bluuebunny/crossref_metadata_2025 huggingface dataset:
Temporal water column dynamics control microbial methane oxidation above an active cold seep (Doggerbank, North Sea)
Authors: de Groot Tim , Menoud Malika , Röckmann Thomas , Maazallahi Hossein , Rush Darci , Mesdag Chris , Meijninger Bart , Niemann Helge
Published: March 2020

Methane is a potent greenhouse gas with strongly increasing atmospheric concentrations since industrialisation. In the ocean, methane is most dominantly produced in sediments and is of microbial and/or thermogenic origin. Uprising methane may escape from the ocean floor to the overlying water column where it can be oxidized by methane oxidizing bacteria. The aerobic methane oxidation (MOx) is thus an important final barrier, which can mitigate methane release from the ocean to the atmosphere where it contributes to global warming. Nevertheless, there is rather little knowledge on the temporal dynamics of the microbial methane filter capacity in the water column. To gain a better understanding of the dynamics, we conducted two 48 hours’ time-series experiments during highly stratified conditions in summer and and mixed water column conditions in autumn above an active methane seep in the North Sea (Doggerbank, 41m water depth). At Doggerbank, dissolved CH4  δ13C-values (<-65 ‰) indicate a microbial CH4 origin, and seismic data suggest a gas pocket at >50 m sediment depth. Our time series measurement showed that CH4 concentrations were highly elevated with up to 2100 nM in bottom and 350 nM in surface waters under stratified conditions. The maxima showed a ~12h periodicity, indicating that the flux of CH4 from the seep was linked to tidal dynamics with the lowest CH4 concentrations at rising tide and enhanced flux at falling tide. In contrast, during mixed water column conditions we found lower maxima of only up to 450 nM. Yet, during mixed conditions we found that surface water methane concentrations were on average XX-fold higher compared to stratified conditions, suggesting a higher methane efflux to the atmosphere during this time period.  MOx activity showed a similar temporal behaviour suggesting that tidal dynamics are an important control on the efficiency of the microbial CH4 filter in the water column. Under stratified conditions MOx rates were highest in bottom waters (<5.7 nM/day), however we also found high MOx rates in near-surface waters at times of elevated seep activity during stratified (<3.2 nM/day) and mixed water column conditions (<16.2 nM/day). Our results indicate that the efficiency of the microbial filter is affected by temporal dynamics and seasonality.
Classification and Separation of Diffraction Energy on Pre-Migration Seismic Data using Deep Learning
Authors: Lowney Brydon , Lokmer Ivan , O'Brien Gareth Shane , Bean Christopher
Published: March 2020

Diffractions are a useful aspect of the seismic wavefield and are often underutilised. By separating the diffractions from the rest of the wavefield they can be used for various applications such as velocity analysis, structural imaging, and wavefront tomography. However, separating the diffractions is a challenging task due to the comparatively low amplitudes of diffractions as well as the overlap between reflection and diffraction energy. Whilst there are existing analytical methods for separation, these act to remove reflections, leaving a volume which contains diffractions and noise. On top of this, analytical separation techniques can be costly computationally as well as requiring manual parameterisation. To alleviate these issues, a deep neural network has been trained to automatically identify and separate diffractions from reflections and noise on pre-migration data.

Here, a Generative Adversarial Network (GAN) has been trained for the automated separation. This is a type of deep neural network architecture which contains two neural networks which compete against one another. One neural network acts as a generator, creating new data which appears visually similar to the real data, while a second neural network acts as a discriminator, trying to identify whether the given data is real or fake. As the generator improves, so too does the discriminator, giving a deeper understanding of the data. To avoid overfitting to a specific dataset as well as to improve the cross-data applicability of the network, data from several different seismic datasets from geologically distinct locations has been used in training. When comparing a network trained on a single dataset compared to one trained on several datasets, it is seen that providing additional data improves the separation on both the original and new datasets.

The automatic separation technique is then compared with a conventional, analytical, separation technique; plane-wave destruction (PWD). The computational cost of the GAN separation is vastly superior to that of PWD, performing a separation in minutes on a 3-D dataset in comparison to hours. Although in some complex areas the GAN separation is of a higher quality than the PWD separation, as it does not rely on the dip, there are also areas where the PWD outperforms the GAN separation. The GAN may be enhanced by adding more training data as well as by improving the initial separation used to create the training data, which is based around PWD and thus is imperfect and can introduce bias into the network. A potential for this is training the GAN entirely using synthetic data, which allows for a perfect separation as the points are known, however, it must be of sufficient volume for training and sufficient quality for real data applicability.
Orbital pacing of large fluctuations in wildfire activity during the Pliensbachian
Authors: Hollaar Teuntje , Baker Sarah , Deconinck Jean-Francois , Mander Luke , Ruhl Micha , Hesselbo Stephen , Belcher Claire
Published: March 2020

At present Earth’s climate is warming and the frequency of large wildfires appears to be increasing (Westerling and Bryant, 2008). Long term trends in climate and the effect on wildfire are understudied and examining the geological record can aid current understanding of natural variability of wildfire over longer time scales. The Early Jurassic is a period of overall global warmth, and therefore serves as a suitable modern-day analogue to understand changes in the Earth System. The Early Jurassic was characterized by major climatic and environmental perturbations which can be seen preserved at high resolution on orbital timescales. Recent research has indicated from Quaternary deposits that wildfires respond to orbital forcings (Daniau et al., 2013). This study tests whether wildfire activity corresponds to changes over Milankovitch timescales in the deep past.

        A high-resolution astrochronology exists for the Upper Pliensbachian in the Llanbedr (Mochras Farm) borehole (NW Wales). Ruhl et al. (2016) show that elemental concentration recorded by hand-held X-ray fluorescence (XRF), changes mainly at periodicities of ~21,000 year, ~100,000 year and ~400,000 year, and which can be related to visually described sedimentary bundles.

        We have quantified the abundance of fossil charcoal at a high resolution (10-15 cm) to test the hypothesis that these well-preserved climatic cycles influenced fire activity throughout this globally warm period. Our results suggest that variations in charcoal abundance are coupled to Milankovitch forcings over periods of ~21,000 and ~400,000 years. Supplementary to the charcoal record, a high-resolution clay minerology dataset has been generated, which indicates the presence of the 400ky cycle. Decreased hydrology on land, corresponds to increased charcoal production. We suggest that these changes in fire relate to changes in seasonality and monsoonal activity that drove changes in vegetation that are linked to variations in the orbital forcing.
The onset of dilatancy in rocks
Authors: Schumacher Sandra , Gräsle Werner
Published: March 2020

The onset of dilatancy determines the start of critical fracture growth in rocks under increasing load. For various applications such as the construction of nuclear repositories or dams, a quantitative comprehensive knowledge on the critical conditions leading to dilatancy is required.

Thus, it is important to determine the parameters, which control the dilatant behaviour of rocks, and to analyse their interactions.

We conducted a series of undrained triaxial experiments on two consolidated, fully saturated Opalinus Clay samples from the Mont Terri underground research lab and one sample of Bunter Sandstone from southern Lower Saxony. By testing only a few samples but them extensively, we avoid that the natural material heterogeneity among multiple samples affected our results. Here we show that our approach allows identifying new correlations between different parameters with surprising clarity.

During the experiments, which can take years, the samples are repeatedly exposed to increases in differential stress (σ1 -σ3) into the dilatant regime but always well below the point of failure. This we achieve by monitoring the pore pressure during the increase in differential stress. The onset of dilatancy becomes visible as clear drop in pore pressure with increasing differential stress.

In addition to the detection of the onset of dilatancy via the pore pressure evolution, pressure diffusion experiments are performed to determine the onset of dilatancy. For this, in the dilatant regime, the differential stress is kept constant and the pore pressure on one side of the sample is de- and increased repeatedly, while the reaction of the pore pressure on the other side of the sample is monitored. With the pore pressure pulse diffusing though our sample specimen, this controlled pore pressure variation induces a transition between dilatant and subdilatant regimes at constant differential stress.

The values for the onset of dilatancy derived by these two methods permit a comprehensive analysis of the dilatant behaviour not only of the Opalinus Clay samples, but also of the Bunter Sandstone sample. Our results show that dilatant behaviour of the tested materials is not governed by only one parameter but by an intricate interplay of several parameters.  Consequently, the development of an equation of state for the dilatant behaviour of different types of rock is achievable. However, due to the multiple parameter dependencies, it will be a time-consuming undertaking.
Kinetic simulations of the Jovian ion circulation around Ganymede and space weather implications
Authors: Plainaki Christina , Massetti Stefano , Jia Xianzhe , Mura Alessandro , Anna Milillo , Grassi Davide , Sindoni Giuseppe , D'Aversa Emiliano
Published: March 2020

The exosphere of Jupiter’s moon Ganymede is the interface region linking the moon’s icy surface to Jupiter’s magnetospheric environment. Space weather phenomena driven by the variability of the radiation environment within the Jupiter system can have a direct impact on the sputtering-induced exosphere of Ganymede.

In this work we simulate the Jovian ion precipitation to Ganymede’s surface for different moon orbital phases around Jupiter. In particular, we consider three different configurations between Ganymede’s magnetic field and Jupiter plasma sheet, similar to those encountered during the Galileo G2, G8, and G28 flyby (i.e., the moon above, inside, below the Jupiter plasma sheet). We discuss the differences between the various ion precipitation patterns and the implications in the density distribution of the sputtered-water exosphere of this moon. We also comment the possible relation of these ion precipitation patterns with the surface brightness asymmetries both between Ganymede’s polar cap and equatorial regions and between the leading and trailing hemispheres. The results of this preliminary analysis are relevant to the JUICE mission and in particular to the preparation of the future observation strategies for the environment of Ganymede.
Extracting higher-mode dispersion curves from ambient noise data by using F-J method to acquire more accurate crustal and upper-mantle structure for the east of South China
Authors: Chen Juqing , Chen Xiaofei
Published: March 2020

It has been widely recognized that the cross-correlation function (CCF) of ambient noise data recorded at two seismic stations approximates to the part of Green’s Function between these two stations. Theoretically, the CCF should include the higher modes, apart from the fundamental mode. However, currently well-known and mature methods that can extract dispersion curves are not pretty proficient in extracting higher modes. Fortunately, our newly proposing method, the Frequency-Bessel Transform Method (F-J Method), has presented its obvious advantage in extracting higher modes. This study applied F-J method to seismic ambient noise data for the east of South China, including Jiangnan Orogen and South China Fold System. We have acquired higher modes, not to mention the fundamental mode with wider frequency than previous studies. Combining both fundamental mode and higher modes, we used L-BFGS inversion method to inverse and acquire more accurate crustal and upper-mantle structure than previous studies only adopting fundamental mode for the east of South China. As shown in this study for the east of South China, we can use F-J method  to conveniently and precisely extract multimodes from ambient noise data and thus add more constrains for inversion results, which can significantly improve the preciseness of imaging crustal and upper-mantle structure.
Simulation of seismic wave scattering for the computation of probabilistic coda-wave sensitivity kernels
Authors: Zhang Tuo , Sens-Schönfelder Christoph
Published: March 2020

Scattered seismic coda waves are frequently used to characterize small scale medium heterogeneities, intrinsic attenuation or temporal changes of wave velocity. Spatial variability of these properties raises questions about the spatial sensitivity of seismic coda waves. Especially the continuous monitoring of medium perturbations using ambient seismic noise led to a demand for approaches to image perturbations observed with coda waves. An efficient approach to localize the property variations in the medium is to invert the observations from different source-receiver combinations and different lapse times in the coda for the location of the perturbations. The key of such an inversion is calculating the coda-wave sensitivity kernels which describe the connection between observations and the perturbation. Most discussions of sensitivity kernels use the acoustic approximation and assume wave propagation in the diffusion regime.

We model 2-D  elastic multiple nonisotropic scattering in a random medium with spatially variable heterogeneity and attenuation. The Monte Carlo method is used to numerically solve the radiative transfer equation that describes the wave scattering process here. Recording of the specific intensity of the wavefield I(r,n,t) which contains the complete information about the energy at position r at time t with the propagation direction n allows us to calculate sensitivity kernels according to rigorous theoretical derivations. We investigate sensitivity kernels that describe the relationships between changes of the model parameters P- and S-wave velocity, P- and S-wave attenuation, and the strength of fluctuation on the one hand and the observables envelope amplitude, travel time changes and decorrelation on the other hand. These sensitivity kernels reflect the effect of the spatial variations of medium properties on wavefield. Our work offers a direct approach to compute these new expressions and adapt them to spatially variable heterogeneities. The sensitivity kernels we derived are the first step in the development of an inversion approach based on coda waves.
A new auroral phenomenon: The anti-black aurora
Authors: Nel Amoré , Kosch Mike
Published: March 2020

Black auroras are small-scale features that show a significant reduction in optical brightness, i.e. reduced flux of particle precipitation, compared to the surrounding diffuse aurora. It typically occurs post-substorm after magnetic midnight. This phenomenon also exhibits lower mean energy than the surrounding brighter aurora it is embedded in. The underlying mechanisms that cause black auroras are not yet fully understood, although several theories have been proposed: a coupled ionospheric-magnetospheric generation mechanism, and a magnetospheric generation mechanism. This shift in particle precipitation energy to a lower mean value is confirmed by using synchronised dual-wavelength optical and EISCAT incoherent scatter radar observations that ran in parallel, and agrees with the magnetospheric generation mechanism theory. Now reported for the first time is an even more elusive small-scale optical structure has been observed occurring paired with ~10% of black aurora patches. A patch or arc segment of enhanced luminosity, distinctly brighter than the diffuse background, which we name the anti-black aurora, may appear adjacent to the black aurora. The anti-black aurora always moves in parallel to the black aurora. The paired phenomenon always drifts with the same average speed in an easterly direction. From the first dual-wavelength observations of anti-black and black aurora pairs, we show that the anti-black and black auroras have a higher and lower mean energy, respectively, of the precipitating electrons compared to the diffuse background.
The Nitrogen Dynamics of Multi-species Grasslands when Subject to Drought and Re-wetting.
Authors: Cummins Saoirse , Finn John , Lanigan Gary , Richards Karl , Misselbrook Tom , Cardenas Laura , Reynolds Chris , Krol Dominika
Published: March 2020

It is predicted that climate change will result in more extreme and frequent weather events including flooding and drought. Nitrous oxide (N2O) is a potent greenhouse gas having 298 times the global warming potential of CO2. The ‘Birch effect’, the term given to high  N2O fluxes following the drying and re-wetting of soils, is an accelerator of this process. Multi species grasslands have been shown have higher nitrogen use efficiency and potential for drought resilience and recovery. This experiment analysed the nitrogen dynamics of multi-species grasslands by means of quantifying the responses of soil mineral nitrogen (NH4+ and NO3-) and N2O fluxes during an eight week simulated drought, re-wetting and fertiliser application two weeks after the re-wetting event. A simplex experimental design was used to determine species and functional group effects which could potentially influence responses. The hypothesis of this study was therefore that multi species grasslands would mitigate the ‘Birch effect’ resulting in less erratic transformations of soil mineral nitrogen and lower N2O fluxes compared to monocultures. This study also predicted a lasting legacy effect of drought on soil systems resulting in prolonged heightened N2O fluxes. Drought resulted in a depletion of soil NO3-, increased  levels of NH4+ and background level N2O emissions. Following re-wetting soil mineral N underwent transformations from NH4+ to NO3- indicating nitrification. Four times more N2O emissions were recorded during re-wetting period compared to fertilizer application. There was no lasting legacy effect of drought and re-wetting on N2O fluxes observed during fertilizer application two weeks after re-wetting bar T. repens which has implications for grassland management strategies.
Fibrous ferrierite from Lovelock, Nevada, USA
Authors: Gualtieri Alessandro , Zoboli Alessandro , Di Giuseppe Dario , Baraldi Cecilia , Gamberini Maria Cristina , Malferrari Daniele , Lassinantti Gualtieri Magdalena , Bailey Mark
Published: March 2020

Ferrierite is the name of a family of zeolite minerals that includes three species with the same topological framework (FER) but with different content of extra-framework cations. In Nevada (USA), the zeolite-rich tuff deposit of Lovelock is the largest occurrence of diagenetic ferrierite-Mg, one of the member of the family. Recent studies have shown that Lovelock ferrierite can exhibit fibrous-asbestiform crystal habit and may possess the same physical-chemical and crystallographic properties of carcinogenic fibrous erionite, Nevertheless, it has not yet been classified by the International Agency for Research on Cancer (IARC). Nowadays, outcrops hosting fibrous ferrierite are being mined in Nevada for commercial purposes. Dust generated by these excavation activities may expose workforces and general public to this potential natural hazard. The main goal of this study was to perform a mineralogical and morphometric characterisation of the tuff deposit at Lovelock and evaluate the distribution of fibrous ferrierite in the outcrop. For this purpose, a multi-analytical approach including X-ray powder diffraction, scanning and transmission electron microscopy techniques, micro-Raman spectroscopy, thermal analyses, and surface-area determination was applied. The results indicate that fibrous ferrierite is widespread in the deposit and intermixed with mordenite and feldspar, although there are variations in the spatial distribution in the bedrock. The crystal habit of the ferrierite ranges from prismatic to asbestiform (elongated, thin and slightly flexible) and fibres are aggregated in bundles. According to the WHO counting criteria, most of the ferrierite fibres can be classified as breathable. While waiting for confirmatory in vitro and in vivo tests to assess the actual toxicity/pathogenicity potential of this mineral fibre, it is recommended to adopt a precautionary approach for mining operations in this area to reduce the risk of exposure.
Seasonal weather regimes in the North Atlantic region: towards new seasonality?
Authors: Breton Florentin , Vrac Mathieu , Pascal Yiou , Vaittinada Ayar Pradeebane , Jézéquel Aglaé
Published: March 2020

European climate variability is shaped by atmospheric dynamics and local physical processes over the North Atlantic region. Both have strong seasonal features. So, a better understanding of their future seasonality is essential to anticipate changes in weather conditions for human and natural systems. We revisit the notion of seasons over the North Atlantic region through the concept of seasonal weather regimes (SWRs), by classifying daily fields of geopotential height at 500 hPa (Z500) without a priori separation of seasons. We use data from the ERA-Interim reanalysis, and from 12 climate models of the fifth phase of the Coupled Model Intercomparison Project. The spatial and temporal variability of SWR structures is investigated, as well as associated patterns of surface air temperatures. Although the climate models have biases, they reproduce structures and evolutions of SWRs similar to the reanalysis over 1979-2017: decreasing frequency of winter conditions, which start later and end earlier, and increasing frequency of summer conditions starting earlier and ending later in the year. These changes are stronger over 1979-2100 than over 1979-2017. By the end of the 21st century, the typical past winter conditions (e.g. 1979-2017) have almost disappeared and correspond to future extreme cold conditions. A new cluster related to summer that was almost absent in 1979-2017 (corresponding to past extreme warm conditions in the past) becomes dominant. To understand whether these changes are linked to uniform Z500 increase or changes in Z500 spatial patterns, we detrend the data (but impose a stationary seasonality) by removing the trend in the seasonal Z500 regional average to define detrended seasonal weather regimes (d-SWRs). The temporal properties of d-SWRs appear almost constant, whereas spatial patterns show evolution. Our results indicate that the evolutions of the SWR temporal features are caused by the regional Z500 trend and that changing spatial patterns in d-SWRs account for the heterogeneity of this trend. Previous research has shown that this large-scale Z500 trend is linked to human influence, suggesting that it drives the changes in seasonality that we find.
Geoarchaeological and paleoenvironmental reconstruction of the Late Quaternary climate- environmental-human nexus in the Kurdistan region of Iraq
Authors: Forti Luca , Regattieri Eleonora , Mercuri Anna Maria , Mazzini Ilaria , Pezzotta Andrea , Florenzano Assunta , Conati Barbaro Cecilia , Peyronel Luca , Morandi Bonacossi Daniele , Zerboni Andrea
Published: March 2020

During the late Quaternary, Iraqi Kurdistan was the scenario of several fundamental human-related
events including the dispersion of Homo in Asia and Europe, the origin of agriculture, the beginning
of urbanization, and the formation of the first state entities. We present the initial results of a
geoarchaeological investigation in this area, which aims to reconstruct a detailed framework of the
relationship between climatic changes, landscape responses, human adaptation, and settlement
distribution during the Late Quaternary. Paleoenvironmental and paleoclimatic data were collected
from two key areas: the territory of the Navkur and Faideh plains, in northern Kurdistan, and a portion
of the Erbil plain, in southern Kurdistan. In the two regions, the Land of Niniveh and MAIPE
archaeological missions are operating. Remote sensing, GIS analyses, and geomorphological survey
are the tools used for the geomorphological reconstruction of ancient hydrology (fluvial pattern) and
the evolution of distinct landforms. Geochemical and geochronological analyses on speleothems from
the Zagros piedmont caves of same region provide information on Holocene climatic variability in
the area. Whereas environmental settings and human land use are investigated on the basis of
sedimentological, palynological, micropaleontological, and geochemical analyses of a fluvio-
lacustrine sequences preliminary dated between 40 and 9 ka BP. The lacustrine sequence is composed
by clayey and silt-sandy sediments alternating calcareous and organic matter-rich layers.
Environmental and geomorphological data have been compared with archaeological information
(mostly the chronological distribution of the archaeological sites) to interpret exploitation of natural
resources, the settlement dynamics and shift in land use. 
New insights on carbon use efficiency using calorespirometry – a bioenergetics-based model
Authors: Chakrawal Arjun , M. Herrmann Anke , Manzoni Stefano
Published: March 2020

Soil organic carbon (SOC) represents both a source of energy (catabolism) and a building material for biosynthesis (anabolism) for microorganisms. Microbial carbon use efficiency (CUE) – the ratio of C used for biosynthesis over C consumed – measures the partitioning between anabolic and catabolic processes. While most work on CUE has been based on C mass flows, the role of SOC energy content, microbial energy demand, and general energy flows on CUE have been rarely considered. Thus, a bioenergetics perspective on CUE could provide new insights on how microorganisms utilize C substrates and ultimately allow C to be stabilized in soils.

The microbial growth reactions are generally associated with a negative enthalpy change, which results in heat dissipation from the system. This heat can be measured using an isothermal calorimeter, which is often coupled with respiration measurements. This coupled system allows studying energy and C exchanges, and calculating their ratio referred to as the calorespirometric ratio (CR). Here, we formulate a coupled mass and energy balance model for microbial growth and provide a generalized relationship between CUE and CR. In the model, we consider two types of organic C in soils, the added substrate (i.e., glucose) and the native SOC. Furthermore, we assume that glucose is taken up via aerobic (AE) and two fermentation metabolic pathways – glucose to ethanol (F1) and glucose to lactic acid (F2); for simplicity, only aerobic growth on the native SOC was adopted. We use this model as a framework to generalize previous formulations and generate hypotheses on the expected variations in CR as a function of substrate type, metabolic pathways, and microbial properties (specifically CUE). In turn, the same equations can be used to estimate CUE from measured CR.

Our results show that in a non-growing system, CR depends only on the rates of different metabolic pathways (AE, F1, and F2). While in growing systems, CR is a function of rates as well as growth yields for these metabolic pathways. Under purely aerobic conditions, our model predicts that CUE increases with increasing CR when the degree of reduction of the substrate is higher than that of the microbial biomass. Similarly, CUE decreases with increasing CR when the degree of reduction of substrate is lower than that of the biomass. In the case of combined metabolism – aerobic and fermentation simultaneously – CUE is not only a function of CR and the degree of reduction of substrates but also the rates and growth yields of all metabolic pathways involved. To summarize, in this contribution we illustrate how calorespirometry can become an efficient tool to evaluate CUE and the role of different metabolic pathways in soil systems.
High temperature in-situ study of radiative properties of basaltic dry magmas
Authors: Biren Jonas , del Campo Leire , Cosson Lionel , Li Hao , Slodczyk Aneta , Andujar Joan
Published: March 2020

Temperature is a key parameter controlling the evolution of lava flows. The hazardous behavior of eruptions prevents direct measurements of hot magmatic bodies. Hence, the temperature of magma is mostly retrieved by using non-contact methods (ground-based or satellite-based thermal cameras) based on measuring the infrared (IR) emission flux (E) of the body [1]. These well-established techniques are however subjected to important errors, ±100 °C, related to surrounding environment [2], large temperature gradients of cooling lavas [3], constant changes in composition and texture and especially an apparent lack of radiative emission properties during the lava emplacement. Despite that reducing the uncertainties of environmental and thermal gradients when measuring E is ultimately challenging, our study aimed to minimizing the uncertainty in one of the critical hitherto poorly known oversimplified parameters [3,4,5] namely spectral emissivity. Therefore, we performed optical measurements at relevant magmatic temperatures (up to 1200 °C) of representative basaltic dry magmas (MORB, alkaline, calc-alkaline). Emissivity has been systematically determined over a wide spectral (400-15000 cm-1) and thermal range (from room up to 1200 °C) using a non-contact in situ IR emissivity apparatus [6]. SEM, EMPA and Raman spectroscopy techniques were also used in order to characterize and understand the complex radiative behavior of these natural magmatic compositions. Emissivity varies accordingly with temperature and wavenumber but our results also show that small changes in bulk-rock composition produce drastic changes in emissivity at given T, with iron content and its oxidation state being the main agents controlling this parameter. Appropriate emissivity values will then help to refine current field or (space) satellite IR monitoring data (i.e. Holuhraun 2014-2015, Iceland; [3]) and to implement the thermo-rheological models of lava flows [7] as to support hazard assessment and risk mitigation.

References: [1] Kolzenburg et al. 2017. Bull. Volc. 79:45. [2] Ball and Pinkerton 2006. J. Geophys.Res., 111. [3] Aufaristama et al. 2018. Remote Sens. 10, 151 [4] Harris, A. 2013: Cambridge University press. 728. [5] Rogic et al. 2019 Remote Sens. 2019, 11, 662 [6] De Sousa Meneses et al. 2015. Infrared Physics & Technology 69. [7] Ramsey et al. 2019. Annals of Geophysics, 62, 2.

 

Keywords: Emissivity, temperature, vibrational spectroscopy, remote sensing, basalt
Monitoring Oil Exploitation Infrastructure and Dirt Roads with Object-Based Image Analysis and Random Forest in the Eastern Mongolian Steppe
Authors: Dashpurev Batnyambuu , Bendix Jörg , Lehnert Lukas
Published: March 2020

Rapid changes in land use due to intensifications of oil exploration and exploitation adversely affect the Eastern Mongolian steppe ecosystem. The expansion of supporting infrastructure and dirt road networks for oil production contribute to accelerate the human-induced land degradation process in the grasslands. So far, neither the extents of road networks nor the extent of surrounding grasslands affected by the oil industry are monitored which is generally labor consuming. This causes that no information on the changes in the area which is affected by those disturbance drivers is available. Therefore, the major aim of this study is to provide a cost-effective model to map the supporting infrastructure, sites and dirt roads of oil exploitation through classifying remotely sensed images using object-based classifications with Random Forest. By combining satellite data with different spatial and spectral resolutions (PlanetScope, RapidEye, and Landsat ETM+), the product delivers data since 2005. In the image classification, the variables of segmentation, spectral characteristics, and indices were extracted from all above mentioned imagery and used as predictors. Within this study examined the comparison analysis in order to quantify the uncertainty arising from the combination of data from different sensors in their spectral and spatial configurations. Besides that, this study analyzed the consequence of supporting infrastructure and dirt roads on surrounding ecosystems combining data from field vegetation surveys and drone imagery. Results show that overall accuracies of land use maps ranged 73%–93% mainly depending on satellites’ spatial resolution. Since 2005, the area of grassland disturbed by dirt roads and oil exploitation infrastructure increased by 88% with its highest expansion by 47% in the period 2005–2010. Consequently, the comparison of multiscale classification suggests that, although high spatial resolutions are clearly beneficial, all datasets were useful to delineate linear features such as roads. Furthermore, the results of this study provide an effective evaluation for the potential of Random Forest based model for extracting relatively narrow linear features such as roads from multiscale satellite images and map products that are possible to use for detailed land degradation assessments.
Sensitivity analysis of dissipation parameterizations in the WAVEWATCH III spectral wave model using the ST6 source term packages for Ireland Coast.
Authors: Fernández Leandro , Calvino Clement , Dias Frederic
Published: March 2020

The research we perform has important engineering applications since a lot of marine activities and offshore engineering activities are in shallow water areas where phenomena like bottom and white-capping dissipation and wind growth take place. The physical parametrization of such forcing/dissipation has become an important issue in the improvement of the performance of models in order to provide accurate sea-state information. In this regard, we perform a sensitivity analysis of dissipation parameterizations in the third-generation spectral wave model WAVEWATCH III using the ST6 source term packages, proposed by Zieger-Babanin 2015, to describe wind generation and dissipation due to white-capping and bottom friction.

A system of nested grids is used to model long distance swells generated in the North Atlantic Ocean and propagating all the way to the west coast of Ireland. We used a 30-minute coarse resolution for the North Atlantic grid, a 6-minute intermediate resolution for the North-East Atlantic, and a 3-minute fine resolution in coastal areas closer to Ireland.

The sensitivity analysis in the parameterization is based on the effect of the model performance by varying the adjustable parameters in the wind input source, swell dissipation in terms of the interaction of waves with oceanic turbulence and the drag coefficient to potentially eliminate a bias in the wind field. The results of the model for the coast of Ireland are discussed in terms of various parametrization schemes.
Using seasonal forecast for energy production: SHYMAT climate service, a small hydropower management and assessment tool
Authors: Contreras Arribas Eva , Herrero Lantarón Javier , Aguilar Porro Cristina , Polo Gómez María José
Published: March 2020

In small hydropower plants management, the operation feasibility is subjected to the Run-of-River (RoR) flow which is also depending on a high variability in water availability. The management has to accomplish with some particular operation conditions of the plant but also some environmental flow requirements. Normally hydropower plants managers use historical information of inflows in order to predict the production of energy. Although some forecast models have been already proposed and applied in the small hydropower production field, there are still an existing gap to link the results of the forecast with the decision support process. 

In the framework of the H2020 project CLARA (Climate forecast enabled knowledge services) a climate service was developed in a co-generation process, bridging the gap between data providers who provides climate-impact data on one side, and managers and policy makers on the other side. The result is SHYMAT (Small Hydropower Management and Assessment Tool), a technological solution for the integrated management of RoR plants which offers a scalable and automatically updated database accessible through an administration panel and a web end user interface. 

The pilot area is a three RoR system in the Poqueira River (southern Spain) where inflow is highly variable due to the irregularity in precipitation and snow cover duration in the contributing basin. The service combines past hydro-meteorological and forecast climate data stored with operation data for the particular plant in order to give the user a) a global view of the hydrological state of the basin, from measurements and a physically based hydrological model; b) a comparison of current information with past data; c) the expected operability of the RoR plant; d) information about the accomplishment of environmental flow requirements and water flow spill; e) the expected energy production. 

SHYMAT is easy and fully scalable to new systems thanks to the administration panel and the topology panel. The service is addressed to technicians in charge of the control operation center of this kind of plants and managers at the regional administrative headquarters of hydropower companies. Energy market operators, river basin authorities and consultants can be also potential users.

 

This research is supported by CLARA Project, which has received funding from the European Union's Horizon 2020 research and innovation programme under the Gran Agreement No 730482.
Temporal changes in the structure of the UTLS and their potential impact on lower stratospheric ozone
Authors: Kunkel Daniel , Weyland Franziska , Ball William , Hoor Peter
Published: March 2020

Although a general recovery of stratospheric ozone is expected after the successful implementation of the Montreal Protocol, strong indications for a decline in lower stratospheric ozone in the extratropics are still evident. Related studies attribute this decline to internal dynamic variability affecting the UTLS, in particular associated to the QBO and the exchange of air masses between tropical and extratropical regions. The dynamics affect the transport of ozone from the source region in the tropics into the extratropical lower stratosphere. More so, dynamics affect the structure of the lower stratosphere. In particular, the locations of the tropopause and of isentropic surfaces in the lower stratosphere, i.e., the region up to ~25 km altitude, affect the vertical profile of ozone and as such the integrated column ozone in the lower stratosphere.
This study aims to address the relation between the changing altitude of the tropopause and isentropic surfaces in the lower stratosphere and the declining ozone in the extratropical UTLS. For this we use reanalysis data from ECMWF and dynamic linear modeling to study trends of the dynamic tropopause and of the thermodynamical structure and the potential consequences of these trends for lower stratospheric ozone. In particular, we ask the question: do ozone trends still show a decline if we use a dynamic instead of a fixed coordinate system to calculate these trends?
Morpho-tectonic control on the distribution of C3-C4 plants during Late Plio-Pleistocene in the central Himalayan Siwaliks
Authors: Sanyal Prasanta , Roy Biswajit , Ghosh Sambit
Published: March 2020

The Siwalik deposits of Himalayan foreland basin (HFB) preserved the Miocene records of the Himalayan tectonics, monsoonal variation and evolution of C4 plants. Previous vegetation reconstructions emphasized   the Late Miocene expansion of C4 plants (ca. 7 Ma) with an implicit assumption that the vegetation thrived in the floodplain of lowland rivers. The coarsening-upward sequence of the Siwalik Group suggests deposition  in an alluvial fan setting in which the Middle and Lower Siwaliks are deposits of distal area whereas the Upper Siwaliks represent proximal areas of the fan. The modern alluvial fans forming in the Himalayan foothills show a significant difference in elevation and vegetational composition between proximal and distal areas. In the HFB, the elevation difference between the proximal and distal areas is expected to be more pronounced due to surface exhumation of the Siwalik deposits. The increased elevation would have had affected the vegetation distribution in the Upper Siwaliks which implies that vegetation  inproximal part of the fan might not represent lowland floodplain. However, the vegetation composition is less understood from the Upper Siwaliks region as conventional proxies are scanty in these younger foreland deposits.

In the present study, the impact of elevation on vegetation distribution in the HFB is examined from comparatively higher exhumed Late Plio-Pleistocene Siwalik deposits at SuraiKhola (Nepal). The δ13C values of bulk soil organic matter (SOM), n-alkane and n-alkanoicacid from the SuraiKholapaleosols suggest most commonly observed expansion of the C4 plants at ca. 7 Ma, and a unique second phase of expansion of C3 plants after ca. 3 Ma. The higher δD values in n-alkane and n-alkanoicacid suggest that the climate was drier in last 4 Myr; most likely driven by the onset of the Northern Hemisphere Glaciation (NHG). The growth of C3 plants was favored due to cool climatic condition induced by higher elevation in the proximal part of the fan. The water-bearing conglomerate units in the Upper Siwaliks helped the C3 plants to thrive in a relatively drier climate. Therefore, the higher abundance of C3 plants in the Upper Siwaliks suggests morpho-tectonic control on vegetation with the possible influence of NHG.

 
Effect of Hydrologic Export on Soil Carbon Turnover Rates
Authors: Hararuk Oleksandra , Jones Stuart , Solomon Christopher
Published: March 2020

Soil is the largest terrestrial carbon (C) reservoir and is an important component of climate-carbon feedbacks, potentially sequestering or releasing large amounts CO2 from or to the atmosphere. In global land models soil C dynamics is determined by the long-term balance between C inputs and turnover rates, and the latter are usually a function of soil texture, temperature, and soil moisture, which represents environmental limitation of microbial soil organic carbon (SOC) mineralization. Hydrologic C export is often overlooked in the terrestrial C cycle models, likely because proportionally soils contain a very small amount of C that can be exported with runoff, contributing around 2.9 Pg C yr-1 to aquatic systems globally. However, ignoring hydrologic C export in areas, where it has substantial effect on SOC turnover rate, could result in systematic overestimation of SOC stocks and inaccurate simulation of SOC responses to changing environmental conditions. We combined water quality data from the United States Geological Survey with hydrologic and soil chemistry data products to estimate the relative contribution of hydrologic export to bulk soil turnover rates across the continental USA. The catchment area weighted average of hydrologic export effect on SOC turnover was 5.2%. Hydrologic export accounted for 0-2% of the bulk SOC turnover in arid regions, 2-15% - in forests, and 20-40% - in wetland-rich areas. The SOC stocks generated for the continental U.S. using microbe-mediated turnover alone amounted to 88.3 Pg C and were 15.4% higher than the amount reported in the Harmonized World Soil Database (76.5 Pg C), thus illustrating the importance of accounting for hydrologic C export when simulating SOC dynamics.
The level of hydrodynamic drag as a main component in explaining concentrations of nutrients and particle loads at different heights of a fisheries trawl plume
Authors: Breimann Sarah , O'Neill Barry , Stinchcombe Mark , Mayor Daniel
Published: March 2020

Shelf sea ecosystems are amongst the most productive on Earth. A large proportion of the nutrients required to sustain this productivity is supplied via the remineralization of organic material in the underlying sediments. Industrial fisheries trawling at the seafloor, the most intense form of anthropogenic disturbance in shelf seas, has the potential to influence the release of sediment and nutrients from the seafloor and hence shelf-scale primary production. However, the absence of data on the concentrations and composition of the materials resuspended by benthic trawling hinders our ability to robustly assess the wider ecosystem effects of this industrial activity. We addressed this key knowledge gap by conducting the first in-situ experiments to quantify the concentrations of particles and nutrients released by different benthic trawling gears.

Our results demonstrate that the composition of resuspended particles and nutrients are both influenced by sampling height above the seafloor and the amount of drag exerted by the trawl gear, although the relative importance of these factors differs between the two response variables examined. These differences likely reflect that sediment particles adhere to physical laws of a solid in a fluid with associated weights, while dissolved nutrients follow the physical laws of fluids and dilution.  

Our findings demonstrate that trawl gear design strongly influences the amount of dissolved and particulate material resuspended. This suggests that gear design could be modified to reduce the impacts on shelf ecosystems. Future work will upscale our observations to assess the potential effects of benthic trawling activities on primary production at the shelf-scale.
A breakdown of the link between the Arctic and North Atlantic Oscillations in warm climate projections
Authors: Hamouda Mostafa , Pasquero Claudia , Tziperman Eli
Published: March 2020

The North Atlantic Oscillation (NAO) and the Arctic Oscillation (AO) are climate variability modes significantly affecting temperature and precipitation variability in the mid-latitudes of the Northern hemisphere. In this study, we use both reanalysis data and model historical and warmer climate simulations to show that the relation between the two oscillations may change dramatically in a different climate. In the current climate, these two climate modes are highly correlated, as they are both strongly influenced by downward propagation of stratospheric anomalies into the troposphere. When considering a warmer climate scenario (RCP8.5 in the XXIII century), the correlation between NAO and AO drops significantly, revealing that they become two separate modes of variability. The stratosphere remains an important precursor for NAO, while the AO consistently precede stratospheric anomalies. The analysis suggests that these changes are owed to land-sea thermal contrast intensification in the Pacific region, which becomes more favorable for storm variability.