bluuebunny/crossref_metadata_2025 huggingface dataset:
Detecting explosion-induced dynamic phenomena using time-lapse seismic surveying
Authors: Mathew Shaji , MacBeth Colin , Mangriotis Maria-Daphne , Stevanovic Jenny
Published: March 2020

Characterization of seismic events as underground nuclear explosions is a challenging task. Geophysical methods such as seismic monitoring systems are used by CTBTO to link post-explosion phenomena to potential sources. The main challenges in seismic monitoring involve accurately locating of sources and separating underground variations in seismic properties due to the explosion from naturally occurring variations. Underground detonations result in an immense change in pressure and temperature concentrated around the source origin. This results in the formation of characteristic static and dynamic phenomena. This study highlights the potential of using time-lapse seismic to identify ground zero by monitoring post-explosion dynamic phenomena. Time-lapse seismic, also known as 4D seismic, is successfully employed in the oil and gas industry for petroleum production monitoring and management. It involves taking more than one 2D/3D seismic at different calendar times over the same reservoir and studying the difference in seismic attributes.

Following an underground explosion, dynamic changes in rock and fluid properties are observable for a prolonged period, even up to several decades. This is prominent near to source origin, and it is a result of the redistribution of residual energy, such as pressure, temperature, and saturation. Frequent seismic monitoring surveys (time-lapse seismic) enables one to monitor the changes in rock and fluid properties. This study presents the characteristics of the time-lapse seismic signature observed in a heterogeneous medium (or heterogeneous cavity). We will look into the impact of factors affecting land 4D repeatability on the 4D signature. The significance of identifying the 4D signature related to the explosion in a seismic section, and the feasibility of detecting it during the OSI with resource and time constraints in place will be discussed. We present a fast detection method using a convolutional neural network for the detection of explosion related time-lapse signature, which could be an identifier of the source location or ground zero.

Acknowledgments: Authors would like to thank EPSRC and AWE for funding this project.
The Mw4.9 Le Teil surface-rupturing earthquake in southern France: New insight on seismic hazard assessment in stable continental regions
Authors: Ritz Jean-François , Baize Stéphane , Ferry Matthieu , Larroque Christophe , Audin Laurence , Delouis Bertrand , Mathot Emmanuel
Published: March 2020

On November 11th 2019, a Mw 4.9 earthquake shook the Rhone River Valley in southern France, a rather densely populated area with many industrial facilities including several nuclear power plants. The “Le Teil” earthquake was felt as far as Montpellier and Grenoble, 120 km from the epicenter. Seismological data promptly showed that the earthquake corresponded to a reverse faulting event along a NE-SW trending fault with a focus at a very shallow depth (~1 km). In parallel, satellite-based radar observations (InSAR) showed the uplift of the SE compartment (up to 10 centimeters) along a sharp NE-SW trending ~4.5-km-long discontinuity. Field investigations conducted in the following days and weeks in the epicentral area uncovered several evidences of surface ruptures across roads and paths where the InSAR discontinuity is mapped. We also carried out airborne LiDAR surveys to map the rupture below the dense forest cover. Characteristics of surface deformations are fully consistent with InSAR and seismological data, and allow concluding to the reactivation of an Oligocene normal fault segment (i.e. La Rouvière fault) that belongs to the Cévennes fault system, a 120 km long polyphased system bounding the southern rim of the Massif Central. The absence of clear cumulative compressional deformation along the fault rupture, which on the contrary displays inherited extensional deformation (most likely Oligocene in age), suggests that the fault has not moved significantly since millions of years. These observations relaunch the question of seismic hazard assessment in stable continental regions such as continental France and most of Western Europe, where strain rates are very low.
Magnitude and Frequency of the Largest Palaeofloods during the Holocene in Nahal Ze'elim and Nahal Rahaf, Judea Desert, Israel
Authors: Zituni Rami , Greenbaum Noam , Zilberman Ezra
Published: March 2020

The Judea Desert constitutes a distinctive hydrological region characterized by short and steep ephemeral streams draining eastward to the Dead Sea Valley. The aridity of the Judea desert is caused by the rain-shadow effect of the north-south, mountainous back bone (MBB) of Israel, as well as by the low elevations within the Dead Sea valley. The hydrological data for these streams is scarce, which leads to poor estimation of the magnitude and frequency of floods. The lack of data is particularly significant when planning infrastructure such as roads, bridges, reservoirs, dams etc. Flood frequency analysis for risk assessment is therefore, based on various models such as rainfall-runoff, empirical, regional models etc.

The current study is based on Palaeoflood Hydrology  which uses geomorphological evidence for real floods that accumulate in typical natural traps, along the course of the streams for hundreds and thousands of years. The collection of these data enables us to reconstruct the history of the floods in the streams including/at least the largest event that occurred in the stream in the last hundreds to thousands years. By combining these data with measured and historical data (if any), a long, solid database can be reconstructed. The applicability of the system in Israel has been proven in the larger streams in the Negev.  However, the Negev Desert is a significantly different hydrological environment. The  largest flood that occurred in the stream is important for regional envelope curves. Long palaeoflood records can indicate on changes in the hydrological regime, which testify for climatic fluctuations.

The method is based on field evidence in the form of slackwater deposits and other high water marks, which accumulate in typical sites and indicate on the minimum water elevation enabling discharge calculations using HECRAS hydraulic engineering software. The ages of the floods are determined by dating the flood deposits using radiocarbon and OSL.

In the Upper Nahal Rahaf stream (50 km2), three sites were located with 2-4 flood deposits at each site, including  a rock shelter within which  2 flood remnants with reconstructed peak discharges of 1,200-1,300 m3/s. These flood sediments are overlying  an Upper Paleolithic site dated to about 30 ka.

In Nahal Ze'elim stream (245 km2) 5 sites were located - 4 of which close to the outlet. Each site recorded between 2-8 sedimentary units with reconstructed peak discharges of 200-900 m3/sec.

The integration of the floods from all sites with their age revealed a vast information regarding major events. In further study this will also allow a renewed frequency analysis on the basis of wider knowledge.
Towards a two-axis cold-atom gyroscope for rotational seismology
Authors: Geiger Remi , gautier romain , sidorenkov leonid , landragin arnaud
Published: March 2020

Cold-atom inertial sensors target several applications in navigation, prospection, geoscience and tests of fundamental physics. The operation of these sensors is based on atomic interferometry taking advantage of superpositions between quantum states of different momentum of an atom. These superposition states are obtained by means of optical transitions with two (or more) photons communicating momentum to the atom and acting as beam splitters and mirrors for the matter waves. The SYRTE cold-atom gyroscope currently represent the state of the art of atomic gyroscopes with a short-term sensitivity of 40 nrad/s/sqrt(Hz) limited by vibration noise (using a 4 Hz sampling rate), a long term stability of 3e-10 rad/s and an accuracy of 10 nrad/s. The detection noise limit of the sensor (quantum projection noise) is currently 5 nrad/s/sqrt(Hz) in the band DC-1 Hz, which already represents an interest to sense ground rotations in a typical frequency range between 1 mHz and 1 Hz. A second horizontal axis of measurement is currently being implemented. Moreover, we are designing a new experiment which aims a reaching a (quantum projection noise limited) sensitivity of 1 nrad/s/sqrt(Hz) in this frequency band along two axes of measurement, which represents an interesting perspective for the field of rotational seismology. This contribution will present the results recently achieved with the SYRTE gyroscope experiment to reach state-of-the-art performances and present the route to applications of this sensor in geosciences.

 
Mapping seagrass and water depths using Sentinel-2
Authors: Kuhwald Katja , Held Philipp , Gausepohl Florian , Schneider von Deimling Jens , Oppelt Natascha
Published: March 2020

Seagrass meadows cover large benthic areas of the Baltic Sea, but eutrophication and climate change imply declining seagrass coverage. Apart from acoustic methods and traditional diver mappings, optical remote sensing techniques allow for mapping seagrass. Optical satellite analyses of seagrass mapping may supplement acoustic methods in shallow coastal waters with observations that are more frequent and have a larger spatial coverage.

In the clear Greek Mediterranean Sea, Sentinel-2 was already applied successfully to detect bathymetry and seagrass meadows. We are now testing whether Sentinel-2 data are also suitable for analysing the sublittoral in the turbid waters of the Baltic Sea. We focus on an extensive shallow water area near Kiel/Germany. Based on Sentinel-2 data, we analyse water depth and differentiate between seagrass covered and bare sandy ground. We derive these parameters using empirical and process-based models. First results show that Sentinel-2 allows to determine water depths up to 4 m (RMSE ~ 0.2 m). Comparisons with LiDAR water depths show that inaccuracies increase in overgrown areas. Our study also shows that the atmospheric correction algorithm influences sublittoral ground mappings with Sentinel-2 data. For instance, the absolute water depths of the process-based modelling differ up to 2.5 m on average depending on the atmospheric correction algorithm (ACOLITE, Sen2Cor, iCOR).

Comparing Sentinel-2 seagrass classifications with diver mappings and aerial imagery emphasises that empiric approaches provide plausible sublittoral ground classifications up to approximately 4 m water depth. Combining these results with seagrass mappings based on acoustic measurements (deeper than 4 m water) provides a synthesised sublittoral classification map of the study area up to the present growth limit of seagrass (~ 7 m in the study area).

The Baltic Sea is considered as a very turbid environment, nevertheless we show that satellite-based remote sensing has a great potential for shedding light into the  "white ribbon". The spatial coverage and temporal resolution of the analysed Sentinel-2 data increases the knowledge about the occurrence of seagrass and its spatio-temporal dynamics. Nevertheless, the influence of the selected atmospheric correction approach on the results shows that further research in remote sensing is necessary to assess seagrass meadows reliably.
VIS-NIR wavelength importance in SOC models
Authors: Reyes Javier , Ließ Mareike
Published: March 2020

Soil organic carbon (SOC) is a key soil property attracting special interest in the study of agricultural systems. Striving towards more effective SOC data acquisition, the use of VIS-NIR spectroscopy has increased over the last years. The interpretation of the recorded signal information with regards to SOC is not trivial as spectral absorption features are caused by the stretching and bending of structural molecule groups which are embedded in a complex soil matrix. The aim of this study was to assess spectral wavelength importance in partial least square regression (PLSR) models for SOC prediction. Surface soil samples were obtained from a long-term field experiment (LTFE) located in the state of Saxony-Anhalt, Germany. The LTFE presented a high variability of SOC values due to the different organic and mineral fertilization treatments. Data sets of Vis-NIR spectra were acquired in the lab and field using an ASD field spectrometer. Then, different preprocessing methods were applied before building the models. Finally, the wavelength importance was observed using regression coefficients (RC) and variable importance projections (VIP). As expected, lab data showed higher accuracy in SOC predictions (RMSE: 0.10-0.12%) compared with field data (RMSE: 0.18-0.20%). Overall, the VIP indicator provided more identifiable peaks at specific wavelength ranges, and it was more consistent among the preprocessing methods compared with RC for both lab and field data. Although model uncertainties were higher with field measurements, the importance of some wavelengths was maintained. Overall, this information is essential for model interpretation and tells us about disturbance effects in spectral field measurements compared to lab measurements.
Improving geomorphological process understanding of complex glacier surfaces using aerial robotics
Authors: Westoby Matt , Rounce David , Shaw Thomas , Fyffe Catriona , Moore Peter , Stewart Rebecca , Brock Ben
Published: March 2020

In the last decade or so, improvements in unpiloted aerial systems (UAS) technology and the emergence of low-cost digital photogrammetry have democratised access to accurate, high-resolution topographic data products, particularly in remote, glacial environments. One such application of these tools has been for advancing understanding of debris-covered glaciers (DCG) which are an important component of the high-mountain cryosphere, but also where detailed, ground-based process analysis is challenging. In this work, we seek to improve meso-scale (<km) geomorphological understanding of DCG surface evolution over multi-annual timescales by quantifying how debris moves around on the surface of these glaciers, and how debris transport is reconciled with wider patterns and mechanisms of ice mass loss. We applied annual UAS-photogrammetry and DEM differencing alongside debris thickness and debris stability modelling to unravel the evolution of a 0.2 km2 sub-region of the debris-covered Miage Glacier, Italy, between June 2015 and July 2018. Following corrections for glacier flow, DEM differencing revealed widespread surface lowering (mean 4.1 ± 1.0 m a-1; maximum 13.3 m a-1). We combined DEMs of difference with local meteorological data and a sub-debris melt model to produce high resolution (metre-scale) maps of debris thickness. Median debris thicknesses ranged from 0.12 – 0.17 m and were highly spatially variable. Debris thickness differencing revealed localised debris thinning across ice cliff faces, except those which were decaying, where debris thickened, as well as ingestion of debris by a newly exposed englacial conduit. Debris stability mapping showed that 18.2 - 26.4% of the survey area was theoretically subject to debris remobilisation in a given year. By linking changes in stability to changes in debris thickness, we observed a net debris thinning signal across slopes which become newly unstable, and a net thickening signal across those which stabilise between years. Finally, we linked morphometric descriptors of the glacier surface with debris thickness change data to derive empirical relationships which describe observed rates of downslope debris thickening as a function of slope-distance and slope angle. These UAS-enabled data provide new insight into mechanisms and rates of debris redistribution on glacier surfaces over sub-decadal timescales, and open avenues for future research to explore patterns of debris remobilisation and the morphological evolution of glacier surfaces at much larger spatiotemporal scales.
A combined approach in determining late Quaternary fluctuations in deep water masses derived from neodymium isotopes, faunal variations and d13C in foraminifera along the western continental slope of South Africa
Authors: Bergh Eugene , Compton John , Zabel Matthias
Published: March 2020

The Meridional Overturning Circulation is crucial in regulating Earth‘s climate and is composed of various ocean currents, playing an important role in heat exchange and the distribution of water masses. The transfer of water masses also affects regional carbon storage, nutrient contents, temperature, evaporation and precipitation balances in the oceans. The advancement in our understanding of the interaction between these water masses can contribute to our current knowledge on the state of the oceans. The use of foraminiferal isotope geochemistry and faunal analyses has greatly contributed to understanding the changes our oceans have undergone in the Quaternary. The purposes of this study are to determine what the timescales were at which the bottom water masses were changing and to determine at which periods the influence of these water masses were the strongest. A combination of neodymium and δ13C isotopes, as well as faunal abundance records in this study, were derived from foraminifera in cores recovered at 3522 m and 3631 m water depths along the western margin of South Africa to investigate deep water mass variability in the southeast Atlantic Ocean during the last two glacial terminations. The neodymium isotope composition (143Nd/144Nd), expressed as εNd, were measured in planktic foraminifera from the western continental slope of South Africa. This isotopic tracer is useful in tracking deep water masses on the sub-millennial scale owing to the short residence time of Nd in seawater. Foraminifera (single-celled protists) microfossils acquire the bottom water Nd signature upon burial that can be useful in providing insight into the variability of deep water masses. In addition to the εNd records, the foraminiferal δ¹³C results also support the results of the neodymium isotopes. These records in this study are largely correlative with the abundances of benthic species Cibicidoides wuellerstorfi, reflecting shifts between the southern-sourced Antarctic Bottom Water (AABW) and the northern-sourced North Atlantic Deep Water (NADW) during the last two glacial terminations at ~130 ka and ~18 ka. The εNd, δ¹³C results and C. wuellerstorfi relative abundances indicate an intensified inflow of southern-sourced water masses and weakened NADW inflow along the margin during peak glacial periods MIS 6 and MIS 2. The terminations of these peak glacials were more beneficial to stronger penetration of NADW into the southeast Atlantic.
A Study on Development of Test Complex for Natural Circulation Agriculture in Reclaimed Land
Authors: Seo Donguk
Published: March 2020

Reclaimed land in Korea is increasingly being used for horticulture, grains, livestock, etc. However, soil reclaimed land located in coastal lowland have so high salinity, poor fertility, high possibility of pollution that farming is difficult. Therefore, it is needed to reduce environmental burden and to promote fertility of soil through natural circulation farming. Therefore, we presented sustainable eco-friendly natural circulation model of agricultural resources in reclaimed land. It promotes desalination and fertility of soil through eco-friendly circular farming by integrating horticulture and livestock. To demonstrate the model, the test complex is planned to apply energy and resources circulation between horticulture and livestock focusing on Hanwoo, Korean-bred cattle. Basically high-technical plastic greenhouse-type horticultural complexes and livestock complexes including fuel facility using manure pellet are planned. Additionally, agricultural product processing, sales and distribution centers, themed landscape agricultural complexes, ecological parks, agricultural tourism facilities, and observation facilities were arranged.
Towards an improved understanding of high-resolution impurity signals in deep Antarctic ice cores
Authors: Bohleber Pascal , Roman Marco , Barbante Carlo , Stenni Barbara , Delmonte Barbara
Published: March 2020

Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) offers minimally destructive ice core impurity analysis at micron-scale resolution. This technique is especially suited for exploring closely spaced layers of ice within samples collected at low accumulation sites or in regions of highly compressed and thinned ice. Accordingly, LA-ICP-MS promises invaluable insights in the analysis of a future “Oldest ice core” from Antarctica. However, in contrast to ice core melting techniques, taking into account the location of impurities is crucial to avoid misinterpretation of ultra-fine resolution signals obtained from newly emerging laser ablation technologies. Here we present first results from a new LA-ICP-MS setup developed at the University of Venice, based on a customized two-volume cryogenic ablation chamber optimized for fast wash-out times. We apply our method for high-resolution chemical imagining analysis of impurities in samples from intermediate and deep sections of the Talos Dome and EPICA Dome C ice cores. We discuss the localization of both soluble and insoluble impurities within the ice matrix and evaluate the spatial significance of a single profile along the main core axis. With this, we aim at establishing a firm basis for a future deployment of the LA-ICP-MS in an “Oldest Ice Core”. Moreover, our work illustrates how LA-ICP-MS may offer new means to study the impurity-microstructure interplay in deep polar ice, thereby promising to advance our understanding of these fundamental processes.
Understanding long-term persistence and multifractal behaviors in river runoff: A detailed study over China
Authors: Yuan Naiming , Wu Wenlu , Xie Fenghua , Qi Yanjun
Published: March 2020

Long-term persistence (LTP) and multifractality in river runoff fluctuations have been well recognized over the recent decades, but the origins of these characteristics are still under debate. In this study, runoff and precipitation data from China are analyzed using detrended fluctuation analysis (DFA) and its generalized version, multifractal detrended fluctuation analysis (MF-DFA). By comparing the results between runoff and the nearby precipitation data, we find the multifractal behaviors in river runoff may be propagated from the nearby precipitation data, but the LTP is not inherited from precipitation. The LTP in river runoff may arise from the spatial aggregation effect, as it is closely related with the catchment area, especially for stations with large catchment areas. These findings are based on data from China, which was not analyzed systematically due to the poor data availability. Since the existence of LTP and multifractality makes the runoff change not completely random, one should further introduce these characteristics into hydrological models, for improved water managements and better estimations of hazard risks.
Torrential rainfall prediction: WeMOTool
Authors: Arbiol-Roca Laia
Published: March 2020

The Western Mediterranean Oscillation index (WeMOi) presents a statistically significant relationship with the pluviometric totals of the eastern façade of the Iberian Peninsula. Use of the WeMOi at daily resolution has proven to constitute a useful tool for helping to predict torrential rainfall episodes in the east of the peninsula. The present research attempts to determinate which atmospherics circulations defines the WeMOi phases. Also, the WeMOi research has focused on the prediction of it in order to configure itself as a predictive tool, the WeMOTool, for torrential rains associated, especially during the autumn months. The calculation of this index is made using the surface pressure data of the GFS model and is updated with the model outputs at 00h and 12h and up to 144h.
Thermochronological constraints on the Late Cenozoic evolution of the northeastern Pamir
Authors: Chen Shenqiang
Published: March 2020

Situated at the northwestern end of the India–Asia collision zone, the northeastern Pamir is an important area to explore intracontinental tectonic processes and geodynamic models. In this study, thermochronology is applied to constrain the Late Cenozoic exhumation history of the northeastern Pamir. A new thermochronological data set, combined with previous thermochronological data, suggests that (1) the Late Cenozoic exhumation of the northeastern Pamir began at ~22–18 Ma; (2) the strong crustal contraction in the hinterland of the northeastern Pamir occurred during ~13–10 Ma and ~8–6 Ma; and (3) the east-west extension along the Kongur Shan dome initiated at ~5–3 Ma, and it has resulted in the exhumation of the core of the dome with an average rate of ~2–4 mm/a. I propose that (1) the Early Miocene exhumation of the northeastern Pamir is related to the initiation of the Main Pamir thrust; (2) the first and second stages of the strong crustal contraction are respectively correlated with the northward propagation of the crustal channel flow in the northeastern Pamir and the initial collision between the northeastern Pamir and the Tian Shan; and (3) the east-west extension is driven by the extrusion of the ductile channel flow.
Laboratory investigation of air-sea momentum transfer under severe wind conditions
Authors: Vdovin Maksim , Baydakov Georgy , Sergeev Daniil , Troitskaya Yuliya
Published: March 2020

Wind-wave interaction at extreme wind speed is of special interest now in connection with the problem of explanation of the sea surface drag saturation at the wind speed exceeding 30 m/s. Now it is established that at hurricane wind speed the sea surface drag coefficient is significantly reduced in comparison with the parameterization obtained at moderate to strong wind conditions.

The subject of this work is investigation of aerodynamic resistance of the waved water surface under severe wind conditions (up to U10 ≈ 50 m/s). Laboratory experiments were carried out at the new high-speed wind-wave flume in the Large Thermally Stratified Tank (at the Institute of Applied Physics, Russia) built in 2019. The main difference between the new wind-wave flume and the old one is the absence of a pressure gradient along the main axis of the new flume. Aerodynamic resistance of the water surface was measured by the profile method with Pitot tube. A method for data processing taking into account the self-similarity of the air flow velocity profile in the aerodynamic tube was applied for retrieving wind friction velocity and surface drag coefficients. Simultaneously with the airflow velocity measurements, the wind-wave field parameters in the flume were investigated by system of wire gauges.

Analysis of the wind velocity profiles and wind-wave spectra showed tendency to decrease for surface drag coefficient for wind speed exceeding 25 m/s simultaneously with the mean square slope and significant wave height.

Acknowledgments
This work was carried out with the financial support of the RFBR according to the research project 18-55-50005, 20-05-00322, 18-35-20068, 18-05-00265. Data processing was carried out with the financial support of Russian Science Foundation grant 19-17-00209.
Optimising Fertilisation Strategy for Nitrogen Uptake Efficiency
Authors: McKay Fletcher Daniel , Ruiz Siul , Duncan Simon , Chadwick Dave , Jone David , Roose Tiina
Published: March 2020

Sufficient nitrogen fertilisation is essential for obtaining the crop yields required to feed the growing population. Moreover, nitrogen applied to fields is often lost to a number of processes including denitrification, surface run-off and leaching. These processes can damage the local ecology and contaminate water supplies. Additionally, nitrogen lost as ammonia gas and the large energy input required to synthesize ammonia are both large contributors to global greenhouse gas emissions. Choosing fertilisation strategies to optimise the proportion of nitrogen taken up by crops (nitrogen use efficiency) can reduce the production of ammonia and the pollution of water supplies.

We developed a mathematical model that describes the movement of water and multiple nitrogen species in soil at the field scale over a growing season. The model was then used to assess the nitrogen use efficiency of varying fertilisation strategies. We consider the effects of a number of biological, chemical, and physical processes including: root growth, root uptake, the transformation of nitrogen between different nitrogen species, and the effect of soil water movement on nitrogen transport. The resulting model is comprised of a coupled system of partial and ordinary differential equations that describe the mathematical interplay between nitrogen transport, water movement, and root uptake, which were solved numerically using a finite element approach. Numerical experiments were conducted to determine how nitrogen uptake efficiency was affected by different fertilisation strategies. We examine numerous cases by varying the quantity of fertiliser applied to the soil and the fertiliser application times.

The numerical experiments suggest that, under uniform rainfall rates, the optimal fertilisation times (within the bounds of typical times found in agriculture) can result in 25% more nitrogen uptake than the worst strategies. However, there were large time periods, 28 days for the first application and 10 days for the second, which resulted in close-to-optimal nitrogen use efficiency. The results of this study, in addition to crop health and past and predicted rainfall, could be taken into consideration by farmers while choosing fertilisation times to optimise nitrogen uptake efficiency.
Multi-point observations of a reconnection outflow associated with interacting flux ropes in the solar wind
Authors: Vörös Zoltan , Yordanova Emiliya , Roberts Owen , Narita Yasuhito
Published: March 2020

Twisted magnetic flux ropes embedded in an interplanetary coronal mass ejection (ICME) often contain oppositely oriented magnetic fields and potentially reconnecting current sheets. Reconnection outflows in the solar wind can be identified through magnetic field and plasma signatures, for example, through decreasing magnetic field magnitude, enhanced bulk velocity, temperature and (anti)correlated rotations of the magnetic field and plasma velocity. We investigate a reconnection outflow observed by ACE, WIND and Geotail spacecraft within the interaction region of two flux ropes embedded into an ICME. The SOHO spacecraft, located 15 RE upstream, 120 RE in GSE Y and 5 RE in GSE Z direction from the ACE spacecraft, does not see any plasma signatures of the reconnection outflow. At the same time the other spacecraft, also separated by more than 200 RE in X and Y GSE directions, observe strong plasma and magnetic field fluctuations at the border of the exhaust.  The fluctuations could be associated with Kelvin-Helmholtz (KH) instability at the border of the reconnection outflow with strong flow shear.  It is speculated that the KH instability driven fluctuations and dissipation is responsible for stopping the reconnection outflow which is therefore not seen by SOHO.
Enhancing water management by using glacial lakes: examples of opportunities and risks from deglaciated Cordillera Negra, Peru
Authors: Emmer Adam
Published: March 2020

Peruvian Cordillera Negra (8°40’ – 10°30’ S; 77°20’ – 78°30’ W) is characterised by dry semi-arid climate and a general lack of water, especially during the dry season (April – October). Numerous glacial lakes – remnants of the past glaciation of this currently glacier ice-free mountain range – thus represent an important water reservoirs. Glacial lakes sustain environmental flows during dry season, store water for grazing animals as well as simple agricultural irrigation. At the same time, climate change and socio-economic development drive increasing pressure on water resources in the region.

To further enhance potential of glacial lakes in water management, hundreds of glacial lakes of the Cordillera Negra have been equiped by damming structures in order to: (i) increase the volume of retained water; (ii) manage the outflow throughout the seasons of the year. Two general types of dams are distinguished: (i) traditional dams (built by local communities from stones, turf and clay); and (ii) modern dams (concrete or embankment earth- or rock-filled). While these dams help to retain water and the idea is promising, the implementation and dam management lag behind.

During the field visit conducted in 2019, many of the visited dams (both traditional and modern) were documented to leak through; attempts to retain as much water as possible also led to the intentional blocking of spillways, reducing dam freeboard to only tens of cm in some cases. In the worst case, these unacceptable management practices might result in dam overtopping or dam failure. Despite the uppermost part of the Cordillera Negra is not densely settled, some of the glacial lakes are located upstream mining areas, so that there is a risk of environmental pollution and contamination in case of flood. These observations suggest that glacial lakes can successfully be used in water mangement, however, they need to be managed properly and continuously.
Image-based model quantification of pore-scale nitrogen diffusion and potential microbial ‘dead zones’ induced by fertilization application
Authors: Ruiz Siul , McKay Fletcher Daniel , Boghi Andrea , Williams Katherine , Duncan Simon , Scotson Callum , Petroselli Chiara , Dias Tiago , Chadwick Dave , Jones David , Roose Tiina
Published: March 2020

Soil microbial communities contribute many ecosystem services including soil structure maintenance, crop synergy, and carbon sequestration. However, it is not fully understood how the health of microbial communities is effected by fertilization at the pore scale. This study investigates the nature of nitrogen (N) transport and reactions at the soil pore scale in order to better understand the influence of soil structure and moisture content on microbial community health. Using X-ray Computed Tomography (XRCT) scans, we reconstructed a microscale description of a dry soil-pore geometry as a computational mesh. Solving two-phase water/air models produced pore-scale water distributions at 15, 30 and 70% water-filled pore volume. The model considers ammonium (NH4+), nitrate (NO3-) and dissolved organic N (DON), and includes N immobilization, ammonification and nitrification processes, as well as diffusion in soil-solution. We simulated the dissolution of a fertilizer pellet and a pore scale N cycle at the three different water saturation conditions. To aid interpretation of the model results, microbial activity at a range of N concentrations was quantified experimentally using labelled C to infer microbial activity based on CO2 respiration measurements in bulk soil. The pore-scale model showed that the diffusion and concentration of N in water films is critically dependent upon soil moisture and N species. We predicted that the maximum NH4+ and NO3- concentrations in soil solution around the pellet under low water saturation conditions (15%) are in the order of 1x103 and 1x104 mol m-3 respectively (1-10 M), and under higher water saturation conditions (70%) where on the order of 2x102 and 1x103 mol m-3, respectively (0.1-1 M). Supporting experimental evidence regarding microbial respiration suggests that these concentrations at the pore-scale would be sufficient to reduce microbial activity in the zone immediately around the fertilizer pellet (ranging from 0.9 to 3.8 mm depending on soil moisture status), causing a major loss of soil biological activity by up to 90%. This model demonstrates the importance of pore-scale processes in regulating N movement in soil with special capability to predict the effects of fertilizers on rhizosphere-scale processes and the root microbiome.
Global Fe–O isotope correlation reveals magmatic origin of Kiruna-type apatite-iron-oxide ores
Authors: Troll Valentin R. , Weis Franz , Jonsson Erik , Andersson Ulf Bertil , Madjidi Seyed Afshin , Högdahl Karin , Harris Chris , Millet Marc-Alban , Chinnasamy Sakthi Saravanan , Kooijman Ellen , Nilsson Katarina
Published: March 2020

Kiruna-type apatite-iron-oxide ores are key iron sources for modern industry. The origin of the Kiruna-type apatite-iron-oxide ores remains ambiguous, however, despite a long history of study and a concurrently intense scientific debate. Diverse ore-forming processes have been discussed, comprising low-temperature hydrothermal processes versus a high-temperature origin from magma or magmatic fluids. We present an extensive set of new and combined iron and oxygen isotope data from magnetite of Kiruna-type ores from Sweden, Chile and Iran, and compare them with new global reference data from layered intrusions, active volcanic provinces, and established low-temperature and hydrothermal iron ores. We show that approximately 80% of the magnetite from the investigated Kiruna-type ores exhibit δ56Fe and δ18O ratios that overlap with the volcanic and plutonic reference materials (> 800 °C), whereas ~20%, mainly vein-hosted and disseminated magnetite, match the low-temperature reference samples (≤400 °C). Thus, Kiruna-type ores are dominantly magmatic in origin, but may contain late-stage hydrothermal magnetite populations that can locally overprint primary high-temperature magmatic signatures [1] .

 

[1] Troll, V.R., Weis, F.A., Jonsson, E. et al. Global Fe–O isotope correlation reveals magmatic origin of Kiruna-type apatite-iron-oxide ores. Nature Communications 10, 1712 (2019) doi:10.1038/s41467-019-09244-4
Constraints of multiple detachment layers on structural deformation patterns in the basin: insight from 3D geological structure model in the Puguang area, China
Authors: huang hanyu , he dengfa , zhang weikang
Published: March 2020

Based on outcrop investigations, 3D seismic interpretations, drilling data and results from physical simulation experiment, the structural deformation characteristics of the Puguang area in the Sichuan Basin were studied. Our results show that there are three main detachment layers at different depths in the Puguang area. The lower detachment layer, which is composed of middle Cambrian gypsum-salt rock, controlled the deep structural deformation system (∈2-3-S). The mudstone at the bottom of the Silurian acts as the central detachment layer, separated while influencing both the bottom and the central structural deformation system (S-T1j). The Triassic Jialingjiang Formation gypsum-salt rock forms the upper detachment layer, which mainly controls the shallow structural deformation system (T2l-K). Different structural deformation systems have different degrees of structural deformation and relatively independent deformation styles. The deformation degree of the deep structural deformation system is relatively high, faults of this system cut through the Cambrian to the Silurian strata, forming a series of low amplitude thrust anticline; the central structural deformation system, which is sandwiched by two gypsum-salt rock layers, mainly brittle ductile shear zone, is characterized by high dipping thrust faulted anticlines with relatively larger amplitudes; the deformation degree of the shallow structural deformation system is relatively low, with narrow detachment anticlines and wide synclines developed, while a series of small pop-up structures superimposing on the overlying Jurassic sequences, and asymmetric highs and steep anticlines formed in local areas. Balanced cross section and physical simulation experiments show that the Puguang area suffered from superimposed compressional deformations originated from two directions, northeast and southeast.They represent the compressive stresses transmitted from the Dabashan orogenic belt in the northern margin of the Sichuan Basin and the compressive stresses transmitted from the Xuefengshan orogenic belt in the eastern margin, respectively.In addition, the rheological properties and the thickness of the detachment layer have important influence on the structural style.
Lithosphere deformation due to tearing at STEPs: an analogue model approach
Authors: Broerse Taco , Willingshofer Ernst , Sokoutis Dimitrios , Govers Rob
Published: March 2020

Tearing of the lithosphere at the lateral end of a subduction zone is a consequence of ongoing subduction. The location of active lithospheric tearing is known as a Subduction-Transform-Edge-Propagator (STEP), and the tearing decouples the down going plate and the part of the plate that stays at the surface. STEPs can be found alongside many subduction zones, such as at the south Caribbean or the northern end of the Tonga trench. Here we investigate what controls the evolution and geometry of the lithospheric STEP. Furthermore we study the type of lithosphere deformation in the vicinity of STEPs.

 

We study the ductile tearing in the process of STEP evolution by physical analogue models, which are dynamically driven by the buoyancy of the subducting slab. In our experiments, the lithosphere as well as asthenosphere are viscoelastic media in a free subduction setup. A stress-dependent rheology plays a major role in localization of strain in tearing processes of lithosphere such as slab break-off. Therefore we developed and tested analogue materials that can serve as mechanical analogues for the stress-dependent lithosphere rheology, such as has been inferred by rock laboratory test for dislocation creep of olivine.

 

We show the influence of age and integrated strength of the lithosphere and its contrasts across the passive margin, on the timing, depth, and the degree of localization of the tearing process. When tearing of the lithosphere is dominated by ductile deformation, we find that gradual necking of the passive margin precedes tearing. In many of our models we find that tearing at the lateral ends of the subduction zones is resisted by the lithospheric strength, such that tearing is delayed with respect to rollback of the slab. This has consequences for the shape of the subduction zone, and for the separation between the subducted slab and the surface lithosphere. We study the type of deformation in the vicinity of the STEP of the lithosphere that stays at the surface, and relate this to deformation observed beside STEP fault zones along the Hellenic slab, the Lesser Antilles slab, and the New Hebrides slab. 
Turbulent cascade in the solar wind on ion scales
Authors: Hellinger Petr , Verdini Andrea , Landi Simone , Franci Luca , Papini Emanuele , Matteini Lorenzo
Published: March 2020

Magnetic power spectra in the solar wind typically exhibit a transition, steepening, on characteristic ion scales. This transition is not yet fully understood. Two basic phenomena are usually suspected: Hall physics and dissipation. We investigate properties of this transition using numerical simulations.  We analyze results of two-dimensional hybrid simulations using a compressible version of von Kármán-Howarth equation for statistically homogeneous Hall MHD turbulence and compare these results to the predictions for the incompressible Hall MHD. The simulation results indicate that the transition between large, MHD and sub-ion scales is related to a combination of the Hall effect and ion heating/energization.
Reconstructing the evolution of ice sheets, sea level and atmospheric CO2 during the past 3.6 million years
Authors: Berends Tijn , de Boer Bas , van de Wal Roderik
Published: March 2020

Understanding the evolution of, and the interactions between, ice sheets and the global climate over geological time is important for being able to constrain earth system sensitivity. However, direct observational evidence of past CO2 concentrations only exists for the past 800,000 years. Records of benthic d18O date back millions of years, but contain signals from both land ice volume and ocean temperature. In recent years, inverse forward modelling has been developed as a method to disentangle these two signals, resulting in mutually consistent reconstructions of ice volume, temperature and CO2. We use this approach to force a hybrid ice-sheet – climate model with a benthic d18O stack, reconstructing the evolution of the ice sheets, global mean sea-level and atmospheric CO2 during the late Pliocene and the Pleistocene, from 3.6 Myr ago to the present day. The resulting reconstructions of CO2 and sea level agree well with the ice core record and different sea-level proxies, indicating that this model set-up yields useful information for colder-than-present climates. For the warmer-than-present climates of the Late Pliocene, different proxies for both CO2 and sea level are contradictory, making model validation difficult. During the early Pleistocene, 2.6 – 1.2 Myr ago, we simulate 40 kyr glacial cycles with CO2 ranging between 270 – 280 ppmv during interglacials and 210 – 240 ppmv during glacial maxima. After the Mid-Pleistocene Transition (MPT), when the glacial cycles change from 40 kyr to 80/120 kyr cyclicity, these values change to 260 to 280 ppmv during interglacials, and 180 – 200 ppmv during glacial maxima.
Probability estimation of a Carrington-like geomagnetic storm
Authors: Serra Isabel , Moriña David , Puig Pere , Corral Álvaro
Published: March 2020

Intense geomagnetic storms can cause severe damage to electrical systems and communications. this work proposes a counting process with Weibull inter-occurrence times in order to estimate the probability of extreme geomagnetic events. It is found that the scale parameter of the inter-occurrence time distribution grows exponentially with the absolute value of the intensity threshold defining the storm, whereas the shape parameter keeps rather constant. The model is able to forecast the probability of occurrence of an event for a given intensity threshold; in particular, the probability of occurrence on the next decade of an extreme event of a magnitude comparable or larger than the well-known Carrington event of 1859 is explored, and estimated to be between 0.46% and 1.88% (with a 95% confidence), a much lower value than those reported in the existing literature.
Global analysis of mountain forest distribution and change during 2000 to 2018
Authors: He Xinyue , Spracklen Dominick , Holden Joseph , Zeng Zhenzhong
Published: March 2020

Mountain forests cover a small fraction of the Earth’s surface, but may exert important influence on the hydrological cycles of river basins (e.g., evapotranspiration, river flow). Many montane ecosystems are currently experiencing forest loss or gain, due to direct land-use change and due to changes in climate. Previous studies revealed most deforestation and afforestation occur in the lowlands, while how forest cover changes at different altitudes in the mountains has not been fully understood. Here we present a study that aims to better understand the distribution of mountain forest change. We use a high-resolution global map of forest change during 2000-2018 combined with elevation data to complete a global analysis of the relationship of elevation with tree cover and tree cover loss and gain. We also assess which climate variables (temperature, rainfall, wind speed) might explain observed variations in tree cover. Our analysis provides new information on how and why mountain forests are changing.