bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison Between Surface Melt Days Estimation from a Regional Climate Model and Near-Daily Synthetic Aperture Radar Backscattering
Authors: Glaude Quentin , Kittel Christoph
Published: March 2020

 

Remote sensing has long been used as a powerful tool for the observation in cryospheric sciences. With the advances brought by the ESA Copernicus program, Earth observation goes a step further in its ability to get acquisitions at very high temporal rate. This is even amplified in polar regions due to heliosynchronism of satellites’ orbits. Earth observation shifts from sporadic observations to Earth monitoring.

Observations are a critical aspect for the assessment of geophysical models. The ability of a model to replicate observations is crucial as a benchmark. It also allows to refine our comprehension of Earth systems, such as in cryospheric sciences.

In this work, we are using the regional climate model MAR to compute the surface melt on a domain focusing on the Roi Baudouin Ice Shelf, Queen Maud Land, East Antarctica. From the results, we extract the number of days with surface melt in a region. In parallel, we employ remote sensing to obtain comparison data. Synthetic aperture radar appears as a solution of choice thanks to its day-and-night (critical in polar regions) and atmospheric-free capabilities. Radar backscattering anomalies between different dates are witnesses of substantial increase of soil moisture. Using Sentinel-1 in its wide-swath modes (namely Interferometric Wide Swath and Extra Wide Swath modes) and multiple satellite paths, near-daily acquisitions can be obtained. By comparing the two independent results, we better constraint model’s outputs while also better interpret SAR acquisitions. 
On sensitivity of natural vegetation and rainfed crops to soil texture
Authors: Gupta Surya , Lehmann Peter , Bonetti Sara , Or Dani
Published: March 2020

Crop sensitivity to soil texture guides many agronomic operations, especially under water-limited conditions. Unlike annual and mono-cultured crops, natural vegetation is subject to continuous selection of species and traits for adaptation to local climatic conditions. We report here a systematic evaluation of natural and rainfed cropped vegetation sensitivity to soil texture across biomes, rainfall anomalies, and scales using field observations and remote sensing products. Across biomes and annual precipitation amounts, natural vegetation productivity (GPP) shows no variations with soil texture. In contrast, crops (yields at small scales and GPP at large scales) exhibit sensitivity to soil texture that varies with annual rainfall anomaly and scale. Local measurements at field scale unambiguously show correlation in dry years (in agreement with conventional agronomic practices), while the strong correlation with soil texture vanishes at large scales (250 x 250 km) using remote sensing products. Subsampling of crop GPP at smaller scale (25 x 25 km) reveals a sensitivity of crop GPP to soil texture that becomes prominent in dry years. We conclude that natural vegetation across biomes represents a condition of climatic equilibrium via trait adaptation to overcome soil texture limitations, whereas annual crops retain dependency on soil texture (in rainfed agriculture) manifested at small scales, but obscured at larger scales where topography, aspect and soil map uncertainty dominate. The study provides new insights into gauging vegetation climatic adaptation via sensitivity to soil texture and the roles of scale in expressing such sensitivities in Earth Surface Models.
Effect of plastic mulching on the accumulation and distribution of macro and micro plastic particles in the soil - A case study of two farming systems in North West China
Authors: Meng Fanrong
Published: March 2020

Plastic mulching is a common farming practice in arid and semi-arid regions. Inappropriate disposal of plastic films can lead to the contamination of macroplastics (MaPs) and microplastics (MiPs) in the soil. To study the effects of plastic mulching on the contamination of soil with MaPs and MiPs and the role of farm management on this contamination, research was done on two farming systems in Northwest China, where plastic mulching is intensively used. Farming in Wutong Village (S1) is characterized by small plots and low-intensity machinery tillage while farming in Shihezi (S2) is characterized by large plots and high-intensity machinery tillage. Soils were sampled to a depth of 30 cm and analysed. The results showed that MaPs ranged from 30.3 kg·ha-1 to 82.3 kg·ha-1 in S1 and from 43.5 kg·ha-1 to 148 kg·ha-1 in S2. The main macroplastics  size categories were 2-10 cm2 and 10-50 cm2 in S1 and  < 2 cm2 and 2-10 cm2 in S2. In S1, we found that 6-8 years of continuous mulching practice resulted in the accumulation of more MaPs as compared to the use of intermittent mulching over the span of 30 years. For S2,  6 to 15 years of plastic mulching use led to MaPs accumulation in fields but from 15 to18 years, the MaPs number and content in soils dropped due to further fragmentation of the plastic and its dispersal into the environment. MiPs were mainly detected in fields with > 30 years of mulching use in S1 and discovered in all fields in S2, this indicated that  long-term cultivation and high-intensity machinery tillage could lead to more severe microplastic pollution. These results emphasized the impacts of  farm management on the accumulation and spread of MaPs and MiPs in the soil and regulations are needed to prevent further contamination of the soil.
Relief rejuvenation in response to intraplate neotectonics in the Betics foreland (southern Spain)
Authors: Expósito Inmaculada , Jiménez-Bonilla Alejandro , Yanes José Luís , Balanyá Juan Carlos , Moral Francisco
Published: March 2020
Tree crown economics: testing and scaling a functional-trait based theory
Authors: McNeil Brenden
Published: March 2020

The relationship of tree form and function has long fascinated humans, and now, much of our ability to improve maps and forecasts of the vital interactions of forests and global change hinges on our ability to understand this adaptive tree crown architecture.  To help address this challenge, I revisit Henry Horn’s classic 1971 monograph “The Adaptive Geometry of Trees”, and blend his theoretical framework with a contemporary ecological theory of species’ functional traits.  Then, I describe how this trait-based theory tree crown architecture can be robustly tested using state-of-the-art hyper-remote sensing techniques.  This suite of imaging techniques from hyper-spatial (e.g. UAV and satellite imagery), hyper-spectral (e.g. AVIRIS imagery), hyper-temporal (e.g. phenocams and tree- or tower-mounted time-lapse cameras), and hyper-dimensional (terrestrial and UAV LiDAR) sensors now enables us to visualize and measure the spectral and architectural properties of individual trees with unprecedented accuracy and precision.  Through analysis of hyper-remote sensing datasets collected in forests across eastern North America, I highlight how this testable trait-based theory of tree crown economics is already providing fresh insights into several important, but heretofore unresolved patterns of spatial and temporal variability in forest functioning.    
Observations and Simulations of Reconnecting Current Sheets in the Solar Corona
Authors: Antiochos Spiro , Kumar Pankaj , Jarpen Judy , Dahlin Joel
Published: March 2020

Jets and mass ejections are ubiquitous features of the Sun’s corona. These explosive dynamics are all believed to be driven by magnetic reconnection at two types of current sheets that form in the solar atmosphere: those that form at magnetic null points and separatrix surfaces, and those, such as the heliospheric current sheet, that form as a result of a large expansion of a bipolar magnetic field. In our breakout model, both types of current sheets are essential for the explosive release of magnetic energy. We report on the first direct observations of reconnection and island formation in a null-point current sheet associated with a large coronal jet. The topology and velocities of the islands are in excellent agreement with our numerical simulations of coronal jets. We discuss the implications of the observations and our models for understanding the energetic particles produced by these events and their release into interplanetary space, as well as the implications for observations by Solar Orbiter and the Parker Solar Probe.

This work was supported by the NASA Living With a Star Program.

 
Tundra Energy Fluxes under Drought and Extreme Summer Rainfall Scenarios
Authors: Grysko Raleigh , Plekhanova Elena , Oehri Jacqueline , Schaepman-Strub Gabriela
Published: March 2020

The Arctic is undergoing amplified climate change and forecasts predict increased warming and precipitation in the future. How changes in temperature and precipitation affect the partitioning of the Arctic land surface energy budget is not clear, despite the importance of both the Arctic region and the surface energy budget in earth system processes at local, regional, and global scales.

We will investigate the Arctic tundra energy budget and the relative importance of biotic and abiotic drivers. Specifically, we are experimentally testing effects of changing summer precipitation on the partitioning of the surface energy budget by simulating precipitation-based climate extremes – extreme drought and extreme precipitation totals.

We will present a literature-based synthesis of the expected impact of drought and extreme rainfall on the energy budget components of the tundra land surface and a description of the experimental design and treatments. The experiment has been established at a long-term Siberian tundra test site (71°N, 147°E). Extreme drought (precipitation) is being simulated by removing (adding) a predetermined fraction of ambient precipitation from (to) the test plots. Control plots, where ambient precipitation is not modified, are used as a baseline. Plot selection, soil sampling, and installation of below-ground sensors were performed during the past two summers, while setup of shelters and water-addition installations were completed early July 2019.

With our results on energy budget behavior change under future summer precipitation scenarios, we expect to inform mechanistic and statistic modeling of species distributions, ecosystem functions, and climate feedback in the Arctic tundra.
Is it feasible to relate CO2 atmospheric measurements with land use and cover change data? -A primary assessment of land use and cover change datasets in the Amazon
Authors: Tejada Graciela , Gatti Luciana , Basso Luana , Marani Luciano , Cassol Henrique , Arai Egidio , Aragão Luiz , Crispim Stephane , Neves Raiane , Domingues Lucas , Correia Caio , Ipia Alber , Gloor Manuel , Miller John , von Randow Celso
Published: March 2020

Atmospheric CO2 concentrations have had a significant increase in recent years reaching levels never seen before. In the Amazon region, the main CO2 emissions come from land use and cover change (LUCC), especially for the deforestation of natural forests. It is very important to understand the impacts of climate change and deforestation on the Amazon forests to understand their role in the current carbon balance at different scales. The lower-troposphere greenhouse gas (GHG) monitoring program “CARBAM project”, has been collecting bimonthly GHGs vertical profiles in four sites of the Amazon since 2010, filling a very important gap in regional GHGs measurements. Here we compare different LUCC datasets for the Amazon region to see if there is a relation between annual LUCC and bimonthly CO2 aircraft measurements in the Amazon. We compared the annual (2010-2018) LUCC area from IBGE, PRODES and mapbiomas pan-amazon datasets for each mean influence area of the CARBAM sites and relate this LUCC areas with the annual CO2 fluxes. We found differences in the classification methods of the LUCC data, showing differences in the total deforested area. The LUCC data have different tendencies in each CARBAM influence area having more deforestation in the east side of the Amazon CARBAM sites. There is no clear trend between LUCC and carbon fluxes in the last 8 years. Inter-annual CO2 fluxes variability could be related with the several droughts that influence the photosynthesis/respiration. Here we highlight the scale issues regarding LUCC datasets, atmospheric CO2 measurements and CO2 modeling to better understand the current Amazon carbon balance.  

Acknowledgment: FAPESP (2018/18493-7; 2018/14006-4; 2016/2016/02018-2), NASA, ERC (GEOCARBON, Horizon 2020/ASICA), NERC (NE/F005806/1), CNPq (480713/2013-8).

 
New insight into the December 2018 Etna eruption through the joint inversion of ground deformation and gravity data
Authors: Chauhan Mahak Singh , Cannavò Flavio , Carbone Daniele , Greco Filippo
Published: March 2020

We focus on the eruption of Mt. Etna which took place on 24 December, 2018. The eruption occurred after a month of unrest and was accompanied by a seismic swarm that culminated in the M4.9 earthquake on the 26th, with epicentre on the eastern flank of the volcano. We jointly analyse ground deformation and gravity data to estimate the geometrical and kinematic parameters of the source structure, together with the density of the intruding material. The data used in this study were recorded by stations in the INGV-OE monitoring network (21 GPS stations and 2 gravity stations equipped with superconducting gravimeters), during the interval of 23 to 28 December (pre to post eruption). We assume a dike-type source for the forward calculation in the defined objective function. A pattern search algorithm (PSA) is used for the iterative minimization of the misfit error. In order to estimate the posterior probability density function (PDFs) of the model parameters, we also use a Markov Chain Monte Carlo (MCMC) approach. Indeed, the calculated PDFs provide more information about the uncertainties of the model parameters, which helps to understand overall tendencies of the solutions. We first test the constrained inversion of the gravity data, to calculate the density of eruptive magmatic body, by fixing the geometrical parameters of the dike, previously retrieved through inversion of the deformation data only. Using this approach, it is possible to suitable explain the deformation data and the gravity change observed at the station in the near field (MNT), while the gravity change at the other station (SLN) remain unexplained. We then invert jointly both deformation and gravity datasets, in order to adequately fit all the observations. The final model gives a density value of ~1.8-2.0 g/cm3. This value is significantly lower than the density of bubble-free magma and indicates either the involvement of gas in the intrusive process, or the formation of dry fissures during the emplacement of the dyke.
Emplacement mechanism of Late Triassic granitic Dushan pluton, North China and its tectonic implications
Authors: Qiu Huabiao , Lin Wei , Chen Yan , Faure Michel
Published: March 2020

To better understand the Late Triassic tectonic setting in the northern North China Craton (NCC), a multidisciplinary investigation, including structural geology, geochronology, anisotropy of magnetic susceptibility (AMS) and gravity modeling, has been carried out in the Dushan pluton. The Dushan pluton consists of monzogranite and biotite-rich facies along the pluton margin without sharp contact between them. The granite varies southwestwards from isotropic texture to arcuate gneissic structures, with locally mylonitic structures. The intensity of solid-state deformation increases southwestwards across the pluton, leaving preserved magmatic fabrics in the northeastern part. The compatible outward dipping magmatic and solid-state magnetic fabrics, together with mesoscopic fabrics, define an elliptic dome-like pattern with a NE-SW oriented long axis, despite the fabrics dip inwards in the southeastern margin of the pluton. Combining gravity modeling, the Dushan pluton presents an overall tabular or tongue-like shape with a northeastern root. The magnetic lineations nearly strike NE-SW, concordant with the stretching lineations observed in the mylonitic zones. We propose the emplacement mode that the Dushan pluton emplaced southwards through the feeder zone in its northeast, beginning probably with a sill. The later successive magma batches may laterally and upwardly inflate, deform and even recrystallize the former cool-down magma. This inflation forms an arcuate, gneissic to mylonitic foliation in the southwestern margin. The Dushan pluton is considered as typically post-tectonic in emplacement, recording a Late Triassic post-tectonic setting of the northern NCC.
Lake level changes in the Dead Sea during the late Pleistocene recorded by fossil lake shorelines
Authors: Jara-Muñoz Julius , Agnon Amotz , Fohlmeister Jens , Mey Jürgen , Frank Norbert , Plessen Birgit , Schroeder-Ritzrau Andrea , Garcin Yannick , Darvasi Yaniv , Melnick Daniel , Strecker Manfred
Published: March 2020

High-resolution records of lake-level changes are crucial to elucidate the impact of local and global climatic changes in lacustrine basins. The Late Quaternary evolution of the Dead Sea has been characterized by substantial variability apparently linked with global climatic changes, beign subject of many research efforts since decades. Previous studies have defined two main lake phases, the Lake Lisan and the Dead Sea, the earlier was a highstand period that lasted between ~70 and ~15 ka, the  latter was the lowstand period that persisted until the present. Here we focus on the switch between Lake Lisan and Dead Sea studying fossil lake shorelines, a sequence that comprises dozens of levels exposed along the rims of the Dead Sea, containing abundant fossil stromatolites that we dated by mean of radiocarbon and U-decay series. We determined 90 radiocarbon and 35 U-Th ages from stromatolites from almost every shoreline level. We compared U-Th and radiocarbon ages to estimating a radiocarbon reservoir between 0.2 and 0.8 ka, used to correct the remaining radiocarbon ages before calibration. The resulting ages range between ~45  and ~20 ka. Dating was complemented with analysis of stable oxygen and carbon isotopes. Furthermore, we applied a distributed hydrological balance model to constrain past precipitation and temperature conditions. Our results suggest that the duration of the last Lake Lisan highstand was shorter than previously estimated. Taking this at face value, the switch between Lake Lisan and Dead Sea occurred at ~28 ka, ~10 ka earlier than previously suggested. Oxygen and carbon isotopes show a consistent pattern, displaying a switch between wet and dry conditions at ~28 ka. Preliminary results from the hydrological model indicate a much stronger sensitivity of the lake level to precipitation amounts than to air temperature. From our results we can’t observe a clear link between global temperature variations and lake-level changes in the Lisan/Dead Sea lakes. Similar non-linear response to northern hemisphere climatic changes have been also documented in Holocene Dead Sea paleoclimatic records, suggesting that global climatic variations may led to variable lake-level responses. The results of this study adds further complexity to the understanding of factors controlling climate variability in the Dead Sea.
Modeling fluid flow through complex fracture network in geological media by using hierarchical hydraulic properties
Authors: Chang Kyung Won , Beskardes Gungor , Weiss Chester
Published: March 2020

Hydraulic stimulation is the process of initiating fractures in a target reservoir for subsurface energy resource management with applications in unconventional oil/gas and enhanced geothermal systems. The fracture characteristics (i.e., number, size and orientation with respect to the wellbore) determines the modified permeability field of the host rock and thus, numerical simulations of flow in fractured media are essential for estimating the anticipated change in reservoir productivity. However, numerical modeling of fluid flow in highly fractured media is challenging due to the explosive computational cost imposed by the explicit discretization of fractures at multiple length scales. A common strategy for mitigating this extreme cost is to crudely simplify the geometry of fracture network, thereby neglecting the important contributions made by all elements of the complex fracture system.

The proposed “Hierarchical Finite Element Method” (Hi-FEM; Weiss, Geophysics, 2017) reduces the comparatively insignificant dimensions of planar- and curvilinear-like features by translating them into integrated hydraulic conductivities, thus enabling cost-effective simulations with requisite solutions at material discontinuities without defining ad-hoc, heuristic, or empirically-estimated boundary conditions between fractures and the surrounding formation. By representing geometrical and geostatistical features of a given fracture network through the Hi-FEM computational framework, geometrically- and geomechanically-dependent fluid flow properly can now be modeled economically both within fractures as well as the surrounding medium, with a natural “physics-informed” coupling between the two.

SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525.
Using glaciers to identify, monitor, and predict volcanic activity
Authors: Martin Michael , Barr Iestyn , Edwards Benjamin , Symeonakis Elias , Spagnolo Matteo
Published: March 2020

Many (about 250) volcanoes worldwide are occupied by glaciers. This can be problematic for volcano monitoring because glacier ice potentially masks evidence of volcanic activity. Both the deadliest and most costly volcanic eruptions of the last 100 years involved volcano-glacier interactions. The 1985 eruption of Nevado del Ruiz killed 23000 people, and the 2010 eruption of Eyjafjallajökull led to the closure of many European airports. Therefore, improving methods for monitoring glacier-clad volcanoes is of clear societal benefit. Amongst several methods, satellite based remote sensing techniques are perhaps most promising, since they frequently have a relatively high temporal and spatial resolution, and are mostly freely available. They can help to identify the effects of volcanic activity on glaciers, including ice fracturing, ice surface subsidence and glacier acceleration potentially due to subglacial melt or subglacial dome growth. This study aims to link pre-, syn- and post-eruption glacier behavior to the type and timing of volcanic activity, and to develop a satellite based predictive tool for monitoring future eruptions. Despite several studies that link volcanic activity and changing glacier behavior, the potential of using the latter to predict the former has yet to be systematically tested. Our approach is to use satellite imagery to observe how glaciers responded to past volcanic events, and to build a training database of examples for automated detection and forecasting.
Low-cost river discharge measurements using a transparent velocity-head rod
Authors: Despax Aurélien , Le Coz Jérôme , Pernot Francis , Buffet Alexis , Berni Céline
Published: March 2020

The common streamgauging methods (ADCP, current-meter or tracer dilution) generally require expensive equipment, with the notable exception of volumetric gaugings and floats, which are however often difficult to implement and limited to specific conditions. The following work aims at testing and validating a reliable, easy-to-deploy and low-cost gauging method, at a cost typically below 40 € each.

The “velocity-head rod” firstly described by Wilm and Storey (1944), made transparent by Fonstad et al. (2005) and improved by Pike et al. (2016) meets these objectives, for wading gauging with velocities greater than 20 cm/s typically. The 9.85 cm wide clear plastic rod is placed vertically across the stream to identify upstream and downstream water levels using adjustable rulers. The difference in level (or velocity head) makes it possible to calculate the average velocity over the vertical, using a semi-empirical calibration relationship.

Experiments carried out in INRAE’s hydraulic laboratory and in the field have enabled us to find a calibration relationship similar to that proposed by Pike et al. (2016) and confirm the optimal conditions of use. The average deviation to a reference discharge has been found to be close to 5 % except for very slow-flow conditions. The influence of the width of the rod on the velocity-head was studied in the laboratory. The uncertainty of the velocity due to the reading of water levels has been estimated. It increases at low velocity due to decreasing sensitivity, and increases at high velocities due to water level fluctuations that are difficult to average.

Several improvements were tested in order to facilitate and improve the measurement operations, without increasing the cost too much: magnetic ruler, removal of a graduated steel rule (expensive), plastic ruler with water level and velocity graduations, reading the depth with another ruler, spirit level, electrical contact (so the operator has not to bend to the surface of the water). An operational procedure and a spreadsheet for computing discharge are proposed. The method being extremely simple and quick to apply is well suited for rapid estimates of flow (instead of floats), training or demonstrations, citizen science programs or cooperation with services with limited resources.

Acknowledgments: The authors thank Q. Morice, J. Cousseau, Y. Longefay (DREAL) who were involved in this study by carrying out field tests.
Extreme precipitation events in the Mediterranean area. A contrasting Lagrangian and Eulerian approach for moisture evaporation sources identification.
Authors: Cloux González Sara , Garaboa Paz A. Daniel , Insua Costa Damian , Perez Muñuzuri Vicente , Miguez Macho Gonzálo
Published: March 2020

Concern about heavy precipitation events has increasingly grown in the last years in the South of Europe, especially in the Mediterranean region. These occasional episodes can result in more than 200 mm of rainfall in less than 24 h, producing flash floods with very high social and economic losses.  

To improve their predictability, the correct identification of the origin of the moisture must be done. The Eulerian and Lagrangian models provide a good approach to detect moisture sources. However, they show some limitations. 

Here, we present a comparison between both methods through a case study of an extreme precipitation event on the region of the Mediterranean coast which take place in 1982. Using the Lagrangian model FLEXPART-WRF to backtrack the moisture, we identify the evaporation sources. Then, we compare it with the results obtained through Eulerian WRF-WVT method [1]. Also, we evaluate the accuracy of E-P balance in contrast to Evaporation patterns. Finally, we implemented a further identification of moisture uptake method which enables us to directly compare results from both strategies [2]. 

 

[1] Insua-Costa, D., Miguez-Macho, G., and Llasat, M. C.: Local and remote moisture sources for extreme precipitation: a study of the two catastrophic 1982 western Mediterranean episodes, Hydrol. Earth Syst. Sci., 23, 3885–3900, https://doi.org/10.5194/hess-23-3885-2019, 2019. 

[2] Sodemann, Harald, C. Schwierz, and Heini Wernli.: Interannual variability of Greenland winter precipitation sources: Lagrangian moisture diagnostic and North Atlantic Oscillation influence. Journal of Geophysical Research: Atmospheres 113.D3 (2008). 
Image-by-image calibration of thermal infrared data
Authors: Heim Rene , Guo Xiaolei , Zare Alina , Rowland Diane
Published: March 2020

Surface temperature retrieval through thermal infrared imaging (TIR) is currently being applied in a multitude of natural science disciplines (e.g. agriculture and ecology). Enormous progress in sensor design, electronics, and computer science render TIR systems as easily applicable and accessible for research, industry and even private use. However, despite the existence of factory-set theoretical calibration models that are supposed to facilitate accurate conversion of digital pixel values into temperature values, complex environmental noise and handling parameters hamper the reliable and stable collection of temperature data. Here, we present an image-by-image calibration method that can potentially account for such environmental noise.

We used custom-built thermal calibration panels, a close-range thermal camera and a thermocouple to collect thermal images and ground truth temperatures of peanut plants (Arachis hypogaea L.) in an open and sheltered agricultural setting. Linear models were trained and tested to investigate whether an image-by-image calibration approach improves the accuracy of digital value to temperature conversion over calibrating once before an experiment, as well as before and after an experiment. For both, the sheltered and open setting, we collected data on multiple days.

Our data indicate that there are marked differences in calibration model stability and accuracy between the open and sheltered setting. For the open setting the image-by-image calibration resulted in lower mean absolute temperature errors (MAE = 0.9°C) compared to the sheltered setting (MAE = 4.37°C). We also found that the intercept and slope of the image-by-image calibration models varied substantially under open conditions. Between two images, both captured less than two minutes apart, the digital number to temperature conversion (intercept) could vary by up to 15°C. By contrast, the intercepts derived from the sheltered scenario rarely varied by more than 5 °C.

Our results show that an image-by-image calibration can be preferable to obtain reliable and accurate temperature data. Such data can be crucial to monitor and detect abiotic and biotic stress in animal and plant food production systems where differences in temperature can be very subtle. A reduction of stressors in such systems is often coupled with an increase in yield. At the EGU 2020, we would like to share our research, and some extensions of it, to receive constructive feedback to drive future research on how to reliably and accurately collect sensitive surface temperatures in industry and research.
Hydraulic fracturing operations within an extremely complex stress regime: The case of Fort St. John, British Columbia, Canada
Authors: Salvage Rebecca O. , Eaton David W.
Published: March 2020

On 30 November 2018, three felt earthquakes occurred in quick succession close to the city of Fort St. John, British Columbia, likely as a direct response to a hydraulic fracturing operation in the area. Events appear tightly clustered spatially within the upper 10 km of the crust. Hypocenters locate at the confluence between a large scale reverse faulting regime (in the north-west, probably due to the influence of the Rocky Mountain fold and thrust belt) and an oblique strike slip faulting regime (in the south-east, probably due to the influence of the Fort St. John Graben), resulting in a variety of focal mechanisms and a very complex local stress regime. Further analysis of the principal stresses suggests that σ1 is well constrained and close to horizontal, whereas σ2 and σ3 are poorly constrained, and can alternate between the horizontal and the vertical plane. Here, we present an overview of the temporal and spatial evolution of this seismic sequence and its relationship to hydraulic fracturing operations in the area, and examine the influence of large-scale regional tectonic structures on the generation of seismicity on this occasion.

 
Daily rainfall above 75mm is a major trigger to landslides in the Muhunguzi, western Burundi
Authors: Kankurize Clairia , Rufyikiri Gervais , Delvaux Bruno
Published: March 2020

Located in the East African Rift Valley, western Burundi is often threatened by landslides during the rainy season. Damage can be seen both in the mountains, the sites of the landslides, and in the plain where sediments are deposited: environmental degradation, loss upstream and downstream of cultivated land, destruction of infrastructures, loss of life, waterborne diseases, floods of streams laden with sludge and stones torn off during landslides... The magnitude of these shifts justifies the need for studies to understand the factors that cause this part of Burundi to be vulnerable to landslides.

Here we highlight the relationship between the environmental context and the process of landslides in this region. To analyze the impact of geomorphological, geological, soil and climatic conditions as well as anthropogenic factors, we carried out an inventory of landslides in the Muhunguzi watershed, a survey of the local population and an analysis of rainfall over the period 1935-2014.

Of 7 Muhunguzi sub-watersheds with a total area of 21.2 km2, 43 landslides were identified, 29 of which were on a single sub-watershed. Most landslides were shallow. Geomorphology was characterized by steep escarpments interspersed with valleys. The landslides were located on the lower slopes and most affected the rivers. The lithology was dominated by shale inclined parallel to the slope. Landslides were located on rocky, black or red soils, identified as Nitisols. The majority of landslides occurred on cultivated fields. Daily precipitations ranging between 75mm and 100mm with a return period of 5.3 years are strongly correlated to shallow landslides in the studied area. Such intense daily rain thus appears here as a major trigger to these landslides. In addition, relief, geological and soil conditions are predisposing factors while population density and the resulting land pressure worsen land instability.

We conclude that further studies are needed to understand the impact of soil processes and human activity in order to identify adequate management practices preventing landslides in Muhunguzi area.
Reservoir Response to Heat Generating Nuclear Waste Disposal in Bedded Salt
Authors: Jayne Richard , Kuhlman Kristopher
Published: March 2020

 The disposal of heat generating nuclear waste is increasingly becoming a concern for several countries worldwide. This issue is of particular concern for the United States because of the 364,000 m3 of heat-generating nuclear waste currently in temporary storage. Numerous concepts for the disposal of heat generating nuclear waste have been investigated internationally, such as, mined repositories in crystalline, argillite, and salt formations, and deep borehole disposal. Currently, salt formations are being investigated as candidate disposal host rocks for heat-generating nuclear waste in the United States, Germany, the Netherlands, and the United Kingdom. Salt formations may be an ideal host media due to salt’s extremely low permeability, high thermal conductivity, and self-healing capability. Salt lacks circulating groundwater, but it is not dry. Brine availability in salt has multiple implications for the safety and design of a nuclear waste storage facility. Brine transport is a potential off-site radionuclide transport vector, brine leads to corrosion of metallic and glass waste forms and waste packages, chloride in brine can reduce criticality concerns, and accumulated brine can provide back-pressure that resists long-term creep closure of porosity associated with mining the repository. In order to improve understanding of brine migration in heated salt, borehole heater experiments are being conducted at the Waste Isolation Pilot Plant (WIPP) in Carlsbad, New Mexico. The salt heater test collaboration aims to collect data to gain a better understanding of brine availability, transport, and thermal evolution of salt in response to heating up to 140 °C. Due to the complex nature and coupled processes that take place within bedded salt, this study will utilize 1D, 2D, and 3D numerical simulations of the salt heater test to deconvolve the parametric controls on brine availability and migration. The purpose of this study is two-fold, in addition to understanding the hydrogeology of salt formations, we utilize two different subsurface flow codes in a code comparison study, TOUGH and PFLOTRAN. Preliminary results from this study illustrate the importance of understanding the host rock properties and the initial/boundary conditions of the salt and multiphase fluid flow near the excavation site.

 

Sandia National Laboratories is a multimission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.
High pressure serpentinization and abiotic methanogenesis in metaperidotite from the Appalachian subduction, northern Vermont
Authors: Boutier Antoine , Vitale Brovarone Alberto , Martinez Isabelle , Sissmann Olivier , Mana Sara
Published: March 2020

Serpentinization is the process of hydroxylation of olivine-rich ultramafic rocks to produce minerals such as serpentine, brucite, magnetite, and may release H2. The hydrogen produced through serpentinization reactions can be involved in abiotic reaction pathways leading to the genesis of abiotic light hydrocarbons such as methane (CH4). Examples of this phenomenon exist at the seafloor, such as at the serpentinite-hosted Lost City hydrothermal field, and on land in ophiolites at relatively shallow depths. However, the possibility for serpentinization to occur at greater depths, especially in subduction zones, raises new questions on the genesis of abiotic hydrocarbons at convergent margin and its impact on the deep carbon cycle. High-pressure ultramafic bodies exhumed in metamorphic belts can provide insights on the mechanisms of high-pressure serpentinization in subduction zones and on the chemistry of the resulting fluids. This study focuses on the ultramafic Belvidere Mountain complex belonging to the Appalachian belt of northern Vermont, USA. Microstructures show overgrowth of olivine by delicate antigorite crystals, suggesting olivine serpentinization at high-temperature consistent with the subduction evolution of the Belvidere Mountain complex.  Fluid inclusion trails cross-cutting the primary olivine relicts  suggest their formation during the antigorite serpentinization event. MicroRaman spectroscopy on the fluid inclusions reveals a CH4-rich gaseous composition, with trace of N2, NH3 and S-H compound. Moreover, the precipitation of daughter minerals of lizardite and brucite in the fluid inclusions indicate the initial presence of H2O in the fluid. Secondary olivine is observed at the rim of pseudomorphosed primary pyroxenes (bastite), and has higher forsterite (Fo95) content with respect to the primary olivine (Fo92), suggesting either a syn-serpentinization olivine precipitation in the subduction zone, or a successive partial dehydration of the antigorite during metamorphism. Decreasing oxygen fugacity during serpentinization and related abiotic reduction of carbon at high-pressure conditions is proposed at the origin of methane in the fluid inclusions. This potentially places the Belvidere Mountain complex as an example of deep serpentinization related to high-pressure genesis of abiotic methane.
Oxidative Potential of PM2.5 in Dammam, Saudi Arabia, and the effect of dust storms.
Authors: Alwadei Manna , Thomson Steven , Kramer Louisa , Shi Zongbo , Bloss William
Published: March 2020

The ability of particulate matter (PM) to generate reactive oxygen species and induce oxidative stress in human body is known as oxidative potential (OP). OP is considered an important indicator of the toxicity of PM, which is associated with adverse health impacts. Linking the predicted health impacts of aerosols to OP may be more relevant than considering PM mass only. In this study, we determined the OP of PM2.5 (PM with aerodynamic diameter less than 2.5 µm) in Dammam, Saudi Arabia, in order to understand the relationship of OP to PM mass and composition in the present and absent of dust storm.
PM2.5 was collected from two locations in Dammam city in the winter and summer of 2018. The first location was the city centre as an urban area while the second one was in the campus of Imam Abdulrahman Bin Faisal University as an urban background area. OP was quantified using dithiothreitol (DTT) assay. The mean PM2.5 mass in the summer (120.5 µg/m3) was nearly  twice that in the winter (62.6 µg/m3). The average OP activity per air volume (DDTv) in the winter was 1.14 nmol min-1 m-3 while in the summer it was 1.77 nmol min-1 m-3. Conversely, the mean OP activity per PM mass (DDTm) in the winter was 24.56 pmol min-1 µg-3 while it was lower in the summer at 17.3 pmol min-1 µg-3. Results showed an inverse correlation between PM mass and DDTm, while there was a positive correlation between PM mass and DDTv. Even though the average mass of PM2.5 in the summer was almost twice that in the winter, the average DDTm was lower in the summer compared to winter. This is due to the much lower oxidative potential in dust storm particles, which contribute significantly to the summertime PM2.5. Our results suggest that OP is driven by PM composition rather than mass. 

 
Seismo-volcanic source mechanism in White Island's hydrothermal system
Authors: Sindija Dinko , Neuberg Jurgen
Published: March 2020

The signals preceding and accompanying phreatic eruptions, although observed on many volcanoes, are still not very well understood. As this type of eruption can have severe consequences, we need to understand the processes and the observed seismic signals leading up to these eruptions. Using seismic broadband instruments, we can detect signals in a wide frequency range, and careful analysis and modelling of these data can help us understand these processes. Phreatic eruptions are often accompanied, and sometimes preceded, by Very Long Period (VLP) seismic signals. These signals are caused by sudden pressure changes inside the volcanic system and in hydrothermal environments these pressure changes and, therefore, observed VLPs are attributed to the sudden expansion of water-filled cracks by vapourisation due to heat flow from the underlying magma body. 
However previous studies consider pure water-water systems which sometimes assume unrealistic pressure-temperature changes in the system to produce a violent phase change from water to vapour. As there are instances of significant amounts of CO2 measured within hydrothermal systems, we model how a sudden injection of CO2 into the hydrothermal system, which would easily allow for explosive phase change could trigger the observed VLPs. Further, we show how poroelastic medium responds to such a source.
Relic charcoal hearth geomorphology and hydrology across the northcentral Appalachians, USA
Authors: Bayuzick Samuel , Drohan Patrick , Raab Thomas , Hirsch Florian
Published: March 2020

Throughout the northeastern United States and Europe, relic charcoal hearths (RCHs) are more regularly being discovered in proximity to furnaces used for iron or quick-lime production; charcoal was used as a primary fuel source in the furnaces.  RCHs have been found across parts of Europe and Connecticut, USA in different hillslope positions, on vary degrees of slope and aspect, all of which can be a factor affecting the shape of the RCH.  Their usage for charcoal production varied with time period furnaces were in operation with some hearths being used once and older ones (such as in Europe) being used multiple times. RCHs across the northcentral Appalachians, USA have been minimally investigated, thus determining where they occur on the landscape, their shape, and their morphologic positions will be useful in discerning their effect on surface hydrology and soil development. Our study focuses on developing a repeatable process for: finding RCHs, classifying the different shapes or styles of the hearths in relation to their geomorphic positions and quantifying how RCHs may alter surface hydrology.  

We used a combination of processed LiDAR to create hillshades of varying light angles and altitude, and slope gradient maps derived from the same LiDAR, to visually digitize > 6,100 hearths. A subset of the mapped hearths was ground-truthed for accuracy of the methodology. For our study, three areas in the mid-Appalachian region of Pennsylvania were chosen for study in order to reflect different historical time periods of construction and environments. A goal of our study is to determine the age of hearths. We hypothesize that using a calculated 3D distance to nearby furnaces, hearths closer to furnaces will be the oldest and have a higher likelihood of being used multiple times resulting in multiple layers of charcoal-enriched substrate. An initial analysis of RCHs indicates a relationship between slope gradient and hearth shape. Hearths constructed on flatter slope gradients are seemingly more circular in shape and have more equal axes whereas steep slopes have a more oval shape being elongated in one axis and shortened on the other.  Likewise, there may be a relationship between hillslope position and the shape of the RCHs such as more circular hearths are on or near flatter hillslope positions (such as on summits or shoulders) whereas oval shaped hearths are on steeper hillslope positions (like backslopes). We also modeled the effect of RCHs on hydrology.  Based on a combination of topographic wetness index data and geomorphology, hearths are not acting as sinks for surface flow but instead often cause water to flow around them leading to slightly drier conditions within RCHs. Future work will address site-specific monitoring of hearth temperature and moisture, and hearth carbon decomposition dynamics in relation to temp and moisture conditions.
Geomorphological properties of the island of Hvar beaches (Croatia, Eastern Adriatic Coast)
Authors: Mićunović Marin , Faivre Sanja
Published: March 2020

Beaches are sedimentary forms, situated at the land-sea contact formed of unconsolidated material which can range in size from sand up to cobbles and boulders. They are one of the most dynamic coastal forms and particularly sensitive to changes (natural and/or anthropogenic).

Geomorphological properties of the island of Hvar beaches were analyzed by means of field mapping, ortho-photo and GIS analysis. All the beaches have been mapped and measured at four different points in time by means of Ortho-photos from State Geodetic Administration (2011, 2014 and 2017) and HERE maps (2019). Larger beaches have been also measured in the field with a GPS receiver (from July 2018 until July 2019). GIS and statistical calculations and visualization were done in ArcGIS 10.4 software.

Hvar is the longest Croatian island with a length of 67,8 km, and the fourth in size with a surface of 297,4 km2. Along its 254 km long coastline 247 beaches have been mapped which make up 3,8 % of total coastal length. The beaches are rather small relating generally to pocket beaches. Only 14,7 % of beaches are larger than 500 m2 and 59,95 % are smaller than 200 m2. According to the sediment size gravely beaches predominate with 95,5 %, while only 4,5 % relates to sand beaches.

This study revealed that on the island of Hvar four major morphological types of beaches can be distinguished: beaches formed in fan material at the gully mouth (82,6 %), beaches under the cliff (9,3 %), beaches formed in Aeolian deposits (4,45 %) and artificial or anthropogenic beaches (2,4 %). 1,2 % are undefined. The majority of beaches, 75%, are today under anthropogenic impact while only 25% is completely natural.

Along the eastern Adriatic coast most of the beaches are formed in torrential material derived from the land accumulated at the gully mouth. Here we revealed that this is also the case on the Island of Hvar (82,6 %). Those beaches are parts of a larger geomorphological system which links the backward drainage basin with the beach. Consequently, here we test if the surface of the beaches correlates with the surface of the drainage basins. Taking into account all the beaches of that morphological type (204 beaches) the correlation revealed to be rather low (r2=0,37). However, taking into account only the beaches without any anthropogenic impacts the correlation becomes more significant (r2=0,64). This probably points to the disturbing effects of the anthropogenic activity on beaches sediment budget of the island of Hvar.

A part of this research was made with the support of the Croatian Science foundation (HRZZ-IP-2019-04-9445).