bluuebunny/crossref_metadata_2025 huggingface dataset:
Hydrological response to warm and dry extremes in glacierized catchments: when and how are glaciers compensating?
Authors: Van Tiel Marit , Van Loon Anne F. , Seibert Jan , Stahl Kerstin
Published: March 2020

Extreme warm and dry summer conditions often cause low-flow situations due to the precipitation deficit and increased evapotranspiration. In glacierized catchments, however, the same extreme weather conditions can lead to a very different hydrological response, namely increased streamflow because of increased glacier melt. In larger combined rainfed and glacierfed catchments, meltwater from glaciers can, thus, buffer the adverse hydrological effects of warm and dry spells. The question is how much glacier cover in a catchment is needed to counterbalance the hydrological processes that cause a decline in streamflow. Moreover, due to climate change, glaciers have been retreating, which affects the hydrological response and the buffering effect of glaciers. In this study, we analysed long-term streamflow records of around 60 glacierized catchments in Switzerland, Austria, Norway and Canada with varying glacier coverage. In addition, a few catchments were modelled to analyse some extreme events in more detail and perform sensitivity tests. Warm and dry spells were selected based on weather data for the catchments and the corresponding hydrological responses were investigated. The events were analysed taking into account catchment characteristics, such as glacier cover and elevation information, and antecedent conditions, such as snowfall in winter and precipitation amounts in the period before the warm and dry event. Results show that during extreme warm and dry spells small glacier cover fractions (< 10%) can already alleviate the otherwise emerging streamflow drought. Moreover, we see a clustering of warm and dry periods in recent years and a decreasing trend of summer streamflow in many catchments. Antecedent conditions appear to shape the individual summer streamflow responses. Overall, understanding the hydrological responses to warm and dry spells is essential due to projected increases in weather extremes. Especially in glacierized catchments, our results imply that with changing glacier cover due to global warming, changes in the buffering capacity of glacierized catchments during warm and dry periods can be expected.
Variability of surface climate in simulations of past and future
Authors: Rehfeld Kira , Hébert Raphaël , Lora Juan M. , Lofverstrom Marcus , Brierley Chris M.
Published: March 2020

It is virtually certain that the mean surface temperature of the Earth will continue to increase under realistic emission scenarios. Yet comparatively little is known about future changes in climate variability. We explore changes in climate variability over the large range of climates simulated in the framework the Coupled Model Intercomparison Project Phases 5 and 6 (CMIP5/6) and the Paleoclimate Modeling Intercomparison Project Phases 3 and 4 (PMIP3/4). 
This consists of time slice simulations for the Pliocene, Last Interglacial, Last Glacial Maximum, the Mid Holocene and idealized warming experiments (1% CO2 and abrupt 4xCO2), and encompasses climates with a range of 12°C of global mean temperature change. We examine climate variability from different perspectives: from local interannual change, to coherent climate modes and through compositing extremes. The change in the interannual variability of precipitation is strongly dependent upon the local change in the total amount of precipitation. Meanwhile only over tropical land is the change in the interannual temperature variability positively correlated to temperature change, and then weakly. In general, temperature variability is inversely related to mean temperature change - with analysis of power spectra demonstrating that this holds from intra-seasonal to multi-decadal timescales. We systematically investigate changes in the standard deviation of modes of climate variability. Overall, no generalisable pattern emerges. Several modes do show, sometimes weak, increasing variability with global mean temperature change (most notably the Atlantic Zonal Mode), but also the El Niño/Southern Oscillation indices (NINO3.4 and NINO4). The annular modes in the Northern (Southern) hemisphere show only weakly increasing (decreasing) relationships.
By compositing extreme precipitation events across the ensemble, we demonstrate that the atmospheric drivers dominating rainfall variability in Mediterranean climates persist throughout palaeoclimate and future simulations. The robust nature of the response of climate variability in model simulations, between both cold and warm climates and across multiple timescales, suggests that observations and proxy reconstructions could provide a meaningful constraint on climate variability in future projections.
Regional flood frequency estimation for the contiguous USA using Artificial Neural Networks
Authors: Fillipova Valeriya , Leedal David , Hammond Anthony
Published: March 2020

We have recently demonstrated the utility of a machine learning-based regional peak flow quantile regression model that is currently providing flood frequency estimation for the re/insurance industry across the contiguous US river network. The scheme uses an artificial neural network (ANN) regression model to estimate flood frequency quantiles from physical catchment descriptors. This circumvents the difficult-to-justify assumption of homogeneity required by alternative ‘region of hydrological similarity’ approaches. The structure of the model is as follows: the output (dependent) variable is a set of peak flow quantiles where the distributions used to derive the quantiles were parameterised from observations at 4,079 gauge sites using the USGS Bulletin 17C extreme value estimation method (notable for its inclusion of pre-instrumental flood events). The features (regressors) for the model were formed from 25 catchment descriptors covering; geometry, elevation, land cover, soil type and climate type for both the gauged sites and the catchments related to a further 906,000 ungauged sites where peak flow quantile estimation was undertaken. The feature collection requires massive computational resource to achieve catchment delineation and GIS processing of land-use, soil-type and precipitation data.

This project integrates many modelling and computational science elements. Here we focus attention on the ANN modelling component as this is of interest to the wider hydrology research community. We pass on our experience of working with this modelling approach and the unique challenges of working on a problem of this scale.

A baseline multiple linear regression model was generated, as were several non-linear alternative formulations. The ANN model was chosen as the best approach according to a root mean square error (RMSE) criterion. Alternative ANN formulations were evaluated. The RMSE indicated that a single hidden layer performed better than more complex multiple hidden layer models. Variable importance algorithms were used to assess the mechanistic credibility of the ANN model and showed that catchment area and mean annual rainfall were consistently identified as dominant features in agreement with the expectations of domain experts together with more subtle region-specific factors.

The results of this study show that ANN models, used as part of a carefully configured large-scale  computational hydrology project, produce very useful regional flood frequency estimates that can be used to inform flood risk management decision-making or drive further hydrodynamic 2D-modelling and are appropriate to the ever-increasing scale of contemporary hydrological modelling problems.
Root system architecture with and without root hairs: Consequences for nutrient and water uptake efficiency and related spatio-temporal patterns
Authors: Lippold Eva , Phalempin Maxime , Schlüter Steffen , Mikutta Robert , Vetterlein Doris
Published: March 2020

Root hairs substantially contribute to the acquisition of nutrients and potentially also to water uptake. Hence, they might have a strong impact on plant growth under nutrient- or water-limited conditions. As little information presently exists about differences in matter uptake to plants either with or without root hairs, we hypothesize that the absence of root hairs will be compensated by an increase in root growth to overcome the hair-less handicap. Within the DFG-funded Priority Program 2089, we compare two different genotypes (i.e. Zea mays “Wild Type” and its corresponding hair-less mutant “rth3”) grown in two different substrates (loam and sand) in column experiments. X-ray computed tomography (X-ray CT) was used to investigate the spatial-temporal change of root architecture during growth. Additionally, total root length was measured after destructive sampling at harvest with WinRhizo. Contrary to our expectation, the reduced root surface area available for water and nutrient uptake in case of the hair-less cultivar was not compensated by more intensive root growth. The substrate had a higher impact on root growth than the presence or absence of root-hairs. For shoot growth (shoot biomass), both factors (genotype, substrate) had a significant impact. As a consequence, nutrient uptake efficiency (uptake per unit root length) was clearly increased by the presence of root-hairs, irrespective of the substrate. Water uptake efficiency did not show any difference between genotypes under the well-watered conditions studied. In general, water uptake per unit root length was higher in sand compared to loam. Differences in nutrient uptake efficiency should be reflected in the extent of nutrient depletion gradients around roots. To address such biochemical gradients we develop a new subsampling scheme based on extraction of undisturbed subsamples. Subsamples will be imaged with micro X-ray fluorescence (μXRF) for elemental mapping. The 2D µXRF image will be registered into the 3D X-ray CT image to relate the extent of gradients to the age of the respective root segment.

 

This project was carried out in the framework of the priority programme 2089 “Rhizosphere spatiotemporal organisation - a key to rhizosphere functions” funded by DFG (project number 403640293).
Environmental Significance of Holocene Dust Accumulation in Archaeological Hilltop Ruins in the Southern Levant
Authors: Roskin Joel , Lucke Bernhard , Vanselow Kim André , Bruins Hendrik J. , Abu-Jaber Nizar , Porat Naomi , Bäumler Rupert
Published: March 2020

Pleistocene primary and secondary loess remains cover large parts of the landscape in the Negev in Israel and have been postulated in southern Jordan, but Holocene deposits are absent. We hypothesized that archaeological structures might represent effective dust traps which preserve Holocene dust, and investigated soils developed on archaeological hilltop ruins. These were compared them with local soils, paleosols, geological outcrops, and current dust. Statistically modeled grain size end-members were identified and demonstrate that the ruin soils in both regions consist of mixtures of local and remote sediment sources that differ from dust compositions deposited during current storms. This discrepancy is attributed to fixation processes connected with sediment-fixing agents such as vegetation, biocrusts, and/or clast pavements associated with vesicular layers (similar to desert pavements). It suggests that dust deposition depends not only on supply, but that sedimentation processes play a major role. Precipitation may have contributed to dust accretion, as a snowstorm in the Petra region delivered a significantly higher amount of sediment than rain or dry deposition. Snowfall dust had a unique particle size distribution relatively similar to the ruin soils. Wet deposition and snow might catalyze dust deposition and enhance fixation by fostering vegetation and crust formation, which suggests that more frequent snowfall during the Pleistocene may have been an important mechanism of primary loess deposition in the southern Levant.
A multi-model CMIP6 study of Arctic sea ice at 127 ka: Sea ice data compilation and model differences
Authors: Sime Louise , Kageyama Masa , Sicard Marie , Guarino Maria-Vittoria , de Vernal Anne , Schroeder David , Stein Ruediger , Malmierca-Vallet Irene ,   Ayako Abe-Ouchi6, Cecilia Bitz7, Pascale Braconnot1, Esther Brady8, Matthew A. Chamberlain9, Danny Feltham4, Chuncheng Guo10, Gerrit Lohmann5, Katrin Meissner11, Laurie Menviel11, Polina Morozova12, Kerim H. Nisancioglu13,14, Bette Otto-Bliesner8, Ryouta
Published: March 2020

The Last interglacial (LIG) is a period with increased summer insolation at high northern latitudes, which results in strong changes in the terrestrial and marine cryosphere. Understanding the mechanisms for this response via climate modelling and comparing the models’ representation of climate reconstructions is one of the objectives set up by the Paleoclimate Modelling Intercomparison Project for its contribution to the sixth phase of the Coupled Model Intercomparison Project. Here we analyse the results from 12 climate models in terms of Arctic sea ice. The mean pre-industrial to LIG reduction in minimum sea ice area (SIA) reaches 59% (multi-model mean LIG area is 2.21 mill. km2, compared to 5.85 mill. km2 for the PI), and the range of model results for LIG minimum sea ice area (from 0.02 to 5.65 mill. km2) is larger than for PI (from 4.10 to 8.30 mill. km2). On the other hand there is little change for the maximum sea ice area (which is 12 mill. km2 for both the PI and the LIG, with a standard deviation of 1.04 mill. km2 for PI and 1.21 mill. km2 for LIG). To evaluate the model results we synthesize LIG sea ice data from marine cores collected in the Arctic Ocean, Nordic Seas and northern North Atlantic. South of 78oN, in the Atlantic and Nordic seas, the LIG was seasonally ice-free. North of 78oN there are some discrepancies between sea ice reconstructions based on dinocysts/foraminifers/ostracods and IP25: some sites have both seasonal and perennial interpretations based on the same core, but different indicators. Because of the conﬂicting interpretations it is not possible for any one model to match every data point in our data synthesis, or say whether the Arctic was seasonally ice-free. Drivers for the inter-model differences are: different phasing of the up and down short-wave anomalies over the Arctic ocean, associated with differences in model albedo; possible cloud property differences, in terms of optical depth; LIG ocean circulation changes which occur for some, but not all, LIG simulations. Finally we note that inter-comparisons between the LIG simulations, and simulations with moderate CO2 increase (during the transition to high CO2 levels), may yield insight into likely 21C Arctic sea ice changes using these LIG simulations.
Semi-Empirical Model for the Ka-band Sea Surface Doppler Centroid
Authors: Yurovsky Yury , Kudryavtsev Vladimir , Grodsky Semyon , Chapron Bertrand
Published: March 2020

The sea surface Doppler spectrum centroid is a principal parameter for the sea surface current retrieval from Doppler radar measurements. Satellite Doppler scatterometers are proposed to operate in the Ka-band (SKIM, DopplerScatt/WaCM, SEASTAR) in order to achieve sufficient measurement accuracy. Todays documentation of the Ka-band sea surface backscattering parameters is poor, thus this work is aimed at presenting a model for the sea surface Doppler spectrum centroid (DC) deducted from field data collected from the Black Sea research platform. The model relies on the well-known two-scale surface separation approach. Within this framework, the small-scale waves are the scatterers moving at their inherent speed (Bragg wave phase velocity or specular point velocity), which, in turn, are advected by the large-scale wave orbital velocities. These modulations lead to correlated variations of local scatterer cross-section and speed. The inherent scatterer velocity is computed theoretically, while the modulation term is described by the empirical modulation transfer function (MTF) which naturally involves both tilt and hydrodynamics components as a function of look geometry and sea state. The proposed semi-empirical DC model is in good agreement with measurements if in situ wave gauge directional spectrum is used as a wave input. Based on this finding, we extrapolate the semi-empirical DC model on the arbitrary surface described by the physical model of the wind wave spectrum. The resulting DC model is compared to the published empirical models and measurements (SAXON-FPN, DopplerScatt, AirSWOT, Wavemill field campaigns, and CDOP Envisat ASAR model). The model DC dependencies on incidence angle and wind speed are consistent with Ku-band
SAXON-FPN, Ka-band AirSWOT, and DopplerScatt datasets, but differs from C-band CDOP model and X-band Wavemill dataset, which generally have higher DC magnitude (besides longer operating radar wavelength, the difference can be attributed to swell dominated sea observed in the CDOP and Wavemill cases). The model predicts that the DC rises with wind speed at small incidence angles, 20–30o, but the DC level is almost independent of wind at larger incidence angles, 50–55o. Such behavior is explained by the balance between opposing wind dependencies of the MTF magnitude and the magnitude of modulating wave orbital velocities.

The work is supported by the Russian Science Foundation under grant No. 17-77-30019.
The Northern Hemisphere Winter Polar Jet Stream and its Connection to the Seasonal Prediction Skill of Weather Regimes over Europe
Authors: Hellmich Lara , Rautenhaus Marc , Athanasiadis Panos , Dobrynin Mikhail , Düsterhus André , Ruggieri Paolo , Baehr Johanna
Published: March 2020

Over the North Atlantic, the frequency of extreme weather events, such as storms or cold spells, is critically dependent on the prevailing weather regime. In consequence, seasonal predictability of these regimes is important. Currently, the ability of seasonal prediction systems to predict such weather regimes over Europe is limited. Weather regimes and the location of the northern hemisphere polar jet stream, hereinafter referred to as jet stream, interact with each other. Specific weather regimes are associated with a northern, central or southern position of the jet stream. Therefore, we investigate whether the relationship between weather regimes and the location of the jet stream can be used to improve seasonal winter forecasts over Europe. For our analysis, we use a seasonal prediction system based on the Max-Planck-Institute Earth-System- Model (MPI-ESM) and investigate a 30-member ensemble, as well as the global reanalysis ERA-Interim as an observational reference.

Our results show that the jet stream’s latitude is predictable per winter month with a seasonal prediction system. We also demonstrate in ERA-Interim that weather regime clusters can be directly identified via the jet stream’s position by using k-mean clustering with monthly data. Moreover our results show that the MPI-ESM reforecast ensemble represents the spatial and temporary variability of these clusters. We analyse whether predictive skill can be improved if the number of clusters represented within the reforecast ensemble at a given time is reduced. Specifically, we test whether the incorporation of the location of the jet stream into the prediction analysis improves the prediction skill of sea level pressure and Z500 in the North Atlantic area.
Time for a Plant Structural Economics Spectrum
Authors: Verbeeck Hans , Bauters Marijn , Toby Jackson , Schenkin Alexander , Disney Mathias , Calders Kim
Published: March 2020

We argue that tree and crown structural diversity can and should be integrated in the whole-plant economics spectrum. Ecologists have found that certain functional trait combinations have been more viable than others during evolution, generating a trait trade-off continuum which can be summarized along a few axes of variation, such as the “worldwide leaf economics spectrum” and the “wood economics spectrum”. However, for woody plants the crown structural diversity should be included as well in the recently introduced “global spectrum of plant form and function”, which now merely focusses on plant height as structural factor. The recent revolution in terrestrial laser scanning (TLS) unlocks the possibility to describe the three dimensional structure of trees quantitatively with unprecedented detail. We demonstrate that based on TLS data, a multidimensional structural trait space can be constructed, which can be decomposed into a few descriptive axes or spectra. We conclude that the time has come to develop a “structural economics spectrum” for woody plants based on structural trait data across the globe. We make suggestions as to what structural features might lie on this spectrum and how these might help improve our understanding of tree form-function relationships.
Noble gas monitoring at the seemingly inactive Ciomadul volcano, Eastern Carpathians, Romania
Authors: Kis Boglarka-Mercedesz , Harangi Szabolcs , Palcsu László , Hegyeli Botond
Published: March 2020

The Ciomadul volcano is the youngest volcano (32 ka) built by the Neogene volcanism in the Carpathian-Pannonian Region. This volcanic area is characterized by intense gas emissions (Kis et al., 2017) (CO2, CH4, H2S) in the form of bubbling pools, mofettes and mineral water springs. The isotopic compositions of carbon, 13CCO2 up to -3‰ VPDB and helium up to 3.1 Ra suggest magmatic origin of the gas up to 80% (Kis et al., 2019).

Although the volcano seems to be inactive, several features, petrologic and geophysical studies suggest that melt-bearing magmatic body could still exist beneath the volcano (Harangi et al., 2015). Moreover the geodynamic system is characterized by frequent earthquakes with magnitude up to 7 at Vrancea area, close to the CO2-rich gas emissions of Ciomadul and the neighbouring areas.

In 2015 we started the monitoring of the helium isotopic ratios of Ciomadul to chech the possible relationship with seismicity. Our results show that in several cases the helium isotopic ratios increase at a seismic event with magnitude between 4 and 5.8 suggesting a relationship between the two phenomena.

 

Harangi, Sz., Lukács, R., Schmitt, A.K., Dunkl, I., Molnár, K., Kiss, B., Seghedi, I., Á. Novothny, Molnár, M. 2015, Constraints on the timing of Quaternary volcanism and duration of magma residence at Ciomadul volcano, east-central Europe, from combined U-Th/He and U-Th zircon geochronology, Journal of Volcanology and Geothermal Research, 301, 66-80

Kis, B.M., Ionescu, A., Cardellini, C., Harangi, Sz., Baciu, C., Caracausi, A; Viveiros, F. 2017, Quantification of carbon dioxide emissions of Ciomadul, the youngest volcano of the Carpathian-Pannonian Region (Eastern-Central Europe, Romania), Journal of Volcanology and Geothermal Research, 341, 119–130

Kis, B.M., Caracausi, A., Palcsu, L., Baciu, C., Ionescu, A., Futó, I., Sciarra, A., Harangi, Sz. 2019, Noble gas and carbon isotope systematic at the seemingly inactive Ciomadul volcano (Eastern-Central Europe, Romania, Geochemistry, Geophysics, Geosystems, 20, 6, 3019–3043

This research belongs to the scientific project supported by the OTKA, K116528 (Hungarian National Research Fund), the EU and Hungary, co-ﬁnanced by the European Regional Development Fund in the project GINOP-2.3.2-15-2016-00009 ‘ICER’ and the Deep Carbon Observatory.
Traces of the Rochechouart Asteroid Impact in the uppermost Triassic sediments of the NE Paris-, Aquitanian- and Lodève Basin
Authors: Kuhlmann Natascha , Thein Jean , Nagel Thorsten , Colbach Robert
Published: March 2020

The end-Triassic extinction event just below the Triassic/Jurassic boundary and its dramatic paleoenvironmental and paleogeographical variations are well documented by rapid changes in the sedimentological and geochemical composition of the uppermost Triassic and lowest Jurassic sequence in the NE Paris Basin. 

An outstanding horizon in the Middle Rhaetian of the Paris Basin is the result of the effects generated by the asteroid impact of Rochechouart (~50 km large crater, ~201 Ma old). The asteroid hit the variscan basement at the southern margin of the Paris Basin, near the town of Limoges (France). This horizon starts at its base with seismically deformed alternation of siltstones and quartzites (seismite), which represent the result of a mega earthquake, generated during the initial impact phase. The seismite is overlain by a completely unsorted conglomerate, fining upwards into a strongly folded and sheared silt/clay with numerous vertebrate bones and ends at the top with a thick red clay formation of the Upper Rhaetian.

The horizon above the seismite obviously represents the deposits of a large tsunami (called tsunamite), triggered when the enormous ejecta masses of the impact entered the waterbody of the southern Paris Basin. Indicators for this event are not only the remains of the reworked vertebrates and exotic sedimentological structures. Additionally the enrichment of platinum group elements which was found in the sequence, clearly points to an impact with cosmic material being involved. The layer can be observed from the Eifel (Germany) over Luxembourg to Lorraine (France). Thickness, sedimentological structures and the lithological composition differ locally, mainly depending on the former geomorphological situation.

Here we present similar impact horizons in two other sites from France: in the northern Aquitanian Basin near Brive-la-Gaillarde (which is in a close distance to the crater) and in the southern Lodève Basin (at a larger distance and in carbonatic rocks). Intensive research in these areas is still in progress.  

The excellently conserved Rochechouart impactite in the Rhaetian of the Paris Basin and surrounding regions offers a unique chance to study in all detail the processes of a large impact with their effects on the adjacent marine sedimentation areas and to compare the results to similar events  worldwide.

 
Drought stress memory in filamentous soil fungi
Authors: Guhr Alexander
Published: March 2020

Drought is a common stressor for soil organisms. One adaptive mechanism is “stress priming”, the ability to cope with a severe stress (“triggering”) by retaining a memory from a previous mild stress event (“priming”). While plants have been extensively investigated for drought memory, only scare information is available for filamentous soil fungi and its implications for soil microbial communities. We investigated the potential for drought-induced stress priming on single species as well its effect on microbial communities in forest A-horizons. Batch experiments with 4 treatments were conducted: exposure to priming and/or triggering as well as non-stressed controls. A priming stress was caused by desiccation to pF 4. The samples were then rewetted and after a recovery time of up to 14 days triggered (pF 6). After triggering, microbial biomass and activity as well as microbial communities by rDNA sequencing were analysed.

Some filamentous fungi show the potential for drought-induced stress priming leading to increased survival rates and activity under severe stress events. Yet, the effect seems to be species specific with potentially high impact on composition and activity of microbial communities considering the expected increase of drought events. Especially receptive to stress priming seem to be species within the fungal classes Mortierellomycetes, Pezizomycetes, and Tremellomycetes. Shifts in the microbial community compositions could be observed in some cases in response to stress priming. In general, the nature of the response depends on the original composition of the microbial community and the occurrence of a subsequent triggering event. For example, species investing high amounts of resources into the primed state only prevail if a triggering occurs (especially noteworthy was Byssonectria fusispora).
Comparing catchment scale subsurface celerities estimated from recession analysis and infiltration experiments.
Authors: Skaugen Thomas , Møen Knut , Boje Søren
Published: March 2020

Catchment scale hydrological models all have some representation of the dynamics of subsurface flow and hence direct or indirect estimates of the celerities (velocities) involved. Parameters representing these celerities (for example recession coefficients of linear reservoirs) are often calibrated against runoff instead of being estimated directly from measured data. Such a procedure, when applied for hydrological models with (too) many parameters to be calibrated, may lead to unrealistic estimates of subsurface celerity due to equifinality issues. Our aim with this study is to obtain an estimate of the distributions of subsurface celerites corresponding to the distribution of saturation levels through recession analysis. Using the recession characteristic Λ=log(Q(t)/Q(t+∆t) and looking for sequences of recession in a moving average filtered time series of runoff, we find, for many catchments, no clear structure in the relationship between Q(t) and Λ.  In order to better understand the recession process we let the runoff be represented by four (parallel) unit hydrographs (UH) of different temporal scales. The UHs thus represent different subsurface celerities through their different temporal scales and different levels of saturation.  Only when there was a systematic build up of saturation from below, i.e. the slowest UH had to be filled to (a chosen max) capacity before the next UH received water, a clear structure between Q(t) and Λ emerged, where for each value of Q(t) the maximum Λ represented the true recession to be used for estimating the celerity.  At the tiny Muren catchment (7500 m2) in southern Norway we performed an infiltration test and estimated the saturated hydraulic conductivity to be 0.00045 m/s. The mean celerity estimated from recession analysis for the same catchment was found to be 0.00034 m/s, and when the distribution of celerities from the recession analysis was used in the Distance Distribution Dynamics (DDD) rainfall runoff model a Kling Gupta efficiency criterion of KGE = 0.86 was obtained for runoff simulations at 15 minutes temporal resolution.
Preparations for the ITRF2020 at TU Wien
Authors: Zessner-Spitzenberg Anna , Mayer David , Hellerschmied Andreas , Mikschi Markus , Böhm Sigrid
Published: March 2020

The next International Terrestrial Reference Frame (ITRF), ITRF2020, will be released in early 2021 and preparations are entering the final phase. It will be realized by using the observations of the space geodetic techniques Very Long Baseline Interferometry (VLBI), Global Navigation Satellite Systems (GNSS), Satellite Laser Ranging (SLR), and Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS).
The Vienna VLBI group is planning to contribute to the ITRF2020. This poster will present the goals, the methodology and preparations for our contribution. In order to analyse the VLBI observation sessions, the Vienna VLBI and Satellite Software (VieVS) will be used. The poster will focus on the influence of applying the gravitational deformation and the atmospheric loading on the individual solutions and the ITRF.  For this purpose, a selected list of more than 800 sessions of the last 40 years, which was released by the International VLBI Service for Geodesy and Astrometry (IVS) to verify the latest changes in the implementation, will be analysed and the results will be presented.
Greenhouse Gas Analyzing Platform using Ground Sites, Aircraft, Ships, and Satellite-based Data: Japan's Contribution to the Paris Agreement
Authors: Saigusa Nobuko , Machida Toshinobu , Nakaoka Shin-ichiro , Matsunaga Tsuneo , Tanimoto Hiroshi , Niwa Yosuke , Terao Yukio , Ito Akihiko
Published: March 2020

Asia, as one of the world’s largest greenhouse gas (GHG) emitters, has a responsibility to play an important role to turn the goals of Paris Agreement into reality. Urgent needs in Earth observations for GHGs are to reduce uncertainties in their source and sink estimations and to identify current knowledge gaps and requirement for further international collaboration. Estimating anthropogenic and natural emissions based on observations for GHGs has a great potential for providing additional sources of information that can support estimating the impacts of mitigation actions. Discussions will be focused on current status and challenges from Japan's relevant GHG observation and analysis to improve up-to-date analysis systems and data coverage particularly in Asia–Oceania for better estimation of the distribution of anthropogenic and natural sinks and sources with sufficient accuracy.
Dust and Black Carbon size distributions in snow and some links to snow physics.
Authors: Voisin Didier , Witwicky Julien , Tuzet François , Osmont Dimitri , Dumont Marie
Published: March 2020

Snow contain many insoluble particles, some of which can absorb light (such as mineral dust and black carbon) and are responsible for a large climate forcing, both directly through their influence on snow albedo and indirectly by inducing snow metamorphism – albedo feedbacks.

Light absorbing particles (LAPs) influence snow metamorphism and melting by changing the heat distribution in the snowpack. Conversely, some physical processes in snow influence the size distribution of LAPs in the snowpack: for example, melting partially redistributes the particles and dry metamorphism can induce vertical movement of particles. Yet, few studies investigate those couplings due to the scarcity of detailed physical and chemical characterization of snow.

 During two consecutive winters, such detailed characterization of snow was conducted at a high altitude site in the Alps (col du Lautaret, 2058m a.s.l.). The physical properties used here include detailed profiles of snow types enabling to investigate links between LAPs size distribution and snow evolution.

Size distributions analysis shows that for both black carbon (BC) and mineral dust, concentrations are often underestimated due to a significant fraction of particles being too big to be detected by the instruments. The median value of this undetected fraction is at least 20% for dust and at least 5% for BC. In more than 10% of the samples, It even exceeds 60% for dust and 25% for BC.

We then used stratigraphic data to explore the impact of partial melt and refreeze on LAP size distributions through an hypothetic coagulation mechanism induced by freeze-thaw cycles. No visible effect was found for dust, due to the higher variability of deposited particles size distributions. Conversely, freeze-thaw cycles seem to lead to a slight shift of BC size distributions toward the big particles.
Connecting deviated and vertical deep boreholes to enhance the extraction of geothermal energy - case study
Authors: Chen Chaofan , Cai Wanlong , Kolditz Olaf , Shao Haibing
Published: March 2020

Recently, an Enhanced U-type Borehole Heat Exchanger (EUBHE) system has been installed in Xi’An, China. The EUBHE system is composed on one vertical and a second deviated borehole. The bottom ends of them are connected at a depth of 2.5 km and form a closed “U-type” loop system. During the heating season, water is circulated through the two boreholes to extract geothermal energy for building heating purpose. In this work, a numerical model was developed based on the OpenGeoSys (OGS) software, in which the boreholes of the EUBHE system are represented by the line elements and the soil/rock surrounding them is discretized with 3D prism elements. With this dual-continuum model, the operation of the EUBHE system can be efficiently simulated, particularly for long-term scenarios. The developed numerical model was verified against analytical solution in a benchmark proposed by Ramey. To simulate the long-term operation of EUBHE, a Direchlet-type boundary was imposed at the inlet of the system. Temperature difference between inlet and outlet were calculated based on the building thermal demand. The impact of parameters of the vertical and deviated boreholes and flow rate of the circulating water are further investigated. Preliminary modelling results showed that the sustainable specific heat extraction rate of the EUBHE system can reach up to 200 W/m. With higher grout and pipe conductivities, the system performance will be improved. The heat extraction efficiency of EUBHE system is higher than the traditional Deep Borehole Heat Exchangers (DBHE). However, electricity consumption from the circulating pump is elevated. The developed numerical model presented in this work can also be utilized for the design and optimization of the EUBHE system.
Comparison of two methods for optimizing existing groundwater monitoring networks: application to the Bacchiglione Basin, Italy
Authors: Sottani Andrea , Meggiorin Mara , Ribeiro Luís , Rinaldo Andrea
Published: March 2020

In the presence of a groundwater monitoring network (GMN) of sensors aimed at measuring the hydraulic head in a given domain, the statistical analysis of time series not only provides insight into the general aquifer behaviour, but it can also return parameters useful to optimize and enhance the GMN’s efficiency.

Several methods to design new GMNs are available, but few of them are useful for optimizing existing networks. This study compares two methods in order to define pros and cons of their applicability and effectiveness.

They are carried out for the case study of the alluvial basin of the Bacchiglione river, near Vicenza (Veneto, Italy). The existing network comprises 92 groundwater data-loggers, installed in wells screening mostly the unconfined aquifer.

The first simple method, here proposed, is based on the Pearson correlation coefficient and the microscale parameter, which shows the time interval in which data are perfectly correlated. The coefficients were calculated between detrended time series. Firstly, based on the correlation coefficient threshold of 0.95, areas of intercorrelated couples are defined. They are characterized by similar hydrological behaviour, therefore it is sufficient to constantly monitor only one location in each area, while other interesting correlated points can be measured manually at longer sampling time. The microscale can be used to estimate this sampling time in order to see the water table trend (between 7 and 78 days in this domain), even if shorter oscillations are obviously missed and some peaks could remain unseen. This way, extra sensors can be moved to other critical areas, in order to improve the system knowledge.

The second method defines the seasonal Mann Kendall (sMK) test for detecting monotonic trends, that are used into Principal Component Analysis (PCA). Finally, a Hierarchical Clustering Analysis is carried out to group sensors with similar factors of the PCA. This method is more articulated than the previous one and entails some informed choices to be made about the distance measure and the clustering algorithm. Thanks to the sMK test and the PCA, a high insight of the system is achieved, however the clustering result may strongly variate depending on the expert’s knowledge and expectation.

The two proposed statistical analyses of hydrogeological data provide integrative decision support to improve representativeness and effectiveness of monitoring networks aimed at both qualitative and quantitative groundwater control.
A consistent multi-method global extreme event attribution framework
Authors: Haustein Karsten , Strauss Benjamin , Li Sihan , Otto Friederike
Published: March 2020

In order to streamline observational and global climate model based extreme event attribution techniques, we propose a multi-method framework which drastically increases the robustness of rapid attribution studies, hence further facilitating the communication of extreme weather related risks across the globe.

We use advanced observational datasets for temperature (Berkeley Earth) and rainfall (CPC), together with CMIP5 simulations and the large HadRM3P ensemble from the weather@home project (W@H) Recent (Climatology) and current/future warming scenarios (1°C, 1.5°C, 2°C, 3°C and 4°C) are juxtaposed to pre-industrial (Natural) baseline conditions.

Two scaling approaches are applied to the observational data to estimate the statistics of future warming scenarios. One in which percentiles of the metric of interest (Tmax, Tmin, Precip) are scaled with Global Mean Surface Temperature (GMST) and another in which the mean is scaled against GMST. Model subsetting (similar to the HAPPI experiment) as function of GMST is applied to the CMIP5 data in order to assign the warming thresholds. W@H scenarios are prescribed to achieve the desired warming threshold. We analyse the results in terms of classes of events, using percentiles, absolute and return-time based thresholds. Before the subsetting, model biases are removed means of quantile-mapping (both for CMIP5 and W@H).

The results between both scaling methods and model subsetting are mostly consistent across many regions and virtually for all temperature thresholds under consideration. The percentile-based scaling method does, however, reveal that the tail of the distributions (highest Tmax, lowest Tmin) has potentially widened with warming. Overall, we find that historically rare extreme events become increasingly common in the future as far as Tmax and Precip is concerned. In contrast, cold extremes become increasingly rare.
Large-wavelength deformation across the central Andean plateau interpreted from Salar de Uyuni (Bolivia) paleoshorelines
Authors: Zeilinger Gerold , Jara-Muñoz Julius , Weiss Jonathan R. , Lee Esther
Published: March 2020

The Salar de Uyuni spans almost the entire width of the Bolivian Altiplano, thus providing a potential record of large wavelength deformation, which can be produced by various mechanism across the central Andean plateau interior. This study focuses on the mapping of paleo-lake terraces, which are geomorphic markers that represent past lake level positions and can be used to study differential vertical deformation. High-resolution TanDEM-X topography for the region, in combination with satellite imagery, reveal a wide range of well-preserved lake terraces in the Salar. Eleven prominent terraces have been identified in the study area at elevations ranging from 3701 m to 3815 m and with ages ranging from ~11.7-16.1 ka based on correlation with published ages. The elevation difference between the younger terraces (Level 1 to 5) is ~51 m in the west and ~46 m in the east, indicating an eastward tilting of about ~5 m across the Salar de Uyuni. The older terraces (Level 8 to 11), however, record an elevation difference of ~20 m in the west and ~ 24 m in the east, indicating a westward tilt of ~4 m. Thus a change in the polarity of tilting of the Uyuni paleo-lake basin occurred between the formation of terraces 5 to 8 from 13.1-14.8 ka.

We discuss different mechanisms that might drive this large wavelength deformation including 1) eastward tilting as a direct consequence of horizontal shortening in a compressional setting and “backtilting” by stress release during thrusting on a deep-seated structure, 2) addition of differentiated igneous bodies derived from the mantle perhaps associated with delamination processes, and 3) seismic coupling along the Chile subduction zone margin. Removal or delamination of mantle lithosphere is unlikely to produce 4 m of uplift in the relatively short, ~2 ka time span of our observations. Well-documented megathrust coupling and the subduction zone seismic cycle would explain the short time span but is unlikely to create significant vertical deformation ~200 km from the coast. We favour and explore the hypothesis that Andean shortening leads to large wavelength flexure (as the expression of an elastic deformation) as a result of strain accumulation that is eventually released by slip along structures beneath the Eastern Cordillera that are perhaps related to the active decollement and fold-and-thrust belt that comprise the Subandean ranges. The observed pattern of paleo-lake terraces may serve as a geologic archive recording a phase of major backarc seismic activity at ~14 ka.
Pleistocene shifts of the Subarctic Front in the North Pacific: Evidence from planktonic foraminiferal proxy data
Authors: Jacobi Lara , Nürnberg Dirk , Chao Weng-si , Tiedemann Ralf , Lembke- Jene Lester , Saavedra Pellitero Mariem , Frederichs Thomas , von Dobeneck Tilo
Published: March 2020

The North Pacific plays a key role in shaping the Earth’s climate, yet there still is a lack in understanding the complex interplay of atmosphere and ocean, and their respective circulation patterns reacting to a varying Pleistocene climate. Proxy records established on marine sediment core SO264-28-2, recovered from the Emperor Seamount Chain (Suiko Seamount; ~45°N, close to the Subarctic Front) during R/V SONNE Cruise SO264 in 2018, allow to reconstruct changes of surface and subsurface water masses in order to provide unique insight in spatial and temporal shifts of North Pacific Subarctic vs. Subtropical gyres. According to the preliminary age model based on radiocarbon dating, benthic oxygen isotopes, combined magneto-, tephra- and biostratigraphical approaches, the only 7 m long core covers the last ~1.35 Myr. This core was chosen due to its highly characteristic pattern in magnetic susceptibility and a prominent lithological change from carbonate oozes to more siliciclastic sediment sequences at ~1.2 Ma. Thus, numerous other cores from the study area can be correlated with it suggesting this core as a reference record for the North Pacific.

A continuous and synchronous cooling of both surface and subsurface ocean temperatures since ~1.35 Ma changed rapidly at 1.2 Ma to a continuous warming surface from <4 °C to ~ 8 °C while subsurface temperature remained constant below 4 °C. The long-term diverging temperatures and increasing salinities at both surface and subsurface point to the continuous northward displacement of the Subarctic Front and an increased influence of the North Pacific Tropical Water at Suiko Seamount, with most prominent, millennial-scale, changes of the gyre system and the related Kuroshio Current during interglacials. Around ~430 ka, the influence of warm and saline subtropical surface water masses declines, reflected by a rapid decrease of sea surface temperatures of 4-5 °C and a salinity inversion, whereby the subsurface water mass becomes more saline than the surface water. After ~430 ka, interglacials are very pronounced and with the prominent presence of low saline and cooler surface waters, conditions are similar to present.