applied to provide in situ measurements of noble metals (PGE, Au, Ag), as well as siderophilic and chalcophilic elements, in sulfide minerals in order to study their distributions in chalcopyrite, pentlandite and pyrite from the Pechenga and Allarechka Cu-Ni deposits (1.98 Ga), Fedorova Tundra and Severny Kamennik PGE deposits (2.5 Ga).

 

The scientific researches are supported by RFBR Grant No 18-05-70082, scientific themes 0226-2019-0032 and 0226-2019-0053.
Tectonic constraints on submarine hydrothermal activity, degassing, and subseafloor gas storage (Milos Shallow Water Hydrothermal System, Greece)
Authors: Escartín Javier , Hughes Alex , Martelat Jean-Emmanuel , Puzenat Valentine , Barreyre Thibaut , Nomikou Paraskevi , Jouvé Guillaume , Bouchard Alban , Stephan Remi , Philippe Alain , Delescluse Mathias
Published: March 2021

The Milos hydrothermal field is one of the largest known shallow water hydrothermal systems, and shows both fluid and gas outflow through the seafloor. Recent studies based on imagery acquired by both aerial and submarine drones (Puzenat et al., submitted) reveal several types of fluid outflow associated with bacterial mats along the SE coast of the island (Paleochori, Spathi, and Agia Kyriaki bays). From these observations? include: a) zones of polygonal hydrothermal outflow and associated bacterial mats, b) extended white (bacterial) patches, and c) isolated ones. Subseafloor hydrothermal circulation is hosted in sediments with subseafloor temperatures >50°C, and there is a clear association between hydrothermal circulation and active degassing.

To understand the controls on and relationships between fluid and gas outflow in the area, we need to characterise: a) the nature of the subseafloor (sediment thickness, composition & permeability); b) the distribution of gas and subseafloor fluids, and c) the distribution of gas flares emanating from the seafloor. In November 2020, we conducted a short pilot geophysical study at Paleochori Bay, deploying a towed catamaran with a multibeam echo sounder (iXblue Seapix) to obtain seafloor bathymetry, acoustic backscatter and water column detection of gas flares. We also deployed a sub-bottom profiler (iXblue Echoes 3500 T1) to image sediment architecture and gas/fluid diffusion within the sediment. Our survey focused on Paleochori Bay, surveing areas from ~5 m (nearshore) to ~100 m waterdepth (offshore).

Preliminary results of this geophysical survey suggest that subseafloor gas accumulations play a major role on the nature and structure of hydrothermal activity at Milos. These gas accumulations within the sediments develop along an onshore/offshore fault system, and likely control the shallow subseafloor thermal structure, establishing a thin thermal conductive layer between the roof of gas pockets and the seafloor.[GJ1] [je2]   We will report on the link between the distribution and geometry (extent, depth, acoustic nature of the accumulations) of gas pockets, fluid outflows, and gas outflows, all of which will be characterised from both seafloor imagery and subsurface geophysical surveys. We will also discuss how gas pocket geometry may be linked to both fluid flow and subseafloor temperature structure. [HA3] 

 

 

 
Modeling of the impact of rigid ellipsoidal blocks by means of an elastic-visco-plastic constitutive model 
Authors: Dattola Giuseppe , Crosta Giovanni Battista , di Prisco Claudio Giulio
Published: March 2021

Rockfall is one of the most common hazards in mountain areas causing severe damages to structures/infrastructures and, human lives. For this reason, numerous are the papers published in the last decades on this subject, both introducing reliable approaches to simulate the boulder trajectory and defining design methods for sheltering structures. As is well known, the most popular strategy to simulate the block trajectory and velocity is based on the lumped mass material point approach. This is capable of describing the block trajectory, before either its natural arrest or impact against an artificial/natural obstacle, by suitably considering its interaction with soil/rock materials, interaction always dynamic, very often highly dissipative and defined, according to its nature, as sliding, rolling or impact.

In this framework, this study focusses on impacts and, in particular, on the role of block geometry in affecting the block kinematic response. The problem is approached numerically; by modifying a previously conceived elastic-viscoplastic constitutive model, based on the macro-element concept. and capable of satisfactorily simulating impacts of spherical blocks.

The modified constitutive model relaxes the assumption of spherical block by assuming an ellipsoidal shape and by allowing for the boulder rotation. These two changes make the problem more complex but allow to model more realistically the impact. For the sake of simplicity, the results shown in this work consider the block motion to be planar, but the model already allows to include general three dimensional conditions.

In this work, the model is briefly outlined and the procedure for calibrating the model constitutive parameters described. Then, the results of an extensive parametric analysis, employing constitutive parameters calibrated on experimental data taken from the literature, are discussed. In particular, the role of (i) the inner block orientation, and (ii) the inner impact angle is considered in terms of both kinematic variables and restitution coefficients. Finally, interpolation functions to compute restitution coefficients, once both block shape and inner impact block orientation are known, are provided.
Comparison of Microporous Minerals for Potential Contaminant Uptake
Authors: Osorio Marvin , Oze Christopher , Celestian Aaron
Published: March 2021

Microporous minerals have many industrial applications, from filtration to contaminant immobilization. Natural and synthetic minerals, including zeolites, clays, and silica aerogel, represent a few examples of microporous minerals with distinctive structures, surface charges, and porosity. Analysis and comparison of their crystal structures are necessary to determine how each mineral may be suited for contaminant uptake. Here we assessed the structure of microporous minerals, specifically rowleyite, clinoptilolite, vermiculite, and silica aerogel.  Raman spectroscopy, X-ray fluorescence, and X-ray powder diffraction were used to create and model atomic mineral structures to visualize atomic and macroscope features. Taking into account pore size and surface charge each mineral was reviewed to find the best fit with regards to heavy metal uptake, mainly Pb (lead). Overall, we provide a comparative framework to assess microporous minerals that will inform future flow-through experiments for heavy metal uptake.
Statistical modelling of intermittence metrics in temporary rivers of the UK
Authors: Eastman Michael , Parry Simon , Sefton Catherine , Park Juhyun , England Judy
Published: March 2021

Lack of monitoring of the IRES network limits the potential to develop current understanding of these critical landscape features. Simulation offers potential to improve the spatiotemporal extent and resolution of the available evidence, enabling further research to be performed and understanding developed. Previous research has demonstrated the potential for statistical models to accurately reconstruct the spatiotemporal dynamics of intermittent rivers.

In this study ordinal regression models were trained to simulate the hydrological regime for the first time, enabling the simulation of flowing, ponded and dry dynamics using localised environmental variables, site characteristics and seasonality. This was enabled by a dataset covering the full range of hydrological conditions of ten chalk streams in the Chiltern Hills, UK over the last 23 years.

The hydrological regime was accurately simulated using ordinal regression models, with weighted f-scores ranging from 0.759-0.955, and scores exceeding 0.935 in the six most westerly streams. This apparent west-east pattern was also present in other evaluation metrics, with probability of detection scores ranging from 0.954 to 0.973 in the westerly streams, and 0.775 to 0.908 in the east, and Correct Classification Rate ranging from 0.935 to 0.955 in the west, and 0.849 to 0.909 in the east. The apparent relationship between model performance and BFI suggests groundwater influence on the hydrological regime    

Further research provided further insights into controls on model performance, including groundwater influence, prominence of ponding and the relatively rapid response of the easterly streams. In addition to improved understanding of controls on model performance, the accurate reconstruction of hydrological regime in these rivers facilitates research from linking associated data to previously unavailable hydrological state data, to investigating climate change impacts and influence of abstraction pressures on these invaluable ecosystems.
Flood risk management in Ghana: gaps, opportunities, and socio-technical tools for improving resilience
Authors: Evers Mariele , Almoradie Adrian , de Brito Mariana M. , Höllermann Britta , Ntajal Joshua , Lumor Mawuli , Bossa Aymar , Norman Charlotte , Yira Yacouba Yira Yacouba , Jean Hounkpe Jean Hounkpe
Published: March 2021

Ghana is one of the countries most prone to floods in West Africa. Its annual occurrence often leads to disasters that are mostly felt by the urban poor. Despite the existence of salient activities conducted in order to reduce the flood risk in Ghana, there are still persisting challenges. Here, we evaluate these gaps and describe opportunities for further improving flood risk management (FRM) in Ghana. A mixed-method participatory approach comprising questionnaires, workshops, interviews with key stakeholders, and a systematic literature review were employed (Almoradie et al. 2020). Existing problems, discourses, FRM practices, and opportunities to enhance flood resilience were identified. Based on that, potential research directions on how to tackle these challenges were outlined. Results showed that the stakeholders interviewed construct the effectiveness of FRM differently and even in contradictory ways, embedded in diverse storylines. Furthermore, we found that Ghana’s FRM is still reactive rather than preventive and that research in the field of quantitative hazard and risk assessment is rather rudimentary. FRM policies and tools such as flood early warning systems (FEWS) are in place, but efforts should be directed towards their implementation and monitoring, investigation of socio-technical capacity aspects, and enhancement of institutions’ mandates, functions, and coordination. Based on these findings, we conceptualized a research and development project, which is based on participatory research, aiming to tackle some of the identified issues. To this end, we will implement a collaborative modelling approach and will develop a socio-technical tool, which comprises: (1) a tailored decision support system, (2) a citizen science-based data collection system, (3) a flood forecasting tool, and (4) an approach for modelling cascading risks.

Almoradie, A.*, de Brito, M.M.*Evers, M., Bossa, A., Lumor, M., Norman, C., Yacouba, Y., Hounkpe, J. (2020) Current flood risk management practices in Ghana: gaps and opportunities for improving resilience. International Journal of Flood Risk Management, doi:10.1111/jfr3.12664.
Towards Real-Time Moment Tensor Inversions in a Data Rich Micro-Seismic Environment using Deep Learning
Authors: Nooshiri Nima , Bean Christopher J. , Grigoli Francesco , Dahm Torsten
Published: March 2021

Despite advanced seismological methods, source characterization for micro-seismic events remains challenging since current inversion and modelling of high-frequency waveforms are complex and time consuming. For a real-time application like induced-seismicity monitoring, these methods are slow for true real-time information because they require repeated evaluation of the often computationally expensive forward operation. Moreover, because of the low amplitude and high-frequency content of the recorded micro-seismic signals, routine inversion procedure can become unstable and manual parameter tuning is often required. Therefore, real-time and automatic source inversion procedures are difficult and not standard. A more promising alternative to the current inversion methods for rapid source parameter inversion is to use a deep-learning neural network model that is calibrated on a data set of past and/or possible future observations. Such data-driven model, once trained, offers the potential for rapid real-time information on seismic sources in a monitoring context.

In this study, we investigate how a supervised deep-learning model trained on a data set of synthetic seismograms can be used to rapidly invert for source parameters. The inversion is represented in compact form by a convolutional neural network which yields seismic moment tensor. In other words, a neural-network algorithm is trained to encapsulate the information about the relationship between observations and underlying point-source models. The learning-based model allows rapid inversion once seismic waveforms are available. Moreover, we find that the method is robust with respect to perturbations such as observational noise and missing data. In this study, we seek to demonstrate that this approach is viable for micro-seismicity real-time estimation of source parameters. As a demonstration test, we plan to apply the new approach to data collected at the geothermal field system in the Hengill area, Iceland, within the framework of the COSEISMIQ project funded through the EU GEOTHERMICA programme.
Exploring the Vis-NIR wavelength importance in SOC models under field and lab conditions in a long-term field experiment
Authors: Reyes Javier , Ließ Mareike
Published: March 2021

Soil organic carbon (SOC) is of particular interest in the study of agricultural systems as an indicator of soil quality and soil fertility. In the use of Vis-NIR spectroscopy for SOC detection, the interpretation of the spectral response with regards to the importance of individual wavelengths is challenging due to the soil’s composition of multiple organic and minerals compounds. Under field conditions, additional aspects affect the spectral data compared to lab conditions. This study compared the spectral wavelength importance in partial least square regression (PLSR) models for SOC between field and lab conditions. Surface soil samples were obtained from a long-term field experiment (LTE) with high SOC variability located in the state of Saxony-Anhalt, Germany. Data sets of Vis-NIR spectra were acquired in the lab and field using two spectrometers, respectively. Four different preprocessing methods were applied before building the models. Wavelength importance was observed using variable importance in projection. Differences in wavelength importance were observed depending on the measurement device, measurement condition, and preprocessing technique, although pattern matches were identifiable, especially in the NIR range. It is these pattern matches that aid model interpretation to effectively determine SOC under field conditions.
A pan-Arctic algorithm for DOC concentrations from CDOM spectra
Authors: Gonçalves-Araujo Rafael , Granskog Mats , Osburn Christopher , Stedmon Colin
Published: March 2021

The surface layer of the Arctic Ocean carries a higher dissolved organic carbon (DOC) content than other ocean basins. Climate change impacts the Arctic aquatic DOC-pool by e.g., introducing DOC trapped in permafrost soils as they thaw and by increasing the terrestrial runoff and primary production. Sampling for DOC in the Arctic is rather challenging given its remoteness and difficult access to the region and that it is not possible yet to determine DOC concentrations from instruments deployed in the field. Compared to DOC, colored dissolved organic matter (CDOM) absorption spectroscopy is an easy-to-measure, relatively quick and cost-effective approach which is often closely related to DOC concentrations in water samples. In regions in close proximity to rivers, linear relationships between CDOM absorption at 350nm (a350) and DOC often can be found and, thus, have improved prediction of DOC using two end‐members. However, in regions with two or more end‐members of comparable DOC concentrations (shelf seas and oceanic waters) these relationships are difficult to derive, as there might be pools of similar concentration/intensity but different ratio of absorption to DOC (carbon specific absorption coefficient, a*). Here we present an algorithm to estimate DOC concentrations based on quantitative (a350) and qualitative (spectral absorption slope between 275 and 295nm, S275-295) properties of CDOM. The algorithm considers that there is a linear correlation between DOC and a350 but that the slope of the relationship (inverse of a*) varies depending on the exponent of the ultraviolet (UV) spectral slope (S275‐295), that is, the character or source of DOM. We compiled a Pan-Arctic dataset (n=3607) from a wide range of aquatic systems spanning lakes, rivers, estuaries, coastal and shelf seas and open ocean with salinity ranging from 0 to 35.3. DOC ranged between 19 and 2304µM, whereas a350 varied from 0.01–81.33m-1 and S275-295 ranged 12–39µm-1. The algorithm provided significant and robust (r2=0.93; p<0.0001) DOC estimates (pDOC), ranging 1–2598µM (RMSE=64µM). This indicates that, besides its simplicity, this method is capable of capturing the extremely high variability of DOC within the broad gradient of Arctic aquatic systems considered in this study. Apart from that, pDOC estimates could reproduce both DOC profiles and the DOC vs. salinity relationship across the Arctic Ocean (i.e., distinct sites with highly distinct hydrographic conditions). This potentially makes the method suitable for high-resolution and long-term in situ monitoring of DOC concentrations in Arctic aquatic systems from e.g., absorbance measurements from in situ nitrate sensors.
The GMAO High‐Resolution Coupled Model and Assimilation System for Seasonal Prediction
Authors: Molod Andrea ,   GMAO Seasonal Prediction Development Group
Published: March 2021

The Global Modeling and Assimilation Office (GMAO) is about to release a new version of the Goddard Earth Observing System (GEOS) Subseasonal to Seasonal prediction (S2S) system, GEOS‐S2S‐3, that represents an improvement in performance and infrastructure over the  previous system, GEOS-S2S-2. The system will be described briefly, highlighting some features unique to GEOS-S2S, such as the coupled interactive aerosol model and ensemble  perturbation strategy and size. Results are presented from forecasts and from climate  equillibrium simulations. GEOS-S2S-3 will be used to produce a long term weakly coupled reanalysis called MERRA-2 Ocean.

The climate or equillibrium state of the atmosphere and ocean shows a reduction in systematic error relative to GEOS‐S2S‐2, attributed in part to an increase in ocean resolution and to the upgrade in the glacier runoff scheme.  The forecast skill shows improved prediction  of the North Atlantic Oscillation, attributed to the increase in forecast ensemble members.  

With the release of GEOS-S2S-3 and MERRA-2 Ocean, GMAO will continue its tradition of maintaining a state‐of‐the‐art seasonal prediction system for use in evaluating the impact on seasonal and decadal forecasts of assimilating newly available satellite observations, as well as evaluating additional sources of predictability in the Earth system through the expanded coupling of the Earth system model and assimilation components.
Frictional properties of a faulted shale gas play: implications for induced seismicity 
Authors: Allen Michael John , Kettlety Tom , Faulkner Daniel R , Kendall J. Michael , De Paola Nicola
Published: March 2021

Injecting fluids into the subsurface is necessary for a number of industries to facilitate the energy transition (e.g., geothermal, geologic CO2 sequestration or hydrogen storage). One of the biggest challenges is that fluid injection induces seismicity, which can lead to damaging events. It is currently not possible to predict the exact nature of seismicity that will occur due to fluid injection prior to operations.

Using laboratory friction experiments and in-situ microseismic analyses, we investigate the role frictional behaviour may have on the rate and magnitude of induced seismicity. This study focuses on the Horn River Basin shale gas play (British Columbia, Canada), where hydraulic fracturing activity has resulted in felt induced seismicity. Microseismic data from this field highlights fault planes that cut across the stratigraphy, including overburden and reservoir shales of varying mineralogy and underburden dolomites.

Our experimental friction results on samples recovered from core at reservoir depths show that both the frictional strength and stability vary considerably across the different lithologies; transitioning from very velocity-strengthening with friction coefficients of 0.3 – 0.4 in the overburden shales to more velocity-weakening and friction coefficients of 0.55 – 0.7 in the reservoir shales and an analogue of the underburden dolomite.

Spatial clustering analysis of the microseismicity allowed us to discriminate the operationally induced fracturing from fault reactivation events. We then examined the variations in the seismic b-value of the event magnitude-frequency distribution. These events were further differentiated by depth, separating them into their lithological horizons. The results show, for both fracturing and faulting events, higher seismic b-values of 1.4 – 1.5 occur in the overburden shales, which then decrease into the upper reservoir shales to 0.8 – 1.1, and then increase into the lower reservoir shales and underburden dolomite to 1.1 – 1.4. These trends correlate well with the laboratory measurements of frictional a-b values that define the degree of velocity-strengthening to velocity-weakening in the different gouges across the same lithological units.

These results suggest that knowledge of the frictional behaviour of the subsurface prior to operations, derived from mineralogical compositions and laboratory testing on cored material, may help improve our understanding of the potential rate and magnitude of induced seismicity that may occur due to subsurface fluid injection.