bluuebunny/crossref_metadata_2025 huggingface dataset:
Macrobenthos richness and biomass preferentially geared towards one half of asymmetrical sand waves
Authors: Cheng Chiu , Borsje Bas , O'Flynn Sarah , Beauchard Olivier , Ysebaert Tom , Soetaert Karline
Published: March 2020

Sand waves are dynamic, sinusoidal bedforms that have been thoroughly studied in the context of the physical and hydrodynamical processes dominating these environments. However, information about the ecological and biogeochemical characteristics within these bedform habitats have been far fewer in comparison. To address this knowledge gap, a field campaign was undertaken in the summer of 2017 to investigate the biogeomorphology of asymmetrical sand waves in the Dutch North Sea, near island Texel. The goal was specifically to address both the macrofaunal community composition and the associated biogeochemistry along the different sections of these sand waves.  Using a combination of several field sampling techniques and lab incubations on board the NIOZ RV-Pelagia, we collected a comprehensive dataset covering the macrofauna assemblage, nutrient flux, oxygen consumption, sediment grain size and permeability, as well as physical and environmental data, within a transect line (< 1 km) that covered several sand waves. Here, we show considerable variability in the species abundance, composition and biomass, which were all significantly higher on the steeper sides of the sand waves; the multivariate statistical analyses on the datasets showed a significant influence of the sand wave position on benthic composition. Correspondingly, measurements from the steep slopes also exhibited a higher concentration of chl-a and organic matter, higher O2 consumption, more fine particles and lower sediment permeability. Despite the overall homogeneity (e.g., sandy sediment) of a well-developed bedform environment such as a sand wave field, it is clearly possible to find significant variations in the benthic community composition and biogeochemical activity on a small spatial scale.  Oftentimes, studies look at larger spatial scales to maximize the characterization of an entire region. However, given the diverse environmental gradients within the North Sea, our observations may not be sufficiently captured or even missed altogether when superimposed upon such large spatial scales.  Thus, a close examination of the interrelated parameters such as biology, biogeochemistry, sedimentology and morphology should also be considered, at a high resolution, over a small local scale for such seemingly uniform habitats.  We hope our results will contribute valuable insight into small-scale patterns of variability in dynamic bedform environments. 
Meridional distribution of moisture transport associated to Tropical Cyclones
Authors: Peano Daniele , Scoccimarro Enrico , Bellucci Alessio , Roberts Malcolm , Cherchi Annalisa , D'Anca Alessandro , Antonio Fabrizio , Fiore Sandro , Gualdi Silvio
Published: March 2020

Tropical cyclones (TCs) transport energy and moisture along their pathways interacting with the climate system and TCs activities are expected to extend further poleward during the 21st century.

For this reason, it is important to assess the ability of state-of-the-art climate models in reproducing an accurate meridional distribution of TCs as well as a reasonable meridional portrait of moisture transport associated with TCs.

Since high resolutions are required to reconstruct observed TCs activity, the present work is based on the simulations performed as part of HighResMIP in the framework of the community CMIP6 effort. To inspect this feature, two horizontal resolutions for each climate model are considered. Besides, the impact of boundary conditions, i.e. observed ocean surface state, is examined by considering both coupled and atmosphere-only configurations.

In the present work, the north Atlantic region is analyzed as a sample region, while the same approach is applied on a multi-basin basis. In the sample area, climate models present a good ability in reproducing the TCs distribution, with a general underestimation at lower latitudes and a slight overestimation at high-latitudes compared to observed TCs tracks (e.g. IBTRACK).

The meridional distribution of moisture transport associated with TCs is evaluated by considering the radial average of the integrated water vapor transport along the TC tracks. When compared to observation (IBTRACS and JRA-55 reanalysis), the simulated moisture transport associated with TCs displays reasonably good performance in atmosphere-only high-resolution models configuration. The interannual variability of water vapor associated with TCs, instead, is poorly represented in climate models.

Climate models in high-resolution configuration can then be used in estimating future TCs meridional distribution and changes in meridional moisture transport associated with TCs.

This effort is part of HighResMIP and it is developed in the framework of the EU-funded PRIMAVERA project.   
Pedoclimatic comparison of three viticultural areas of Italy devoted to high-quality Aglianico and Cabernet Sauvignon production
Authors: Monaco Eugenia , De Mascellis Roberto , Barbato Giuliana , Mercogliano Paola , Buonanno Maurizio , Brook Anna , De Micco Veronica , Bonfante Antonello
Published: March 2020

In the Mediterranean area, the expected increase in temperature coupled with the decrease in rainfall, as well as the increase in the frequency of extreme events (heatwaves and drought, IPCC, 2019), will severely affect the survival of current vineyard areas. Cultivar thermal requirement and soil water availability could be not satisfied, leading to a limitation in yield and berry quality also due to constraints in the achievement of optimal grape maturity.

In this context, the understanding of how the spatial viticultural suitability will change under climate change is of primary interest in order to identify the best adaptation strategies to guarantee the resilience of current viticultural areas. Moreover, the improvement of knowledge of climate, soil, and their interaction for each specific cultivar will be fundamental because the terroir system is based on this interaction able to influence the plant status (e.g., water).

In this study, different pedo-climatic conditions (past, present, and future) in three Italian sites at different latitudes (from center to southern), were compared for two red varieties of grapevine: Aglianico (indigenous cv) and Cabernet Sauvignon (international cv).

Grapevine adaptation to future climate in each experimental farm in Campania, Molise, and Sicily Italian regions has been realized through the use of bioclimatic indexes (e.g., Amerine & Winkler for Aglianico 2110 GDD). The climatic evaluation was performed using Regional Climate Model COSMO-CLM at high-resolution (8km x 8km) climate projections RCP4.5 and RCP 8.5 (2010-2100) and Reference Climate (RC, 1971-2005).

Results have shown how climate change will affect the cultivation of Aglianico and Cabernet Sauvignon, considering both the climate and bioclimatic needs of cultivars themselves in the current viticultural areas.

Finally, coupled with the climatic evaluation, a pedological survey to characterize the soils, and the analysis of satellite images (Sentinel2 ) coupled with stemwood anatomical analysis has been performed to reconstruct the past eco-physiological behavior.
Visualizing models and observations of the thermosphere-ionosphere in support of the ESA EE10 candidate mission Daedalus
Authors: Doornbos Eelco , Sarris Theodoros , Tourgaidis Stylianos , Pirnaris Panagiotis , Buchert Stephan , Liu Hanli , Lu Gang , Gasperini Federico
Published: March 2020

Daedalus is a new satellite mission concept for studying the lower thermosphere-ionosphere (LTI). The mission is currently undergoing Phase 0 studies, funded by ESA as one of three missions that are candidates for becoming its Earth Explorer 10 mission (EE10).

Using an elliptical orbit with a very low perigee (140 km and lower), the mission will make comprehensive in-situ measurements, including local density, composition, temperature and velocities of both the neutral and charged particles. An option of having two Daedalus satellites is being studied to allow better separation of temporal and spatial variability, and to better measure the strong vertical gradients and wave activity that occur in the LTI. The complete suite of instruments on Daedalus will allow the computation of higher level products such as local collision frequencies, conductivities and heating rates, along the orbit. The unique complementarity of instrumentation and orbit sampling over a large range of altitudes will be extremely valuable in advancing the science of the LTI region, which is a key region for many space weather phenomena.

High quality visualizations of models and data are very important during the definition of the mission. They allow both experts and newcomers to the field to better comprehend the physics of the LTI region, how it couples with other regions and systems, as well as how Daedalus will be able to sample this region from its unconventional orbit. The presentation will showcase 2D and 3D visuals that were developed during the phase 0 studies, and that make use of empirical and physics-based models of the thermosphere-ionosphere, Earth's magnetic field and simulated satellite orbits.
Diagnosing temperature sensitivity of respiration at multiple spatial scale in the northern high-latitude regions
Authors: Wu Dongxing , Liu Shaomin , Xu Ziwei , Yang Xiaofan , Wu Xiuchen , Xu Tongren , Shi Hanyu
Published: March 2020

Accurate estimation of the temperature sensitivity of respiration (Q10) is important for understanding terrestrial ecosystem carbon cycle and its response to climate change, especially in the northern high-latitude regions (NHL). The conventional calculation of temperature sensitivity contain seasonal confounding effects on annual temporal scale. The scale-dependent parameter estimation (SCAPE) method which is based on singular spectral analysis could circumvent confounding effects. However, the process of screening a series of high frequency subsignals to identify the best intrinsic Q10 produce large error. In this study, we proposed the SCAPE-M method to improve the approach of screening high frequency subsignals. Three datasets were used to validate the SCAPE-M method in the NHL, namely FLUXNET2015 datasets, MsTMIP multi-model weighted average outputs, and ERA_interim reanalysis data. The main results were as follows: (1) On the site scale, the confounding effects in the forest ecosystems were less than grassland and cropland ecosystems in the NHL. The apparent Q10 derived from conventional approach differed among biomes in the NHL and increased with annual mean temperature. The mean apparent Q10 across 36 FLUXNET sites in the NHL was 2.71 ± 0.77. Contrary to the results of apparent Q10, the intrinsic Q10 across 36 FLUXNET sites in the NHL were independent of annual mean temperature, and were confined to values around 1.54 ± 0.38. (2) On the grid scale, the apparent Q10 increased with annual mean temperature, with high values in the Western Europe and low values in the Mongolian Plateau. There were no significant changes of intrinsic Q10 in the spatial distribution. While the convergence value 1.01 ± 0.15 on the grid scale was smaller than the site scale. The results in this study indicated that the response of carbon cycle to climate warming in the NHL was less pronounced than suggested by most carbon cycle climate models.
The Webcam around Mars: Supporting Science with the Mars Express Visual Monitoring Camera
Authors: Ravanis Eleni , Hernández-Bernal Jorge , Cardesín-Moinelo Alejandro , Sánchez-Lavega Agustín , del Río-Gaztelurrutia Teresa , Hueso Ricardo , Wood Simon , Titov Dmitrij , Almeida Miguel , Marin-Yaseli de la Parra Julia , Merritt Donald , Grotheer Emmanuel , Breitfellner Michel , Castillo Manuel , Martin Patrick
Published: March 2020

The Visual Monitoring Camera (VMC), or “the ESA Mars Webcam” on board ESA’s Mars Express (MEX) orbiter was originally designed as an engineering camera whose purpose was to monitor the separation of the Beagle-2 lander in 2003. Later, in 2007, the camera was switched on again for outreach purposes, with images regularly posted to Twitter (@esamarswebcam) and Flickr. Following the subsequent use of VMC data for Mars atmospheric science (Sánchez-Lavega et al., AAS/DPS, 48, 2016; Sánchez-Lavega et al., Icarus 299, 194-205, 2018) the VMC was designated a scientific instrument in 2016. No on-ground calibration exists for the VMC, so the VMC team have had to take initiative in order to perform in-flight calibration of the instrument. New observation planning procedures have been developed, as well as a new data processing pipeline hosted at the European Space Astronomy Centre (ESAC) in Madrid to maximise the scientific return of the instrument. The data is currently in the process of being archived in the Planetary Science Archive, for its wider use by the community.

The MEX Science Ground Segment (SGS) team at ESAC maintains close collaboration with the VMC science team located at the University of the Basque Country (UPV-EHU) in Bilbao. The scientific studies undertaken with VMC camera data include monitoring of the global dust storm over the south pole in 2018 (Hernández-Bernal et al., J. Geophys. Res. Lett., 46, 10330–10337, 2019), analysis of twilight clouds (Hernández-Bernal et al., EPSC, 12, 2018), discovery of a seasonally recurrent double cyclone in the northern latitudes of Mars (Sánchez-Lavega et al., J. Geophys. Res., 123, 3020, 2018) and studies of an extremely elongated cloud over Arsia Mons (Hernández-Bernal et al., EGU, 2020). The scientific success of this “webcam” around Mars highlights how small cameras on planetary missions can yield high science return, which has implications for potential future CubeSat missions to Mars.
N2O-based climatology of the Brewer-Dobson Circulation in WACCM, a chemical reanalysis and a CTM driven by four dynamical reanalyses
Authors: Minganti Daniele , Chabrillat Simon , Christophe Yves , Errrera Quentin , Abalos Marta , Prignon Maxime , Kinnison Douglas , Mahieu Emmanuel
Published: March 2020

The Brewer-Dobson Circulation (BDC) plays a major role in the stratospheric dynamics in terms of tracer transport through the mean residual meridional advection and the isentropic 2-way mixing.
The climatological BDC in the Whole Atmosphere Community Climate Model (WACCM) is separated in its components and evaluated through a comparison with a chemical reanalysis of the Aura Microwave Limb Sounder version 2 (BRAM2) and with a chemistry-transport model driven by four modern reanalyses (ERA-Interim, JRA-55, MERRA and MERRA2). The BDC seasonal means and climatological annual cycle are addressed using the Transformed Eulerian Mean (TEM) analysis of the long-lived tracer N2O. The N2O TEM budget terms considered in this study are the vertical residual advection and the horizontal two-way mixing terms.
WACCM presents a general underestimation of the horizontal mixing term in the wintertime Northern Hemisphere with respect to the reanalyses throughout the stratosphere.In the wintertime antarctic region the mid-low stratospheric horizontal mixing term in WACCM does not agree with the reanalyses: it shows near-zero positive values, while all the reanalyses show a consistent negative contribution. This disagreement between WACCM and the reanalyses is located in the region and period of the polar vortex development, and can be related to a different representation of the polar jet. In this region the reanalyses are nevertheless affected by large uncertanties of the TEM analysis: the residual term of the budget has the same magnitude as the horizontal mixing term.Even though the residual term can be interpreted as the effect of sub-grid mixing processes, caution must be exerted when considering these regions because the N2O TEM budget is not completetely closed.
The mid-stratospheric arctic region are characterized by smaller uncertanties of the TEM budget together with large differences among the datasets during winter: the WACCM realizations, characterized by a large internal variability, show a smaller horizontal mixing contribution with respect to the reanalyses.
The agreement among datasets is generally improved when considering the middle and low latitudes, especially in the Northern Hemisphere: those regions are characterized by smaller differences among datasets and a well-closed TEM budget.
The inter-annual variability of the horizontal mixing term and the vertical advection term is highly latitude-dependent: the horizontal mixing term presents a large variability, together with a large dataset spread, in the antarctic region in the austral fall and during boreal winter in the Arctic; the vertical advection shows large variability in the arctic region and large model spread in the Tropical regions.
An efficient cellular flow model for cohesive particle flocculation in turbulence
Authors: Zhao Kunpeng , Vowinckel Bernhard , Hsu Tian-Jian , Köllner Thomas , Bai Bofeng , Meiburg Eckart
Published: March 2020

We propose a one-way coupled model that tracks individual primary particles in a conceptually simple cellular flow setup to predict flocculation in turbulence. This computationally efficient model accounts for Stokes drag, lubrication, cohesive and direct contact forces on the primary spherical particles and allows for a systematic simulation campaign that yields the transient mean floc size as a function of the governing dimensionless parameters. The simulations reproduce the growth of the cohesive flocs with time and the emergence of a log-normal equilibrium distribution governed by the balance of aggregation and breakage. Flocculation proceeds most rapidly when the Stokes number of the primary particles is O(1). Results from this simple computational model are consistent with experimental observations, thus allowing us to propose a new analytical flocculation model that yields improved agreement with experimental data, especially during the transient stages.
Understanding what to account for and what to ignore in the design of distributed hydrological models
Authors: Fenicia Fabrizio , Dal Molin Marco
Published: March 2020

Designing a distributed rainfall-runoff model requires many not obvious decisions, such as whether to include regional groundwater flow, whether to account for the spatial variability of topography, geology, soils and vegetation, and at which spatial resolution to resolve model inputs. Typically, the effect of such decisions is determined a posteriori, for example based on sensitivity analyses, with the disadvantage that if a decision is poorly made, it is necessary to restart the model development from the conceptualization stage, which is a time consuming process. We here show that a more effective strategy is to base such decisions on a preliminary analysis of the available data, hence by “looking at data first”. In particular, similarly to what done in catchment classification studies, we start by identifying potential climatic and landscape controls on streamflow signatures. These insights are subsequently used to inform model decisions such as the ones above described. This approach is illustrated in the Thur catchment in Switzerland (1702 km2), with 10 sub-catchments. The catchment shows a large variability in streamflow, climatic, and landscape characteristics. Results demonstrate that precipitation (quantity and type) is the main control of the water balance and of streamflow seasonality; geological features control the partition of the fluxes between baseflow and quick flow; other catchment characteristics are not of primary importance in determining streamflow variability. The present study, that conjugates some aspects of catchment classification with hydrological modelling, represents a step forward in understanding catchment dominant processes at the large scale and in designing a procedure for constructing distributed hydrological models with limited complexity.
Effects of an abrupt depth change on weakly nonlinear surface gravity waves: deterministic and stochastic analysis
Authors: Li Yan , Draycott Samuel , Zheng Yaokun , Adcock Thomas A.A. , Lin Zhiliang , van den Bremer Ton S.
Published: March 2020

This work focuses on two different aspects of the effect of an abrupt depth transition on weakly nonlinear surface gravity waves: deterministic and stochastic. It is known that the kurtosis of waves can reach a maximum near the top of such abrupt depth transitions. The analysis is based on three different approaches: (1) a novel theoretical framework that allows for narrow-banded surface waves experiencing a step-type seabed, correct to the second order in wave steepness; (2) experimental observations; and (3) a numerical model based on a fully nonlinear potential flow solver. To reveal the fundamental physics, the evolution of a wave envelope that experiences an abrupt depth transition is examined in detail; (a) we show the release of free waves at second order in wave steepness both for the super-harmonic and sub-harmonic or ‘mean’ terms; (b) a local wave height peak that occurs near the top of a depth transition – whose exact position depends on several nondimensional parameters – is revealed; (c) furthermore, we examine which parameters affect this peak. The novel physics has implications for wave statistics for long-crested irregular waves experiencing an abrupt depth transition. We show the connection of the second-order physics at work in the deterministic and stochastic cases: the peak of wave kurtosis and skewness occurs in the neighborhood of the deterministic wave peak in (b) and for the same parameters set composed of a seabed topography, water depths, primary wave frequency and steepness, and bandwidth.
Glacio-eustatic variability in the sedimentation pattern over northern Japan during the past 600 ka
Authors: Barik Sushree Sova , Singh Raj K. , Upadhyaya Pratik K. , Biswal Lisantaraj , Vats Nishant , Das Manisha
Published: March 2020

The Japan Sea is a semi-enclosed marginal sea affected by global sea-level fluctuation, expansion of seasonal and permanent sea-ice cover, having a significant influence on the regional climate neighboring Japan Sea. Middle Pleistocene to Holocene sediments of the Integrated Ocean Drilling Program site U1423 situated in the northeastern part of Japan Sea was processed for the grain size analysis, semi-quantitative mineral analysis, and clay mineral analysis to access glacio-eustatic control on sedimentation pattern over Japan Sea during the past 610 ka. The average time resolution per sample is ~10 kyr. The mean grain size data suggest the dominance of silt size fraction over the sand and clay. The end member modeling of grain size data suggests the presence of two different energy conditions that varied with the time and influenced by the glacio-eustatic changes over the Japan Sea. The grain size data are relatively coarser and deposited in the higher energy condition during the glacial periods in comparison to interglacial periods except for MIS 2, 4, and 8. The higher energy condition during the glacial intervals suggesting deposition of grains due to the melting of seasonal/permanent ice sheets in the northern Japan Sea. The eolian dust brought from the Chinese loess deposits are relative finer in size and dominated by a higher proportion of quartz. During the glacial phases, illite and kaolinite (%) show a decreasing trend than the interglacial phases suggesting less terrigenous input. The high illite and decreased smectite (%) during interglacial phases suggest a higher degree of physical weathering. The significant increase in the smectite/(illite+chlorite) ratio suggests a higher degree of chemical weathering of the nearby source area, which varied over time. The overall study suggests the phase-wise variability in the presence of permanent/seasonal ice sheets and East Aian Winter Monsoon strength during the past 600 ka.
Integration of Machine Learning on Distributed Acoustic Sensing Surveys
Authors: Jestin Camille , Hibert Clément , Calbris Gaëtan , Lanticq Vincent
Published: March 2020

Distributed Acoustic Sensing (DAS) is an innovative technique which has been recently employed for near-surface geophysics purposes. It involves the use of fibre-optic cable as a sensor. The fibre is analysed by sending a laser pulse from an interrogator unit. The phase of the backscattered signal contains the information on the strain on the cable, enabling the detection of a passing acoustic wave with enough energy for the cable excitation. Allowing the interrogation of long profiles and the generation of a dense spatial sampling, uneasy to obtain with classic geophysical techniques, DAS instrumentation then proved its relevance for seismic applications but also for infrastructure monitoring.

During DAS acquisition, and more precisely when closely looking at infrastructures integrity, it is necessary to clearly identify the source of the acoustic vibrations at the structure neighbourhood. Indeed, in the context of pipeline monitoring for example, it appears important to be able to classify events which generate seismic signals recorded by DAS systems and which can be related to a potential threat for the structure. In order to launch an alarm if necessary, the source identification must be fast, accurate and robust. Moreover, because DAS acquisition can generate traces every few meters along fibres of tens of kilometres, the used machine-learning algorithm must demonstrate its ability to handle a big amount of data.

In this study, we analyse the efficiency of the Random Forests (RF) machine-learning algorithm applied to data acquired with DAS system for the discrimination of event sources. RF algorithm has been selected because of its ability to handle large numbers of attributes related to signal characteristics and to enable a good reliability for the discrimination of sources. This algorithm has already proved its efficiency for automated classification of seismic waveforms (e.g. earthquakes, volcanic tremors, rock falls, avalanches, etc.).

We focus our study on tests lead along a gas pipeline instrumented with fibre-optic cable. Different third-party works have been conducted: excavation, saw sections, drill, jackhammer, etc. We work on the discrimination of six classes of seismic source. After running a detection phase based on a threshold on signal energy, we obtain several hundred of exploitable seismic traces to inject to the RF algorithm. We demonstrate the efficiency of the application of machine learning on DAS data to discriminate seismic waveforms from the correct class, with an overall precision on our test set of 99%.
Raikoke aerosol clouds observed from Tbilisi, Georgia and Halle, Belgium using ground-based twilight sky brightness spectral measurements.
Authors: Mateshvili Nina , Fussen Didier , Mateshvili Iuri , Vanhellemont Filip , Bingen Christine , Paatashvili Tamar , Kyrölä Erkki , Robert Charles , Dekemper Emmanuel
Published: March 2020

Raikoke volcano (Kuril Islands, Russia) eruption on 21 June 2019 sent an ash plume at 10-13 km altitude, which is higher than the local tropopause.  Volcanic aerosols were transported around the globe, causing spectacular purple twilights. We will present ground-based measurements of monochromatic twilight sky brightnesses at 780 nm wavelength in two geographical points: Tbilisi, Georgia (41° 43’ N, 44° 47° E) and Halle, Belgium (50° 44′ N, 4° 14′ E).  Aerosol extinction vertical profiles in the lower stratosphere-upper troposphere were retrieved with the help of the Levenberg–Marquardt algorithm. Monte Carlo code Siro was used to design a forward model. Raikoke aerosols observed above the both sites have shown essentially cloudy and variable structure. Multiple layers were observed between 10 and 17 km with extinction up to 0.01 km-1.  We will present Raikoke aerosol cloud evolution in the period July 2019 –January 2020.
Major environmental and ecological shifts in late Holocene marine sediments of the NW Adriatic Sea
Authors: Berensmeier Michaela , Tomašových Adam , Martin Zuschin
Published: March 2020

Sediments of the NW Adriatic Sea preserve important information about environmental changes during the Holocene and due to recent anthropogenic impact. This study is based on new data of a 3-m-long gravity core taken from 31 m water depth. Large environmental and ecological shifts are indicated by changes in geochemistry (XRF core scanning data, geochemical bulk analyses) and molluscan composition, particularly in the uppermost decimeters.

Sedimentologically, the record can be divided into 4 facies types: (1) laminated silty sediments with some sands, terrestrial plant remains, and scarce mollusc shells (at 175-300 cm sediment depth), (2) bioturbated silty, fine-sandy sediments with terrestrial plant remains, scarce mollusc shells, and calcirhizomes (70-175 cm), (3) strongly bioturbated, clayey silt with increasing abundance in mollusc shells (20-70 cm), and (4) clayey silt with a peak in molluscan shell abundances and diversity, with abundant bivalves (Corbula gibba) and gastropods (Turritellinella tricarinata, 0-20 cm).

Corbula gibba valves were used for C14-calibrated amino acid racemization (AAR) analyses of valves. The resulting shell ages show a bisection in the record: (1) an uppermost, surface-mixed layer with very young shells (median age = 50 years) and (2) an age-homogeneous composition down to 30 cm sediment depth (median age = 3000 years). This downcore shift in age distributions probably indicates that the 20th century shells of Corbula gibba are not mixed beyond 10 cm. This pattern implies decreasing bioturbation and increasing sedimentation in the study area in the 20th century.
Pore connectivity across scales and resolutions
Authors: Lucas Maik , Vetterlein Doris , Vogel Hans-Jörg , Schlüter Steffen
Published: March 2020

An important parameter to quantify pore structure and link it to soil functions is connectivity. When quantifying connectivity with X-ray microtomography (X-ray-µCT), one of the major drawbacks is that high resolution can only be achieved in small samples. In these samples, the small pores can be described, but the connectivity of larger pores cannot be quantified reasonably.

Here we explore changes in pore connectivity with changing sample size covering a range of analyzed pore diameters of more than three orders of magnitude. Soil columns with a diameter of 10 cm were taken in two different depths (0 - 20 cm and 40 - 60 cm) at different sites of an agricultural chronosequence ranging in age from 0 to 24 years. X-ray CT was used for scanning the original columns as well as undisturbed subsamples of 3 and 0.7 cm diameter. This enabled us to detect characteristic traces in certain connectivity metrics on the chronosequence, caused by different pore types and thus different processes. In detail, we determined the connection probability of two random points within the pore system, i.e. the Γ-indicator and the Euler number, χ as a function of minimum pore diameter.

Our results revealed that scale artifacts in the connectivity functions overlap with characteristic signatures of certain pore types. For the very first time a new method for a joint-Γ-curve was developed that merges information from three samples sizes, as the Γ-indicator gives highly biased information in small samples. In contrast, χ does not require such a scale fusion and is helpful to define characteristic size ranges for pore types. Overall, findings suggest a joint evaluation of both connectivity metrics to identify the contribution of different pore types to the total pore connectivity with Γ and to disentangle different pore types with χ.

For the samples of the chronosequence such an evaluation revealed that biopores mainly connect pores of diameters between 0.1 and 0.5 mm. However, this was not necessarily coupled with increasing porosity. Tillage, conversely, lead to an increase in porosity due to a shift of pores of diameter >0.05 mm towards pores of diameter >0.20 mm and therefore increased connectivity of pores >0.20 mm.

The current study is part of the DFG-Project Soil Structure (AOBJ: 628683). 
A direct measurement of water vapor at Europa and implications for the magnetospheric environment
Authors: Roth Lorenz , Paganini Lucas , Villanueva Geronimo , Mandell Avi , Hurford Terry , Mumma Michael , Retherford Kurt , Blöcker Aljona
Published: March 2020

Previous investigations suggested local anomalies in Europa’s atmosphere, advancing the idea of possible water plumes. Now a global survey with the Keck observatory provided a direct detection (3.1 sigma) of line emission from H2O at infrared wavelengths on one out of 17 observing dates in 2016 and 2017. The non-detections on the 16 other dates resulted in sensitive upper limits for H2O abundance at various longitudes, providing reference to the rate and location of occurrence.

When active, outgassing at plumes locally increases the neutral density in Europa’s bound atmosphere. Such atmosphere anomalies in turn might lead to small scale (compared to Europa’s diameter) features in the electromagnetic interaction signals such as in magnetic field perturbations, or to an increased mass loss from Europa. The strength and detectability of plume-related magnetospheric signals depend on the relative abundance of plume gas (when active) compared to the sputtered atmosphere.

The new results from the infrared survey suggest that outgassing occurs at lower levels than previously estimated, with only rare localized events of somewhat stronger plume activity. In this presentation, we put these observations in context and discuss if and how plume activity might affect the magnetospheric environment.
Paleoflooding and paleoclimate of the Lower Meuse during the Allerød-early Holocene
Authors: Peng Fei , Kasse Cornelis , Prins Maarten , Van der Woude John , Van der Putten Nathalie , Woolderink Hessel , Troelstra Simon , Beets Christiaan , Van Balen Ronald
Published: March 2020

Lateglacial climatic oscillations exerted profound impacts on the earth surface. In the Lower Meuse Valley (southern Netherlands), geomorphological studies in the last decades mainly centered on Lateglacial vegetation evolution, channel pattern changes and river terrace formation. Little information has been reported with respect to the paleohydrology and its relation with local and regional climate system. This study investigates a sediment core that contains flood sediments deposited from the Allerød to the middleHolocene. We conducted grain-size analysis, thermogravimetric analysis (organic matter and calcium carbonate content), pollen counting, macro fossils analysis, and oxygen and carbon stable isotopes analysis of the biogenic carbonate. Plant species variations in each pollen assemblage zone represent the local and regional vegetation development. The pollen and macro fossil studies reveal that the core site was in a lake and marsh environment through the Allerød-early Holocene period. The oxygen isotope record is believed to have captured the intra-Allerød Cold Period, its synchronous variation with the carbon isotope record indicates a dominant evaporation effect on the lake during the warm Allerød period. By highlighting the coarser components (flood signal) of the fine and coarse end members, two flooding energy indexes were constructed separately. The hydrological processes in the first phase of the Younger Dryas were characterized by rapidly increased flooding conditions and high accumulation rates. In the second phase of the Younger Dryas, an addition of aeolian sediments to the core site complicates the paleoflood identification. This work expands the paleoflooding reconstruction to a more broadly deposition setting where only fine or coarse fluvial sediment is the dominant component. The nearly synchronous changes of the increased flooding with the abruptly enhanced westerlies at the Allerød-Younger Dryas transition indicates a link between the Lower Meuse catchment and the regional North Atlantic climatic system
Numerical Modeling of Nonlinear Interactions of Spectral Components of Acoustic-Gravity Waves in the Middle and Upper Atmosphere
Authors: Gavrilov Nikolai M. , Kshevetskii Sergej P.
Published: March 2020

Acoustic-gravity waves (AGWs) measuring at big heights may be generated in the troposphere and propagate upwards. A high-resolution three-dimensional numerical model was developed for simulating nonlinear AGWs propagating from the ground to the upper atmosphere. The model algorithms are based on the finite-difference analogues of the main conservation laws. This methodology let us obtaining the physically correct generalized wave solutions of the nonlinear equations. Horizontally moving sinusoidal structures of vertical velocity on the ground are used for the AGW excitation in the model. Numerical simulations were made in an atmospheric region having horizontal dimensions up to several thousand kilometers and the height extention up to 500 km. Vertical distributions of the mean temperature, density, molecular viscosity and thermal conductivity are specified using standard models of the atmosphere.

Simulations were made for different horizontal wavelengths, amplitudes and speeds of the wave sources at the ground. After “switch on” the tropospheric wave source, an initial AGW pulse very quickly (for several minutes) could propagate to heights up to 100 km and above. AGW amplitudes increase with height and waves may break down in the middle and upper atmosphere. Wave instability and dissipation may lead to formations of wave accelerations of the mean flow and to producing wave-induced jet flows in the middle and upper atmosphere. Nonlinear interactions may lead to instabilities of the initial wave and to the creation of smaller-scale perturbations. These perturbations may increase temperature and wind gradients and could enhance the wave energy dissipation.

In this study, the wave sources contain a superposition of two AGW modes with different periods, wavelengths and phase speeds. Longer-period AGW modes served as the background conditions for the shorter-period wave modes. Thus, the larger-scale AGWs can modulate amplitudes of small-scale waves. In particular, interactions of two wave modes could sharp vertical temperature gradients and make easier the wave breaking and generating  turbulence. On the other hand, small-wave wave modes might increase dissipation and modify the larger-scale modes.This study was partially supported by the Russian Basic Research Foundation (# 17-05-00458).
Diagnosing factors in parameterised and resolved convection with physical tendency output in AROME-Arctic during a Cold-Air Outbreak event
Authors: Kähnert Marvin , Valkonen Teresa M. , Sodemann Harald
Published: March 2020

Numerical weather prediction (NWP) models generally display comparatively low predictive skill in the Arctic. Particularly, the large impact of sub-grid scale, parameterised processes, such as surface fluxes, radiation or cloud microphysics during high-latitude weather events pose a substantial challenge for numerical modelling. Such processes are most influential during mesoscale weather events, such as polar lows, often embedded in cold air outbreaks (CAO), some of which cause high impact weather. Uncertainty in Arctic weather forecasts is thus critically dependent on parameterised processes. The strong influence from several parameterised processes also makes model forecasts particularly susceptible to compensation of errors from different parameterisations, which potentially limits model improvement.
Here we analyse model output of individual parameterised tendencies of wind, temperature and humidity during Arctic high-impact weather in AROME-Arctic, the operational NWP model used by the Norwegian Meteorological Institute Norway for the European Arctic. Individual tendencies describe the contribution of each applied physical parameterisation to a respective variable per model time step. We study a CAO-event taking place during 24 - 27 December 2015. This intense and widespread CAO event, reaching from the Fram Straight to Norway and affecting a particularly large portion of the Nordic seas at a time, was characterised by strong heat fluxes along the sea ice edge. 
Model intern definitions for boundary layer type become apparent as a decisive factor in tendency contributions. Especially the interplay between the dual mass flux and the turbulence scheme is of essence here. Furthermore, sensitivity experiments, featuring a run without shallow convection and a run with a new statistical cloud scheme, show how a physically similar result is obtained by substantially different tendencies in the model.
Global Flood Model: Revolutionising Flood Catastrophe Modelling
Authors: Dunning Paul , Styles Kirsty , Evans Daniel , Hutchings Stephen
Published: March 2020

Catastrophe models are well established tools, traditionally used by the re/insurance industry to assess the financial risk to insured property (“exposure”) associated with natural perils. Catastrophe modelling is challenging, particularly for flood perils over large geographical scales, for a number of reasons. To adequately capture the fine spatial variability of flood depth, a flood catastrophe model must be of high spatial resolution. To validly compare estimates of risk obtained from catastrophe models for different geographical regions, those models must be built from geographically consistent data. To compare estimates of risk between any given collection of geographical regions globally, global coverage is required.

Traditional catastrophe models struggle to meet these requirements; compromises are made, often for performance reasons.  In addition, traditional models are typically static datasets, built in a discrete process prior to their use in exposure risk assessment. Scientific assumptions are therefore deeply embedded; there is little scope for the end user to adjust the model based on their own scientific knowledge.

This research presents a new and better approach to catastrophe modelling that addresses these challenges and, in doing so, has allowed creation of the world’s first global flood catastrophe model.

JBA’s Global Flood Model is facilitated by a technological breakthrough in the form of JBA’s FLY Technology. The innovations encoded in FLY have enabled JBA to create a model capable of consistent global probabilistic flood risk assessment, operating at 30m resolution and supported by a catalogue of 15 million distinct flood events (both river and surface water). FLY brings a model to life dynamically, from raw flood hazard data, simultaneously addressing the user configurability and performance challenges.

Global Flood Model and FLY Technology will be of interest to those involved in financial, economic or humanitarian risk assessment, particularly in and between countries and regions not covered by flood catastrophe models to date. The detail of how they work will be covered here, and their power in facilitating consistent global flood risk assessment will be demonstrated.
Natural time analysis: Estimation of the occurrence time of a major earthquake from the entropy changes of the preceding seismicity.
Authors: Skordas Efthimios S , Sarlis Nicholas V. , Lazaridou-Varotsos Mary S , Varotsos Panayiotis A
Published: March 2020

By analyzing the seismicity in the new time domain termed natural time [1],  the entropy changes of seismicity before major earthquakes have been studied. It was found [2-5] that the key quantity is the entropy change ΔS under time reversal, which is minimized a few months before major earthquakes such as the M9.0 Tohoku earthquake [2] on 11 March 2011 and the M8.2 Chiapas earthquake [3] in Mexico on 7 September 2017; accompanied by an abrupt increase of its fluctuations [4,5]. Here we discuss how these fluctuations may lead to a procedure through which the occurrence time of an impending mainshock can be estimated [6].

References

1. Varotsos P.A., Sarlis N.V. and Skordas E.S., Natural Time Analysis: The new view of time. Precursory Seismic Electric Signals, Earthquakes and other Complex Time-Series (Springer-Verlag, Berlin Heidelberg) 2011.

2. N. V. Sarlis, E. S. Skordas, and P. A. Varotsos, "A remarkable change of the entropy of seismicity in natural time under time reversal before the super-giant M9 Tohoku earthquake on 11 March 2011", EPL (Europhysics Letters), 124 (2018), 29001.

3. N. V. Sarlis, E. S. Skordas P. A. Varotsos, A. Ramírez-Rojas, E. L. Flores-Márquez, "Natural time analysis: On the deadly Mexico M8.2 earthquake on 7 September 2017", Physica A 506 (2018), 625-634.

4. P. A. Varotsos, N. V. Sarlis and E. S. Skordas, "Tsallis Entropy Index q and the Complexity Measure of Seismicity in Natural Time under Time Reversal before the M9 Tohoku Earthquake in 2011", Entropy 20 (2018), 757.

5. A. Ramírez-Rojas, E. L. Flores-Márquez, N. V. Sarlis and P. A. Varotsos, "The Complexity Measures Associated with the Fluctuations of the Entropy in Natural Time before the Deadly México M8.2 Earthquake on 7 September 2017", Entropy 20 (2018), 477.

6. E. S. Skordas, N. V. Sarlis and P. A. Varotsos “Identifying the occurrence time of an impending major earthquake by means of the fluctuations of the entropy change under time reversal”, EPL (Europhysics Letters), in press.
The Holocene volcanism of El Hierro, Canary Islands
Authors: Rodríguez-González Alejandro , Aulinas Meritxell , Perez-Torrado Francisco José , Criado Hernández Constantino , Cabrera Maria del Carmen , Fernandez-Turiel Jose-Luis
Published: March 2020

El Hierro is, together with La Palma, the youngest island of the Canarian Archipelago. Both islands are in the shield stage of their volcanic growth, which implies a high volcanic activity during the Holocene period. The submarine eruption occurred in October 2011 in the SSE rift of El Hierro evidenced the active volcanic character of the island. Even so, despite the numerous scientific works published following the submarine eruption (most of them centered to understand such volcanic event), there is still a lack of precise knowledge about the Holocene subaerial volcanism of this island. The LAJIAL Project focuses on solving this knowledge gap.

The Holocene subaerial volcanism of El Hierro generates fields of monogenetic volcanoes linked to the three systems of rifts present on the island. Its eruptive mechanisms are typically Strombolian although there are also phreato-Strombolian events. The most recent eruptions frequently form lava on coastal platforms, which are considered after the last glacial maximum (approx. 20 ka BP). The most developed coastal platforms in El Hierro are at the ends of the rifts and in the interior of the El Golfo depression. This geomorphological criterion shows that more than thirty subaerial eruptions have taken place in El Hierro since approx. 20 ka BP. In addition, there are many apparently recent volcanic edifices far from the coast.

The research of the most recent volcanism of the island, the last 11,700 years of the Holocene, covers a long enough period whereas it is close to the present day. Thus, this period is the best to model the eruptive processes that will allow us to evaluate the future scenarios of the eruptive dynamics in El Hierro. The Project LAJIAL combines methodologies of geological mapping, geomorphology, GIS, chronostratigraphy, paleomagnetism, petrology and geochemistry to solve the Holocene eruptive recurrence rate in El Hierro, and to constrain the rift model of intraplate ocean volcanic islands.

Financial support was provided by the Project LAJIAL (ref. PGC2018-101027-B-I00, MCIU/AEI/FEDER, EU). This study was carried out in the framework of the Research Consolidated Groups GEOVOL (Canary Islands Government, ULPGC) and GEOPAM (Generalitat de Catalunya, 2017 SGR 1494).