bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparing different error structures in MixSIAR analysis using artificial mixtures from real sediment sources
Authors: Ovando-Fuentealba Luis , Taylor Alex , Clason Caroline , Bravo-Linares Claudio , Blake William
Published: March 2020

Within a catchment context, statistical models are widely used to predict the load of pollutants (i.e. fine sediments, chemicals compounds) from potential sources around it, into a main channel (mixture). MixSIAR is a Bayesian mixing model framework that has been used in many environmental studies. As with other models, it presents some assumptions that might be assessed before its use. In this study, a set of artificial mixtures (from real sources) were created using four different catchment sediment sources (Channel Bank; Cultivated land; Pasture and Road Material). The material collected from each source was sieved (<63um) then analysed via WD-XRF for elemental composition. The data collected from this analysis was used to test and assess the main model parameters within an experimental context. A simple range test was performed to initially select tracers that were potentially good predictors. In the end, the model was structured with 43 tracers (elements) using the mean and standard deviation among 10 replicates. Furthermore, it was run using 10^6 iterations (length of the chain) and two different error structures to be compared (residual vs multiplicative error). The results demonstrated the accuracy of the MixSIAR approach to get the real composition in different mixture combinations using a large number of tracers, although in some mixtures a statistically different value was observed where the source term with highest internal variability was present in larger proportion (frequently when %CB >10%). The most precise and reliable results based on convergence were those using the “Residual error” structure, where the value of each mixture was closer to the real and model convergence was achieved more easily. On the other hand, “Multiplicative error” structure led to longer model run times (due to its complexity) and in most cases the model did not converge as for the “Residual error” structure when using the full set of tracers. To mitigate this problem, a posterior tracer selection based on diagnostic information was devised which made it  possible to increase dramatically the convergence of the predicted parameters without a significant difference in the result. Although the “Residual error” structure showed to be the most convenient for further analysis, the technique applied for “Multiplicative error” structure can be used as a potential solution to achieve model convergence while reducing model runtime.
Insights into a pulsing debris flow
Authors: Nagl Georg , Hübl Johannes , Kaitna Roland
Published: March 2020

The internal deformation behavior of natural debris flows is of interest for model development and model testing for debris-flow hazard mitigation. The pulsing nature of debris flows can increase the runout length by remobilization of deposited material. Up to now, only a view attempts were made to measure internal deformation behavior in natural debris-flow surges due to the low predictability and high destructive power of these flows.  In this contribution we present recent advances of measuring in-situ velocity profiles together with flow parameters like flow height, basal normal stress, and pore fluid pressure. For that a fin-shaped monitoring barrier was constructed in the Gadria creek (IT), laterally carrying an array of paired conductivity sensors. We present results from a debris-flow event in 2019 with 20 surges and flow heights up to 2 m. We observe changing velocity profiles during the passage of the surges and identify deposition and remobilization domains in the flow. The flows exhibited significant longitudinal changes of flow properties like flow height and density. The liquefaction ratios reached values up to unity in some sections of the flows. Between surges, the lower levels of the flow deposited and were subsequently overridden by the next surge and reactivated. These measurements gain new insights of the dynamics of surges of a real-scale debris flow.
Effects of nitrogen deposition on greenhouse gas fluxes from the soil: results from an innovative experimental design
Authors: Bortolazzi Anna , Ventura Maurizio , Panzacchi Pietro , Fornasier Flavio , Mondini Claudio , Tonon Giustino
Published: March 2020

In the last decades, the effects of nitrogen (N) deposition on temperate forests have received much interest. Studies recorded several changes in soil carbon (C) and N cycles due to extra reactive N available. For instance, past studies reported that N deposition, may influence CO2 emission, lower CH4 consumption by the soil and increase the emission of N2O. Nevertheless, the mechanistic understanding of these ecological responses is still far to be reached. However, most of the studies neglected to include the canopy interception in the experiments simulating N addition, notwithstanding tree canopy have shown to change both the amount and the chemical composition of the N deposition. Hence, experiments simulating this process by applying fertilization above the canopy are needed.

The aim of this study is to explore how N deposition influences greenhouse gas (GHG) emissions in a temperate oak forest (Quercus petraea Liebl.) located in Monticolo (Bolzano, Italy). In this site, a set of three plots was created and replicated three times. Each set includes a control plot, a plot with below-canopy fertilization (NBL) and a plot with above-canopy fertilization (NAB). The fertilization is applied, since 2015, from May to September, for a total annual N addition of 20 kg N ha-1.

Since April 2018, CO2 emission has been monthly measured with a portable infrared gas analyzer. Measurements were performed on three points per plot, for a total of 27 measurement points. During measurements, soil moisture and soil temperature at 10 cm depth were measured as well.

The measurements of CH4 and N2O started during the growing season in 2019 and are performed on a monthly basis by a static chamber method. Three chambers were installed per plots, for a total of 27 chambers.

We will present the preliminary results of this study. The results showed that the 5-year N fertilization did not lead to significant differences between plots in terms of GHG fluxes. The sensitivity of CO2 emission to temperature was not influenced by extra N. The differences were not significant between fertilized and unfertilized plots, nor between the two fertilization methods.
Copernicus Data Infrastructure NRW
Authors: de Wall Arne , Remke Albert , Fechner Thore , van Zadelhoff Jan , Müterthies Andreas , Müller Sönke , Klink Adrian , Hinterlang Dirk , Herkt Matthias , Rath Christoph
Published: March 2020

The Competence Center Remote Sensing of the State Agency for Nature, Environment and Consumer Protection North Rhine-Westphalia (LANUV NRW, Germany) uses data from the Earth observation infrastructure Copernicus to support nature conservation tasks. Large amounts of data and computationally intensive processing chains (ingestion, pre-processing, analysis, dissemination) as well as satellite and in-situ data from many different sources have to be processed to produce statewide information products. Other state agencies and larger local authorities of NRW have similar requirements. Therefore, the state computing center (IT.NRW) has started to develop a Copernicus Data Infrastructure in NRW in cooperation with LANUV, other state authorities and partners from research and industry to meet their various needs. 

The talk presents the results of a pilot project in which the architecture of a Copernicus infrastructure node for the common Spatial Data Infrastructure of the state was developed. It is largely based on cloud technologies (i.a. Docker, Kubernetes). The implementation of the architectural concept comprised as a use case of an effective data analysis procedure to monitor orchards in North Rhine-Westphalia. In addition to Sentinel 1 and Sentinel 2 data, the new Copernicus Data Infrastructure processes digital terrain models, digital surface models and LIDAR-based data products. Finally we will discuss the experience gained, lessons learned, and conclusions for further developments of the Copernicus Data Infrastructure in North-Rhine Westphalia.
The relative importance of environmental drivers on the growth of Norway spruce depends on soil types: A case study from Saxony and Thuringia, Germany
Authors: Seltmann Christian Torsten , Wernicke Jakob , Petzold Rainer , Baumann Martin , Münder Kristian , Martens Sven
Published: March 2020

In forest management and sience it is important to determine the drivers of tree growth and to quantify their relative importance with regard to forest site characteristics. The growth of individual trees depends on complex interactions between biotic and environmental drivers. Forest management can make use or buffer the effects of biotic drivers, e. g. through thinning strategies. However, large uncertainties emerge from environmental drivers and its effects on tree growth.

The aim of this study is to quantify the relative importance of environmental drivers (climate, soil, and terrain attributes) on the growth of Norway spruce trees (Picea abies (L.) Karst.). For that purpose we distinguished three common soil types of Saxony and Thuringia, Germany (Cambisols, Podzols and water-influenced soils, i.e. Gleysol, Planosol, Stagnosol). We used national forest inventory data, regionalized climate data and terrain inferred parameters with a Boosted Regression Tree (BRT) approach. The approach is particularly suitable, since BRT quantify the relative predictor importance, considering non-linearities and interactions among predictors.

The results of this study clearly demonstrate the importance of soil properties on the growth of Norway spruce trees. Terrain attributes and temperature are similarly important for Norway spruce growth on Cambisols and Podzols, whereas spruce growth is mainly influenced by the relative sand content of the soil, the available field capacity and terrain attributes on water-influenced soils. Interactions among environmental drivers are most relevant on Cambisols and Podzols but not on water-influenced soils. Thus, the implementation of the results in growth models of high spatial resolution will support decision making in forest management.
Recent advances in vulnerability assessment for the built environment exposed to dynamic flooding
Authors: Fuchs Sven , Papathoma-Köhle Maria , Schinke Reinhard , Ortlepp Regine , Keiler Margreth
Published: March 2020

Regardless of the frequency and magnitude, the consequences of flood hazards are strongly connected to the vulnerability of elements at risk (e.g. buildings, people, and infrastructure). It is, therefore, obvious that an analysis and quantification of vulnerability is required for successful risk reduction. Vulnerability is multidimensional (physical, social, economic, institutional, etc.), however, the primary driver of direct costs and threat to human lives is the physical one. We focus here on the physical vulnerability of buildings subject to dynamic flooding occurring in mountain environments. These processes include debris floods, fluvial sediment transport, and debris flows. Furthermore, we included flash flood hazards if these are related to torrential catchments.

Physical vulnerability to dynamic flooding in mountain areas is a topic that has been under scientific investigation over the last 20 years. Several methods to assess physical vulnerability of buildings towards flash floods, debris flows and hyper-concentrated flows can be found in the literature. The plethora of methods and approaches may be classified under the following three categories: vulnerability matrices, vulnerability curves and vulnerability indices. We provide a short review of these methods which became available over the last decade and which dominate the scientific debate in mountain hazard risk management, giving an emphasis to vulnerability curves. The approaches presented herein are highlighted through case studies from the mountain areas of Europe and beyond, and challenges in vulnerability assessment including data requirements, need for improved event documentation, uncertainties and challenges related to future climate and socio-economic changes are outlined. Finally, a discussion on progress-driving factors such as new technologies (e.g. mobile apps, drones), citizen science and new innovative assessment methods is provided.
Reconstructing the climate of Ancient Babylonia
Authors: McGovern Rhonda , Kostick Conor , Farrelly Laura , Ludlow Francis
Published: March 2020

Ancient Babylonia is a kingdom / province in the Fertile Crescent in south-central Mesopotamia (modern day Iraq). It has a rich textual and archaeological history and is the origin of many scientific and cultural advances, such as the definition of the seven-day week, the invention of zero, and many legal principles still underlying modern contract, tort, criminal, property, and family law.

The Irish Research Council-funded “Climates of Conflict in Ancient Babylonia” (CLICAB) project aims to investigate climatic changes in Babylonia during the final eight centuries BCE and assess for linkages to patterns of violence and conflict, through the application of methods from historical climatology to the wealth of data available. Although there are gaps in the recorded observations, and potentially more tablets yet to be found and translated, the 209 precisely dated, transliterated and translated tablets presently available will provide for many years a sub-daily window into the weather, and therefore the climate of this key historical region. This is a far greater resolution than is currently available for any region or period in the Ancient world, and indeed unprecedented in the world of historical climatology before the Early Modern Period.

Key to the project’s broader aims is the reconstruction of the climate for the region based on the information held in the Babylonian Astronomical Diaries. This paper thus examines the process of mining information from the detailed record maintained by Ancient Babylonian scribes in the Astronomical Diaries and presents an overview of the findings. These diaries are a collection of cuneiform tablets spanning 652-61BC, housed in the British Museum. They are rich in systematic weather observations (even down to an hourly resolution), astronomical phenomena, price data, and river heights for the Euphrates. Much work has been undertaken to examine the economic, astronomical and fluvial data, but until now the weather observations have remained relatively untouched, despite their unparalleled temporal resolution for this period, the systematic methodology applied in their recording, and the sheer breadth of information provided. This ranges from wind direction and intensity, to the level of cloud cover and references to atmospheric clarity (clear vs. dusty skies), to the general conditions (temperature and precipitation), for all seasons. This project will see the reconstruction of the climate for the region of Babylonia, and therefore provide one of the oldest weather records in the world. This paper presents high-resolution weather data from the Astronomical Diaries. Specifically, the authors will present the frequency of meteorological extremes over the period, alongside a discussion into the mitigation methods the Babylonians employed to reduce their vulnerability to these extremes. 

KEYWORDS: Ancient Babylonia, Climate, Conflict
Water of garnet in Dabie UHP eclogite: implication for fluid action in continental subduction zone
Authors: Chen Ren-Xu , Wang Zhi-Min , Zheng Yong-Fei , Gong Bing
Published: March 2020

Nominally anhydrous minerals are major components of the subducted continental slab and thus regard as important water reservoir in continental subduction zone. The water contents of NAMs are critical for understanding of fluid action and geodynamics of subduction zones. Fourier Transform Infrared Spectroscopy as well as major and trace element analyses were carried out on garnets in Jinheqiao eclogites from the Dabie orogen. The results demonstrate that garnet grains contain both molecular water and hydroxyl (OH). Contents of both hydroxyl and molecular water show rough correlation with Si, Ca, Al and Na, suggesting their incorporation in garnet is related to the formation of garnet. Molecular water is primary or transformed from hydroxyl during exhumation, implying molecular water an internal origin in eclogite. Garnet has varying total water contents up to thousands, with the highest water content corresponding to the garnet’s capacity for water storage under subduction zone condition. Water can be saturated in peak metamorphic garnet. The variable water contents in garnet was affected by several factors such as protolith nature, fluid availability, pressure and temperature, but dominated by decompression dehydration during exhumation. The high water contents of garnet suggest that garnet is not only an important media for subducted slab to transport water into deep mantle but also an important source for retrograde fluid during exhumation of deeply subducted continental slab.
Post-storm recuperation as a stepping-stone towards long-term integrated modelling in steep beaches
Authors: Kombiadou Katerina , Costas Susana , Roelvink Dano , McCall Robert
Published: March 2020

Integrated modelling approaches for the evolution of the entire dune-beach system have become increasingly sought-after, not only for management purposes, but also to allow better understanding of the feedbacks between processes and scales and a closer approximation of where critical system thresholds may lie. The effective reproduction of both destructive and constructive processes over a broad spectrum of temporal scales is crucial to any, such, integrated approach. Recent improvements of the XBeach-Duna model regarding approximation of nearshore processes were tested using in-situ data from the Emma storm impacts on a reflective beach (Praia de Faro, in S. Portugal). The model results compare well with measured post-storm and recovered profiles, showing high model skill under both erosive and constructive regimes. Building from this event-scale analysis, a gradual increase of temporal windows in simulated forcing conditions, through wave schematisation, is presented and discussed in terms of optimisation between gains in simulation time and losses in geomorphic change information. This methodological approach and findings are the basis that will allow passing on to dependable, long-term simulations of the beach-dune system evolution.

 

Acknowledgements: The work was implemented in the framework of the ENLACE project (ref. 28949 FEDER), funded by FCT (Fundação para a Ciência e a Tecnologia)
Global comparison between ocean ambient noise modelling and infrasound network observations
Authors: De Carlo Marine , Ardhuin Fabrice , Ceranna Lars , Hupe Patrick , Le Pichon Alexis , Vergoz Julien
Published: March 2020

The International Monitoring System (IMS) of the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) may be used to detect atmospheric explosions and events of interest using infrasound technology. However, ambient noise may affect the detection performance of the station network, and particularly ocean noise known as microbarom, as previously shown by characterizing ambient noise through broadband array processing on IMS data. Indeed, ocean wave interactions generate acoustic noise almost continuously. In this study, we use wave action models and include bathymetry and source directivity effects to model the microbarom sources and perform a global comparison between the synthetic signals obtained from two-dimensional spectrum ocean wave products, and observations. With this study, it is expected to enhance the characterization of the ocean-atmosphere coupling and to discriminate the impact of different features to account for in models. In return, better knowledge of microbarom sources allows to better characterize explosive atmospheric events and to provide information about the middle atmosphere dynamics and disturbances that could be used as model constraints
Characterization of dust aerosol over United Arab Emirates
Authors: Komppula Mika , Filioglou Maria , Shang Xiaoxia , Giannakaki Eleni , Hirsikko Anne , Romakkaniemi Sami
Published: March 2020

One-year of ground-based Raman lidar observations have been conducted in order to characterize the aerosol properties over United Arab Emirates (UAE). In total, over 1000 aerosol layers were detected during the one-year campaign period which was carried between March 2018 and February 2019. We found that the measurement site is a receptor of frequent dust events but predominantly the dust is mixed with anthropogenic and/or aerosol of marine origin. With our multiwavelength PollyXT Raman lidar we are able to retrieve the backscatter coefficients (at 355, 532 and 1064 nm), extinction coefficients (at 387 and 607nm), particle depolarization ratios (at 355 and 532 nm), water vapour concentration (at 407 nm), and further on lidar ratios and Ångström exponents to characterize the aerosols properties in detail. In general, the average lidar ratios and linear particle depolarization ratios already showed strong presence of dust aerosols. Since the region is both a source and a receptor of mineral dust, we have also explored the pure mineral dust properties in the region. The findings suggest that the mineral dust properties over the Middle East and western Asia, including the observation site, are comparable to those of the African mineral dust regarding the particle depolarization ratios but not the lidar ratios. The lower lidar ratio values are attributed to different geochemical characteristics of the under-study region compared to soil originating from Northern Africa.
Subglacial Drainage Routes of the Last Scandinavian Ice Sheet
Authors: Dewald Nico , Clark Chris D. , Livingstone Stephen J. , Ely Jeremy C. , Hughes Anna L.C.
Published: March 2020

The configuration of subglacial drainage systems has a major impact on the dynamics of ice sheets. However, the logistical challenges of measuring subglacial processes beneath contemporary ice sheets hinder our understanding about the spatio-temporal evolution of subglacial drainage systems. Furthermore, today’s observations on contemporary ice sheets are inherently limited to a short period within the process of deglaciation. Landforms generated by the flow of meltwater at the ice-bed interface offer the potential to study both large-scale (103-106 km2) and long-term (103-105 a) developments of subglacial drainage networks beneath past ice sheets. Despite collectively recording subglacial drainage, individual meltwater landform types such as eskers, meltwater channels and tunnel valleys, and hummock corridors have mostly been considered as separate entities. Using high-resolution (1-2 m) DEMs, we summarise the suite of interconnected subglacial meltwater landforms into a common drainage signature herein called a subglacial drainage route. Our integrated map of subglacial meltwater landforms presents the large-scale distribution of major subglacial drainage routes across Scandinavia and provides a basis for future research about the long-term evolution of subglacial drainage networks and its effect on ice dynamics of the Scandinavian Ice Sheet.
Efficiency Of Integrated Seismic Methods Approach To Near-Surface Characterization
Authors: Gjorgjeska Irena , Sheshov Vlatko , Edip Kemal , Dojchinovski Dragi
Published: March 2020

Surface seismic methods are among the most popular, widely accepted, geophysical methods for near-surface characterization. The most practical and effective way to perform in-situ measurements and data processing using different seismic methods as are seismic refraction, seismic reflection and MASW method in an integrated approach is presented in this paper. Each method has some advantages and limitations, but their application in an integrated approach provides higher accuracy in subsurface modeling. The same seismic equipment and, in most of the cases, the same acquisition parameters were used, enabling time and cost effective survey for subsurface characterization. The choice of these parameters was not random. Experimental research by use of the above-mentioned seismic methods was carried out in a long period in order to define the optimal parameters for successful application of an integrated technique in future research. During this survey, particular attention was paid to the influence of the acquisition parameters on the dispersion image resolution in the MASW surveys and extraction of an effective dispersion curve.

The results of the performed surveys at characteristic locations in R. North Macedonia are presented to show the efficiency of the combined methods approach.
Topographically trapped waves along the continental slope north of Svalbard
Authors: Kalhagen Kjersti , Nilsen Frank , Skogseth Ragnheid , Fer Ilker , Koenig Zoé , Kolås Eivind
Published: March 2020

On the continental slope north of Svalbard, Atlantic Water is transported eastward as a part of the Arctic Circumpolar Boundary Current. As inflow of Atlantic Water through the Fram Strait is the largest oceanic heat source to the Arctic Ocean, it is important to improve our knowledge about the dynamics and processes that govern the heat exchange between Atlantic Water and water masses of Arctic origin. This includes processes that enable lateral exchange across the shelf break or into the interior of the deep basin. Here, we study the vorticity dynamics on the slope and its contribution to the water mass modifications and heat exchange. Focusing on topographically trapped waves – sub-inertial oscillations trapped to follow the continental slope – we establish their existence and properties on the northern slope of Svalbard using a free baroclinic wave model. Their dependence on background stratification and current properties is explored in sensitivity analysis. Next, we discuss their contribution to lateral exchange from the boundary current on the slope to the continental shelf, troughs, and the deep Nansen Basin in the Arctic Ocean, including exchange associated with instabilities and resulting eddy shedding off the vorticity waves. Hydrographic and current time series from 2018-19 at two mooring arrays crossing the slope north of Svalbard (The Nansen Legacy project) are used to associate the observed physical environment with model-predicted topographic waves. Analysis of the in-situ data will determine which wave mode that can exist over the sloping seafloor and the observed hydrography and flow, and the model will give the corresponding spatial characteristics for the given frequencies and wave numbers. Energetic oscillations present in the observations are analyzed in light of the model results. Of special interest are the seasonal variability in hydrography and current strength and the resulting modification of the wave characteristics. Moreover, the interaction between the vorticity waves and tidal oscillations in the diurnal band is emphasized.
Seasonal melting simulation of permafrost rock glaciers and their potential contribution to sediment loads in Alpine catchments
Authors: Reid Lucas , Scherer Ulrike , Zehe Erwin
Published: March 2020

A common issue with large scale erosion modelling is that local processes are often unaccounted for, either because they haven’t been included in the model conceptually, or because they are undetected yet. On the other hand, significant deviations from such a general soil erosion model to the measurements can reveal those local processes. We compared the average yearly sediment amounts of a network of turbidity measurement stations in the catchment of the alpine River Inn to the results of the large scale erosion model RUSLE2015 (Panagos et. al.) for long term yearly erosion amounts and found a significant underestimation of sediment loads in three sub catchments. An important source of sediments in alpine rivers comes from glaciers, which explains the high loads in one of the stations, but two of the three high sediment load sub catchments are too low to have substantial valley glaciers. But another potential source of glacial sediment exists in the form of permafrost soils and in this case a specific permafrost form: rock glaciers. Rock glaciers in particular have been spotted in those two high sediment load catchments, but since they are hard to detect from remote sensing due to the surface being covered with rocks, the existence or the exact spatial extent is often unknown. But with rising temperatures in the Alps, the areas in which permafrost rock glaciers can exist decreases every year and the depth of the seasonal melting layer increases.

We propose the hypothesis that the high sediment loads in those sub catchments are caused by increasingly deeper melting of permafrost rock glaciers. This process releases fine materials which have been trapped frozen since the glacial period and are now being eroded and transported to the alpine streams. To get an estimation of potential erodible material from rock glacier melting in the respective sub catchments, we developed a model to simulate the heat diffusion from the air into the frozen ground, while accommodating for the change in specific thermal capacity. The model (developed in Python) takes air temperature time series data as input and can be configured for varying ground stratification setups with different thermal diffusivity values depending on the ground properties.

From the simulated melting depth of an average square meter of rock glacier we extrapolate the mass of melted material to the potential permafrost erosion material available in the River Inn sub catchments. We show that this source of sediments can be significant and needs to be factored in should an erosion model be used to calculate sediment input into the rivers. But, with the estimation of sediment load from permafrost origins narrowed down, improving a large-scale erosion model like the RUSLE2015 for this alpine mountain region by accounting for local processes like this one is possible. 
A global ensemble-based comparison of the last two glacial inceptions with LCice 2.0
Authors: Geng Marilena , Tarasov Lev , Bahadory Taimaz
Published: March 2020

What determines the character of glacial inceptions? Does the spatio-temporal pattern of ice nucleation and expansion vary much between Late Pleistocene glacial inceptions? According to various benthic del18O stacks, the MIS 7 interglacial was the most anomalous in character of the last 4 interglacials. Key differences include a weaker interglacial state and an initial fast inception interrupted by a return to a similar and extended interglacial state. These anomalies of MIS 7 along with temporal proximity arguably make the last two glacial inceptions the best test case for addressing our opening questions. As part of a larger project to generate and analyze a data-constrained ensemble of fully coupled ice/climate transient simulations for the last two complete glacial cycles, herein we present initial results comparing the last two glacial inceptions (MIS 7 and 5d). We are using a new version of the fully coupled ice/climate model LCice. LCice now simulates all 4 paleo ice sheet complexes with hybrid shallow-shelf and shallow-ice physics. It has already been shown to capture northern hemispheric ice sheet growth and subsequent retreat consistent with inferences from global mean sea level proxies (Bahadory et al, 2019). Orbital and greenhouse gas changes are the only external forcings applied to the model. A 300 member ensemble probes parametric uncertainties in both the 3D Glacial Systems Model and LoveClim (Atmosphere/Ocean/Vegetation) components of LCice. Our presentation will compare the evolution and relative phasing of all 4 paleo ice sheets, and associated changes in the rest of the modelled climate system.
Are in-stream transport and hyporheic exchange parameters identifiable from tracer test data?
Authors: Bottacin-Busolin Andrea
Published: March 2020

Inverse modeling approaches based on tracer data are often used to characterize transport processes in streams and rivers. This generally involves the calibration of a one-dimensional transport model using concentrations measured in the surface water at one or multiple locations along a stream reach. A major concern is whether the calibrated model parameters are representative of the physical transport processes occurring in the water column and the underlying sediment bed. This study looks at the identifiability of the parameters of a physically based one-dimensional stream transport model that represents hyporheic exchange as a vertically attenuated mixing process in accordance with recent experimental evidence. It is shown that, if the average flow velocity and hydraulic radius are not predetermined, there are infinite sets of parameter values that generate the same space-time concentration distributions in the water column. The result implies that in-stream transport and hyporheic exchange parameters cannot be determined from sole measurements of solute breakthrough curves in the surface water unless stream discharge and average cross-sectional geometry can be independently estimated.
Analysis of canopy structural and functional properties of tropical forests in a fertilisation experiment by Sentinel-2 images
Authors: Maleki Maral , Verryckt Lore , Barrios Jose Miguel , Peñuelas Josep , Janssens Ivan , Balzarolo Manuela
Published: March 2020

Tropical forests such as Amazon is repository of ecological services. Understanding how tropical forest responds to the climate helps to improve ecosystem modeling and declining the uncertainty in calculation of carbon balance. Nowadays, the availability of very high resolution satellite imagery such as Sentinel-2 are powerful tools for analyzing the canopy structural and functional shifts over time, especially for tropical forest.

In this study, we examined the effect of the nutrient availability (nitrogen (N) and phosphorus (P)) on canopy and structural properties in tropical forest of French Guiana. In situ observations of canopy structure and functioning (i.e. photosynthesis, leaf N, chlorophyll content) were collected at two experimental sites (Paracou and Nouragues). Three topographical positions in each site were considered (top of the hills, middle and bottom end of the slope) and four plots were manipulated with different level of fertilization (Control, N, P, NP) in September 2016. Statistical analysis were conducted to analyze how the fertilization affect the forest canopy seasonality and if differences between sites and across positions existed. Furthermore, we tested whether Sentinel-2 data could help or not to describe the canopy changes observed in the field. Therefore, all Sentinel-2 images available before the start of the experiment, which date represent the natural situation, and two years after the intensive and repeated fertilization were collected. Greenness, chlorophyll and N, P related indicators were calculated from Sentinel-2 images.

Key words: Sentinel-2, Tropical forest, soil fertilization, topographical position.
Influence of soil texture and degree of saturation on the equilibration time of water isotope in closed systems using direct H2O(liquid) - H2O(vapour) equilibration method
Authors: Vadibeler Devakunjari , Stockinger Michael , Wassenaar Leonard I. , Stumpp Christine
Published: March 2020

The direct liquid-vapour equilibration (DLVE) method is a new method to measure the stable isotopes of oxygen and hydrogen in soil pore water. Advantages of DLVE are (a) minimum sample handling, (b) direct isotope measurement from the samples without the need of extracting the water, (c) comparatively low costs, (d) and high reliability. However, the impact of different water content and equilibration times on the isotope measurement of different soil types is not well understood yet. Therefore, this study focuses on advancing our knowledge of the effect of different soil types and soil water contents on the isotope measurement of the DLVE method. Three different types of soil (sand, silt and clay) representing sediment samples with different pore sizes were saturated using tap water with a known isotopic value in a water bath. Different degrees of saturation (100%, 80%, 60% and 40%) were established, placed in Ziploc bags and equilibrated for different time spans ranging from 1 hour up to 8 days at constant surrounding temperature (about 20oC). The isotope measurements were obtained using cavity ring down laser spectroscopy (CDRS) for each test samples. The time taken for the H2O(liquid)-H2O(vapour) equilibration for different soil textures and different water contents in Ziploc bags were determined. Results showed that sandy soil samples took shorter time to reach isotopic equilibrium with the headspace in the Ziploc bags compared to clayey soil which took comparatively longer for the same soil saturation level. Regardless of the soil type, 100% saturated soil samples took shorter time to reach liquid-water equilibration compared to low saturated soil samples. These findings could lead to protocols of soil sample measurements using DLVE regarding the influence of different soil textures and soil moisture contents.
Objective deviation of Climate Indices for the assessment of altered risk-landscapes driven by accelerated climate change
Authors: Madjdi Nikta , Enigl Katharina , Matulla Christoph
Published: March 2020

Floodings are amongst the most devastating damage-processes worldwide. Along with the increase in climate change induced extreme events, research devoted to the identification of so-called Climate Indices (CIs) describing weather phenomena triggering hazard-occurrences gains rising emphasis. CIs have a wide potential for further investigation in both research and application as e.g. in public protection and the transport and logistic industry. The appearance of specific CIs in regional climate models (i.e., ‘hazard development corridors’) can serve as an input in decision-theoretic concepts aiming to sustain current safety levels in climate change induced altering risk landscapes (Matulla et al, submitted). Enigl et al, 2019 first objectively derived hazard-triggering precipitation totals for six process-categories and three climatologically as well as geomorphologically distinct regions in the Austrian part of the European Alps.  This study aims at investigating a slightly different methodological approach for the objective determination of Climate Indices in the catchment area of the River Danube in Austria depending on catchment areas.
Episodic fluid pressure cycling controls the interplay between Slow Slip Events and Large Megathrust Earthquakes
Authors: Petrini Claudio , Dal Zilio Luca , Gerya Taras
Published: March 2020

Slow slip events (SSEs) are part of a spectrum of aseismic processes that relieve tectonic stress on faults. Their occurrence in subduction zones have been suggested to trigger megathrust earthquakes due to perturbations in fluid pressure. However, examples to date have been poorly recorded and physical observations of temporal fluid pressure fluctuations through slow slip cycles remain elusive. Here, we use a newly developed two-phase flow numerical model — which couples solid rock deformation and pervasive fluid flow — to show how crustal stresses and fluid pressures within subducting megathrust evolve before and during slow slip and regular events. This unified 2D numerical framework couples inertial mechanical deformation and fluid flow by using finite difference methods, marker-in-cell technique, and poro-visco-elasto-plastic rheologies. Furthermore, an adaptive time stepping allows the correct resolution of both long- and short-time scales, ranging from years to milliseconds during the dynamic propagation of earthquake rupture.

Here we show how permeability and its spatial distribution control the degree of locking along the megathrust interface and the interplay between seismic and aseismic slip. While a constant permeability leads to more regular seismic cycles, a depth dependent permeability contributes substantially to the development of two distinct megathrust zones: a shallow, locked seismogenic zone and a deep, narrow aseismic segment characterized by SSEs. Furthermore, we show that without requiring any specific friction law, our model shows that permeability, episodic stress transfer and fluid pressure cycling control the predominant slip mode along the subduction megathrust. Specifically, we find that the up-dip propagation of episodic SSEs systematically decreases the fault strength due to a continuous accumulation and release of fluid pressure within overpressured subducting interface, thus affecting the timing of large megathrust earthquakes. These results contribute to improve our understanding of the physical driving forces underlying the interplay between seismic and aseismic slip, and demonstrate that slow slip events may prove useful for short-term earthquake forecasts.
Which role do preferential flowpaths and fractures play in the subsurface reactivity in heterogeneous aquifers?
Authors: Bouchez Camille , Lavenant Nicolas , Farasin Julien , Labasque Thierry , Osorio Ivan , Bouchez Julien , Gomez Francesco , Longuevergne Laurent , Le Borgne Tanguy
Published: March 2020

The underground fracture pattern, which results from tectonic, climatic and biological stresses, drives water storage dynamic and nutrient cycling in the deep critical zone. Despite a gradual decrease of fracture density with depth, the fracture network is strongly heterogeneous and anisotropic, resulting in a complex pathway distribution with variable hydraulic conductivities. High celerities occurring in preferential flowpaths govern the dynamic response of discharge flows to extreme recharge events. However, the role of preferential flowpaths in transporting fresh meteoritic water and biota remains poorly studied, while the delivery of meteoritic reactants is crucial to initiate underground chemical reactions.

Here, we study a fractured aquifer in a crystalline catchment located in Brittany (Guidel, France) to investigate the link between depth, water transit time and subsurface reactivity in fractures. Oxygen is used as a tracer of fresh water inputs because its availability has a tremendous impact on oxidation-driven reactions such as weathering processes and microbial activity. We performed vertically sampling of fracture fluid with an inflatable packer capable of isolating fractures in an artesian well located in the discharge chemically-reduced zone of the aquifer. Major ions, dissolved reactive gases, dissolved anthropogenic gases, stable isotopes (O, Sr and Si) and microbial diversity were analysed on five fracture waters sampled at depth between 20 and 55 m. Significant differences have been observed between fractures and younger and more oxygenated waters were found intermittently in fractures at 47 and 54m, with dissolved oxygen concentrations ranging between 0.1 and 0.5 mg/L. The penetration of oxygen in deep fractures reveals either a rapid transport of oxygen or a low consumption of oxygen in preferential flowpaths. These hypotheses are tested with a Discrete Fracture Network model, where first-order reaction rates have been implemented, and the temporal dynamic of oxygen is assessed and linked to water transit time in fractures. We investigate the concept of transit time and water-rock contact time and discuss the relevance of mean transit time to evaluate subsurface reactivity.

Preferential flowpaths thus not only make fractured aquifers more dynamic but can also, under extreme recharge conditions, efficiently transport fresh water at high depth. The advective-dominant transport of oxygen through artery-like fractures could have a significant impact on short term microbial activity and the associated nutrient cycling but also on long term weathering front propagation.
Using sediment morphometry to infer transport dynamics in Alpine catchments: which variables matter?
Authors: Cattapan Alessandro , Paron Paolo , McClain Michael , Piégay Hervé , Franca Mário
Published: March 2020

Decisions on water resources infrastructures’ planning and management are, at the moment, only rarely taking into consideration their impacts on sediment transport dynamics and on river geomorphological changes at basin scale. The reasons for this are the fact that these changes in most cases happen over time scales longer than the so called “engineering scale” (around 70/100 years) and the inherent complexity in accurately modelling these processes at the scales of interest. Recently, simplified schematizations have been proposed to assess different scenarios for river basin development strategies (e.g. dams development and operations). The possibility to calibrate and validate these models still is hindered by the scarcity of measurements of sediment fluxes in most catchments worldwide. If one could accurately infer transport processes (fluxes) (e.g. travel distances, source areas, relative production etc.) from sediment properties (shape, size, lithology, etc.), this would allow the use of already available data and would simplify the collection of future datasets.

Recent studies on sediment attrition claim the existence of a “universal” relation between particles relative mass loss and their circularity (Novák-Szabó et al., 2018). The relationship between relative mass-loss and travel distance is, however, still unclear and thought to depend on the transport conditions and on particles mechanical properties.

In order to start assessing the importance of the latter, we identified a case study, the Sarzana River basin, in North-East Italy, characterized by the presence of localized sources of arenites and metabasalts, which are expected to have different abrasion rates. We measured sediment size and shape properties with a photogrammetric method and compared their longitudinal evolution. We also performed the same analysis on mixed samples, collected using the Wolman method. The inclusion of particles lithology among the control variables of the study allowed the identification of a series of transport dynamics that would otherwise be completely overlooked by mixed sampling. This example stresses the importance for a thorough basin analysis when designing a sediment monitoring campaign in order to maximise the amount of information minable from data.