bluuebunny/crossref_metadata_2025 huggingface dataset:
Evolution of detachment fault systems within necking domains: insights from the Frøya and Gossa Highs, mid-Norwegian margin
Authors: Gresseth Julie Linnéa Sehested , Osmundsen Per Terje , Péron-Pinvidic Gwenn
Published: March 2022

Within rifted margins, the necking domain corresponds to the area where drastic reduction in basement thickness leads the crust to attain a wedge-shape. The crustal thinning occurs along detachment fault systems typically recording displacements in the order of 10s of kilometers. These systems commonly shape the crustal taper and eventually the taper break, where crustal thickness is thinned to 10 km or less. In recent years, it has become clear that evolutionary models for detachment fault systems remain unsatisfactory as the well-known principles for smaller magnitude fault systems are not fully applicable to these large-magnitude systems. Consequently, the detailed responses in the foot- and hanging walls and associated basin sedimentation within detachment fault systems and necking domains remain poorly understood compared to those observed in extensional half-graben basins.

We use interpretation of 3D- and 2D seismic reflection data from the Mid-Norwegian rifted margin to discuss the effects of lateral interaction and linkage of extensional detachment faults on the necking domain configuration. We investigate how the structural evolution of these detachment faults interact with the effects of isostatic rollback to produce complex 3D geometries and control the configuration of the associated supradetachment basins. The study area demonstrates how successive incision may induce a complex structural relief in response to faulting and folding. In the proximal parts of the south Vøring and northeastern Møre basins, the Klakk and Main Møre Fault Complexes form the outer necking breakaway complex and the western boundary of the Frøya High. We interpret the previously identified metamorphic core complex within the central Frøya High as an extension-parallel turtleback-structure. The now eroded turtleback is flanked by a supradetachment basin with two synclinal depocenters resting at the foot of the necking domain above the taper break. We attribute footwall and turtleback exhumation to Jurassic-Early Cretaceous detachment faulting along the Klakk and Main Møre Fault Complexes. The study area further demonstrates how detachment fault evolution may lead to the formation of younger, successively incising fault splays locally. Consequently, displacement may occur along laterally linked fault segments generated at different stages in time. Implicitly, the detachment fault system may continue to change configuration and therefore re-iterate itself and its geometry during its evolution.
Instrument design and laboratory evaluation of the OSAS-B heterodyne spectrometer for sounding atomic oxygen in the MLT
Authors: Wienold Martin , Semenov Alexey , Richter Heiko , Dietz Enrico , Frohmann Sven , Hübers Heinz-Wilhelm
Published: March 2022

The Oxygen Spectrometer for Atmospheric Science on a Balloon (OSAS-B) is dedicated to the remote sounding of atomic oxygen in the mesosphere and lower thermosphere (MLT) region of Earth's atmosphere, where atomic oxygen is the dominant species. OSAS-B is a heterodyne receiver for the thermally excited ground state transition of atomic oxygen at 4.75 THz. Due to water absorption, this line can only be observed from high-altitude platforms such as a balloon. A combined Helium/nitrogen dewar comprises the detector of the instrument, a hot-electron bolometer mixer, as well as a quantum-cascade laser, which serves as the local oscillator for heterodyning. A turning mirror allows for measurements at different vertical inclinations and for radiometric calibration against two blackbody sources. The first flight will take place in autumn 2022 within the HEMERA2020 program. We will present the instrument design and results of the laboratory evaluation of the instrument.
Contrasting passive and transform margin tectonic history and sedimentation: insights from 3D numerical modelling and observations from the Atlantic
Authors: Balazs Attila , Gerya Taras , May Dave , Tari Gabor
Published: March 2022

Passive and transform margins emerging during continental rifting and opening of oceanic basins are fundamental elements of plate tectonics. It has been suggested that inherited structures, variable plate divergence velocities and surface processes exert a first order control on the topographic, bathymetric and magmatic evolution and thermal history of these margins and related sedimentary basins. We conducted 3D thermo-mechanical numerical experiments with the code I3ELVIS coupled to surface processes modelling (FDSPM) to simulate the dynamics of continental rifting, continental transform fault zone formation and persistent oceanic transform faulting. Numerical modelling results allow to explain the first order observations from passive and transform margins, such as diachronous rifting, strain localization into individual oblique rift basins and the opening of structurally separate oceanic basins connected in an open marine environment. In addition, the models reproduce the rise of transform marginal ridges and submarine plateaus, continental crustal slivers within oceanic transforms and their interaction with erosion and sedimentation. Model results are compared and validated by seismic and well data from passive and transform margin segments of the Atlantic.
Using the Subseasonal-to-Seasonal (S2S) Real Time Pilot (RTP) Initiative to understand the challenges and opportunities of co-production in S2S forecast application development
Authors: Robbins Joanne , Simmonds Rebecca
Published: March 2022

The aim of the Subseasonal to Seasonal (S2S) Prediction Project Real Time Pilot (RTP) Initiative is to identify best practices for the development of useful and usable, user-orientated S2S forecasts. Typically, S2S forecasts are only available to researchers with a 3-week lag, but this can represent a barrier to the development of user-orientated applications as it prevents users from being able to understand the utility of this information in real time within their decision-making frameworks. To accomplish the aims of the RTP, the initiative looked to engage with existing user-orientated projects and offer them the opportunity to access real time S2S forecast information to enable better end-to-end development and evaluation of applications. To ensure that sufficient time was available for projects and users to use and become familiar with the real time S2S forecasts, an agreement was reached where S2S forecasts would be available in real time, to a small set of projects for a 2-year period (November 2019 up to November 2021). This has since extended up to November 2022.

To address the aims of the S2S RTP a series of feedback activities have been undertaken with the 16 projects involved. This has included the dissemination and analysis of 2 sets of questionnaires, followed by more detailed semi-structured interviews and subsequent synthesis. All feedback activities were inclusive of researchers and users participating in the initiative. This presentation will describe the different approaches projects have taken in the development of S2S forecast applications, focussing on co-production and user engagement activities across the value chain. Benefits, opportunities and challenges to using co-production methods in the development of user-orientated forecasts are identified through the feedback activities and wider literature. These findings suggest that the application of co-production methods remains novel in the S2S time range, with time and resource availability for stakeholder engagement posing a challenge. However, the feedback indicates that where bi-directional interaction is sustained, positive feedback mechanisms can develop, which build trust, strengthen collaborative working arrangements and enhance forecast product development specific to user requirements.
Examining turbulent scalar exchange during a strong wind event
Authors: Hodder Wilhelm , Renfrew Ian , Elvidge Andrew , Sheridan Peter , Petersen Guðrún Nína
Published: March 2022

Various research has been conducted into the turbulent momentum fluxes in orographic flow, and is in some models parameterised to simulate orographic form drag, yet the role of turbulent exchange of heat and moisture presents a somewhat opaque picture, as these processes are generally not resolved or parameterised in NWP models.  We present results from rare, low-level leeside turbulence observations in a strong mountain wind event.  These observations were obtained in 2018 during the Iceland-Greenland Seas Project (IGP) field campaign, a coupled atmosphere-ocean project, which included two research flights over the steep and complex orography of two Icelandic peninsulas with the aim of investigating leeside turbulent exchange processes.  High resolution regional model MetOffice Unified Model (MetUM) forecasts are run and compared to in-situ observations from 12th and 19th March 2018 over the Westfjords and Snaesfellsness peninsula in north-western Iceland.  With sub-kilometre horizontal grid-cell lengths flow features such as a downslope windstorm coupled with a hydraulic jump and a wave-breaking region directly aloft are well resolved and provide suitable cases for testing different MetUM science configurations.  The evaluation of control forecasts has shown a consistent 2 K bias in the lower atmospheric boundary layer sourced from the global driving model.  Sensitivity tests are run with the aim to ultimately parameterise scalar transport of heat and moisture in the leeside orographic flow.  This presentation will outline current progress and, to a degree, will attempt to answer the question of the significance and importance of turbulent scalar exchange within a strong wind event.

Keywords: MetUM, tuurtbulent exchange, orographic, NWP, Iceland
Interplay of topography, flood frequency and soil properties determine the distribution of microplastics in a Rhine floodplain 
Authors: Rolf Markus , Laermanns Hannes , Kienzler Lukas , Pohl Christian , Möller Julia , Laforsch Christian , Löder Martin G.J. , Bogner Christina
Published: March 2022

Rivers are important transport pathways of microplastics from terrestrial to marine environments. They also interact with terrestrial ecosystems, in particular during flood events, when microplastics can be deposited in or eroded from floodplains. The spatial distribution of these riverine microplastics in alluvial floodplains remains widely unclear. However, the knowledge on their abundance and distribution in floodplain soils is essentially important for ecological risk assessment.

We analysed the distribution of microplastics in three transects of a floodplain soil in a nature reserve in Cologne (Germany). We took soil samples in two different depths (0-5 cm and 5-20 cm), described the soil profiles and plant cover and determined the soil texture. Additionally, we used a hydrodynamic model (MIKE21 software by DHI) and time series of Rhine's water level to analyse the frequency of past flood events from 1950 to 2020. We analysed concentrations of microplastics via ATR-FTIR and µ-FPA-FTIR spectroscopy after density separation and enzymatic-oxidative purification of soil samples. We found elevated microplastic concentrations per kg of dry soil with increasing distance to the river ranging from 25,616 particles/kg to 84,824 particles/kg. Combining the analysis of flood events, the digital terrain model and quantification of microplastics, we show how the local topography (e.g., depressions), flood frequency and soil properties (e.g., grain size) interact and affect the spatial and vertical distribution of microplastics.
Modeling of the CME on 2021 October 28
Authors: Valentino Angelo , Magdalenic Jasmina
Published: March 2022

We present the evolution of the CME/flare event observed on 2021, October 28 . The GOES X1.1 class flare originated from the active region NOAA AR 2887, situated at the moment of eruption close to the central meridian. The full halo CME had also on disc signatures, i.e. the EIT wave and coronal dimming and was associated with the white light shock and the type II radio burst. The CME propagated with the projected line of the sight speed of about 1100 km/s and it seemed to be Earth directed.

However, only the associated shock wave was observed by the DSCOVR in-situ instruments, in the morning of October 31. The observations indicate that the CME’s propagation direction had a strong southward component, which induced only glancing blow and not a direct impact to Earth.

We reconstructed the CME, using SOHO/LASCO and STEREO/COR observations, and modeled it’s propagation in the inner heliosphere employing recently developed heliospheric model EUHFORIA (EUropean Heliospheric FORecasting Information Asset, Pomoell & Poedts, 2018).  After accurately modeling the observed CME we also made the ensemble runs with EUHFORIA to study how the changes of the propagation direction of the CME influence its impact to Earth.

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A global statistical study on the triggering of volcanic eruptions by large tectonic earthquakes
Authors: Jenkins Alex , Rust Alison , Biggs Juliet
Published: March 2022

Recent studies have shown that large tectonic earthquakes are capable of triggering volcanic eruptions (i.e. increasing the number of eruptions within a defined time period) up to hundreds of kilometres away. However, the prevalence of eruption triggering is less clear, with findings ranging from little evidence for triggered eruptions, to a fourfold increase in the number of eruptions following nearby large earthquakes. Some of this variability is likely due to differences in definitions of what constitutes a triggered volcanic eruption, including a lack of consensus on the maximum distance and time lag between an earthquake and a triggered volcanic eruption, the minimum magnitude of earthquake considered, and how aftershocks are incorporated into the analysis. A further source of variability arises from the different datasets used, including regional versus global studies, and the inclusion of incomplete earthquake and eruption records from before the modern instrumental era. To help address these issues, we provide a comprehensive statistical study of how large earthquakes affect volcanic eruption rates, using complete and unbiased global datasets spanning 1960-2021. We take a systematic approach to investigating how parameters such as the maximum distance and time lag between earthquake-eruption pairs, the minimum earthquake magnitude considered, and the declustering of aftershocks affects the results. We also investigate how previously unstudied earthquake parameters such as source depth and mechanism affect the prevalence of eruption triggering. Our results are placed in statistical context through the use of Monte Carlo simulations using randomised earthquake and eruption catalogues. Preliminary results indicate that, contrary to a previous focus on large subduction megathrust earthquakes, deep normal faulting earthquakes have the greatest eruption triggering tendency. However, when compared with randomised earthquake and eruption catalogues, the overall statistical significance of observed eruption triggering is fairly low.
The effect of different pedotransferfunctions on the spatial distribution and intensity of runoff processes using the hydrological model WaSiM-ETH.
Authors: Jackel Mathias , Casper Markus , Mohajerani Hadis
Published: March 2022

Pedotransferfunctions (PTF) play a major role in physically based hydrological modeling, as they establish the relationship between soil properties and the water stress curve. The selection of the PTF thus has a great influence on the water balance of a catchment in general, as well as on the spatial distribution and intensity of runoff processes. In this study, these very influences of PTF's on the runoff processes will be investigated. The hydrological model "WaSiM-ETH", which was calibrated and validated, is used for the investigations. On the basis of this modeling, 11 further scenarios were created, which differ only in their PTFs. In all scenarios an artificial weather event is applied, which includes a constant heavy precipitation of 100 mm as well as input data, which excludes the generation of interfering processes e.g., evaporation or snowfall. In addition, these scenarios will be applied to different system conditions to determine the differences of dry, humid, and wet system preconditions. Ultimately, the precipitation intensity but not the amount of the artificial weather event will also be varied to be able to determine any change in the dominant runoff processes due to precipitation intensity. The results of the modeling will then be compared using the generated surface runoff, interflow, and deep infiltration. In addition, a check of the modeling with a runoff process map available for the catchment area as well as a pattern comparison using the spatial efficiency metric (SPEAF) will be performed. It is expected that the different PTF´s per se, as well as depending on the system precondition and precipitation intensity, will result in very different spatial distributions and dominance of the individual runoff processes. Thus, one goal is to find the PTF´s that provide comprehensible distributions and intensities of the considered runoff processes.
Multi-model comparison of carbon cycle predictability in initialized perfect-model simulations
Authors: Spring Aaron , Li Hongmei , Ilyina Tatiana , Bernardello Raffaele , Ruprich-Robert Yohan , Tourigny Etienne , Mignot Juliette , Fransner Filippa , Tjiputra Jerry , Sospedra-Alfonso Reinel , Frölicher Thomas , Watanabe Michio
Published: March 2022

Predicting carbon fluxes and atmospheric CO2 can constrain the expected next-year atmospheric CO2 growth rate and thereby allow to independently monitor total anthropogenic CO2 emission rates. Several studies have established predictive skill in retrospective forecasts of carbon fluxes. These studies are usually backed by perfect-model simulations of single models showing the origins of predictive skill in carbon fluxes and atmospheric CO2 concentration. Yet, a comprehensive multi-model comparison of perfect-model predictions, which can be valuable in explaining differences in retrospective predictions, is still lacking. Moreover, as of now, we don't have sufficient understanding of how well do the models predict their own integrated carbon cycles and how congruent this predictability is across models.

Here, we show the predictive skill of land and ocean carbon fluxes as well as atmospheric CO2 concentration in seven Earth-System-Models. Our first results indicate predictive skill of globally aggregated carbon fluxes of 2±1 years and atmospheric CO2 of 3±2 years. However, the regional patterns, hotspots and origins of predictive skill diverge among models. This heterogeneity explains the regional differences found in existing retrospective forecasts and backs the overall consistent predictability time-scales at global scale.
Modelling focused fluid flow: What matters?
Authors: Wang Lawrence Hongliang , Yarushina Viktoriya M. , Podladchikov Yury
Published: March 2022

Two-phase flow equations that couple solid deformation and fluid migration have opened new research trends in geodynamical simulations and modelling of subsurface engineering operations. The physical nonlinearity of fluid-rock systems and strong coupling between flow and deformation in such equations lead to interesting predictions such as the spontaneous formation of focused fluid flow in ductile/plastic rocks. However, numerical implementation of two-phase flow equations and their application to realistic geological environments with complex geometries and multiple stratigraphic layers is challenging. Here, we present an efficient pseudo-transient solver for two-phase flow equations. We first study the focused fluid flow under the viscous regime without considering the elasticity. The roles of material parameters, reservoir topology, geological heterogeneity, and porosity are investigated. We show that focused fluid channels are the natural outcome of the flow instability of the two-phase system with a low ratio (< 0.1) between shear viscosity and bulk viscosity. We also confirm the previous studies that  decompaction weakening is necessary to elongate the porosity profile. The permeability exponents play the dominant role in the speed of wave propagation. The numerical models study fluid leakage from high porosity reservoirs into less porous overlying rocks. Geological layers present in the overburden do not stop the propagation of the localized channels but rather modify their width, permeability, and growth speed. We further validate our conclusions by modelling the full two-phase system with viscoelastic rheology and elastic solid and fluid compressibility (Yarushina et al., 2015). The Deborah number (De), solid (Ks), and fluid (Kf) bulk moduli are thus introduced into the governing equations. We found that the elasticity makes a difference when the Deborah number approaches one by speeding up the channel propagation. At the same time, its effect is rather limited when Deborah's number is small (e.g., 0.1). The effects of compressibility of the solid and fluid, on the other hand, are not found significant within the reasonable ranges of the bulk moduli.

 
Measurement report: Disentangling methane and other trace gases sources and transport across the Russian Arctic from aircraft measurements
Authors: Narbaud Clement , Paris Jean-Daniel , Berchet Antoine , Wittig Sophie , Saunois Marielle , Nédelec Philippe , Belan Boris , Arshinov Mikhail , Davydov Denis , Fofonov Aleksandr , Kozlov Artem
Published: March 2022

A more accurate characterization of the sources and sinks of methane (CH4) and carbon dioxide (CO2) in the vulnerable Arctic environment is required to better predict climate change. A large-scale aircraft campaign took place in September 2020 focusing on Siberian coast. CH4 and CO2 were measured in situ during the campaign and form the core of the study. Measured ozone (O3) and carbon monoxide (CO) are used here as tracers. Compared to the reference (i.e., the seasonal value at Mauna Loa, Hawaii, US), median CH4 mixing ratios are fairly higher (1890-1969 ppb vs 1887 ppb) while CO2 mixing ratios from all flights are lower (408.09-411.50 ppm vs 411.52 ppm). We also report on 3 case studies. Our analysis suggests that during the campaign the European part of Russia’s Arctic and Western Siberia were subject to long-range transport of polluted air masses, while the East mainly was under the influence of local emission of greenhouse gases. The relative contributions of anthropogenic and natural sources of CH4 in Siberia are simulated using the Lagrangian model FLEXPART in order to identify dominant sources in the boundary layer and in the free troposphere. In western terrestrial flights, air masses composition is influenced by from wetlands and anthropogenic activities (waste management, the fossil fuel industry and to a lesser extent the agricultural sector), while in the East, emissions are dominated by freshwaters, wetlands, and the oceans, with an ambiguous contribution from likely anthropogenic sources related to fossil fuels. Our results generally highlight the importance of the contribution form freshwater and oceans emissions and, combined with the large uncertainties associated with them, suggest that the emission from these aquatic sources should receive more attention in Siberia.
Global carbon budget variations in emission-driven earth system model predictions
Authors: Li Hongmei , Ilyina Tatiana , Loughran Tammas , Pongratz Julia
Published: March 2022

Predictions of the variations in anthropogenic global carbon budget (GCB), i.e., CO2 emissions and their redistribution among the atmosphere, ocean, and land reservoirs, is crucial to constrain the global carbon cycle and climate change of the past and facilitate their prediction and projection into the future. Global carbon project assesses the GCB every year by taking into account available datasets and stand-alone model component simulations. The utilization of different data sources leads to an unclosed budget, i.e., budget imbalance. We propose a novel approach to assess the GCB in decadal prediction systems based on emission-driven earth system models (ESMs). Such a fully coupled prediction system enables a closed carbon budgeting and therefore provides an additional line of evidence for the ongoing assessments of the GCB.

As ESMs have their own mean state and internal variability, we assimilate ocean and atmospheric observational and reanalysis data into Max Planck Institute Earth system model (MPI-ESM) to reconstruct the actual evolution of climate and carbon cycle towards to the real world. In the emission-driven model configuration, the carbon cycle changes in response to the physical state changes, in the meanwhile, the feedback of atmospheric CO2 changes to physics are also considered via interactive carbon cycle. Our reconstructions capture the observed GCB variations in the past decades. They show high correlations relative to the assessments from the global carbon project of 0.75, 0.75 and 0.97 for atmospheric CO2 growth, air-land CO2 fluxes and air-sea CO2 fluxes, respectively. Retrospective predictions starting from the reconstruction show promising predictive skill for the global carbon cycle up to 5 years for the air-sea CO2 fluxes and up to 2 years for the air-land CO2 fluxes and atmospheric carbon growth rate. Furthermore, evolution in atmospheric CO2 concentration in comparing to satellite and in-situ observations show robust skill in reconstruction and next-year prediction.  
Investigation of non-linear behavior of hard rock using relative seismic velocity changes - a case study at the GERES array in Germany 
Authors: Kramer Richard , Lu Yang , Delorey Andrew , Bokelmann Götz
Published: March 2022

Variations in strain/stress and fluid content can change seismic velocities in the subsurface. Monitoring velocity changes, e.g., using ambient seismic noise, may thus constrain these variations as well as the material elastic properties and their non-linear behaviour. We can test this capability by inspecting velocity changes from known effects, such as tides, temperature or atmospheric pressure affecting the upper crust. Here we present a workflow to use ambient seismic noise to derive the non-linear behaviour of hard rocks during the influence of tides, temperature and atmospheric pressure. We study one year of data from the GERES array in south Germany, which provides data to the Comprehensive Nuclear Test Ban Treaty Organization (CTBTO). The seismological GERES array consists of 25 high-quality stations located in concrete vaults with depths between 3 and 5 meters. The aperture is 4 km. We estimate hourly Green’s function by cross-correlating ambient seismic noise recorded at pairs of stations. A Wiener filter increases the signal-to-noise ratio and stabilizes the hourly calculation of relative seismic velocity change in the 1-4 Hz frequency band. We compare different techniques to measure seismic velocity changes with high precision in time, frequency, and wavelet domain. The results indicate short and long term variations of the seismic velocities. This study aims to compare this non-linear behaviour of hard rocks with other geological settings used in earlier investigations.
Hydropower Portfolio Site and Design using a Simulation - Optimisation Model incorporating High Resolution Hydraulic Modelling in Data Scarce Regions
Authors: Hatchard Simbi , Schmitt Rafael J. P. , Pianosi Francesca , Savage James , Bates Paul
Published: March 2022

Development of hydropower in developing countries carries economic development rewards, particularly for storage hydropower which can be used to balance fluctuating supply of other renewables. Yet, dams and reservoirs carry significant environmental impacts, e.g., network fragmentation and flow alteration. While flood control has often been a motivator for reservoir construction, one environmental impact of storage hydropower on tropical rivers is the reduction of peak flows resulting in less hydraulic connectivity between floodplains and channels. In many tropical rivers, where most future dams are planned, this reduced lateral connectivity will create negative impacts on biodiversity, the biophysical functioning of floodplains, and human uses such as recession agriculture. Determining the optimal siting, design, and operation (SDO) of dam portfolios which maximises power generation and minimises this environmental impact, e.g., in terms of maintaining lateral connectivity, is a complex problem.

Simulation - Optimisation models of hydropower portfolios have often included impact on annual flood peak as a proxy objective for floodplain impacts, but have rarely explicitly included inundated area as an objective. Furthermore, when this type of analysis is done, it is usually performed at a monthly timescale, which underestimates flood peaks and neglects in-channel and floodplain hydraulics.

This work presents a multi-dam simulation - optimisation framework which uses a high-resolution hydrodynamic modelling framework (LISFLOOD-FP) to explicitly model the impact of SDO of many different dam portfolios on inundated floodplain extent, and to include this modelled extent as an optimisation objective. This incorporates channel and floodplain hydraulics at a fine time resolution, allowing a more realistic representation of the impact of hydropower development on biodiversity.

The optimisation framework is applied to the data scarce Pungwe Basin in Mozambique / Zimbabwe, and identifies significant trade-offs from mainstem damming between power production and downstream hydraulic connectivity between rivers and floodplains. It identifies Pareto Optimal combinations of site and design (large dam, small dam, and run-of-the-river installations) for these two objectives. The inclusion of hydraulically modelled inundated area represents a step forward for increasing the ability of simulation - optimisation frameworks to model complex downstream impacts of hydropower development and operation related to changing discharge and channel hydraulics.
Sub-rock typing and its influence on pore-scale, image-based simulations of multiphase flow in complex geological rocks
Authors: Wang Shan , Ruspini Leonardo C. , Øren Pål-Eric , Van Offenwert Stefanie , Bultreys Tom
Published: March 2022

Image-based pore-scale modeling is an important method to study multiphase flow in permeable rocks. However, many rocks have pore size distribution that are so wide that they cannot be resolved in a single pore-space image. The accurate identification and characterization of this sub-resolution porosity have received extensive attention, due to its crucial impact on porosity and permeability estimation. To date, several modeling methods incorporate this information to improve the simulation of multiphase flow in complex rocks. The challenge is that the microporosity’s flow properties are difficult to characterize in images, and to include in models, of representative volumes. In this study, a novel sub-rock typing method was proposed to better characterize and classify microporous regions in rock samples, and to reduce the uncertainty of image-based pore-scale modeling of such samples. To this end, we performed capillary drainage experiments with brine and decane on two water-wet rock samples (Estaillades limestone and Luxembourg sandstone). Laboratory-based Micro-CT was used to image intricate pore structures and fluid occupancy changes at controlled capillary pressure steps during drainage. We proposed a novel workflow to generate 3D, micrometer-scale capillary pressure maps, which we combined with porosity maps to classify zones of microporosity types (sub-rock types). This was used to extract multi-scale pore network models and perform multiphase flow simulations. We found that the new approach yielded a good match with macroscopic experimental measurements, and significantly improved the prediction accuracy of the fluid distributions on a pore-by-pore basis. The results illustrate the importance of characterizing microporosity for simulations in heterogeneous rocks. The workflow can be applied to other complex geological porous rocks to improve modeling and simulation of subsurface multiphase flow.
Deciphering rock cooling histories in the European Alps using ESR and OSL thermochronometry
Authors: wen xiaoxia , Bartz Melanie , Anderson Leif , King Georgina
Published: March 2022

The impact of Quaternary glaciation on rates of erosion and the timing of Alpine valley incision remains disputed. This is mainly due to a lack of geochronological methods that cover the timespan of 103-106 years. While conventional thermochronometers like (U-Th-He) in apatite can constrain timescales of 106 years, and cosmogenic nuclide (CN) dating timescales of 101-103 years, it remains difficult to resolve changes in erosion rates at the timescale of glacial/interglacial cycles. To fill this temporal gap, we develop electron spin resonance (ESR) thermochronometry using both the Al and Ti centres in quartz. The combination of ESR and optically stimulated luminescence (OSL) thermochronometry, as well as numerical modelling approaches, will allow the development of a multi-thermochronometric system to understand rock cooling histories, enabling changes in erosion rates to be related to glacial advance and retreat.

 

In this study, we focus on the western European Alps, which were intensively glaciated during the Quaternary. Three vertical transects are targeted in the Rhône valley, which is thought to have substantially deepened around 1 million years ago[1]. The first transect consists of seven quartz samples, which were used for (i) optimizing the measurement protocols (i.e., preheat conditions, dose recovery), (ii) analyzing ESR signal growth and thermal stability of the Al and Ti signals to estimate kinetic trap parameters; and (iii) inverting the ESR data to constrain rock cooling histories.

 

A series of laboratory experiments show the potential of the single aliquot regenerative dose protocol. The Al and Ti signals show similar thermal stability between different samples in the same transect and yield mid-Pleistocene ages. Preliminary inversion of the data shows that the low closure temperatures of the Al and Ti signals in quartz allow the Late Quaternary exhumation of the Alpine valleys to be resolved. Our new ESR thermochronometry results will be supported by OSL thermochronometry measurements, CN dating and also the high density of existing thermochronometric data [e.g. 1] providing new insights into the glacial incision history during the Quaternary and especially how erosion rates varied temporally under a changing climate.

 

Keywords glacial erosion; landscape evolution; ESR; European Alps

 

Reference:

[1] Valla, P.G., D.L. Shuster, and P.A. van der Beek. 2011. Significant increase in relief of the European Alps during mid-Pleistocene glaciations, Nature Geoscience. 4(10): p. 688-692.
Volcanic geomorphosites, places of geotouristic interest and geo-routes in La Palma (Canary, Spain) 
Authors: Hernández William , Dóniz Javier , Hernández Pedro A. , Pérez Nemesio M.
Published: March 2022

Tourism is one of the economic activities of reference throughout the world despite the consequences of SARS-CoV-2. Within the new tourism products, geotourism is a relatively new modality and alternative to mass tourism in mature destinations. One example of this is the creation and rise of the global and European networks of geoparks. In the case of the Canary Islands, this fact can also be seen in the increase in tourist activities related to volcano tourism as an alternative product to sun and beach tourism. In this sense, the main objective of this study is to identify, inventory, select, characterize and evaluate geomorphosites with geotouristic interest on the Canary Island of La Palma following the methodology proposed by Reynard et al (2007 and 2017), based on the evaluation of scientific and added values. A total of 47 geomorphosites of geotourism interest (Ligts) that host the geodiversity of volcanic and non-volcanic forms and processes of La Palma have been studied. The main results after applying the assessment is that the scientific values ​​(0.53) are above the added values ​​(0.43). Among the first, the paleogeographic interest stands out (0.61) and of the added ones, that of the protection of the site (0.71). All these evaluations show that the geomorphological sites studied are representative of the natural and cultural heritage of La Palma, but also that they are conserved, protected and that they contribute to explain the geological and geomorphological evolution of the island. These aspects are essential to be able in the future to propose itineraries or georoutes of volcano tourist interest.
Soil Hydraulic Properties and Water Flow Estimation Using Uni- and Bimodal Porosity Models in Erosion-Affected Hillslope 
Authors: Filipović Vilim , Defterdarović Jasmina , Krevh Vedran , Filipović Lana , Magdić Ivan , He Hailong , Haghverdi Amir , Gerke Horst H.
Published: March 2022

Soil degradation processes, such as erosion, has been reported as one of the main concerns in agricultural areas. The resulting erosion-affected soils are characterized by modified soil hydraulic and other properties, strongly affecting the agricultural productivity. The study objective was to identify hydropedological factors controlling soil water dynamics in erosion-affected hillslope vineyard soils and to test uni- and bimodal porosity models. The hydropedological study was conducted at three locations: Jastrebarsko (location I), and Jazbina (II) and (III). The selected sites had same agricultural management practices and similar slope with identified Stagnosol soil type. Soil Hydraulic Properties (SHP) were estimated using Evaporation and WP4C methods on intact soil cores while the soil hydraulic functions were fitted using uni- and bimodal porosity models in HYPROP-FIT software. The study illustrated that erosion-affected soil structural properties governing hillslope hydrology in the arable landscape, in this case, vineyards, were evident and had a significant impact on SHP and, consequently, soil water dynamics. Both unimodal and bimodal soil hydraulic models fitted the data agreeably; although, it can be clearly noticed that the bimodal model performed better in particular cases where data showed non-uniform pore size distributions. HYDRUS-1D simulations showed, in general, that both models provided a similar distribution of flux components between infiltration, surface runoff, and drainage (bottom flux) in most cases. Overall, the differences generated when using the bimodal hydraulic functions can lead to a large discrepancy in water flow quantification. It is evident that the SHP and water dynamics in highly erosion-affected heterogeneous soils with developed structure and pore space (e.g., compacted soil with cracks and biopores) cannot be adequately explained using the unimodal porosity functions or by applying single porosity models. However, the validity of more complex approaches should be further tested, and parametrization should be performed with extra care, as using the non-appropriate model can lead to errors in the water balance.
Sulfide trace element signatures as a tracer for low- and high-temperature processes in serpentinites
Authors: Kalter Malte , Schwarzenbach Esther M. , Menne Falco , Oelze Marcus , Whitehouse Martin J. , John Timm
Published: March 2022

Serpentinization of ultramafic rocks at mid oceanic spreading ridges is an important sink for reduced seawater sulfate. During the dehydration of serpentinites in subduction zones volatile phases like sulfur can be leached out or further transported into the mantle. For understanding the fate of sulfur in subduction zones, it is crucial to identify the signature of sulfides during the process of hydration. The reduction of seawater sulfate takes place under isotopic fractionation of sulfur. Generally, positive δ34S values are a result of high temperature thermochemical reduction of SO4 to H2S while negative δ34S are a result of microbial sulfate reduction under low temperatures. High temperature fluids are typically derived from interaction with gabbroic intrusions before they alter the ultramafic host rocks. In contrast, low temperature fluids can be derived from relatively unmodified seawater. Therefore, these fluids imprint different metal concentrations during concurrent sulfide precipitation. Here we study ODP (Ocean Drilling Program) samples from the Iberian Margin and 15°20'N Fracture Zone along the Mid-Atlantic Ridge together with samples of ophiolitic serpentinites from the Northern Apennines. We present in situ δ34S and trace element signatures in sulfides to provide new insights into fluid sources and temperature conditions during water-peridotite interaction. High temperature fluids precipitate sulfides with stronger enrichments in metals like Cu, Co and Ni compared to sulfides formed from low temperature fluids. In respect to mafic dominated systems, sulfides from high temperature fluids of ultramafic systems show distinct enrichments in Ni. As a consequence, the combination of variations in δ34S and trace element signatures can be used to trace back the tectonic environment in which the sulfides formed and maybe used as a tracer for sulfide formation in subduction zones.
Experimental study on the failure modes and process of the overtopping breaching of noncohesive landslide dams
Authors: Zhu Xinghua , Kang Yongchuang , Kong Jinwen
Published: March 2022

The failure of landslide dams is a sudden geological disaster, with its formation and failure greatly threatening the security of local people’s lives and property. In this research, we conducted 12 sets of model experiments, considering the influence of different angle of flume bed, dam heights, and downstream slopes on the process of overtopping breaching of noncohesive landslide dams. Based on these experimental results, we analyzed the characteristics of the longitudinal and transverse evolution, and outburst discharge of landslide dams in detail. At first, we divided the failure process of landslide dams into four stages, including initiation, headward erosion, downcutting erosion, and riverbed rebalancing. In addition, the quantitative analysis of breaching evolution model and the numerical method for simulating landslide dam failure due to overtopping has also been introduced in this research. This paper provides the research basis for the following two papers, which also provide a scientific reference for the prevention and mitigation of landslide dams.
Hydrometeorological thresholds based on catchment storage to predict changes in debris-flow susceptibility after the Wenchuan earthquake (Sichuan, China)
Authors: Greco Roberto , Marino Pasquale , Fan Xuanmei
Published: March 2022

After the 2008 Wenchuan earthquake (Mw 7.9), increased occurrence of rainfall-induced debris flows was initially observed in the earthquake-hit region (Sichuan, China). In the following years, the frequency of debris flows gradually reduced, indicating a progressive recovery of stability of debris deposits accumulated along slopes and in gullies after the earthquake. To assess these dynamically changing conditions, empirical thresholds have been identified to predict post-seismic debris flow occurrence with two approaches: a meteorological approach based only on precipitation characteristics, and a hydrometeorological approach that also considers the hydrologic conditions before the onset of rainfall. Both used the available record of precipitations and debris flows that occurred between 2008 and 2015 in several gullies, tributary of the upper Minjiang river course, in Wenchuan county. Hydrometeorological thresholds for debris flows were identified at the gully catchment scale, by assessing the water balance with a simplified lumped hydrological model, based on the Budyko framework. The parameters of the model were estimated based on the scarce available information about the water balance of the entire watershed of the upper Minjiang. Simulated catchment water storage was used as a proxy of the moisture state of the slopes. The results indicate that both meteorological and hydrometeorological thresholds allow catching the progressive recovery of stability of the debris deposits. Specifically, the assessment of water balance at the catchment scale highlights the role played by the hydrological processes affecting the slopes, leading to the definition of reliable thresholds, that resulted robust despite the uncertainty of the estimated parameters of the hydrological model. Therefore, the hydrometeorological approach appears suitable to define thresholds for early warning of debris flows at the catchment scale.
Exposure to past disasters related to hydrological hazards: the case of Bujumbura city, Burundi
Authors: Nsabimana Jean , Henry Sabine , Ndayisenga Aloys , Kubwimana Désiré , Dewitte Olivier , Kervyn de Meerendré François , Michellier Caroline
Published: March 2022

Disasters related to hydrological hazards are frequent, occur worldwide, and regularly devastate many African cities. The victims are commonly among the population in precarious situations, without solid infrastructure and with incomes too low to recover from disasters.

Located in the western branch of the East African Rift, and squeezed between the shore of Lake Tanganyika and steep hillslopes, the city of Bujumbura hosts approximately 800,000 people. It is regularly affected by disasters related to lake and river floods, flash floods, riverbank collapses, and gullies. This research aims to assess people's vulnerability to these hydrological processes through the analysis of the territorial vulnerability of the city. To achieve this objective, we present here the first step which focuses on the evaluation of the exposure to past hydrological disasters.

We built a comprehensive dataset using information from different sources, such the Civil Protection, that we combined and complemented with field data collection obtained from qualitative and quantitative surveys. Given the limited information on the susceptibility to the various processes studied, the distribution of past disasters is used as an indicator of the exposure of different parts of the city to hydrological hazards. This phenomenological approach is a key step to map and understand risk due to hydrological hazards.

Between 1990 and 2021, the city recorded more than 210 catastrophic events. Flooding was the most frequent hazard. For example, with a rise of more than 2m above its normal level, the Lake Tanganyika flooding in April 2021 has induced the displacement of many people and the abandonment of many houses and recreation centers. Flash flooding and gullying have been reported mostly at the foot of the hillslopes. The collapse of river banks has also caused severe damages to infrastructures, along the major rivers crossing the city.

Like many African cities, Bujumbura is characterized by the non-compliance with the law, an inefficient drainage system, the anthropization of the hillslopes overlooking the city, the increasing demand for housing and a lack of structure in its urban expansion. The older neighborhoods of central Bujumbura seem adapted to cope with these types of events, while the peri-urban areas are not. The combination of these vulnerability factors makes Bujumbura more exposed to disasters of hydrological origin.