bluuebunny/crossref_metadata_2025 huggingface dataset:
Exploring the effects of a time- and space-dependent eruption efficiency on planetary evolution.
Authors: Arts Mara
Published: March 2020

It has been shown that melting and crust production strongly influences the convection regime of terrestrial planets, potentially even more than the vigor of convection. A planet producing and erupting a lot of crust can hardly remain in the stagnant lid regime and produces resurfacings or even reaches some mobile-lid regime. On the other hand, a planet that intrudes its melt in the lithosphere tends to have a larger conductive heat flux and cools efficiently without much lid mobility. Thus, the question of the amount of melts being erupted or intruded might dominate the cooling of terrestrial planets. So far, an "eruption efficiency", which gives the ratio of melt that erupts over the remaining melt fraction, has been imposed in numerical simulations. The eruption efficiency in the convection code StagYY has thus far been treated as a constant in time and space. Here, we explore the effects of a time- and space-dependent eruption efficiency on planetary evolution in the planetary convection code StagYY. An equation was devised that describes how eruptive a system is, based on the main characteristics of lithospheric melt transport: the amount of melt and the local stress state. In a range of systematic simulations, we explore the consequences of this parameter. 

In a first set of simulations this parameter is explored while keeping the eruption efficiency constant. Results show that the most important parameters are the amount of melt, where the stress has smaller local effects. Additionally, changing the yield stress, viscosity or constant eruption efficiency has a large effect on what the eruptivity should be based on this equation. Parameters that govern the global mantle temperature are less important for the eruptivity. 

A second set of simulations was performed with the eruption efficiency behaving in a fully self-consistent manner. These models tend to behave like intrusive systems, except during resurfacing episodes when the models become very extrusive. Models that show mobile behaviour at almost all times in the planetary evolution will have an almost constant spatially averaged eruption efficiency. In these models the eruption efficiency does vary locally however.
Air-Sea Fluxes following the Unusually Early Ice Retreats in the Arctic
Authors: Zhang Dongxiao , Zhang Chidong , Cross Jessica , Mordy Calvin , Cokelet Edward , Gentemann Chelle , Chiodi Andy , Stabeno Phyllis , Jenkins Richard , Meinig Christian , Lawrence-Slava Noah , Tabisola Heather , Wang Muyin
Published: March 2020

The Arctic has been rapidly changing over the last decade, with more frequent unusually early ice retreats in late spring and summer. Vast Arctic areas that were usually covered by sea ice are now exposed to the atmosphere because of earlier ice retreat and later arrival. Assessment of consequential changes in the energy cycle of the Arctic and their potential feedback to the variability of Arctic sea ice and marine ecosystems critically depends on the accuracy of surface flux estimates. In the Pacific sector of the Arctic, earlier ice retreat generally follows the warm Pacific water inflow into the Arctic through the Bering and Chukchi Seas. Due to ice coverage and irregularity of seasonal ice retreats, air-sea flux measurements following the ice retreats has been difficult to plan and execute. A recent technology development is the Unmanned Surface Vehicles (USVs): The long-range USV saildrones are powered by green energy with wind for propulsion and solar energy for instrumentation and vehicle control. NOAA/PMEL and University of Washington scientists have made surface measurements of the ocean and atmosphere in the Pacific Arctic using saildrones for the past several years. In 2019, for the 1st time a fleet of six saildrones capable of measuring both turbulent and radiative heat fluxes, wind stress, air-sea CO2 flux and upper ocean currents was deployed to follow the ice retreat from May to October, with five of the USVs into the Chukchi and Beaufort Seas while one staying in the Bering Sea. These in situ measurements provide rare opportunities of estimating air-sea energy fluxes during a period of rapid reduction in Arctic sea ice in different scenarios: open water after ice melt, free-floating ice bands, and marginal ice zones. In this study, Arctic air-sea heat and momentum fluxes measured by the saildrones are compared to gridded flux products based on satellite data and numerical models to investigate the circumstances under which they agree and differ, and the main sources of their discrepancies. The results will quantify the uncertainty margins in the gridded flux products and provide insights needed to improve their accuracy. We will also discuss the feasibility of using USVs in sustained Arctic observing system to collect benchmark datasets of the changing surface energy fluxes due to rapid sea ice reduction and provide real time data for improved weather and ocean forecasts.  
VEgetation NUtrient-retention Service (VENUS) index: an indicator to assess favourable conditions for nutrient retention by vegetation.
Authors: Murgese Davide
Published: March 2020

Ecosystems role in preserving water resources is acknowledged by EU Water Framework Directive 2000/60/EC and by Groundwater Directive 2006/118/EC. In this view nutrient concentration represent a critical aspect with regard to water quality and eutrophication. Nitrate pollution is specifically addressed by the Nitrate Directive 91/676/EEC, which provides nitrate management rules for farming activities, defines nitrate vulnerable zones and gives indications on nitrate monitoring in water bodies.

To preserve water quality levels an important role is played by Riparian Buffer Zones (RBZ) through the provision of the Ecosystem Service (ES) nutrient retention, the uptake process operated by plant roots. Research has shown how ES valuation is a very effective approach to support land management process, as it allows a better understanding of the importance of the role of ecosystems in guaranteeing wellbeing conditions for human communities and for the environment.

In order to perform a complete assessment of ES, the use of maps only providing information on processes occurring at/above the surface (e.g land use maps, or ecosystem maps, or ecosystem function maps) does not allow a complete analysis of underground dynamics.

In the case of the valuation of the ES “nutrient retention” provided by RBZ it is necessary to include the hydrogeological model and its links with the riverine network. The simple presence/absence of vegetation, or even a detailed vegetation classification map, cannot provide a complete description of all conditions required to fully assess this ES, as information on groundwater flow, sediments and soils characteristics is needed.

For the Riparian Vegetation Management Plan of the Gesso Stura Riverine Park a specific index to study vegetation contribution to nutrient retention was introduced: the VEgetation NUtrient-retention Service (VENUS) Index. This index provides land managers a semi-quantitative indication on the spatial distribution of “best conditions” (suitability map) for nutrient retention by vegetation; it is based on a simple set of parameters representing the main factors controlling the interactions between vegetation roots and water flows (runoff and groundwater) from surrounding areas towards water bodies.

The application of the VENUS Index improved the definition of management measures for riparian vegetation and allowed reaching the following results: (1) identification of homogeneous sectors in terms of RBZ relevance for nutrient retention; (2) assessment of different RBZ management scenarios with regard to nutrient retention performance; (3) definition of specific management measures to preserve and/or foster the provision of nutrient retention.
Flood risk assessment and cultural heritage impact in the Instituto Superior de Arte (ISA) in Habana.
Authors: Bignami Daniele Fabrizio , Stucchi Leonardo , Bocchiola Daniele , Zecchin Christian , Del Curto Davide , Garzulino Andrea , Rosso Renzo
Published: March 2020

Keeping ISA Modern is a project of Fondazione Politecnico di Milano and other partners aimed at planning the conservation of some of the buildings (Schools) of the University of Arts (ISA) of Cuba, built over a former country club, designed by eminent architects of the time (Vittorio Garatti, Roberto Gottardi and Ricardo Porro), and bestowed with the status of UNESCO World Heritage in 2003.

Most of the Schools are currently unusable, also due to damages caused by frequent floods from the surrounding Rio Quibù river, and they need urgent restoration if they are to be used. Personnel of Politecnico di Milano carried out a field survey on the Rio Quibù during 2019, and also based upon information from the Cuban National Institute of Hydraulic Resources (INRH) they studied established flood risk for ISA.

Here, we built a high-resolution digital terrain model (DTM) of the park where Schools are located, using laser scanner data, and previously georeferenced points. Using field measurements taken in June 2019 we were able to assess geometry (included bridges), slope and roughness coefficients of the main channel of the Quibù river, influence of the sea level. Then using as input critical discharge data provided by INRH we evaluated flood area and flood volume for 4 representative return periods (5, 20, 50, 100 years).

The most impacted building is the School of Ballet, located within a narrow meander of Rio Quibù, immediately upstream of a narrow bridge, clogging largely during floods, only 1 km far from the sea, and with drainage system unable to discharge storm water.

Given the high required cost, a partially collapsed wall originally partially protecting the School of Ballet was not rebuilt, and we are now exploring flood mitigation strategy which are cheaper, and feasible from the point of view of compatibility with the historical and architectural value of the building.
Feeding preference of cockchafer populations and response of oak regeneration: a case study in Germany
Authors: Dounavi Aikaterini , Creyaufmüller Frederike Caroline , Chassignet Isabelle , Leinemann Ludger , Delb Horst , Gailing Oliver , Kreuzwieser Juergen , Teply-Szymanski Julia , Vornam Barbara
Published: March 2020

In view of climate change the risk of biotic stressors in the forests is expected to be enhanced in addition to severe abiotic stress events, like drought. One biotic stress considered to be increased for oak regeneration is the root feeding of young plants from cockchafer. The cockchafers (Melolontha spp.) belong to the scarab beetles (Scarabaeidae) and are widespread pest species throughout Central Europe. In Germany, the most common species is the European cockchafer (Melolontha melolontha Linnaeus), whereby the forest cockchafer (Melolontha hippocastani Fabricius) is also present, mainly on sandy soils. Specifically, in south-western Germany both European and forest cockchafers cause economic losses in agricultural and forest areas. Besides drought, the feeding of roots from cockchafer larvae, act as an additional stress factor for young oak plants. In the present case study, geographically distant oak stands are infested with different intensity.

In the present study, population genetic analysis was used to differentiate the two cockchafer species and was used to estimate population dynamics, as well as possible consequences of climatic changes to the life cycle of forest cockchafer. Additionally, seedlings of two distant oak provenances were exposed to forest cockchafer larvae in a greenhouse experiment and their population genetic and root-based VOC profiles were studied. Larvae preferences for the different plants/populations were estimated and terpene synthase gene expression of the plants was measured.

Chloroplast haplotypes showed patterns of migration from different refugial regions. However, no clear association between genetic constitution of the different provenances and the abundance of cockchafer populations on site was observed. TPS gene expression patterns in response to larval feeding revealed geographic variation rather than genotypic variation. Our results support the assumption that root-released VOC are influencing the perception of roots by herbivores.
Health Risk Assessments of Arsenic and Toxic Heavy Metals Exposure in Drinking Water in Central Gangetic Plain, Uttar Pradesh
Authors: Yadav Shailesh kumar , Ramanathan Alagappan
Published: March 2020

The current study was focused on the characterization of recharge, weathering processes and to check the aptness of groundwater for household and agriculture utility in the Central Gangetic Plain, Uttar Pradesh, India. Arsenic contamination in groundwater recognized as a vital catastrophic problem that affect millions of people across the world and have geogenic as well as anthropogenic sources. In central gangetic, plain, high geogenic arsenic in groundwater is extensively present in Holocene alluvial aquifers. The severity of this problem is further accelerated through in-situ physio-chemical factors in the fluvial environment. In our studied areas, newer alluvium has organic rich clay, which plays an important role in arsenic mobilization by reductive dissolution of Fe-oxyhydroxide. The aim of this paper is to compare and contrast the long-term similarities and differences in arsenic hot spot regions in central gangetic plain with those of other parts of the world and assess the unique socio-cultural factors that determine the human health risks of exposure to arsenic in local groundwater. It documents how the pathways of exposure to this poison have been greatly expanded through intensive application of groundwater in agriculture in the region within the Green Revolution framework.
Faulted geological contacts: constraining uncertainty of discontinuities orientation using triangulation and combinatorial algorithm
Authors: Michalak Michał , Kuzak Ryszard , Gładki Paweł , Kulawik Agnieszka
Published: March 2020

Subsurface information is usually a limited resource in geological modelling. This is not the case, however, for the Kraków-Silesian Homocline in central Poland. It was subject to rapid exploitation of ore-bearing clays in the second half of the 20th century. Exhaustive geological documentation remained after this activity had ceased and it contains thousands of borehole records. A small part of this resource has recently been incorporated to propose a new method for determining the dominant orientation of a selected geological contact. This new method regarded Delaunay triangles as source of local orientations that were then analyzed on stereonets. The geological contacts in this region are inclined gently towards NE, but they are also faulted and indicate some stratigraphic noise which makes the extraction of dominant orientation a challenging task.

It is still unknown, however, to which extent the proposed modelling approach is capable of detecting faults and calculating their orientation. This is particularly important for the introduction of a new method for the recognition of faults based on investigating spatial distribution of orientation patterns. This expert-guided methodology assumes to relate orientation trends with genetic trends and investigate them on 2D maps.

In this research, we built synthetic models of faulted contacts to observe the behaviour of triangles intersecting the fault surface. To observe the variability of the orientation at larger scale, and perhaps to constrain it at the same time, we applied a combinatorial algorithm for creating all three-element subsets from an n-element set. The employment of this combinatorial approach allowed to achieve a better clustering effect around the expected orientation. The limitation of the proposed approach can be attributed to some unexpected and unintuitive orientations. Compared to previous studies these singularities seem to be geometrical and not numerical in nature.
Methods for the analysis of asbestos in incoherent soils
Authors: Zanetti Giovanna , Marini Paola , Baietto Oliviero
Published: March 2020

Soils contaminated with asbestos, whether of natural origin or deriving from anthropogenic pollution, can have very different dimensional, chemical and humidity characteristics.

The legal limit that allows to define an asbestos contaminated soil is a concentration of 1000 mg / kg of asbestos fibers, as per DLGS 152/2006. The analytical methods suggested in Italy by regulation (DM 6/09/94) for the determination of asbestos content are Diffrattometry (XRD) and  Fourier Transform Infrared (FTIR), methods that do not allow to distinguish the fibrous material and secondly Scanning Electron Microscopy (SEM). The Phase Contrast Optical Microscopy (PCOM) is considered a methodology only useful for a qualitative analysis for it low rilevability index (0,1 mm in respect of   for SEM and    for XRD and FTIR).

The goal of this study is to describe the cheap and quick soil analysis methodology used in the Asbestos laboratory of DIATI Politecnico di Torino where also the representativeness of the analysed quantity of material is considered.

When the sample is an incoherent soil, sieving (at 0.6 - 0.3 – 0.150-0.075 mm) after drying is carried out. The asbestos fibers eventually present in the classes >0.6 mm and 0.6-0.3 mm, that are visible with a low magnification (5-10 x), can be recovered by flotation and weighted after drying. The quantitative analysis of the classes 0.3-0.075 is perfomed by means of PCOM, measuring the dimensions of the fibers, hipotyzing the third dimension equal to the width and calculating the weight knowing the density of the asbestos fiber observed.  .The presence of asbestos in the finer particle size class can be verified by SEM, but is the asbestos content in the other particle size classes is high the value obtained for the finer class is generally found to be irrelevant to the final result.If the initial sample has a very fine particle size, it is homogenized by grinding and is prepared for reading under the SEM by depositing a known quantity on a polycarbonate membrane. The results thus obtained are referred to the analysis of at least 100 g of material.

The reliability of the technique has been verified by participating in interlaboratory circuits.

 
Excitation of San Andreas tremors by thermal instabilities below the seismogenic zone
Authors: Wang Lifeng , Barbot Sylvain
Published: March 2020

The relative motion of tectonic plates is accommodated at boundary faults through slow and fast ruptures that encompass a wide range of source properties. Near the Parkfield segment of the San Andreas fault, deep tremors and slow slip take place deeper than most seismicity, at temperature conditions typically associated with stable sliding, which should inhibit stick slip. However, laboratory experiments indicate that the strength of granitic gouge decreases with increasing temperature above 350$^\circ$C, providing a possible mechanism for weakening if temperature is to vary dynamically. Here, we argue that recurring tremor and slip at these depths may arise due to shear heating and the temperature dependence of frictional resistance and contact healing. Assuming a lower thermal diffusivity in the fault zone than in the surrounding rocks, numerical simulations can explain the recurrence pattern of the mid-crustal tremors and their correlative slip distribution, predicting peak temperatures exceeding the solidus of wet granite during sliding. We conclude that shear heating associated with slow slip can be sufficient to generate pseudotachylyte injection veins in host rocks even when fault slip is domin.
Hydropower in the Era of Climate Change. The Case of the Sabbione Storage Plant in Italy
Authors: Stucchi Leonardo , Bombelli Giovanni Martino , Bocchiola Daniele
Published: March 2020

Hydropower, between renewable energy sources, is probably the best candidate for reducing greenhouse emission, since it is the only renewable energy source whose production can be adapted to demand, and still has a large exploitation margin, especially in developing countries. However, in Europe the contribution of hydropower from the cold water in the mountain areas is at stake under rapid cryospheric down wasting under global warming. Italian Alps are no exception, with a large share of hydropower depending upon cryospheric water. We study here climate change impact on the iconic Sabbione (Hosandorn) glacier, in the Piemonte region of Italy, and the homonymous reservoir, which collects water from ice melt. Sabbione storage plant has operated since 1953 and it was, until recently, the highest altitude dam of Europe at 2460 m asl. Using two models, namely Poly-Hydro and Poly-Power, we assessed present hydrological budget divided by components (i.e., ice/snow melt, rainfall), and hydropower production under optimal reservoirs’ management, respectively. We then project forward hydrological cycle under properly downscaled climate change scenarios (three General Circulation Models, three Representative Concentration Pathways, nine scenarios overall) from IPCC until 2100, and we assess glacier fate and consequences for hydropower production. Mean annual discharge during 2000–2017 is estimated at 0.90 m3 s−1, with ice melt contribution of ca. 11.5%, and ice cover as measured by remote sensing changing from 4.23 km2 in 2000 to 2.94 km2 in 2017 (−30%). Mean hydropower production during 2005–2017 is estimated as 46.6 GWh. At the end of the century ice covered area would be largely depleted (0–0.37 km2), and ice melt contribution would drop largely over the century (-10% to 0%, 5% on average at half century, and null in practice at the end of century). Therefore, decreased ice cover, and uncertain patterns of changing precipitation, would combine to modify the future stream fluxes (−22% to −3%, −10% on average at half century, and −28% to 1%, average −13%, at the end of century). Power production, driven by seasonal demand and water availability, would change (decrease) in the future (−27% to −8%, −15% on average at half century, and −32% to −5%, −16% at the end of century). Our results demonstrate potential for decrease of cold water in this area, paradigmatic of the present state of hydropower in the Alps, and subsequent considerable hydropower losses under climate change, and claim for adaptation measures therein.
Oxygen isotopes of individual planktic foraminifers reveal Pliocene-Pleistocene change of seasonal upper ocean stratification in the northern South China Sea
Authors: Zhao Ning , Vonhof Hubert , Giosan Liviu , Schiebel Ralf , Haug Gerald
Published: March 2020

Most paleoceanographic studies using planktic foraminifera focus on annual means, but seasonal signals buried by the analyses of lumped specimens could be very valuable. Surface ocean feedbacks on climate change may be more significant in the seasonal realm than annual mean in the northern South China Sea, a region being strongly affected by Asian monsoons and tropical cyclones. Here we use oxygen isotope measurements on individual specimens of surface and subsurface planktic foraminiferal species to reconstruct surface seasonality and seasonal upper ocean stratification in this region. Many studies have shown that the thermocline was deeper in the tropical Pacific during the Pliocene than the Pleistocene, but the mechanism remains unclear. Several processes could lead to changes in the upper ocean stratification, such as changes in sea surface temperature and upper ocean mixing by tropical cyclones. Our results show that the upper ocean stratification was weaker during the Late Pliocene than the Early Pleistocene, with the change more significant in summer than winter, while no systematic offset is observed in the surface seasonality. The observations suggest that enhanced mixing by tropical cyclones might be the major cause of the deeper thermocline during the Pliocene.
Deep neural networks to downscale ocean climate models
Authors: Déchelle-Marquet Marie , Levy Marina , Gallinari Patrick , Crepon Michel , Thiria Sylvie
Published: March 2020

Ocean currents are a major source of impact on climate variability, through the heat transport they induce for instance. Ocean climate models have quite low resolution of about 50 km. Several dynamical processes such as instabilities and filaments which have a scale of 1km have a strong influence on the ocean state. We propose to observe and model these fine scale effects by a combination of satellite high resolution SST observations (1km resolution, daily observations) and mesoscale resolution altimetry observations (10km resolution, weekly observations) with deep neural networks. Whereas the downscaling of climate models has been commonly addressed with assimilation approaches, in the last few years neural networks emerged as powerful multi-scale analysis method. Besides, the large amount of available oceanic data makes attractive the use of deep learning to bridge the gap between scales variability.

This study aims at reconstructing the multi-scale variability of oceanic fields, based on the high resolution NATL60 model of ocean observations at different spatial resolutions: low-resolution sea surface height (SSH) and high resolution SST. As the link between residual neural networks and dynamical systems has recently been established, such a network is trained in a supervised way to reconstruct the high variability of SSH and ocean currents at submesoscale (a few kilometers). To ensure the conservation of physical aspects in the model outputs, physical knowledge is incorporated into the deep learning models training. Different validation methods are investigated and the model outputs are tested with regards to their physical plausibility. The method performance is discussed and compared to other baselines (namely convolutional neural network). The generalization of the proposed method on different ocean variables such as sea surface chlorophyll or sea surface salinity is also examined.
Interpretability of Quaternary palaeo dune fields (Eastern Canary Islands)
Authors: Roettig Christopher-B. , Kolb Thomas , Schmidt Christoph , Zöller Ludwig , Faust Dominik
Published: March 2020

Generally, the Quaternary palaeo dune fields on the Eastern Canary Islands are built up by different dune generations which are seperated by reddish silty layers. The biogenic carbonate sands originate from the shallow marine shelf around the islands and reach the dune fields from northern direction.

On northern Fuerteventura different lava flows were formed during the Late Pleistocene, and gradually interrupted the sand pathways of the dune fields close to the western coast. The sedimentation pattern in these dune fields indicates that this cut off was completed not later than 50 ka. A huge calcium carbonate crust in the outcrops marks the stratigraphic position of that final cut off. This crust was a subject of intensive debates, and was formerly linked to unstable environmental conditions. However, within the dune fields on the neigbouring island Lanzarote we did not find a comparable carbonate crust at the similar stratigraphic position. Instead, the El Jable dune field on northwestern Lanzarote shows a well-resolved dune sequence with intercalated silty layers during that period.

Consequently, the dune fields on the Eastern Canary Islands point to the importance of carbonate sand transport as the main driving force within the sediment system. Finally we can conclude that unimpaired sand pathways are a mandatory prerequisite for the buildup of palaeoclimatic signals in the Quaternary dune archives.
Current knowledge and future perspectives on soil drying and rewetting, by the scientific community
Authors: Brangarí Albert C. , Hicks Lettice , Leizeaga Ainara , Rousk Johannes
Published: March 2020

Drying and rewetting events induce enormous dynamics in soil biogeochemistry, known as the “Birch effect”. A series of laboratory studies have shown that during this phenomenon, respiration and microbial growth are uncoupled. In addition, it has been found that soil microorganisms exhibit one of two different response-patterns, the dynamics of which are strongly regulated by the harshness of the moisture disturbance experienced by soil microbes. Despite the potential significance of these responses for the global carbon cycle, the characteristics and mechanisms underlying them are still unclear.

In order to shed some light on the current status of research in this field, we will present the outcomes of an international workshop organized in Lund in November 2019. During it, we integrated researchers from different environments in order to identify knowledge-gaps and tackle outstanding and new challenges in this field. We will review the characteristics of the growth and respiration responses to moisture fluctuations and the putative mechanisms and factors governing them. We will also discuss the advantages of combining empirical and modelling approaches by using our own group experience as a case example.
Monitoring climate-driven and anthropogenic impacts on hydrology and agriculture in South-Eastern Australia in the 21st century
Authors: Schumacher Maike , Forootan Ehsan , Crosbie Russell , Mallschützke Theresa , Rothermel Jonas
Published: March 2020

With the climate change, drought events likely become more frequent and severe in Australia, where the worst droughts were recorded during the 21st century. Particularly, in the South-East of the country, the so called "Millennium Drought" showed below average annual precipitation for an entire decade. The precipitation record was then increased by extreme precipitation events generated from the La Niña events in 2010 and 2011. Afterwards, dry conditions began again to develop. The climate-driven events and anthropogenic adaptions to the circumstances resulted in strong impacts on the hydrological resources and agricultural production. In fact, simulating hydrological processes within the (semi-)arid region of South-East Australia is very challenging especially during extreme events. In previous studies, we found a strong underestimation of the decline of total terrestrial water storage (TWS) and of groundwater in comparison to remote sensing data and in-situ station networks. Thus, we successfully calibrated the W3RA water balance model and simultaneously assimilated TWS anomalies obtained from the Gravity Recovery And Climate Experiment (GRACE) satellite mission to improve the model's skill during extreme meteorological conditions. In this presentation, we focus on the comparison of remote sensing observations and W3RA simulations after implementing the calibration and data assimilation with existing data records on anthropogenic intervention into the water cycle, as well as on agricultural production. Our results indicate high correlations between meteorological, hydrological and agricultural variables, and we observe strong similarities in the long-term trends and break points.
Conductive anomalies related to the Mérida Andes derived from the 3D inversion of a magnetotelluric profile
Authors: Cruces José , Ritter Oliver , Weckmann Ute , Tietze Kristina , Schmitz Michael
Published: March 2020

Abstract

The geodynamic settings of north-western Venezuela are conditioned by the expulsion of the North Andean Block (NAB), and the deformational structures related to the Caribbean – South America plate interactions. The most prominent feature is the 100 km wide Mérida Andes (MA) that reach from the Colombian border to the Caribbean coast over more than 500 km. We present the analysis of a magnetotelluric (MT) profile acquired at 72 broadband sites along a 240 km long profile with station spacing between 3 and 5 km across the central part of the MA, including the sedimentary Maracaibo (MB) and Barinas-Apure (BAB) basins. Phase Tensors (PT) are consistent with 1D/2D dimensionality above the MB and the BAB, however, stations above the MA show a clear 3D dimensionality, with the induction vectors indicating the presence of off-profile structures. Following the dimensionality analysis, 3D inversions of the entire dataset were performed, employing the finite differences code ModEM. The results are in agreement with prominent geological structures, and are particularly effective in modelling the depth extensions of major fault systems. A conductive structure east from the profile at mid crustal levels seems to correlate with the tectonic escape of the Trujillo block, which is part of the NAB.
Soil systems as critical infrastructure: do we know enough about soil system resilience and vulnerability to secure our soils?
Authors: Davies Jessica , Batista Pedro , Janes-Bassett Victoria , O'Riordan Roisin , Quinton John , Yumashev Dmitry
Published: March 2020

Soils provide us with multiple essential services, such as food production, water flow regulation, and climate regulation. The loss of soil function endangers provision of these services, in turn endangering the local, regional and global societies and economies that rely on these. Soils, therefore, are in effect a critical infrastructure, which can be defined as an asset, system or process, the loss or compromise of which could result in a major detrimental impact on the availability, integrity or delivery of essential services, with significant economic or social impacts. Conceptualising soil as a critical infrastructure changes the way we as a society need to approach its management. For example, government authorities have a responsibility to reduce the vulnerability of critical infrastructure, and strengthen their security and resilience. To meet this responsibility there is a need to assess infrastructure resilience, identify critical vulnerabilities, and identify and implement strategies for increasing resilience. There has been growing interest and research on soil resilience, particularly drawing on ecological resilience concepts. In this contribution, we will consider our current understanding of soil system resilience from a critical infrastructure perspective and discuss where further science is needed.
Can the Budyko framework and satellite data help improve hydrological modeling in ungauged and poorly monitored catchments? The case study of the Lurín catchment in Peru
Authors: Bondy Jan , Zehe Erwin , Wienhöfer Jan
Published: March 2020

Predictions in ungauged basins still present one of the major challenges in hydrology. In many cases, the absence of a stream gauge also implies a low density of the meteorological monitoring network in these catchments and surroundings as well as little available data on water management infrastructure and agricultural consumptions. This combination creates a circle of uncertainties and thus individual influences of relevant water balance components are difficult to disentangle and quantify. 

The original Budyko curve presents a very general model that yields, to first order, an estimate of the steady-state water balance of a catchment at the climatological scale, assuming its landscape and functioning has evolved naturally and free of anthropogenic interferences. Even at smaller time scales, the Budyko relationship allows approximating the water partitioning in the catchment, and thus helps correct erroneous assumptions[JW1]  or missing information about for instance unknown human-induced alterations. On the other hand, an increasing variety of global remote-sensing data products is becoming available providing spatial estimates of land surface properties such as for instance vegetation indexes or soil moisture. Even if the predictive power of such products in terms of absolute values remains questionable, it is possible to derive coarse spatial patterns or temporal dynamics to narrow down zones and orders of magnitude of interferences with the natural hydrological cycle such as reservoirs or irrigated lands. This study combines these two general approaches in order to improve hydrological modelling and system understanding of the semi-arid Lurín catchment in the Western Andes of Peru.
Localized magnetic field structures and their boundaries in the near-Sun solar wind from Parker Solar Probe measurements
Authors: Krasnoselskikh Vladimir ,   PSP Magnetic Structures
Published: March 2020

One of the most striking discoveries made by Parker Solar Probe during its ﬁrst three encounters with the Sun is the presence of a multitude of relatively small-scale structures that stand out as sudden deﬂections of the magnetic. They were named “switchbacks” since some of them show up the full reversal of the radial component of the magnetic ﬁeld and return to “regular” solar wind conditions. We carried out an analysis of three typical switchback structures having slightly diﬀerent characteristics: I. Alfv´enic structures, where the variations of the magnetic ﬁeld components take place conserving the magnitude of the magnetic ﬁeld constant; II. Compressional, where the magnetic ﬁeld magnitude varies together with changes of the components of the magnetic ﬁeld; III. Structures manifesting full reversal of the magnetic ﬁeld, they may be presumably similar to Alfv´enic, but they are some extremal class of “switchback structures”. We analyzed the properties of the magnetic ﬁeld of these structures and the characteristics of their boundaries. Our observations and analysis lead to the conclusion that the structures represent localized magnetic ﬁeld tubes moving with respect to surrounding plasma. The very important characteristic of these tubes consists of the existence of a relatively narrow boundary layer on the surface of the tube that accommodates ﬂowing currents. These currents supposedly closed on the surface of the structure, and typically they have comparable azimuthal and the tube axes aligned components. These currents are supported by the presence of the eﬀective electric ﬁeld ensured by quite strong gradients of the density, and ion plasma pressure. The ion beta is typically larger than one inside the structure, and less than one outside. Another important feature is an electromagnetic wave accommodated on the surface of the structure. Its role consists in assistance to particles in carrying currents, to electrons parallel to magnetic ﬁeld, and perpendicular to ﬁeld to ions.
GGOS Focus Area on Geodetic Space Weather Research – Current Status
Authors: Schmidt Michael , Forootan Ehsan
Published: March 2020

Space weather means a very up-to-date and interdisciplinary field of research. It describes physical processes in space mainly caused by the Sun’s radiation of energy. The manifestations of space weather are multiple, for instance, the variations of the Earth’s magnetic field or the changing states of the upper atmosphere, in particular the ionosphere and the thermosphere.

The main objectives of the Focus Area on Geodetic Space Weather Research (FA GSWR) are (1) the development of improved ionosphere models, (2) the development of improved thermosphere models and (3) the study of the coupled processes between magnetosphere, ionosphere and thermosphere (MIT). 

Objective (1) aims at the high-precision and the high-resolution (spatial and temporal) modelling of the electron density. This allows to compute a signal propagation delay, which will be used in many geodetic applications, in particular in positioning, navigation and timing (PNT). Moreover, it is also important for other techniques using electromagnetic waves, such as satellite- or radio-communications. Concerning objective (2), satellite geodesy will obviously benefit when working on Precise Orbit Determination (POD), but there are further technical matters like collision analysis or re-entry calculation, which will become more reliable when using high-precision and high-resolution thermospheric drag models. Objective (3) links the magnetosphere with the first two objectives by introducing physical laws and principles such as continuity, energy and momentum equations and solving partial differential equations.     

To arrive at the above described objectives of the FA GSWR one new Joint Study Groups (JSG) and three Joint Working Groups (JWG) have been installed recently. In detail, these groups are titled as JSG 1: Coupling processes between magnetosphere, thermosphere and ionosphere, JWG 1: Electron density modelling, JWG 2: Improvement of thermosphere models, and JWG 3: Improved understanding of space weather events and their monitoring by satellite missions. Other implemented IAG Study and Working Groups within the IAG programme 2019 to 2023 will provide valuable input for the FA GSWR. In this presentation we provide the latest investigations and results from the above mentioned Joint Study and Working Groups JSG 1, JWG 1, JWG 2 and JWG 3 of the FA GSWR.
Deconstructing the subtropical AMOC variability
Authors: Jamet Quentin , Dewar William , Wienders Nicolas , Deremble Bruno , Close Sally , Penduff Thierry
Published: March 2020

Mechanisms driving the North Atlantic Meridional Overturning Circulation (AMOC) variability at low-frequency are of central interest for accurate climate predictions. However, the origin of this variability remains under debate, complicating for instance the interpretation of the observed time series provided by the RAPID-MOCHA-WBTS program. In this study, we aim at disentangling the respective contribution of the local atmospheric forcing, the signal of remote origin and the ocean intrinsic dynamics for the subtropical low-frequency AMOC variability. We analyse for this a set of four ensembles of a regional (20oS - 55oN), eddy-resolving (1/12o) North Atlantic oceanic configuration, where surface forcing and open boundary conditions are alternatively permuted from fully varying (realistic) to yearly repeating signals.

The analysis of the four ensemble mean AMOCs reveals predominance of local, atmospherically forced signal at interannual time scales (2-10 years), while signals imposed by the boundaries imprint at decadal (10-30 years) time scales. Due to this marked time scale separation, we show that most of the subtropical AMOC forced variability can be understood as a linear superposition of these two signals. Analyzing the ensemble spread of the four ensembles, we then show that the subtropical AMOC is also characterized by an intrinsic variability, which organizes as a basin scale mode peaking at interannual time scales. This basin scale mode is found to be weakly sensitive to the surrounding forced signals, suggesting no causal relationship between the two. Its spatio-temporal pattern shares however similarities with the atmospherically forced signal, which is likely to make the attribution from a single eddy-resolving simulation, or from observations, more difficult.
CONDE: Climate simulation ON DEmand using HPCaaS
Authors: Pérez Montes Diego A. , Añel Juan A. , Rodeiro Javier
Published: March 2020

CONDE (Climate simulation ON DEmand) is the final result of our work and research about climate and meteorological simulations over an HPC as a Service (HPCaaS) model. On our architecture we run very large climate ensemble simulations using a, adapted, WRF version that is executed on-demand and that can be deployed over different Cloud Computing environments (like Amazon Web Services, Microsoft Azure or Google Cloud) and that uses BOINC as middleware for the tasks execution and results gathering. Here, we also present as well some basic examples of applications and experiments to verify that the simulations ran in our system are correct and show valid results. 
Intensive CO2 and CH4 measurement campaign at Mexico-City
Authors: Ramonet Michel , Taquet Noémie , Grutter Michel ,   MERCI-CO2
Published: March 2020

Mexico City (MC) is the home of 21.2M people, 19% of the country's population. The MC urban area has intense emissions of pollutants and greenhouse gases, which accumulate in the overlying air-shed due to the location of the city in a high-altitude basin surrounded by mountains. Local and national authorities have engaged into aggressive emission reduction strategies. The Mexican-French collaborative project, MERCI-CO2, aims to develop atmospheric CO2 measurements that will enable, with the support of atmospheric inversion, to verify the effectiveness of CO2 emission reductions taken by the city authorities. The MERCI-CO2 combines high-precision analysers and low-cost sensors for surface measurements with total column observations up- and down-wind of MC. In addition to the long-term infrastructure currently deployed, an intensive campaign in the spring 2020 will produce an unprecedented data set. For this campaign we will deploy during one month six EM27 spectrometers for total column CO2, CH4 and CO observations; two high-precision analyzer at fixed position and one on board a car for transect measurements; and ten low-cost CO2 sensors which will be setup at air quality stations from the local city network measuring CO, NOx and O3. The dense network will be deployed before, during and after the Eastern vacation period in early April. During this week the traffic, which represents about 70% of CO2 emissions, will be significantly reduced. The atmosphere will be analyzed with a high-resolution transport model to infer the reduction of the surface emissions. This result will be compared to the reduction of the traffic inferred from car counting statistics, and bottom-up estimates. The EM27 instruments will be moved around a large landfill, in order to measure the CH4 enhancement due to this installation, and estimate its emission. The waste sector represent by far the largest CH4 contributor (about 90%) in Mexico, and remains subject to large uncertainties.
Impact of coastal East Antarctic ice rises on surface mass balance: insights from observations and modelling
Authors: Kausch Thore , Lhermitte Stef , Lenaerts Jan T.M. , Wever Nander , Inoue Mana , Pattyn Frank , Sun Sainan , Wauthy Sarah , Tison Jean-Louis , van de Berg Willem Jan
Published: March 2020

About 20% of all snow accumulation in Antarctica occurs on the ice shelfs and ice rises, locations within the ice shelf where the ice is locally grounded on topography. These ice rises largely control the spatial surface mass balance (SMB) distribution by inducing snowfall variability due to orographic uplift and by inducing wind erosion due altering the wind conditions. Moreover these ice rises buttress the ice flow and represent an ideal drilling locations for ice cores.

In this study we assess the connection between snowfall variability and wind erosion to provide a better understanding of how ice rises impact SMB variability, how well this is captured in the regional atmospheric climate model RACMO, and the implications of this SMB variability for ice rises as an ice core drilling side. By combining ground penetrating radar profiles from two ice rises in Dronning Maud Land with ice core dating we reconstruct spatial and temporal SMB variations across both ice rises from 1982 to 2017. Subsequently, the observed SMB is compared with output from RACMO, SnowModel to quantify the contribution of the different processes that control the spatial SMB variability across the ice rises. Finally, the observed SMB is compared with Sentinel-1 backscatter data to extrapolate spatial SMB trends over larger areas.

Our results show snowfall-driven differences of up to ~ 0.24 m w.e./yr between the windward and the leeward side of both ice rises as well as a local erosion driven minimum at the peak of the ice rises. RACMO captures the snowfall-driven differences, but overestimates their magnitude, whereas the erosion on the peak can be reproduced by SnowModel with RACMO forcing. Observed temporal variability of the average SMBs calculated for 4 time intervals in the 1982-2017 range are low at the peak of the easternmost ice rise (~ 0.03 m w.e./yr), while being three times higher (~ 0.1 m w.e./yr) on the windward side of the ice rise. This implicates that at the peak of the ice rise, higher snowfall, driven by regional processes, such as orographic uplift, is balanced out by local erosion.  Comparison of the observed SMB gradients with Sentinel-1 data finally shows the potential of SAR satellite observations to represent spatial variability in SMB across ice shelves and ice rises.