bluuebunny/crossref_metadata_2025 huggingface dataset:
Negative Velocity Gradients in the uppermost Mantle below the larger Alpine Area
Authors: Kind Rainer , Schmid Stefan , Yuan Xiaohui , Working Group Alparray
Published: March 2020

In the frame of the Alparray project we analyse teleseismic data from permanent and temporary stations of the greater Alpine area to study the structure of the crust and the uppermost mantle. We use S-to-p and P-to-s converted waves below the seismic stations which are aligned along the arrival times of the generating P and SV signals. The broadband data used are unfiltered, amplitude normalized and sign corrected. Profiles of migrated data are constructed through the entire Alpine area and compared with results of tomographic, controlled-source and receiver function studies. Thereby we provide additional constraints regarding the ongoing controversies regarding the configuration of the various slabs whose existence was postulated by previous authors within the larger Alpine area including the Western Carpathians. Special attention is given to the possibility of a reversal of subduction polarity in the eastern Alps.
Trends in intra-seasonal temperature variability in Europe
Authors: Krauskopf Tomas
Published: March 2020

While long-term changes in measures of central tendency of climate elements, i. e. mean temperature, are well acknowledged, studies of trends in measures of their variability are much less common. This is despite the fact that trends in variability can have higher effect on climate extremes than trends in mean. Here, three measures of intra-seasonal variability are examined: 1) standard deviation of mean daily temperature 2) mean absolute value of day-to-day temperature change, 3) the range between the 90th and 10th quantile of mean daily temperature. ECA&D daily data from 180 stations and linear regression method are utilized to calculate trends of these characteristics in period from 1961 to 2012. Spatial distribution of trends in individual variability characteristics in Europe together with long-term change in mean and autocorrelation of mean temperature are demonstrated in maps. Significant trends (positive and negative) in all examined variability characteristics were found with substantial differences between seasons as well as between regions. On this basis, Europe is divided into 6 regions and trends are assessed in each reagion separately. While the most significant decrease in variability is observed in Northern Scandinavia and Iceland in winter, the most substantial increase is detected in Central and Western Europe in spring. Our results are accompanied by comparing the probability density function of daily temperature between periods 1961 – 1986 and 1987 – 2012 in each region showing how the shape of distribution of daily temperature has changed and if it could affect the changing number and value of temperature extremes.
Detection and characterization of SCVs in the North Atlantic
Authors: Chouksey Ashwita , Carton Xavier , Gula Jonathan
Published: March 2020

In recent years, the oceanographic community has devoted considerable interest to the study of SCVs (Submesoscale Coherent Vortices, i.e. vortices with radii between 2-30 km, below the first internal radius of deformation); indeed, both mesoscale and submesoscale eddies contribute to the transport and mixing of water masses and of tracers (active and passive), affecting the heat transport, the ventilation pathways and thus having an impact on the large scale circulation.

In different areas of the ocean, SCVs have been detected, via satellite or in-situ measurements, at the surface or at depth. From these data, SCVs were found to be of different shapes and sizes depending on their place of origin and on their location. Here, we will concentrate rather on the SCVs at depth.

In this study, we use a high resolution simulation of the North Atlantic ocean with the ROMS-CROCO model. In this simulation, we also identify the SCVs at different depths and densities; we analyse their site and mechanism of generation, their drift, the physical processes conducting to this drift and their interactions with the surrounding flows. We also quantify their physical characteristics (radius, thickness, intensity/vorticity, bias in polarity: cyclones versus anticyclones). We provide averages for these characteristics and standard deviations. 

We compare the model results with the observational data, in particular temperature and salinity profiles from Argo floats and velocity data from currentmeter recordings. 

This study is a first step in the understanding of the formation, occurrences and structure of SCVs in the North Atlantic Ocean, of help to improve their in-situ sampling.
The Role of Changing Indian Ocean Salinity in shaping Pleistocene Climate
Authors: Nuber Sophie , Rae James W. B. , Andersen Morten B. , de Boer Bas , Zhang Xu , Hall Ian R. , Barker Stephen
Published: March 2020

Indian Ocean surface salinity dynamics are thought to play an important role in shaping glacial-interglacial climate through controlling Agulhas leakage efficiency. It is proposed that a strong Agulhas leakage supplies warm and salty Indian ocean surface waters to Atlantic surface currents influencing convective potential at North Atlantic deep-water formation sites. Here, we present new planktonic foraminiferal Mg/Ca and stable isotope-derived salinity reconstructions for the last 1.2Ma from the northern Mozambique channel. We find salinity increases well before terminations, followed by early decrease before glacial inception. We present a possible link between the hydrography in the northern Mozambique channel and whole ocean salinity changes due to unique surface circulation in the Indian ocean. Despite being a mostly tropical and subtropical ocean, salinity in the modern tropical Indian Ocean is fresher than at comparable latitudes in the Atlantic or Pacific. This is due to the inflow of freshwater from the Indonesian throughflow and recycling via an active Agulhas leakage. We show that salinity in the glacial western Indian Ocean was significantly higher due to a reduced ITF and a weaker Agulhas leakage. We hypothesise that opening and closing of these two gateways influences the development/diminishment of a strong subtropical Indian Ocean gyre which controls sea surface salinity and temperature of tropical Indian Ocean water masses and subsequently the efficiency of the Agulhas Leakage.
Evapotranspiration over a rainfed maize field in northeast China: how are relationships between the environment and terrestrial evapotranspiration mediated by leaf area?
Authors: Zhou Li , Wang Yu , Zhou Guangsheng
Published: March 2020

As a central process in the hydrological system and the climate system, terrestrial evapotranspiration is a key factor furthering our understanding of the climate change processes. Knowledge of factors controlling the variability in evapotranspiration is crucial for the prediction of the fate of terrestrial ecosystems under environmental changes. Based on long-term (2005-2014) eddy covariance flux data observed at a rainfed maize site in northeast China, the purpose of this study was to clarify the environmental regulation of actual evapotranspiration (ET) and the extent to which the regulatory effects on ET are directly or indirectly mediated by changes in biotic factors, using the structural equation modeling (SEM) method. The results showed that annual total ET was 397 ± 35 mm for the rainfed maize site in comparison with 575 ± 169 mm of precipitation (Prec), with an ET/Prec ratio ranging from 0.43 (2012) to 1.14 (2014). It was revealed that net radiation (Rn) was the primary controlling factor of the maize ET, followed by leaf area index (LAI), vapor pressure deficit (VPD), air temperature (Ta), and soil water content (SWC). The adjusted SEM models explained 71%, 67%, and 67% of the variation in daily ET of the maize growing season (ETgs) for dry, normal, and moist years, respectively. Rn and VPD dominated ETgs in an increasing order of dry, normal, and moist years. Conversely, the effects of LAI and Ta on ETgs followed the opposite trend. This indicated that drought may increase the sensitivity of maize ET to temperature changes, and decrease the sensitivity of maize ET to radiation changes. In SEM analysis, LAI played an important mediating role in the relationship among climate, soil variables, and ETgs. Rn, VPD, Ta, and SWC all had significant indirect effects on ETgs mediated through LAI. At the annual scale, it was identified that most active days could be a robust predictor of annual ET.
Carbon dynamics and full carbon balance of a Northern mire ecosystem
Authors: Vestin Patrik , Weslien Per , Wallin Marcus , Bastviken David , Kljun Natascha , Edvardsson Johannes , Holst Jutta , Lindroth Anders , Crill Patrick , Rinne Janne , Klemedtsson Leif
Published: March 2020

We present the Net Ecosystem Carbon Balance (NECB) of a Northern mire ecosystem for the period 2016-2019. The Mycklemossen peatland is located in the hemi-boreal region in the Southwestern part of Sweden and is classified as a fen with bog-like vegetation. The NECB was determined from eddy covariance (EC) measurements of carbon dioxide (CO2) and methane (CH4) and continuous water discharge measurements with biweekly measurements of dissolved organic carbon (DOC), dissolved inorganic carbon (DIC) and dissolved CH4.
We focus on the carbon dynamics of the Mycklemossen ecosystem during summer droughts and on its recovery during normal years. During 2016-2018, the annual precipitation was lower than the 30-year average while 2019 was a normal year in terms of weather conditions. 2018 sticks out as an extreme year with a severe drought and unusually high air temperature at Mycklemossen, as was the case in much of Northern and Central Europe.
The EC results indicate that Mycklemossen lost carbon during 2016-2018. While CH4 emissions decreased, the mire became a strong source of CO2 these years, especially 2018. There were also large losses of DOC during this period, which were further enhanced during 2019.
A Study of Sediment Yield in the Deji Reservoir Watershed Using Risk Analysis
Authors: Chang Wen Wei , Lin Chao Yuan
Published: March 2020

Deji Reservoir Watershed was used as a sample site to understand the sediment yield using risk analysis. The historic typhoon and/or torrential storm events were collected to estimate the excessive runoff for each event. The distribution of SCS-CN is obtained by combining the maps of land use and soil texture, and the excess rainfall (Pe) and the maximum water storage (S) for each event were then calculated according to SCS-CN. Regression analysis shows that there is a good relationship between estimated runoff (x) and measured runoff (y); y=0.9561x+3*106, R2= 0.9414. Topographic wetness index (TWI) and sediment delivery ratio (SDR) were derived from DEM. The risk model developed to assess the sediment yield is calculated from the multiplication of hazard (Pe), vulnerability (TWI), and exposure (SDR). The total siltation amount of Deji Reservoir from 2009 to 2017 was taken as the measured value, and the estimated amount of sediment yield was calculated from the aforementioned formula  to obtain the potential index of sediment yield. The results show that there is also a good relationship between estimated sediment yield (x') and measured sediment yield (y') annually; y'=10-11x'2-0.0223x'+9*106 , R2= 0.74.

Keywords: Risk Analysis, Curve Number, Sediment Delivery Ratio
Recent changes of the salinity distribution in the South Adriatic
Authors: Mauri Elena , Menna Milena , Notarstefano Giulio , Gerin Riccardo , Martellucci Riccardo , Poulain Pierre-Marie
Published: March 2020

The South Adriatic is one of the dense water formation site in the Mediterranean Sea. The variations of its thermohaline properties are relevant not only from an oceanographic and climatic point of view but also for the local impact on the vertical distribution of the biogeochemical parameters.

The South Adriatic Pit has been extensively sampled during the last forty years by traditional shipboard techniques. Float and glider measurements became part of the investigation only in the last ten years, providing a more detailed and more uniform spatio-temporal dataset. From the analysis, evidences of important changes of the South Adriatic Pit salinity vertical distribution emerge in the last 5 years. In the past, the Levantine Intermediate Water (LIW) entered the South Adriatic at a depth between 100 and 300 m, highlighted by a maximum in the salinity. The recent findings suggest that the LIW is no longer characterized by the highest salinity along the vertical profiles, which is present instead in shallower subsurface layers. In addition, in most of the seasons a thick low salinity layer is evident in the top 50-100 m. Among those changes, some peculiar haline characteristics occur in 2012 and 2017; they will be analyzed in concert with auxiliary data and model outputs.
High-frequency hybrid modelling of near-source topographic effects at teleseismic distances: The Degelen mountain case study
Authors: Pienkowska Marta , Nippress Stuart , Nissen-Meyer Tarje , Bowers David
Published: March 2020

We apply a hybrid method that couples global Instaseis databases (van Driel et al., 2015) with a local finite-difference code WPP (Nilsson et al., 2007) to study the 1960s-1980s nuclear explosions located at the USSR Degelen mountain test site. Observed teleseismic P waves (up to 2 Hz) display strong near-source signatures, yet the relative importance of contributing factors – such as explosion depth and yield, scattering from near-source topography and geological heterogeneities, as well as non-linear effects – are not well understood. An analysis of teleseismic waveforms suggest that these features are dependent on the source location within the Degelen mountain range, while depths and yields do not show a consistent effect. We therefore propose that the change in signal characteristics on teleseismic waveforms is related to the mountainous topography in the source region and we turn to deterministic hybrid modelling to test the effect of Degelen topography at teleseismic distances. Despite simplistic modelling assumptions, we achieve an excellent fit with the observed waveforms. Amplitudes are in good agreement and many observed features are reproduced by synthetic seismograms at 2 Hz, highlighting the importance of near-source 3-D effects on long-range wave propagation. Hybrid modelling of more realistic high-frequency scenarios could ultimately lead to waveform-based constraints on explosion locations, for example via grid-search methods or more advanced learning algorithms, or even improve nuclear discrimination methods.
On the identification of Electron Diffusion Regions at the magnetopause with an AI approach
Authors: Lenouvel Quentin , Génot Vincent , Garnier Philippe , Toledo-Redondo Sergio , Lavraud Benoît , Torbert Roy , Giles Barbara , Burch Jim
Published: March 2020

MMS has already been producing a very large dataset with invaluable information about how the solar wind and the Earth's magnetosphere interact. However, it remains challenging to process all these new data and convert it into scientific knowledge, the ultimate goal of the mission. Data science and machine learning are nowadays a very powerful and successful technology that is employed to many applied and research fields. During this presentation, I shall discuss the tentative use of machine learning for the automatic detection and classification of plasma regions, relevant to the study of magnetic reconnection in the MMS data set, with a focus on the critical but poorly understood electron diffusion region (EDR) at the Earth's dayside magnetopause. We make use of the EDR database and the plasma regions nearby that has been identified by the MMS community and compiled by Webster et al. (2018) as well as the Magnetopause crossings database compiled by the ISSI team, to train a neural network using supervised training techniques. I shall present a list of new EDR candidates found during the phase 1 of MMS and do a case study of some of the strong candidates.
Optimized global map projections for specific applications: the triptychial projection and the Spilhaus projection
Authors: Grieger Björn
Published: March 2020

There is no perfect global map projection. A projection may be area preserving or conformal (shape preserving on small scales) in some regions, but it will inevitably exhibit considerable distortions in others. An oblique version of a projection (where the globe is rotated before projecting) can be optimized to avoid major distortions in specific regions of interest.
We present two global map projections of the Earth which either display all continents (including Antarctica) or the complete world ocean with minimal distortion and without any intersection. These are the triptychial projection and the Spilhaus projection, respectively.
The triptychial projection is original work and has been published by Grieger (2019). While that paper comprises complete information on the definition of the projection, the details of its application need to be collected from literature referenced therein. The triptychial projection is an oblique and rearranged version of the Peirce quincuncial projection of the world (Peirce, 1879).
Instances of the Spilhaus projection went viral on the internet in fall 2018. The projection is mostly attributed to a publication from 1942, but in fact it seems to appear for the first time in Spilhaus (1979). The projection is shown in that paper (and in a few later ones), but no information on its definition is provided. Developers of ArcGIS did some reverse engineering and could identify the Spilhaus projection as an oblique version of the Adams projection of the world in a square II (Adams, 1929).
The triptychial and the Spilhaus projection both imply several steps in their application. While the two projections look very different, they have one step in common: the conformal mapping of a hemisphere onto a square, which requires tabulated Jacobi elliptic functions. We review both projections, describe them in full detail, and provide all formulas and data needed to apply them. The algorithms employed may also be interesting for planetary applications.
Factors controlling shear rupture roughness: An insight from field and laboratory experiments
Authors: Mukhopadhyay Manaska , Biswas Uddalak , Mandal Nibir , Misra Santanu
Published: March 2020

Faults and fracture surfaces record the history of slip events through a range of structural features in tectonically active zones. Slickensides, among them, prove to be the most prominent evidences of such slip movements. These linear features give us crucial information about the mechanical processes associated with shear surface roughness formation. We conducted extensive field survey in the Singhbhum Shear Zone, Eastern India, and report shear fractures of varying surface roughness from deformed quartzites. Shear surfaces encountered in the field study varied from very smooth, devoid of any lineation to strongly rough with prominent slickenlines.

For better understanding of the varied surface roughness, we performed analogue laboratory experiments. The experimental results suggest that the fracture orientation and the mode of shear failure are potential factors that control the fracture roughness. We used cohesive sand-talc models for the analogue experiments with varying sand:talc volume ratio, ranging from pure sand to pure talc variant. Experimental models with pure sand composition underwent Coulomb failure in the brittle regime. With subsequent increase in talc content, the behavior of failure switched to plastic yielding in the ductile regime. This transition from coulomb failure to plastic yielding produced a remarkable variation in the shear surface roughness characteristics. Shear surfaces formed by Coulomb failure are smooth and devoid any slickenlines, whereas, those formed by plastic yielding show prominent presence strongly linear roughness, defined by cylindrical ridge-grooves along the slip direction.

Shear surface roughness defined by linear irregularities become more prominent with increasing fracture orientation (θ) to the compression direction (θ = 30° to 60°). Increase in θ promotes the formation of smooth slickenlines at the cost of rough zones. For critical analysis and understanding of these features we develop a new computational technique. The technique is based on controlled optical images to map the shear surface geometry from field casts and laboratory samples. Binarization of the irregular surface images (cantor set) provides 1D fractal dimension (D), which is used to quantify the roughness variability, and the degree of their anisotropy in terms of ΔD (difference in D across and along the slip direction). From numerical models, we finally show onset of wave instability in the mechanically distinct rupture zone as an alternative mechanism for slickenlines formation.  
Structural ecosystem change in Holocene chironomid assemblages
Authors: Mayfield Roseanna , Langdon Peter , Dearing John , Doncaster Patrick , Wang Rong
Published: March 2020

There is a growing trend in using structural analyses to investigate temporal changes in ecosystem system architecture. System architecture defines the organisation of taxa within a system and how this may affect system response to stress. Over the Holocene, in areas with little/no human impact, the climate has been a key driver of ecosystem change, including post-glacial to early/mid-Holocene warming, subsequent neoglacial cooling, and rapid climate change events such as the 8.2 kyr event. This study aims to investigate whether Holocene climate change is a driver for structural change in temperature-sensitive organisms, such as chironomids, in high latitude lakes. These areas are at risk from rapidly rising global temperatures, with warmer temperatures already recorded and predicted to continue rising in high latitude areas. Increased temperatures can create stress on ecologically sensitive environments where many organisms are adapted to cooler temperatures. Three sets of analyses - beta diversity, compositional disorder, and network skewness - are applied to Norwegian chironomid sequences to investigate ecosystem structural change during the Holocene.
The Seasonality of submesoscale variability in the Antarctic Seasonal Ice Zone
Authors: Giddy Isabelle , Nicholson Sarah , Du Plessis Marcel , Thompson Andy , Swart Sebastiaan
Published: March 2020

The ocean surface boundary layer in the Southern Ocean plays a critical role in heat and carbon exchange with the atmosphere. Submesoscale flows have been found to be important in setting mixed layer variability in the Antarctic Circumpolar Current (ACC). However, sparsity in observations, particularly south of the ACC in the Antarctic Seasonal Ice Zone (SIZ) where the horizontal density structure of the mixed layer is influenced by sea ice melt/formation and mesoscale stirring, brings into question the ability of climate models to correctly resolve mixed layer variability. We present novel fine-scale observations of the activity of submesoscale variability in the ice-free Antarctic SIZ using three deployments of underwater gliders over an annual cycle. Salinity-dominated density fronts of O(1)km associated with strong horizontal buoyancy gradients are observed during all deployments. There is evidence that stratifying ageostrophic eddies, energised by salinity driven submesoscale fronts are active across seasons, with intermittent equivalent heat fluxes of the same order to, or greater than local atmospheric forcing. This study highlights the need to consider future changes of Antarctic sea-ice in respect to feedback mechanisms associated with salinity (sea-ice) driven submesoscale flows.
A Simple Model for Glacial Cycles and Impact of fossil fuel CO2 emissions
Authors: Talento Stefanie , Ganopolski Andrey
Published: March 2020

We propose a simple physically-based model of the coupled evolution of Northern Hemisphere (NH) landmass ice-volume, atmospheric CO2 concentration and global mean temperature. The model only external forcings are the orbital forcing (maximum solar insolation at 65°N) and anthropogenic CO2 emissions. The model consist of a system of 3 coupled non-linear differential equations, representing physical mechanisms relevant for the evolution of the climate system in time-scales longer than thousands of years.

 

When forced by the orbital forcing only, the model is successful in reproducing the natural glacial-interglacial cycles of the last 800kyr, in agreement with paleorecords and simulations performed with the CLIMBER-2 Earth System Model of intermediate complexity. The model is successful in reproducing both the timing and amplitude of the glacial-interglacial variations, producing a correlation with paleodata of 0.75 in terms of NH ice-volume.

 

For the next million years, we analyse the model results under different scenarios: the natural scenario (in which only orbital forcing is applied) and scenarios in which various magnitudes of fossil fuel CO2 emissions are considered (in addition to the orbital forcing).

 

When anthropogenic emissions are included the model shows that even fairly low CO2 anthropogenic emissions (100 Pg or larger) are capable of affecting the next glacial inception, expected to occur in 120kyr from now, delaying large NH ice formation by 50kyr. Considering total carbon releases ranging between 1000 and 5000 Pg (a reasonable expectation of fossil fuel CO2 emissions to occur in the next few hundred years) the temporal evolution of the climate system could be significantly different from the natural progression. Emissions larger than 3000 Pg could have long-lasting effects, being natural conditions not resumed even after 1 Million years have passed. In addition, emissions larger than 4000 Pg prevent glacial cycles in the next half million years.
A framework to characterize flood events of defined return period ranges using functional boxplots
Authors: Staudinger Maria , Furrer Reinhard , Viviroli Daniel
Published: March 2020

To assess the safety of dams, design floods are typically used as a basis. Of particular interest are events with a return period of 1’000 years and even rarer events derived from that with help of simple return period conversion factors given by design codes. However, both the peaks and even more the flood volumes of such rare events are subject to large uncertainties due to limited length and spatial coverage of gauge records. Bivariate approaches can help reduce the uncertainty related to the flood volumes. Nevertheless, both univariate and bivariate approaches require long-term observations on which the return periods of flood events can be calculated.

In this study, we make use of very long simulated hydrographs in hourly resolution for Swiss catchments (scale range: ~300–18’000 km²). The hydrographs span about 300’000 years each and stem from a hydro-meteorological modelling chain starting with a stochastic multi-site weather generator. With these hydrographs, we develop a framework to characterize design floods through a realistic hydrograph using functional data analysis as well as hydrographs that envelope 50%, say, of the most central observations (corresponding to the 25% and 75% quantiles in a univariate setting).

In a first step, we assigned the simulated annual maximum flood events to return period classes of 100, 1000 and 10000 years. We then built clusters of similar events within each class using functional clustering. Here we explore some of the possibilities of the approach and in particular show how sensitive the functional clustering is to the choice 1) of event characterization (peak only, flood peak and volume, flood volume given a minimum flood peak), and 2) to the separation of event and baseflow of the selected events in the bivariate case and 3) to the different functional latent mixture models that are applied within the functional clustering.
Analysis of the laboratory hydraulic fracturing curves.
Authors: Novikova Helen , Trimonova Mariia
Published: March 2020

In this study, the data obtained during a series of laboratory experiments on hydraulic fracturing were analyzed. The main goal was to determine the time of the fracture closure, the pressure of the fracture closure, and the permeability of the sample, where the fracture was formed and propagated.

A special laboratory setup was used to conduct the experiments. The design of this setup allows to provide a three-axis load on the model sample, which makes the conditions of the laboratory experiment on hydraulic fracturing closer to the real conditions in the field. To produce the fracture, viscous fluid was injected under constant rate through the preliminary created cased borehole with perforations.

As results of the experiments, the curves of the fluid injection pressure variations with time were obtained. Their analysis was carried out using the G-function technique developed by Nordgren [1] and Nolte [2]. It is based on the plotting and analyzing of the behavior of the following dependencies: the injection pressure, first derivative of the pressure and the semi-logarithmic derivative of the pressure with respect to G-function. The curves processing allows to estimate the time of the fractures closure, with the help of which the fracture closure pressure was determined. The obtained pressure values were compared with the minimum stresses known from the experimental conditions.

Additionally, the permeability of the model reservoir sample was calculated using a technique developed by Horner [3] and improved by Nolte et al. [4]. The approach is based on an assumption that the fracture in the formation has been already closed, and a radial regime of fluid flow has been established. The obtained results were compared with the actual permeability, which was determined in the preliminary laboratory experiment.

Acknowledgements

The reported study was funded by RFBR, project number 20-35-80018, and state task 0146-2019-0007.

References

Nordgren, R. P. [1972] Propagation of a vertical Hydraulic Fracture. SPE 45th Annual Fall Meeting, Houston, SPE-3009-PA.

Nolte, K. G. [1979] Determination of Fracture Parameters from Fracturing Pressure Decline. The 54th Annual Fall Technical Conference and Exhibition of the Society of Petroleum Engineers of AIME, Las Vegas, SPE-8341-MS.

Horner, D. R. [1951] Pressure Build-Up in Wells. 3rd World Petroleum Congress, Netherlands, WPC-4135.

Nolte, K. G., Maniere, J. L., Owens, K. A. [1997] After-Closure Analysis of Fracture Calibration Tests. SPE Annual Technical Conference and Exhibition, San Antonio, Texas, SPE-38676-MS.
Can the latest generation of regional climate models reproduce European snow conditions and how do biases translate into uncertainties of snow cover projections?
Authors: Bülow Katharina , Kotlarski Sven , Steger Christian , Teichmann Claas
Published: March 2020

Snow cover is a crucial part of the climate system due to its distinctive alteration of surface reflectance (snow-albedo-feedback) and its influence on further physical surface properties (e.g. heat conduction and water storage). These effects are particularly relevant in alpine areas and high latitude regions, where snow coverage prevails for a significant part of the season. In addition, various human activities rely on snow cover duration and/or snow amounts, such as winter tourism, agriculture and hydropower production.

The EURO-CORDEX project provides an RCM ensemble with a horizontal resolution of ~50 and ~12 km for both present-day and future climates assuming different emission scenarios. These simulations present a potentially valuable information source for the future snow cover evolution. Prerequisite, however, is the ability of RCMs to reproduce historical snow cover conditions. These issues are addressed in the present work on a European scale. A horizontal resolution of ~12 km allows for an improved representation of topography and is thus particularly interesting for snow cover studies, as snow in alpine regions strongly correlates with elevation. We therefore only consider the high-resolution EURO-CORDEX RCMs and, for the climate projection part, simulations for RCP2.6, RCP4.5 and RCP8.5.

To assess the RCMs’ ability of reproducing current snow cover conditions in Europe, we evaluate simulated snow water equivalent and snow cover duration/extent by comparison against different reanalysis data (e.g. ERA5, UERRA MESCAN-SURFEX) and snow products derived from remote sensing. Regarding the spatial domain, we consider entire Europe with a focus on four mountainous regions (Alps, Norway, Pyrenees and Carpathians). The evaluation reveals that, on an European scale, mean yearly snow cover duration is well captured by the ensemble mean of the models. However, the majority of the RCMs underestimates snow cover extent throughout the season. This bias is more pronounced in the reanalysis (ERA-Interim) driven set of simulations than in the GCM-driven runs. In regions with complex topography, winter snow water equivalent is distinctively overestimated in some simulations - whereas certain grid cells reveal glaciation (i.e. year-round snow coverage). A comparison with E-OBS data indicates that biases in snow cover duration and amount are, besides arising from inaccurate snow schemes, linked to mismatches in simulated air temperature and precipitation patterns. Scenarios for the 21st century show a distinctive reduction in snow cover duration for low-elevation regions, whereas the magnitude of this decrease depends, amongst other factors, on the climate scenario. Projected decreases in the snow cover are less pronounced for medium to high-elevation regions.
Investigating hydrogel potentialities for improving soil pore network by using X-ray computed microtomography
Authors: Piccoli Ilaria , Sara Pozza , Camarotto Carlo , Squartini Andrea , Guerrini Giacomo , Morari Francesco
Published: March 2020

Hydrogels (HGs) are conventionally defined as a natural or synthetic polymeric 3D networks with high hygroscopicity and water-swelling properties. Over the decades, HGs have been widely utilized in various fields of cosmetics, food additives, tissue engineering, drug delivery, and pharmaceuticals. Only recently HGs have been studied also for agronomic purpose. Indeed, their unique physical properties, including their porosity and swellability, make them ideal platforms for water and nutrient delivering. The aim of this study was to investigate the potentialities of two HGs, one formed by polyacrylamide and one by cellulose added with clay and humic acids, for improving soil porosity of three soil types (sandy “SD”, silty “SL” and clay “CL”). Soil pore network was characterized with X-ray computed microtomography (µCT) at 50 µm resolution and subsequent image analysis measuring  total porosity (TP), pore size distribution (PSD), mean diameter (MD), connectivity density and degree of anisotropy. Soil samples were at first saturated and then dried trough freezing and drying cycles with acetone at -80°c.

Preliminary results showed that at water saturation HG increased TP of four- and two-fold, respectively for SL and CL soil, MD of 40 (SD), 519 (SL) and 164 µm (CL) while no effects were found on other pore architecture indices (e.g., connectivity or anisotropy). The PSD analysis highlighted that HG increased the macroporosity fraction (e.g., pore > 0.8 mm) only in SL (+36%) and CL (+11%) while the other pore classes were not affected. Present study demonstrated that in fine-textured soils at high water content, HG might be a valuable tool to increase not simply the TP but, in particular, the macroporosity fraction which may play a key role in soil functioning and ecosystem services. Future research will investigate the HG performances under dynamic soil moisture conditions on water holding capacity and hydraulic conductivity (Research supported by Fondazione CARIPARO, InnoGel, Progetti Eccellenza 2017).
Space-weighted seismic attenuation multi-frequency tomography at Deception Island volcano (Antartica)
Authors: Guardo Roberto , De Siena Luca , Caselli Alberto , Prudencio Janire , Ventura Guido
Published: March 2020

Deception Island is the most active and documented volcano in the South Shetland Islands (Antarctica). Since its last eruption (1970) several experiments have targeted the reconstruction of its magmatic systems. Geophysical imaging has provided new insight into Deception's interior, particularly when using space-weighted seismic attenuation tomography for coda waves. Here, sensitivity kernels have been used to invert coda wave attenuation (Qc−1). We obtain a multifrequency-dependent model of the magmatic systems at Deception Island using active data, paying particularly attention to data selection and model optimisation. The results have been framed in the extensive knowledge of the tectonics and the geomorphology of the volcano with a GIS, underlining a spatial correlation between high-attenuation anomalies and high thermal activity regions. This inter- and multi-disciplinary analysis improves the interpretation of the dynamics of Deception Island and its related hazards.
Landscape evolution of the southeastern Tibetan Plateau – Temporal and spatial relationships between glacial and fluvial landforms
Authors: Schneider Ramona A.A. , Stroeven Arjen P. , Blomdin Robin , Gribenski Natacha , Caffee Marc W. , Yi Chaolu , Xu Xiangke , Zeng Xuezhen , Hättestrand Martina , Fu Ping , Owen Lewis A.
Published: March 2020

Landscape system components interact in ways which are not yet fully understood, and in tectonically active regions it is of particular interest whether endogenic or exogenic factors are the main drivers of landscape evolution. For example, fluvial terraces may form in response to exogenic disturbances like climatic changes or to endogenic forces like tectonic uplift. This study explores how temporal and spatial correlations between end moraines (denoting the advance of glaciers due to climate change) and fluvial terraces can yield insights about exogenic-endogenic processes determining landscape evolution during the Quaternary on the southern margin of the Shaluli Shan plateau, SE Tibet, a formerly glaciated and tectonically active region. A high-resolution TanDEM-X Digital Elevation Model (12 m) was used to produce detailed geomorphological maps of glacial valleys, marginal moraines, glacial lineations, and fluvial terraces. The geomorphological mapping was complemented with geomorphological and sedimentological field observations. Samples for Optically Stimulated Luminescence dating were taken from extensive and distinct terraces located in pull-apart basins bordering the plateau and samples for cosmogenic nuclide exposure dating were collected from selected boulders on end moraines formed by valley glaciers draining the Mt Genie massif on the Shaluli Shan plateau. Infrared stimulated luminescence (IRSL) signals from feldspar multi grains aliquots, and 10Be and 26Al concentrations from quartz, were used to determine depositional ages of terraces and moraines, respectively. In combining both dating techniques, we compare the timing of glacial expansions with the depositonal ages of the terraces to tease out the effects of exogenic and endogenic drivers on terrace formation and to formulate a conceptual model of landscape evolution.
Intermediate water masses, a major supplier of oxygen for the eastern tropical Pacific ocean
Authors: Duteil Olaf , Frenger Ivy , Getzlaff Julia
Published: March 2020

Abstract. It is well known that Intermediate Water Masses (IWM) are sinking in high latitudes and ventilate the lower thermocline (500–1500 m depth). We here highlight how the IWM oxygen content and the IWM pathway along the Equatorial Intermediate Current System (EICS) towards the eastern tropical Pacific ocean are essential for the supply of oxygen to the lower thermocline and the Oxygen Minimum Zones (OMZs). To this end, we assess here a heterogeneous subset of ocean models characterized by a horizontal resolution ranging from 0.1° to 2.8°. Subtropical oxygen levels in the lower thermocline, i.e., IWM are statistically correlated with tropical oxygen levels and OMZs. Sensitivity simulations suggest that the oxygen biases of the subtropical IWM oxygen levels contribute to oxygen biases of the tropical thermocline as an increase of the IWM oxygen by 60 mmol m−3 results in a 10 mmol m−3 increase in the tropical ocean in a timescale of 50 years. In the equatorial regions, the IWM recirculates into the Equatorial Intermediate Current System (EICS). By comparing tracer and particle release simulations, we show that a developed EICS increases eastern tropical ventilation by 30 %. Typical climate models lack in representing crucial aspects of this supply: biases in IWM properties are prominent across climate models and the EICS is basically absent in models with typical resolutions of ~ 1°. We emphasize that these biases need to be reduced in global climate models to allow reliable projections of OMZs in a changing climate.
Influence of inherited structural domains and their particular strain distributions on the Roer Valley Graben evolution from inversion to extension
Authors: Deckers Jef , Rombaut Bernd , Van Noten Koen , Vanneste Kris
Published: March 2020

Abstract. After their first development in the middle Mesozoic, the overall NW-SE striking border fault systems of the Roer Valley Graben were reactivated as reverse faults under Late Cretaceous compression (inversion) and reactivated again as normal faults under Cenozoic extension. In Flanders (northern Belgium), a new geological model was created for the western border fault system of the Roer Valley Graben. After carefully evaluating the new geological model, this study shows the presence of two structural domains in this fault system with distinctly different strain distributions during both Late Cretaceous compression and Cenozoic extension. A southern domain is characterized by narrow ( 10 km) distributed faulting. The total normal and reverse throw in the two domains was estimated to be similar during both tectonic phases. The repeated similarities in strain distribution during both compression and extension stresses the importance of inherited structural domains on the inversion/rifting kinematics besides more obvious factors such as stress directions. The faults in both domains strike NW-SE, but the change in geometry between them takes place across the oblique WNW-ESE striking Grote Brogel fault. Also in other parts of the Roer Valley Graben, WNW-ESE striking faults are associated with major geometrical changes (left-stepping patterns) in its border fault system. This study thereby demonstrates the presence of different long-lived structural domains in the Roer Valley Graben, each having their particular strain distributions that are related to the presence of non-colinear faults.
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Authors: Matwyshyn Andrea M.
Published: March 2020

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Regulating Data Privacy and Use: A Key to Modern National Security?
Authors: Zwier David
Published: March 2020

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Estudio in Vitro de la frecuencia del 4° conducto radicular de la raíz mesio bucal en primeros molares superiores permanentes
Authors: Herrera Henry , De Herrera Helen , Gutiérrez José
Published: March 2020

El presente estudio "in vitro", fue realizado en la Universidad Evangélica de El Salvador, Facultad de Odontología, para determinar la frecuencia del 4' conducto de la raíz mesio bucal del primer molar superior permanente, habiéndose examinado 241 piezas extraídas. De las 241, seis fueron excluidas por no reunir los requisitos indispensables. Las piezas estudiadas fueron 235 de las cuales el 2.55% (6 piezas) presentaron calcificación de los conductos de la raíz mesio bucal (MB). 11.06% (26 piezas) presentaron 2 forámenes apicales con un conducto, 23.40% (55 piezas dentales) presentaron 1 foramen apical con dos conductos, 28.08% (66 piezas) presentaron 2 forámenes apicales y 2 conductos, 34.89% (82 piezas) presentaron un foramen apical y un conducto. Par lo tanto, se concluye, que el porcentaje total de la frecuencia del 4° conducto de la raíz mesio bucal del primer molar superior permanente de piezas extraídas fue de 51.48% (121 piezas).
Efecto de un producto de panificación elaborado con sucralosa y su influencia sobre el indice glicémico en pacientes diabéticos tipo 2
Authors: Martínez Aguilar Reina Cristina , Castillo de del Valle Nancy Raquel , Guzmán de Ascencio Ligia María
Published: March 2020

La Diabetes mellitus tipo 2 representa una problemática mundial, cuya prevalencia crece cada vez más en personas mayores de 40 años, en los que representa de 90 a195% de esta enfermedad, lo cual genera gastos considerables en los presupuestos sanitarios de un país. El objetivo del estudio fue formular un producto de panificación elaborado con surculosa (edulcorante no calórico) y fibra (avena), para reducir los niveles sanguíneos de glucosa y medir su influencia en niveles glicémicos del diabético tipo 2, así como evaluar su aceptabilidad. Se evaluaron pruebas sanguíneas pre y post prandial en 30 pacientes diabéticos, antes y después de consumir el producto de panificación, valorando su efecto en el índice glicémico. Los pacientes fueron seleccionados aleatoriamente conformando dos grupos, el experimental y el control. Se suministraron una formula con surculosa y una con sacarosa. La aceptabilidad se determinó evaluando características organolépticas como el sabor, color, textura y presentación. Los resultados demostraron que los niveles de glucosa en sangre disminuyeron en la prueba post prandial después de consumir el producto, pero estadísticamente no fueron significativos de acuerdo a la prueba t de student. Se considera que es un producto apto para la alimentación del diabético por su aporte nutricional sin azúcar de caña y con avena como fuente de fibra, puede ser incluido en las listas de sustitución de alimentos para diabéticos.
Factores prenatales e intraparto relacionados con puntaje de APGAR bajo en Hospital Nacional Zacamil
Authors: Amaya Claros Alex , Arévalo José Raúl , López Enrique
Published: March 2020

En el Hospital Nacional Zacamil se realizó un estudio Descriptivo, retrospectivo de 44 casos de madres que tuvieron hijos con puntaje de APGAR bajo al primer o al quinto minuto de vida durante el año 2004, con el objetivo de conocer la frecuencia, factores obstétricos relacionados, vía del parto y métodos de reanimación utilizados en el neonato con APGAR bajo en el servicio de Partos de dicha institución. Se encontr6 que durante el año 2004 se asistieron un total de 3,027 partos de los cuales 44 casos tuvieron APGAR de 6 6 menos representando una frecuencia de 1.4%. De los neonatos con APGAR bajo al minuto se encontró una Casa de recuperación satisfactoria mayor al 80% a los 5min. La mayor incidencia se obsero6 en neonatos de termino con peso entre rangos normales. Se concluy6 que la edad materna, prirniparidad, control prenatal incompleto o ausente, distocias de parto y cesáreas son factores de riesgo para que el recién nacido presente APGAR bajo.