bluuebunny/crossref_metadata_2025 huggingface dataset:
Carbon dioxide fluxes on agricultural grasslands – Uncertainty associated with gap-filling
Authors: Vekuri Henriikka , Tuovinen Juha-Pekka , Korkiakoski Mika , Heimsch Laura , Kulmala Liisa , Rainne Juuso , Mäkelä Timo , Hatakka Juha , Liski Jari , Laurila Tuomas , Lohila Annalea
Published: March 2020

Mitigation of climate change requires – besides reductions in greenhouse gas emissions – actions to increase carbon sinks and storages in terrestrial ecosystems. Agricultural lands have a high potential for increased carbon sequestration through climate-smart land management and agricultural practices. However, in order to make climate-smart farming an accredited solution for climate policy, carbon markets and product footprints, reliable verification of carbon sequestration is needed. Direct measurement of the changes in soil carbon stock is slow, laborious and expensive and has significant uncertainties due to large background stocks and high spatial variability. An alternative is to infer the soil carbon stock change from measurements of the gaseous carbon fluxes between ecosystems and the atmosphere using the micrometeorological eddy covariance (EC) method.

Eddy covariance measures net ecosystem exchange (NEE), which is a small difference between two large components: carbon uptake by photosynthesis and losses due to plant and soil respiration. Therefore, small changes in either of them results in a large change in NEE. This sensitivity is also reflected in uncertainty estimates, which are critical for defining confidence intervals for annual carbon budget estimates and for making statistically valid comparisons of different management practices.  In addition, there are inevitable gaps in the data due to instrument failure, power shortages and non-ideal flow conditions. Therefore, in order to calculate daily and annual sums, the collected data must be temporally upscaled or gap-filled, which constitutes a major additional source of uncertainty. This study compares two different gap-filling methods for CO₂ fluxes: (1) an artificial neural network and (2) non-linear regression, which uses temperature and radiation as drivers. Uncertainties associated with both methods are estimated and discussed. The analysis is based on EC flux measurements conducted at two agricultural grassland sites in Finland.
Increased ice flow in the Getz region of West Antarctica, from 1994 to 2018
Authors: Selley Heather , Hogg Anna , Cornford Stephen , Shepherd Andrew , Dutrieux Pierre , Wuite Jan , Kusk Anders , Nagler Thomas , Gilbert Lin
Published: March 2020

The Getz region is a marine-terminating sector of West Antarctica, characterised by a ~650 km long ice shelf that buttresses the inland ice sheet. The majority of the Getz drainage basin is grounded well below sea level, and while the ice shelf has thinned, its calving front has remained relatively stable since the early ’90s. Satellite observations have shown strong thinning of both the ice sheet and ice shelf over the past 25-years, and mass balance studies have shown that the sector is negatively imbalanced (−16.4 ± 4.0 Gt/year). In this study, we use satellite data to measure ice speed in the Getz region, over a 25-year period from 1994 to 2019. We use Synthetic Aperture Radar (SAR) data from historical missions including ERS-1, 2 and ALOS PALSAR, in combination with newer data from the Sentinel-1a & b satellite constellation, to generate annual velocity maps. The Sentinel-1 data extend the historical velocity record and provides a new high temporal resolution record, 6-day averaged solutions, of velocity change since 2017. We used satellite observations in combination with the BISICLES ice sheet model to fill gaps in the observational record, and to measure ice discharge and from the region. We find there are 14 distinct flow units that drain the Getz coastline, with average speeds ranging from 153 ± 7 to 1053 ± 194 m/yr around the grounding line. Our results show that all of these flow units have sped up during the study period, since 1994. At the grounding line, we measure an average speed increase of ~5 m/yr2, with some flow units accelerating by over 11 m/yr2. We find that the spatial pattern of change in ice speed is consistent with the regions of strongest surface lowering, which on some flow units occurs at rates of up to -2.4 m/yr. Our observations show that ice speedup is greatest where the ice is thickest (>700 m), and grounded most deeply. This long 25-year record of change also shows that on some ice streams, the rate of change in ice speed has not been constant throughout the study period. In some regions where ocean temperature measurements are also available, we find that increases in ice speed coincide with the periodic presence of circumpolar deep water, which may therefore be responsible for driving this change. In summary, this study provides a new record of change in ice speed for a rapidly evolving region of Antarctica. In the future, it will be important to use both ocean models and observations to improve our understanding of how ocean forcing is driving dynamic imbalance in the region. This will improve our understanding of the physical mechanisms driving change in Antarctica, helping us to better constrain the ice sheets future contribution to global sea level rise.
On the characterisation of open-flow seeding conditions for image-velocimetry techniques using UASs
Authors: Dal Sasso Silvano Fortunato , Pizarro Alonso , Manfreda Salvatore
Published: March 2020

In the last years, new technologies have been developed to monitor rivers in a real-time framework opening new opportunities and challenges for the research community and practitioners. Acquiring data in open flow conditions can be performed through the use of Unmanned Aerial System (UAS) to derive surface velocity fields and in consequence, river discharge. Significant work has been done to investigate the reliability of image-velocimetry techniques using numerical simulations and laboratory flume experiments, but, to date, the effects of environmental factors on velocity estimates are not addressed adequately. In this context, a critical variable is represented by the number of particles transiting on the water surface (defined as seeding density) during field surveys and their challenging dynamics along the cross-section, on both time and space. Seeding density has a significant effect on surface velocity estimation and river discharge accuracy. The goal of this study was, therefore, to evaluate the accuracy and feasibility of LSPIV and PTV techniques under different seeding and flow conditions using several footages acquired employing UASs. To this purpose, the seeding behaviour during the whole acquisition time was examined for each case study focusing on the quantification of essential variables such as seeding density, average tracers’ dimension, coefficient of variation of tracers’ area, and spatial dispersion of them in the field of view. For each case study, both image-velocimetry techniques have been applied considering several different sets of images to locally measure the accuracy of velocity estimations in challenging seeding conditions. Results show that the local seeding density, tracers’ dimension and their spatial distribution can strongly influence the reconstruction of velocity fields in natural stream reaches. Therefore, prior knowledge of seeding characteristics in the field can deal with the choice of the optimal image-velocimetry technique to use and the related setting parameters.
A new automated radiolarian image acquisition, processing and identification workflow
Authors: Tetard Martin , Marchant Ross , Gally Yves , de Garidel-Thoron Thibault , Beaufort Luc
Published: March 2020

Identification of microfossils is usually done by taxonomist experts and requires significant systematic knowledge and time, as about 300 specimens per sample are commonly identified for statistically reliable studies. Radiolaria are no exception, and their utility has been demonstrated for a long time in biostratigraphy using the presence / absence of some species, as well in palaeoceanographic reconstructions (past productivity, temperature, and water masses variability). Traditionally, these studies have required the manual identification of numerous species in a lot of samples under a transmitted light microscope, which is very time consuming. Furthermore, identification may differ between operators, biasing reproducibility. Recent technological advances in image acquisition, processing, and recognition now enable automated procedures for this process, from microscopic slide field-of-view acquisition to taxonomic identification.

 

A new workflow was developed for radiolarian acquisition, processing and identification. Firstly, a new protocol was developed as a proposed standard methodology for preparing radiolarian microscopic slides. We mount 8 samples per slide (using 12x12 mm cover slides) on which radiolarians were randomly and uniformly decanted using a new 3D-printed decanter that minimizes the loss of material. The slides are then automatically imaged using an automated transmitted light microscope. About 500 individual radiolarian specimens (excluding the broken and overlaying specimens) are recovered (about 4000 specimens per slide) from 3375 original fields of view (15 images z-stacked per FOV x 225 FOVs) per sample, after which automated image processing and segmentation is performed using a custom plugin developed for the ImageJ software. Each image is then classified using a convolutional neural network (CNN) trained on a database of radiolarian images.

 

To create the CNN classification stage, a dedicated software program, ParticleTrieur, was used to annotate a large dataset of radiolarian taxa (currently more than 27488 images, corresponding to 101 classes, from Neogene to recent). This software enables the visualisation and assignation of radiolarian pictures to defined taxa by progressively learning and suggesting taxa labels based on previous labelling. This database was then used to train a CNN (convolutional neural network) for the automated taxonomical identification stage. After fusing classes containing less than 10 images into a single “other” class, 69 classes were trained to be recognised with an overall accuracy of 93 %. This new workflow will now be used on a Miocene to Recent sedimentary record from the IODP expedition 363 (Core U1488A), recovered in the West Pacific Warm Pool.
Monitoring diseases by using Hyperspectral and Thermal techniques at two different spatial scales: A feasibility study in alpine regions
Authors: Mejia-Aguilar Abraham , Prechsl Ulrich , Monsorno Roberto
Published: March 2020

 

Since some decades, cultural and traditional alpine farming have been changed enormously, mainly due to anthropogenic activities and economic factors: some pastures were abandoned, some others changed from farming to touristic areas (eg. ski resorts) and some others have been dramatically intensified by changing to monoculture. In consequence, these activities allow practices of deforestation, the massive use of fertilizers and pesticides, the excessive use of machinery, grading, drainage among others. Additionally, human activity have impacted on weather by resulting on low rainfall or drought extended periods. The combination of these factors result that vegetation and species are more vulnerable to the infestation of pests and diseases.

On this feasibility study, we propose the identification, mapping and classification of individual trees affected by fungal species (alternaria) in apple orchards located in South Tyrol, Italy, based on hyperspectral and thermal imagery. We have conducted terrestrial and UAV-based surveys to identify (un)healthy indivuals (trees). High spatial resolution scale consisted on terrestrial monitoring approaches based on the identification of trees and leaves, the collection of leave spectral signature based on a dedicated spectroradiometer (300 to 2000 nm) and spectral imagery of individuals. Medium spatial resolution consisted on UAV-based spectral data collection and interpretation. 30 hyperspectral bands (400 to 900 nm) in the VIR range and thermal imagery (14 µm) in combination with leave-spectral bands allowed the identification and mapping of un-healthy individuals for further treatment.
Towards the first Scots pine chronosequence studies in Poland
Authors: Olejnik Janusz , Ziemblinska Klaudia , Urbaniak Marek , Malek Stanislaw
Published: March 2020

Since January 2008 the first eddy covariance (EC) ecosystem station in Polish forests was set up in a 54-year-old homogenous Scots pine stand near Tuczno (north-western part of the country).  Almost 40-m tall steal scaffold tower ensures obtaining CO2 and H2O fluxes from the area extending to 500 m in the prevailing wind direction most of the time. Until now measurements carried out in Tuczno forest are the only direct, real-time and long-term studies of this type in the Poland. In comparison with other European pine forests, investigated using the same technique, this site is very productive, annually sequestering about 16 t of CO2 per hectare. There were many other comprehensive studies done nearby the main EC tower, which were the part of the common project founded by the State Forests since the very beginning e.g.: dendrometry and typical forest biometrics, hydrological and soil investigations, etc.

The results of EC measurements of CO2 fluxes from Tuczno site together with data from two others pine forest sites: Tlen I (5-year-old forest, 6 years of data) and Mezyk (25-year-old forest, 2 years of data) allowed to create the cumulative NEP over the chronosequence. This is the first chronosequence curve for one tree species in this part of Europe. Since the climate and soil conditions at all three sites are very similar (there is no significant statistical difference), the current research at all site will be continued until 2025 and we do expect a full chronosequence curve very soon. These results were also compared with models (mainly CBM) and we would like to extend our results to the whole territory of Poland where it is a dominant species (about 60% of total forest area is covered by Pinus Silvestris).
A data fusion method to improve winter PM10 concentration predictions in Budapest based on the CAMS air quality models
Authors: Varga-Balogh Adrienn , Leelőssy Ádám , Lagzi István , Mészáros Róbert
Published: March 2020

Winter air pollution in Budapest is a major environmental issue, caused by an interaction of residential heating, urban traffic and large-scale transport. Increasing public and political demand are present to achieve more accurate air quality predictions to support both real-time public health measures and long-term mitigation policies.  Atmospheric chemistry and transport models of the Copernicus Atmospheric Monitoring Service (CAMS) provide near-real-time air quality forecasts for Europe. The validation of these model predictions for Budapest showed that although large-scale processes are well captured, the complex interaction of large-scale plumes with significant and highly variable local residential emissions leads to the underestimation of winter PM10 concentrations. Furthermore, CAMS models are not expected to fully predict the non-representative concentrations at specific urban monitoring locations, which, on the other hand, serve as the legal basis of all public policies and measures. Therefore, obtaining a relationship between monitoring site observations and CAMS model predictions is of primary importance. 

In this study, we used observed PM10 concentration data from 12 air quality monitoring sites within Budapest, as well as 24-hour predictions from 7 of the 9 CAMS models to produce an optimal linear combination of models that best matched, in terms of RMSE, the observed time series. A zero-degree term to correct the model bias was also applied. The applied data fusion method was cross-validated on urban monitoring sites not used in fitting the model, and found to improve PM10 forecast validation statistics compared to the pointwise model median (CAMS ensemble) as well as each of the 7 single models. The presented fusion of CAMS models can therefore provide an improved prediction of PM10 concentrations at urban monitoring sites in Budapest.  
Towards field data applications of six-component polarization analysis
Authors: Sollberger David , Igel Heiner , Schmelzbach Cedric , Bernauer Felix , Yuan Shihao , Wassermann Joachim , Gebauer André , Schreiber Ulrich , Robertsson Johan
Published: March 2020

The analysis of the relative amplitudes of a passing seismic wave recorded on a single seismometer measuring six degrees of freedom of ground motion (translation and rotation) theoretically allows one to extract information on the wave that can conventionally only be obtained from receiver arrays. In the past, it has been shown on numerical data that the extension of conventional three-component (3C) polarization analysis techniques to six-components, allows one to unambiguously identify the wave type of a passing wave and characterise it in terms of its propagation direction (without the 180° ambiguity inherent in 3C data) and local wave speed. Additionally, due to the increase in the dimensionality of the data, two waves arriving at a station at the same time can be simultaneously characterised under ideal conditions (low noise).

Attempts to apply such 6-C polarization analysis techniques to field data have so far been met with limited success. Varying noise levels on the individual components and complex wavefields (with more than two interfering waves arriving at the station at the same time) usually prevent the stable recovery of wave parameters using single-station 6-C polarization analysis.

Here we discuss first attempts to overcome these issues. We (1) test the robustness of different wave parameter estimators (maximum likelihood, MUSIC) towards high levels of noise and (2) we try to reduce the number of interfering events in the analysis window by performing 6-C polarization analysis on time-frequency decomposed seismograms (i.e. spectrograms) using the S-transform.

The new techniques are extensively tested on field data recorded on the high-performance ROMY ringlaser.
How well do the latest Earth System Models capture the behaviour of biogenic secondary organic aerosol in the atmosphere?
Authors: Scott Catherine , Yoshioka Masaru , Dearden Chris , Carslaw Ken , Spracklen Dominick , O'Connor Fiona , Folberth Gerd , Dalvi Mohit , Mulcahy Jane , Balkanski Yves , Checa-Garcia Ramiro , Olivie Dirk , Schulz Michael , van Noije Twan , le Sager Philippe , Michou Martine , Nabat Pierre , Nieradzik Lars , Bergman Tommi , O'Donnell Declan
Published: March 2020

Biogenic secondary organic aerosol (SOA) is formed as a result of the atmospheric oxidation of gas-phase biogenic volatile organic compounds (BVOCs). Here, we evaluate the ability of five European Earth System Models (CNRM-ESM2-1, EC-Earth3, IPSL-CM6, NorESM1.2, UKESM1) to capture the amount, and behaviour, of biogenic SOA in the atmosphere.

The ESMs cover a range of complexity in terms of their representation of the sources and processing of biogenic SOA (i.e., from a fixed climatology of SOA amount to an interactive BVOC emission scheme followed by atmospheric processing).

We combine station measurements of BVOC emission and atmospheric BVOC concentrations with remotely sensed isoprene emission estimates to evaluate the models’ representation of the sources of biogenic SOA. We use organic aerosol mass and particle number concentration measurements from a number of forested sites to evaluate the ability of the models to capture the seasonal cycle in the amount of biogenic SOA present, as well as its impact on the aerosol size distribution. Whilst the models appear to capture the seasonal cycle in organic aerosol well for a boreal forest site, the ESMs consistently over-predict the amount of organic aerosol present at a tropical forest location. 

Finally, we explore the ability of these models to capture the observed relationships between organic aerosol mass, or particle number, and temperature. We find that the ESMs equipped with vegetation models that generate BVOC emissions interactively are able to capture well the strength of the observed relationship between temperature and organic aerosol mass. This lends confidence to the ability of these ESMs to accurately represent changes in atmospheric composition driven by climate.
Energy budget of laboratory earthquakes: a comparison between linear elastic fracture mechanics approach and experimental approach.
Authors: Violay Marie , Paglialunga Federica , Passelègue François X.
Published: March 2020

Earthquakes correspond to a sudden release of elastic energy stored during inter-seismic period by tectonic loading around fault. The earthquake energy budget consists of four non-independent terms: the energy release rate (by unit crack length), the fracture energy, the heat term and finally the radiated energy. These terms depend on the rupture and sliding velocities, the amount of slip and the stress drop. Because of the impossibility to access to stress and strain conditions at depth, the earthquake energy budget cannot be fully constrained from seismological data, limiting our understanding of its influence on rupture propagation.

To address this issue, we conducted stick-slip experiments with large samples in a biaxial configuration apparatus. By imposing constant normal load and increasing shear load, seismic events were produced on a 20 cm long fault, for which the energy budget was estimated using different methods.

Fracture energy was estimated by recording the strain field around the crack tip through high frequency (2 MHz) strain gage rosettes array and comparing it to the theoretical LEFM strain field predictions obtained for same conditions (i.e. rupture velocity, distance from the fault). Fracture energies were then inverted and found to range in between 1 and 10 J/m2. At the same time the energy partitioning was estimated through stress-slip evolution during rupture. The fracture energies obtained from this method are almost one order of magnitude larger than the ones inverted from LEFM and range in between 1 and 90 J/m2. Moreover, the energy partitioning shows the radiated energy ranging between 80 and 300 J/m2 and finally the heat/thermal energy as the largest fraction of the energy partitioning with values ranging from 200 to 2500 J/m2. Our preliminary results highlight the importance of understanding the contribution of heat energy in frictional processes, since this term cannot be estimated from seismological data.
Global Changes of Köppen-Trewartha Climate Zones Derived from RegCM CORDEX-CORE Simulations
Authors: Belda Michal , Halenka Tomáš
Published: March 2020

The analysis of climate patterns can be performed for each climatic variable separately or the data can be aggregated using e.g. a kind of climate classification. The advantage of such method, in our case Köppen-Trewartha classification, is putting together the most important variables, i.e. temperature and precipitation, considering not only annual means, but through monthly values the annual cycle as well. These classifications usually correspond to vegetation distribution in the sense that each climate type is dominated by one vegetation zone or eco-region. Climate classifications represent a convenient tool for the assessment and validation of climate models and for the analysis of simulated future climate changes.

 

The results of RegCM driven by selected CMIP5 simulations (mostly HadGEM, MPI and NorESM) produced within the CORDEX-CORE experiment over nine CORDEX domains are analysed. Validation based on ERA-Interim driven runs compared to CRU database (E-OBS for higher resolution in Europe) shows reasonable agreement in the Northern hemisphere with a tendency towards wetter and colder climate types in North America. Worse representation in Southern hemisphere is observed, mainly in Australia (lack of desert type). Through the analysis of the control experiments together with the performance of driving GCMs we can assess the sources of the biases in present conditions as well as the added value, which comes mainly from better representation of topography in higher resolution and thus appearance of mountaineous tundra type, as well as better representation of coastal regions and thus separating maritime subtypes. Finally, for two scenarios RCP8.5 and RCP2.6 we show the projections of the individual types‘ area changes, mainly decline of boreal and polar types, their shift to the higher latitudes and altitudes, increase of temperate, subtropical and dry climates. Magnitude, and in some cases (temperate climate) even the sign of change is largely dependent on the region and driving model.
Geophysical characterization of a Limestone Heterogeneous Vadose Zone – Beauce Aquifer (France)
Authors: Ammor Salma , Baltassat Jean Michel , Jodry Clara , Legtchenko Anatoly , Azaroual Mohammed , Amraoui Nadia , Isch Arnaud
Published: March 2020

 

In the Region Centre - Val de Loire, groundwater quality of the largest reservoir in France is menaced by strong pressures related to high agricultural activities. Scientific efforts are being made to well understand both hydrological systems and water transfers in the Vadose Zone (VZ). The O-ZNS observatory, currently under development at an agricultural site in Villamblain (Centre Val de Loire, France), will provide a detailed insight of hydrological transfer processes in the VZ. It is based on an exceptional well (20m-depth and 4m-diameter) associated with several surrounding boreholes. These will allow, an accurate characterization of the heterogeneous structure of the unsaturated limestone, by geophysical imaging and a monitoring of the hydrogeological parameters by various techniques. The aim is to understand the hydrogeological processes governing water transfer in heterogeneous limestone VZ, and to elaborate hydrogeological models integrating these processes.

Our approach for this first characterization of the O-ZNS site is mainly based on a qualitative comparison between surface and borehole geophysical prospections and laboratory tests. Geophysical prospection consisted especially in 2D Magnetic Resonance Sounding (MRS), which allows non-invasive determination of water content in the VZ. Several sizes of MRS loops were tested to explore scale effects and different measurement configuration were applied for filtering. MRS results are compared with laboratory tests (petrophysical, mineralogical and hydraulic properties) and the other geophysical prospection methods, such as neutron logging and cross-borehole radar tomography results.

These preliminary results are used in order to define MRS monitoring measurement configuration including loop size and position, as well as identify optimized filtering strategy and measurement time frequency. Finally, these results will provide the baseline for the research projects, which aims at determining MRS contribution to the improvement of taking into consideration scale variability and heterogeneity in water transfers models within the vadose zone.
Millimeter scale water movement on convex and concave surfaces of porous media under microgravity.
Authors: Maruo Yuichi , Sato Naoto , Naganuma Natsumi , Nogawa Kento , Tsukano Maho , Mizutani Hayato , Noborio Kosuke
Published: March 2020

 Human’s sphere of activities is going to expand to Moon and Mars on 2030s. As manned space mission getting longer, the importance of extra-terrestrial agricultural production increase not only for food production, but also for phycological benefit for astronauts. Water movement in porous media must be understood for secured plant growth, previous researches, however, reported that slower capillary flow was observed under microgravity than under Earth gravity (1 G). Air entrapment on pore neck may induce higher tortuosity and made capillary flow slower under microgravity. It was also reported that widening shape on capillary tube restrict water movement in capillary tube under microgravity. The diameter of capillary tube was relatively large (0.8 mm to 2.3 mm in-diameter) in the previous report; therefore, it is unclear that the result is applicable to the smaller pore structure like porous media. The objective of this study is (1) to evaluate capillary flow rate on convex and concave surface on the particle of porous media under microgravity and under 1 G, (2) to evaluate the water movement on widening area made by boundary between 0.8 mm and 1.0 mm glass beads. To make water movement visible, acrylic column of 2 mm thickness was chosen and was filled with 4 cm layer of 0.8 mm diameter glass beads and 3 cm layer of 1.0 mm diameter glass beads. Distilled water dyed with methylene blue solution was infiltrated into the glass beads under 2.4 s microgravity condition induced by 50 m free fall or under 1 G condition. Capillary flow was taken by high speed (960 fps) and closeup camera (DSC-RX100M5A, SONY) and split into image sequences to analyze with software (ImageJ). Both under microgravity and under 1 G, capillary flow stuck on the convex surface and hardly infiltrated into the concave surface, however, once water crossed over the convex surfaces, water moved on concave surfaces very fast. Pore was filled with water and air entrapment on pore neck, predicted on previous research, was not observed. The water front firstly reached on the boundary of 0.8 mm to 1.0 mm glass beads stopped, however, after the surrounding water front catch up, water crossed over the boundary. This result suggested that widening area restricted capillary flow, however it did not shut-off.
Stream Temperature Evolution in Switzerland: Recent past and future
Authors: Michel Adrien , Brauchli Tristan , Wever Nander , Schaefli Bettina , Lehning Michael , Huwald Hendrik
Published: March 2020

Climate change has already affected many components of our natural environment which are well described in the literature. Water temperature has received less interest despite the fact that it is recognized as key variable for assessing water quality of freshwater ecosystems in streams and lakes. It influences the metabolic activity of aquatic organisms but also biochemical cycles. Water temperature is also a key variable for many industrial sectors, e.g. as cooling water for electricity production or in large buildings, and for the spreading of some diseases affecting fishes.

It is very likely that climate change has and will also have an important effect on the temperature of streams. This study (Michel et al., 2020) investigates first the past temperature evolution and corresponding discharge in Switzerland since 1979, showing an increase of +0.33 ± 0.03° per decade in water temperature. Some differences between catchment type (alpine vs. lowland) and some important seasonal features are identified.

In a second step, the response of selected catchments in Switzerland to the future forcing is numerically assessed using the CH2018 climate change scenarios for Switzerland. The approach uses a sequence of physical models including Snowpack, Alpine3D and StreamFlow. The CH2018 scenarios have been down-scaled to hourly resolution using a novel approach based on a delta method which preserves the seasonal aspect of the climate change scenario. The results show an increase in temperature for any of the RCP (2.6, 4.5, and 8.5) and a strong impact of climate change on alpine catchments caused by changes in snowfall/melt and glacier melt. As a consequence, river ecosystems including fish populations will be severely impacted and current legal limits for the usage of water for cooling in the energy production sector and in the industry will be reached more often in the future.

REFERENCES

Michel, A., Brauchli, T., Lehning, M., Schaefli, B., & Huwald, H.: Stream temperature and discharge evolution in Switzerland over the last 50 years: annual and seasonal behaviour , Hydrol. Hydrol. Earth Syst. Sci., 24, 115–142, https://doi.org/10.5194/hess-24-115-2020, 2020.
Reservoir monitoring with controlled source electromagnetics - a case study from a producing oil field in NW Germany
Authors: Ritter Oliver , Patzer Cedric , Tietze Kristina
Published: March 2020

Injection of fluids (e.g. brines, CO2, steam) is commonly used in enhanced oil recovery (EOR) techniques to push crude oil in place towards the production wells. To optimize EOR procedures, it is essential to know the spatial propagation of injected fluids in the subsurface. Electromagnetic monitoring methods are particularly useful to decipher the spatio-temporal distribution of typically resistive oil versus typically conductive fluids.

We present an overview of soft- and hardware developments, modelling results, and time-lapse field data obtained over five years in an oilfield in NW Germany. CSEM modelling studies showed that conventional surface-based measurements alone do not provide sufficient resolution to changes within a thin (<15 m) reservoir structure located at ~1200 m depth. Combination with sources and/or receivers with vertical components increase sensitivity to such reservoirs very significantly. Based on these findings, a novel horizontal-vertical dipole source using the steel casing of a 1.3 km deep abandoned oil-well was successfully used for current injection in three time-lapse CSEM surveys (2014-2016) across the oilfield. We developed a novel numerical framework to compute the effect of metal casings on CSEM data and included it into our existing modelling and inversion (imaging) software. We also developed a receiver chain to measure the vertical electric field in a shallow observation borehole. Repeatability of the measured data – an essential prerequisite for any monitoring application – was excellent between the repeat surveys despite of high noise levels in an active oil field.

We also show results of a new numerical framework for 4D (time-lapse) CSEM inversion which allows direct imaging of changes within the 3D electrical conductivity structure of a reservoir. A cascaded inversion scheme in combination with a-priori information (conductivity constraints) and weighting of subdomains of the modelling space shows promising results in solving this mathematically ill-posed problem.

 
Processing steps for the compiling AAGRG gravity maps
Authors: Zahorec Pavol , Papčo Juraj , Pašteka Roman ,   AlpArray Gravity Research Group
Published: March 2020

First unified complete Bouguer anomaly map of AlpArray area compiled from terrestrial gravity data is in preparation. The following steps to calculate the first version of the map were performed: 1. unification of different spatial, height and gravity systems, 2. getting available detailed (mainly LiDAR-based) elevation models and their transformation from physical to ellipsoidal heights, 3. calculation of mass corrections (gravity effect of the topography between the surface and ellipsoid level) with density 2 670 kg/m3, 4. calculation of bathymetric corrections for water masses below the ellipsoid (correction density -1 640 kg/m3), 5. calculation of lake correction for great alpine lakes (correction density -1 670 kg/m3), 6. calculation of the final complete Bouguer anomalies based on normal field (Somigliana formula with GRS80 parameters, free-air correction using Taylor series expansion to the 2nd order) and particular corrections including also the atmospheric correction.

The quality control of input data was performed based on the height differences between the point data and particular elevation models. Several thousand points with height residuals higher than chosen threshold (±50 m) were excluded. The available detailed local elevation models (resolution 10 – 20 m) were compared with global model MERIT (resolution 25 m).

The most significant methodological innovation is the ellipsoidal heights concept using straightforward calculation of mass/bathymetric corrections in respect to the ellipsoid instead of using the geophysical indirect effect computation. Our specially developed program Toposk was used for mass/bathymetric correction calculation (the standard distance of 166.7 km was used for the first version of the map) as well as for the calculation of lake corrections. Mass corrections amount to hundreds of mGal, while the lake corrections reach more than 5 mGal locally. Atmospheric effect taking into account topography was also calculated and compared with standard atmospheric correction.

 
Quantifying long term evolution of fluvial channel in glacier forefield
Authors: Piermattei Livia , Heckmann Tobias , Altmann Moritz , Rom Jakob , Fleischer Fabian , Stark Manuel , Haas Florian , Pfeifer Norbert , Becht Michael
Published: March 2020

Alpine rivers have experienced considerable changes in channel morphology over the last century. Human disturbance and natural factors are the main drivers of changes in channel morphology that modify natural sediment and flow regimes at local, catchment and regional scale. River sediment loads are likely to increase due to increasing snow and glacier melt runoff, facilitated by climate changes. Additionally, channel erosion and depositional dynamics and patterns are influenced by sediment delivery from rock walls, hillslopes, and sediment in the forefields of retreating glaciers. Land cover changes may facilitate or obstruct runoff and soil degradation.

In order to reliably assess the magnitudes of the channel changing processes and/or their frequencies due to recent climate change, the investigation period needs to be extended to the last century, ideally back to the end of the Little Ice Age. Moreover, a high temporal resolution is required to account for the history of changes of channel morphology and for better detection and interpretation of related processes.

The increasing availability of digitised historical aerial images, together with advancements of digital photogrammetry, provides the basis for reconstructing and assessing long-term evolution of the surface, both in terms of planimetric mapping and generation of historical digital elevation models (DEMs). This work presents the temporal evolution of fluvial channel morphology in Kaunertal, Austria, spanning twenty periods from 1953 to 2019. Here we use photogrammetric analysis of recent and historical images, together with LiDAR and drone-based photogrammetric DEMs, to quantify the river changes in terms of channel incision, riverbank erosion, as well as the spatial patterns of channel erosion and deposition and the amounts of mobilized sediment. We show that geomorphic changes are mainly driven by deglaciation, i.e. glacier retreat, and sediment delivery from recently deglaciated steep lateral moraines. Overall, this work contributes to better understand the links between channel changes and climatic factors and highlights similarities and differences in the evolutionary trajectories of the main rivers in the catchment.
Characterization of the fluid-rock interaction in the Colombian emerald deposits
Authors: Moreno Boada Germán David , Song Sheng-Rong
Published: March 2020

Emerald is a high-value gemstone and a variety of the Beryl group that contains traces of Chromium and Vanadium which give them their characteristic green color.  Colombian emerald deposits have been found within two main narrow belts both of them located in the Eastern Cordillera, one of the three main ranges that constitute the Colombian Andes along with the Central and Western Cordilleras.

Several authors (Kozlowski et al. 1998; Ottaway et al. 1994; Giuliani et al. 1993b) have established that the interaction between hydrothermal fluids and the emerald hosted black shales, leading into an intense albitization and carbonation of the host rocks with the depletion of many major and trace elements, resulting into the emerald mineralization along with the deposition of calcite, dolomite, pyrite, albite, quartz and rarely parasite (Giuliani et al.1995). However, the fluid-rock interaction has not been clearly explained and stablished for both productive and non-productive areas in order to provide a more useful guide for further emerald exploration.   

Inductively Coupled Plasma Atomic Mass Spectroscopy (ICP-AMS) along with X-ray Diffraction (XRD) and Scanning Electron Microscope (SEM) data were obtained from unaltered and altered host rocks including siliceous black shales, carbonated black shales, limestones, and dolomitic limestones. The results were analyzed to establish the geochemical relationships between different lithologies and the occurrence or absence of emerald mineralization for the different emerald belts.

The concentration of major, trace and REE elements and particularly the of  Cr, V and Be in the host rocks and the distribution over the studied areas will provide a better understanding of whether those contents are sufficient not only for the formation of emeralds besides of the different minerals in paragenesis. The results of the ongoing results are expected to be used as a possible exploration tool in favor to identify the areas with low potential for emerald mineralization.
Re-colonization of sterile soil samples during long term field exposure
Authors: Herre Michael , Marschner Bernd , Marhan Sven
Published: March 2020

The distribution of soil organic matter and microbial biomass in subsoils is much more heterogeneous than in the topsoil due to a more localized input of fresh substrate and nutrients from rhizodeposition and preferential flow paths forming hotspots of microbial activity. However, the remaining bulk soil also contains substantial amounts of labile substrates that are readily mineralized during lab incubation experiments. We therefore hypothesized that one reason for this is that potential consumers are spatially separated from these substrates due to the low microbial densities in subsoils. Consequently, hotspots are not only formed through high substrate inputs but also through a higher abundance and diversity of microorganisms compared to the bulk soil due to inputs of cells and spores with the soil solution or through hyphal growth. However, little is known about the colonization potential or dynamics of microorganisms in the subsoil.

In November 2018, we started a field experiment to investigate the re-colonization potential of microorganisms by exposing 24-well microplates containing sterilized soil samples in the field at two different depths (topsoil: 10 cm, subsoil 60 cm) at a beech forest site in northern Germany. After 6 and 12 months, samples from each well and from the intact soil compartments above each well were analyzed for enzyme activities (hydrolytic enzymes using MUF and AMC substrates), microbial activity parameters (soil respiration and SIR using the MicroResp®) and the microbial community structure (quantitative PCR).

We expect (1) different temporal dynamics of re-colonization between top- and subsoil samples; (2) that the recolonization potential is related to the microbial activity in the soil compartments above the exposed samples and (3) that the heterogeneous re-colonization is maintained throughout the field exposure and thus indicates the relevance of preferential flow paths for microbial transport especially in subsoils.

First results of the SIR assays after 6 months of field exposure show that in the topsoil microbial activity has been re-established in all of the wells, but is still below the mean activity in the undisturbed soil above the sterilized samples. In all subsoil samples, the re-established microbial activity was much lower and even below detection limit in some of the wells. In both depths, the SIR assays show a very patchy distribution of wells with higher microbial activities indicating that the influx of organisms is limited to small areas from the soil above the exposed containers.
The role of non-structural carbohydrates in simulations of ecosystem carbon fluxes.
Authors: Jones Simon , Rowland Lucy , Cox Peter , Hemming Debbie , Wiltshire Andy , Williams Karina , Parazoo Nicolas , Liu Junie , da Costa Antonio , Meir Patrick , Mencuccini Maurizio , Harper Anna
Published: March 2020

Accurately representing the response of ecosystems to environmental change in land surface models (LSM) is crucial to making accurate predictions of future climate. Many LSMs do not correctly capture plant respiration and growth fluxes, particularly in response to extreme climatic events. This is in part due to the unrealistic assumption that total plant carbon expenditure (PCE) is always equal to gross carbon accumulation by photosynthesis. We present and evaluate a simple model of labile carbon storage and utilisation (SUGAR), designed to be integrated into an LSM, that allows simulated plant respiration and growth to vary independently of photosynthesis. SUGAR buffers simulated PCE against seasonal variation in photosynthesis, producing more constant (less variable) predictions of plant growth and respiration relative to an LSM that does not represent labile carbon storage. This allows the model to more accurately capture observed carbon fluxes at a large-scale drought experiment in a tropical moist forest in the Amazon, relative to the Joint UK Land Environment Simulator LSM (JULES). SUGAR is designed to improve the representation of carbon storage in LSMs and provides a simple framework that allows new processes to be integrated as the empirical understanding of carbon storage in plants improves. The study highlights the need for future research into carbon storage and allocation in plants, particularly in response to extreme climate events such as drought.
Developing a variable time-interval continuous verification method for ensemble flood forecasts
Authors: van Andel Schalk Jan
Published: March 2020

Most continuous verification metrics for hydrometeorological forecasts are based on equal interval forecasts and observations (e.g. daily, 6-hourly, etc.). For some purposes of verification, however, it might be more beneficial to have variable time intervals that take into account the duration of events, e.g. rainfall or flood event (or discharge exceeding a flood warning threshold). Such verification, however, is challenged by defining the length of the non-event intervals for scoring correct rejections and false alarms, needed for continuous verification.  The work presented here suggests how to approach this challenge and presents verification results of a continuous forecast verification method that take into account variable duration of events.
The study of storm and tsunami deposits in the geological record: Are we going in circles?
Authors: Switzer Adam D.
Published: March 2020

Studies on recent on the deposits of recent tsunami and tropical cyclone events have provided the research community with new insights on the utility of their deposits. In addition, they also provide for the evaluation of some criticisms and knowledge gaps for future studies. There remain no globally applicable sedimentological criteria for differentiating between tsunami and storms deposits in either washover sandsheets or boulder deposits. What has been compiled for the many deposits attributed to tsunamis and storms is a suite of geomorphological or sedimentary features or commonalities, often referred to as signatures. All deposits regardless of type must be considered in terms of the local setting, and be carefully analysed for spatial relationships. Geomorphological characteristics and sedimentary features must also be considered in the context of the local environment. When considered alone many of the reported signatures for storms and tsunamis are equivocal. In fact, many of the signatures from the literature for tsunami or storm deposition, including the presence of marine microfauna or increases in particular elemental concentrations merely indicate the marine source of the material. Hence, storm surges, sea level change or co-seismic subsidence may show similar sedimentological characteristics. Efforts to differentiating between tsunami and storm deposits have stagnated and new approaches are needed. Addressing this need I will discuss my views on where the coastal geohazard community can go from here.