bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of extraction temperature and time on the chemical and colloidal properties of dissolved organic matter
Authors: Andersson Erika , Meklesh Victoriia , Persson Per , Tunlid Anders , Olsson Ulf
Published: March 2020

Dissolved organic matter (DOM) is ubiquitous in terrestrial and aquatic ecosystems where it serves several important functions. It plays a central role in the landscape carbon balance, connects the terrestrial and aquatic environments, and acts as a vector for both nutrients and contaminants. Herein DOM is defined as dissolved molecules and suspended colloidal objects with a size below 0.2 μm. Despite the high interest of DOM, the important connection between the chemical composition of DOM and its colloidal structure are poorly understood. An active discussion in this field of research is how different extraction procedures affect the properties of DOM. Historically, sodium hydroxide extraction has been widely applied but today water extraction, more resembling the natural process, is commonly used. Even when using water as the solvent, the protocol for DOM extraction can differ greatly resulting in the study of different material.

We have systematically investigated the effects of extraction temperature and time on the chemical and colloidal properties of DOM extracted with water from a boreal forest soil. Chemical composition was determined using elemental analysis, pH, z-potential and 1H NMR while the colloidal structure was probed using a combination of dynamic and static light scattering (DLS, SLS) and small angle x-ray scattering (SAXS). Our results show that chemically the DOM is dominated by carbohydrates irrespective of extraction time and temperature.  Concentration and colloidal structure on the other hand are affected by these parameters. At high temperatures the concentration of all identified components increases, with the most notable difference in the carbohydrates. Also, with increasing extraction temperature the colloidal structure transforms from dense clusters to something resembling flexible polymer chains.

Contrast match experiments of DOM using small angle neutron scattering (SANS) have also been performed in preparation for studies on DOM-mineral interactions. The results show that the match point of DOM agrees with that of carbohydrates further confirming our results of the chemical composition. We believe our broad combination of complementary techniques is necessary to advance the understanding of DOM, in particular the correlation between chemical composition and colloidal properties. In the long-term it can help to reveal the importance of DOM size distribution and aggregation of DOM components for biogeochemically important processes in soil.

 
Efficiency of electromagnetic emission by electrostatic turbulence in solar plasmas with density inhomogeneities
Authors: Krafft Catherine , Volokitin Alexander
Published: March 2020

A new method to calculate semi-analytically the radiation efficiency of electromagnetic waves emitted at specific frequencies by electrostatic wave turbulence in solar plasmas with random density fluctuations is presented. It is applied to the case of electromagnetic emissions radiated at the fundamental plasma frequency ωp by beam-driven Langmuir wave turbulence during Type III solar bursts. It is supposed that the main radiation mechanism is the linear conversion of electrostatic to electromagnetic waves on the background plasma density fluctuations, at constant frequency. Due to the presence of such inhomogeneities, the rates of electromagnetic radiation are modified compared to the case of uniform plasmas. Results show that the radiation efficiency of Langmuir wave turbulence into electromagnetic emissions at ωp is nearly constant asymptotically, the electromagnetic energy density growing linearly with time, and is proportional to the average level of density fluctuations. Comparisons with another analytical method developed by the authors and with space observations are satisfactory.
Groundwater dynamics retrievals in Africa using SMOS soil moisture measurements
Authors: Pellarin Thierry , Oxarango Laurent , Cohard Jean-Martial , Depeyre Alban , Hector Basile , Kerr Yann , Vandervaere Jean-Pierre
Published: March 2020

ESA’s SMOS mission is celebrating 10 years of measurements in 2020 and is still producing soil moisture data of interest for many applications. One of the successes of this mission is its unexpected applications of soil moisture, such as thin ice sheets over the ocean, above ground biomass and carbon stocks, crop yields or rainfall estimation. We believe that knowledge of soil moisture time series contains information that are closely related to the functioning of the hydrosphere (infiltration, evaporation, groundwater recharge) and the biosphere (vegetation development, crop yield, carbon storage). These two compartments are traditionally studied using models forced by precipitation rates and atmospheric variables. However, beyond the difficulty of measuring the precipitation rate accurately from space, a non-negligible portion of rain does not infiltrate the soil either because it is intercepted by vegetation or because of the surface runoff.

In this study, we assume that SMOS retrieved soil moisture dynamics (0-5 cm) can inform us on much deeper soil horizons. Given that the water that reaches the root zone (0-200cm) and groundwater necessarily transits at some point through the surface, we can hypothesize that surface soil moisture dynamics intrinsically contains information on water dynamics in deeper layers.

To test this idea, we used Richards' 1D model and forced the first layer of the model with 5-cm in-situ soil moisture measurements from the AMMA-CATCH observatory sites in West-Africa. A variation of soil moisture at the surface generates moisture variations in the deeper layers according to the hydrodynamic parameters of the model: soil conductivity at saturation (Ks), shape parameters of the retention curve (α and m), soil porosity (θsat). For highly permeable soils, water rapidly infiltrates the soil column and creates a groundwater table with its seasonal dynamics. For more impermeable soils, water remains close to the surface and there is no groundwater recharge. This approach satisfyingly compares with in-situ measurements concerning both root zone soil moisture profiles and water table dynamics.

In a second step, the proposed methodology was applied to measurements derived from the SMOS satellite over the whole of Africa. To substitute in situ measurements, the GRACE satellite gravity data is used to compare with simulated soil water variations. This comparison allows to reject a lot of hydrodynamic parameters, and to select the best combination of the 4 parameters. Finally, the method makes it possible to produce maps of water table depths and their temporal dynamics at the scale of the African continent from information on surface soil moisture from SMOS (0-5cm) and soil water content from GRACE satellite.
A data-driven open-source architecture for service-oriented observation methods and in-stream process modeling of turbidity and dissolved organic matter
Authors: Wagner Robert , Goblirsch Tobias
Published: March 2020

The conservation and long-term protection of our environment require a better understanding of ecosystems through cross-domain integration of data and knowledge from different disciplines. Current methods used in applied environmental research and scientific surveys are not sufficient to address the heterogeneity and dynamics of ecosystems appropriately. To this end, an urgent need is seen in introducing new technology and methods for a service-oriented and holistic in-situ monitoring with increased spatio-temporal resolution and cutting edge functionalities. Recent developments in the field of digital information processing, the internet of things (IoT) or the the analysis of complex datasets are opening up new possibilities for data-based environmental research. This rapidly developing fields are calling for a disruptive paradigm shift towards a service-oriented earth observation (smart monitoring). To this end, future earth observation approaches will have a much stronger coupling between the modeling and the data acquisition. The development, implementation and evaluation of such an interface is one of the overall objectives of this project. To achieve this goal, a basic data model and a special hardware architecture must be defined. A realistic application scenario will be used to demonstrate the advantages of developing a monitoring strategy that is no longer based on static data collection but on the coupling of modeling and empiricism using integrated sensors for an advanced modeling. Since current methods have so far failed to allow a holistic assessment of varying, large-scale environmental phenomena there is a corresponding need for capable hardware which is specialized for exactly this purpose.

The project aims to introduce an integrated sensor system for advanced modeling of turbidity and dissolved organic matter using miniaturized optical sensors in the ultraviolett and infrared range. Moreover, a data-driven, open-source architecture for service-oriented observation methods and in-stream process modeling close to real-time was developed. In addition to the hardware-related requirements of such a sensor system, the creation of an interface between the physical environment (sensor level) or abstracted model assumption (model level) is a particular focus of the research project. A sampling theorem, the predictive object specific exposure (POSE), is introduced as an underlying measurement paradigm and data model. This allows to consider not only the measured value in the evaluation but also accompanied parameters, which is called the context of a measurement. The development and provision of a first adaptive sensor concept resulted in promising prototype enabling the possibility to record environmental data depending on decision criteria such as location, time or context. Thus, the project is representing an interesting practical contribution to Digital Earth.
Active seismic monitoring of CO2-saturated brine injection into a fault (CS-D experiment in the Mont Terri Rock Laboratory)
Authors: Grab Melchior , Zappone Alba , Rinaldi Antonio P. , Hellmann Sebastian , Wenning Quinn , Roques Clément , Obermann Anne , Madonna Claudio , Guglielmi Yves , Nussbaum Christophe , Maurer Hansruedi , Wiemer Stefan
Published: March 2020

Confirming the permanent containment is a key challenge for the storage of CO2 in deep underground reservoirs. Faults in the cap rock of such reservoirs are potential flow paths for the CO2 to escape. Our decametre-scale experiment at the Mont Terri Rock Laboratory aims to better understand mechanisms of CO2 leakage trough a fault, and to test strategies to monitor the propagation of CO2-saturated water through faults.

Two boreholes were drilled through the main fault in Mont Terri with packer-intervals dedicated to fluid-injection and hydraulic/geochemical monitoring. Another five boreholes in the close surrounding were equipped with various instruments for geotechnical and geophysical observations. During the first phase of the experiment, the hydraulic response of the fault was characterized with injections of formation water in a step-up mode at pressures up to 6.0 MPa. The second phase, which was still on-going at the time of the abstract submission, consists of a long-term (several months) injection of CO2-saturated formation water at a constant head of 4.5 MPa, which is below the fault opening pressure. All injection activities were monitored with active seismic measurements, along with a comprehensive set of hydraulic-, mechanical-, geochemical- and other geophysical surveys. We will present the active seismic imaging results from the step-up injection test and compare them with the other surveys. Additionally, preliminary results will be shown acquired during the long-term injection of CO2-saturated formation water into the fault.
Scour-resilient bio-inspired geomorphic designs: The Male Japanese Puffer Fish Nest
Authors: Clement Laurence , Campbell Callum , Hasibi Arezoo , Zare-Behtash Hossein , Valyrakis Manousos
Published: March 2020

In 1995, divers noticed a strange circular pattern on the seabed off Japan. The geometric formations mysteriously appeared and dissolved, and no-one knew what made them. Finally, the creator of these remarkable formations was found: a new species of pufferfish from the genus Torquigener. The male puffer fish executes a design of mathematical perfection in the form of ornate circles. As he swims along the seabed, he laboriously flaps his fins and rearranges the sand, creating the geomorphic feature dubbed crop circle by the pioneers who first noticed them. The significance to understand the puffer fish design is magnified when we consider that the nest is able to maintain its morphological features for long periods even though it is built entirely of mobile particles in an area where the flow does not stop.

As a relatively new discovery, the exact reasons behind why the pufferfish spends such a long time constructing and cultivating the nest it still a question that is shrouded in a substantial amount of mystery. Male puffer fish spend many days caring for the eggs, the only puffer fish genus to be overserved doing so; suggesting that Torquigener place an unusually large emphasis on ensuring the survival of their eggs. It is hypothesised that the nest is created as a mating display, as female puffer fish will visit the site, presumably assessing various characteristics of the nest. It is not known exactly what parameters the females judge the nest on; whether it be size, symmetric properties or decorative choice. However, due to some basic hydrodynamic experiments performed by Hiroshi Kawase, there is some evidence to suggest that there may be more to building the nest than solely attracting a mate.

Several questions therefore arise regarding the nest. Is there an evolutionary reason that male puffer fish build these nests? Which characteristics of a nest make it attractive to female puffer fish? Are the eggs safer in a nest, perhaps from incoming currents? How exactly does fluid flow through nest, and can it be replicated and simulated? This project begins to tackle these questions through a numerical investigation (CFD) of the fluid flow through the nest in order to identify key fluid dynamic features, which may play a significant role in egg incubation and spawning using Star CCM+.
A Machine Learning Approach to Cloud Masking in Sentinel-3 SLSTR Data
Authors: Jackson Samuel , Thiyagalingam Jeyarajan , Cox Caroline
Published: March 2020

Clouds appear ubiquitously in the Earth's atmosphere, and thus present a persistent problem for the accurate retrieval of remotely sensed information. The task of identifying which pixels are cloud, and which are not, is what we refer as the cloud masking problem. The task of cloud masking essentially boils down to assigning a binary label, representing either "cloud" or "clear", to each pixel.

Although this problem appears trivial, it is often complicated by a diverse number of issues that affect the imagery obtained from remote sensing instruments. For instance, snow, sea ice, dust, smoke, and sun glint can easily challenge the robustness and consistency of any cloud masking algorithm. The cloud masking problem is also further complicated by geographic and seasonal variation in acquired scenes.

In this work, we present a machine learning approach to handle the problem of cloud masking for the Sea and Land Surface Temperature Radiometer (SLSTR) on board the Sentinel-3 satellites. Our model uses Gradient Boosting Decision Trees (GBDTs), to perform pixel-wise segmentation of satellite images. The model is trained using a hand labelled dataset of ~12,000 individual pixels covering both the spatial and temporal domains of the SLSTR instrument and utilises the combined channels of the dual-view swaths. Pixel level annotations, while lacking spatial context, have the advantage of being cheaper to obtain compared to fully labelled images, a major problem in applying machine learning to remote sensing imagrey.

We validate the performance of our mask using cross validation and compare its performance with two baseline models provided in the SLSTR level 1 product. We show up to 10% improvement in binary classification accuracy compared with the baseline methods. Additionally, we show that our model has the ability to distinguish between different classes of cloud to reasonable accuracy.
On-line nano-solid phase extraction Fourier-transform ion cyclotron resonance mass spectrometry workflow to analyse soil solution organic matter gradients in the rhizosphere
Authors: Lohse Martin , Blaser Sebastian , Vetterlein Doris , Schlüter Steffen , Oburger Eva , Reemtsma Thorsten , Lechtenfeld Oliver
Published: March 2020

Plant-microbe interplay in the rhizosphere generates multi-faceted chemical gradients. The soil solution is a crucial component of the rhizosphere, where chemical gradients of organic molecules first develop upon growth of roots, introduction of plant-derived carbon and microbial turnover. Studying these gradients requires high resolution both in time and space as well as high chemical specificity to resolve the multitude of compounds. Existing methods to probe the rhizosphere soil solution were mostly limited to bulk chemical parameters, inorganic ions or targeted analysis of organic molecules. However, to decipher organic carbon turnover in the rhizosphere the characterization of the complex pool of soil solution organic matter is needed.

Here we present a novel method that combines time-resolved collection of soil solution samples via micro-suction cups in the rhizosphere with ultrahigh chemical resolution provided by Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) to unravel developing pattern of soil solution organic matter.

Zea mays plants were grown in soil columns for three weeks and soil solution samples of undisturbed root-soil system were collected once a week. Growth of the root system and hence position of sampling locations in relation to the distance from the root, were followed by X-ray computed tomography (X-ray CT).

The online sample preparation was optimised to extract and desalt the organic matter from a few microliters of soil solution. The downscaling to a nano-liquid chromatography system for the on-line extraction allowed the analysis of only minute amounts of organic carbon within the samples (down to 10 ng). Given the high background concentration of soil-derived organic carbon, the high mass resolution and sensitivity of FT-ICR-MS enabled to distinguish root derived molecules from soil organic matter based on their exact masses. Molecular formulas of the root derived molecules could be calculated showing distinct chemical characteristics as compared to the bulk soil solution. X-ray CT analyses enabled relating the results from the chemical analysis to distance from the root and root age. With increasing influence of the roots higher molecular masses and an increasing degree of oxygenation of the molecules could be observed.

Our method is thus capable to show the changing small scale pattern of soil solution organic matter during the early rhizosphere development, closing the knowledge gap between root exudates, soil chemistry and microbial processes.
Key Aspects for the Definition of On-site Inspection Challenging Environments
Authors: Kuang Feihong , Haquin Gerade Gustavo
Published: March 2020

On-site inspection (OSI) is an element of the verification regime of the Comprehensive Nuclear Test Ban Treaty (CTBT), with the sole purpose to clarify whether a nuclear weapon test explosion or any other nuclear explosion has been carried out in violation of the Treaty. An OSI could be launched in any environment where a triggering event occurred. A challenging environment may affect not only the signatures and observables of a nuclear explosion, but also the possibility to conduct the OSI. Harsh environmental conditions, such as extreme climate conditions, high vegetation coverage and complicated topographic characteristics, among others, could slow down the deployment of field missions, and affect the state-of-health of OSI equipment and even the performance of inspectors, thereby compromising the whole inspection. Thus, the operationalization of OSI in different environments is an important aspect in the development of OSI capability. In this respect, well defined OSI environment is an important step towards the development of comprehensive OSI capabilities. Based on the analysis of historical underground nuclear explosions data and knowledge on the environmental impact on observables, equipment and inspectors, a definition of OSI environment was developed. Climatic conditions were grouped into the main five groups of the Köppen-Geiger classification scheme. Vegetation coverage was re-grouped in four of the 16 classes of land coverage (not including water bodies) following the International Geosphere-Biosphere Programme. Complicated landforms grouped in topographic classification using a digital elevation model based on slope gradient, surface texture and local convexity within neighboring cells was used to classify topographic relief of four types of landforms for OSI. In this presentation, it is shown how these key environmental aspects will impact the conduct of an OSI.
Valuing climate services: experiences from the CLARA project
Authors: Delpiazzo Elisa , Bosello Francesco
Published: March 2020

This presentation aims to discuss some issues regarding the role of the economic evaluation of climate services in the context of the Horizon 2020 CLARA project.

CLARA provides 14 innovative services based on a co-development approach involving service producers and specific final users. In this context, the first issue is the role of the evaluation in the co-development framework. Our understanding suggests that it cannot be one of the last steps in the process, but a preliminary evaluation should be presented in the co-design of the service. For this reason, we advise the use of the “maximum likely value” as a signal for both developers and users. It derives from a comparison between the values of two alternative knowledge sources (i.e. one other than the climate service and the other as a 100% skill climate service). The “maximum likely value” provides a benchmark against which to compare the final product. It gives insights to the producer how to improve the service, while the final user has a direct and understandable measure of likely benefits from climate service adoption. This directly supports a higher engagement of the final user, whose participation is essential in developing the service as well as in gathering information for the evaluation.

Moreover, the final user’s participation has a strong impact in assessing how the services enter the decision- making process that is sometimes an obscure issue in the internal dynamic of the organizations. Recognizing a benefit stimulate the discussion on how the tool may be used internally. This sometimes leads to changes in the service design to meet better the users’ requirements. Another critical issue is the final user’s ability to translate into actions the signals of the climate services as well as to predict and quantify costs and benefits of actions based on climate services forecasts.

All these issues are discussed presenting examples from the CLARA project, especially from a set of services related to renewable energy production and water management.
The sabkhas of Qatar: modern analogues for studying early life on Earth and on Mars
Authors: Bontognali Tomaso , Blattmann Franziska , Al Disi Zulfa , Al Saad Al Kuwari Hamad , DiLoreto Zach , Dittrich Maria , Josset Jean-Luc , Kuhn Nikolaus , McKenzie Judith , Sadooni Fadhil , Williford Kenneth
Published: March 2020

The study of early life on Earth and the search for life on Mars often includes investigations of modern analogues: natural environments that share similarities to what we hypothesize may have existed on the early Earth and early Mars. The study of modern analogues provides key information on how biosignatures are formed and preserved, which is essential for interpreting the geological record. Research conducted in recent years in various modern sabkhas located along the coast of Qatar have demonstrated that these extreme evaporitic environments represent an inspirational gold mine for the field of geobiology and astrobiology.

The intertidal zones of the Qatari sabkhas are typically colonized by microbial mats. Their presence leads to the formation of Microbially Influenced Sedimentary Structures (MISS). Examples of studied MISS include polygonal, domical, blistered, tufted and crinkled microbial mats. We discuss biological vs. physiochemical factors responsible for their formation, as well as their fossilization potential. These MISS often occur in a precise sequence along a transect from the lower to the upper intertidal zone. We propose that a MISS sequence represents a stronger morphological biosignature than a single MISS. The community composition of some of the studied mats revealed an uppermost layer dominated by anoxygenic phototrophs. We propose that such mats represent a particularly good analogue for studying life in the Early Archean, a time when the cyanobacteria that usually dominate the uppermost photo-oxic layer of most modern mats probably did not exist.

Besides influencing sediment morphology, the extracellular polymeric substances (EPS) constituting the mats serve as nucleation sites for the precipitation of authigenic minerals. Among these possible precipitates, our research focused on microbially influenced Mg-rich carbonates and Mg-rich silicates. Linking these minerals to a microbial process is of particular interest in view of the forthcoming rover missions to Mars (i.e., ExoMars and Mars 2020). Indeed, orbital spectral analyses revealed the presence of Mg-rich clays and Mg-rich carbonates in the surroundings of the proposed landing sites. It will be exciting to test the hypothesis that, on Mars, some of these minerals may have formed at low temperatures from liquid water and may, therefore, represent a target phase for the investigation of biosignatures.
The function of carboxyls in the structure of humic acids to binding of organic substances
Authors: Smilek Jiri , Belusova Anna , Kalina Michal , Sedlacek Petr
Published: March 2020

The humic substances, the major and the most important part of soil organic matter, are responsible for the immobilization of organic compounds (e.g. heavy metal ions, organic dyes, surface active agents, etc.) in the soil. Unfortunately, there are a lot of gaps in the knowledge in the complex mechanism of binding of organic charged compounds by humic substances.

The unconventional diffusion and dialysis (transport) techniques have been developed for the purpose of study on the interactions between humic substances and organic charged substances.  In our contribution we are focusing on one fraction of humic substances – humic acids. The binding between humic acids with/without selectively blocking of carboxylic functional groups (methylation by –CH3) with organic charged compounds (e.g. organic dyes, surface active agents) has been studied by diffusion and dialysis approach using the spectroscopic techniques as analytical method. The strong impact of methylation on the positive affinity of humic acids towards organic compounds has been expected. These expectations were not confirmed by diffusion and dialysis techniques. The role of carboxyls in the structure of humic acids is not so essential as was expected and mentioned in the literature. The other effects (e.g. hydrophobic interactions, pi-pi stacking, etc.) are more important in the binding of organic compounds as was expected. The positive binding as well as kinetics of this process is also strongly depending on the physico-chemical circumstances of the system (e.g. pH, ionic strength, temperature, etc.).
Gullies on Mars and seasonal ices visualised using the Colour and Stereo Surface Imaging System (CaSSIS)
Authors: Conway Susan , Pommerol Antoine , Raack Jan , Philippe Meven , Mcewen Alfred , Thomas Nick , Cremonese Gabriele
Published: March 2020

Young gullies on Mars were first reported by Malin and Edgett in 2000 and were hailed as evidence of recent liquid water flows on Mars. Since that time, monitoring of gullies has revealed they are active today at times of year when the martian surface is at its coldest and when carbon dioxide ice is condensed on to the surface. In order to further explore the relationship between surface frosts and gully-activity we focus on Sisyphi Cavi near the south pole of Mars, where gully-activity has already been studied and CaSSIS obtained a dense temporal coverage in 2018. We identified the following sequence of events:

1) In winter frost covers all surfaces and dark spots and flows can be seen across the slopes with gullies and preferentially around the gully channels. This is consistent with previous observations and has been interpreted to be the surface expression of gas-jets generated by the sublimation of CO2 underneath a continuous slab of CO2 ice on the surface. The jets occur when the pressure fractures the slab ice and the pressurized gas can escape with entrained particles.

2) As the surface temperature increases towards 200 K, the top of the slopes are the first to defrost followed by sun facing parts of the alcoves and channels.

3) As the surface temperature approaches and exceeds 250 K and the surrounding terrain is completely defrosted, the last parts of the gully to remain frost covered are the fans. We interpret this to be a result of the fans having slightly lower thermal inertia than the surrounding materials. This lower thermal inertia could be because the fans have a lower content of water ice (i.e. a thicker lag on top of the ice-table), because of recent depositional events. It is at this time of year when gullies are most active. Hence, we infer that gully activity increases when there is both frosted and defrosted surfaces available to drive vigorous sublimation of the CO2 ice.

4) Finally, once defrosting has almost fully completed and surface temperatures have reached their seasonal maximum of ~270 K the only remaining surface frosts are in pole-facing niches at the base of gully-alcoves.

Our study has underlined that the colour capability of the CaSSIS instrument is particularly suited to studying and monitoring changes in surface ices. Our observations reveal that gully-alcoves defrost before the fans and gullies defrost later than surrounding terrain – suggesting activity is driven by the availability of “hot” sediment to trigger more efficient sublimation. Further work will examine whether surface frost patterns differ between gullies that have been shown to be active and inactive since spacecraft observations began.
Modelling impacts of climate change and alternative management interventions on the multi-functionality of agricultural landscapes in southern Africa
Authors: Roetter Reimund , Scheiter Simon , Hoffmann Munir , Ayisi Kwabena , Merante Paolo , Nelson William , Isselstein Johannes , Odhiambo Jude , Bracho Mujica Gennady , Taylor Peter , Twine Wayne , Erasmus Barend
Published: March 2020

On the background of increasing welfare and continued population growth, there is an ever-increasing pressure on land and other natural resources in many parts of the world. The situation is, however, particularly severe in the drylands of Sub-Saharan Africa. Southern African landscapes, composed of arable lands, tree orchards and rangelands, provide a range of important ecosystem functions. These functions are increasingly threatened by land use changes through competing claims on land by agriculture, tourism, mining and other sectors, and by environmental change, namely climate change and soil degradation. Among others, climate models project that drought risk in the region will increase considerably. Based on comprehensive data sets originating from previous groundwork by several collaborative projects on the functioning of these ecosystems, a number of biophysical and bio-economic models have been developed and evaluated. In the framework of the South African Limpopo Landscapes network (SALLnet) we have now refined and tailored these models for combined use for the assessment of changes in multiple functions of the prevailing agroecosystems when affected by alternative climate and land management scenarios - from field to regional scale. We apply vegetation models (such as aDGVM), crop models (such as APSIM) and integrative farm level models (e.g. agent-based) for different farming systems in conjunction with geo-referenced databases. Model outputs are combined to assess the impact of management x environment interactions on various ecosystem functions. Of special interest in our study are the ecosystem services related to the provision of food, feed and fuel, soil and water conservation, as well as recycling and restoring carbon and nutrients in soil. To illustrate how the combination of various modelling components can work in assessing management intervention effects under different environmental conditions on landscape level ecosystem services, a case study was defined in Limpopo province, South Africa. We investigated effects of current management practices and an intensification scenario over a longer period of years on soil organic carbon change under rangeland and arable land, potential erosion, productive water use, biomass production, monthly feed gaps, and rangeland habitat quality. Tentative results showed that sustainable intensification closed the livestock feed gap, but further reduced soil organic carbon. More generally, coupling the output of vegetation and crop models regionally calibrated with sound ground/ experimental data appears promising to provide meaningful insights into the highly complex interconnections of different ecosystem services at a landscape level.
Seasonal forecast of agricultural impacts of droughts in Mexico through a principal component regression based approach
Authors: Real-Rangel Roberto , Pedrozo-Acuña Adrián , Breña-Naranjo Agustín
Published: March 2020

Drought monitoring and forecasting allows to adopt mitigating actions in early stages of an event to reduce the vulnerability of a wide range of environmetal, economical and social sectors. In Mexico, various drought monitoring systems on national and regional scale perform a follow up of these events, such as the Drought Monitor in Mexico, and the North American Drought Monitor, but seasonal drought forecasting is still a pending task. This study aims at fill this gap applying a methodology that uses data derived from a globally available atmospheric reanalysis product and a principal component regression based model oriented to predict drought impacts in rainfed crops associated to deficits in the soil moisture, estimated by means of the standardized soil moisture index (SSI). Using the state of Guanajuato (Center-North of Mexico) as a study case, the model generated yielded RSME values of 0.74 using regional and global hydrological, climatic and atmospheric variables as predictors with a lead-time of 4 months.
Constraining ice core chronologies with 39Ar and 81Kr
Authors: Ritterbusch Florian , Chu Yan-Qing , Crotti Ilaria , Dong Xi-Ze , Gu Ji-Qiang , Hu Shui-Ming , Jiang Wei , Landais Amaelle , Lipenkov Volodya , Lu Zheng-Tian , Shao Lili , Stenni Barbara , Team Taldice , Tian Lide , Tong A-Min , Wang Wen-Hao , Zhao Lei
Published: March 2020

Paleoclimate reconstructions from ice core records can be hampered due to the lack of a reliable chronology, especially when the stratigraphy is disturbed and conventional dating methods are not readily applied. The noble gas radioisotopes 81Kr and 39Ar can in these cases provide robust constraints as they yield absolute, radiometric ages. 81Kr (half-life 229 ka) covers the time span from 50-1300 ka, which is particularly relevant for polar ice cores, whereas 39Ar (half-life 269 a) with a dating range of 50-1400 a is suitable for high mountain glaciers. For a long time the use of 81Kr and 39Ar for dating of ice samples was hampered by the lack of a detection technique that can meet its extremely small abundance at a reasonable sample size. Here, we report on 81Kr and 39Ar dating of Antarctic and Tibetan ice cores with the detection method Atom Trap Trace Analysis (ATTA), using 5-10 kg of ice for 81Kr and 2-5 kg for 39Ar. Among others, we measured 81Kr in the lower section of Taldice ice core, which is difficult to date by conventional methods, and in the meteoric bottom of the Vostok ice core in comparison with an age scale derived from hydrate growth. Moreover, we have obtained an 39Ar profile for an ice core from central Tibet in combination with a timescale constructed by layer counting. The presented studies demonstrate how the obtained 81Kr and 39Ar ages can complement other methods in developing an ice core chronology, especially for the bottom part.

[1] Z.-T. Lu, Tracer applications of noble gas radionuclides in the geosciences, Earth-Science Reviews 138, 196-214, (2014)

[2] C. Buizert, Radiometric 81Kr dating identifies 120,000-year-old ice at Taylor Glacier, Antarctica, Proceedings of the National Academy of Sciences, 111, 6876, (2014)

[3] L. Tian, 81Kr Dating at the Guliya Ice Cap, Tibetan Plateau, Geophysical Research Letters, (2019)

[4] http://atta.ustc.edu.cn
Estimation of wave induced sediment resuspension using an ADV
Authors: Fleit Gábor , Baranya Sándor
Published: March 2020

The ever-increasing demand for fluvial navigation and the more and more efforts made for ecologically sustainable water usage (facilitated by e.g. the Water Framework Directive of the EU) have highlighted potential conflicts of interests in river management. Riverine traffic has notable hydrodynamic effects, i.e. the local hydraulic regime of river reaches may get significantly altered by wave events generated by passing vessels. As ship waves reach the shallower areas, the related hydrodynamic stresses affect the near-bed boundary layer increasingly, bed shear stress increases gradually, leading to the resuspension of fine sediments. In order to find out more about the nature of this phenomenon, simultaneous ABS (acoustic backscatter sensor) and ADV (acoustic Doppler velocimeter) measurement were performed in the Hungarian Danube. Such measurement not only offer the opportunity to reveal the likely interconnections between hydrodynamic variables (e.g. flow velocity, turbulent kinetic energy) and suspended sediment concentrations (SSC), but the found correlation between ABS data and the backscatter strength of the ADV also suggests the applicability of the latter for the estimation of instantaneous SSC in a high temporal resolution.
Modeling the X-ray emissions from the geo-space environment
Authors: Sun Tianran
Published: March 2020

The Earth's magnetosheath is luminous in the soft X-ray band, due to the solar wind charge exchange (SWCX) process. SWCX occurs when a heavy solar wind ion with a high charge state encounters with a neutral component. The heavy ion obtains an electron and gets into an excited state. It then decays to the ground state and emits a photon in the soft X-ray band. Considering that the X-ray emission from the magnetosheath is higher compared to that from the magnetosphere, information about the boundary positions can be derived from an X-ray image of the magnetosheath.

 

The solar wind - magnetosphere - ionosphere link explorer (SMILE) is a mission jointly supported by ESA and CAS, which aims at exploring the dynamics in the whole system. Soft X-ray Imager (SXI) is expected to provide X-ray images of the magnetosphere. The Modeling Working Group (MWG) is one of the four working groups of SMILE. Studies about the modeling of X-ray emissions as well as the method to derive the boundary positions are two main topics of the MWG. The main progress of MWG will be summarized here. 
A paleoclimatic perspective of triple oxygen isotopes from gypsum in Holocene Thar Desert playa lakes
Authors: Giesche Alena , Dixit Yama , Gázquez Fernando , Bauska Thomas , Brady Matthew , Singh Vikas K. , Singh Ravindra N. , Petrie Cameron A. , Hodell David A.
Published: March 2020

The Thar Desert (NW India) has numerous evaporative saline playa lakes. Some are still active and others are dry and preserve up to several meters of sedimentary deposits. These deposits feature a variety of evaporite minerals, including the hydrated mineral gypsum (CaSO4 2H2O). Assuming no secondary exchange, the isotopic composition of the gypsum hydration water preserves the δ18O, δ17O and δ D of palaeolake water at the time of gypsum formation. This method provides a way to understand the hydrologic balance in a part of the world where it is typically very difficult to obtain palaeoclimate records. Our 36-hour pan evaporation experiment on site shows that triple oxygen isotopes track changes in evaporative conditions, which vary diurnally due to fluctuating temperature and relative humidity, and appear to reflect night-time condensation. We present new palaeohydrological records from two dry playas (Karsandi, Khajuwala) and one active playa (Lunkaransar) in the Thar Desert using the triple oxygen and hydrogen isotopic composition of gypsum hydration water. Results show that a source of water maintained active playa lake basins in the central Thar Desert for much of the Holocene, either by enhanced direct precipitation and/or fluvial sources. The derived 17O-excess and d-excess data potentially enable modelling of past changes in relative humidity, once other parameters (windiness, evaporation/inflow, etc.) are set.
Spatial distribution of geomorphic changes after an extreme flash-flood compared with hydrological and sediment connectivity
Authors: Calvo-Cases Adolfo , Gago Jorge , Ruiz-Pérez Maurici , García-Comendador Julián , Fortesa Josep , Company Jaume , Nácher-Rodríguez Beatriz , J. Vallés-Morán Francisco , Estrany Joan
Published: March 2020

An extraordinary flash-flood event occurred the 9th October 2018 in the north-eastern part of Mallorca Island. The spatial distribution of main geomorphic changes were accurately mapped through field and aerial UAV campaigns in two contrasted small headwater catchments (i.e., < 2 km2) of the Begura de Saumà River. The first one was massively covered by step terraces over Lias limestone, whilst the second one was only covered by check-dam terraces over Miocene marls.

Two weeks after the event, a UAV was used to record aerial photographs and build high-resolution digital elevation models (HR-DEM; i.e., 5 cm). Geomorphic changes were assessed comparing this HR-DEM with LiDAR-derived DEM (i.e., 25 cm resolution) obtained in 2014. The Borselli index of connectivity (IC; version of Cavalli et al., 2013) was calculated from the LiDAR-derived DEM to compare the geomorphic changes triggered by the flash-flood with the structural sediment connectivity distribution.

At hillslope scale, the HR-DEM allowed the identification of geomorphic changes, such as the initiation of rills and the wall collapse of old agricultural terraces in the terraced limestone catchment. In the main headwater valley axis of the marls catchment, where natural streams had been historically reduced and deviated with the construction of check-dam terraces, huge geomorphic changes enabled the recovering of natural streams.

The spatial distribution of the observed geomorphic changes on hillslopes was compared with the spatial patterns of sediment connectivity. Geomorphic changes elucidated a good concordance with structural connectivity, both in the location and magnitude. The analysis of these concordances and some discordances allows the identification of hydrogeomorphological factors triggering the erosional response of hillslopes.

This work was supported by the research project CGL2017-88200-R “Functional hydrological and sediment connectivity at Mediterranean catchments: global change scenarios –MEDhyCON2” funded by the Spanish Ministry of Science, Innovation and Universities, the Spanish Agency of Research (AEI) and the European Regional Development Funds (ERDF).
UV-Indien Network- a network dedicated to the long-term monitoring of UV radiation in the Indian Ocean.
Authors: Portafaix Thierry , Lamy Kevin , Forestier Jean-Baptiste , Rakotoniaina Solofo , Amélie Vincent
Published: March 2020

Radiation (UV) is one of the main components of solar radiation transmitted by the Earth's atmosphere. Exposure to UV radiation can have both positive and negative effects on the biosphere and humans in particular. Overexposure significantly increases the risk of skin cancer and eye problems.

Ozone, cloud cover and zenithal solar angle are the main parameters affecting UV radiation levels at the surface. Stratospheric ozone in particular strongly absorbs UV radiation. A dense cloud cover absorbs UV radiation, while a split cloud cover may tend to amplify it.

Although the stratospheric ozone layer is showing signs of recovery from reduced ozone-depleting substances. The impact of greenhouse gases on the climate is still in increase and global climate models anticipate an acceleration in Brewer-Dobson Circulation, which would lead to lower ozone levels in the tropics. Butler et al. (2016) estimate a decrease in stratospheric ozone in the tropics of 5 to 10 DU for all climate scenarios. Some recent projections (Lamy et al., 2019) predict a 2-3% increase in UVR in the southern tropical band, a region where UV levels are already extreme.

The purpose of the UV-Indien network is to :

- Monitor UV levels at different sites in the Western Indian Ocean (WIO)

- Describe the annual and inter-annual variability of UV radiation in the WIO

- Perform regional climate projections of UV radiations, validated by quality ground measurements.

UV-Indien is split into three phases. The first phase began in 2016, with the deployment of the first measurement sites (Reunion Island, Madagascar, Seychelles, Rodrigues). These sites are equipped with a broadband radiometer measuring the UVI and a camera estimating the coverage and sometimes a spectrometer for the measurement of total ozone. The second phase from 2019, sees the extension of this network to 4 other sites (Juan de Nova, Diego Suarez, Fort Dauphin and Grande Comoros). The data validation phase began in 2019 (comparative study with satellite data) and will also propose the study of the variability of UV radiation on different sites. Finally, climate projections will be made from 2020 onwards and will use data from the network to validate the results.

The aim of this communication is to describe the entire network and its objectives. The first results, as well as the first climatologies will also be discussed.