bluuebunny/crossref_metadata_2025 huggingface dataset:
Biochar impact on tensile strength of Dystric Cambisol aggregates – a model study
Authors: Szewczuk-Karpisz Katarzyna , Tomczyk Agnieszka , Sokołowska Zofia , Turski Marcin , Cybulak Marta , Skic Kamil
Published: March 2020

Aggregate tensile strength is a significant parameter of soil structure. Adequate mechanical stability of aggregates promotes long-term crop productivity due to, inter alia, maintaining gas diffusion, facilitating root penetration and improving water infiltration. Soil aggregates characterized by high tensile strength are also resistant to erosion. Nowadays, intensive agriculture and environmental pollution contribute to clear deterioration of soil condition. The soil structure is often destroyed. In order to limit the negative phenomena, various soil additives are used, e.g. biochar.

In this paper, the effect of wood waste biochar on tensile strength and porosity of Dystric Cambisol artificial aggregates was examined. The experiments were performed on dry-air and wet soil aggregates non-containing and containing 0.1% or 5% dose of biochar. Tensile strength of the probes was determined using strength testing device (Zwick/Roell), whereas porosity – by mercury intrusion porosimetry (Micrometrics). The obtained results indicated that the biochar addition decreases tensile strength of all examined aggregates. This effect was more significant for higher biochar dose – 5%. This phenomenon is probably connected with formation of macropores of larger sizes within aggregates after the biochar addition.

Research was conducted under the project "Water in soil - satellite monitoring and improving the retention using biochar" no. BIOSTRATEG3/345940/7/NCBR/2017 which was financed by Polish National Centre for Research and Development in the framework of "Environment, agriculture and forestry" - BIOSTRATEG strategic R&D programme.
Predictive skill of atmospheric rivers in the Iberian Peninsula
Authors: Ramos Alexandre M. , Sousa Pedro M. , Dutra Emanuel , Trigo Ricardo M.
Published: March 2020

In recent years a strong relationship has been found between Atmospheric Rivers (ARs) and extreme precipitation and floods across western Europe, with some regions having 8 of their top 10 annual maxima precipitation events related to ARs. In the case of the Iberian Peninsula, the association between ARs and extreme precipitation days has also been well documented, particularly for western Iberia river basins.

Since ARs are often associated with high impact weather, it is important to study their medium-range predictability. Here we perform such an assessment using the ECMWF ensemble forecasts up to 15 days, for events that made landfall in western Iberian Peninsula during the winters spanning between 2012/2013 and 2015/16. IVT and precipitation from the 51 ensemble members of the ECMWF Integrated Forecasting System (IFS) ensemble (ENS) were processed over a domain including western Europe and contiguous North Atlantic Ocean.

Metrics concerning the ARs location, intensity and orientation were computed, in order to compare the predictive skill (for different prediction lead times) of IVT and precipitation analyses in the IFS. We considered several regional boxes over Western Iberia, where the presence of ARs is detected in analysis/forecasts, enabling the construction of contingency tables and probabilistic evaluation for further objective verification of forecast accuracy. Our results indicate that the ENS forecasts have skill to detect upcoming ARs events, which can be particularly useful to improve the prediction of associated hydrometeorological extremes. We also characterized how the ENS dispersion and confidence curves change with increasing forecast lead times for each sub-domain. We employed the standard ROC analysis to evaluate the probabilistic component of these predictions showing that for short lead times precipitation forecasts are more accurate than IVT forecasts, while for longer lead times this result is reversed (~10 days). Furthermore, we show that this reversal occurs at shorter lead times in areas where the ARs contribution is more relevant for winter precipitation totals (e.g. northwestern Iberia).

 

Acknowledgements

The work done was supported by the project Landslide Early Warning soft technology prototype to improve community resilience and adaptation to environmental change (BeSafeSlide) funded by Fundação para a Ciência e a Tecnologia, Portugal (FCT, PTDC/GES-AMB/30052/2017). A.M.R. was also supported by the Scientific Employment Stimulus 2017 from FCT (CEECIND/00027/2017).
Combining remote sensing and in situ observations to study the physical-biological coupling at fine scale: recent Mediterranean campaigns and outlook.
Authors: Doglioli Andrea M. , Grégori Gérald , d'Ovidio Francesco , Petrenko Anne A. , Barrillon Stéphanie , Fuda Jean-Luc , Thyssen Melilotus , Tzortzis Roxane , Izard Lloyd , Dumas Franck , Garreau Pierre , Pascual Ananda , Marrec Pierre , Rousselet Louise , Bhairy Nagib , Cyr Frédéric , Tedetti Marc , Berline Léo , Carlotti François
Published: March 2020

The oceanic fine scales are highly energetic features (eddies, fronts, meanders, filaments) with relatively short lifetimes (days/weeks to months). Due to their associated strong gradients in physical and biogeochemical properties, they crucially affect ocean physics and ecology with potential impacts at the climate scale. The temporal scale associated with these horizontal and vertical fine scales is the same as many important ecological processes including phytoplankton growth and competition. This temporal resonance is one of the reasons behind the fine-scale variability appearing in the marine ecosystems structure and related domains, including biogeochemical cycles, trophic food-webs up to resources and biodiversity.

Over the past few decades, great progresses have been made in characterizing fine scales through modeling. Remote sensing is also improving rapidly in terms of resolution, with landmark missions like SWOT expected to be operational very soon (2022). However, in situ sampling remains challenging due to the difficulties of mapping a large domain covering the length of a filament or the diameter of an eddy (~100km) at high spatio-temporal frequency (~km and ~daily).

Here we present some sampling strategies we are developing for addressing this issue by combining remote sensing and in situ multi-platform high-resolution sampling of physical, biogeochemical and biological variables. 

In a series of campaigns in the Mediterranean Sea (OSCAHR 2015, PROTEVSMED-SWOT 2018, FUMSECK 2019), satellite-based adaptive and Lagrangian strategies proved to be successful to target and follow fine scale structures in situ. When paired with in situ biological measurements, like automated cytometry, these strategies highlight the important role of the fine scales in structuring the phytoplankton community by acting as fluid dynamical barriers and biodiversity hot-spots.

To extend these observations to other regions, we support an international coordinated experimental effort of the fine scale community at several sites all around the world to fully exploit the great opportunities offered by the launch of the satellite SWOT.
Probability distributions of non-structural carbon ages and transit times provide insights in carbon allocation dynamics of mature trees
Authors: Herrera David , Muhr Jan , Hartman Henrik , Römermann Christine , Trumbore Susan , Sierra Carlos
Published: March 2020

In trees, the use of non-structural carbon (NSC) under limiting conditions impacts the age structure of the NSC pools. We compared model predictions of NSC ages and transit times for Pinus halepensis Mill., Acer rubrum L. and Pinus taeda L., to understand differences in carbon storage dynamics in species with different leaf phenology and growth environments. We used two carbon allocation models from the literature to estimate the NSC age and transit time distributions, to simulate carbon limitation, and to evaluate the sensitivity of the mean ages to changes in allocation fluxes. Differences in allocation resulted in different NSC age and transit time distributions. The simulated starvation flattened the NSC age distribution and increased the mean NSC transit time, which can be used to estimate the age of the NSC used, the NSC remaining in the system,  and the time it would take to consume the reserves. Mean NSC ages and transit times were sensitive to carbon fluxes in roots and allocation of carbon from wood storage. Our results demonstrate how trees with different storage traits are expected to react differently to starvation. They also provide a probabilistic explanation for the “last-in, first-out” pattern of NSC mobilization from well-mixed carbon pools. In addition, they unveil determinant sink fluxes in NSC dynamics for mature trees. These findings open the possibility to better understand NSC dynamics in mature trees based on estimated NSC ages and transit times in different tree organs of species with contrasting life strategies and growth environments.    
New insights on the dynamics of the Sumatra and Mariana complexes inferred from the comparative analysis of gravity data and model predictions
Authors: Bollino Arcangela , Marotta Anna Maria , Restelli Federica , Regorda Alessandro , Sabadini Roberto
Published: March 2020

Subduction is responsible for surface displacements and deep mass redistribution. This rearrangement generates density anomalies in a wide spectrum of wavelengths which, in turn, causes important anomalies in the Earth's gravity field that are visible as lineaments parallel to the arc-trench systems. In these areas, when the traditional analysis of the deformation and stress fields is combined with the analysis of the perturbation of the gravity field and its slow time variation, new information on the background environment controlling the tectonic loading phase can be disclosed.

Here we present the results of a comparative analysis between the geodetically retrieved gravitational anomalies, based on the EIGEN-6C4 model, and those predicted by a 2D thermo-chemical mechanical modeling of the Sumatra and Mariana complexes.

The 2D model accounts for a wide range of parameters, such as the convergence velocity, the shallow dip angle, the different degrees of coupling between the facing plates. The marker in cell technique is used to compositionally differentiate the system. Phase changes in the crust and in the mantle and mantle hydration are also allowed. To be compliant with the geodetic EIGEN-6C4 gravity data, we define a model normal Earth considering the vertical density distribution at the margins of the model domain, where the masses are not perturbed by the subduction process.

Model predictions are in good agreement with data, both in terms of wavelengths and magnitude of the gravity anomalies measured in the surroundings of the Sumatra and Marina subductions. Furthermore, our modeling supports that the differences in the style of the gravity anomaly observed in the two areas are attributable to the different environments – ocean-ocean or ocean-continental subduction – that drives a significantly different dynamic in the wedge area.
Characterization of CO2 Induced Wellbore Cement degradation by Micro CT
Authors: Wang Yan , Zhang Liwei , Miao Xiuxiu
Published: March 2020

Wellbore cement integrity under CO2 geologic storage (CGS) conditions is a key factor to assure safe and permanent storage of CO2. Wellbore cement integrity may be impaired and the structure of cement may be altered as a result of CO2 attack. To understand how CO2-induced structure alteration in oil well cement under CGS conditions affects well integrity in CGS projects, this paper reports an experiment of reaction between CO2 and oil well cement under CGS conditions. Samples were scanned by Micro CT before and after reaction. The Micro CT is capable of operating at 140KV and 10W, has a maximum resolution of 10µm. To simulate the reaction between CO2 rich brine and oil well cement at CGS conditions, our team has developed a testing system which provides the storage temperature and pressure. 

The samples were made by standard class G oil well cement used for CGS pilot projects. The cement was cured at CO2 storage formation conditions: 62℃, 17MPa, and 1 wt% NaCl solution. The curing was maintained for 14 days. The diameter of the samples was 10 mm. Every sample contained a small borehole at center (around 1 mm diameter) that made the samples suitable for examining seepage through small leakage pathways within cement. During the reaction experiment, the samples were placed in the high-pressure, high-temperaure testing system for 14 days, given a temperature of 62℃ and a CO2 partial pressure of 17MPa. The goal of this experiment is to evaluate how the geochemical reactions between dissolved CO2 and cement affect structure of the cement. Change of borehole geometry was not observed in the Micro CT images. However, a region with decreased porosity around the borehole due to CaCO3 precipitation and a region with increased porosity around the borehole due to Ca(OH)2 and C-S-H dissolution were observable. Initial distribution of cementitious materials and solution buffering governed the width of the high-porosity region and CaCO3 precipitation region. This study demonstrates a 3-D sample characterization technique that can be used to investigate CO2-induced structure alteration of oil well cement. 
Biogeocaching – a scavenger hunt for the treasures of biology around Lake Lunz
Authors: Hödl Romana , Attermeyer Katrin , Coulson Laura , Harjung Astrid
Published: March 2020

Climate change and decreasing biodiversity are currently hot topics in the media. Freshwaters in the alpine region are good indicators of climate change and, hence, perfect examples for illustrating these threats. Here, we want to share our idea for a Geocaching path (similar to the popular treasure hunt game) that is used to educate the public about the biology of freshwaters. We want to educate the visitors about the natural environment and the consequences of climate change and decreasing biodiversity for our aquatic ecosystems and livelihoods. In particular, we want to show the approaches of scientists to understand and predict these threats and, furthermore, how our society can find solutions to protect aquatic ecosystems.

Lake Lunz is a very popular place for tourists. Visitors enjoy walks around the lake as well as swimming. Close by is also one of the oldest lake research stations (WasserCluster Lunz – Biologische Station), where scientists from all over the world are currently conducting on aquatic ecosystems. The project received funding from the EGU Public Engagement Grant in 2019. The GPS coordinates for the Geocache (a small treasure box) will be hidden in the answers to several questions about freshwater biology that will lead the participants around the lake, a search we termed “Biogeocaching”. The answers can be found on different informational signs that will be set up around the lake and at the experimental sites and research facilities of WasserCluster Lunz. After finishing the path, the participants will have learned about ecology of alpine lakes and the research activities at WasserCluster Lunz.

We think that geocaching as a treasure hunt is a playful way for people of all ages to discover nature. The combination of an outdoor recreational activity with information about freshwaters, climate change, and decreasing biodiversity –Biogeocaching - will sensitize the public to and raise awareness of these hot topics in the field of Earth Sciences. We hope to encourage other researchers and research institutes to develop something similar on their topic and research.
Augmenting satellite-derived soil moisture with multiple data streams using machine learning
Authors: Orth Rene , Oh Sungmin
Published: March 2020

Soil moisture plays a key role in land-atmosphere interactions through its influence on the energy and water cycles. Furthermore, its spatiotemporal variations can affect the development and persistence of extreme weather events. Consequently, soil moisture information is required for a wide range of research and applications, such as agricultural monitoring, flood and drought prediction, climate projection, and carbon-cycle modeling. Despite its scientific and societal importance, observations of soil moisture are sparse, in particular across time and at large spatial scales. Only models and satellite retrievals can provide global soil moisture information. While the ability of land surface models to represent the complex land-atmosphere interplay is still limited, satellite-based soil moisture data are a valuable alternative. However, these products suffer from a scaling based on models, and can only capture the top few centimeters of the soil. 

In this study, we aim to augment satellite-based soil moisture data using machine learning. For this purpose we integrate satellite soil moisture with multiple hydro-meteorological data streams to derive global gridded soil moisture using Long Short-Term Memory (LSTM) neural networks. These networks are trained using in-situ soil moisture measurements as target data. With the resulting self-learned relationships, the LSTMs can produce in-situ-like soil moisture globally. We further analyze the implications of using point-scale target data to infer large scale information. The new dataset is derived separately for the surface and the deeper soil, thereby extending beyond the range covered by the satellite-based products. The integration of many data streams and multiple soil moisture observations through a powerful synergistic technique offers the potential to yield high accuracy. This is tested through rigorous cross-validation of the derived dataset. Finally, the planned datasets will permit consistent long-term, large-scale analysis to enhance our understanding of the hydrology-biosphere-climate interplay, to better constrain models and to support hydrological hazards monitoring and climate projections.
Experimental Evaluation of Equivalent Permeability for Permeable Interlocking Concrete Paver (Soil-Block) Composite System
Authors: Ahn Jaehun , Lee Yunje
Published: March 2020

Increase in impermeable area and frequency of intense rainfall cause flooding damages in urban areas. Permeable Interlocking Concrete Paver (PICP) system, which is a composite system comprised of soils and blocks, is considered as one of the solutions to improve the urban water environment, and its applications are increasing rapidly worldwide. It is important to evaluate the initial permeability and its reduction due to clogging. In this study, the permeability and effect of clogging were evaluated based on experimental methods developed. The equivalent permeability and its degradation of PICP systems were successfully evaluated using the prodecure developed, and the equation for equivalent permeability presented quite a good agreement with the experimental results.

ACKNOWLEDGEMENT : The authors would like to thank the Ministry of Land, Infrastructure, and Transport of Korean government for the grant from Technology Advancement Research Program (grant no. 20CTAP-C152124-02) and Basic Science Research Program (grant no. 2017R1D1A3B03034563) through the National Research Foundation of Korea (NRF) funded by the Ministry of Education.
Coupling USArray and satellite gravity data – an integrated conductivity, density and seismic velocity model of the western USA
Authors: Weise Bernhard , Moorkamp Max , Fishwick Stewart
Published: March 2020

The EarthScope USArray project provides high quality magnetotelluric and seismic observations, which have been used to identify tectonic boundaries of the USA. Combining these data sets together with satellite gravity observations, we investigate how the different data sets can complement each other in order to find a consistent model of the subsurface. Using a cross-gradient constraint, we first invert the magnetotelluric and gravity data sets in order to demonstrate the feasibility of our approach and to identify any difficulties. Once a joint conductivity and density model is found, we perform a full joint inversion of all three data sets. By comparison with models derived from separate inversions of the individual observables we can show how the different data sets interact. Examining the magnitude of the cross-gradient lets us distinguish parts of the model where a good agreement of the recovered structures has been achieved from those where differing patterns are necessary in order to achieve an acceptable data fit. In this presentation we will give an overview of our approach, highlight our strategy and show results from individual and joint inversions.
Mid-altitude cusp dynamics and properties during the IMF By dominated intervals
Authors: Bogdanova Yulia , Escoubet C.-Philippe , Fear Robert , Trattner Karlheinz , Berchem Jean , Fazakerley Andrew , Pitout Frederic
Published: March 2020

Observations inside the cusp can be used as distant monitoring of the large-scale geometry and properties of the magnetic reconnection at the magnetopause. The recent modelling and observations of the cusp and flux transfer events in the vicinity of the magnetopause show that the reconnection can occur along the X-line extended over many hours of magnetic local time (MLT), comprising sites of both component and anti-parallel reconnection scenarios. Such observations are in contradiction to the statistical DMSP studies showing that the cusp is rather limited in magnetic local time with an average size 2.5 hours of MLT. Moreover, some past observations indicate that the cusp is moving in response to the changes of the IMF By component, suggesting that the cusp is formed due to anti-parallel reconnection along the X-line limited in MLT.

In this presentation we analyse several events of the mid-altitude cusp observations during the Cluster campaign when the satellites cross the cusp mainly along the longitude in a string-of-pearls configuration during an Interplanetary Magnetic Field (IMF) configuration with a stable and dominant IMF By-component. During this particular Cluster orbit it was possible to define the dawn and dusk cusp boundaries and to study plasma parameters inside different parts of the cusp region. The observations will be discussed in terms of the cusp extension, cusp motion, and possible formation of the ‘double’ cusp structures. Finally, we will consider what these observations reveal about the large-scale reconnection geometry at the magnetopause.
Mantle flow under the Central Alps: Constraints from non-vertical-ray SKS shear-wave splittting
Authors: Löberich Eric , Bokelmann Götz
Published: March 2020

The association of seismic anisotropy and deformation, as e.g. exploited by shear-wave splitting measurements, provides a unique opportunity to map the orientation of geodynamic processes in the upper mantle and to constraint their nature. However, due to the limited depth-resolution of steeply arriving core-phases, used for shear-wave splitting investigations, it appears difficult to differentiate between asthenospheric and lithospheric origins of observed seismic anisotropy. To change that, we take advantage of the different backazimuthal variations of fast orientation φ and delay time Δt, when considering the non-vertical incidence of phases passing through an olivine block with vertical b-axis as opposed to one with vertical c-axis. Both these alignments can occur depending on the type of deformation, e.g. a sub-horizontal foliation orientation in the case of a simple asthenospheric flow and a sub-vertical foliation when considering vertically-coherent deformation in the lithosphere. In this study we investigate the cause of seismic anisotropy in the Central Alps. Combining high-quality manual shear-wave splitting measurements of three datasets leads to a dense station coverage. Fast orientations φ show a spatially coherent and relatively simple mountain-chain-parallel pattern, likely related to a single-layer case of upper mantle anisotropy. Considering the measurements of the whole study area together, our non-vertical-ray shear-wave splitting procedure points towards a b-up olivine situation and thus favors an asthenospheric anisotropy source, with a horizontal flow plane of deformation. We also test the influence of position relative to the European slab, distinguishing a northern and southern subarea based on vertically-integrated travel times through a tomographic model. Differences in the statistical distribution of splitting parameters φ and Δt, and in the backazimuthal variation of δφ and δΔt, become apparent. While the observed seismic anisotropy in the northern subarea shows indications of asthenospheric flow, likely a depth-dependent plane Couette-Poiseuille flow around the Alps, the origin in the southern subarea remains more difficult to determine and may also contain effects from the slab itself.
Europe Windstorm variations: past, present and future
Authors: Cusack Stephen , Panosetti Davide
Published: March 2020

Ten years ago, we studied 101 years (1910-2010) of wind observations at five stations spread throughout the Netherlands, and representative of a wider area in Europe containing regions of dense exposure. The raw wind speed data were homogenised using detailed station metadata to account for changes in observation practises, then processed to form a windstorm loss index timeseries. Our analysis found large changes in annual storm losses at multidecadal timescales, with two minima occurring in the 1960s and the 2000s. The more recent minimum was three to four times lower than the century-scale peak of indexed losses in the 1980s and early 1990s and primarily driven by the reduced rate of occurrence of damaging storms.

We recently extended the storm loss timeseries up to 2019 and results confirmed what most of us expected: the lull continues. A recent industry survey indicated the ongoing quiet period is the top science issue for European windstorms, presumably because its large amplitude dwarfs other uncertainties in storm loss climate. The burning question for re/insurance is: what to expect over the next few years? What roles will natural climate variability and anthropogenic forcings play in the medium-term future evolution of our storm climate? Researchers have begun to supply some answers, finding strong empirical links between Arctic sea-ice, the state of the North Atlantic Ocean, and European winter climate, backed up by process-based studies connecting these variables. We will review their findings in the context of storm loss variability, then identify questions which could be key to anticipating the storm activity over the next few years.
Persisting effects of ligneous organic soil amendments on CO2, N2O and CH4 emissions in relation to moisture content in northern agricultural clay soil
Authors: Peltokangas Kenneth , Havisalmi Jimi , Heinonsalo Jussi , Karhu Kristiina , Kulmala Liisa , Liski Jari , Pihlatie Mari
Published: March 2020

In agriculture, organic soil amendments are envisioned to mitigate climate change through carbon sequestration. However, the full impact of the organic amendments on soil physico-chemical dynamics is still poorly understood. We conducted a laboratory incubation to assess the net climate effect of four ligneous organic amendments: two biochars (willow and spruce) and two fiber byproducts of paper and pulp industry. Soil samples were collected from a soil-amendment field experiment at Qvidja farm, South-West of Finland. Soil samples were sieved, air-dried and adjusted to 30%, 50%, 80% and 110% of water holding capacity (WHC), and incubated for 32 days in standard laboratory conditions. Greenhouse gas (GHG) emissions were measured after 1, 5, 12, 20 and 33 days. 

The carbon dioxide (CO2) emissions were highest at 80% WHC, and lowest at severely water stressed conditions at 30% WHC. The organic amendments did not have an observable effect on CO2 dynamics. The CO2 emissions correlated linearly with soil moisture and microbial biomass nitrogen. Nitrous oxide (N2O) emissions were systematically lower in the amended soils compared to the control soil, and independent of soil nitrate concentrations. Without organic amendments, N2O emissions increased exponentially with soil moisture content. Methane (CH4) emissions fluctuated throughout the incubation, exhibiting mostly negative values. Consequently, CH4 emissions played only a minor role in the GHG budget.

CO2, N2O and CH4 emissions, calculated as CO2 equivalent, exhibited a linear correlation with the moisture gradient. CO2 dominated the GHG budget up to a moisture of 80% WHC, but was superseded by N2O emissions at 110% WHC. The results indicate that soil moisture content is critically affecting the GHG emissions and that while organic soil amendments may have persisting effects on GHG exchange, they primarily occur through N2O dynamics.
How does the flow affect the evolution of solution pipes ?
Authors: Magni Silvana , Cooper Max , Szymczak Piotr
Published: March 2020

Dissolution by a reactive flow is a complex phenomenon influenced by a number of different parameters, including flow rate, diffusion rate of the reactant, reaction rate and the pore space characteristics of the host rock. Depending on the values of these parameters, the dissolution patterns will have different morphological features. In particular, there is range of parameters where the dissolution front becomes unstable, which is accompanied by a formation of pronounced dissolution channels, which are called solution pipes in geological literature and wormholes in the petroleum industry, where they are produced to stimulate the flow from oil reservoirs. In the natural settings, these features are formed in rocks with a very high porosity and then with a rather large flow rate. Their shapes are strongly related to their characteristic sizes. At the macroscale (1-10metres) they are usually almost cylindrical with a diameter from a few cm up to a meter, while at microscale they show a highly ramified, fractal-like shape. To investigate this variability and to understand their formation and evolution, we are conducting microfluidic experiments using a self-constructed microfluidic cell. We are using a system consisting of two polycarbonate chips in which it is possible to have a control on flow rate and on the aperture. The lower plate has an indentation that can be filled with gypsum, while on the upper chip there is a reservoir that allows water to be supplied to the system in a controlled way. We are using powder gypsum during these experiments because it has a very simple chemistry, high solubility in water and therefore allows a greater speed of dissolution The two chips are joined together with an ultrathin, double coated tape of variable thickness that allows us to control the aperture of the system, which can thus be regarded as an analog fracture. As the gypsum chip is dissolved, we observe the appearance of fingers of different shapes, depending on the flow rate and the aperture. We report the results of these experiments and relate the observed features with the natural shapes found in the karst systems. We also investigate how the shapes of the pipes change as we vary the flow rate periodically, which reflects annual variations in the flow in the natural karst systems.

Key words: dissolution, solution pipes, microfluidics

 

 
Probing the use of coccolith geochemistry as a proxy for past carbon dioxide concentrations - Insights from Termination II in the Northern Atlantic Ocean
Authors: Godbillot Camille , Hermoso Michaël , Minoletti Fabrice
Published: March 2020

Despite their omnipresence in pelagic carbonate sediments, the coccoliths, the calcite biominerals produced by the coccolithophores, have historically been under-exploited in palaeoenvironmental studies. This is due, in part, to their small size (2-20 microns), which makes them difficult to isolate from other particles, and to the large differences in isotopic composition existing between coccolith calcite and equilibrium conditions. This so-called “vital effect” complicates the use of coccolith geochemistry to derive paleoclimatic signals with confidence. Recent studies from cultured and fossil coccoliths have shown that the oxygen and carbon isotopic compositions of the coccoliths are particularly sensitive to the availability of CO2 in the environment, upon which the coccolithophores rely for their photosynthetic activity. Therefore, our approach here is to test whether the coccolith geochemistry can be used as a novel proxy for surface ocean and atmospheric CO2 concentrations.

In this study, different size fractions of coccoliths were extracted from carbonate sediments of site MD95-2037 in the Northern Atlantic Ocean and run for isotopic analysis. Using calibrations between coccolith vital effects and seawater [CO2] from culture studies, we present a seawater [CO2] curve for site MD95-2037 across Termination II (130 kyrs). The curve was in turn translated into atmospheric pCO2 estimates taking into account changes in ancillary parameters (such as temperature). Coccolith-derived CO2 concentrations yield comparable values, both for the absolute numbers and trends, to the record from Vostok ice cores. This coherency is confirmed by a 80 ppm-shift in pCO2 concentrations in the North Atlantic between glacial and interglacial times reconstructed from the coccolith record.

Altogether, these datasets confirms that coccolith geochemistry can indeed be used to reconstruct past changes in [CO2]sw. Perspectives for this study include providing the scientific community with a new record of pCO2 for periods extending beyond the Vostok record, in particular the Mid-Pleistocene Transition, where a decrease in global pCO2 has been put forward to explain the shift from 41 kyr- to 100 kyr-cycles in glacial-interglacial cycles.
New insights into SMOS Sea Surface Salinity retrievals in the Arctic Ocean.
Authors: Supply Alexandre , Boutin Jacqueline , Vergely Jean-Luc , Kolodziejczyk Nicolas , Reverdin Gilles , Reul Nicolas , Tarasenko Anastasiia
Published: March 2020

Since 2010, the Soil Moisture and Ocean Salinity (SMOS) satellite mission monitors the earth emission at L-Band, providing the longest time series of Sea Surface Salinity (SSS) from space over the global ocean. However, retrieving SSS at high latitudes with a reasonable accuracy remains challenging, in particular due to the low sensitivity of L-Band radiometric measurements to SSS in cold waters and to the contamination of SMOS measurements by the vicinity of continents and sea ice as well as the presence of Radio Frequency Interferences. In this paper, we assess the quality of weekly SSS fields derived from swath-ordered instantaneous SMOS SSS (so called Level 2) distributed by the European Space Agency. These products are filtered according to new criteria. We use the pseudo-dielectric constant retrieved from SMOS brightness temperatures to filter SSS pixels polluted by sea ice. We identify that the dielectric constant model and the sea surface temperature auxiliary parameter used as prior information in the SMOS SSS retrieval are significant sources of uncertainty. We develop a novel correction methodology accordingly.

SSS Standard deviation of differences (STDD) between weekly SMOS SSS and in-situ near surface salinity significantly decrease after applying the SSS correction, from 1.46 pss to 1.26 pss. The correlation between new SMOS SSS and in-situ near surface salinity reaches 0.94. SMOS estimates better capture SSS variability in the Arctic Ocean in comparison to TOPAZ reanalysis (STDD = 1.86 pss), particularly in river plumes fresher by about 10 pss than surrounding waters. Furthermore, comparisons with in-situ measurements ranging from 1 to 11 m depths identify huge vertical stratification in fresh regions. This emphasizes the need to consider in-situ salinity as close as possible to the sea surface when validating L-band radiometric SSS which are representative of the first top centimeter.
Evaluation of Aurora Activity Obtained from Abisko and Kiruna Ground Based Observation
Authors: Sugihara Kiyonobu , Yamauchi Masatoshi , Kobayashi Makoto , Koichi Shin , Nishi Masahiro
Published: March 2020

Available space weather forecasts mainly use data from the Sun and upstream interplanetary monitoring, to provide the early warning. Although the accuracy is improving, it cannot provide onset timing and actual strength of the substorm and its propagations better than 1 hour. A higher-accuracy forecast requires monitoring of the ionosphere (e.g., aurora and geomagnetic field). In this sense, it is also necessary to develop a value-based nowcast based on such monitoring. In EGU 2018, Yamauchi et al. has proposed simple index showing aurora and geomagnetic conditions using 1-minute resolution values from Kiruna. This study improved in the following directions:

(1) We used 1-sec resolution data and optimized the indices above: By using 1-sec values, the products representing variation (standard deviation and peak-to-peak variation) can be obtained every minute and improved, whereas combination of ∑L3 (or ∑L*exp(L)) and area of aurora found to be the best in representing the aurora activity, where L is luminosity of each pixel defined by HLS color code. Using these values, we confirmed that the intensity of the aurora was different for the same magnetic variation between before and after the strongest aurora (substorm onset). Therefore, it is necessary to add a condition of "increasing trend" of both aurora and magnetic variation from the viewpoint of forecasting.

(2) We compared the results from two different places (Abisko and Kiruna in Sweden) that are 89 km apart in linear distance. Our Abisko camera system (DASC, Digital All Sky Camera) is in operation since March 2014. When the aurora was observed at both sites, the shapes of the aurora at both sites are sometimes quite different at the same time. In addition, the timing of the brightest aurora (∑L3 or ∑L*exp(L) is maximum) was different between both sites. These results confirm that the aurora had a three-dimensional structure, which has been known for many years.

(3) Using superposed epoch analysis, we also took statistics of last 10 minutes before the largest aurora (in the index mentioned above) occurred.
Integration of Hydrologic Signatures for Model Evaluation in Gauged and Ungauged Catchments
Authors: Kiraz Melike , Wagener Thorsten , Coxon Gemma
Published: March 2020

Rainfall-runoff models are widely used tools in catchment hydrology. Their evaluation is mostly based on comparing observed and simulated discharge values and various statistical objective functions have been proposed to evaluate the agreement between these time series. However, model evaluations that are based on statistical objective functions often does not provide the modeller with much insight on why the model fails to represent the hydrology of the real-world system.  Other, hydrologically meaningful indices or signatures have been proposed instead that quantify the hydrologic response characteristics of the catchment. They can also be regionalized and thus provide a potential opportunity for model evaluation in ungauged basins.

Our study investigates how to best integrate hydrological signatures in an objective function for model evaluation to shift the focus of objective functions to evaluate basic hydrological functions of catchments. We propose a signature-based hydrologic efficiency metric that can be derived from locally observed or regionalised hydrologic signatures.  The metric improves upon the Kling-Gupta Efficiency (KGE) metric by replacing its three components with hydrologic signatures characterising the water balance (or bias), the damping (or variance) and the timing of flows (or correlation). Additionally, we use these hydrologic signatures with the physical characteristics (i.e. catchment attributes) in some regionalization approaches such as linear, nonlinear regression and random forests for streamflow predictions in ungauged catchments. We test our ideas on a large and diverse sample of 582 UK catchments using the CAMELS-GB dataset and show that the performance of the proposed metric works well.
Effects of long term application of chicken manure and spent mushroom substrate on organic matter and storage of water in sandy soils
Authors: Lipiec Jerzy , Usowicz Boguslaw , Klopotek Jerzy , Turski Marcin , Frac Magdalena
Published: March 2020

The aim of this study was to evaluate the effects of long-term application of exogenous organic matter on soil organic matter and water storage. Addition of organic matter is of importance in sandy soils that are in general poor in organic matter, acidic, conducive to drought and used in agricultural production throughout the world. In this study the sandy podzol (63-74% sand) was amended with chicken manure or waste spent mushroom substrate through more than 20 years. Soil organic matter content, water retention curves, acidity and structural stability were determined at three depths in the top 60 cm in organic amended and control plots. Enrichment of the soil with chicken manure and spent mushroom substrate caused increase in soil organic matter content in the top 0-20 cm from 1.34 to 3.50% and from 0.86 to 4.71%, respectively. Corresponding increases in field water capacity were from 13.6 to 31.8 m3 m−3 and from 17.7 to 27.2 m3 m−3. Both amendments improved soil structure, reaction and nutrient status. In general, these positive effects were greater in chicken manure than spent mushroom substrate amended soil and less pronounced at depths 20-40 cm and 40-60 cm compared to upper soil. Increase in the field water capacity and water storage capacity made the soils amended with  organic matter more drought resistant. Our findings provide valuable insights the spent mushroom substrate left after growing the mushrooms and chicken manure are environmentally friendly and economical viable soil management practices to increase soil quality and crop productivity.

 

 Acknowledgements

The work was partially funded by the HORIZON 2020, European Commission, Programme: H2020-SFS-4-2014: Soil quality and function, project No. 635750, Interactive Soil Quality Assessment in Europe and China for Agricultural Productivity and Environmental Resilience (iSQAPER, 2015–2020).
Changes in the basic ionic composition and other parameters of the Aral Sea and the Dead Sea waters during their drying
Authors: Andrulionis Natalia , Izhitskiy Alexander , Gertman Isaak , Yakushev Evgeniy , Zavialov Peter
Published: March 2020

In terms of water mass, salt lakes occupy 104 000 km3 (47 % of the total water volume of all lakes on the Earth), which is only slightly below that of fresh water lakes - 125 000 km3 (53%). Their waters are of certain economic importance, since they are used as raw materials for the extraction of valuable components and for therapeutic purposes. They also have a great influence on climate formation in the region. The drying out of the lakes entails an increase climate continentality. It also leads to an increase of frequency of dust and salt storms and storms that carry toxic substances over long distances from the source. This negatively affects public health. The drying of the Aral and Dead Seas is one of the largest environmental disasters of the 20th century. The reasons for their drying out are both natural such as global warming and aridization and anthropogenic factors such as diversions of river flows for the economic needs of the population of the regions. A sharp decrease in river runoff leads to a rapid drop in sea level, as well as to sharp interannual changes in the thermohaline structure and chemical composition of water. The annual runoff of the rivers has long ceased to fulfill the water resources of these water bodies.
We report the results of water sampling campaigns conducted in the Aral Sea (2014-2019) and the Dead Sea (2017-2019). The main ionic composition, salinity, density and other parameters of the waters of the Aral and the Dead Seas were obtained. We compare the hydrochemical characteristics of these water bodies and their changes during with historical data and with each other. The studied natural water bodies are terminal lakes, characterized by high salinity of water, which is many times higher than the salinity of ocean waters. The ratios of the main ions in the studied sources differ significantly between water bodies, as well as from similar ratios in the oceans. We determined ionic composition of these water samples using potentiometric titrator Titrando 905 (Metrohm). The density of samples was determined by the density meter DMA 5000M (Anton Paar). Currently, the Aral Sea is a complex of separate residual lakes with diverging hydrological and hydrochemical characteristics. The Dead Sea today is divided into two basins, the southern part of which is used for industrial purposes. Significant changes of the ionic composition of water with time were registered in both lakes. However, in the waters of the Aral Sea, these processes are much more intense and rapid than those in than the waters of the Dead Sea.
Worldwide water constrains on closing yield gaps
Authors: Droppers Bram , Supit Iwan , van Vliet Michelle , Ludwig Fulco
Published: March 2020

By 2050 a doubling of crop production may be necessary to meet the growing worldwide food demands. Several studies have indicated the potential to increase crop production by reducing the so-called yield gap, i.e. the difference between potential crop production and actual crop production. The focus is commonly on closing the yield gap by increasing nutrient supply through fertilization and/or by increasing irrigated cropland extent. This could potentially achieve water-limited production (limited by rainfall) in rain-fed croplands and climate-limited production (limited by temperature and radiation) in irrigated croplands. For irrigated croplands this assumes sufficient water availability for irrigation. However, water availability for irrigation may be insufficient under higher nutrient supply. In addition, irrigation expansion in upstream areas might negatively affect water availability in downstream areas.

We aim to quantitatively assess the worldwide water constrains to close yield gaps, accounting for various nutrient inputs. To assess water constrains we integrated a macro-scale hydrological model, the Variable Infiltration Capacity model (VIC-5 including human impacts; Droppers et al. in review), with a crop production model, the World Food Studies (WOFOST; de Wit et al. 2019) model. The VIC and WOFOST models were coupled for two-way interactions. The VIC model simulates the water and energy balance, including runoff, evapotranspiration, discharge and water stress for crop growth. Water stress is used in the WOFOST model to limit and adapt crop growth, e.g. limited biomass production and adjusted relative root production. Simulated crop characteristics (height, leaf area index, CO2 effects) are subsequently returned to VIC. By coupling these models we are able to assess the feedbacks between crop production and water availability globally.

References:

Droppers, B., Franssen, W. H. P., van Vliet, M. T. H., Nijssen, B., and Ludwig, F.: Simulating human impacts on global water resources using VIC-5. Geosci. Model Dev. Discuss., https://doi.org/10.5194/gmd-2019-251, in review, 2019.

de Wit, A., Boogaard, H., Fumagalli, D., Janssen, S., Knapen, R., van Kraalingen, D., ... & van Diepen, K. (2019): 25 years of the WOFOST cropping systems model. Agricultural Systems, 168, 154-167, https://doi.org/10.1016/j.agsy.2018.06.018.