bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of VLF/LF transmitter signals during the minimum of solar activity in the year 2018
Authors: Boudjada Mohammed  Y. , Weingril Vanessa , Eichelberger Hans Ulrich , Biagi Pier Francesco , Zhang XueMin , Magnes Werner , Schwingenschuh Konrad , Rozhnoi Alexander , Galopeau Patrick H.M. , Ermini Anita , Lammer Helmut , Colella Roberto , Besser Bruno , Stachel Manfred
Published: March 2020

We report on VLF/LF transmitter signals observed in the year 2018 during the minimum of solar activity. Those signals were recorded in Graz (Austria) using INFREP (Biagi et al., Nat. Hazards Earth Syst. Sci., 11, 2011) and UltraMSK (Schwingenschuh et al., Nat. Hazards Earth Syst. Sci., 11, 2011) systems. This leads us to record fourteen transmitter signals in the frequency range between 19 kHz and up to 270 kHz. Six transmitter channels are common to both systems and are localized in Great-Britain (Anthorn, GBZ, 19.58kHz), Italy (Tavolara, ICV, 20.27kHz), Germany (Rhauderfehn, 23.4kHz,) and Island (Keflavik, NRK, 37.5kHz). Others are mainly LF broadcasting transmitters from Romania (Brasov, 153kHz), Luxembourg (Felsberg-Berus, 183kHz), Algeria (Berkaoui, 198kHz), Monte-Carlo (Roumoules, 216kHz) and Tchecki (Lualualei, 270kHz). In the year 2018, the solar activity decreased reaching its minimum in the end of 2019. We emphasize in this work on three aspects: (a) C-flares related to the solar activity, (b) Kp-index linked to the geomagnetic activity, and (c) seismic events in the southern part of Europe, i.e. Greece and Italy.  The dominant patterns observed on almost all transmitters are due to the solar flares. Geomagnetic activity is found to depend on the seasonal effect and mainly observed few weeks before and after the summer solstice in the northern hemisphere.  Few earthquakes occurred in the southern part of Europe, in Greece (6 events) and in Italy (2 events) with a magnitude of 5.5 Mw and depths less than 10 km. We discuss the disturbances of VLF/LF transmitter signals prior to EQs occurrences, and their links to external effects. Our results are compared to recent investigations of Zhang et al. (Radio Sci., 52, 2017) and Rozhnoi et al. (Ann. Geophys., 37, 2019) concerning, respectively, the spatial distribution of VLF transmitter signals recorded by Demeter satellite, and the solar X-flare effects on VLF/LF transmitter signals.
Modeling of mixed karstic and alluvial recharge area for the drainage capture in Radovna River valley, Julian Alps (NW Slovenia)
Authors: Brencic Mihael , Loboda Jernej , Germovšek Andrej , Greiner Carina , Jelovčan Mateja , Krušec Urša , Pajnkiher Andreja , Peulić Kristina , Rustja Damjan , Vidmar Ines
Published: March 2020

In the Radovna River valley (NW Slovenia) in fluvioglacial sediments with high permeability and high yield, drainage capture supplies drinking water to over 20,000 inhabitants and extensive tourist facilities in one of the most important Slovenian tourist centers of Bled in the Gorenjska region. Drainage is dug at a depth of 10.0 m to 5.5 m and is 235 m long. It runs parallel to the river at a distance of 30 to 60 m. The total drainage flow ranges from 0.40 to 0.60 m3/s.

The Radovna River valley is a deep glacial valley with karstic plateaus on both sides of the valley. On the plateaus, sinkholes and smaller karst poljes are developed. The thickness of the fluvioglacial sediment in the valley exceeds 140 m. The position of the recharge area is such that it includes water infiltrating through the fluvioglacial sediment from the river and water infiltrating from the karst aquifer through the fluvioglacial sediment. The ratio of drainage water originating from the karst area and the river changes throughout the hydrological season. The proportion of water from the karstic plateau is higher in the high-water condition, and in the low-water conditions, water from the river bed is almost entirely dominant.

The paper presents a numerical model of groundwater flow toward the drainage, modeling both the inflow from the river area and the inflow from the karstic aquifer. The modeling is performed using the MODFLOW numerical model in the FREEWAT modeling environment.
Rock water as a key resource for ecosystems with thin soils: Digging deep trees subsidize patches of surficial grasses
Authors: Montaldo Nicola , Corona Roberto , Sirigu Serena , Piroddi Luca , Curreli Matteo , Oren Ram
Published: March 2020

Mediterranean mountainous areas of shallow soil often display a mosaic of tree clumps surrounded by grass. During dry seasons, evapotranspiration (ET) cannot be met by soil moisture. However, the combined role and dynamics of water extracted from the underlying rock, and the competition between adjacent patches of trees and grass, has not been investigated. We quantified the role rock water plays in the seasonal dynamics of evapotranspiration, and its components, over a patchy landscape in the context of current and past seasonal climate changes, and land-cover change strategies. Soil water budget, using precipitation (P), ET, and soil moisture changes (ΔS; ~17 cm soil layer), suggests deep water uptake by roots of trees (fd; 0.8 – 0.9 mm/d), penetrating into the fractured basalt below clumps and the surrounding pasture, subsidized grass transpiration in spring through hydraulic redistribution. However, in summer trees used all the deep water absorbed (0.79 mm/d; fd > tree transpiration). A 15-year dataset shows that, with increasing seasonal drought-severity (potential ET/P) to >1.34, the vertical water flux through the bottom of the thin soil layer transitions from drainage to uptake in support of ET. A hypothetical grass-covered landscape, with no access to deep water, would require 0.68 – 0.85 mm/d more than is available from P and ΔS, forcing shortened growing season and/or lower leaf area. In summer, ET in such a landscape would be half that of the existing mosaic, with consequences to energy balance. The vegetation mosaic may represent trending equilibrium, as long-term decreasing winter precipitation and increasing spring potential evaporation suggest drying climate. Intervention policies to increase water yield by reducing tree cover will curtail grass access to rock moisture, while attempting to increase tree-related products by increasing forest cover will limit water availability per tree leaf area. Both changes may further reduce ecosystem stability.

 
Aggregate formation dynamics driven by 3D fluid flow in natural porous media
Authors: Ritschel Thomas , Totsche Kai
Published: March 2020

Fluid flow and reactive transport in natural porous media take place in a three-dimensional, hierarchically organized network of voids and pores in the size range of sub-micrometers inside small aggregates to several millimeters in, e.g., earthworm burrows or cracks. Thus, fluid flow regimes are manifold with consequences not only for the transport of solutes, but also for the displacement of colloidal particles and organic matter and thus, for their inclusion into soil aggregates. Therefore, we incorporated the simulation of three-dimensional fluid flow in pore networks typical for natural porous media into our recent approach to model soil aggregate formation using DLVO theory and diffusion-limited aggregation to overcome its previous limitation to suspensions at rest. To visualize the model capabilities, we simulated aggregation in pore networks that were either synthetically designed to represent certain structural features such as pore junctions and dead-end pores, or taken directly from X-ray µ-CT measurements of undisturbed soil cores. We explored the development of structural aggregated features that evolve in response to flow, transport and the topology of the soil pore space. The resulting three-dimensional arrangement of compounds and the entire aggregates were classified according to their morphological metrics, e.g. the pore space distribution, and functional properties, e.g. the water retention capacity, that are provided by these structures. By this fusion of complementary modeling approaches, we significantly contribute to the fundamental mechanistic understanding of the complex interplay and feedback of structure, interactions and functions on the scale of (micro-)aggregates.
Comparison of global lightning activity variations inferred from Q-bursts, Schumann resonances, and WWLLN-detected lightning strokes
Authors: Szabóné André Karolina , Bór József , Sátori Gabriella , Bozóki Tamás , Steinbach Péter
Published: March 2020

Measured time series of the extremely low frequency (ELF, 3 Hz-3 kHz) band electromagnetic field can be considered as a superposition of background and transient signals. Transient signals produced by exceptionally powerful lightning strokes far from the recording station are named Q-bursts. The direction of the source lightning stroke at the recording station can be calculated using the horizontal components of the Poynting vector. The source lightning stroke can be identified in the lightning database of the World Wide Lightning Location Network (WWLLN, wwlln.net) by the matching detection time and direction calculated from ELF measurements.

Schumann resonance (SR) peaks appear at ~8Hz, ~14Hz, ~20 Hz, etc., in the spectra computed from the background ELF timeseries. SRs are natural electromagnetic resonances with wavelengths comparable to the circumference of the Earth-ionosphere waveguide. Peak amplitudes and frequencies in the resonance spectrum detected in the ELF band at any given location on the Earth depend on the distribution and intensity of the global lightning activity which excites SR.

ELF measurements are routinely performed in the Széchenyi István Geophysical Observatory (NCK, 47°38' N, 16°43' E) near Nagycenk, Hungary. Vertical electric and the horizontal magnetic components of the atmospheric electromagnetic field are monitored by the Schumann resonance recording system. In this work, we study the variation of the number of lightning strokes with high charge moment change (CMC; indicated by the number of large amplitude Q-bursts recorded at NCK) and the variation of the number of lightning strokes with large peak current (indicated by the number of WWLLN-detected energetic lightning strokes). In addition to considering the total number of WWLLN-detected lightning strokes and Q-bursts, we analyze lightning strokes occurring  only in west, south, east, and north directions from NCK, corresponding predominantly to the three main lightning producing regions of the tropical lands in America, Africa, and Indonesia as well as to the Pacific Ocean. Time variations of the number of high CMC and large peak current lightning strokes during November, 2014 are compared with time variation of the cumulative SR intensity detected at NCK station in the vertical electric field component in the same month. Similarities and differences in the time variations of the considered quantities are discussed in order to show how these indicators mirror the changing distributions of the global lightning activity.
Oxidation of black shale and its deterioration mechanism in Xujiaping rockslide, Southwestern China
Authors: Sun Chunwei , Derron Marc-Henri , Jaboyedoff Michel , Ling Sixiang
Published: March 2020

The water-rock chemical interaction of black shale interbedded with limestone along the bedding slip zone and its deterioration to the surrounding rock mass in Xujiaping rockslide is studied. As an important rock-forming mineral in black shale, pyrite is known for being easily oxidized to produce sulfuric acid in water, and sulfuric acid is a significant factor that leads to the dissolution of minerals. Significant number of erosion pits on the limestone were found and many geochemical phenomenon such as extremely low pH fissure water and the secondary mineral phases were investigated. Rock and water samples from this site were analyzed to determine mineralogy, chemical composition and hydrochemistry. The results indicate that many major elements and heavy elements are dissolved, such as Fe, Mn, Si, Zn, Ni, Al, S, Mg, Ca, Na, K, Co and Sr, because of the strong dissolution ability of acid water from black shale.The acid water migrates along the slip zone to exposed surface of cliff and fractures, where it evaporates to form the secondary mineral phases including melanterite, rozenite, szomolnokite, and gypsum etc. The water-rock chemical interaction in Xujiaping rockslide is a combination of dissolution, oxidation, dehydration, and neutralization reactions. Besides, the deterioration mechanism is expanded on two aspects: (1) rock-forming minerals, carbonate minerals especially are prone to be dissolved by sulfuric acid from oxidation of black shale in the slip zone; (2) the crystallization volume expansion of minerals precipitated, which leads to the further expansion and deformation of fractures.
Damage indicators and failure prediction in Focal Mechanism solutions
Authors: Vinciguerra Sergio , King Thomas , Benson Philip , De Siena Luca
Published: March 2020

Acoustic Emissions (AE), the laboratory analogue to seismic events, recorded during conventional triaxial deformation tests allow for an unprecedented amount of information on the evolution of fractured media within a controlled environment. This study presents the results of a new and robust derivation of first motion polarity focal mechanism solutions (FMS). 4 x 10 cm cylindrical samples of Alzo Granite (AG) and Darley Dale Sandstone (DDS) underwent systematic triaxial deformation testing (5, 10, 20 and 40 MPa) in order to investigate the relationships between increasing confining pressure, deformation and failure mode and role of pre-existing microstructure. With an average of 11 of 12 waveforms picked using a neural network for each AE, high resolution datasets are obtained that can track the evolution of deformation structure through time. Focal mechanisms are solved using a least squares minimisation of the fit between projected polarity measurements and the deviatoric stress field induced by tensile, shearing and collapse/closing type sources. Results reveal a surprisingly limited dependency on the distribution of shear fracturing in the lead up to dynamic failure. Instead, deformation is driven by the competition between the opening and closure of fractures that is strongly related to the coupling of local stress fields with pre-existing damage.Spatio-temporal trends in mechanism type and AE amplitude allow for clear identification of: a) Fracture Enucleation. This phase is characterised by broadly distributed tensile fracturing that becomes preferentially aligned as confining pressure increases; b) Fracture Growth. The onset is characterized by a discrete increase in low amplitude shearing events and cyclic fracture development that evolves from a dominance of collapse to shearing followed by tensile fracturing which then returns to collapse type. Influences in mechanism dominance due to rock type are highlighted by increased tensile fracturing in AG, which is replaced by shearing in DDS. A reduction in low amplitude tensile events at 10 MPa in both rock types further reveals a switch from axial splitting to planar localisation as confinement increases; c) Crack Coalescence. The cyclic fracture growth prior to dynamic failure and the amount of strain of this phase share a positive log-linear relationship with confining pressure, allowing to identify the potential for real-time failure prediction; d) Dynamic Failure: High amplitude events characterize the propagation of fractures. Taken together results highlight that failure of the studied samples is the result of the complex interaction between distinct regions of dilatant and compactant deformation. Although planar localisation and preferentially aligned flaws play a more significant role at higher confining pressures, it is the initial heterogeneity or patchiness of the regions undergoing damage that control dynamic failure occurrence and the eventual fracture plane features.
Feasibility of plate tectonics during the Archean: Insights from 3D numerical thermo-mechanical modelling
Authors: Piccolo Andrea , Arndt Nicholas , White Richard , Boris Kaus
Published: March 2020

Slab-pull forces are considered the major driving forces of the present-day plate tectonic. Their efficiency relies on the buoyancy contrast between asthenosphere and subducting plate and on the strength of the latter. Subduction is not only pivotal for understanding the dynamics of plates but also represents the only modern geodynamic setting that produces significant amount of juvenile continental crust and allows exchange between the mantle, lithosphere and atmosphere.

One of the most important unsolved questions is related to the onset of plate tectonics, which is inherently linked to feasibility of the subduction during the early in Earth history. During the Archean, the mantle potential temperature was higher than nowadays, which promoted extensive mantle melting and possibly a weaker lithosphere. The intense magmatism associated with the high mantle potential temperature generated highly residual lithospheric mantle that was more buoyant than the underlying asthenosphere. Altogether these factors may have inhibited the dynamic effect of slab pull and prevented modern style tectonic during the Archean. However, the Archean mantle potential temperature is still not well constrained, and many of these theoretical considerations have not been fully tested by integrating petrological forward modelling into 3D numerical geodynamic modelling.

In our contribution, we focus on the feasibility of modern style plate tectonic as a function of the mantle potential temperature and the composition and structure of the lithosphere. We compute representative phase diagrams that represents the composition of mantle lithospheric and its complementary crust as a function of the mantle potential temperature and integrate them into large-scale 3D numerical experiments. The numerical setup is constructed assuming the existence of a set plates interacting with each other. We prescribe the principal plate boundaries and allow the model to spontaneously evolve as function of the thermal ages of the prescribed plate, testing the effect of continental terrains and oceanic plateau on overall geodynamic evolution. The overall goal is to understand the feasibility of plate tectonics at high mantle potential temperature and to estimate the amount of fluid released by the subduction processes, which provide useful insights on the formation of continental crust.
The Swedish National Seismic Network
Authors: Roth Michael , Lund Björn
Published: March 2020

The Swedish National Seismic Network (SNSN) is operating 69 broadband stations in a latitude range from about N55.5 to N68.5 deg. The southern and northern parts of Sweden are covered more or less evenly with stations having about 100km interstation distances. In the center, between latitudes N61 - N65 deg the stations are situated in a band of about 100 km width following the coast of the Bothnian Sea. The maintenance of this large and distributed network - parts of it in Arctic environment - is challenging. All stations are recording at 100 samples per second and are sending continuous data in near real-time to the SNSN centre at Uppsala University. Seismic data are shared via seedlink directly with seismological institutes in the neighbouring countries, and a subset of the network is made available at ORFEUS. The density, spatial distribution and data avalability of the network allow the production of  a reviewed seismic bulletin with a magnitude completeness down to 0.5. We are currently running several independent automatic processing systems at SNSN: Seiscomp3, Earthworm, SIL/MSIL and an in-house developed waveform-backpropagation algorithm. The SIL system was put in operation 1990 and was originally designed to work decentralized (i.e. phase detection processing at each station computer) and to work with segmented data, suitable for a network with narrow communication bandwidth. SIL was further developed into a version called MSIL, which now performs all steps (detection, associaton and localization) centrally. This not only facilitates station and software maintenance, but also reduces the number of potential points of failure, thereby increasing the data acquisition and processing performance. All the automatic systems are set up for regional and local monitoring. Solutions obtained by the Seiscomp3 and Earthworm system are consistent in location and magnitude for more than 90% of the detected events. The SIL/MSIL and the backpropagation system are targeted to weaker events and they provide additional seismic event locations, but also more spurious events. The current setup of several automatic systems provides operational redundancy and it increases the confidence in the automatic solutions (when detected by more than one system). Eventually we are going to merge the automatic solutions of all systems into one automatic bulletin in order to decrease the workload for analyst review.
The mobile Drilling Information System (mDIS) for core repositories
Authors: Behrends Knut , Heeschen Katja , Kunkel Cindy , Conze Ronald
Published: March 2020

The Drilling Information System (DIS) is a data entry system for field data, laboratory data and sampling data. The International Continental Scientific Drilling Program (ICDP) provides the system to facilitate data management of drilling projects during field work and afterwards. Previously, a legacy DIS client-server application was developed in 1998, and has been refined over the years. The most recent version was released in 2010. However, legacy DIS was locked-in to very specific versions of the Windows- and Office platforms that are non-free, and, more importantly, are no longer supported by Microsoft.

 

Therefore we have developed a new version of the DIS called the mobile DIS, or mDIS. It is entirely based on open-source components and is platform-independent. We have introduced a basic (beta) version of mDIS at EGU 2019. That version was designed for fieldwork. At EGU 2020 we present an extended version designed for core repositories.

 

The basic or expedition mDIS manages basic datasets gained during the field work of a drilling project. These datasets comprise initial measurements of the recovered rock samples, such as core logs, special on-site sample requests, and drilling engineering data. It supports label-printing including QR codes, and the automatic assignment of unique International Geo Sample Numbers (IGSN). The data are available online for all project scientists on site as well as offsite.

 

The curation mDIS, however, satisfies additional requirements of core repositories, which store drill cores for the long term. Additional challenges for the mDIS that occur during long-term sample curation include: (a) the import of large datasets from the expedition mDIS, (b) complex inventory management requirements for physical storage locations, such as shelves, racks, or even buildings, used by the repositories, (c) mass printing of custom labels and custom reports, (d) managing researchers' sample requests, sample curation and sample distribution, (e) providing access to science data according to FAIR principles.
Radial evolution of magnetic field fluctuations in an ICME sheath
Authors: Good Simon , Ala-Lahti Matti , Palmerio Erika , Kilpua Emilia , Osmane Adnane
Published: March 2020

The sheaths of compressed solar wind that precede interplanetary coronal mass ejections (ICMEs) commonly display large-amplitude magnetic field fluctuations. As ICMEs propagate radially from the Sun, the properties of these fluctuations may evolve significantly. We present a case study of an ICME sheath observed by a pair of radially aligned spacecraft at around 0.5 and 1 AU from the Sun. Radial changes in fluctuation amplitude, compressibility, inertial-range spectral slope, permutation entropy, Jensen-Shannon complexity, and planar structuring are characterised.  We discuss the extent to which the observed evolution in the fluctuations is similar to that of solar wind emanating from steady sources at quiet times, how the evolution may be influenced by evolving local factors such as leading-edge shock orientation, and how the perturbed heliospheric environment associated with ICME propagation may impact the evolution more generally.
Determination of hydraulic, mechanical and chemical fracture apertures
Authors: Blum Philipp , Hale Sina , Cheng Chaojie , Kling Tobias , Wendler Frank , Pastewka Lars , Milsch Harald
Published: March 2020

In various reservoirs such as geothermal reservoirs or host rocks for nuclear waste, fractures and in particular fracture apertures play a crucial role in acting as conduits or even barriers, and therefore control fluid flow and solute transport in such reservoirs or host rocks. Often such reservoirs are simulated by discrete fracture network (DFN) models, whose performance however rely strongly on reliable input parameters such as fracture apertures under different conditions. Hence, in this study we examine various novel field and numerical methods, which are able to determine hydraulic, mechanical and even chemical apertures of natural fractures. First, we compare three different methods, (1) syringe air permeameter, (2) microscope camera and (3) laser scanner for determining hydraulic fracture apertures. Our results prove that the air permeameter allows direct and reliable measurements of hydraulic apertures in the laboratory and also in the field. Additionally, the novel air permeameter could be successfully validated by flow through experiments using various types of fractured core samples. In contrast, microscope camera and laser scanner only provide reliable mechanical apertures. In order to also simulate fracture closure under normal stresses, an innovative contact mechanical approach is introduced and validated using a granodiorite fracture. The simulations indicate the best performance for an elastic–plastic (EP) model, which fits almost perfectly the experimentally derived normal closure data. Finally, a phase-field model (PFM) for hydro­thermally induced quartz growth is used to understand the effect of sealing fractures on the flow behaviour. Our results demonstrate that flow behaviour and hydraulic properties of such chemically altered fractures, i.e. chemical fractures, significantly depend on the evolving crystal geometries. Consequently, a novel equation to estimate hydraulic apertures is derived, which includes a geometry factor α for dissimilar crystal geometries (α = 2.5 for needle quartz and α = 1.0 for compact quartz). Finally, the outcome of our studies clearly demonstrate that nowadays novel experimental and numerical methods exist to precisely determine various fracture apertures improving our understanding of coupled processes on the fluid flow behaviour in fractured media.

Acknowledgements to Florian Amann, Christoph Butscher, Frieder Enzmann, Christoph Naab, Jens Oliver Schwarz and Daniel Vogler
Performance of a Physically Based Gap-Filling Technique of in-situ Soil Moisture, in Comparison with Machine Learning
Authors: Lee Seulchan , Jeon Hyunho , Park Jongmin , Choi Minha
Published: March 2020

As the importance of Soil Moisture (SM) has been recognized in various fields, including agricultural practices, natural hazards, and climate predictions, ground-based SM sensors such as Frequency Domain Reflectometry (FDR), Time Domain Reflectometry (TDR) are being widely used. However, gaps in in-situ SM data are still unavoidable due not only to sensor failure or low voltage supply, but to environmental conditions. Since it is essential to acquire accurate and continuous SM data for its application purpose, the gaps in the data should be handled properly. In this study, we propose a physically based gap-filling method in a mountainous region, in which in-situ SM measurements and flux tower are located. This method is developed only with in-situ SM and precipitation data, by considering variation characteristics of SM: increases rapidly with precipitation and decreases asymptotically afterward. SM data from the past is used to build Look-Up-Tables (LUTs) that contains the amount and speed of increment and decrement of SM, with and without precipitation, respectively. Based on the developed LUTs, the gaps are filled successively from where the gaps started. At the same time, we also introduce a machine learning-based gap-filling framework for the comparison. Ancillary data from the flux tower (e.g. net radiation, relative humidity) was used as input for training, with the same period as in the physically based method. The trained models are then used to fill the gaps. We found that both proposed methods are able to fill the gaps of in-situ SM reasonably, with capabilities to capture the characteristics of SM variation. Results from the comparison indicate that the physically based gap-filling method is very accurate and efficient when there’s limited information, and also suitable to be used for prediction purposes.
A new model for brittle failure at depth involving high-pressure metamorphism
Authors: Yamato Philippe , Baïsset Marie
Published: March 2020

Intermediate-depth earthquakes are registered in convergence zones where crustal rocks are expected to deform by ductile flow. This paradox is also evidenced in exhumed crustal rocks where brittle structures (e.g., pseudotachylytes and breccias) associated to high-pressure metamorphism have been documented. If the link between brittle deformation and metamorphic reactions appears obvious today, the mechanism involved is still a burning issue. We propose that the initial heterogeneity of rocks, by itself, is sufficient to trigger both metamorphic reaction and brittle deformation. Based on a mechanically consistent dynamic model, we show that local pressure variations due to pre-existing heterogeneities can be high enough to reach the thermodynamic conditions required for reaction initiation. Brittle behaviour is then controlled by the strength difference between the untransformed host rock and its reaction product. This continuous process also explains the higher pressures recorded in eclogite facies rocks of ductile shear zones compared to their brittle host rock. Our results, constraint by natural data, have therefore significant implications for intermediate-depth seismicity.
Laboratory and modelling investigations of potential geochemical reactions upon seasonal heat storage in Danish geothermal reservoirs
Authors: Holmslykke Hanne Dahl , Kjøller Claus , Weibel Rikke , Fabricius Ida Lykke
Published: March 2020

Seasonal storage of excess heat in hot deep aquifers is one of the considered solutions to optimize the usage of commonly available energy sources. This study investigates the risk of damaging the reservoir through potential geochemical reactions induced by the increased reservoir temperature upon injection of heated formation water. Three core flooding experiments were performed at reservoir conditions and temperatures up to 150°C with cores from two potential Danish geothermal reservoirs and with synthetic brine as the flooding fluid. The tested reservoir sandstones comprise two samples with different mineralogy from the Upper Triassic – Lower Jurassic Gassum Sandstone Formation and one sample from the Lower Triassic Bunter Sandstone Formation. For the calcium carbonate-containing Bunter Sandstone formation, the experiments were performed with Ca-depleted synthetic formation water to avoid loss of injectivity by calcium carbonate scaling at elevated temperatures. The interpretation of the laboratory experiments was supported by petrographic analysis of the cores prior to and after the flooding experiments and by geochemical modelling. The results show that heating induced a series of silica dissolution/precipitation processes for all three sandstones, including dissolution of quartz, alteration of Na-rich feldspar to kaolinite, replacement of plagioclase with albite and precipitation of muscovite, depending on the sandstone. These processes are not expected to significantly deteriorate the physical properties of the reservoir. However, for the Bunter Sandstone Formation, flushed with Ca-depleted brine, a significant portion of the cementing calcite dissolved. In the reservoir, this may ultimately reduce the mechanical strength of the geological formation. Thus, this study suggests that heat storage in geothermal reservoirs can be technically feasible in typical and extensive Danish geothermal sandstone reservoirs. However, in reservoirs containing calcium carbonate, means for avoiding calcium carbonate precipitation during heat storage should be chosen with caution to minimise possible reservoir damaging side effects.
The application of FengYun-3 Microwave Radiation Imager soil moisture product in drought monitoring
Authors: Sun Ruijing , Zhang Yeping , Wu Shengli
Published: March 2020

FY-3(Feng Yun 3) satellites series are the China’s second-generation polar-orbiting meteorological satellites. FY-3B is the second satellite of FY3 series which was launched on November 5, 2010. One of the eleven instruments on board the FY-3B satellite is the Microwave Radiation Imager (MWRI) which is a highly sensitive microwave radiometer. It is China’s first space-borne microwave radiometer. It has 5 different frequencies from 10.65GHz to 89GHz with dual polarization. The MWRI instrument provides measurements of terrestrial, oceanic, and atmospheric parameters, including precipitation rate, sea ice concentration, snow water equivalent, soil moisture, atmospheric cloud water, and water vapor. Soil moisture, as a key parameter in the drought monitoring, becomes especially concerned. The FY-3B/MWRI soil moisture product provides global observations of land surface soil moisture. The current soil moisture retrieval algorithm of FY-3B/MWRI uses the brightness temperature with both v and h polarizations of 10.65GHz to eliminate the effects of surface roughness and vegetation simultaneously. For the bare surface soil estimation part, the algorithm is based on a parameterized surface emission model (the Qp model) which uses a physically based soil moisture inversion technique for application with passive microwave measurements. For the vegetation correction part, the algorithm uses the empirical relationship between the NDVI and the vegetation water content to estimate the vegetation optical depth. The spatial resolution of FY-3B/MWRI soil moisture product is 0.25°×0.25°. In recent years, drought occurs frequently worldwide. As the only microwave sensor which operationally provides global soil moisture products currently in china, the FY-3B/MWRI soil moisture product plays an important part in drought monitoring during the meteorological service. In the summer of 2014, Henan Province which is located in the middle area of China suffered severe drought. The soil moisture of this area remained a very low level all along until significant precipitation finally came in last September. In the year of 2018, there was a severe drought occurred in Afghan, we used a long-time data series to analyze this drought event. The result showed that the FY-3B/MWRI soil moisture can objectively reflect the spatial distribution and development process of drought. This paper will give an introduction of the applications of FY-3B/MWRI soil moisture product during these drought event.
How heterogenous distributions of hydrophobicity affects the capillary rise in soil
Authors: Bentz Jonas , Kroener Eva , Patel Ravi , Haupenthal Adrian
Published: March 2020

A central component of the rhizosphere is root mucilage, a hydrogel exuded by plants that dramatically alters chemical and physical properties of the soil. It is characterized by its large water holding capacity and is hydrophilic or hydrophobic depending on its hydration status: when swollen, mucilage is hydrophilic but becomes hydrophobic when dry, forming local hydrophobic spots on the surface of soil particles. The morphology of these hydrophobic regions formed by dried mucilage is affected by the type of mucilage and microorganisms and can vary from isolated local spots, to networks spanning across larger areas of the soil particle surface. However, until now the understanding on how this heterogeneous distribution and its morphology affect water retention and water repellency in soil is limited.

Therefore, the goal of this study is to investigate the impact of the spatially heterogeneous interfacial tension distributions on the capillary rise in soil. We utilize a two phase flow model based on the Lattice-Boltzmann to numerically simulate capillary rise between parallel slides having a heterogeneous distribution of interfacial tension during imbibition and drainage.

The simulations allow us to quantitatively evaluate how heterogeneous micro-scale distributions of interfacial tension affect the macro-scale water retention behavior. This we could approximately explain with three hypotheses: The equilibrium capillary rise volume (i) is a measure for the hydrophilicity of a field, (ii) capillary rise is affected by the standard deviation of the interfacial tension field, (iii) hysteresis is induced by the heterogeneous field and depends on the correlation length of the patterns.

In future, simulations will be extended also to the geometry of real soil.
Mercury and methylmercury along a transect from the Lena river estuary across the Laptev Sea Shelf
Authors: Nguyen Van Liem , Wild Birgit , Gustafsson Örjan , Semiletov Igor , Dudarev Oleg , Jonsson Sofi
Published: March 2020

Widespread accelerated permafrost thawing is predicted for this century and beyond. This threatens to remobilize the large amounts of Mercury (Hg) currently ‘locked’ in Arctic permafrost soils to the Arctic Ocean and thus potentially lead to severe consequences for human and wildlife health. Future risks of Arctic Hg in a warmer climate are, however, poorly understood. One crucial knowledge gap to fill is the fate of Hg once it enters the marine environment on the continental shelves. Arctic rivers are already today suggested to be the main source of Hg into the Arctic Ocean, with dissolved and particulate organic matter (DOM and POM, respectively) identified as important vectors for the land to sea transport.

In this study, we have investigated total Hg (HgT) and monomethylmercury (MeHg) concentrations in surface sediments from the East Siberian Arctic Shelf (ESAS) along a transect from the Lena river delta to the Laptev Sea continental slope. The ESAS is the world’s largest continental shelf and receives large amounts of organic carbon by the great Arctic Russian rivers (e.g., Lena, Indigirka and Kolyma), remobilized from continuous and discontinuous permafrost regions in the river catchments, and from coastal erosion. Data on HgT and MeHg levels in ESAS sediments is however limited. Here, we observed concentrations of Hg ranging from 30 to 96 ng Hg g-1 d.w. of HgT, and 0.03 to 9.5 ng Hg g-1 d.w. of MeHg. Similar concentrations of HgT were observed close to the river delta (54 ± 19 ng Hg g-1 d.w.), where >95 % of the organic matter is of terrestrial origin, and the other section of the transect (42 ± 7 ng Hg g-1 d.w.) where the terrestrial organic matter is diluted with carbon from marine sources. In contrast, we observed higher concentrations of MeHg close to the river delta (0.72 ± 0.71 ng Hg g-1 d.w. as MeHg) than further out on the continental shelf (0.031 ± 0.71 ng Hg g-1 d.w. as MeHg). We also observed a positive correlation between the MeHg:Hg ratio and previously characterized molecular markers of terrestrial organic matter (Bröder et al. Biogeosciences (2016) & Nature Com. (2018)). We thus suggest riverine inputs, rather than in situ MeHg formation, to explain observed MeHg trends.
Post-Event Reviews for building Wildfire Resilience: The case of Tasmania, Australia
Authors: Keating Adriana , Handmer John
Published: March 2020

Wildfire frequency and severity is dramatically increasing. Wildfires cause loss of life and destroy human and natural assets; smoke chokes cities; large fires release significant amounts of carbon; and fires can permanently change ecosystems so they are less effective carbon sinks. Countries with a history of wildfire, such as Australia, are facing unprecedented fires that outstrip response capacity.

Yet even in the worst catastrophes, scant attention is being paid to the massive potential for community-based initiatives to reduce risk and enhance resilience. The vast majority of wildfire reviews focus on suppression operations, and there is a clear need for these to be complemented with broader learning that provides holistic insights about how wildfire risk is generated, and how resilience might be increased.

This presentation will report on the findings from one such comprehensive and holistic review of a wildfire disaster in southwest Tasmania, Australia, in January 2019. The event resulted in a locally unprecedented human and animal evacuation, and burnt through large swathes of precious wilderness world heritage area. Utilising the Post-Event Review Capability (PERC) methodology, this study investigated the causes, successes and failures of this disaster. This presentation will present findings and recommendations that are locally actionable yet provide a number of generalised lessons pertinent across multiple risk contexts. Findings demonstrate the significance of community-based actions for wildfire risk management.
Transient simulations of the last deglaciation with interactive carbon cycle using CLIMBER-X
Authors: Willeit Matteo , Ganopolski Andrey
Published: March 2020

The processes leading to the observed atmospheric CO2 variations of ~80 ppm between glacial and interglacial times associated with the glacial cycles of the past million years are still not fully understood. Computationally efficient Earth system models are a unique tool to help elucidate the mechanisms behind the CO2 variations. Here we use the newly developed Earth system model of intermediate complexity CLIMBER-X to explore the effect of different processes on the atmospheric CO2 evolution since the last glacial maximum using transient simulations.

CLIMBER-X includes the frictional-geostrophic 3D ocean model GOLDSTEIN coupled to the HAMOCC ocean and sediment carbon cycle model, the semi-empirical statistical-dynamical atmosphere model SESAM and the land model PALADYN. The model also includes the ice sheet model SICOPOLIS, but for in presented experiments the ice sheets are prescribed from reconstructions. CLIMBER-X can simulate ~10,000 model years per day.

In transient experiments of the last 20,000 years we test the sensitivity of simulated atmospheric CO2 to changes in ocean circulation, ocean temperature, sea level, atmospheric dust deposition and the model representation of crucial ocean biogeochemistry and land carbon cycle processes.
A reconstruction of Iberia accounting for West Tethys/North Atlantic kinematics since the Late Permian-Triassic
Authors: Angrand Paul , Mouthereau Frédéric , Masini Emmanuel , Asti Riccardo
Published: March 2020

The West European kinematic evolution results from the opening the West Neo-Tethys and the Atlantic oceans since the Late Paleozoic and the Mesozoic, respectively. Geological evidence suggests that the Iberian domain was strongly overprinted by the propagation of these two rift systems and is therefore key to significantly advance our understanding of the regional plate reconstructions. The Late Permian-Triassic tectonic evolution of Iberian rift basins show that they have accommodated a significant component of extension, which remain however difficult to quantify. This tectonic stage is therefore often neglected in most plate kinematic models, leading to the overestimation of the movements between Iberia and Europe during the subsequent Mesozoic (Early Cretaceous) rift phase.

We compile seismic profiles and geological constraints along the North Atlantic margins and over Iberia, as well as existing kinematic and paleogeographic reconstructions to build a coherent, global kinematics model that consider both the Neo-Tethyan and Atlantic evolutions. We use tectonic subsidence analyses from the literature to quantify the apparent extension during the Late Permian to Early Cretaceous extensive phase. We show that an improved knowledge of the distribution in space and time of the deformation between Europe and the Iberian domain can be obtained for the Late Permian-Mid Cretaceous period. Our model differs from standard models that consider left-lateral strike-slip movement localized in the northern Pyrenees. The Europe-Iberia plate boundary rather forms a domain of distributed and oblique extension made of two rift systems, in the Pyrenees and in the Iberian intra-continental basins. This reconstruction emphasizes the need for an Ebro block and the significant strike-slip movement south of the Ebro block that is however minimized by accounting for the previous Late Permian-Triassic extension. We propose that these two rifts accommodated the same order of magnitude of strike-slip movement during the evolution of the Iberia-Europe (diffuse) plate boundary.

Our reconstructions reveal that the Late Permian-Triassic rift and magmatic evolution of the western Europe, at the western tip of the Neo-Tethyan Ocean, controlled the subsequent localization of the Atlantic rift. Our study provides a significant advance that allows reconciling the main geological observations, including the lack of major strike-slip faulting and a large oceanic basin in northern Iberia. The temporal overlap between Late Variscan magmatism and the Neo-Tethyan extension is not directly addressed in this contribution but its impact on the Earth’s surface evolution and topography during initial rifting certainly requires further investigations.