bluuebunny/crossref_metadata_2025 huggingface dataset:
Evolution of the crystallisation conditions in the Wellington Lake Pegmatite in the Pikes Peak Granite, Colorado (USA)
Authors: Fonseca Teixeira Ludmila Maria , Allaz Julien , Bachmann Olivier
Published: March 2021

Pegmatites are texturally, mineralogically, and geochemically zoned rocks that show distinctive features such as graphic granite in the wall zones, coarse-crystalline material in the centre, and unusual mineralisation sometimes of economic significance. They are usually considered to be derived from silicate melts, but a significant fluid supply is also required to reproduce their unique characteristics. These fluids are commonly enriched in flux anions such as F-, Cl-, CO32-, and BO33- . Many studies have investigated the petrogenetic processes that led to pegmatite crystallisation, yet not all aspects of pegmatite formation have been fully understood. Notably, the nature of the precipitating medium remains uncertain for the different zones of the pegmatite. In order to better understand the transition from a silicate-melt-dominated crystallisation to fluid-dominated precipitation, we aimed to produce a temperature profile across the pegmatite and its host granite. We analysed quartz crystals from the different zones of the Wellington Lake Pegmatite and the host rock, a syenogranite of the Pikes Peak Batholith, in Colorado (USA). This NYF-type pegmatite consists of a fine-grained graphic granite wall zone, a coarse-grained quartz and albite intermediate zone, and pure blocky quartz core zone with REE-dominated mineralisation including fluocerite, bastnäsite, thorite, columbite, zircon, and cassiterite. Quartz trace element data (Al, Ti, Ge) suggest that the granite crystallized over a range of conditions, with Ti-in-quartz temperatures varying from 800 to 550°C. The wall zone of the pegmatite crystallised over a more constricted range, with temperatures on the order of ~660 to 630°C, just below the experimentally determined H2O-saturated haplogranite solidus. Finally, the intermediate and core zones of the pegmatite show much colder conditions, with fluid inclusion homogenisation temperatures calibrated for typical pegmatite pressures ranging from 450°C (for 300 MPa) or 380°C (for 200 MPa) for the intermediate zone to 380°C (for 300 MPa) or 325°C (for 200 MPa) for the core. These results suggest crystallisation from a range of conditions transitioning from hydrous silicate melt-based mineral precipitation at the high temperature end (in the core of quartz crystals in the granite) to sub-solidus Al-Si-Na-enriched fluid precipitation in the interstitial quartz of the granite and in the pegmatite. Textural and geochemical zoning in the pegmatite records the transition from near-magmatic conditions in the borders to colder and more hydrothermal conditions in the core.

 
Delta Deposits on Mars: A Global Perspective
Authors: De Toffoli Barbara , Plesa Ana-Catalina , Hauber Ernst , Breuer Doris
Published: March 2021

The presence of delta deposits on Mars has been thoroughly demonstrated for decades and large scale mapping [1,2] highlighted the presence of several delta fans mainly located on the dichotomy boundary. While a previous delta inventory was compiled by Morgan et al. [3], we aim to update and finalize a complete mapping of delta deposits in order to allow the examination of the evolution and distribution of standing bodies of water on Mars. The objective of our project focuses on the production of a global catalogue of water-related features at the Martian surface, which are commonly studied separately or at smaller scales.

Globally, we located around 150 deltas among which many were not previously included in published literature [e.g. 1,2,4]. We then examined the deltas based on two main traits. Firstly, we measured the length of the feeding channels since it may be (i) a proxy for the duration of the aqueous activity in the channel-delta system, and (ii) proportional to the age of the delta [2]. The latter relationship links older deltas near Chryse Planitia (>3 Ga) to longer valleys, while younger deltas are usually fed by shorter valleys [2]. Secondly, we measured the elevation of the delta population and compared the obtained dataset with the hypothesized sea level elevation of -2540 ± 177 m firstly suggested by Di Achille and Hynek [1] for a northern ocean through the analysis of deltas.

We observed that, if the relationship between feeding channel length and delta age found for a sub-group of the population [2] is applicable as a rule of thumb to all deltas, many of the deposits have the potential to be Hesperian or Amazonian in age. They would thus be younger than the ocean that might have occupied the northern lowlands during the Noachian-Hesperian boundary period [1] and thus be unrelated to a global sea level range. In fact, less than half of the delta population is related to medium/long feeding channels (>30 km). Abundant pristine morphologies, both related to channels and deltas, also supports the hypothesis that part of the population is younger than Noachian. Additionally, the large variety of elevations where the deltaic deposits can be found and the very small amount of deltas included in the sea level elevation range proposed by Di Achille and Hynek [1] raise questions about the generation and environmental implications of these features, especially when seen at global scale.

 

[1] Di Achille, G. & Hynek, B. M., Nat. Geosci. 3, 459–463 (2010).

[2] Hauber, E. et al., J. Geophys. Res. E Planets 118, 1529–1544 (2013).

[3] Morgan, A. M., et al., Lunar Planet. Sci. Conf. (2018).

[4] Ori, G.G. et al., J. Geophys. Res. E Planets 105, 17629–17641 (2000).
Spatial variability in Karoo dolerites
Authors: Kotze Arnold , Roberts R. James
Published: March 2021

AD Kotze and RJ Roberts

Department of Geology, University of Pretoria, Hatfield, Pretoria, South Africa; u04541686@tuks.co.za

The Karoo Large Igneous Province (KLIP) in South Africa consists of both a spatially limited extrusive basalt suite (Drakensberg Group) and a spatially extensive dolerite suite, both generally considered to be remarkable homogenous and of a “low-Ti” character (Luttinen, 2018). The homogeneity of the rocks requires that statistical analysis is necessary to look for spatial and geochemical trends in the data, which may yield clues to the mantle processes producing the 60 000 km2 expanse of basaltic magma. In this project, data derived from several locations are used as proxies to check for lateral variability in the Karoo dolerites. A principal component analysis (PCA) on trace element data using a covariance matrix was performed, and comparisons based on variables that are 1) common to the Karoo dolerites and Lesotho basalts and, 2) responsible for the most amount of variation to the data set are made. Trace element modelling is then used to test different mantle melting scenarios possibly responsible for the variation seen in the dolerites.

Principal component analyses revealed several trace elements are responsible for most of the variability in the dolerites. Cr and Ni has the strongest positive loading on Component 1 whereas Cr and Ba has the strongest positive loading on Component 2. Ba has a strong negative loading on Component 1. Cu, Sr, V and Zr do impart an appreciable amount of variation to the data, but all four variables have weak negative loadings on both components. Interestingly, the activity of Cu and V seems to be the inverse of that of Cr and Ni.

Due to the nature of a PCA, this work is afforded an opportunity to place the geochemistry of the Karoo dolerites within a larger geodynamic context without bias. From the observed variation, the activity of Ba and Cr is interpreted as an assimilation-oxidation process, whereas the Ni signature reflects the mantle origin of the magmas. Further modelling of these processes will allow the testing of suggested mechanisms for the formation of the KLIP, especially whether the magmatism is plume-related or related to the foundering of crustal blocks.

Luttinen, A., 2018. Bilateral geochemical asymmetry in the Karoo large igneous province. Scientific Reports, 8(5223).
The shape and infill of the Basadingen overdeepened glacial valley from P-wave seismic reflections
Authors: Brandt Anna-Catharina , Tanner David C. , Buness Hermann , Burschil Thomas , Gabriel Gerald
Published: March 2021

Overdeepened valleys in the Alps allow to probe the glacial sedimentation record, which in turn can illuminate the climatic history. In particular, seismic reflections can be used to extend punctual borehole data (for instance a number of boreholes are to be drilled into Alpine glacial overdeepened valleys as part of the DOVE ICDP project) in the second dimension or even survey a region before drilling begins. Thus, we use detailed, 2-D seismic P-wave profiles to reveal the shape and infill of an overdeepened Rhine glacier valley in the area of Basadingen, near to the German/Swiss border. We acquired two profiles nearly perpendicular to the valley strike, approximately 500 m apart. The first profile was 1246 m long, and consisted of a single spread of 624 geophones. The second profile was 1120 m long and was acquired using 200 3-component geophones using a roll-along method. For both profiles we used a vibro-source with a 12 s linear sweep of 20-240 Hz at every second geophone (two metre spacing), which produced a high fold.

Both seismic images reveal that the overdeepened basin at this location is asymmetrical and circa 260 m deep, although the deepest part (220 m wide) covers only a small portion of the broader main valley. The infill is characterised by at least three unconformities and distinct onlap and erosive boundaries between the sedimentary units. We interpret the infill to represent a highly dynamic sedimentary system. The lower part, within the deepest part of the basin is filled with chaotic sediments and slumping. Above a major unconformity, the upper part contains strongly-dipping reflectors that probably represent a prograding point-bar in a glacio-fluviatile environment that migrated toward the north-east. Beneath the deepest part of the basin we see evidence for faults in the Tertiary Molasse basement, which correlate with known faults at the surface. The faults most likely caused the valley to be sited at this location and they were probably also the cause of the ‘valley in valley’ shape.

A new DOVE research borehole will be drilled in the centre of the valley in 2021. This will bring more light on the sedimentary history and OSL-dating of the material will bracket the timing of the infill.
Statistical Distribution of Bifurcation of Earth's Inner Energetic Electron Belt at tens of keV
Authors: Hua Man , Ni Binbin , Li Wen , Ma Qianli , Gu Xudong , Fu Song , Cao Xing , Guo Yingjie , Liu Yangxizi
Published: March 2021

The Earth’s inner energetic electron belt typically exhibits one-peak radial structure with high flux intensities at radial distances < ~2.5 Earth radii. Recent studies suggested that human-made very-low-frequency (VLF) transmitters leaked into the inner magnetosphere can efficiently scatter energetic electrons, bifurcating the inner electron belt. In this study, we use 6-year electron flux data from Van Allen Probes to comprehensively analyze the statistical distributions of the bifurcated inner electron belt and their dependence on electron energy, season, and geomagnetic activity, which is crucial to understand when and where VLF transmitters can efficiently scatter electrons in addition to other naturally occurring waves. We reveal that bifurcation can be frequently observed for tens of keV electrons under relatively quiet geomagnetic conditions, typically after significant flux enhancements that elevate fluxes at L = 2.0 – ~2.5 providing the prerequisite for the bifurcation. The bifurcation typically lasts for a few days until interrupted by substorm injections or inward radial diffusion. The L-shells of bifurcation dip decrease with increasing electron energy, and the occurrence of bifurcation is higher during northern hemisphere winter than summer, supporting the important role of VLF transmitter waves in energetic electron loss in near-Earth space.
Geomorphological evolution of ephemeral rivers through historical and UAVs images
Authors: Ibisate Askoa , Ollero Alfredo , García J. Horacio , Ortiz Martínez de Lahidalga Josu , Sáenz de Olazagoitia Ana , Hermoso Yilena , Conesa-García Carmelo , Gómez-Gutiérrez Alvaro
Published: March 2021

Ephemeral rivers hydromorphological processes are intermittent and many times of fast response. Therefore they remain still quite unknown. The geomorphological mapping of river forms and geomorphological units is a useful tool to recognize the evolution, changes and the response of river adjustments of hydrological events.

A diachronic geomorphological mapping has been done in some ephemeral rivers located in Ebro basin, Segura basin and Calabrian ephemeral rivers. We are presenting the specific results of six reaches distributed by the Ebro basin (Tudela, Reajo, Alpartir, Cariñena, Valcodo, Sosa and Seco). The first historical aerial image is that of the American Flight B of 1956-57, another of the mid 80’s, the last official ortophotography available (around 2017), and a specific flight with an unmanned aerial vehicle (UAV) done during the winter of 2019. An altimetry correction has been performed on the first two images.

Different categories have been identified within the channel (active channel, principal channel and secondary channel), the sediment bars (vegetated, scant vegetated and non-active paleo-bars), the deposits coming from bank failures or tributaries, rocky areas, exhumed old sediment areas, consolidated or unconsolidated granular bed. The categories were mapped at different scales depending on the image quality (for example, from ≤ 1/300 scale of the UAV to ≤ 1/1,000 scale of the American flight).

This evolutionary cartography allows comparing the geomorphology of each river reach among different dates, considering the different resolution of the images and its limitations (i.e. previously, the results were unified to compare among them), and relating to the fluvial processes and changes on the river and basin.

This research was funded by ERDF/Spanish Ministry of Science, Innovation and Universities—State Research Agency (AEI) /Project CGL2017-84625-C2-1-R; State Program for Research, Development and Innovation Focused on the Challenges of Society. 
An Alternative Machine Learning-Based Methodology for H-SAF H35 Fractional Snow Cover Product
Authors: Kuter Semih , Aksu Cansu , Bolat Kenan , Akyurek Zuhal
Published: March 2021

The fractional snow cover (FSC) product H35 is a daily operational product based on multi-channel analysis of AVHRR onboard to NOAA and MetOp satellites. H35 is supplied by the European Organization for the Exploitation of Meteorological Satellites (EUMETSAT) Satellite Application Facility on Support to Operational Hydrology and Water Management (HSAF). The “traditional” H35 FSC product is generated at pixel resolution by exploiting the brightness intensity, which is the convolution of the snow signal and the fraction of snow within the pixel and the sampling is carried out at 1-km intervals. The product for flat/forested regions is generated by Finnish Meteorological Institute (FMI) and the product for mountainous areas is generated by Turkish State Meteorological Service (TSMS). Both products, thereafter, are merged at FMI. This presentation aims to represent the latest findings of our efforts in developing an “alternative” H35 FSC product for the mountainous part by using two data-driven machine learning methodologies, namely, multivariate adaptive regression splines (MARS) and random forests (RFs). In total, 332 Sentinel 2 images over Alps, Tatra Mountains and Turkey acquired between November 2018 and April 2019 are used in order to generate the necessary reference FSC maps for the training of the MARS and RF models. AVHRR bands 1-5, NDSI and NDVI are used as predictor variables. Binary classified Sentinel 2 snow maps, ERA5 snow depth and MODIS MOD10A1 NDSI data are employed in the validation of the models. The results show that both MARS- and RF-based H35 product are i) in good agreement with reference FSC maps (as indicated by low RMSE and relatively high R values) and ii) able to capture the spatial variability of the snow extend. However, MARS-based H35 is preferred for an operational FSC product generation due to the high computational cost required in RF model.
Curie depth point, effective elastic thickness, and 3-D crustal structure of Eastern Indian shield based on the interpretation of satellite gravity (GOCE) and aeromagnetic data.
Authors: Arasada Rama Chandrudu , Gangumalla Srinivasa Rao
Published: March 2021

Eastern Indian shield comprises rocks that well persevered the Archean to the Proterozoic history of the earth. However, the lithospheric evolution of the region is poorly understood due to the scanty of seismological observations. In the presented study, an integrated approach is adopted to analyze the satellite gravity (GOCE), aeromagnetic, and topography data complemented with seismological constraints to understand the thermal evolution of the region. Wavelet based Bouguer-topography coherence method was used to compute spatial variations of effective elastic thickness (Te) in the region. We noticed high Te values of 27-31 km over EGMB and low to moderate Te values of 22-30 km over SC and CGGC. Results of 3-D forward gravity modeling of Complete Bouguer anomalies show that the Moho boundary lies at a depth of 35-38 km below the Eastern Ghats Mobile Belt (EGMB) and 38-40 km below Singhbhum Craton (SC), and it increases gradually towards the Chotanagpur granite gneiss complex (CGGC) to a depth of 40-44 km. Curie depth point (CDP) values obtained based on the spectral analysis of aeromagnetic data range from 25-30 km beneath the EGMB, 23-26 km over SC, and 30-36 km beneath the CGGC. Further comparison of CDP values with Moho depths (35-44 km) from 3-D forward gravity modeling and available deep seismic sounding/receiver function data in this region indicate that CDP values are shallower than the Moho. Unlike other cratonic regions, the shallowest CDP and low Te values observed over the Eastern Indian Shield suggests thermal reworking of the cratonic lithosphere in this region.
RS41 GRUAN Data Product Version 1 (RS41-GDP.1) - Reference Radiosonde Data for the Troposphere and Lower Stratosphere
Authors: Sommer Michael , von Rohden Christoph , Simeonov Tzvetan , Dirksen Ruud
Published: March 2021

One of the main goals of the GCOS Reference Upper Air Network (GRUAN) is to perform reference observations of profiles of atmospheric temperature, humidity and wind for monitoring climate change. Two essential criteria for establishing a reference observation are measurement-traceability and the availability of measurement uncertainties. Radiosoundings have proven valuable in providing in-situ profiles of temperature, humidity, pressure and wind at unmatched vertical resolution. Data products from commercial radiosondes often rely on black-box or proprietary algorithms, which are not disclosed to the scientific user. Furthermore, long-term time-series from these products are frequently hampered by changes in the hardware and/or the data processing.

The GRUAN data products (GDP’s) comply with the above-mentioned criteria for a reference product. Correction algorithms are open-source and well documented and the data include vertically resolved best estimates of the uncertainties. Another major advantage of a GRUAN data product is that it includes the radiosonde’s raw measurement data, which allows for reprocessing when new or improved corrections become available. Currently, GDP’s are available for the Vaisala RS92 and Meisei RS-11G radiosondes. Data products for additional radiosonde models, as well as for other measurement techniques are in the making. The GDP’s are used to determine trends, constrain and calibrate data from more spatially‐comprehensive observing systems (including satellites and current radiosonde networks), and provide appropriate data for studying atmospheric processes.

This presentation introduces the GRUAN processing of Vaisala RS41 radiosoundings, the correction algorithms that are applied, and the derivation of the vertically resolved uncertainty estimates. Well-known, dominant error sources for the RS41 profiles are related to solar radiation, causing a temperature error, and time-lag of the humidity sensor at low temperatures. The corrections for these error sources are based on dedicated experiments that were performed at Lindenberg observatory to measure the response of the RS41 temperature sensor to solar irradiance and to determine the time-lag of the humidity sensor at temperatures down to -70 °C. The RS41-GDP.1 is planned to become available in 2021. The majority of the 30, globally distributed, GRUAN sites employ the RS41, and its predecessor the RS92 before, establishing a continuous data record of more than 10 years of reference climate observations.
First results from coupling the Parallel Ice Sheet Model with the Modular Ocean Model via an Antarctic ice-shelf cavity module
Authors: Kreuzer Moritz , Reese Ronja , Huiskamp Willem , Petri Stefan , Albrecht Torsten , Feulner Georg , Winkelmann Ricarda
Published: March 2021

The past and future evolution of the Antarctic Ice Sheet is largely controlled by interactions between the ocean and floating ice shelves. To investigate these interactions, coupled ocean and ice sheet model configurations are required. Previous modelling studies have mostly relied on high resolution configurations, limiting these studies to individual glaciers or regions over short time scales of decades to a few centuries. To study global and long term interactions, we developed a framework to couple the dynamic ice sheet model PISM with the global ocean general circulation model MOM5 via the ice-shelf cavity module PICO. Since ice-shelf cavities are not resolved by MOM5, but parameterized with the box model PICO, the framework allows the ice sheet and ocean model to be run at resolution of 16 km and 3 degrees, respectively. We present first results from our coupled setup and discuss stability, feedbacks, and interactions of the Antarctic Ice Sheet and the global ocean system on millennial time scales.
Dunes as palaeo-wind vanes: Investigating palaeowind regimes using semi-automated remote sensing approaches to dunefield mapping and orientation quantification 
Authors: Nowatzki Maike , Fitzsimmons Kathryn , Harder Hartwig , Rosner Hans-Joachim
Published: March 2021

Many dryland regions of the world are at high risk of desertification from combined human land use and anthropogenic climate change. One symptom of desertification is the reactivation of previously stable dunefields. Since morphologies of stable dunes are thought to reflect wind regimes at the time of their formation, the degree to which dune orientation reflects modern winds may be one way to assess changes in wind regimes and the progression of desertification in a region.

Here we investigate the relationship between wind dynamics and desert dune orientation in one region at risk of desertification, southeast Kazakhstan in Central Asia, on the basis of open-source software and open-access datasets. Using Google Earth Engine, we map dunes or interdune spaces within six palaeo-dunefields in the Ili-Balkhash area, by performing a multi-layer object-based image analysis (OBIA) on satellite remote sensing data (Sentinel-2 optical imagery and SRTM digital elevation models). A semi-automated GIS approach is used to undertake data cleansing and the quantification of dominant palaeo-dunefield orientations. The resulting orientation trends are concurrent with the region’s topography: The dunefields within the Ili valley show a narrow, mostly E-W oriented trend concurrent with the course of the valley while the orientation ranges become broader towards the open pre-Balkhash area.

We then predict modern dune orientations by applying the maximum gross bedform-normal transport rule on reanalysed wind data for 2008-2018. This approach by Rubin and Hunter (1987) allows the deduction of sand transport and resulting bedform trends from wind direction frequencies. The predicted modern orientation trends for the dunefields in the Ili-Balkhash area yield only partial consensus with observed palaeo-bedform trends. We therefore propose that modern wind regimes are not exclusively responsible for existing dune morphologies in the region, and that dune orientation may be inherited from earlier wind regimes.
A unified framework for computational microstructure-based snow mechanics
Authors: Blatny Lars , Löwe Henning , Wang Stephanie , Gaume Johan
Published: March 2021

The effective mechanical behavior of snow can be deduced from microstructural homogenization through numerical simulations. Although such numerical upscaling of elasticity and strength of snow microstructures is standard (using FEM), numerical schemes to study generic features of the transition from small to large strain situations that involve yielding and failure are scarce. This prevents the development of accurate homogenized constitutive models valid for the post-failure and large deformation regimes. It has been shown that treating this transition is feasible using DEM under the assumption of particulate microstructures. However, this requires snow microstructures to be segmented into a granular collection of (usually spherical) cohesive elements. Here, we suggest generating random porous microstructures by level-cutting Gaussian random fields and using the material point method to numerically simulate them under mechanical loading. This allows investigating both small and large deformation characteristics of irregular porous media, such as snow, where a segmentation into grains and bonds can be ambiguous. We demonstrate our approach by examining elasticity and failure as a function of a wide range of solid volume fractions, from 20% (low-density snow) to 80% (high-density firn), as the most important control on the mechanical behavior. Observing that onset of failure can be well described through the second order work, we show that the failure strength follows a power law similar to that of the elastic moduli. Moreover, we propose that the failure envelope can be approximated by a porosity-dependent quadratic curve in the space of the two first stress invariants. Furthermore, we observe that plastic deformation appears to be governed by an associative plastic flow rule. Finally, these results combined with a viscoplastic Perzyna model and a sintering (hardening) model should allow us to develop a universal homogenized snow constitutive model.
Modeling of snow avalanche dynamics using open source software OpenFOAM
Authors: Romanova Daria , Egiit Margarita
Published: March 2021

The work is devoted to the comparison of different approaches for modeling the dynamics of dense and powder snow avalanches. Various 3D and 2D approaches are considered. The accuracy of determining the avalanche run-out zone, the interaction of the flow with obstacles, the front speed, and various distributed parameters are evaluated. As objects for comparison, an experiment on the interaction of a slushflow with a combination of protective structures and a powder snow avalanche in the Khibiny mountains are modeled.

 

Taking into account the advantages and disadvantages of various approaches based on basic solutions available in the OpenFOAM package, a specialized software avalancheFoam is being developed for three-dimensional modeling of the dynamics of snow avalanches, taking into account the complex turbulent regime and multiphase structure of the flow. Machine learning techniques are used to refine turbulent stresses. The neural network is trained on a dataset obtained from high-precision supercomputer simulation of the flow, and sets the form of additional refinement members of the mathematical model of less computational complexity. Various avalanche sites in the Khibiny mountains are modeled to validate the developed software.
Seasonal mixed layer heat budget in coastal waters off Angola
Authors: Körner Mareike , Brandt Peter , Dengler Marcus
Published: March 2021

The Angolan shelf system represents a highly productive ecosystem that exhibits pronounced seasonal variability. Productivity peaks in austral winter when seasonally prevailing upwelling favorable winds are weakest. Thus, other processes than local wind-driven upwelling contribute to the near-coastal cooling and nutrient supply during this season. Possible processes that lead to changes of the mixed-layer heat content does not only include local mechanism but also the passage of remotely forced coastally trapped waves. Understanding the driving mechanism of changes in the mixed-layer heat content that may be locally or remotely forced are vital for understanding of upward nutrient supply and biological productivity off Angola. Here, we investigate the seasonal mixed layer heat budget by analyzing atmospheric and oceanic causes for heat content variability. We calculate monthly estimates of surface heat fluxes, horizontal advection from near-surface velocities, horizontal eddy advection, and vertical entrainment. Additionally, diapycnal heat fluxes at the mixed-layer base are determined from shipboard and glider microstructure data. The results are discussed in reference to the variability of the eastern boundary circulation, surface heat fluxes and wind forcing.
Crustal structure, seasonal and directional variations of ambient seismic noise in SE Canada and the NE USA
Authors: Bagherpur Mojaver omid , Darbyshire Fiona
Published: March 2021

Long-duration stacks of ambient seismic noise cross-correlation can be used to generate high-resolution images of the lithosphere. In this study, we investigate the crustal structure beneath southeastern Canada and the northeastern USA, using an ambient noise tomography technique. Our study area covers the Phanerozoic northern Appalachians and the Proterozoic eastern Grenville Province, recording a complex tectonic history since ~1 Ga. Our datasets include continuous records of vertical component time series, recorded by 69 stations belonging to 7 seismograph networks over a more than two-year period. The ambient seismic noise directionality and seasonality variations of our datasets are analyzed in detail, and possible noise source locations are proposed in the Atlantic and Pacific oceans. Our analysis suggests strong variations of dominant seismic noise sources at both Primary (11-20 s) and Secondary (5-10 s) bands in various months, with different observed patterns at these passband periods. Our tomographic models indicate complex and strong variations of Rayleigh wave phase velocities across the study area, providing us evidence to discuss tectonic implications. The resulting Rayleigh wave phase velocity maps suggest generally slower velocities beneath the Appalachians than the Grenville province. A sharp velocity contrast is observed across the Grenville Province-Appalachian domain boundary at periods sensitive to the lower crust, suggesting a step-like geometry of the Moho interface beneath this area.
Petrological microscopy data workflow – an example from Cap de Creus, NE Spain
Authors: Wessels Richard , Kok Thijmen , van Melick Hans , Drury Martyn
Published: March 2021

Publishing research data in a Findable, Accessible, Interoperable, and Reusable (FAIR) manner is increasingly valued and nowadays often required by publishers and funders. Because experimental research data provide the backbone for scientific publications, it is important to publish this data as FAIRly as possible to enable reuse and citation of the data, thereby increasing the impact of research.

The structural geology group at Utrecht University is collaborating with the EarthCube-funded StraboSpot initiative to develop (meta)data schemas, templates and workflows, to support researchers in collecting and publishing petrological and microstructural data. This data will be made available in a FAIR manner through the EPOS (European Plate Observing System) data publication chain (https://epos-msl.uu.nl/).

The data workflow under development currently includes: a) collecting structural field (meta)data compliant with the StraboSpot protocols, b) creating thin sections oriented in three dimensions by applying a notch system (Tikoff et al., 2019), c) scanning and digitizing thin sections using a high-resolution scanner, d) automated mineralogy through EDS on a SEM, and e) high-resolution geochemistry using a microprobe. The purpose of this workflow is to be able to track geochemical and structural measurements and observations throughout the analytical process.

This workflow is applied to samples from the Cap de Creus region in northeast Spain. Located in the axial zone of the Pyrenees, the pre-Cambrian metasediments underwent HT-LP greenschist- to amphibolite-facies metamorphism, are intruded by pegmatitic bodies, and transected by greenschist-facies shear zones. Cap de Creus is a natural laboratory for studying the deformation history of the Pyrenees, and samples from the region are ideal to test and refine the data workflow. In particular, the geochemical data collected under this workflow is used as input for modelling the bulk rock composition using Perple_X.    

In the near future the workflow will be complimented by adding unique identifiers to the collected samples using IGSN (International Geo Sample Number), and by incorporating a StraboSpot-developed application for microscopy-based image correlation. This workflow will be refined and included in the broader correlative microscopy workflow that will be applied in the upcoming EXCITE project, an H2020-funded European collaboration of electron and x-ray microscopy facilities and researchers aimed at structural and chemical imaging of earth materials. 
Data quality of Aeolus wind measurements
Authors: Krisch Isabell , Reitebuch Oliver , von Bismarck Jonas , Dabas Alain , Fischer Peggy , Huber Dorit , de Kloe Jos , Rennie Michael ,   Aeolus DISC
Published: March 2021

The European Space Agency (ESA)’s Earth Explorer Aeolus was launched in August 2018 carrying the world’s first spaceborne wind lidar, the Atmospheric Laser Doppler Instrument (ALADIN). ALADIN uses a high spectral resolution Doppler wind lidar operating at 355nm to determine profiles of line-of-sight wind components in near-real-time (NRT). ALADIN samples the atmosphere from 30km altitude down to the Earth’s surface or to the level where the lidar signal is attenuated by optically thick clouds.

The global wind profiles provided by ALADIN help to improve weather forecasting and the understanding of atmospheric dynamics as they fill observational gaps in vertically resolved wind profiles mainly in the tropics,  southern hemisphere, and over the northern hemisphere oceans. Since 2020, multiple national and international weather centres (e.g. ECMWF, DWD, Météo France, MetOffice) assimilate Aeolus observations in their operational forecasting. Additionally, the scientific exploitation of the Aeolus dataset has started.

A main prerequisite for beneficial impact and scientific exploitation is data of sufficient quality. Such high data quality has been achieved through close collaboration of all involved parties within the Aeolus Data Innovation and Science Cluster (DISC), which was established after launch to study and improve the data quality of Aeolus products. The tasks of the Aeolus DISC include the instrument and platform monitoring, calibration, characterization, retrieval algorithm refinement, processor evolution, quality monitoring, product validation, and impact assessment for NWP.

The achievements of the Aeolus DISC for the NRT data quality and the one currently available reprocessed dataset will be presented. The data quality of the Aeolus wind measurements will be described and an outlook on planned improvements of the dataset and processors will be provided.
Modeling of ocean wave propagation across the crevasse-ridden ice shelf: focus on the comparison of two models
Authors: Konovalov Yuri
Published: March 2021

The propagation of high-frequency elastic-flexural waves through an ice shelf was modeled by a full 3-D elastic models. These models based on the momentum equations that were written as the differential equations (model#1) and as the integro-differential equations (model#2). The integro-differential form implies the vertical integration of the momentum equations from the ice surface to the current coordinate z like, for instance, in the Blatter-Pattyn ice flow model. The sea water flow under the ice shelf is described by the wave equation. The numerical solutions were obtained by a finite-difference method. Numerical experiments were undertaken for a crevasse-ridden ice shelf with different spatial periodicities of the crevasses. In this research the modeled positions of the band gaps in the dispersion spectra dependently on the spatial periodicities of the crevasses is investigated from the point of view of agreement of these positions with the Bragg’s law. The investigation of the dispersion spectra shows that different models reveal different sensitivities of the dispersion spectra (in relation to the appearance of the band gaps in the spectra) dependently on the spatial periodicity of the crevasses and on the crevasses depth.
Modelling the Moho depth and Flexure parameters across the Indo-Burma subduction zone.
Authors: Biswas Anirban , Gangumalla Srinivasa Rao
Published: March 2021

Indo-Burma subduction zone is one of the seismically active regions in India where the Indian plate is underthrusting the Burmese arc. However, the nature of the slab subduction in this region and its associated stress-regime are less understood due to the lack of deep crustal information. In the present study, we analyze the vertical gravity component of the Gravity Field and Steady-State Ocean Circulation Explorer (GOCE) and topography data to model the Moho depth interface and flexure parameters of the Indo-Burmese subduction region. Here, Moho depths are obtained by performing the non-linear gravity inversion using tesseroids in spherical coordinates. It is observed that the Moho interface in the Bay of Bengal (Indian plate) lies at a depth of 20-30 km and then deepens to a depth of 50-60 km towards the Burmese region. Beneath the Shan Plateau, Moho depth varies gently from 35 to 40 km and shows an eastward dip at Sagaing fault.  We also constructed eight profiles across the subduction zone to model the flexure parameters such as effective elastic thickness (Te), forebulge, and bending moments (Mo). The modelling results indicate that both Te (15-55 km) and Mo (1.12×10-19 to 2.84×10-19 N.m) values vary significantly along the subduction zone and show correlation with slab depth. Larger values of Te (55 km) and Mo (2.84×10-19 N.m) are noticed in the central Indo-Burmese subduction zone, where the slab depth is around 110-120 km. Whereas the lowest values of Te (15 km) and Mo (1.12×10-19 N.m) are inferred for the profiles lying in the southern Indo-Burmese subduction.
Coupling meteorological forecasts with hydrologic and hydraulic models: The Itaipu Dam ensemble inflow forecasting system
Authors: Quevedo José , Firmo Kazay Daniel , Maria Werlang Mariana , Gomes Giovanni , Takahashi Roberto , Zaicovski Marcelo , Villanueva Aguero Tannia , Fariña Jara José Maria
Published: March 2021

This work presents the development of the inflow ensemble forecasting system for Itaipu Dam. The system is based on combination of twelve Quantitative Precipitation Forecast (QPF) with three hydrological models and one hydrodynamic one-dimensional model. The QPF are provided by different meteorological institutions based in the results of the global Numerical Weather Prediction (NWP) models GFS and ECMWF, as well as of the regional NWP models WRF and COSMO executed by the Brazilian and Paraguay meteorological services (SIMEPAR, INMET and DINAC). The semi-distributed model MGB – Large Basin Model, the lumped models SMAP and HEC-HMS are considered as the hydrological models. Furthermore, the computed flows are propagated in a HEC-RAS scheme designed with extensive field data from bathymetry of Parana River and tributaries. The daily results are presented as fifteen inflow scenarios that are considered for the definition of a unique flow forecast. Finally, that forecast is used for the electric generation scheduling of the power plant. Each of these fifteen methods performance was evaluated as well as the suitability of the system for it purposes. For a short-term forecast horizon (less than 4 days), the performances of the hydrological models forced by the different rain forecast are quite similar. However, it is remarkable the difference between the results of the three hydrological models for the same horizon. On the other hand, for medium-term horizon (more than 4 days) both hydrological and meteorological models have diverse behavior and contribute for a wide representation of the possible scenarios. Overall, it has been showed that the simulations are complementary and provides to the forecaster a general overview of the hydrologic situation. Nevertheless, at this moment, further analysis of accuracy and reliability of the prediction have not been realized, so the forecaster needs to appeal to its own expertise to assure the consistence of the scenarios for decision-making.
Retrieving freeze/thaw-cycles using Sentinel 1 data in Eastern Nunavik (Québec, Canada)
Authors: Chen Yueli , Wang Lingxiao , Bernier Monique , Ludwig Ralf
Published: March 2021

In the terrestrial cryosphere, freeze/thaw (FT) state transitions play an important and measurable role for climatic, hydrological, ecological, and biogeochemical processes in permafrost landscapes. Satellite active and passive microwave remote sensing has shown its principal capacity to provide effective monitoring of landscape FT dynamics. Sentinel-1 continues to deliver high-resolution microwave remote sensing than ever before and has therefore a large potential of usage for monitoring. In light of this, the capability and responses of its radar backscatter to landscape FT processes in different surface soil depths should be examined to provide a thorough grounding for a robust application of the F/T retrieval algorithm.

This study presents a seasonal threshold approach, which examines the time series progression of remote sensing measurements relative to signatures acquired during seasonal reference frozen and thawed states. It is developed to estimate the FT-state from the Sentinel 1 database and applied and evaluated for the region of Eastern Nunavik (Québec, Canada). In this course, the FT state transitions derived from Sentinel 1 data are compared to temporally overlapping situ measurements of soil moisture from different depths within the top 20cm soil. This work allows to explore differences in the sensitivity of the Sentinel 1 at different surface soil depths in higher detail; this information is used to examine the penetration performance of the Sentinel 1 under different conditions of permafrost and permafrost-dominated landscapes.

This work is dedicated to providing more accurate data to capture the spatio-temporal heterogeneity of freeze/thaw transitions. As Sentinel-1 continues to deliver high-quality information, the provided threshold algorithm delivers an extended time series to analyze FT-states and improve our understanding of related processes in permafrost landscapes.
Towards investigating the race of two Marine Ice instabilities: Sheet vs. Cliff
Authors: Schlemm Tanja , Levermann Anders
Published: March 2021

Due to ocean warming in the Amundsen sea, pine island glacier and thwaites glacier could lose their buttressing ice shelves in the near future. This would lead to glacier retreat through the marine ice sheet instability and could be accelerated by additional cliff calving (marine ice cliff instability). Using the Parallel Ice Sheet Model (PISM-PIK) we investigate this in a regional setup of the West Antarctic Ice Sheet. We remove floating ice in the Amundsen sea and investigate the resulting glacier retreat without additional cliff calving and with cliff calving with a range of maximum calving rates. We find that without additional cliff calving, the removal of the ice shelves in the Amundsen sea leads to a glacier retreat that is equivalent to 0.4-0.6m of sea level rise in 100 years, consistent with earlier simulations of other models (ABUMIP and LARMIP-2). Cliff calving can more than double this number.
Geomorphological impact of storm Alex in the Maritime Alps, France: what can we learn from seismological observations?
Authors: Chmiel Małgorzata , Godano Maxime , Piantini Marco , Rivet Diane , Ampuero Jean-Paul , Gimbert Florent , Bakker Maarten , Courboulex Françoise , Sladen Anthony , Ambrois David , Brigode Pierre
Published: March 2021

On 2-3 October 2020, the Maritime Alps were struck by storm Alex, a violent meteorological event that triggered heavy rainfall in southeast France, more generally referred to as a "Mediterranean Episode". The Mediterranean episode generated cumulative 24-hour rainfall rate locally exceeding yearly averages (>500 mm per 24 hours). The torrential rains triggered hazardous sediment-transporting floods of an intensity never documented in the area causing several casualties, and large infrastructure and economic damage. 

Rain and stream gauges’ measurements during the episode are incomplete and highly uncertain due to threshold saturation and destruction of measuring devices, and changes in the stream bed. However, 11 regional seismological stations of the French permanent network recorded continuous ground shaking during and after the episode. Significant ground unrest was generated by the geomorphological phenomena providing additional information on their temporal and spatial dynamics.

Here, we present results of the combined efforts in environmental and crustal seismology to better understand the spatiotemporal dynamics of the sediment-transporting floods and hydrological forcing on the solid Earth during and after the episode. For that, we first analyze seismic power, peak frequency, and dominant noise directions of seismic signals generated by sediment-transporting floods to infer bedload transport dynamics. Moreover, by using template matching we detect 93 small earthquakes that were triggered during the Alex episode exactly in the area where rainfall was maximum. This exceptional seismic swarm is possibly triggered by overpressure due to the water load in karsts, or changes in pore fluid pressure. Our results illustrate that seismological observations allow for better understanding and quantifying of the geomorphological impact of extreme weather phenomena in mountainous settings and the related hydro-geomorphological hazards.