bluuebunny/crossref_metadata_2025 huggingface dataset:
Geological Insigths Gained from a Seismic Data Lake
Authors: Rodriguez Karyna , Hodgson Neil
Published: March 2021

Seismic data has been and continues to be the main tool for hydrocarbon exploration. Storing very large quantities of seismic data, as well as making it easily accessible and with machine learning functionality, is the way forward to gain regional and local understanding of petroleum systems. Seismic data has been made available as a streamed service through a web-based platform allowing seismic data access on the spot, from large datasets stored in the cloud. A data lake can be defined as transformed data used for tasks such as reporting, visualization, advanced analytics and machine learning. The global library of data has been deconstructed from the rigid flat file format traditionally associated with seismic and transformed into a distributed, scalable, big data store. This allows for rapid access, complex queries, and efficient use of computer power – fundamental criteria for enabling Big Data technologies such as deep learning.  

This data lake concept is already changing the way we access seismic data, enhancing the efficiency of gaining insights into any hydrocarbon basin. Examples include the identification of potentially prolific mixed turbidite/contourite systems in the Trujillo Basin offshore Peru, together with important implications of BSR-derived geothermal gradients, which are much higher than expected in a fore arc setting, opening new exploration opportunities. Another example is de-risking and ranking of offshore Malvinas Basin blocks by gaining new insights into areas until very recently considered to be non-prospective. Further de-risking was achieved by carrying out an in-depth source rock analysis in the Malvinas and conjugate southern South Africa Basins. Additionally, the data lake enabled the development of machine learning algorithms for channel recognition which were successfully applied to data offshore Australia and Norway.

“On demand” regional seismic dataset access is proving invaluable in our efforts to make hydrocarbon exploration more efficient and successful. Machine learning algorithms are helping to automate the more mechanical tasks, leaving time for the more valuable task of analysing the results. The geological insights gained by combining these 2 aspects confirm the value of seismic data lakes.
Plasma turbulence generated during particle acceleration in magnetic islands
Authors: Zharkova Valentina , Xia Qian
Published: March 2021

We investigate plasma turbulence generated during particle acceleration in magnetic islands within 3D Harris-type reconnecting current sheets (RCSs),using the particle-in-cell approach.  RCSs with a strong guiding magnetic field  ar shown to lead to separation of electrons and ions into the opposite sides from the current sheet mid-plane that significantly reduces kink instability along the guiding field direction. Particles with the same charge also have asymmetric trajectories forming two distinct populations of beams: ‘transit’ particles, which pass through RCS from one edge to another, become strongly energised and form nearly unidirectional beams; and ‘bounced’ particles, which are reflected from the diffusion region and move back to the same side they entered the current sheet, gaining much less energy and forming more dispersive spatial distributions. Thes transit and bounced particles form the ‘bump-on-tail’ velocity distributions that naturally generate plasma turbulence. Using the wavelet analysis of electric and magnetic field fluctuations in the frequency domain, we identified some characteristic waves produced by particle beams. In particular, we found thre are Langmuir waves near X-nullpoints produced by two electron beam instabilities, while the presence of anisotropic temperature variations inside magnetic islands lead to whistler waves. The lower-hybrid waves are generated inside the magnetic islands, owing to the two-stream instabilities of the ions. While the high-frequency fluctuations, upper hybrid waves, or electron Bernstein waves, pile up near X-nullpoints. The results can be beneficial for understanding in-situ observations with modern space missions of energetic particles in the heliosphere.
Investigation on flight level contamination using volcanic SO2 plume and cloud top height satellite products
Authors: Sievers Klaus , Brenot Hugues , Theys Nicolas , Kessinger Cathy
Published: March 2021

Volcanic emission is a major risk for air traffic. Flying through a volcanic cloud can have a strong impact on engines (damage caused by ash and/or sulphur dioxide – SO2) and persons. The knowledge of the height of the volcanic plume is indeed essential for pilots, airlines and passengers.

In this presentation, we study recent volcanic emissions to illustrate the difficulty for obtaining information about the height of the SO2 plume in a form relevant to aviation. Our study uses satellite data products. We consider SO2 layer height from TROPOMI (UV-vis hyperspectral sensor on board S5P, a polar orbiting platform), as shown by SACS (Support to Aviation Control Service), combined with cloud top observations (from the same sensors or from geostationary broadband imagers) to determine the minimum SO2-cloud height. This is a validation which is of interest to aviation.

The flight level, not the km, is the measure, the unit for expressing height during cruise flight used on board by the pilots to ensure safe vertical separation between aircraft, despite natural local variations in atmospheric air pressure and temperature. Thus, it is critical to provide the corresponding SO2 contamination expressed as flight levels. Our study will focus on this conversion that is one item currently being developed in the frame of ALARM H2020 project (https://alarm-project.eu) and SACS early warning system (https://sacs.aeronomie.be) in the creation of NetCDF alert products.
A new cost-performance grid to compare different flood modelling approaches
Authors: Hdeib Rouya , Moussa Roger , Colin François , Abdallah Chadi
Published: March 2021

The wise selection of modeling approaches with an appropriate level of complexity for the study objectives is critical for robust inference. In this paper, the structure of a cost-performance grid designed for flood modeling is presented. The grid is developed to compare different flood modeling approaches of variable complexity and to guide on the proper selection of the couple data-model. The methodology involves defining metrics to quantify the three variables: data costs, model costs, and performance. Preliminarily, eighteen flood modeling applications in literature were arbitrarily selected and analyzed to guide on the implementation of the grid. The cost-performance diagram allows tracing a cost-performance curve and grouping applications in 4 zones corresponding to 4 modeling approaches (empirical and geomorphic, hydrological, hydraulic, and coupling). The grid is a tool to support the comparison, classification, and future selection of cost-effective modeling approaches. It is flexible and can be extrapolated to other modeling objectives.
Optimal energy growth in stably stratified turbulent Couette flow
Authors: Zasko Grigory , Glazunov Andrey , Mortikov Evgeny , Nechepurenko Yuri , Perezhogin Pavel
Published: March 2021

In this report, we will try to explain the emergence of large-scale organized structures in stably stratified turbulent flows using optimal disturbances of the mean turbulent flow. These structures have been recently obtained in numerical simulations of turbulent stably stratified flows [1] (Ekman layer, LES) and [2] (plane Couette flow, DNS and LES) and indirectly confirmed by field measurements in the stable boundary layer of the atmosphere [1, 2]. In instantaneous temperature fields they manifest themselves as irregular inclined thin layers with large gradients (fronts), spaced from each other by distances comparable to the height of the entire turbulent layer, and separated by regions with weak stratification.

Optimal disturbances of a stably stratified turbulent plane Couette flow are investigated in a wide range of Reynolds and Richardson numbers. These disturbances were computed based on a simplified linearized system of equations in which turbulent Reynolds stresses and heat fluxes were approximated by isotropic viscosity and diffusion with coefficients obtained from DNS results. It was shown [3] that the spatial scales and configurations of the inclined structures extracted from DNS data coincide with the ones obtained from optimal disturbances of the mean turbulent flow.

Critical value of the stability parameter is found starting from which the optimal disturbances resemble inclined structures. The physical mechanisms that determine the evolution, energetics and spatial configuration of these optimal disturbances are discussed. The effects due to the presence of stable stratification are highlighted.

Numerical experiments with optimal disturbances were supported by the RSF (grant No. 17-71-20149). Direct numerical simulation of stratified turbulent Couette flow was supported by the RFBR (grant No. 20-05-00776).

References:

[1] P.P. Sullivan, J.C. Weil, E.G. Patton, H.J. Jonker, D.V. Mironov. Turbulent winds and temperature fronts in large-eddy simulations of the stable atmospheric boundary layer // J. Atmos. Sci., 2016, V. 73, P. 1815-1840.

[2] A.V. Glazunov, E.V. Mortikov, K.V. Barskov, E.V. Kadantsev, S.S. Zilitinkevich. Layered structure of stably stratified turbulent shear flows // Izv. Atmos. Ocean. Phys., 2019, V. 55, P. 312–323.

[3] G.V. Zasko, A.V. Glazunov, E.V. Mortikov, Yu.M. Nechepurenko. Large-scale structures in stratified turbulent Couette flow and optimal disturbances // Russ. J. Num. Anal. Math. Model., 2010, V. 35, P. 35–53.
On the prediction of magnetic field vectors of ICME using data constrained simulation with EUHFORIA
Authors: Sarkar Ranadeep , Pomoell Jens , Asvestari Eleanna , Kilpua Emilia , Mierla Marilena , Rodriguez Luciano , Poedts Stefaan
Published: March 2021

Coronal mass ejections (CMEs), the most violent eruptive phenomena occurring in the heliosphere, erupt in the form of gigantic clouds of magnetized plasma from the Sun and can reach Earth within several hours to days. If the magnetic field inside an Earth-directed CME or its associated sheath region has a southward directed component (Bz), then it interacts stronger with the Earth’s magnetosphere, leading to severe geomagnetic storms. Therefore, it is crucial to predict the magnitude and orientation of Bz inside an Earth impacting interplanetary CME (ICME) in order to forecast the intensity of the resulting geomagnetic storms. However, due to lack of realistic inputs and the complexity of the Sun-Earth system in a time-dependent heliospheric context, it is very difficult to perform a reliable forecast of Bz at 1 AU.  

In this work, we use recently developed observational techniques to constrain the kinematic and magnetic properties of CME flux ropes. Using those observational properties as realistic inputs, we construct an analytical force free flux rope model to mimic the magnetic structure of a CME and simulate its evolution from Sun to Earth using the “European heliospheric forecasting information asset” (EUHFORIA). In order to validate our tool, we simulate an Earth-directed CME event on 2013 April 11 and compare the simulation results with the in-situ observations at 1 AU. Further, we assess the performance of EUHFORIA in forecasting of Bz, using different flux rope models like spheromak and torus.  The results obtained from this study help to improve our understanding to build the steppingstones towards the forecasting of Bz in near real time.

This research has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 870405 (EUHFORIA 2.0).
An Idealized Model of Ocean Gyres near Pine Island Ice Shelf and Thwaites Ice Shelf
Authors: Zheng Yixi , Stevens David , Heywood Karen , Webber Benjamin , Queste Bastien
Published: March 2021

Floating ice shelves buttress the Antarctic Ice Sheet, which is losing mass rapidly mainly due to oceanic melting and the associated disruption to glacial dynamics. The local oceanic circulation near ice shelves is therefore important for the prediction of future ice mass loss and related sea-level rise as it determines the water mass exchange, heat transport under the ice shelf, and the resultant melting. However, the dynamics controlling the near-coastal circulation are not fully understood, particularly relating to seasonal and interannual changes in wind stress curl and ice cover. A gyre circulation (27 km radius, cyclonic) in front of the Pine Island Ice Shelf has been identified in both numerical models and velocity observations. In 2019 in the west of Thwaites Ice Shelf, for the first time in this habitually ice-covered region, another gyre circulation rotating in a different direction (13 km, anticyclonic) was detected by velocity observations. Here we use an idealised configuration of MITgcm, with idealised forcing based on ERA-5 climatological wind fields and simplified sea ice conditions from MODIS satellite images, to reproduce key features of the observed gyres near Pine Island Ice Shelf and Thwaites Ice Shelf. A barotropic version of the model is able to reproduce the gyres driven solely by the wind. We show that the modelled gyre direction depends upon the angle between the wind direction and the sea ice front. Gyres generated by wind in sea-ice-free conditions have directions controlled by the wind stress curl. When sea ice is present, the wind stress exerted on the sea surface is reduced, leading to a modified wind stress curl and a resultant change in gyre direction.
The timing of deglaciation from mountain summits to cirques in Wales: 10Be and 26Al exposure dates from Cadair Idris
Authors: Hughes Philip , Glasser Neil , Fink David , Dortch Jason , Fülöp Reka , Wilcken Klaus , Fujioka Toshiyuki
Published: March 2021

Cosmogenic 10Be and 26Al exposure ages from 20 erratic samples collected from Cadair Idris (893 m), a mountain in southern Snowdonia, Wales, provide evidence for the timing of deglaciation from summits to cirques at the end of the Late Pleistocene. The summit of the mountain is characterised by intensely modified frost-shattered surfaces that have long been identified as a representing a former nunatak. Numerous glacially-transported quartz boulders on the highest ground indicate that ice overran the summit at some point in the Pleistocene. Two quartz boulders, one with preserved striations, sampled at c. 856 m near the summit of Cadair Idris yielded consistent 10Be and 26Al paired exposure ages of 75 ka to 60 ka (using a high-latitude sea level 10Be spallation production rate of 4.20 at/g/y, scaled by the Lal/Stone scheme). A glacially polished bedrock quartzite outcrop at 735 m gave an age of 17.5 ka. Immediately below this, cirque and down-valley recessional moraine ages, covering an elevation of 480 m to 350 m ranged from 10 to 15 ka respectively.

These results confirm that Cadair Idris was overridden by the Welsh Ice Cap during marine isotope stage (MIS) 4, when ice was thicker than at the global last glacial maximum (LGM) in MIS 2. This is consistent with findings from northern Snowdonia. The highest Welsh summits, including Cadair Idris, emerged above a thinning Welsh Ice Cap (British Irish Ice Sheet) during the transition from MIS 4 to 3. The summit area above ~800 m then stood as nunataks above the LGM ice sheet surface in MIS 2. The Welsh Ice Cap then rapidly thinned over Cadair Idris at ~20-17 ka based on ages from high-level ice-moulded bedrockThis is supported by more new ages from high-level paired erratics and bedrock samples on several other mountains throughout Snowdonia, leading to a phase of alpine-style deglaciation. Valley glaciers initiated their retreat up-valley from ~17 to 14 ka after Heinrich Event 1. A later phase of glacier stabilisation or still stand formation produced classic cirque moraines near the rim of a present cirque lake basin (480 m elevation) yielding 10Be ages of 13-10 ka during the Younger Dryas.
Are “ramblas” the sewerage of metal pollution in mining areas with a semi-arid climate?
Authors: Pérez-Sirvent Carmen , Martínez Sánchez Maria Jose , Martínez López Salvadora , Martínez Martínez Lucia Belén , Hernández Pérez Carmen , García Lorenzo Mari Luz , Hernández-Córdoba Manuel , Rodríguez Pedrosa María Teresa , Ros Castejón Raquel , Valero Espín Elia , Bech Jaume
Published: March 2021

 “Rambla”are temporary watercourses, which are characteristic of mediterranean and semi-arid climates, with low rainfall and sporadic torrential rain. A few times a year, when the rainfall exceeds 80 mm in less than an hour, they are capable of evacuating high flows of water mixed with particulate material of different granulometries to the sea.

The Sierra Minera of Cartagena (Murcia, Spain) has two marine slopes, one of short distance and steep slope towards the Mediterranean Sea, and another of a greater extent that affects the Mar Menor, a specially protected saltwater lagoon.

The processes that can take place in the course of the ramblas that begin in the Sierra Minera, when water is present, are those of transport of particulate and soluble material, processes of dissolution, hydrolysis, redox, complexation, carbonation and precipitation among others. When the rainy season ends and the Surface water disappears, the sediments that have been left in the riverbed are subject to other secondary processes that lead to the formation of very particular mineralogical species, efflorescence of hydrated sulphates, carbonates and oxydroxides. This is due to the pore water which can remain for a long period of time in the sediments of the rambla bed. Depending on the degree of influence of the current mining sediments in the rambla, the water it transports can have an acid pH (3.5-5.5), being qualified as acid mine drainage.

The Rambla del Beal is one of the various watercourses that cross the Sierra and flow into the Mar Menor next to a wetland that is an Special Protection Area (SPA), which makes the study more interesting. Like other ramblas in the area, during different periods, it carried the waste from the mineral floatation plants to the sea, as if it were a natural pipe, so along its route there are abundant terraces formed by this waste. This is in addition to the materials dumped and the materials eroded from the ponds and dumps that are in its receiving basin.

A selective sampling has been carried out along the riverbed to its mouth, analysing the content of potential toxic elements (PTEs), granulometry, general characteristics and mineralogy.

The bioavailability and mobility of the different PTEs (As, Pb, Zn, Cd and Fe) and their relationship with the mineralogy have also been studied.

The results show that only in the central part of the rambla can sediments not affected by primary pollution be found (they are secondary pollution), and that the Rambla del Beal itself can be considered a focus or primary source of pollution by PTEs.

 
Antarctic Peninsula warming triggers enhanced basal melt rates throughout West Antarctica
Authors: Thompson Andrew , Flexas Mar , Schodlok Michael , Speer Kevin
Published: March 2021

The acceleration of ice-shelf basal melt rates throughout West Antarctica, as well as their potential to destabilize the ice sheets they buttress, is well documented.  Yet, the mechanisms that determine both trends and variability of these melt rates remain uncertain.  Explanations for the intensification of melting have largely focused on local processes in seas surrounding the ice shelves, including variations in wind stress over the continental slope and shelf.  Here, we show that non-local freshwater forcing, propagated between shelf seas by the Antarctic Coastal Current (AACC), can have a significant impact on ice-shelf melt rates.  

We present results from a suite of high-resolution (~3-km) numerical simulations of the ocean circulation in West Antarctica that includes a dynamic sea-ice field, ice-shelf cavities and forcing from ice shelf-ocean interactions.  Motivated by persistent warming at the northern Antarctic Peninsula since the 1950’s, freshwater perturbations are applied to the West Antarctic Peninsula.  This leads to a strengthening of the AACC and a westward propagation of the freshwater signal.  Critically, basal melt rates increase throughout the WAP, Bellingshausen and Amundsen Seas in response to this perturbation.  The freshwater anomalies stratify the ocean surface near the coast, enhancing lateral heat fluxes that lead to greater ice-shelf melt rates.  A suite of sensitivity studies show that changes in meltrates are linearly proportional to the magnitude of the freshwater anomaly, changing by as much as 30% for realistic perturbations, but are relatively insensitive to the distribution of the perturbation across the WAP shelf.  These results indicate that glacial run-off on the Antarctic Peninsula, one of the first signatures of a warming climate in Antarctica, could be a key trigger for increased melt rates in the Amundsen and Bellingshausen Seas.
Handwashing and water security in the context of a pandemic
Authors: Hannah David M. , Lynch Iseult , Mao Feng , Miller Joshua D. , Young Sera L. , Krause Stefan
Published: March 2021

The COVID-19 pandemic is a wake-up call for water security issues. It makes us acutely aware how crucial access, and ability, for adequate hand hygiene are for reducing transmission risks of communicable diseases. An estimated 40% of households globally lack access to basic handwashing facilities. A recent cross-cultural study of household water insecurity experiences (HWISE) found that nearly one in four of 6,637 randomly sampled households across 23 sites in 20 low- and middle-income countries. Similar water, sanitation and hygiene problems impact on poorer families in high-income nations too.

We explore the challenge of hand hygiene in a changing water world and reflect on the importance of making rapid progress towards “ensure availability and sustainable management of water and sanitation for all” (UN Sustainable Development Goal 6). We contest that urgent action on water security is essential to better prepare societies for the future, including global health crises. Drawing on the latest evidence, we provide recommendations on how to increase handwashing, and improve human health and wellbeing more broadly, by reducing water insecurity. Across our world, policymakers must focus on: investment in water infrastructure, water independent alternatives, and behavioural change and knowledge promotion. Moreover, we must prioritise holistic, evidence-based solutions that address 3 facets of water (in)security: availability, quality & accessibility.
Updated Mapping of Hydrogen in the Lunar Southern Polar Regions according to LEND/LRO data
Authors: Sanin Anton , Mitrofanov Igor , Litvak Maxim
Published: March 2021

Determining the amount of water ice in the lunar regolith is an important task not only from a scientific point of view, but it is also important for exploration, since water may be used in many aspects - from the production of rocket fuel to direct use by astronauts during their stay on a habitable lunar base. One of the methods of remote sensing for hydrogen-bearing compounds, such as water ice, in the upper 1–2 m subsurface soil layer of atmosphereless celestial bodies is the spectroscopy of the neutron leakage flux from the surface. To estimate water equivalent hydrogen (WEH) in the lunar soil we have used data of Lunar Exploration Neutron Detector (LEND) aboard the Lunar Reconnaissance Orbiter (LRO), operating almost continuously in orbit around the Moon from 2009 to the present [1].

LEND is the collimated epithermal neutron telescope which uses the passive neutron collimator to collect most of neutron signal at a narrow field of view (FOV). Dataset gathered by LEND till April 1, 2015 was early used to estimate the water equivalent hydrogen (WEH) and create maps of its distribution [2]. After 5 years of additional data accumulation we update the WEH map in the Southern circumpolar region, including both large permanently shadow regions (PSRs) and neutron suppression regions (NSRs), which might be partially overlapping with PSRs and often extends on sunlit areas.

The updated map is done not only by the new larger dataset, but by new WEH estimation method also. This method uses precise estimation of the neutron flux at different altitudes of spacecraft orbits modelled with specially developed code based on the Geant4 toolkit with additional treatment of the neutron propagation in the lunar gravity field. Also, the method precisely accounts the fact of the collimator partial transparency, which leads to additional background counting rate in detectors dependent on WEH in the soil at surrounding regions located out of the instrument FOV. 

References:
1.    Mitrofanov I. et al. (2010) Space Sci. Rev., 150, 183–207.
2.    Sanin A. B. et al. (2017) Icarus, 283, 20-30.
Devastating hyper-concentrated flood on the Loess Plateau, China: simulations and implications
Authors: Zhang Ga , An Chenge , Fu Xudong
Published: March 2021

Yellow River has long been suffered from floods and sedimentation in the history, and has brought great catastrophes to the Chinese nation. Therefore, the Yellow River is also called the “China’s sorrow”. From July 25 to 26 of 2017, most of the northern part of the Shanxi and Shannxi Province in the middle Yellow River basin encountered high intensity rainfall with the maximum rainfall of 223.6 mm. In the abstract below, we term this rainfall event as the “7.26 storm”. After the extreme rainfall, hyper-concentrated floods occurred in the Dali River and Wuding River, which are tributaries of the Yellow River. The objective of this research is to study the hyper-concentrated floods of the Wuding River (with a drainage area of 28460 km2) at hourly time-step with a numerical model. The model that we utilized is the Digital Yellow River Model (DYRIM), which a physically based spatially distributed model of watershed sediment dynamics. Due to lack of sub-daily observation data, we first calibrate and verify the model at daily time-step. Then we apply the model to simulate the 7.26 storm at hourly time-step. Results show the DYRIM could well reproduce the peak discharge, peak sediment concentration, flood timing and volume, when compared with the measured data. Furthermore, the DYRIM is able to (1) delineate spatial distribution of hillslope erosion intensity, maximum erosion intensity could reach 10000 t/km2; (2) provide information about proportion of different sources of sediment, channel erosion is the main source of the sediment to the outlet and (3) analysis the influence of check-dams on flow and sediment, the dam trapped about 40 millions tons sediment, their effect on water and sediment reduction under extreme rainfall events is limited though.
Estimating soil hydraulic properties from saturation to complete dryness
Authors: Minasny Budiman , Rudiyanto Rudiyanto , Maggi Federico
Published: March 2021

To study the effect of drought on soil water dynamics, we need an accurate description of water retention and hydraulic conductivity from saturation to complete dryness. Recent studies have demonstrated the inaccuracy of conventional soil hydraulic models, especially in the dry end. Likewise, current pedotransfer functions (PTFs) for soil hydraulic properties are based on the classical Mualem-van Genuchten functions.

This study will evaluate models that estimate soil water retention and unsaturated hydraulic conductivity curves in full soil moisture ranges. An example is the Fredlund-Xing scaling model coupled with the hydraulic conductivity model of Wang et al. We will develop pedotransfer functions that can estimate parameters of the model. We will compare it with existing PTFs in predicting water retention and hydraulic conductivity.

The results show that a new suite of PTFs that used sand, silt, clay, and bulk density can be used successfully to predict water retention and hydraulic conductivity over a range of moisture content. The prediction of hydraulic properties is used in a soil water flow model to simulate soil moisture dynamics under drought. This study demonstrates the importance of accurate hydraulic model prediction for a better description of soil moisture dynamics.

 
Structural deformation-metamorphism and exhumation processes of Yuanmou metamorphic complex, Yunnan, China
Authors: Cheng Xuemei , Cao Shuyun
Published: March 2021

Within orogenic zone and continental extensional area, it often developed metamorphic complex or metamorphic gneiss dome that widely exposed continental mid-lower crustal rocks, which is an ideal place to study exhumation processes of deep-seated metamorphic complex and rheology. The Yuanmou metamorphic complex is located in the south-central part of the "Kangdian Axis" in the western margin of Qiangtang Block and Yangtze Block, which is a part of the anticline of the Sichuan-Yunnan platform. Many research works mainly focus on the discussion of intrusion ages, aeromagnetic anomalies, and polymetallic deposits. However, the exhumation process and mechanism of the Yuanmou metamorphic complex are rarely discussed and still unclear. This study, based on detailed field geological observations, optical microscopy (OM), cathodoluminescence (CL), electron backscatter diffraction (EBSD) and electron probe (EMPA) were performed to illustrate the geological structure features, deformation-metamorphic evolution process and its tectonic significance of Yuanmou metamorphic complex during the exhumation process. All these analysis results indicate that the Yuanmou metamorphic complex generally exhibits a dome structure with deep metamorphic rocks and deformed rocks of varying degrees widely developed. Mylonitic gneiss and granitic intrusions are located in the footwall of the Yuanmou, which have suffered high-temperature shearing. The mylonitic fabrics and mineral stretching lineations in the deformed rock are strongly developed, forming typical S-L or L-shaped structural features. The high-temperature ductile deformation-metamorphism environment is high amphibolite facies, that is, the temperature range is between 620 ~ 690 ℃ and the pressure is between 0.8 ~ 0.95 Gpa. In the deformed rocks closed to the detachment fault, some of the mylonite fabric features are retained, but most of them have experienced a strongly overprinted retrogression metamorphism and deformation. At the top of the detachment fault zone, it is mainly composed of cataclasites and fault gouge. The comprehensive macro- and microstructural characteristics, geometry, kinematics, and mineral (amphibole, quartz and calcite) EBSD textures indicate that the Yuanmou metamorphic complex has undergone a progressive exhumation process during regional extension, obvious high-temperature plastic deformation-metamorphism in the early stage, and superimposed of low-temperature plastic-brittle and brittle deformation in the subsequent stage, which is also accompanied by strong fluid activities during the exhumation process.
Incorporating observational errors in multivariate hydrologic model calibration: the value in known unknowns
Authors: Marshall Lucy
Published: March 2021

The latest generation of integrated hydrologic models provides new opportunities to better understand and hypothesize about the connections between hydrological, ecological and energy transfer processes across a range of scales. Parallel to this has been unprecedented growth in new technologies to observe components of Earth’s biophysical system through satellite remote sensing or on-the-ground instruments. However, along with growth in available data and advanced modelling platforms comes a challenge to ensure models are representative of catchment systems and are not unrealistically confident in their predictions. Many hydrologic and ecosystem variables are measured infrequently, measured with significant error, or are measured at a scale different to their representation in a model. In fact, the modelled variable of interest is frequently not directly observed but inferred from surrogate measurements. This introduces errors in model calibration that will affect whether our models are representative of the systems we seek to understand.

In recent years, Bayesian inference has emerged as a powerful tool in the environmental modeler’s toolbox, providing a convenient framework in which to model parameter and observational uncertainties. The Bayesian approach is ideal for multivariate model calibration, by defining proper prior distributions that can be considered analogous to the weighting often prescribed in traditional multi-objective calibration. 

In this study, we develop a multi-objective Bayesian approach to hydrologic model inference that explicitly capitalises on a priori knowledge of observational errors to improve parameter estimation and uncertainty estimation. We introduce a novel error model, which partitions observation and model residual error according to prior knowledge of the estimated uncertainty in the calibration data. We demonstrate our approach in two case studies: an ecohydrologic model where we make use of the known uncertainty in satellite retrievals of Leaf Area Index (LAI), and a water quality model using turbidity as a proxy for Total Suspended Solids (TSS). Overall, we aim to demonstrate the need to properly account for known observational errors in proper hydrologic model calibration.
Modeling the fate, transport and risk of Bisphenol A and N, N-diethyltoluamide in a tropical reservoir
Authors: Tong Xuneng , Zhang Jingjie , You Luhua , Gin Karina Yew-Hoong
Published: March 2021

The fate and transport of emerging contaminants in aquatic environments is a complex process, which is not only determined by their own properties but can also be influenced by the surrounding environment. In this study, a comprehensive modelling framework coupling a 3D hydrodynamic--emerging contaminants module was developed to describe the fate and transport of two representative emerging contaminants, namely Bisphenol A (BPA) and N, N-diethyltoluamide (DEET) in a tropical reservoir. First, the model was calibrated and validated with BPA and DEET obtained from a historical dataset (2013-2014) in bulk water, suspended solids, pore water and sediments phase. Results revealed that the simulation performance gave “excellent simulation” results with skill scores all larger than 0.90. Subsequently, the ecological risk assessment for the reservoir was conducted using the trophic state index (TSI) and coupled species sensitivity distribution (SSD)-Risk Quotient (RQ) method. The RQ values of the study area ranged from 0.003-0.068 (BPA) and 0.001-0.014 (DEET), respectively, which suggests that the levels of studied compounds BPA and DEET may pose low risk to the aquatic ecosystem. Finally, the indirect influence of general water quality parameters such as nutrients (phosphorous) on the multi-compartment distributions of emerging contaminants was explored. Our approach lays down a comprehensive framework to better understand the dynamics of fate and transport and their potential ecological risks of emerging contaminants as well as the indirect impact of other water quality parameters on their distributions in different phases in aquatic ecosystems.
Rising CO2 and warming lead to declining global canopy demand for nitrogen
Authors: Dong Ning , Prentice Iain Colin , Wright Ian , Luo Xiangzhong , Smith Nick
Published: March 2021

Nitrogen (N) limitation constrains the magnitude of terrestrial carbon uptake in response to CO2 fertilization and climate change. However, the trajectory of N demand, and how it is influenced by continuing changes in CO2 and climate, is incompletely understood. We estimate recent changes in global canopy N demand based on a well-tested optimality hypothesis for the control of photosynthetic capacity (Vcmax). The predicted global pattern of optimal leaf-level Vcmax is similar to the pattern derived from remotely sensed chlorophyll retrievals. Over the period from 1982 to 2015, rising CO2­ and warming both contributed to decreasing leaf-level N demand. Widespread increases in green vegetation cover over the same period (especially in high latitudes) imply increasing total canopy N demand. The net global trend is, nonetheless, a decrease in total canopy N demand. This work provides a new perspective on the past, present and future of the global terrestrial N cycle.
An adapted method to assess soil organic carbon stocks in a high mountain region: A LDN case study from Kirgistan
Authors: Korintenberg Margarete , Walter Judith , Märten Katja , Zeitz Jutta
Published: March 2021

The Sustainable Development Goals (SDGs) adopetd by the United Nations in 2016 include the SDG 15.3 „Land Degradation Neutrality (LDN)“, which aims to reduce land degradation by national efforts of the member states. Three indicators for land degradation were gloablly identified: landcover, land productivity and soil organic carbon stocks (SOC). In particular, the assessment of SOC is challenging in countries where (a) spatial digital data is largely missing and (b) SOC mapping is difficult due to remotness typical for high mountain regions . Global data provided by the Secretariat of the United Nations Convention to Combat Desertification (UNCCD) may be used for reporting, but experience from various countries indicates inaccuracies due to generalisation. This is especially the case for SOC. Moreover, to report on changes in SOC stocks, a comprehensive baseline is mandatory. In order to approach these challenges, Kirgistan, which has signed the SDG’s but still lacks a baseline for SOC, has been chosen for a case study.

In a multinational project we developed a scientifically based method to map and assess SOC stocks enabling a nationwide upscaling of SOC data (baseline). Using globally available data on landcover, elevation, climate and national soil data, „representative SOC units“ were identified prior to sampling. We assume that mainly these factors determine the spatial variability of SOC and that similar SOC stocks can be expected at comparable site conditions. More than 90% of the surface area, that potentially store SOC, is coverd by only 20 representative units, which were sampled 3-fold in the field. Sampling location within a single unit was determined using a drone to identify a representative location. Using the drone was especially helpful as sampling sites in a high mountain region were often extremely remote. During sampling small-scale variability of SOC was considered in the field. To determine SOC stocks, bulk density of the fine soil, coarse fragments and amount of roots were measured in the laboratory. Furthermore, pH, clay, silt and sand content were analysed to identify further drivers for SOC distribution.

Results show that spatial distribution of SOC in such a high mountain region is mainly controlled by landcover (cropland, grassland, forest), elevation, bulk density and clay content. Within single landcover classes topographic indices, such as aspect, further determine SOC distribution. This is especially the case for grassland, which is the dominant landcover in Kirgistan (53%). For the assessment of SOC stocks different approaches were compared. For instance, precise assessment of stocks using the bulk density of the fine soil corrected for coarse fragments leads to significantly lower SOC stocks when compared to the global data provided by the UNCCD.
Unravelling the origin of placer gold: A case study on the largest Roman gold mining sector of NW Spain (Jamuz, León)
Authors: Fernández-Lozano Javier , Esbrí José María , Garrido Ignacio , Carrasco Rosa María , Pedraza Javier , Bernardo-Sánchez Antonio , Higueras Pablo
Published: March 2021

NW Iberia hosts a substantial number of mineral resources. Among them, gold (Au) acquired particular relevance since Antiquity, representing one of the largest Roman Au mining provinces in Europe. While primary deposits associated with orogenic Au have been widely studied in the past years, the Plio-Quaternary Raña Au-bearing placer deposits of the western Duero Basin have received little attention. Besides, the different morphology of Au particles suggests complex processes that may have been responsible for the secondary formation of colloidal particles and Au growth grains from complex geochemical soil interactions and biological activity. In this context, exploring the mechanism by means these secondary deposits developed may contribute to understanding the source of Au (extrinsic or intrinsic factors that rule in within Raña deposits) and the formation of potential mineral exploration sectors. This paper outlines the geochemical analysis of a Cenozoic Raña-like deposit in the Jamuz valley (León), where the source of Au and the main characteristics are established. The correlation matrix showed notable relationships between Au, Fe, Na, K, Ca, Pb and As, among the most important. High values in Fe and As provides direct evidence of Au precipitation. Likewise, a non-linear correlation was found between Au-Na, and Au-Ca, suggesting a direct link to soil formation processes. Finally, the presence of apparent differences in grain roundness and the particles' characteristics ranging from monomineral angular Au to polymineral rounded-shaped particles points towards a complex process affecting the Raña deposits. The ubiquitous rubefaction and top-bottom leaching activity produced during rainwater percolation aided by the extreme drainage affecting this conglomeratic formation have often been argued to be responsible for the transformation of mineral phases in soils. The presence of secondary silicification processes and pH drop due to biological reactions (i.e., presence of P) may have been a triggering mechanism for digestion and reprecipitation of Au colloids in these sediments. Our results have outstanding implications on the mechanisms that may determine the Au enrichment of certain levels within the Raña deposits of the western Duero Basin.

This work was funded by the wine company “Fuentes del Silencio”.
Simulating hydrological processes with a fully coupled surface-subsurface model for estimating catchment travel times
Authors: Moussa Adnan , Klaus Julian , Sulis Mauro
Published: March 2021

How water and solute are transported in catchments is the foundation for sustainable water management. The flow and transport processes can be described through the travel time of water summarizing the catchment functions of storage, mixing, and release. For a catchment scale, travel time is defined as the time a water particle needs to travel from when it hits the ground surface until it leaves the catchment as discharge or evapotranspiration. Recent studies treated travel time distributions as time-variant in order to reflect the temporal and spatial variability of atmospheric forcing and corresponding hydrologic dynamics through the Master Equation and StorAge selection functions (SAS functions). A challenge is that travel times cannot be directly estimated from data but are inferred from either conceptual or physically based hydrological models. In our study, we employ the integrated surface-subsurface hydrological model Parflow to simulate water fluxes in the forested Weierbach catchment in Luxembourg. However, there are challenges on model parametrization and optimization to build a robust model that is representative of the catchments processes. Our objective here is to setup a robust model for Weierbach catchment based on available catchment parameters. We will evaluate the model against observed streamflow at several sites and soil moisture data. Nevertheless, such model can be used to reveal the spatio-temporal heterogeneity of the hydrological processes at our catchment once it is constrained with the available field data. Future work will consist of directly estimating the travel time of both discharge and evapotranspiration using Parflow and particle tracking (such as EcoSLIM) and will be constrained with the observed stable isotope data.
Chlorine-bearing species and the 37Cl/35Cl isotope ratio in the coma of comet 67P/Churyumov-Gerasimenko
Authors: Dhooghe Frederik , De Keyser Johan , Hänni Nora , Altwegg Kathrin , Cessateur Gaël , Jehin Emmanuel , Rubin Martin , Wurz Peter
Published: March 2021

A full-mission analysis of Cl-bearing species in the coma of comet 67P/Churyumov-Gerasimenko has been conducted using data from the Rosetta ROSINA/DFMS mass spectrometer. This contribution will focus on the challenges encountered to relate DFMS data on Cl-bearing species to the neutral abundances at the comet.

DFMS was operated in neutral mode, in which electron impact ionizes a fraction of the incoming neutral gas in the ion source. Only ions in a narrow range around a certain commanded mass-over-charge ratio (m/z) pass through the mass analyser at a time and impact on a micro-channel plate (MCP), creating an electron avalanche that is recorded by a Linear Electron Detector Array chip with two rows of 512 pixels each (LEDA A and LEDA B). Data are obtained as Analog-to-Digital Converter (ADC) counts as a function of LEDA pixel number. The instrument scans over a sequence of m/z values.

A well-defined approach exists to convert ADC counts as a function of pixel number to the number of ions that were detected on the MCP. However, to relate the number of ions detected this way to the abundance of neutrals in the coma gas, the sensitivity for each neutral needs to be known. The sensitivity for a certain neutral takes into account the total ionization cross section for the neutral and product ion fraction, instrument transmission and secondary electron yield for each product ion. Sensitivities can be determined experimentally by introducing the neutrals in the DFMS instrument copy in the laboratory, but such data are not available for Cl-bearing species and an alternative approach needs to be used. Fortunately, the use of ratios cancels out some of the factors that play a role in the sensitivity. As an example, for the 37Cl/35Cl ratio, total ionization cross sections and product ion fractions can be considered identical. In the case of 37Cl/35Cl, taking into account the sensitivity results in a correction of more than 15%, mainly due to the secondary electron yield.

The 37Cl/35Cl ratio does not appear to change appreciably throughout the mission and is compared with known values from other solar system objects. The Cl/HCl ratio obtained with DFMS indicates that there must be at least one additional chlorine-bearing species on the comet next to HCl, CH3Cl and NH4Cl, the identity of which is unknown at this time.