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1
Authors: Rennie, Susannah, et al
Published: Feb 2021
Authors: Rennie, Susannah, et al
Published: Feb 2021
Abstract. eLTER was a “Horizon 2020” project with the aim ofadvancing the development of long-term ecosystem research infrastructure inEurope. This paper describes how eLTER Information System infrastructure hasbeen expanded by a climate service data product providing access tospecifically pre-processed regional climate change scenario data from astate-of-the-art regional climate model ensemble of the Coordinated RegionalDownscaling Experiment (CORDEX) for 702 registered ecologicalresearch sites across Europe. This tailored, expandable, easily accessibledataset follows FAIR principles and allows researchers to describe theclimate at these sites, explore future projections for different climatechange scenarios and make regional climate change assessments and impactstudies. The data for each site are available for download from the EUDATcollaborative data infrastructure B2SHARE service and can be easily accessedand visualised through the Dynamic Ecological Information Management System– Site and Dataset Registry (DEIMS-SDR), a web-based information managementsystem which shares detailed information and metadata on ecological researchsites around the globe. This paper describes these data and how they can beaccessed by users through the extended eLTER Information Systemarchitecture. The data and supporting information are available from B2SHARE. Eachindividual site (702 sites are available) dataset has its own DOI. To aiddata discovery, a persistent B2SHARE lookup table has been created whichmatches the DOIs of the individual B2SHARE record with each DEIMS site ID.This lookup table is available at https://doi.org/10.23728/b2share.bf41278d91b445bda4505d5b1eaac26c (eLTEREURO-CORDEX Climate Service, 2020).
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Authors: Maria Cristina Bonci, Davide Dagnino, Andrea Mandarino, Aaron Mazzini, Michele Piazza
Published: Feb 2021
Authors: Maria Cristina Bonci, Davide Dagnino, Andrea Mandarino, Aaron Mazzini, Michele Piazza
Published: Feb 2021
The aim of this paper is the revision and redocumentation of Ostrea (Gigantostrea) gigantica Solander var. oligoplana Sacco, 1897, Ostrea (Ostrea) isseli n. denom. Rovereto, 1897, and Ostrea (Ostrea) isseli n. denom. var. elongata Rovereto, 1897. These taxa are from the Oligocene strata of the Molare Formation (Tertiary Piedmont Basin, southern Piedmont - central Liguria, NW Italy). The syntypes of O. (G.) gigantica var. oligoplana are in the "Collezione Bellardi e Sacco", at the Museo Regionale di Scienze Naturali di Torino; the syntypes of O. (O.) isseli and O. (O.) isseli var. elongata are in the "Collezione BTP" (BTP Collection, at the Dipartimento di Scienze della Terra, dell'Ambiente e della Vita - DISTAV - of the Università di Genova). The var. oligoplana is here moved to the species rank and allocated to the genus Pycnodonte Fischer von Waldheim, 1835. O. (O.) isseli and O. (O.) isseli var. elongata are recognized as junior synonyms of the Sacco's taxon. Rovereto (1897) compared his new species with Ostrea subgigantea Raulin & Delbos, 1855, a poorly known taxon, that is here figured for the first time and shown to represent a species different from P. oligoplana (Sacco, 1897).
1
Authors: Balázs Kövesdi
Published: Feb 2021
Authors: Balázs Kövesdi
Published: Feb 2021
Resistance calculation of steel bridges with orthotropic plates subjected to combined loading situation (bending moment, shear and transverse forces called as M-V-F interaction) can be challenging for designers due to the interactive stability behavior and combined buckling phenomena. The current EN 1993-1-5 standard provides a design method using analytical design equations checking the pure (bending, shear and patch loading) and interaction resistances separately. This design process is complex in the case of steel bridges, especially for box-section bridges having numerous longitudinal and transverse stiffeners. Finite Element Model (FEM) based design can provide suitable design tools for efficient and accurate resistance calculation of these structure types. However, within the modelling process there are numerous questions to be answered regarding material models and imperfections to ensure required accuracy and safe resistance. A new standard prEN 1993-1-14 is currently under development which will provide design rules to finite element model-based design of steel structures, having the aim to answer the main part of the above mentioned questions and standardize the design process. The current paper discusses and demonstrates the methodology of the FEM based design for welded plated structures. Benchmark example for a Hungarian steel box-section bridge subjected to combined loading situation is presented. Effect of different meshing, imperfection combinations and material models are presented and evaluated in the paper. Efficiency of the numerical model and the obtained resistance on the input parameters are evaluated and design example is given for the application of the FEM based design method.
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Authors: Kääb, Andreas, et al
Published: Feb 2021
Authors: Kääb, Andreas, et al
Published: Feb 2021
Abstract. Spatio-temporal patterns related to the viscous creep inperennially frozen sediments of rock glaciers in cold mountains have rarelybeen studied outside the densely populated European Alps. This studyinvestigates the spatial and temporal variability of rock glacier movementin the Ile Alatau and Kungöy Ala-Too mountain ranges, northern TienShan, a region with particularly large and fast rock glaciers. Over thestudy region of more than 3000 km2, an inventory of slope movements wasconstructed using a large number of radar interferograms and high-resolutionoptical imagery. The inventory includes more than 900 landforms, of whicharound 550 were interpreted as rock glaciers. Out of the active rockglaciers inventoried, 45 are characterized by a rate of motion exceeding100 cm/a. From these fast rock glaciers we selected six (Gorodetzky,Morenny, Archaly, Ordzhonikidze, Karakoram, and Kugalan Tash) and studiedthem in more detail using offset tracking between repeat aerial images andhistorical and modern high-resolution optical satellite data. Two of theserock glaciers showed a steady increase in decadal surface velocities fromthe 1950s onwards, with speeds being roughly 2 to 4 times higher inrecent years compared to the 1950s and 1960s. Three rock glaciers showedsimilar accelerations over the last 1 to 2 decades but also phases ofincreased speeds in the 1960s. This development indicates a possiblesignificant increase in current sediment and ice fluxes through rockglaciers and implies that their material transport in the region might gaingeomorphodynamic importance relative to material transport by glaciers,assuming the latter decreases together with the regional glacier shrinkage.The study demonstrates how air and satellite image archives are exploited toconstruct one of the longest decennial times series of rock glacier speedscurrently available. Our results are in line with findings from Europe aboutrock glacier speeds increasing with atmospheric warming and underline localvariability of such an overall response.
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Authors: Malehmir, Alireza, et al
Published: Feb 2021
Authors: Malehmir, Alireza, et al
Published: Feb 2021
Abstract. Many metallic mineral deposits have sufficient physical property contrasts, particularly density,to be detectable using seismic methods. These deposits are sometimes significant for our society andeconomic growth and can help to accelerate the energy transition towards decarbonization. However,their exploration at depth requires high-resolution and sensitive methods. Following a series of2D seismic trials, a sparse, narrow source–receiver azimuth, 3D seismic survey was conducted inthe Blötberget mine, in central Sweden, covering an area of approximately 6 km2 fordeep-targeting iron oxide deposits and their host rock structures. The survey benefited from acollaborative work by putting together 1266 seismic recorders and a 32 t vibrator,generating 1056 shot points in a fixed geometry setup. Shots were fired at every 10 mwhere possible, and receivers were placed at every 10–20 m. Notable quality data were acquireddespite the area being dominated by swampy places as well as by built-up roads and historicaltailings. The data processing had to overcome these challenges for the staticcorrections and strong surface waves in particular. A tailored for hardrock setting and processing workflow wasdeveloped for handling such a dataset, where the use of mixed 2D and 3D refraction staticcorrections was relevant. The resulting seismic volume is rich in terms of reflectivity, with clearsoutheast-dipping reflections originating from the iron oxide deposits extending vertically andlaterally at least 300 m beyond what was known from available boreholes. As a result, weestimate potential additional resources from the 3D reflection seismic experiment on the order of10 Mt to be worth drilling for detailed assessments. The mineralization is crosscut by at leasttwo major sets of northwest-dipping reflections interpreted to dominantly be normal faults and to beresponsible for much of the lowland in the Blötberget area. Moreover, thesepost-mineralization faults likely control the current 3D geometry of the deposits. Curved andsubmerged reflections interpreted from folds or later intrusions are also observed, showing thegeological complexity of the study area. The seismic survey also delineates the near-surfaceexpression of a historical tailing as a by-product of refraction static corrections, demonstratingwhy 3D seismic data are so valuable for both mineral exploration and mine planning applications.
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Authors: John F. Cherry, Krysta Ryzewski, Susana Guimarães, Christian Stouvenot, Sarita Francis
Published: Feb 2021
Authors: John F. Cherry, Krysta Ryzewski, Susana Guimarães, Christian Stouvenot, Sarita Francis
Published: Feb 2021
Only five years ago, Montserrat was a blank spot on the distribution map of islands in the Lesser Antilles where petroglyphs were known. In January 2016, hikers in Soldier Ghaut, a deeply incised watercourse in the northwest of the island, came upon a panel of nine petroglyphs engraved on a nearly vertical wall of volcanoclastic tuff. Soon afterward the petroglyphs were documented by the Survey and Landscape Archaeology on Montserrat project (SLAM). Then in January 2018 an additional petroglyph was spotted on a large slab of rock, detached from the rock wall on the opposite side of the ghaut. At the invitation of the Montserrat National Trust (MNT) and with European Union funding, Susana Guimarães and Christian Stouvenot traveled to Montserrat in 2018 to assist in further studies at the site. They conducted photogrammetric documentation and photography under enhanced lighting conditions and inspected the petroglyphs and their context in detail in order to advise MNT about their conservation and provisions for public access. This report presents this new group of petroglyphs and their landscape setting and considers questions of dating and interpretation.
1
Authors: Keen, Ann, et al
Published: Feb 2021
Authors: Keen, Ann, et al
Published: Feb 2021
Abstract. We compare the mass budget of the Arctic sea ice for 15 modelssubmitted to the latest Coupled Model Intercomparison Project (CMIP6),using new diagnostics that have not been available for previous modelinter-comparisons. These diagnostics allow us to look beyond the standardmetrics of ice cover and thickness to compare the processes of sea icegrowth and loss in climate models in a more detailed way than has previouslybeen possible. For the 1960–1989 multi-model mean, the dominant processes causing annual icegrowth are basal growth and frazil ice formation, which both occur duringthe winter. The main processes by which ice is lost are basal melting, topmelting and advection of ice out of the Arctic. The first two processesoccur in summer, while the latter process is present all year. The sea icebudgets for individual models are strikingly similar overall in terms of themajor processes causing ice growth and loss and in terms of the time ofyear during which each process is important. However, there are also somekey differences between the models, and we have found a number ofrelationships between model formulation and components of the ice budgetthat hold for all or most of the CMIP6 models considered here. The relativeamounts of frazil and basal ice formation vary between the models, and theamount of frazil ice formation is strongly dependent on the value chosen forthe minimum frazil ice thickness. There are also differences in the relativeamounts of top and basal melting, potentially dependent on how muchshortwave radiation can penetrate through the sea ice into the ocean. Formodels with prognostic melt ponds, the choice of scheme may affect theamount of basal growth, basal melt and top melt, and the choice ofthermodynamic scheme is important in determining the amount of basal growthand top melt. As the ice cover and mass decline during the 21st century, we see ashift in the timing of the top and basal melting in the multi-model mean,with more melt occurring earlier in the year and less melt later in thesummer. The amount of basal growth reduces in the autumn, but it increasesin the winter due to thinner sea ice over the course of the 21stcentury. Overall, extra ice loss in May–June and reduced ice growth inOctober–November are partially offset by reduced ice melt in August andincreased ice growth in January–February. For the individual models, changesin the budget components vary considerably in terms of magnitude and timingof change. However, when the evolving budget terms are considered as afunction of the changing ice state itself, behaviours common to all themodels emerge, suggesting that the sea ice components of the models arefundamentally responding in a broadly consistent way to the warming climate. It is possible that this similarity in the model budgets may represent alack of diversity in the model physics of the CMIP6 models considered here.The development of new observational datasets for validating the budgetterms would help to clarify this.
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Authors: Elisabeth D. Hafner, Frank Techel, Silvan Leinss, Yves Bühler
Published: Feb 2021
Authors: Elisabeth D. Hafner, Frank Techel, Silvan Leinss, Yves Bühler
Published: Feb 2021
Abstract. The spatial distribution and size of avalanches are essential parameters foravalanche warning, avalanche documentation, mitigation measure design andhazard zonation. Despite its importance, this information is incompletetoday and only available for limited areas and limited time periods. Manualavalanche mapping from satellite imagery has recently been applied to reducethis gap achieving promising results. However, their reliability andcompleteness have not yet been verified satisfactorily. In our study we attempt a full validation of the completeness of visuallydetected and mapped avalanches from optical SPOT 6, Sentinel-2 and radarSentinel-1 imagery. We examine manually mapped avalanches from two avalancheperiods in 2018 and 2019 for an area of approximately 180 km2 aroundDavos, Switzerland, relying on ground- and helicopter-based photographs asground truth. For the quality assessment, we investigate the probability ofdetection (POD) and the positive predictive value (PPV). Additionally, werelate our results to conditions which potentially influence avalanchedetection in the satellite imagery. We statistically confirm the high potential of SPOT for comprehensiveavalanche mapping for selected periods (POD = 0.74, PPV = 0.88) as wellas the reliability of Sentinel-1 (POD = 0.27, PPV = 0.87) for which thePOD is reduced because mainly larger avalanches are mapped. Furthermore, wefound that Sentinel-2 is unsuitable for the mapping of most avalanches dueto its spatial resolution (POD = 0.06, PPV = 0.81). Because we couldapply the same reference avalanche events for all three satellite mappings,our validation results are robust and comparable. We demonstrate thatsatellite-based avalanche mapping has the potential to fill the existingavalanche documentation gap over large areas, making alpine regions safer.
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Authors: Liang Xue, Shao-Hua Gu, Xie-Er Jiang, Yue-Tian Liu, Chen Yang
Published: Feb 2021
Authors: Liang Xue, Shao-Hua Gu, Xie-Er Jiang, Yue-Tian Liu, Chen Yang
Published: Feb 2021
Abstract Shale gas reservoirs have been successfully developed due to the advancement of the horizontal well drilling and multistage hydraulic fracturing techniques. However, the optimization design of the horizontal well drilling, hydraulic fracturing, and operational schedule is a challenging problem. An ensemble-based optimization method (EnOpt) is proposed here to optimize the design of the hydraulically fractured horizontal well in the shale gas reservoir. The objective is to maximize the net present value (NPV) which requires a simulation model to predict the cumulative shale gas production. To accurately describe the geometry of the hydraulic fractures, the embedded discrete fracture modeling method (EDFM) is used to construct the shale gas simulation model. The effects of gas absorption, Knudsen diffusion, natural and hydraulic fractures, and gas–water two phase flow are considered in the shale gas production system. To improve the parameter continuity and Gaussianity required by the EnOpt method, the Hough transformation parameterization is used to characterize the horizontal well. The results show that the proposed method can effectively optimize the design parameters of the hydraulically fractured horizontal well, and the NPV can be improved greatly after optimization so that the design parameters can approach to their optimal values.
1
Authors: Mostafa Abdel-Hameed Mohamed, Mohamed El-Sayed El-Mahdy
Published: Feb 2021
Authors: Mostafa Abdel-Hameed Mohamed, Mohamed El-Sayed El-Mahdy
Published: Feb 2021
Abstract. Climate change raises important issues concerning hydrological engineering.The impact of climate change on important river basins should beinvestigated rigorously. Extreme temperature variability has a direct impacton the hydrological cycle, especially the evaporation component. In thispaper, spatial and temporal patterns of changes in extreme temperatures wereinvestigated using 10 meteorological stations' data for the period 1950–2018in the Blue Nile Basin. Long-term trends in the Blue Nile Basin annual andmonthly temperatures were investigated. The statistical significance of thetrend was calculated by applying the Mann–Kendall (MK) test. The analysis ofdata was performed using the coefficient of variance and anomaly index. Theresults showed that the annual maximum and minimum temperatures wereincreasing significantly with a magnitude of 0.037 and0.025 ∘C per decade respectively in the period from 1950 to2018. The result of the Mann–Kendall analysis test revealed a markedincrease in the mean maximum and minimum temperature trends over time duringthe study period (the minimum temperature rate is more evident than themaximum). The long-term anomalies of mean annual minimum temperaturerevealed the interannual variability while the trend after 1977 was higherthan the long-term average, which is proof of the warming trend's existenceduring the last two decades of the 20th century.
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