bluuebunny/crossref_metadata_2025 huggingface dataset:
Geological controls on the morphology of an overdeepened canyon investigated by seismic surface waves (Lower Aare Valley, Switzerland)
Authors: Gegg Lukas , Keller Lorenz , Buechi Marius W. , Spillmann Thomas , Deplazes Gaudenz , Madritsch Herfried , Anselmetti Flavio S.
Published: March 2020

Subglacial overdeepenings are common features of past and presently glaciated landscapes. In the Northern Alpine Foreland, these troughs occur mostly within the rather soft, poorly lithified sandstones of the Molasse basin. An exceptional setting is the Lower Aare Valley in Northern Switzerland, where a narrow, finger-like overdeepening (Gebenstorf-Stilli Trough) has been incised more than 100 m below the present surface into the fold-and-thrust belt of the Jura Mountains with its diverse Mesozoic lithologies including competent limestone units. Consequently, the morphology of this overdeepening can provide valuable information on lithological and structural controls on subglacial overdeepening erosion.

We investigate the Gebenstorf-Stilli Trough with three scientific boreholes located along the South-North oriented trough axis. In addition, a set of seismic cross-sections has been acquired by a combination of active and passive seismic approaches analysing surface waves, namely passive horizontal-to-vertical spectral ratio (HVSR) measurements, active measurements applying multiple filter analysis of group velocity (MFA), and extended spatial auto correlation of ambient vibration array data (ESAC).

Preliminary results show that the base of the overdeepening can be well imaged using our methodology. In combination with borehole information, surface elevation data and 3D models of the subsurface geology, we see great potential to better constrain the morphology of the Gebenstorf-Stilli Trough, and to assess how different bedrock lithologies and structures influence subglacial overdeepening erosion – an underexplored and poorly understood issue.
Machine-learning inference of the interior structure of low-mass exoplanets
Authors: Baumeister Philipp , Padovan Sebastiano , Tosi Nicola , Montavon Grégoire , Nettelmann Nadine , MacKenzie Jasmine , Godolt Mareike
Published: March 2020

We explore the application of machine-learning, based on mixture density neural networks (MDNs), to the interior characterization of low-mass exoplanets up to 25 Earth masses constrained by mass, radius, and fluid Love number k2. MDNs are a special subset of neural networks, able to predict the parameters of a Gaussian mixture distribution instead of single output values, which enables them to learn and approximate probability distributions. With a dataset of 900,000 synthetic planets, consisting of an iron-rich core, a silicate mantle, a high-pressure ice shell, and a gaseous H/He envelope, we train an MDN using planetary mass and radius as inputs to the network. We show that the MDN is able to infer the distribution of possible thicknesses of each planetary layer from mass and radius of the planet. This approach obviates the time-consuming task of calculating such distributions with a dedicated set of forward models for each individual planet.

The fluid Love number k2 bears constraints on the mass distribution in the planets' interior and will be measured for an increasing number of exoplanets in the future. Adding k2 as an input to the MDN significantly decreases the degeneracy of possible interior structures.
Changes in the Past and Projected Western North Pacific Tropical Cyclone Activity in a Warmed Climate
Authors: Wu Liang
Published: March 2020

Two high-resolution climate models (the HiRAM and MRI-AGCM3.2) are used to simulate present-day western North Pacific (WNP) tropical cyclone (TC) activity and investigate the projected changes for the late 21st century. Compared toobservations, the models are able to realistically simulate many basic features of the WNP TC activity climatology. Future projections with the coupled model inter-comparison project phase 5 (CMIP5) under Representative Concentration Pathway (RCP) 8.5 scenario show a tendency for decreases in the number of WNP TCs, and of increases in the more intense TCs. It is unknown to what cause this inverse variation with number and intensity should be generally linked to similar large-scale environmental conditions. To examine the WNP TC genesis and intensity with environmental variables, we show that most of the current trend of decreasing genesis of TCs can be attributed to weakened dynamic environments and the current trend of increasing intensity of TCs might be linked to increased thermodynamic environments. Thus, the future climate warms under RCP 8.5 will likely lead to strong reductions in TC genesis frequency over the WNP, with project decreases of 36-63% by the end of the twenty-first century, but lead to greater TC intensities with rapid development of thermodynamic environments.
Measuring Spatial and Temporal Patterns of Urban NO2 Concentrations by combining mobile and stationary DOAS instruments
Authors: Wenig Mark , Zhu Ying , Ye Sheng , Chan Ka Lok , Chen Jia , Dietrich Florian , Bi Xiao , Kuhlmann Gerrit
Published: March 2020

In many cities around the world the NO2 concentration levels exceed WHO guideline limits. Urban air quality is typically monitored using a relatively small number or monitoring stations that follow certain guidelines in terms of inlet height and location relative to streets. However, the question remains how a limited number of point measurements can represent the city-wide air quality and capture spatial patterns. Measurement campaigns in Hong Kong and Munich were conducted, using a combination of mobile in-situ and stationary remote sensing differential optical absorption spectroscopy (DOAS) instruments. In order to separate spatial and temporal patterns, we developed an algorithm based on a combination of mobile and stationary data sets that corrects for the diurnal cycle in the mobile measurements.  We constructed pollution maps from the corrected measurements that represent daily average NO2 exposure. The maps have been used to identify pollution hot spots, determine the spatial dependency of long-term changes, and capture the weekly cycles of on-road NO2 levels in Hong Kong and Munich. Since our method can also be used to determine the spatial representativeness of the monitoring stations in cities, it is very valuable tool for identifying suitable locations for air quality monitoring stations.
Plasmaspheric electron density estimation based on COMISC/FORMOSAT-3 data
Authors: Prol Fabricio , Hoque Mainul
Published: March 2020

The plasmasphere is a region of continuous study due to some open questions related to the plasmaspheric internal dynamics, boundaries, and coupling processes with the magnetosphere and ionosphere, in particular during space weather events. Given such interests, the results of a new tomographic method to estimate the plasmaspheric electron density will be presented. The tomographic reconstruction is applied using measurements of Total Electron Content (TEC) from the Global Positioning System (GPS) receivers aboard the Constellation Observing System for Meteorology, Ionosphere, and Climate / Formosa Satellite Mission 3 (COSMIC/FORMOSAT-3). Despite relevant challenges imposed by the orbital geometry to obtain stable electron density reconstructions of a large area such as the plasmasphere, the developed approach was capable of representing the natural variability of the plasma ambient in terms of geographic/geomagnetic latitude, altitude, solar activity, season, and local time. The quality assessment was carried out using two years of in-situ electron density measurements from spacecraft deployed by the Defense Meteorological Satellite Program (DMSP). Our investigation revealed that improvements over 20% can be achieved for electron density specification by TEC data assimilation into background ionization.
A new perspective on studying ENSO teleconnections
Authors: Herein Matyas , Haszpra Timea , Bodai Tamas
Published: March 2020

Traditionally we think that climate is a long term average of weather. It is true but only if the climate is stationary. However, in a changing climate, where one or more relevant system parameters are changing in time, there can be no stationarity by definition, whereas stationarity is crucial for the applicability of any temporal averaging techniques. To avoid this problem we redefine climate as the distribution of potential climate realizations characterized by the instantaneous statistics of an ensemble using the so-called snapshot attractor view. In this view, the relevant quantities of the climate system are the statistics taken over an ensemble of possible realizations evolved from various initial conditions. To illustrate the power and applicability of this method we investigate the changes in the El Niño–Southern Oscillation (ENSO) phenomenon and its precipitation-related teleconnections over the Globe under climate change in the Community Earth System Model’s Large Ensemble from 1950 to2100. For the investigation, a recently developed ensemble-based method, the snapshot empirical orthogonal function (SEOF) analysis is used. The instantaneous seasonal ENSO SST pattern is defined as the leading mode of the SEOF analysis carried out at a given time instant over the ensemble. The corresponding principal components (PC1s) characterize the ENSO phases. Considering regression maps, we find that the largest changes in the typical amplitude of SST fluctuations occur in the June–July–August–September (JJAS) season, in the Niño3–Niño3.4 region and in the western part of the Pacific Ocean. At the same time, the increase is also considerable along the Equator in December–January–February (DJF). The Niño3 amplitude shows also an increase of about 20% and 10% in JJAS and DJF, respectively. The strength of the precipitation-related teleconnections of the ENSO is found to be non-stationary, as well. For example, the anti-correlation with precipitation in Australia in JJAS and the positive correlation in Central and North Africa in DJF are predicted to be more pronounced by the end of the 21th century. Half-year-lagged correlations, aiming to predict precipitation conditions from ENSO phases, are also studied. The Australian, Indonesian precipitation and that of the eastern part of Africa in both JJAS and DJF seem to be well predictable based on ENSO phase, while the South Indian precipitation is in relation with the half-year previous ENSO phase only in DJF. The strength of these connections increases with time, especially from the African region to the Arabian Peninsula.
Mass wasting at the Siberian termination of Lomonosov Ridge, Arctic Ocean
Authors: Schlager Ursula , Jokat Wilfried , Weigelt Estella
Published: March 2020

The Lomonosov Ridge is an 1800 km long continental sliver in the center of the Arctic Ocean. Beside its tectonic relevance it hosts glaciogenic features caused either by deep reaching icebergs or grounded ice sheets as well as indications for mass wastings. Systematic swath bathymetry acquired in 2014 provided an almost complete image of these shallow disturbances from almost 84˚ N to the foot of the Laptev margin.

Several arcuate transverse features are present on both sides of the crest of the eastern part of Lomonosov Ridge between 81˚ and 84˚ N. Eight of them are 2.1-10.2 km wide, 1.7-8.2 km long, 125-851 m deep, with height of headwall between 58-207 m and a slid mass volume of 0.09-7.58 km3. Due to the absence of scientific drill holes only a tentative seismic stratigraphy can be used for a rough age estimate of the mass wasting. All but one show a glide plane on top of a pronounced stratigraphic seismic horizon with strong seismic amplitudes. We will introduce the different geometries and statistics of these mass wasting features.
Seismic deformation in the Western Alps : new insights from high resolution seismotectonic analysis
Authors: Mathey Marguerite , Sue Christian , Potin Bertrand , Pagani Colin , Bodin Thomas , Husson Laurent , Hannouz Estelle , Baize Stéphane , Walpersdorf Andrea
Published: March 2020

In the Western Alpine arc, GNSS measurements indicate that the far field convergence responsible for the Oligo-Miocene continental collision is now over. However, seismicity and slow deformation are still active. Former collisional tectonic features, such as the Penninic Front, are nowadays reactivated as normal faults. Indeed, geodetic and seismotectonic studies show that the inner part of the chain is undergoing transtensional deformation, although local compression is observed in the foothills at the periphery of the arc. Due to the low to moderate seismicity of the Western Alps, the stress and strain fields remain partly elusive.

The aim of the present study is to quantitatively assess the current seismic stress and strain fields within the Western Alps, from a probabilistic standpoint. We used a new set of more than 30,000 Alpine earthquakes recorded by the dense local Sismalp seismic network since 1989. We first computed well-constrained focal mechanisms (f.m.) for more than 2,000 events with Ml ranging from 0.5 to 4.9 based on first motion (P-wave) polarity. This is the first time that such a huge focal mechanism dataset can be analyzed in the Alps. Corresponding events have been localized using a 3D velocity model (B. Potin, 2016). The global distribution of P and T axes dips confirms a vast majority of dextral transtensive focal mechanisms in the overall Alpine realm. We interpolated these results based on a Bayesian interpolation method, providing a probabilistic 2D map of the styles of seismic deformation in the Western Alps. Compression is robustly retrieved only in the Pô plain where seismicity depth differs from the shallow seismicity of the Western Alps. Extension is localized at the center of the belt. Importantly, extension is clustered instead of continuous along the belt. We then summed seismic moment tensors in homogeneous volumes of crust, to obtain seismic strain rates directly comparable to geodetic ones. Last, we inverted f.m. together in specific areas to obtain principal stress directions. A major outcome is the orientation of the extension, which is surprisingly oblique to the arc, rather than normal, as commonly thought.

These results bring new insights on the geodynamic processes driving the seismotectonic activity of the Western Alps, such as the relative contributions of crustal tectonics and deep processes.
Classification of volcanic and tectonic earthquakes in Kamchatka (Russia) with different machine learning techniques
Authors: Galina Natalia , Shapiro Nikolai , Seydoux Leonard , Droznin Dmitry
Published: March 2020

Kamchatka is an active subduction zone that exhibits intense seismic and volcanic activities. As a consequence, tectonic and volcanic earthquakes are often nearly simultaneously recorded at the same station. In this work, we consider seismograms recorded between December 2018 and April 2019. During this time period when the M=7.3 earthquake followed by an aftershock sequence occurred nearly simultaneously with a strong eruption of Shiveluch volcano. As a result, stations of the Kamchatka seismic monitoring network recorded up to several hundreds of earthquakes per day. In total, we detected almost 7000 events of different origin using a simple automatic detection algorithm based on signal envelope amplitudes. Then, for each detection different features have been extracted. We started from simple signal parameters (amplitude, duration, peak frequency, etc.), unsmoothed and smoothed spectra and finally used a multi-dimensional signal decomposition (scattering coefficients). For events classification both unsupervised (K-means, agglomerative clustering) and supervised (Support Vector Classification, Random Forest) classic machine learning techniques were performed on all types of extracted features. Obtained results are quite stable and do not vary significantly depending on features and method choice. As a result, the machine learning approaches allow us to clearly separate tectonic subduction-zone earthquakes and those associated with the Shiveluch volcano eruptions based on data of a single station.
Exploring the Evolution and Source Properties of Injection-Induced Seismicity in Northern Oklahoma Using a Large-N Seismic Array
Authors: Kemna Kilian B. , Wickham-Piotrowski Alexander , Peña-Castro Andrés F. , Cochran Elizabeth S. , Harrington Rebecca M.
Published: March 2020

The LArge-n Seismic Survey in Oklahoma (LASSO) array recorded local seismicity in 2016 in a region of active saltwater disposal. The month-long deployment of 1,833 vertical-component nodes had a nominal station spacing of 400 m and covered a 25 by 32 km2 area. We estimate local event magnitudes and focal mechanisms of the induced seismicity using the vertical component waveforms from a catalog of 1375 earthquakes. Here we use the developed catalog to investigate the spatio-temporal evolution of seismicity and the source properties of the induced events.

The catalog is complete to a local magnitude of ~0.9, with a b-value of ~1.1. Focal mechanisms, which we determined using the HASH method, show a mix of strike-slip and normal faulting. The majority of the events are located at 1.5 – 5.0 km depth, where injection depths range from 0.1 – 2.0 km, and the basement contact is located at 1.5 – 2.5 km. Analysis of the coefficient of variation of interevent times suggests that the time evolution of seismicity is close to Poissonian, with minimal temporal clustering. We observe spatial clustering, with larger (M > 2) events occurring within dense clusters near the footprint of the array.

The dense station coverage of the array permits the exploration of variations in corner frequency and resulting stress drop estimates as a function of azimuth, i.e. radiation pattern. We calculate stress drops for the local catalog within 5 km of the array footprint from individual spectral and spectral ratio corner frequency values. Single spectra corner frequency estimates for events within the array footprint on individual nodes show evidence of variation related to radiation pattern, and vary as much as 100% from the mean for an individual event. Stress drop estimates from spectral ratio corner frequency estimations range between 10 – 100 MPa, show self-similar scaling, and fall within the typical range observed for intraplate (tectonic) earthquakes. Both single spectra and spectral ratio corner frequency estimates show a significant sample bias in the corner frequency estimation by using less than ~10 stations, and highlight the importance of azimuthal coverage for the stability of spectral estimates.
Viscous relaxation of mineral Inclusions and its implications for reaction overstepping calculations in metamorphic rocks
Authors: Moulas Evangelos , Zhong Xin , Tajcmanova Lucie
Published: March 2020

Over the recent years, Raman elastic barometry has been developed as an additional method to calculate metamorphic conditions in natural systems. A major advantage of Raman elastic barometry is that it does not depend on thermodynamic databases and classic geobarometry methods but relies on mechanical calculations. As a consequence, Raman elastic barometry offers an independent method for estimating the pressure conditions that prevailed at the time of entrapment of minerals during growth of their hosts.

The difference between the pressure calculated using elastic geobarometry and that calculated by phase equilibria methods has recently been employed to estimate the extent of metamorphic reaction overstepping in natural systems. Quantification of the latter however implicitly assumes that the rheology of the inclusion-host system is perfectly elastic. This assumption may not hold at high temperatures, where viscous creep of minerals takes place.

The amount of viscous relaxation of a host-inclusion system is a path-dependent quantity which mostly depends on the temperature-time (T-t) path followed. Here, we present examples of visco-elastic relaxation of mineral inclusions and calculate the apparent reaction overstepping which results by assuming that the mechanical system is purely elastic. Our modelling shows that host-inclusion systems that experienced large peak temperatures for long periods of time will retain inclusion residual pressures that cannot be simply related to the growth of their hosts and should therefore not be used for reaction overstepping calculations.
New insights into concurrent air-sea heat flux forcing of Subantarctic Mode Water formation from mooring observations in the Southeast Indian and Southeast Pacific sectors of the Southern Ocean
Authors: Josey Simon , Tamsitt Veronica , Cerovecki Ivana , Gille Sarah , Schulz Eric
Published: March 2020

Wintertime surface ocean heat loss is the key driver of Subantarctic Mode Water (SAMW) formation. However, until now there have been very few direct observations of fluxes, particularly during winter. Here, we present results from the first concurrent (2015-17 with gaps), air-sea flux mooring deployments in two key SAMW formation regions: the Southern Ocean Flux Site (SOFS) in the Southeast Indian sector and the Ocean Observatories Initiative (OOI) mooring in the Southeast Pacific sector. Gridded Argo and ERA5 reanalysis provide temporal and spatial context for the mooring observations. Turbulent ocean heat loss is found to be on average 1.5 times larger at the Southeast Indian than Southeast Pacific sites with stronger extreme heat flux events in the Southeast Indian leading to larger cumulative winter heat loss. For the first time, we show that turbulent heat loss events in the Southeast Indian sector occur in two atmospheric regimes (a direct cold air pathway from the south and an indirect pathway circulating dry Antarctic air via the north). In contrast, heat loss events in the Southeast Pacific sector occur in a single atmospheric regime (cold air from the south). On interannual timescales, wintertime anomalies in net heat flux and mixed layer depth (MLD) are often correlated at the two sites, particularly when wintertime MLDs are anomalously deep. Using ERA5, we show that this is part of a larger zonal dipole in heat flux and MLD anomalies present in both the Indian and Pacific SAMW formation regions, associated with anomalous meridional atmospheric circulation. These recent results will be placed in the context of multidecadal variability in the SAMW formation region dominant heat flux patterns over the past 40 years over all 3 sectors of the Southern Ocean (Pacific, Indian and Atlantic).
Bank Erosion Processes, Trends and Impacts in a Hypertidal Estuarine System
Authors: Gasparotto Andrea , Leyland Julian , Darby Stephen , Carling Paul
Published: March 2020

Estuarine systems represent the dynamic transition zone between fluvial and marine systems and as such they are sensitive to changes in both domains resulting from impacts of climate change and human activities related to coastal and water-flow management especially in densely inhabited areas. Further, these tidally influenced systems are subject to a unique set of driving conditions linked to bidirectional flow processes. The potential growing risks of shoreline erosion in coastal, estuarine and inter-tidal environments have been identified by a number of studies in recent years. However, bank erosion processes in tidal settings remain poorly understood, especially when compared to the large volume of research concerning fluvial bank erosion. In general, the well-established fluvial bank erosion literature suggests that bankline erosion involves two main sets of processes: hydraulic erosion and gravitational collapse. Given the additional complexity of the process mechanics involved in tidal settings, arising mainly from the presence of bi-directional flows, process insights gained from studies of fluvial bank erosion might not be appropriately applied in a tidal context.

The present study aims to improve our understanding of estuarine bank mobility dynamics through investigation of the evolution and rates of bank retreat/accretion acting in the Severn Estuary (UK). The Severn Estuary has one of the highest semidiurnal tidal ranges in the world (about 15 m in the outer estuary, up to 8-9 m in the middle parts of the system, and 2 to 3 m in the inner river-dominated sector). Here we estimate bank mobility throughout the estuary from the river-dominated to the tidal-dominated zones during the last 119 years, via analysis of historical maps and recent satellite images. We use the findings from this analysis coupled with recent data collection to propose an empirical model of bank mobility throughout the entire estuary, highlighting the characteristics and the differences between riverine and coastal erosive processes. The model indicates that (i) the highest bank mobility (both in term of erosion and deposition) is located in the mid part of the estuary, close to the bedload convergence zone (BLZ), with other ‘hot spots’ of change linked to major anthropogenic disturbances either in the outer and inner estuary, and (ii) that the erosive mechanics associated to severe lateral land losses in the estuary are mainly driven by impulses in energy delivery to the bank surface in occasion of very high tidal oscillations (particularly in spring overbank tides) and severe storms triggering mass wasting in form of toppling and rotational failures.  
Stable Carbon Isotope Ratios in Atmospheric VOC during the EMeRGe-EU and ASIA campaigns
Authors: Krebsbach Marc , Koppmann Ralf
Published: March 2020

VOC (volatile organic compounds) play a critical role in the chemistry of the atmosphere. The formation of many important secondary pollutants in the atmosphere, such as ozone, peroxides, aldehydes, and peroxyacyl nitrates and secondary organic particulate matter depends critically on the availability of VOC as their precursors. Many of them have strong direct adverse effects on our environment. The assessment of the impact of VOC on the atmosphere can be significantly improved by measuring their stable carbon isotope ratios. The isotopic composition of compounds emitted by natural or anthropogenic activities vary for emissions from different sources. In almost all atmospheric processes, e.g. chemical reactions, photolytic processes, transport and dilution, diffusion, and phase transitions, the isotopic ratio in VOC is altered. Studying the isotope ratios of both precursors and products makes it possible to distinguish between freshly emitted VOC and photochemically processed compounds, to increase our knowledge of transport versus chemistry, to study the ultimate fate of oxidation products, and to help assess the impact of emissions, e.g. from large population centres (MPCs), on local, regional and even global pollution.
The automated high volume air sampling system MIRAH has been deployed during several missions with the German High Altitude – Long-range research aircraft (HALO). Here we focus on the campaigns EMeRGe-EU and -ASIA (Effect of Megacities on the transport and transformation of pollutants on the Regional and Global scales). The objectives were to measure the pollution emitted, transported and transformed from the MPCs London, BeNeLux, Rhine-Ruhr and Po Valley for the European Part. The second part of EMeRGe was conducted from Taiwan with the goal to investigate the pollution outflow from Asian MPCs such as Taipei, Hongkong, Shanghai, Beijing, Manila, Seoul and Tokio. In both parts a key experiment was the identification of the source of the air masses by collecting whole air samples on ground prior and during particular flights in specific metropolitan regions. On 7 flights in Europe and 12 flights in Asia, mostly below 6 km altitude, more than 140 air samples were collected on HALO during each campaign, and additional 46 samples at specific ground sides. The whole air samples were analysed for mixing ratios and stable carbon isotope ratios of selected aldehydes, ketones, alcohols, and aromatics. This allowed investigating air masses of different origin, characteristic, and atmospheric processing. In this presentation we will give an overview of the data and show exemplary results.

This work was supported by the German Research Foundation (Deutsche Forschungsgemeinschaft, DFG Priority Program SPP 1294) under grant-No. KR3861/1-1.
Characteristics of turbulence in transition regions near large-scale boundaries in the solar wind.
Authors: Riazantseva Maria , Rakhmanova Liudmila , Zastenker Georgy , Yermolaev Yuri , Lodkina Irina , Safrankova Jana , Nemecek Zdenek , Prech Lubomir
Published: March 2020

Fluctuations of solar wind parameters can be strongly affected by the presence of sharp boundaries between different large-scale structures. Turbulence cannot develop freely across such boundaries, just as it could in the undisturbed solar wind. It can lead the growing of fluctuation level and changes in shape and properties of turbulent cascade too. The compression regions, for example  Sheath regions before magnetic clouds, and CIR regions (the compression areas between fast solar wind from coronal holes and slow solar wind  from coronal streamers), are  typical examples of such transitions.  Here we present the analysis of turbulence spectrum changes during crossings of  Sheath and CIR regions. We use unique high time resolution plasma measurements by BMSW instrument at Spektr-R spacecraft in order to consider both MHD and kinetic scales of turbulent cascade.  We analyze the base properties of  turbulence spectra: spectral power and slopes at corresponding scales, break frequency between scales, and also shape of spectra. We began by examining of the case study crossings of the transition regions and then compared statistically the spectral properties in such regions with the same ones in the undisturbed solar wind. We have shown that spectra fall nonlinearly at kinetic scales and become steeper with growing of fluctuation level in transition regions, at the same time the slope of spectra at MHD scale remains almost Kolmogorov. Withal some interesting features can be observed in the vicinity of the break between characteristic scales during crossing of transition regions. The given results reveal the lack of energy balance between MHD and kinetic scales, and can indicate the intensification of dissipation processes and the additional plasma heating in the  transition regions. The work is supported by Russian Science Foundation grant 16-12-10062.
Reservoir impoundment, hydro-mechanical changes, and increased seismicity near the Xiluodu hydropower dam, Southwestern China
Authors: Zhang Man , Ge Shemin , Yang Qiang , Ma Xiaodong
Published: March 2020

Xiluodu is currently the third largest hydropower station in the world and situates on the upper Yangtze River in Southwestern China. The 285.5 m-high dam lies in the center of a relatively intact and stable tectonic block, triangulated by three large fault zones. The seismicity in the region increased markedly since the reservoir was first impounded in 2013. Previous studies suggest a strong spatial-temporal link between the seismicity and reservoir impoundment. This study attempts at conducting a quantitative analysis integrating the geological and engineering data to constrain the link between the impoundment and the seismicity, which could inform the future seismic evolution in the area.

We first study the characters of the spatial activity of earthquakes in different periods to address the correlation between increased seismicity and reservoir impoundment. Since the impoundment, the earthquakes in this region can be plausibly separated spatially into two groups. The first group (including a ML5.4 and a ML5.5 event) is located within ~10km of reservoir, where a major fault zone is absent. Within this spatial range,  earthquakes > ML 2.0 are rare three years prior to the impoundment, but more than 1000 events were detected between the initial impoundment in 2013  and September 2014 when the reservoir reached its peak level. Thereafter, the fluctuations of water level were accompanied by continuous seismicity, albeit at a considerably lower rate. The seismicity in this region is strengthened again in 2019. The other group of earthquakes are clustered with several mapped major fault traces. Some of these events quickly followed the water level fluctuation, while some were observed after significant delays. In general, the distances between locations of delayed events and the reservoir gradually increase with time. 

To address the influence of impoundment on seismicity, we analyzed the hydrologic and mechanical effects of the impoundment, i.e., the fluid pressure diffusion and the reservoir loading. We computed the spatiotemporal changes of Coulomb stress on known faults resulting from these two effects. The sensitivity analysis of hydraulic and mechanical parameters shows that the changes of Coulomb stress in the area could increase to a level that is relevant to reactivation of faults. While the relationship between the impoundment and increase seismicity warrants further analysis, we hope to inform the regional seismic impact by integrating in-situ stress state, fault geometries, and the coupled hydro-mechanical stress changes.
Direct dating of marine sediments using optically stimulated luminescence techniques: Insights from ODP cores 658B and 659A.
Authors: Armitage Simon , Sahy Diana , Tindall Joanna , Pinder Robyn
Published: March 2020

Chronologies for marine sediments are usually constructed by tuning marine proxies for global ice volume (δ18O) to the well understood variations in the Earth's orbit, by the identification of event horizons (e.g. tephra or biostratigraphic markers) and/or by radiocarbon dating. However, these techniques are not universally applicable. Optically stimulated luminescence dating (OSL) is potentially widely applicable to marine cores and may offer significant advantages over more conventional chronometric techniques. However, methodological considerations regarding the application of OSL techniques have yet to be systematically explored. Using material from Ocean Drilling Program (ODP) cores 658B and 659A, we assess the applicability of OSL dating to deep ocean sediments. For these cores, severe uranium-series disequilibrium is found, but the cause and character of this disequilibrium is spatially and temporally variable. Uranium-series disequilibrium causes the environmental dose rate to vary over time, and an iterative dose rate calculation is required to generate accurate ages. For the last glacial-interglacial cycle, these calculations yield OSL ages which are in good agreement with independent age estimates, suggesting that the application of luminescence dating techniques to deep-sea sediments merits further investigation.
Changes in ecological networks and eco-environmental effects on urban ecosystem in China’s three typical urban agglomerations
Authors: Fang Ying , Wang Jing , Liu Jingjing , Li Zehui
Published: March 2020

Rapid urbanization caused a massive loss of natural habitats and seriously changed urban natural ecosystems. Ecological network, a spatial concept of ecosystems, maps the most valuable areas that provide multiple ecological goods and services for human demands. Ecological network has long been adopted worldwide for improving urban ecological environment under the scenarios of rapid urbanization. However, Little researches focused on changes in ecological networks and their effects on urban ecosystem. It is important to investigate the trends in ecological network changes, clear its relationship with human activities and policies for guiding sustainable economic and social development. The study aimed to analyze the relationship between the changes in ecological networks and human activities, regional policies as well as environmental changes, and to establish new ecological networks that meet the human demands of ecosystem services, in China’s three typical urban agglomerations, including Beijing-Tianjin-Hebei (BTH), Yangtze River Delta (YRD), and Pearl River Delta (PRD) from 2000 to 2015.This study used the variation of habitat quality index, ecosystem carbon stock, PM2.5 and supply-demand of ecosystem services to measure the eco-environmental effects of ecological network changes under complex physical and socio-economic circumstances. Meanwhile, it established the new ecological networks based on the human-being demand of ecosystem services calculated by real-time population distribution, accessibility, and land development index, trying to optimize the land spatial patterns and ecosystem management in urban agglomerations. The results showed that a lot of areas of ecological networks had vanished into dryland, urban land and other developed land from 2000 to 2015, resulting from urban expansion, industrial development and regional land policies. The degradation in ecological networks caused a significant increase of PM2.5 and decrease of habitat quality index and ecosystem carbon stock. And the spatial imbalance in the supply-demand of ecosystem services was shrinking to varying degrees, due to different regional ecological protection policies. There were regional spatial differences in the establishment of new ecological networks. However, the closer to central cities of each agglomerations, the human demands of ecosystem services and the need of strengthening the preservation ecosystems were more critical. This study contributes to the identifying the role of human activities on ecological processes and provides a scientific reference for the use of ecological network as the basis of the regional development plans. It is necessary to relieve the dilemma between the urban growth and ecosystem protection.
Parameterization of multidimensional process-based tree-ring models: Why it is important?
Authors: Shishov Vladimir , Il'in Victor , Tychkov Ivan , Popkova Margarita , Belousova Daria
Published: March 2020

Improvement of our understanding of tree-growth processes and accurate interpretations of climatic signals in tree rings have recently become possible through the application of process-based models, e.g., Biome3, MAIDEN,  ASTANEA, CAMBIUM, PRYSM, VS-lite and others, which simulate tree growth based on non-linear effects of environmental conditions. The process-based Vaganov–Shashkin model (VS-model) is one such model which describes tree-ring formation as a result of multivariate affects of local climate (temperature, soil moisture and solar irradiance). As with most of the process-based models, the VS-model is a complex tool that requires a considerable number of model parameters that should be reasonably estimated for each forest stand. This leads to problem of accurate model parameterization, namely estimations of optimal values of the model parameters necessary to guarantee: (1) the best fit to the observed tree-ring measurements; (2) identification of the specific seasonal cell production and enlargement; (3) reasonable ecological interpretation in terms of processes involved in the model.

Based on differential evolution (DE) approach adopted to the model parameterization using the supercomputer facilities it was shown:

(1) a significant spatial variability of adjusted VS-parameter values (with corresponded ecological interpretation) that provide the best fit to the actual tree-ring chronologies from climatically contrasted sites distributed in the vast territories of Eurasia and as a result, the models ability to capture a significant diversity in non-linear tree-ring growth responses that are climatically induced,

(2) the high sensitivity of the models even for forest stands where mixed climatic signal affects on tree-ring growth during growing season,

(3) the high probability to obtain a "correct" model parameterization which explains up to 60% tree-ring variance by the climate forcing even for randomly generated "chronologies"  in case of incorrect usage of the calibration-verification strategy for multidimensional models.
Water Shedding Properties of Oil Impregnated Hydrophobic Soils
Authors: McCerery Rebecca , Woodward John , McHale Glen , Winter Kate
Published: March 2020

Hydrophobic soils and sediments have gained significant interest in soil science due to negatively influencing biomass production and as drivers of landslides and enhanced erosion. Whilst natural and fire-induced soil water repellency have been studied, little work has considered how the sediment-water interaction with naturally occurring hydrophobic sediments might change in the presence of oil. Recent advances in materials physics have shown bio-inspired slippery liquid infused porous surfaces (SLIPS) and lubricant impregnated surfaces (LIS) can produce super slippery surfaces with excellent water shedding properties. Here we apply this new understanding to the physics of soil water repellency and address how the presence of oil, whether from contamination or otherwise, might influence water infiltration. We hypothesise that oil impregnating a hydrophobic soil may create stable oil coatings and/or layers that create soil surfaces resistant to water infiltration and with enhanced run-off of water. Using monolayers of sand, silt and clay particles treated with a commercial hydrophobising agent and silicone oil, we created model (oil-free) hydrophobic and oil impregnated hydrophobic soils. Static water contact angles and droplet sliding angles were used to classify their degree of hydrophobicity and ability to shed water. Our results show that in the absence of oil, model hydrophobic soil surfaces with particle sizes below 63μm are superhydrophobic with water droplet contact angles above 150 degrees. In the presence of oil, we observed a sediment-based SLIP/LI surface on particle sizes below 63μm with water contact angles of 90 degrees and droplet sliding angles of below 5 degrees. We also achieved reduced sliding angles compared to the oil-free surfaces, and a conformal layer of oil on all particle sizes. These results support our hypothesis that SLIPS/LIS may occur in natural soil systems. These results have implications for soil water repellency, oil clean up from soil and for processes occurring in other sedimentary environments caused by both naturally occurring and anthropogenic contamination of oils.
separating groundwater response to climate and anthropogenic changes using long-term groundwater head time series in the Netherlands
Authors: Zaadnoordijk Willem
Published: March 2020

A set of time series has been investigated which spans more than 50 years of groundwater head measurements throughout the Netherlands.
The relation between the groundwater head and precipitation and evaporation has been established using linear transfer noise modeling. This has been done for each entire series and for parts. The latter to detect base level changes and other groundwater regime changes.

In addition, trends in the other components of the groundwater heads have been investigated as well as possible non linearities in the groundwater response.

The link is explored between the trends and regime changes from the time series models on one hand and anthropogenic (land use) changes and climate change on the other hand.

 
The future of sea level: More knowledge, more uncertainty
Authors: Le Bars Dewi , Drijfhout Sybren , Haasnoot Marjolijn
Published: March 2020

Sea level rise is one of the most indisputable effects of global warming with important consequences for current decisions concerning mitigation and adaptation. A few evolutions in the climate and decision making fields have recently increased the concerns of sea level information users about the potential impacts of future sea level. We identify four main evolutions:

- Most countries are not on track to reach their Paris agreement emission pledges, making the goal of staying well bellow 2ºC less and less attainable.

- New climate model simulations from the Coupled Model Inter-comparison Project 6 (CMIP6) have both a higher average climate sensitivity and a larger spread between models compared to CMIP5.

- The Greenland and Antarctic ice sheets are melting faster than expected in previous IPCC reports and future projections from a recent structured expert judgment show larger expected melt and more uncertainty than both current numerical models and a previous expert judgment.

- Decision makers are more and more interested in events with a large impact and a small probability to build robust infrastructure and design robust long term strategies concerning relocation of coastal communities.

While these four evolutions are fundamentally deeply uncertain, to explore their combined effect we build a subjective probabilistic framework that allows to propagate the uncertainty through the different components and obtain sea level rise projections. In this presentation we present this framework, the results and their sensitivity to multiple hypothesis and we discuss implications for different uses and users of sea level rise information.
An inclusive risk assessment tool for travel and fieldwork
Authors: Prior-Jones Michael , Pinnion Jennifer , Millet Marc-Alban , Bagshaw Elizabeth , Fagereng Ake , Ballinger Rhoda
Published: March 2020

Travel and fieldwork are integral to the geosciences, and it is usual for students, academics and professionals to need to assess the risks and hazards of a planned trip in advance. In the UK, health and safety law focusses on the idea of a “risk assessment” - a process by which hazards are identified and mitigations are planned to reduce the overall risk of the activity. A recent review of our risk assessment procedures highlighted the need to better consider the needs of a diverse community, including those with “protected characteristics” in UK law. These are defined in the Equality Act 2010 as: age, disability, gender reassignment, marriage and civil partnership, pregnancy and maternity, race, religion or belief, sex, and sexual orientation.

We present our improved risk assessment forms and suggest some approaches to considering hazards and appropriate mitigations that particularly affect those people with protected characteristics. These include the need to consider how laws and attitudes, such as those towards women, or LGBT+ people, may affect the safety of participants. It is particularly important to address this in the geosciences, where fieldwork is frequently an integral part of teaching and learning activities.