bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of fracture connectivity on Rayleigh wave velocity dispersion
Authors: Quiroga Gabriel , Rubino J. Germán , Solazzi Santiago , Barbosa Nicolás , Holliger Klaus
Published: March 2020

The use of passive seismic techniques to monitor geothermal reservoirs allows to assess the risks associated with their exploitation and stimulation. One key characteristic of geothermal reservoirs is the degree of fracture connectivity and its evolution. The reason for this is that changes in the interconnectivity of the prevailing fractures affect the permeability and, thus, the productivity of the system. An increasing number of studies indicates that the Rayleigh wave velocity can be sensitive to changes in the mechanical and hydraulic properties of geothermal reservoirs. In this work, we explore the effects of fracture connectivity on Rayleigh wave velocity dispersion accounting for wave-induced fluid pressure diffusion effects. To this end, we consider a 1D layered model consisting of a surficial sandstone formation overlying a fractured and water-saturated granitic layer, which, in turn, is underlain by a compact granitic half-space. For the stochastic fracture network prevailing in the upper granitic layer, we consider varying levels of fracture connectivity, ranging from entirely unconnected to fully interconnected. We use an upscaling approach based on Biot’s poroelasticity theory to determine the effective properties associated with these scenarios. This procedure allows to obtain the frequency-dependent seismic body wave velocities accounting for fluid pressure diffusion effects. Finally, using these parameters, we compute the corresponding Rayleigh wave velocity dispersion. Our results show that Rayleigh wave phase and group velocities exhibit a significant sensitivity to the degree of fracture connectivity, which is mainly due to a reduction of the stiffening effect of the fluid residing in connected fractures in response to wave-induced fluid pressure diffusion. This suggests that time-lapse observations of Rayleigh wave velocity changes, which so far are commonly associated with changes in the fracture density, could also be related to changes in the interconnectivity of pre-existing fractures.
Two-sided turbulent boundary layer parameterizations for assessing ocean – atmosphere fluxes
Authors: Lemarie Florian , Pelletier Charles , Brilouet Pierre-Etienne , Blayo Eric , Redelsperger Jean-Luc , Bouin Marie-Noëlle
Published: March 2020

Standard methods for determining air – sea fluxes typically rely on bulk algorithms derived from the Monin-Obukhov stability theory (MOST), using ocean surface fields and atmosphere near-surface fields. In the context of coupled ocean – atmosphere simulations, the shallowest ocean vertical level is usually assimilated to the surface, and the turbulent closure is one-sided: it aims at extrapolating atmosphere near-surface solution profiles (for wind speed, temperature and humidity) to the prescribed ocean surface values. Assimilating near-surface ocean fields as surface ones is equivalent to considering that in the ocean surface layer, solution profiles are constant instead of also being determined by a turbulent closure. Here we introduce a method for extending existing turbulent parameterizations to a two-sided context, by including the ocean surface layer and the viscous sublayers, which are also generally neglected in standard air – sea fluxes computation. The formalism we use for this method is derived from that of classical turbulent closure, so that our novelties can easily be implemented within existing formulations. Special care is taken to ensure the smoothness of resulting solution profiles. We investigate the impact of such two-sided bulk formulations on air - sea fluxes and discuss further implications such as resulting bulk formulation retuning. We also present leads on incorporating other mechanisms impacting air – sea fluxes within our framework, such as waves and radiation penetration.
The applicability of analytical elasto-plastic solutions and issues of the formation of shear bands zones
Authors: Grishko Elena , Myasnikov Artyom , Sabitov Denis , Podladchikov Yuri , Garavand Aboozar
Published: March 2020

Key Words: numerical modelling, elasto-plastic analytical solutions, shear bands, geomechanics.

The correct analysis of wellbore stability in unconventional reservoirs receives much interest from the industry as shale rock and tar sands demonstrate perceptible plastic behavior which influences the estimation of rock failure. To tackle this problem the 3D finite element code has been developed for computing the stress-strain state in the elastoplastic medium near a borehole. The accuracy of the results, obtained due to the application of the finite element technique, can be affected by various numerical effects. Since the theory of plasticity assumes infinitesimal load increments, errors associated with finite increments are almost inevitable. The accuracy of the numerical solution can be verified by comparing the numerical results with the analytical solutions. Elasto-plastic analytical solutions [1], [2] stand out among others because they are the only ones among many others, mentioned in the cited monographs, that consider analytical solutions under conditions of non-hydrostatic loading.

In this study, the numerical and analytical solutions were verified and relative errors were calculated for different loading paths. It turned out, for example, that Galin’s analytical solution works well not only in the field of its applicability, but also outside of it, despite different errors. This work discusses questions related to the influence of the increment of the applied load on the structure of a stationary elasto-plastic solution, including in the case of the formation of zones of localized plastic deformation. The issue of the appearance of shear bands zones is also considered: these bands develop directly around the hole under certain boundary conditions or gradually grow out of the zones of elliptical plastic deformation.

The first, third and fifth authors acknowledge support of research by Geosteering technologies company within the scope of Geonaft project sponsored by Skolkovo foundation, Russia.

The second and fourth authors acknowledge support of research by Government of Russian Federation under grant 2019-220-07-9139.

REFERENCES

[1] Detournay, E. (1986). An approximate statical solution of the elastoplastic interface for the problem of Galin with a cohesive-frictional material. International Journal of Solids and Structures, 22(12), 1435–1454.

[2] Galin, L.A. (1946). Plane elastoplastic problem. Applied Mathematics and Mechanics, 10 (3), 365–386.
Fe(II)-catalyzed transformation of Fe (hydr)oxides in particle-size soil organic matter fractions from amended agricultural soils
Authors: Giannetta Beatrice , Balint Ramona , Said-Pullicino Daniel , Plaza César , Martin Maria , Zaccone Claudio
Published: March 2020

Redox-driven changes in Fe crystallinity and speciation may affect soil organic matter (SOM) stabilization and carbon (C) turnover, with consequent influence on global terrestrial soil organic carbon (SOC) cycling. Under reducing conditions, increasing concentrations of Fe(II) released in solution from the reductive dissolution of Fe (hydr)oxides may accelerate ferrihydrite transformation, although our understanding of the influence of SOM on these transformations is still lacking. 

Here, we evaluated abiotic Fe(II)-catalyzed mineralogical changes in Fe (hydr)oxides in bulk soils and size-fractionated SOM pools (for comparison, fine silt plus clay, FSi+Cl, and fine sand, FSa) of an agricultural soil, unamended or amended with biochar, municipal solid waste compost, and a combination of both. 

FSa fractions showed the most significant Fe(II)-catalyzed ferrihydrite transformations with the consequent production of well-ordered Fe oxides irrespective of soil amendment, with the only exception being the compost-amended soils. In contrast, poorly crystalline ferrihydrite still constituted ca. 45% of the FSi+Cl fractions of amended soils, confirming the that the higher SOM content in this fraction inhibits atom exchange between aqueous Fe(II) and the solid phase. Building on our knowledge of Fe(II)-catalyzed mineralogical changes in simple systems, our results evidenced that the mechanisms of abiotic Fe mineral transformations in bulk soils depend on Fe mineralogy, organic C content and quality, and organo-mineral associations that exist across particle-size SOM pools. Our results underline that in the fine fractions the increase in SOM due to organic amendments can contribute to limiting abiotic Fe(II)-catalyzed ferrihydrite transformation, while coarser particle-size fractions represent an understudied pool of SOM subjected to Fe mineral transformations. 
Spectrally resolved OLR from IASI measurements
Authors: Whitburn Simon , Clarisse Lieven , Bauduin Sophie , Dewitte Steven , George Maya , Safieddine Sarah , Hurtmans Daniel , Coheur Pierre-François , Clerbaux Cathy
Published: March 2020

The Earth’s Outgoing Longwave Radiation (OLR) is a key component in the study of climate feedbacks and processes. As part of the Earth’s radiation budget, it reflects how the Earth-atmosphere system compensates the incoming solar radiation at the top of the atmosphere. It can be retrieved from the radiance intensities measured by satellite sounders and integrated over all the zenith angles of observation. Since satellite instruments generally acquire the radiance at a limited number of viewing angle directions and because the radiance field is not isotropic, the conversion is however not straightforward. This problem is usually overcome by the use of empirical angular distribution models (ADMs) developed for different scene types that directly link the directional radiance measurement to the corresponding OLR.

OLR estimates from dedicated broadband instruments are available since the mid-1970s; however, such instruments only provide an integrated OLR estimate over a broad spectral range. They are therefore not well suited for tracking separately the impact of the different parameters affecting the OLR (including greenhouse gases), making it difficult to track down deficiencies in climate models. Currently, several hyperspectral instruments in space acquire radiances in the thermal infrared spectral range, and in principle, these should allow to better constrain the OLR. However, as these instruments were not specifically designed to measure the OLR, there are several challenges to overcome. Here we propose a new retrieval algorithm for the estimation of the spectrally resolved OLR from measurements made by the IASI sounder on board the Metop satellites. It is based on a set of spectrally resolved ADMs developed from synthetic spectra for a large selection of scene types associated with different states of the atmosphere and the surface. Atmospheric and surface parameters are derived from the Copernicus Atmosphere Monitoring Service (CAMS) reanalysis dataset and selected using a dissimilarity-based subset selection algorithm. These spectral ADMs are then used to convert the measured IASI radiances into spectral OLR.

We then evaluate how the IASI OLR compare with the CERES and the AIRS integrated and spectral OLR. We analyze the interannual variations in OLR over 10 years of IASI measurements for selected spectral channels using EOF analysis and we connect them with well-known climate phenomena such as El Niño-Southern Oscillation (ENSO), the Pacific Decadal Oscillation (PDO), the Atlantic Multidecadal Oscillation (AMO).
Providing a user-friendly outlier analysis service implemented as open REST API
Authors: Goldfarb Doron , Kobler Johannes , Peterseil Johannes
Published: March 2020

As outliers in any data set may have detrimental effects on further scientific analysis, the measurement of any environmental parameter and the detection of outliers within these data are closely linked. However, outlier analysis is complicated, as the definition of an outlier is controversially discussed and thus - until now - vague. Nonetheless, multiple methods have been implemented to detect outliers in data sets. The application of these methods often requires some statistical know-how.

The present use case, developed as proof-of-concept implementation within the EOSC-Hub project, is dedicated to providing a user-friendly outlier analysis web-service via an open REST API processing environmental data either provided via Sensor Observation Service (SOS) or stored as data files in a cloud-based data repository. It is driven by an R-script performing the different operation steps consisting of data retrieval,  outlier analysis and final data export. To cope with the vague definition of an outlier, the outlier analysis step applies numerous statistical methods implemented in various R-packages.

The web-service encapsulates the R-script behind a REST API which is decribed by a dedicated OpenAPI specification defining two distinct access methods (i.e. SOS- and file-based) and the required parameters to run the R-script. This formal specification is subsequently used to automatically generate a server stub based on the Python FLASK framework which is customized to execute the R-script on the server whenever an appropriate web request arrives. The output is currently collected in a ZIP file which is returned after each successful web request. The service prototype is designed to be operated using generic resources provided by the European Open Science Cloud (EOSC) and the European Grid Initiative (EGI) in order to ensure sustainability and scalability.

Due to its user-friendliness and open availability, the presented web-service will facilitate access to standardized and scientifically-based outlier analysis methods not only for individual scientists but also for networks and research infrastructures like eLTER. It will thus contribute to the standardization of quality control procedures for data provision in distributed networks of data providers.

 

Keywords: quality assessment, outlier detection, web service, REST-API, eLTER, EOSC, EGI, EOSC-Hub
Exploring continuous time series of vegetation hyperspectral reflectance and solar-induced fluorescence through radiative transfer model inversion
Authors: Celesti Marco , Biriukova Khelvi , Campbell Petya K. E. , Cesana Ilaria , Cogliati Sergio , Damm Alexander , Drusch Matthias , Julitta Tommaso , Middleton Elizabeth , Migliavacca Mirco , Miglietta Franco , Panigada Cinzia , Rascher Uwe , Rossini Micol , Schuettemeyer Dirk , Tagliabue Giulia , van der Tol Christiaan , Verrelst Jochem , Yang Peiqi , Colombo Roberto
Published: March 2020

Remote sensing of solar-induced chlorophyll fluorescence (SIF) is of growing interest for the scientific community due to the inherent link of SIF with vegetation photosynthetic activity. An increasing number of in situ and airborne fluorescence spectrometers has been deployed worldwide to advance the understanding and usage of SIF for ecosystem studies. Particularly, a number of sites has been instrumented with the FloX (J&B Hyperspectral Devices, Germany), an automated instrument that houses two high resolution spectrometers covering the visible and near infrared spectral regions, one specifically optimized for fluorescence retrieval, the other for plant trait estimation.

In this contribution we explore the feasibility to consistently retrieve plant traits and SIF from canopy level FloX measurements through the numerical inversion of a light version of the SCOPE model. The optimization approach was specifically adapted to work with the high- frequency time series produced by the FloX. In this context, a strategy for optimal retrieval of plant traits at daily scale is discussed, together with the implementation of an emulator of the radiative transfer model in the retrieval scheme. The retrieval strategy was applied to site measurements across Europe and the US that span a variety of natural and agricultural ecosystems.

The full spectrum of canopy SIF, the fluorescence quantum efficiency, and main plant traits controlling light absorption and reabsorption were retrieved concurrently and evaluated over the growing season in comparison with site-specific ancillary data. Improvements and challenges of this method compared to other retrievals are discussed, together with the potential of applying a similar retrieval scheme to airborne datasets acquired with e.g. the HyPlant sensor, or the reconfigured “FLEX mode” data acquired with the recently launched Sentinel-3B during its commissioning phase.
Air quality modelling studies in Germany and Europe across scales
Authors: Barra Marc , Fallmann Joachim , Tost Holger
Published: March 2020

The problem of health risks associated with poor air quality in cities and metropolitan areas is rising in the perception of society. In order to improve air quality, a thorough understanding of different emission sources concerning transport, origin and composition as well as the microphysical and chemical processes involved is of crucial importance.

To assess air quality related issues, we set up a simulation system using the global to regional model system MECO(n), which allows entangling of chemical and physical interactions using a dynamical coupling approach from a global to regional domains down to a resolution of ∼7km. This provides us with a detailed picture of air quality in urbanised regions whilst maintaining a consistent representation and implementation of processes across the scales.

The model setup is evaluated using measurement data from the aerosol robotic network (AERONET) and satellite data from VIIRS instrument on board the polarorbiting Suomi NPP satellite. Moreover we compare our model to ground based measurements of gas species and particulate matter, which are taken from the databases of the Environmental Protection Agency of Rhineland-Palatinate. In this context the limits of the model with respect to aerosol processes especially in the boundary layer are discussed and the resulting limitations in comparing our model output to ground based measurements of particulate matter, specifically PM2.5 and PM10 are shown.

To demonstrate the flexibility of the model system two model applications relevant for air pollution issues in the Rhine-Main region are presented. The first investigates the direct influence of a localised reduction in anthropogenic emissions on the surrounding regions and the reducing region itself. The second explores deposition regions of kerosene, which is released by aircrafts during emergency fuel dumping event.
3D modelling of a mineral deposit using drill core hyperspectral data
Authors: De La Rosa Roberto , Khodadadzadeh Mahdi , Contreras Cecilia , Tusa Laura , Kirsch Moritz , Tolosana-Delgado Raimon , Gloaguen Richard
Published: March 2020

Drill core samples have been traditionally used by the mining industry to make resource estimations and to build geological models. The hyperspectral drill core scanning has become a popular tool in mineral exploration because it provides a non-destructive method to rapidly characterise structural features, alteration patterns and rock mineralogy in a cost effective way.

Typically, the hyperspectral sensors cover a wide spectral range from visible and near-infrared (VNIR) to short and long wave infrared (SWIR and LWIR). The spectral features in this range will help to characterize a large number of mineral phases and complement the traditional core logging techniques. The hyperspectral core scanning provide mineralogical information in a millimetre scale for the entire borehole, which fills the gap between the microscopic scale of some of the laboratory analytical methods or the sparse chemical assays and the meter scale from the lithological descriptions.

However, applying this technique to the core samples of an entire ore deposit results in big datasets. Therefore, there is the need of a workflow to build a 3D geological model conditioned by the data applying suitable data reduction methods and appropriate interpolation techniques.

This contribution presents a case study in the combination of traditional core logging and hyperspectral core logging for geological modelling. To attain mineral and alteration maps from the hyperspectral data, unsupervised classification techniques were applied generating a categorical data set. The amount of data was reduced by the application of a domain generation algorithm based on the hyperspectral information. The domain generated by the algorithm is a compositional categorical data set that was then fed to condition the application of stochastic Plurigaussian simulations in the construction of 3D models of geological domains. This technique allows to simulate the spatial distribution of the hyperspectral derived categories, to make a resource estimation and to calculate its associated uncertainty.
Addressing uncertainty, multiple objectives, and adaptation in DICE: Can dynamic planning shed new light on the decision-making process?
Authors: Carlino Angelo , Marangoni Giacomo , Tavoni Massimo , Castelletti Andrea
Published: March 2020

Integrated assessment models are often criticized because of: i) the simplified treatment of the severe uncertainties involved, ii) the strong dependency on the difficult quantification of future climate damages and iii) their implicit description of adaptation strategies.
We propose a novel approach to tackle these three issues by coupling a closed loop control strategy and an updated AD-DICE (ADaptation - Dynamic Integrated Climate-Economy) model. First, we model explicitly uncertain parametrization and stochastic processes for climate sensitivity, atmospheric temperature, population, productivity, and carbon intensity. We then ensure an adaptive response to the uncertainties by implementing a closed-loop control system where we condition the decision variables on state observation. This leads to an improvement with respect to the traditional static optimization approach. Second, we propose a multi-objective formulation of the optimization problem traditionally solved by DICE in order to separate temperature targets from economic objectives. This allows us to be less dependent on the climate damages quantification while studying the tradeoffs to find compromise solutions. Third, we include an explicit description of adaptation strategies introducing stock and flow adaptation investments as additional decision variables. Thanks to this last modification, we can also thoroughly analyze the tradeoffs between mitigation and adaptation.
Results show that the proposed method outperforms traditional static optimization both in single-objective and multi-objectives contexts. Moreover, we confirm the absolute need for fast and strong mitigation since we observe that the tradeoff between temperature and economic objectives is strongly reduced under uncertainty and when considering adaptation. On the other hand, different adaptation strategies correspond to a different balance of present value damages and economic objectives. By making explicit this tradeoff between two socio-economic objectives, results reveal the political nature of the choice over climate adaptation strategies.
Coupling an individual-based boreal forest model with a permafrost land-surface model to forecast biomass development in boreal larch forests at the Siberian treeline
Authors: Stünzi Simone , Kruse Stefan , Boike Julia , Herzschuh Ulrike , Langer Moritz
Published: March 2020

The fate of boreal forests under global warming and forced rapid environmental changes is still highly uncertain, in terms of remaining a carbon sink or becoming a future carbon source. Forest dynamics and resulting ecosystem services are strongly interlinked in the vast permafrost-covered regions of the Siberian treeline ecotone. Consequently, understanding the role of current and future active layer dynamics is crucial for the prediction of aboveground biomass and thus carbon stock developments.

We present a coupled model version combining CryoGrid, a sophisticated one-dimensional permafrost land surface model adapted for the use in forest ecosystems, with LAVESI, a detailed, individual-based and spatially explicit larch forest model. Subsequently, parameterizing against an extensive field data set of >100 forest inventories conducted along the treeline of larch-dominated boreal forests in Siberia (97-169° E), we run simulations covering the upcoming decades under contrasting climatic change scenarios.

The model setup can reproduce the energy transfer and thermal regime in permafrost ground as well as the radiation budget, nitrogen and photosynthetic profiles, canopy turbulence and leaf fluxes and predict the expected establishment, die-off and treeline movements of larch forests. Our results will show vegetation and permafrost dynamics, quantify the magnitudes of different feedback processes between permafrost, vegetation, and climate and reveal their impact on carbon stocks in Northern Siberia.
High-speed UV imaging of elves and lightning from space: first simultaneous detections from the Mini-EUSO and ASIM instruments
Authors: Battisti Matteo , Arnone Enrico , Bertaina Mario , Casolino Marco , Chanrion Olivier , Fuglesang Christer , Neubert Torsten ,   Mini-EUSO team for the JEM-EUSO collaboration
Published: March 2020

The search for the physical mechanisms of lightning, transient luminous events and terrestrial gamma-ray flashes is receiving an extraordinary support by new space observations that have recently become available. Next to lightning detectors on geostationary satellites, new low orbit experiments are giving an unprecedented insight in the very source of these processes. Looking at the physics behind these new observations requires however to have a variety of different instruments covering the same event, and this is proving extremely challenging. Here, we present observations of UV emissions of elves and lightning taken for the first time simultaneously from the two instruments Mini-EUSO and ASIM operating on the international space station. Mini-EUSO was designed to perform observations of the UV-light night emission from Earth. It is a wide field of view telescope (44°x44° square FOV) installed for the first time on October 2019 inside the Zvezda Module of the ISS, looking nadir through a UV transparent window. Its optical system consists of two Fresnel lenses for light collection. The light is focused onto an array of 36 multi-anode photomultiplier tubes (MAPMT), for a total of 2304 pixels. Each pixel has a footprint on ground of ~5.5 km. The instrument is capable of single-photon counting on three different timescales: a 2.5 microsecond (D1) and a 320 microsecond (D2) timescale with a dedicated trigger system, and a 40.96ms timescale (D3) used to produce a continuous monitoring of the UV emission from the Earth. ASIM is an experiment dedicated to lightning and atmospheric processes. Its Modular Multispectral Imaging Array (MMIA) is made of an array of 3 high speed photometers probing different wavelength sampling at rates up to 100 kHz, and 2 Electron Multiplication Charge Coupled Devices (EM-CCDs) with a sub-km spatial resolution with an 80° FOV and recording up to 12 frames per second. Mini-EUSO detected several bright atmospheric events like lightning and elves, with a few km spatial resolution and different time resolutions, probing therefore different stages of the electromagnetic phenomena. Observations from Mini-EUSO were simultaneously captured by ASIM instruments, allowing for the first time to compare and complement the capabilities of the two instruments with a time inter-calibration based on unambiguous series of lightning detections.
Verification of the Storm surge Forecasting System for the Korean Coastal Area
Authors: La Nary , An Byoung Woong , Kang KiRyong , Oh Sang Myeong , Kim YoonJae
Published: March 2020

In recent years, coastal disasters have been frequently caused by typhoons and storm surges accompanied by high waves due to global warming and the changing marine environment. In addition, the development of coastal areas in Korea has also led to suffering great damage to society every year. 

To cope with this issue, we have developed a new storm-surge prediction system based on the NEMO model for improving the predictability both the tide and the surge. This new regional tide-surge prediction system (RTSM) is constructed with a two-dimensional barotropic sigma coordinates and has a 1/12 degrees horizontal resolution. To find optimal coefficients of this model, several sensitivity experiments were conducted and verified with tide gauge measurements from the KHOA (Korea Hydrographic and Oceanographic Agency). Finally, we selected a bathymetry from SRTM (Shuttle Radar Topography Mission), Charnock coefficient as a constant value of 0.275 and the reference pressure for the inverse barometric effect as the domain mean. As the result of comparing surge-height predictions with the currently operating model (OPER-RTSM), the new system (RTSM) showed roughly 30% higher in forecast accuracy than the previous OPER-RTSM.
High-resolution spatiotemporal heterogeneities of water optical properties in a large lake to infer physical and biogeochemical drivers of primary production
Authors: Minaudo Camille , Odermatt Daniel , Fernandez-Castro Bieito , Chmiel Hannah E. , Lavanchy Sébastien , Bouffard Damien , Wüest Johny Alfred
Published: March 2020

Measuring primary production (PP) is of major importance to evaluate how lakes are recovering from eutrophication, and better constrain their role in global biogeochemical cycles. The classical sampling method involving radiolabelled carbon incubated in bottles at selected depths is associated with heavy logistics and prevents scientists from sampling the short-term dynamics of PP. Therefore, we investigate alternative methods based on oxygen sensors and optical properties.

To explore the interplay between biogeochemical and physical processes and how they are related to PP in large lakes, we have deployed since October 2018 a sophisticated autonomous profiler in Lake Geneva, Switzerland. The so-called Thetis profiler measures with a centimeter resolution backscattering and fluorescence at discrete wavelengths, hyperspectral absorption and attenuation, hyperspectral reflectance, along with temperature, dissolved oxygen and conductivity. The profiler was deployed over contrasted seasons and recorded these parameters every three hours over the top 50 m of the water column.

Observations revealed large spatiotemporal heterogeneities of optical properties as a result of seasonal and short-term (weekly to sub-daily) physical and biogeochemical processes. Diel cycles in the optical properties representing phytoplankton abundance resulted from night-time convection and grazing and production during the day. Short-lived but strong upwelling events triggered sudden disruptive shifts in the phytoplankton community composition over the fall to winter transition period which, in turn, impacted the oxygen budgets, opening the door to a better understanding of the vertical heterogeneity of PP directly from inherent optical properties. The data also features advected riverine and resuspended sediments during storms and snowmelt, and during upwelling events, respectively.

This in-situ data is now being combined with remotely sensed water quality parameters (OLCI products from Sentinel 3A and 3B) and a three-dimensional hydrodynamic model of Lake Geneva (www.meteolakes.ch) to upscale PP estimates from local to basin scale.
Assessment of the 2019 Chamoson debris flow event (Swiss Alps)
Authors: Derron Marc-Henri , Baumann Valérie , Choanji Tiggi , Noël François , Baron Ludovic , Hiscox Baux Simon , Ballu Aurelien , Nduwayezu Emmanuel , Jaboyedoff Michel
Published: March 2020

Debris flows triggered by heavy rain are common and can cause huge damages in Alpine valleys. In this case we documented the changes occurred in the Losentsé valley after the 11 August 2019 event, which caused two death and several damages to the village of Chamoson. The Chamoson basin is located in the Alps on the right side of the Rhône valley. Three main rivers drain the Chamoson basin, the Losentsé, the Cry and the Tsené. The main debris flow event occurred in the Losentsé sub-basin. The Losentsé River is 9 km long from the sources at 3000 m until the alluvial cone apex at 600 m. In the upper part of the Chamoson basin thick loose debris cones and glacial deposits lie on steep slopes, the geology of the middle basin is formed by unstable clayey shales with several active landslides on both lateral valley slopes.

The village of Chamoson is located on the huge alluvial cone built with torrential events from the three main rivers. Since the XIX century, several big debris flow events (1898, 1923, 2003, 2018) were recorded in this area and mitigation measures were built in the principal rivers. Unfortunately, the 2019 debris flows overflowed the channels limit when the flows reached the alluvial cone apex, reaching the road and took a car with 2 persons inside. Upstream in the middle basin 2 wood bridges were destroyed and many concrete or stone walls (mitigation measures) along the river were damaged.

After the event we acquired pictures with a drone from the sources area and the Losentsé river valley in order to have a post event image. With this image we could analyse and map the source areas and the inundated areas in the Losentsé channel. We did also field observation along the river.

After comparing the pre- and post-event images we mapped the middle and upper basin inundated areas by the 2019 event and the described the deposits and eroded sections along the river. We calculated the peak discharge of 1000 m3/s for this event using the inundated transversal profile area near the cone apex and the flow velocity obtained from a movie. The peak discharge corresponds to 4 in the size classification for debris flows (Jacob et al., 2005).

Reference:

Jakob, M. (2005). A size classification for debris flows. Engineering geology, 79(3-4), 151-161.
Physically-based oscillations of the Laurentide under glacial conditions.
Authors: Moreno Daniel , Blasco Javier , Álvarez-Solas Jorge , Robinson Alexander , Montoya Marisa
Published: March 2020

The climate during the last glacial period was far from stable. Evidence has shown the presence of layers of ice-rafted debris (IRD) in deep sea sediments, which have been interpreted as quasi-periodic episodes of massive iceberg calving from the Laurentide Ice Sheet (LIS). Several mechanisms have been proposed, yet the ultimate cause of these events is still under debate. In fact, one of the main sources of uncertainty and diversity in model response is the choice of basal friction law. Therefore, it is essential to determine the impact of this feature in glacial transport and erosion, deposition of sediments and ice streams among others. We herein study the effect of a wide range of basal friction parameters and laws under glacial conditions over the LIS. In addition, the impact of the thermodynamic state of the ice is taken into account by means of two independent procedures: a two-valued friction coefficient approach and an active basal hydrology. The aim is to determine under what conditions, if any, physically-based oscillations are possible in a three-dimensional hybrid ice-sheet model. Increasing our understanding of both basal friction laws and basal hydrology will improve not only reconstructions of paleo ice dynamics but also help to constrain the potential future evolution of current ice sheets.
PISM paleo simulations of the Antarctic Ice Sheet over the last two glacial cycles
Authors: Albrecht Torsten , Winkelmann Ricarda , Levermann Anders
Published: March 2020

Simulations of the glacial-interglacial history of the Antarctic Ice Sheet provide insights into dynamic threshold behavior and estimates of the ice sheet's contributions to global sea-level changes, for the past, present and future. However, boundary conditions are weakly constrained, in particular at the interface of the ice-sheet and the bedrock. We use the Parallel Ice Sheet Model (PISM) to investigate the dynamic effects of different choices of input data and of various parameterizations on the sea-level relevant ice volume. We evaluate the model's transient sensitivity to corresponding parameter choices and to different boundary conditions over the last two glacial cycles and provide estimates of involved uncertainties. We also present isolated and combined effects of climate and sea-level forcing on glacial time scales. 
Experimental study of the effect of stress on α → β quartz transformation at lower continental crust pressure and temperature conditions
Authors: Moarefvand Arefeh , Gasc Julien , Fauconnier Julien , Deldicque Damien , Labrousse Loic , Schubnel Alexandre
Published: March 2020

Based on experimental observations, there have been claims that deviatoric stresses may trigger high pressure phase transitions below their equilibrium transition pressures. This implies that the phase assemblages observed in exhumed rocks may reflect stresses induced by tectonic overpressure rather than mere lithostatic pressure, thus resulting in overestimated maximum depths of burial. Despite the numerous studies that have addressed whether mean or principal stress may trigger polymorphic phase changes, the case is still not completely clear. The aim of this study is therefore to investigate the role of deviatoric stress on phase transitions at high PT conditions. In this study, we investigated the α-β transition of quartz, which is one of the most common mineral of the Earth’s crust. This transition has a particular importance for the lower continental crust because of the significantly different elastic properties of the two polymorphs. The α-β quartz transition is also a good experimental candidate because of its displacive and quasi-instantaneous nature.

A series of experiments was performed with a new high pressure Griggs-type apparatus equipped with ultrasonic monitoring, at the ENS Paris. Cored rock samples of Arkansas Novaculite (mean grain size of 5.6 mm) were subjected to pressure and temperature conditions of 0.5-1.5 GPa and ~ 850 °C. The deviatoric stress was increased to cross the transition while keeping the temperature constant. Two p-wave transducers were used on top and bottom of the assembly as transmitter and receiver to measure travel times across the assembly. The quartz a-b transition was directly observed by a time-shift of the p-wave arrival in the order of 10 ns. The mechanical data clearly show that the phase transformation is controlled by mean stress. The quartz α-β transition induces a softening behavior on our sample because of the volume change induced by the reaction. According to the elastic properties of α and β quartz, the variation of p wave velocity for the quartz α-β transition is in the order of 10 %. The present active monitoring method allowed us to detect variations smaller than 5 %, which can be explained by a partial transformation due to local stress heterogeneities in the sample, since microscopic stress at the grain scale can be different than the macroscopic stress that we measure.
Sediment starvation is the primary factor of tidal ingress in the Mekong delta
Authors: Vasilopoulos Grigorios , Le Quan Quan , R. Parsons Daniel , E. Darby Stephen , N. Hung Nguyen , P. D. Tri Van , Haigh Ivan , Voepel Hal , Aalto Rolf , Nicholas Andrew
Published: March 2020

The Vietnamese Mekong Delta (VMD) is home of 18 million people, provides enough food to cover 50% of the country’s nutritional needs and underpins the welfare of the rapidly growing population of the wider region. The longer-term future sustainability of this great delta, formed over millennia, is uncertain. The region is threatened by climate change induced eustatic sea-level rise (SLR), and by severe land loss. The latter is the result of a number of factors that are, in their majority, driven by human activities. They include dam impoundment that reduces the amount of sediment reaching and slowly building up the delta, sand mining which rapidly depletes the delta from its slowly accumulated sediment reserves and ground water extraction which enhances sediment compaction and accelerates delta subsidence.

In May 2018 we undertook a delta-scale survey to map the bathymetry of all of the main distributary channels of the VMD. Comparisons of these survey data with existing datasets from 1998 and 2018 reveal major increases of channel depth. They show that between 1998 and 2008 the VMD lost in excess of 370 million cubic meters of sediment, while the respective value for the period between 2008 and 2018 is 635 million cubic meters, suggesting an accelerating trend of sediment loss from the system.

We assume a ‘business as usual’ scenario for delta management practices and propagate delta degradation into the future, generating delta analogues for years 2028 and 2038. We combine these delta analogues with projections of SLR for the region for up to year 2098 and a number of boundary condition scenarios into a delta-scale hydraulic model. The fluvial-tidal interactions resolved in our numerical modelling simulations reveal that channel deepening is the key driver of tidal ingress into the delta plain for the next few decades. For the longer-term future (2098), the combined effects of predicted SLR and channel incision can lead to an increase of tidal ingress by 20%. This may destabilise delta bifurcations, is likely to increase bank erosion and flood risk into the future and can have sever implications for saline intrusion into the delta plains.
Methane emissions from coal mines ventilation shafts in Upper Silesia, Poland
Authors: Stanisavljevic Mila , Nęcki Jaroslaw , Korbeń Piotr , Maazallahi Hossein , Menoud Malika , Defratyka Sara , Vinkovic Katarina , van der Veen Carina , Chmura Łukasz , Zieba Damian , Schmidt Martina , Wołkowicz Wojciech , Röckmann Thomas , Wietzel Julia , Swolkień Justyna
Published: March 2020

Atmospheric methane is the second most important anthropogenic greenhouse gas after carbon dioxide. On the global scale, methane emissions are reasonably well constrained but the contributions from individual sources are highly uncertain (Saunois, 2016). According to bottom-up estimates, methane emissions from underground coal mining excavation contribute 11% to all anthropogenic methane sources (Saunois, 2016). However, there is a lack of in situ measurement to verify these estimates. Here we present results from measurements of the methane mole fraction over the Polish part of the Upper Silesian Coal Basin (USCB). Methane mole fraction was measured using vehicles equipped with high precision laser-based instruments (Picarro G2201-i CRDS, Picarro G2301- CRDS). Basic meteorological data (wind speed, wind direction) and GPS location data were collected on the roof of the vehicles. In order to obtain emission estimates, we attempted to cross the plumes from the coal mine shafts using public roads approximately perpendicular to plume downwind from the source. When possible, the plumes were intersected several times at different distances in order to have a closer look at uncertainties. A Gaussian plume model was used to calculate the release rate from the methane single source.

In addition to methane mole fraction measurements, we collected air samples for isotopic characterization (δ13C and δD) using isotope ratio mass spectrometry. We observed significant variation in measured methane isotopic composition over USCB (the results are in a range of -321 to -142 ‰ SMOW for δD and -31 to -58 ‰ VPDB for δ13CH4). The results indicated a much larger variability of the isotopic composition of methane emitted from coal mines than assumed previously, which may complicate the distinction of methane emissions from different sources by isotopic characterization.

Keywords: Methane, Greenhouse Gases, Clime Change, Coal Mine Ventilation Shafts, Methane Isotopic Compositions

Reference:

Saunois, M., Bousquet, P., Poulter, B., et al., 2016a. The global methane budget, 2000–2012. Earth Syst. Sci. Data 8, 697–751. https://doi.org/10.5194/essd-8-697-2016. www.earth-syst-sci-data.net/8/697/2016/.

This work is part of the Marie Sklodowska-Curie Initial Training Network MEMO2 , which enable us to extend these measurements to other European locations
Gender aspects in Marine Science
Authors: Kısakürek Ibsen Başak , Kutser Tiit , Matthes Katja , Schmeck Marike , Stadmark Johanna , Vaitkevičienė Viktorija , Valve Helena , Waniek Joanna , Werner Iris
Published: March 2020

The EU-funded project, Baltic Gender (www.baltic-gender.eu), has been working since 2016 to help reduce gender segregation and gender inequalities in marine science and technology. Gender-sensitive indicators from eight institutions participating in Baltic Gender (from Estonia, Finland, Germany, Lithuania and Sweden) set the scene for the status of gender equality in marine S&T in Europe today. Although 34-50% of doctorate students are women, this proportion drops dramatically at professorship positions (0-27%). The glass ceiling index can be used to look at the career phase, where bottlenecks in an institution appear (i.e., where the retention rates of different genders vary the most). More women than men are observed to drop out at the transition from postdoc to faculty positioning or from junior professorship to professorship, depending on the career path development plan of the specific institution. Data from German research ships (Sonne, Maris S. Merian, Meteor, Poseidon, Alkor, Polarstern, Heincke, Elisabeth Mann Borgese) show that the average length of the scientific cruises led by men and women was the same in 2018, but only one fifth of the chief scientists were women.

Baltic Gender implemented activities at three levels. At the individual level, initiatives (such as mentoring, leadership trainings and grass-root networks) were introduced to support career growth and networking, especially at those career stages where bottlenecks exist. At the structural level, best practice examples were selected from Baltic Gender partners and collected in a handbook to promote structural changes. These best practice examples support equal opportunities, transparent processes and respectful cooperation in marine sciences. Additionally, custom tailored training sessions were organised in the Baltic Gender institutions to raise awareness on various topics such as unconscious bias, work-life balance, border violations to name a few. At the research level, a new methodology that guides the integration of gender perspectives into the content of marine science projects was developed and tested. Finally, Baltic Gender endorsed the integration of the above-mentioned indicators, initiatives and practices in the Gender Equality Plans (GEPs) of its partner institutions, paving the way for long lasting and gender fair structures.