bluuebunny/crossref_metadata_2025 huggingface dataset:
The Atlantic Meridional Overturning Circulation Over Time From Nd Isotopes
Authors: Yehudai Maayan , Goldstein Steve , Pena Leo D. , Kim Joohee , Jaume-Segui Maria , Basak Chandranath , Knudson Karla , Hartman Allison E. , Lupien Rachel
Published: March 2020

The Atlantic Meridional Overturning Circulation (AMOC) brings heat from the tropics to the high latitudes, and its temporal variability has major impacts on climatic cycles. We have constructed north-south profiles using deep sea cores from the North Atlantic to the Southern Ocean, covering the past ~1.5 Ma or so, including the interval prior to and including the Mid-Pleistocene Transition (MPT), the interval of ‘lukewarm interglacials’ following the MPT, and to the present-day, using Nd isotopes in Fe-Mn oxide encrusted foraminifera and fish debris. Some important observations show that our Nd isotope records indeed reflect the AMOC variability, rather than regional Nd sources or alteration effects. Firstly, throughout the time interval and at all sites, the εNd-values show glacial-interglacial ‘zig-zags’, indicating stronger AMOC during interglacials and weaker AMOC during glacials. Secondly, going from north to south the data show increasingly weaker NADW signals at all points in time. Thirdly, all of the εNd-values are those expected from seawater Nd sources. The εNd-values at North Atlantic DSDP Site 607 during interglacials are almost always between -13 and -14.5, similar to present-day NADW both before and after the AMOC-crisis, thus indicating that the normal NADW range during interglacials has remained similar since the middle Pleistocene. Fourthly, at all times, the εNd-values throughout the transect remain sandwiched by the global North Atlantic and North Pacific end-member values. These observations are what are required if the data reflect the glacial-interglacial waxing and waning of the AMOC, but are unexpected for virtually any other scenario.
Timing of rates and magnitude of sea-level rise projection families
Authors: Slangen Aimée , Haasnoot Marjolijn
Published: March 2020

In the past decade, many different projections of global and regional sea-level rise as a result of climate change have been published (Garner et al, 2018, Horton et al, 2018). This wide range of projections illustrates the large uncertainty about future sea-level rise, which is complicated for coastal decision makers relying on these projections. Here, we aim to provide insights into the available projections, by identifying the main contributing sources in each of the sea-level projections, and sorting the projections into ‘families’ that have contributing sources or methodologies in common. Using these ‘families’, we discuss the main differences between projections in terms of rates and timing of certain levels of sea-level rise. 

Sea-level rise projections are often compared by showing amounts or rates at a certain future point in time, e.g., 2050 or 2100. For many areas, a sea-level rise exceeding 1 to 2 m will require truly transformative decisions. Such decisions have a long lead time (in the order of 30 years) for planning and implementation. Showing the timing of a particular rate or magnitude of sea-level rise may provide insight that it is not a matter of if and how to adapt, but when to adapt. This may help decision makers in dealing with the uncertainties and it may accelerate adaptation.

We find that a sea-level rise of 25 cm (since 2000) is first reached for each of the RCP scenarios (the 95th percentile) within a decade of each other. This indicates that for a structure with a lifetime based on a sea-level rise of 25 cm, decisions are not conditional on the RCP scenario. The latest year for crossing the 25 cm threshold (the 5th percentile), however, does depend more on the RCP scenario: for the RCP2.6 scenario this is later than for the RCP8.5 scenario, because the acceleration is less strong. As the levels examined grow (0.25 m, 0.5 m, 0.75 m, etc.), the initial year of reaching that level starts to diverge more between the scenarios, and therefore the timing of decision points starts to be more and more conditional upon RCP scenario. However, for investments with a long envisioned lifetime such as coastal infrastructure, certain amounts of sea level rise may still be within the lifetime independent of the RCP scenario.

 
Characteristics of organic carbon in surface sediments of Laptev Sea shelf
Authors: Oberemok Irina , Gershelis Elena , Grin’ko Andrey , Ruban Alexey , Klevantseva Elizaveta , Zhivotova Natalia , Dudarev Oleg , Shakhova Natalia , Semiletov Igor
Published: March 2020

Accelerating coastal erosion and enhancing river sediment discharge are expected to greatly increase the delivery of terrestrial organic carbon (terrOC) to the Arctic Ocean. Remobilized terrOC may be buried in shallow or outer shelf sediments, degraded and translocated to the deeper basins, or remineralized in the water column causing a positive feedback to amplified global warming. The East Siberian Arctic Shelf (ESAS), represented by the Laptev Sea, the East Siberian Sea, and the Russian part of the Chukchi Sea, is the widest and shallowest continental shelf of the World Ocean. In the current study, we investigated surface sediment samples collected across the Laptev Sea shelf (from the coastline to the outer shelf) during the Arctic expedition onboard the Russian R/V Academician M. Keldysh during fall 2018.

We analyzed 16 samples for bulk (TOC, δ13C) and molecular (distribution and concentration of n-alkanes and PAHs) parameters. We also performed Rock-Eval (RE) analysis in order to compare its results with the signatures provided by traditional geochemical tracers and thereby to gain new insights into the sources of organic matter in modern surface sediments. In addition, a grain-size analysis was carried out to reveal hydrodynamic control on the organic carbon transport across the studied transect. Using a combination of traditional molecular interpretations (performed in this study and published earlier) and RE parameters (Hydrogen index, Oxygen index and Tpeak) we attempted to distinguish riverine input and coastal erosion and disentangle processes of terrOC degradation and its replacement with fresh/marine OC during cross-shelf transport. Overall, a strong decrease of terrigenous contribution to the sedimentary organic carbon was observed on molecular level with increasing distance from the coast. According to the RE data, intensive terrOC degradation takes place in the shallow and mid-shelf sediments which is traced by sharply increasing oxygen index. The clear correlation between OI and the clay content points toward the perception that mineral matrix do not seem to be such good protector as expected, and intensive microbial degradation of the sedimentary organic matter contained in fine particles occurs during repeated resuspension.

This research is supported by Russian Science Foundation, project # 19-77-00067.
CMIP model evaluation with the ESMValTool v2.0
Authors: Lauer Axel , Iglesias-Suarez Fernando , Eyring Veronika , development team the ESMValTool
Published: March 2020

The Earth System Model Evaluation Tool (ESMValTool) has been developed with the aim of taking model evaluation to the next level by facilitating analysis of many different ESM components, providing well-documented source code and scientific background of implemented diagnostics and metrics and allowing for traceability and reproducibility of results (provenance). This has been made possible by a lively and growing development community continuously improving the tool supported by multiple national and European projects. The latest version (2.0) of the ESMValTool has been developed as a large community effort to specifically target the increased data volume of the Coupled Model Intercomparison Project Phase 6 (CMIP6) and the related challenges posed by analysis and evaluation of output from multiple high-resolution and complex ESMs. For this, the core functionalities have been completely rewritten in order to take advantage of state-of-the-art computational libraries and methods to allow for efficient and user-friendly data processing. Common operations on the input data such as regridding or computation of multi-model statistics are now centralized in a highly optimized preprocessor written in Python. The diagnostic part of the ESMValTool includes a large collection of standard recipes for reproducing peer-reviewed analyses of many variables across atmosphere, ocean, and land domains, with diagnostics and performance metrics focusing on the mean-state, trends, variability and important processes, phenomena, as well as emergent constraints. While most of the diagnostics use observational data sets (in particular satellite and ground-based observations) or reanalysis products for model evaluation some are also based on model-to-model comparisons. This presentation introduces the diagnostics newly implemented into ESMValTool v2.0 including an extended set of large-scale diagnostics for quasi-operational and comprehensive evaluation of ESMs, new diagnostics for extreme events, regional model and impact evaluation and analysis of ESMs, as well as diagnostics for emergent constraints and analysis of future projections from ESMs. The new diagnostics are illustrated with examples using results from the well-established CMIP5 and the newly available CMIP6 data sets.
S-wave reflection imaging of a tectonically determined cavern by use of next generation electro-mechanic vibrator
Authors: Labak Peter , Kovacs Attila , Hegedus Endre
Published: March 2020

The key objectives of a ground-based geophysical mapping during an On-site Inspection are to detect, locate and characterize the zones of rock damage associated with an underground nuclear explosion (UNE). The cavity, rubble zone and fracturized rock matrix are also common features in the close vicinity of a cave of karstic origin. The natural cavities are mainly developed within the weakest zones of the rock matrix. The connatural features with an UNE are important but the thermal and pressure effects are lacking in the case of natural origin. However, the similarities may justify the efforts to investigate the cavern and its surroundings by geophysical methods.

 

The oval shaped cavern with a diameter of 28 m located 70 m below the surface was discovered within a clay mine in N-Hungary. The deep basement is composed of Triassic limestone, the cavern is located in the overlying Oligocene sandstone formation. As a result of hydrothermal activity in the Pleistocene a cave formed in the limestone which may have collapsed over time. The opening of the deep part of the cave influenced the overlying sandstone formation but the collapse did not reach the surface.

 

As a consequence of a UNE the cracks and open fissures could provide a pathway for the radioactive gas to find its way near to the surface. The detection of these fracturized zones require the highest possible resolution of the seismic imaging of the subsurface. Therefore, we made a 2D survey above the cavern site and determined that the optimal method is to generate and detect horizontally polarized (SH) waves. The electro-mechanically driven vibrator has provided a bandwidth ranging from 5 to 200 Hz which can be extended up to 400 Hz. The use of the Lightning type vibrator has broadened the seismic bandwidth achieving the maximum penetration of 250 m with substantial increase of the resolution.

The joint interpretation of the seismic and geoelectric tomographic results with the SH- wave reflection section has provided a clear pattern of the tectonized rock matrix around the cavern.

 
Modelling overland flow concentration in urban area with structural and geometric effects
Authors: Chen Yu-Chang , You Jiing-Yun
Published: March 2020

Recently, urban flooding has become an important issue due to heavy rainfall and rapid urbanization. For urban flooding, the drainage of stormwater is essential in inundation analysis, including the concentration of overland flow and the transportation in sewer system. However, in the past, the concentration of overland flow has not been well examined, especially under the influence of building structures. In the past, the overland flow in urban area is hard to calculate and causing lots of computation time. Currently, two-dimensional hydraulic models become an important tool for flood planning and management. In this study, we compare two hydraulic numerical models based of grid cell. So, we can flow pattern of overland flow in urban area for better understanding. First one is FLO-2D, which uses full dynamic wave momentum equation to predict the progression of a flood hydrograph. The second model is GSSHA, a physically-based, distributed model, which uses diffusive wave equation as governing equation to execute numerical simulation. With these two hydraulic models, this study focuses on how the constructions affect the water flow during the flood and whether they can be an important factor to influence the drainage system in urbanized area.

Keywords: urban flooding simulation, two-dimensional hydraulic model, influence of buildings, rainfall-runoff model, FLO-2D, GSSHA
An experimental evaluation of impact force on a fiber bragg grating (FBG)-based device for debris flow warning
Authors: Zhang Shaojie
Published: March 2020

Conventional sensors for debris flow monitoring suffer from several drawbacks including low service life, low reliability in long-distance data transfer, and stability in severe weather conditions. Recently, fiber Bragg grating (FBG)-based sensors have been developed to monitor debris flows. However, they can be easily damaged by the impact forces of boulders within debris flow. This paper presents a new FBG-based device to measure the strain induced by the impact force of debris flow with high reliability and effectiveness. The effects of the impact forces of debris flows have been investigated. Then, the relationship between the strain and the debris flow energy correlating with the damage to building structures has been established. It is shown that this new FBG-based device is capable of monitoring and warning about debris flows. The impact experiment results show that the peak value of dynamic strain on the fixed end of the new device is positively correlated with the external impact force. Using an impact force, we establish a relationship between the measured strain and the potential of a debris flow resulting in damage to structures was established. This follows the general rule that a larger measured strain corresponds to a higher level of debris flow. Using this relationship, we can quantify a dangerous level of debris flow using the monitored strain data. Our new device is capable of monitoring and warning about dangerous debris flows, allowing for more effective debris flow mitigation.
In-situ Measurements of the Tropopause Aerosol Layer at the Tibetan Plateau and the Influence of the Volcanic Eruptions
Authors: Wu Xue , Zhang Jinqiang , Lyu Daren
Published: March 2020

A robust but thin aerosol layer in summer extending geographically from Eastern Mediterranean to Western China, the Asian Tropopause Aerosol Layer (ATAL) was observed and verified by the CALIPSO lidar measurements. However, its source and forming mechanism is still under debate. In August 2018 and 2019, two experimental campaigns over the Tibetan Plateau were carried out at Golmud (GLM, 36.48°N, 94.93°E) and Qaidam (QDM, 37.74°N, 95.34°E), during which a balloon-borne Portable Optical Particle Counter (POPS) was used to measure the features of aerosol particulates. The in-situ measurements show a robust ATAL around the tropopause, ranging from 14 to 18 km a.s.l., with a maximum aerosol number density of 35–40 cm-3 and a maximum aerosol mass concentration of 0.13 μg m-3 for particles with diameters between 0.12 and 3 μm, and majority of the particulates (98%) are smaller than 0.4 μm in diameter.

Backward-trajectory simulations are conducted with the Massive-Parallel Trajectory Calculations (MPTRAC) model to investigate the possible sources and transport pathways of the observed particulates. The backward-trajectory analysis revealed that the air parcels arrived at the altitude of the ATAL through two separate pathways: 1) the uplift below the 360 K isentropic surface, where air parcels were first elevated to the upper troposphere and then joined the ASM anticyclonic circulation, which will take about 5–10 days; and 2) the quasi-horizontal transport along the anticyclonic circulation, located approximately between the 360 and 440 K isentropic surfaces. The dispersion of the volcanic aerosol from the volcanic eruption of Raikoke in June 2019 has enhanced the aerosol layer in the Tibetan Plateau upper troposphere and lower stratosphere (UTLS), but the ATAL was not concealed by the volcanic plume because the boundary of the Asian summer monsoon (ASM) anticyclone acted as a transport barrier which stopped most of the volcanic aerosol entering the ASM region. Only at most 20% of the aerosol particulates observed in the Tibetan Plateau UTLS was contributed by the Raikoke volcanic eruption. Comparing with the Nabro eruption in 2011, the influence of volcanic eruption on the ATAL significantly depends on the relative geographical location of the volcanic eruption and the ASM anticyclone, as well as the volcanic plume height.
Assessing the Impact of Uncertainties of Digital Elevation Models on Hydro-Geomorphological Analysis Using Gaussian White Noise
Authors: Graf Lukas , Moreno-de-las-Heras Mariano , Estrany Joan
Published: March 2020

Digital elevation models (DEM) are mathematical representations of the Earth's bare surface in computer-readable format. The underlying measurements are often obtained by remote sensing and photogrammetry methods and processed into continuous raster data. Each of these data sources, however, provides imperfect information, and further processing steps often increase the degree of imperfection. Consequently, the process of DEM generation cumulates in uncertainty, which affects subsequent hydro- and geomorphological analyses and modelling (e.g., stream network delineation, flowpath distribution, erosion modelling).

In many DEM-based studies, however, the aspect of uncertainty related to the DEM data source has been neglected. Therefore, we propose a new approach for quantifying the effects of DEM uncertainty on hydro-geomorphological modelling based on Gaussian white noise, a concept widely used in signal processing to map noise in signals and extract the actual message context. The basic idea is to add noise to the original DEM values by means of a Gaussian distribution whose parameters are determined from the mean value of the elevation values in a moving window and the device-specific properties (precision and accuracy).

We postulate that such an approach can be used to determine uncertainties and their effect on subsequent analysis steps of hydro-geomorphological modelling. It is conceivable to create DEM ensembles depending on known parameters such as the accuracy and precision of the measuring instrument, as is used operationally in weather forecasting. Using such ensembles, probability ranges for terrain and catchment hydro-geomorphological properties can be determined and uncertainty ranges can be specified. Thus, the currently mostly deterministic approach of digital terrain modelling will be replaced by a more probabilistic understanding. Overall, our approach will help decision-makers and scientists to better assess the results of digital terrain analysis. Furthermore, it will also facilitate determining whether a result of DEM-based hydro-geomorphological analysis is sufficiently certain to answer specific research questions.
The Evolution Process of Warm Season Intense Regional Rainfall Events in Yaan
Authors: Hu Xuelin
Published: March 2020

Accurate simulation and prediction of intense precipitation events require better understanding of their physical mechanisms. This study uses Yaan—a place with regional maximum rainfall in central China—to investigate the cause and process of intense precipitation. Hourly rain gauge records and the new ERA5 reanalysis are used to characterize the evolution process of warm season intense regional rainfall events (RREs) in Yaan and its associated three-dimensional circulation. Results show that before the start of the Yaan intense RREs, moderate rainfall amount (frequency) appears northeast of the key region. The rainfall then moves southward in the following several hours along the eastern periphery of the Tibetan Plateau where it reaches peak. It then moves to and end up in the south and southeast Sichuan Basin. The progression of the RREs is found to be associated with a counter-clockwise rotation of anomalous surface winds associated with a developing mesoscale surface low-pressure center, which is further associated with the southeastward progression of a large-scale synoptic scale wave. The easterly phase of the winds in the counter-clockwise rotation causes upslope motion perpendicularly toward the terrain that leads to maximum rainfall. The findings illustrate how large-scale circulations, mesoscale systems, and specific topographic features interact to create the RREs evolution in Yaan.
Long-term Runoff Forecasting Models Based on the Teleconnection coupled with Machine Learning
Authors: Zhang Teng , Wang Zhongjing , Zhang Zixiong
Published: March 2020

Runoff forecast with high precision is important for the efficient utilization of water resources and regional sustainable development, especially in the arid area. The monthly runoff of Changmabao (CMB) station has an upwards trend and an abrupt point in 1998. The impact factor analysis shows that it is highly correlated with the current precipitation and temperature in the wet season while the previous runoff and previous global land temperature in the dry season. Three models including the time-series decomposition model, the model based on teleconnection coupled with the support vector machine, and the model based on teleconnection coupled with the artificial neural network are used to predict the runoff of CMB station. An indicator β is constructed with the correlation coefficient (R) and mean relative deviation (rBias) to evaluate the model performance more conveniently and intuitively. The results suggest that the model based on teleconnection coupled with the support vector machine preforms best. This forecasting method could be applied to the management and dispatch of water resources in arid areas.
What value do mangroves have in reducing the cost of storm surges?
Authors: Thomas Christopher , Narayan Siddharth , Matthewman Joss , Shepard Christine , Geselbracht Laura , Nzerem Kechi , Beck Mike
Published: March 2020

With coastlines becoming increasingly urbanised worldwide, the economic risk posed by storm surges to coastal communities has never been greater. Given the financial and ecological costs of manmade coastal defences, the past few years have seen growing interest in the effectiveness of natural coastal “defences” in reducing the risk of flooding to coastal properties, but estimating their actual economic value in reducing storm surge risk remains a challenging subject.

In this study, we estimate the value of mangroves in reducing annual losses to property from storm surges along a large stretch of coastline in Florida (USA), by employing a catastrophe modelling approach widely used in the insurance industry. We use a hydrodynamic coastal flood model coupled to a property loss model and a large property exposure dataset to estimate annual economic losses from hurricane-driven storm surges in Collier County, a hurricane-prone part of Florida. We then estimate the impact that removing mangroves in the region would have on average annual losses (AAL) caused by coastal flooding. We find that mangroves reduce AAL to properties behind them by over 25%, and that these benefits are distributed very heterogeneously along the coastline. Mangrove presence can also act to enhance the storm surge risk in areas where development has occurred seaward of mangroves.

In addition to looking at annual losses, we also focus on the storm surge caused by a specific severe event in Florida, based on Hurricane Irma (2017), and we estimate that existing mangroves reduced economic property damage by hundreds of millions of USD, and reduced coastal flooding for hundreds of thousands of people.

Together these studies aim to financially quantify some of the risk reduction services provided by natural defences in terms of reducing the cost of coastal flooding, and show that these services can be included in a catastrophe modelling framework commonly used in the insurance industry.
Cr6+ adsorption by modified vermiculite
Authors: Medoro Valeria , Marcos Pascual Celia , Ferretti Giacomo , Galamini Giulio , Coltorti Massimo
Published: March 2020

Abstract: Cr6+ adsorption by modified vermiculite

 

Valeria Medoro- University of Ferrara , Department of Physics and Earth Sciences, Italy

Celia Marcos Pascual-University of Oviedo, Department of Geology, Spain

Giacomo Ferretti- University of Ferrara , Department of Physics and Earth Sciences, Italy

Giulio Galamini- University of Ferrara , Department of Physics and Earth Sciences, Italy

Massimo Coltorti- University of Ferrara , Department of Physics and Earth Sciences, Italy

 

This work aimed at investigating the adsorption of Cr6+ in water by exfoliated vermiculite. The adsorbant tested in this experiment was a vermiculite (from China) which has been subjected to heating at 1000 °C for 1 minute, resulting in an exfoliated vermiculite.

Three effects were studied: 1) contact time; 2) initial concentracion of Cr6+; 3) adsorbent mass. Samples were analysed by X Ray Fluorescence (XRF), X Ray Diffraction (XRD) and the solutions with Inductively Coupled Plasma Mass Spectrometry (ICP-MS) to quantify the adsorbed Cr6+ by the vermiculite.

Results from XRD diffraction showed a conversion of vermiculite into flogopite  after heating at 1000°C for 1 minute because of: 1) high content of potassium, 2) dehydration and 3) structural re-ordering; after the contact of vermiculite with Cr6+, the mineral structure did not change. The adsorption of Cr6+ was studied by Langmuir, Freundlich and Dubinin-Kaganer-Radushkevich (DKR) isotherm models. DKR model, indicative of a cooperative process, described adsorption equilibrium better than the other two models and the maximum adsorption capacity obtained was of 2.81 mol/g. Kinetic was studied using pseudo-first and pseudo-second order kinetic models, with a better description of the process by pseudo-second order model with correlation coefficient almost unitary (R2=0.9984; other kinetic parameters were k2=0.0015 and the absorption initial rate of 0.2x10-8 mg g-1 h-1). 

The present study demonstrates the effectiveness of modified vermiculite adsorbents for the treatment of hexavalent chromium-contaminated waters and that its adsorption depends on the experimental conditions (such as contact time, initial concentracion of Cr6+ and adsorbent mass).
A sea ice-free Arctic during the Last Interglacial supports fast future loss
Authors: Guarino Maria Vittoria , Sime Louise , Schroeder David , Malmierca-Vallet Irene , Rosenblum Erica , Ringer Mark , Ridley Jeff , Feltham Danny , Bitz Cecilia , Steig Eric , Wolff Eric , Stroeve Julienne , Sellar Alistair
Published: March 2020

The Last Interglacial (LIG) is a period of great importance as an analog for future climate change. Global sea level was 6-9 m higher than present. Stronger LIG summertime insolation at high northern latitudes drove Arctic land summer temperatures around 4-5 K higher than during the preindustrial era. Climate-model simulations have previously failed to capture these elevated temperatures. This may be because these models failed to correctly capture LIG sea ice changes.

Here, we show that the latest version of the UK Hadley Center coupled ocean-atmosphere climate model (HadGEM3) simulates a much improved Arctic LIG climate, including the observed high temperatures. Improved model physics in HadGEM3, including a sophisticated sea ice melt-pond scheme, results in the first-ever simulation of the complete loss of Arctic sea ice in summer during the LIG.

Our ice-free Arctic yields a compelling solution to the long-standing puzzle of what drove LIG Arctic warmth. The LIG simulation result is a new independent constraint on the strength of Arctic sea ice decline in climate-model projections, and provides support for a fast retreat of Arctic summer sea ice in the future.
Precipitation Retrieval over the Tibetan Plateau from the Geostationary Orbit
Authors: Kolbe Christine , Thies Boris , Turini Nazli , Bendix Jörg
Published: March 2020

The distribution of precipitation on the Tibetan Plateau (TiP) is not yet understood due to various factors. Satellite-based precipitation retrieval can provide comprehensive information in a high spatial-temporal resolution. The aim of this feasibility study is to retrieve precipitation rates over High Asia using multi-spectral data from the two geostationary (GEO) satellites Elektro-L2 and Insat-3D in a 30 minutes and 4 km resolution. The variety of spectral bands from both satellites provides an insight into the cloud properties which are associated with precipitation. In the first step, the precipitation area is delineated, and in a second step, the rates are retrieved. To this end, we use a machine learning approach (Random Forest, RF) and a precipitation product of the Global Precipitation Measurement Mission (GPM IMERG) as a reference. From this product, we use the best quality gauge calibrated microwave (MW) precipitation estimates. We validate our results with independent gauge calibrated MW precipitation. To improve the RF models, we tested various optimization schemes. The results of this study will provide information about the precipitation processes in High Asia.
Crustal structure and evolution of the Niuafo'ou Microplate in the northeastern Lau Basin, Southwestern Pacific
Authors: Schmid Florian , Kopp Heidrun , Schnabel Michael , Dannowski Anke , Heyde Ingo , Riedel Michael , Engels Martin , Beniest Anouk , Klaucke Ingo , Augustin Nico , Brandl Philipp , Devey Colin , Hannington Mark
Published: March 2020

The northeastern Lau Basin is one of the fastest opening and magmatically most active back-arc regions on Earth. Although the current pattern of plate boundaries and motions in this complex mosaic of microplates is fairly well understood, the structure and evolution of the back-arc crust are not. We present refraction seismic, multichannel seismic and gravity data from a 300 km long east-west oriented transect crossing the Niuafo’ou Microplate (back-arc), the Fonualei Rift and Spreading Centre (FRSC) and the Tofua Volcanic Arc at 17°20’S. Our P wave tomography model shows strong lateral variations in the thickness and velocity-depth distribution of the crust. The thinnest crust is present in the Fonualei Rift and Spreading Center, suggesting active seafloor spreading there. In the much thicker crust of the volcanic arc we identify a region of anomalously low velocities, indicative of partial melts. Surprisingly, the melt reservoir is located at ~17 km distance to the volcanic front, supporting the hypothesis that melts are deviated from the volcanic arc towards the FRSC in sub-crustal domains. We identify two distinct regions in the back-arc crust, representing different opening phases of the northeastern Lau Basin. During initial extension, likely dominated by rifting, crust of generally lower upper-crustal velocities formed. During an advanced opening phase, likely dominated by seafloor spreading, crust of higher upper-crustal velocities formed and is now up to 11 km thick. This thickening is the result of magmatic underplating, which is supported by elevated upper mantle temperatures in this region.
Erosion assessment in the desertification site of Gilbues, Brazil
Authors: de Araújo José Carlos , Simplício Antonio Álisson , Pereira Francisco Jairo , Gomes Costa Carlos Alexandre
Published: March 2020

The Gilbués Desertification Site (GDS) is an 8,000-km² area located in the Northeast of Brazil. It comprises large continuous areas with deep (up to 30 m), wide (up to 50 m), and long (up to 6 km) gullies, as well as severe inter-rill erosion. Inside the GDS there is an experimental site, in which almost 100 check dams were constructed a decade ago to assess their feasibility as a soil-restoration initiative. For two years (2018 and 2019) we have monitored a 15-ha watershed that contains 52 check dams so as to estimate the main erosion-related parameters as well as to assess the effectiveness of the check dams. The monitoring program consisted of (i) a climate station; (ii) four hillslopes with pins every m², measured monthly to quantify gross erosion; (iii) five flights with an accurate unmanned aerial vehicle (UAV) to identify the siltation of the check dams and to parameterize the rainfall-runoff behavior; (iv) 92 soil samples in the hillslopes and inside the check dams; and (v) four infiltration experiments. The results show that (i) the gross erosion is 8 mm.yr-1, or 10² Mg.ha-1.yr-1, a value ten times higher than the region average; (ii) based on the silting of the check dams, the sediment yield averaged 85 Mg.ha-1.yr-1, 20 times higher than the regional mean value, which is partially explained by the small size of the watersheds (10²-10³ m²); (iii) the Wischmeier vegetation C factor is 0.9, showing high degree of vegetative-cover degradation; and (iv) the sediment delivery ratio was 0.8, which could be satisfactorily represented by the Maner equation. These results show that, although the GDS corresponds to only 10% of the Boa Esperança (5,000 hm³) hydroelectric power plant basin, it may cause 60% of the reservoir silting. The GDS soil has also shown specific properties: 71% of the soil mass has a diameter of ~ 0.1 mm; there is a high rate of open macro-pores when the soil is dry (they close shortly after a moderate rainfall event ~ 40 mm); and it is prone to form gravel-like particles that silt in the reservoir delta (despite its fine diameter). Last, we observed that the check dams – as they were built – are not a sustainable solution: after a decade, nearly 10% are spilling due to the high siltation rates, causing dam-wall erosion and instability; and three dams have presented piping, with discharges (0.2 – 0.7 L.s-1) one thousand times higher than the expected percolation flow through the dams.
Effects of secondary static stress triggering on the spatial distribution of aftershocks, a case study, 2003 Bam earthquake (SE Iran)
Authors: Maleki Asayesh Behnam , Zafarani Hamid , Tatar Mohammad
Published: March 2020

Immediate after a large earthquake, accurate prediction of spatial and temporal distribution of aftershocks has a great importance for planning search and rescue activities. Currently, the most sophisticated approach to this goal is probabilistic aftershock hazard assessment (PASHA). Spatial distribution of the aftershocks fallowing moderate to large earthquakes correlate well with the imparted stress due to the mainshock. Furthermore the secondary static stress changes caused by smaller events (aftershocks) could have effect on the triggering of aftershocks and should be considered in the calculations. The 26 December 2003 (Mw 6.6) Bam earthquake with more than 26000 causalities is one of the most destructive events in the recorded history of Iran. This earthquake was an interesting event and was investigated in a majority of aspects. Good variable-slip fault model and precise aftershocks data enabled us to impart Coulomb stress changes due to mainshock and secondary static stress triggering on the nodal planes of aftershocks to learn whether they were brought closer to failure.

We used recently published high-quality focal mechanisms and hypocenters to reassess the role of small to moderate earthquakes for static stress triggering of aftershocks during the Bam earthquake. By imparting Coulomb stress changes due to the mainshock on the nodal planes of the 158 aftershocks we showed that 77.8% (123 from 158) of the aftershocks received positive stress changes at least in one nodal plane. We also calculated Coulomb stress changes imparted by the mainshock and aftershocks (1≤M≤4.1) onto subsequent aftershocks nodal planes and found that 81.6% (129 of 158) of aftershocks received positive stress changes at least in one nodal plane. In summary, 77.8% of aftershocks are encouraged by the main shocks, while adding secondary stress encourages 81.6%. Therefore, by adding secondary stress the Coulomb Index (CI), the fraction of events that received net positive Coulomb stress changes compared to the total number of events, increased from 0.778 to 0.816.
Watertable fluctuation-induced variability in the water retention curve: Sand column experiments
Authors: Luo Zhaoyang , Kong Jun , Ji Zhiling , Shen Chengji , Lu Chunhui , Xin Pei , Zhao Zhongwei , Li Ling , Barry D. Andrew
Published: March 2020

The soil water retention curve (WRC), describing the relation between the soil water content and its corresponding capillary pressure, relies not only on whether drying or wetting occurs but also on the pore scale water flow velocity. Here, we investigated the effects of the watertable fluctuations on the WRC through 28 laboratory experiments covering a wide range of fluctuation amplitudes and periods. Results show that both the response of the capillary pressure and soil water content lag behind the watertable fluctuation, and the vertical capillary pressure distribution in the unsaturated zone is non-hydrostatic, especially for the fluctuations with shorter period. As a consequence of watertable fluctuation, the measured WRC deviates from that under static conditions, depending on both the fluctuation amplitude and period. Moreover, the air-entry pressure under dynamic conditions is considerably larger than that under static conditions, and it first increases and then decreases as the fluctuation period decreases. The effects of the watertable fluctuations on the dynamic capillary coefficient was further examined. It is found that the relation between the dynamic capillary coefficient and saturation is nonunique even for the drying and wetting of a given sand and watertable fluctuation, suggesting a hysteretic dynamic capillary coefficient, and the dynamic capillary coefficient is rate-dependent, decreasing with an increase of fluctuation rate.
A Citizen Science Web Portal for Interdisciplinary Research on Climate Change (BAYSICS): Development and Evaluation
Authors: Batsaikhan Anudari , Weismüller Jens
Published: March 2020

Citizen science can be used to collect vast and timely data, while promoting active learning on selected topics. The Bavarian Citizen Science Portal for Climate Research and Science Communication (BAYSICS) is a scientific project which started in 2018 with 10 partner institutions in Bavaria. It aims to achieve (1) citizens’ participation in climate change research through innovative digital forms, (2) transfer of knowledge on the complexity of climate change and its local consequences, and (3) joint scientific and environmental education goals. 

Within the BAYSICS project, a web portal has been developed that builds the interface between researchers and citizens. In the initial phase, the interests from the different research disciplines participating in the project were identified. Currently, the IT structure for the web portal is developed based on the needs of the project. Free tools such as PostgreSQL, Django, Gunicorn and Nginx are used. The researchers involved have the opportunity to integrate research topic specific questions and data collection guidelines for citizens. 

On the web portal, users are able to choose a topic from four different areas (phenology, pollen, tree, and animals) and submit their observations in multiple data types (pictures, geolocations, and texts). The observation data is visualized on a map of the web portal. The data collected within the project is freely available for download on the web portal, while protecting user’s privacy. Application Programming Interface (API) is developed to enable interaction with other software products and services.

A first test phase within the project members start at the beginning of 2020. Afterwards, a second test phase is planned involving potential users (e.g. school students and teachers). The outcomes from the test phases will be used for evaluation.
Trace elements in quartz vein of Gubong gold deposit, Republic of Korea
Authors: Yoo Bong Chul , Seo Jung Hun , Heinrich Christoph A. , Lee Bum Han
Published: March 2020

  The Gubong gold deposit is located in the Cheonan metallogenic province which records a highest gold production areas in the Republic of Korea. The Gubong deposit is the richest gold deposit in the province and consists of five stages of massive quartz veins that fill fractures along fault shear zones orienting NE and NW hosted in Precambrian metasedimentary rocks (Gyeonggi massif).

  Ores and alteration minerals of Gubong deposit are sericite, chlorite, epidote, illite, K-feldspar, plagioclase, biotite, quartz, calcite, magnetite, ilmenite, rutile, zircon, monazite, apatite, pyrite, gersdorffite, arsenopyrite, pyrrhotite, sphalerite, marcasite, chalcopyrite, galena, and electrum. Fluid inclusion microthermometry and textural relationships in veins indicate that early sulfide deposition is associated with H2O-CO2-CH4-NaCl±N2 bearing hotter hydrothermal fluids (203~432oC, ≤ 13.4 wt % NaCl) and late sulfide deposition is associated with H2O-NaCl bearing fluids (202~399oC, 3.9~17.3 wt % NaCl) cooled and diluted possibly by mixing with meteoric water.

  Trace element analyses in quartz from veins were performed by using LA-ICP-MS (193-nm ArF Excimer laser combined with an Elan 6100 quadrupole mass spectrometer) at ETH Zürich. Concentration of trace elements in quartz including Li (<0.01~3.55 ppm), B (3.03~27.17 ppm), Na (3.23~72.79 ppm), Al (4.0~149.9 ppm), P (14.4~68.9 ppm), Sc (3.3~8.7 ppm), Ti (<0.10~1.43 ppm), Cr (<3.34~65.6 ppm), Ga (0.50~1.30ppm), Ge (0.57~2.15 ppm), Rb (<0.01~0.50 ppm), Sr (0.01~3.13 ppm), Sn (<0.29~7.24 ppm), Sb (<0.05~0.42 ppm), and Bi (<0.01~8.30 ppm) are reported. Some trace elements (Al, Na, Ga, P, Li) tend to correlate positively. Titanium versus aluminum concentrations in quartz from Gubong deposit are plotted in the field of orogenic Au deposit suggested by Rusk (2012). We analyzed quartz from other numerous Korean Au-Ag and W-Mo deposits to compare hydrothermal fluid conditions and to provide a geochemical tool for mineral exploration.

Reference

Rusk, B.G., 2012, Cathodoluminescent textures and trace elements in hydrothermal quartz: Quartz: Deposits, Mineralogy and Analytics, Jens Götze and Robert Möckel, Springer, p. 307-329.
Assessment of relationships between Arctic sea ice and stratification of water column modelled by NEMO version 4.0
Authors: An Byoung Woong , Chang Pil-Hun
Published: March 2020

The Arctic Ocean is globally important for the weather and climate and has a unique environment. Therefore accurate prediction of the Arctic sea ice remains crucial in most numerical models. It is because small changes within the atmosphere or the ocean can cause major changes in the areal extent and thickness of the sea ice. Such changes, in turn, will have pronounced effects on the ocean and atmosphere through modification of the albedo, the ocean-atmosphere heat and momentum exchanges, and the ocean-ice heat and salt fluxes. The focus of this study is on the impact of such coupling on sea ice and upper ocean properties and the halostad related sea ice variations and inflows from Oceans. To assess the impact of the vertical mixing, we perform a set of sensitivity experiments with a global oceanic configuration at 1/4° resolution based on the version 4.0 of NEMO (Nucleus for European Modelling of the Ocean). In particular we examine the spatio-temporal distributions of Pacific and Eastern Arctic origin waters in the Chukchi Sea using 2016-2018 hydrographic data. Overall, the model agrees well with observations in terms of sea ice extent in spite of inaccurate vertical stratification of the water column. We conclude that beyond seasonal time scale forecast accuracy could be improved by more accurate representation of the structure of water masses.
Can moisture content estimates from nuclear magnetic resonance improve optically stimulated luminescence dating - first results on Loess samples from Toshan/Iran
Authors: Dlugosch Raphael , Zeeden Christian , Lauer Tobias , Tsukamoto Sumiko
Published: March 2020

Dating of loess deposits using optically stimulated luminescence (OSL) enable us to extract important information about the climate during the last ~150 ka. A good estimation of the dose rate during the past is essential for OSL and depends, among others, on the history of the moisture content in the proximity of the dated sample. While the current moisture content can be measured by heating/drying, the history of the moisture variations of a sample is generally unknown. Reference values reported on similar materials and climate conditions may provide a range for the expected moisture variations in the past, but these values are generally rough guesses and not depth- and time-specific.

Nuclear magnetic resonance (NMR) relaxometry targeting the hydrogens of the pore fluid can estimate the current moisture content of a sample without heating. Additionally, the NMR relaxation time distribution yields information of the expected moisture content for a given field potential (e.g. wilting point). This can help to estimate a sample-specific range of likely moisture variation in a quick (several min) and no-invasive way.

We discuss this new approach on a loess profile from Toshan (Iran) published previously by (Lauer et al., 2017) and (Vlaminck, 2018). The later pointed out inconsistencies in the obtained age model. The estimated sample specific moisture content for the wilting point (15 to 35 wt.%) provide the low boundary for the moisture content estimate, which is higher than previously assumed (5 wt.%). The new dose rate calculated for these sample specific moisture content values lead to clearly older and more consistent ages (less age inversions).

We suggest that NMR derived moisture content data is valuable for obtaining information on the moisture content of samples. Especially the minimum moisture can be derived reliably, giving more robust water content estimates for OSL dating.

 

 

References

Lauer, T., Vlaminck, S., Frechen, M., Rolf, C., Kehl, M., Sharifi, J., Lehndorff, E., Khormali, F., 2017. The Agh Band loess-palaeosol sequence – A terrestrial archive for climatic shifts during the last and penultimate glacial–interglacial cycles in a semiarid region in northern Iran. Quaternary International, Loess, soils and climate change in Iran and vicinity 429, 13–30. https://doi.org/10.1016/j.quaint.2016.01.062

Vlaminck, S., 2018. Northeastern Iranian loess and its palaeoclimatic implications (PhD Thesis). Universität zu Köln.