bluuebunny/crossref_metadata_2025 huggingface dataset:
Magnetic structures and reformation at quasi-parallel shocks
Authors: Johlander Andreas , Battarbee Markus , Turc Lucile , Pfau-Kempf Yann , Ganse Urs , Grandin Maxime , Dubart Maxime , Alho Markku , Bussov Maarja , George Harriet , Tarvus Vertti , Papadakis Konstantinos , Suni Jonas , Zhou Hongyang , Palmroth Minna
Published: March 2021

Shock waves in collisionless plasmas are common in heliospheric and astrophysical settings and are some of the most efficient particle accelerators in space. Shocks can undergo self-reformation where a new shock front appears in front of the previous shock front. Shock reformation has been observed previously in both spacecraft observations and simulations, but the process is not yet fully understood. We here study self-reformation of Earth's quasi-parallel bow shock with observations from the four MMS spacecraft and simulation results from the hybrid-Vlasov simulation Vlasiator. We find, in both observations and simulation, that short large amplitude magnetic structures (SLAMS) can constitute shock reformation. The SLAMS form upstream of the shock and grow in amplitude while being convected towards the shock and eventually forming the new shock front. Using MMS's and Vlasiator's high-cadence field and ion measurements, we study how the shock reformation process influences the dynamics and acceleration of ions at the quasi-parallel shock.
Disentangling the impacts of anthropogenic aerosols on terrestrial carbon cycle during 1850-2014
Authors: Zhang Yuan , Ciais Philippe , Boucher Olivier , Maignan Fabienne , Bastos Ana , Goll Daniel , Lurton Thibaut , Viovy Nicolas , Bellouin Nicolas , Li Laurent
Published: March 2021

Aerosols have a dimming and cooling effect and change hydrological regimes, thus affecting carbon fluxes, which are sensitive to climate. Aerosols also scatter sunlight, which increases the fraction of diffuse radiation, increasing photosynthesis. Although previous studies have quantified the impacts of some of these factors separately, there remains no clear conclusion whether the physical impacts of aerosols on land carbon fluxes is larger through diffuse radiation change than through changes in other climate variables. In this study, we quantified the overall physical impacts of anthropogenic aerosols on land C fluxes and explored the contribution from each factor using a set of factorial simulations driven by climate and aerosol data from the IPSL-CM6A-LR experiments from 1850 to 2014. A newly-developed land surface model which distinguishes diffuse and direct radiation in canopy radiation transmission, ORCHIDEE_DF, was used. Specifically, a sub-grid scheme was developed to distinguish the cloudy and clear sky conditions. We found that anthropogenic aerosol emissions since 1850 cumulatively enhanced the land C sink by 22.6 PgC. 78% of this C sink enhancement is contributed by aerosol-induced increase in the diffuse radiation fraction, which is much larger than the effect of the aerosol-induced dimming. The cooling of anthropogenic aerosols increases the C sink in low latitudes but decreases the C sink in high latitudes and overall slightly increases the global land C sink. Compared with radiation and temperature changes, aerosol-induced precipitation changes have limited impacts. The dominant role of diffuse radiation changes in affecting historical land C fluxes found in this study implies that future aerosol emissions may have a much stronger impacts on the C cycle through changing radiation quality than through changing climate alone. Earth system models need to take into account the diffuse radiation fertilization effect, in order to better evaluate the impacts of climate change mitigation scenarios.
Understanding differences in land-atmosphere interactions between pan-European convection-permitting and parametrised climate models
Authors: Halladay Kate , Berthou Segolene , Kendon Elizabeth
Published: March 2021

Increasingly, we are using high-resolution convection-permitting models for climate projections but these models are less well understood in terms of the interaction between soil moisture, precipitation and evapotranspiration. The work was motivated by the discovery of warm, dry biases in summer in the 2.2 km convection-permitting model over France and eastern Europe compared to the 12 km convection-parametrised model that were associated with drier soils. We analyse several 12 km and 2.2 km versions of the Met Office Unified Model including sensitivity tests relating to soil hydraulics, land cover type and runoff model. We conduct similar tests using the land surface only to compare results between online and offline versions as the absence of some feedbacks can also produce differences.  
Integrated methodologies for seismic risk mitigation in Durrës (Albania) after the seismic event of November 26th, 2019
Authors: Shehu Elfrida , Skrame Klodian
Published: March 2021

Albania, the small country in the western Balkan, is a disaster-prone country. It ranks as one of the countries in the world with the highest economic risk from natural hazards events. During the past several decades, in average, Albania has been hit by about one major geological event per year. The impact of disasters in Albania are significantly compounded by a relatively high degree of poverty, lack of infrastructure maintenance, unsafe building and land use practices, linked to rapid urbanization, exploitation of natural resources (overgrazing of pasture, overexploitation of forests and riverbeds, etc.) as well as some other consequences of the transition from a centralized to an open marked economy.

From a geological point of view, Albania is a young and very dynamic territory and is very vulnerable to the geological and hydro-geological hazards as: earthquakes, landslides, flooding, torrential rains, river erosion, coastal erosion and avalanches that cover almost the entire territory. Due to these conditions its average annual losses count for about 2.5% of its GDP.

The Durrës earthquakes of 2019 had a huge impact on the Albanian economy. The city of Durrës, Thumanë, Tirana, Vora, Shijak and their villages suffered considerable damage after the earthquakes of September 21st, 2019 of Mw 5.4 and November 26th, 2019 of Mw 6.2. The main event of the 26th November caused the deaths of 51 persons and the damaging of hundreds of buildings. The degree of damages produced by these earthquakes has been, in some cases, significantly enhanced by the characteristics of the earthquake ground motion affected by the local subsurface soil structure and the quality of the constructions. The situations during and after the seismic events highlight the indispensable need of the seismic microzonation studies for the entire Albanian territory and emergency plans for the main cities of the country.

This paper shows the impact of the earthquake event on the housing market value by treating the data collected in the city of Durrës for the period December 2019 - September2020.

The main goal of the paper is to correlate the obtained results with the engineering-geological and geophysical conditions of the city of Durrёs and the seismic vulnerability of the building.

The findings of this study can be considered as a first step for in-depth studies aiming to calculate the impact of seismic risk and the change in the risk perception on the housing prices.
Evolution of melt-bearing shear zones during cooling within an upper crustal aureole: the Calamita Schists (Island of Elba, Italy)
Authors: Papeschi Samuele , Musumeci Giovanni , Bartoli Omar , Cesare Bernardo , Massonne Hans-Joachim , Mazzarini Francesco
Published: March 2021

The Calamita Schists in the aurole of the Late Miocene Porto Azzurro pluton underwent partial melting and HT metamorphism at P < 0.2 – 0.3 GPa and T > 650 – 700 °C, coeval with regional deformation. Deformation produced a network of shear zones that evolved from melt-present conditions to the brittle-ductile transition. Shearing at high temperature in the presence of melt allowed deformation to remain relatively distributed in wide high-strain zones. As the thermal pulse associated with the intrusion progressively faded away, deformation localized into anastomosing, mylonitic greenschist-facies shear zones surrounding lozenges of high-grade migmatitic schist. Mylonitic shear zones formed at low-angle with respect to the well-established high grade foliation preserved as a relic, oblique foliation. We show that such an extreme strain localization was determined by strain hardening of the no longer melt-bearing quartz-feldspar schist, localized embrittlement on precursory shear bands, and fluid-enhanced reaction softening that caused the breakdown of Al-silicates and the development of phyllosilicate-rich mylonitic bands. Consequently, tectonic structures with different orientation developed under the same kinematic regime, as a result of the changing physical and mechanical properties of the cooling rock volume.
Сharged particle acceleration in the CS of the Mercury magnetosphere: comparison of different mechanisms
Authors: Zhukova Elena , Popov Victor , Malova Helmi , Zelenyi Lev
Published: March 2021

The mechanisms of particle acceleration in the CS of the Mercury magnetosphere were investigated. The numerical model is developed that allows evaluating the acceleration of ions H+, He+, O+ in two possible mechanisms of particle acceleration: (1) by multiple dipolarizations during substorm activity passage of fronts; (2) by the turbulent electromagnetic field in the magnetosphere. Our simulation show that all kinds of charged plasma particles can be efficiently accelerated during multiple dipolarizations processes of the type (2) to maximum energies about 100-200keV. The gain of energies of ions under the (2) process of magnetospheric perturbations is about 10% higher than in the second case. The shapes of obtained in the model energy spectra were shown to be in agreement with experimental spectra. We conclude that the role of these mechanisms is more important near Mercury in comparison with plasma processes in the Earth’s magnetosphere.
Are the recurring earthquake swarms in West-Bohemia rain triggered?
Authors: Vlcek Josef , Beránek Roman , Fischer Tomáš
Published: March 2021

In past decades, a significant effort was spent to find the origin of recurring earthquake swarms in West-Bohemia/Vogtland. Widespread understanding accepts that crustal fluids migration along the fault zones is responsible for earthquake triggering in this area. Recently, a new model was suggested, which tests the hypothesis whether the diffusion of hydraulically induced pore pressure could be a valid trigger mechanism. In this approach the precipitation signal was transformed by diffusion equation to the hypocenter depth and statistically compared with the earthquake occurrence in time and concluded that at least 19% of the seismicity could have been triggered by rain. 

In our study we apply a different approach to verify the validity of these results. We use two types of rain signal on the input which is compared with the time series of earthquake weekly rate for the past 25 years. To remove the strong episodic character of the swarm seismicity we use a declustered seismic catalog, which is characteristic by almost continuous seismic activity.

The rain signal is represented first by the precipitation data and second by the water level data in the Horka reservoir, which is located above the main focal zone of Nový Kostel. We test the possible relation to the earthquake swarm activity by cross correlating both the rain signal types and the seismicity rate. To amplify the possible seasonal periodicity of the data we stacked the explored time series data (precipitation, water level and seismic activity) according to their occurrence date in a single year. The results show that in any of the input data and seismicity do not correlate. 

In the next step, we tested the possible (annual) periodicity of the data in question by the singular spectral analysis (SSA), which is a sensitive method to identify possible periodic signals in the presence of noise. While the water level data showed a striking peak for the period of 1 year, any indication of annual periodicity was never found in the seismicity data. Accordingly, we conclude that our analysis has shown no influence of the precipitation or the water level fluctuations in the Horka dam to the earthquake swarm activity in West Bohemia/Vogtland.
Geophysical Investigation of Boreal Forest Hydrogeology and Implications for Greenhouse Gas Fluxes
Authors: Mertes Jordan R , Kulessa Bernd , Kljun Natascha
Published: March 2021

Boreal forest ecosystems constitute the second largest forest biome after tropical rainforests yet have been estimated to contribute to 18-20% of the global terrestrial CO2 sink (~0.68±0.88 Pg C y-1 2006-2018) making our understanding of them critical during this period of changing climate. In Fennoscandia, ~90% of the boreal forest is managed. Increasing the amount of managed forests worldwide has been suggested as a way to improve C mitigation potential. However, due to the complex environmental effects caused by, for example, rotation forestry, further investigations are needed to understand all interactions that may occur. These potential ecosystem changes are not confined to the above ground environment, but also affect the subsurface, a part of the forest ecosystem that is often lesser understood spatially. One crucial consideration is alterations to the subsurface hydrogeology, which may lead to shifts in the local soil moisture regime, water table depth and depths to capillary zones. Such changes could have strong effects on localized greenhouse gas (GHG) fluxes. 

During the period of 2017-2020, we have conducted extensive hydrogeophysical investigations at the ICOS Norunda forest research site in Sweden (30 km north of Uppsala). The Norunda boreal forest research station is part of the European Integrated Carbon Observation System (ICOS) and offers one of the longest (>20 y) timeseries of local micrometeorological and GHG flux measurements. Here we have integrated electrical resistivity tomography (2-D profiling and monitoring), self-potential (2-D profiling and 3-D monitoring) and ground penetrating radar survey results to increase our knowledge of the local subsurface. Combining our geophysical observations with a priori knowledge of GHG fluxes in different zones of the forest (e.g. mature, thinned, marshy) allows us to investigate the relationships between hydrogeology and surface GHG fluxes. Here we present the highlight results from our study that include (i) spatial characterization of differing hydrogeological zones within Norunda from ERT, SP and GPR; and (ii) an evaluation of the importance of subsurface hydrology for soil GHG fluxes. 
Effects of sand extraction on marine environments: offshore deposits versus coastal deposits  
Authors: paganelli daniela , lavalle paola , targusi monica
Published: March 2021

Abstract

Coastal erosion is a serious environmental, social and economic issue in Europe and over the world. Much of Europe’s coastline is eroding and erosion threatens some of the values and functions of the coast. It was estimated that about 15,100 km of European coastline is retreating and that about 15 km2 of land is lost each year. Amongst the different techniques to stop or reduce local erosion, beach nourishment is considered to be one of the main tools for coastal management and also as the more ecologically sound, because it causes minor damage to the ecosystem, an aspect of extreme importance in the Mediterranean sea characterized by landscapes of outstanding natural value and by a large number of particularly sensitive and protected  habitats.

In this framework also in Italy the research of suitable sediment sources for beach nourishment has become a key theme of national interest, included also in the "National Guidelines for the defense of the coast from erosion and the effects of climate change” of the National Table on Coastal Erosion. Sediments for beach nourishment can have different origins, ordinarily comes from terrestrial quarries, and aquatic environment such as river mouths, canals, ports and offshore deposits. In Italy, most of sands used for beach nourishment comes from the dredging of offshore and coastal deposits.

Although dredgings for beach nourishment are carried out using uncontaminated sediments, these activities can produce significant effects on the environment. Extraction can affect benthic communities and demersal fish populations, sea bottom (morphology, bathymetry and sediment) and water column characteristics (turbidity, suspended solid) and in some cases, coastal dynamics.

In this paper we present a review of the main environmental effects induced on the Mediterranean environments by coastal and offshore dredging for beach nourishment, also with the aim to develop good practices and to support administrations engaged in sustainable management of coastal zone
Observing the Sun with LOFAR: an overview of the telescope capabilities and the recent results from the PSP groud base support campaign.
Authors: Zucca Pietro
Published: March 2021

Understanding and modelling the complex state of the Sun-solar wind-heliosphere system, requires a comprehensive set of multiwavelength observations. LOFAR has unique capabilities in the radio domain. Some examples of these include: a) the ability to take high-resolution solar dynamic spectra and radio images of the Sun; b) observing the scintillation (interplanetary scintillation - IPS) of distant, compact, astronomical radio sources to determine the density, velocity and turbulence structure of the solar wind; and c) the use of Faraday rotation as a tool to probe the interplanetary magnetic-field strength and direction. However, to better understand and predict how the Sun, its atmosphere, and more in general the Heliosphere works and impacts Earth, the combination of in-situ spacecraft measurements and ground-based remote-sensing observations of coronal and heliospheric plasma parameters is extremely useful. Ground-based observations can be used to infer a global picture of the inner heliosphere, providing the essential context into which in-situ measurements from spacecraft can be placed. Conversely, remote-sensing observations usually contain information from extended lines of sight, with some deconvolution and modelling necessary to build up a three-dimensional (3-D) picture. Precise spacecraft measurements, when calibrated, can provide ground truth to constrain these models. The PSP mission is observing the solar corona and near-Sun interplanetary space. It has a highly-elliptical orbit taking the spacecraft as close as nearly 36 sola radii from the Sun centre on its first perihelion passage, and subsequent passages ultimately reaching as close as 9.8 solar radii. Four instruments are on the spacecraft’s payload: FIELDS measuring the radio emission, electric and magnetic fields, Poynting flux, and plasma waves as well as the electron density and temperature; ISOIS measuring energetic electrons, protons, and heavy ions in the energy range 10 keV-100 MeV; SWEAP measuring the density, temperature, and flow speed of electrons, protons, and alphas in the solar wind; and finally, WISPR imaging coronal streamers, coronal mass ejections (CMEs), their associated shocks, and other solar wind structures in the corona and near-Sun interplanetary space, and provide context for the other three in-situ instruments. In this talk, the different observing modes of LOFAR and several results of the joint LOFAR/PSP campaign will be presented, including fine structures of radio bursts, localization and kinematics of propagating radio sources in the heliosphere, and the challenges and plans for future observing campaigns including PSP and Solar Orbiter.

 
Scenario design and analysis tasks of the National Data Centre Preparedness Exercise (NPE) 2019
Authors: Ross Ole , Gesternann Nicolai , Gaebler Peter , Ceranna Lars , Rizzo Antonietta , Ottaviano Giuseppe
Published: March 2021

National Data Centre (NDC) Preparedness Exercises (NPE) base on partially simulated scenarios of CTBT relevant events distributed to all NDC. They provide an opportunity to practice the verification procedures for the detection of nuclear explosions in the framework of CTBT monitoring. The NPE 2019 scenario was developed in close cooperation between the Italian NDC-RN (ENEA) and the German NDC (BGR). The fictitious state RAETIA announced a reactor incident with release of unspecified radionuclides into the atmosphere. Simulated concentrations of particulate and noble gas isotopes at IMS stations were given to the participants. The task was to check the consistency with the announcement and to search for waveform events in the potential source region of the radioisotopes.
During NPE2019 an Exercise Expert Technical Analysis was requested from the IDC for the first time. A fictitious state party provided within the scenario (simulated) national measurements of radionuclides and asked for assisistance in analysing the additional samples. Especially backward ATM and the search for seismic events in the possible source region was requested. In addition the overall consistency to potential emissions of the reactor incident declared by the ficititious state RAETIA was questioned. In the third and last stage of the exercise, national regional seismic data were distributed among the particpants which contained an (synthetically manipulated) anomaly pointing on a explosive event.
Heat distribution in the Tropical Indian Ocean during the prolonged La-Nina events during 1958–2017
Authors: Mukhopadhyay Soumya , Gnanaseelan C. , Chowdary J.S. , Mohapatra Sandeep
Published: March 2021

In the present study, heat distribution in the Tropical Indian Ocean (TIO) associated with the prolonged La-Nina events during 1958–2017 is examined using reanalysis/observations. A detailed analysis revealed that in response to prolonged La-Nina forcing, prominent east-west thermocline gradient in the equatorial Indian Ocean and the eastward extension of thermocline ridge in the southwestern TIO (TRIO) are noted. Anomalous subsurface warming, thermocline deepening, and sea-level increase are also evident in the eastern and southeastern TIO and Bay of Bengal (BoB) during the prolonged La-Nina events. Cross equatorial volume transport near the eastern boundary during the prolonged La-Nina years especially at 50m-150m depth levels indicates the pathways of Pacific water entering the north Indian Ocean (NIO), a feature that has a strong impact on the BoB dynamics and thermodynamics. Intense cooling of TRIO and the Arabian Sea and the eastward extension of TRIO are some of the characteristic features of the prolonged La-Nina years. These may have strong implications on the air-sea interaction associated with inter-annual and intra-seasonal variability over this region. Further, the subsurface heat content (50m–150m) in the eastern and southeastern TIO in general dominated by interannual variability whereas the TRIO region experienced the decadal variability. Subsurface heat content variations associated with prolonged La Niña years are discussed. This study shows that the warming and cooling events of TIO are very closely tied to the internal dynamics of the IO driven remotely by the Pacific through modulation of surface winds.
SHEMAT-Suite: a parallel open source simulator for flow, heat and mass transport in porous media
Authors: Keller Johannes , Fink Johanna , Klitzsch Norbert
Published: March 2021

We present SHEMAT-Suite, a numerical code for simulating flow, heat, and mass transport in porous media that has been published as an open source code recently. The functionality of SHEMAT-Suite comprises pure forward computation, deterministic Bayesian inversion, and stochastic Monte Carlo
simulation and data assimilation. Additionally, SHEMAT-Suite features a multi-level OpenMP parallelization. Along with the source code of the software, extensive documentation and a suite of test models is provided.

SHEMAT-Suite has a modular structure that makes it easy for users to adapt the code to their needs. Most importantly, there is an interface for defining the functional relationship between dynamic variables and subsurface parameters. Additionally, user-defined input and output can be implemented without interfering with the core of the code. Finally, at a deeper level, linear solvers and preconditioners can be added to the code.

We present studies that have made use of the code's HPC capabilities. SHEMAT-Suite has been applied to large-scale groundwater models for a wide range of purposes, including studying the formation of convection cells, assessing geothermal potential below an office building, or modeling submarine groundwater discharge since the last ice age. The modular structure of SHEMAT-Suite has also led to diverse applications, such as glacier modeling, simulation of borehole heat exchangers, or Optimal Experimental Design applied to the placing of geothermal boreholes.

Further, we present ongoing developments for improving the performance of SHEMAT-Suite, both by refactoring the source code and by interfacing SHEMAT-Suite with up-to-date HPC software. Examples of this include interfacing SHEMAT-Suite with the Portable Data Interface (PDI) for improved data management, interfacing SHEMAT-Suite with PetSC for MPI-parallel solvers, and interfacing SHEMAT-Suite with PDAF for parallel EnKF algorithms.

The goal for the open source SHEMAT-Suite is to provide a rigorously tested core code for flow, heat and transport simulation, Bayesian and stochastic inversion, while at the same time enabling a wide range of scientific research through straightforward user interaction.
Thermo-mechanical modelling of subducting plate delamination in the northern Apennines
Authors: Negredo Ana M. , Clemente Carlos , Carminati Eugenio , Jiménez-Munt Ivone , Vergés Jaume , Fullea Javier , Torné Montserrat
Published: March 2021

A number or previous studies indicate the possibility of post-collisional continental delamination in the northern Apennines. In this study we investigate by means of thermo-mechanical modelling the conditions for, and consequences of, delamination postdating continental subduction in this region. The modelled cross-section strikes approximately from Corsica to the Adriatic Sea. The initial model setup simulates the scenario at ca 20 Ma, where the oceanic lithosphere of the westward-subducting Adria plate was entirely consumed and some amount of continental subduction also occurred. The negative buoyancy of the slab remnant, together with the low viscosity of the dragged down lower continental crust, promote lithospheric mantle sinking into the mantle and asthenospheric upwelling and its lateral expansion along the lower crust. Consistent with geological data, the compressional front produced by delamination migrates about 260 km eastwards, causing a similar migrating pattern of extension from the northern Tyrrhenian Sea, to Tuscany and the seismogenically active Apennines backbone. The topographic response is computed by means of a true free-surface approach, and reflects the same eastward migrating pattern of uplift caused by asthenospheric inflow in the internal part of the system and crustal thickening; and subsidence at the front caused by the negative buoyancy of the sinking Adria slab. The conditions for the occurrence of magmatism and high heat flow beneath Tuscany are also explored. Simulations resulting in fast migration of the delamination front predict slab necking and breakoff, which could be consistent with the slab window observed beneath the central Apennines. Subcrustal seismicity beneath the Northern Apennines can be interpreted as the result to this incipient slab necking. This is a GeoCAM contribution (PGC2018-095154-B-I00)
The sources of sea-level rise in the Mediterranean Sea since 1960
Authors: Mir Calafat Francisco , Frederikse Thomas , Horsburgh Kevin , Dayoub Nadim
Published: March 2021

Sea-level change is geographically non-uniform, with regional departures that can reach several times the global average. Characterizing this spatial variability and understanding its causes is crucial to the design of adaptation strategies for sea-level rise. This, as it turns out, is no easy feat, primarily due to the sparseness of the observational sea-level record in time and space. Long tide gauge records are restricted to a few locations along the coast. Satellite altimetry offers a better spatial coverage but only since 1992. In the Mediterranean Sea, the tide gauge network is heavily biased towards the European shorelines, with only one record with at least 35 years of data on the African coasts. Past studies have attempted to address the difficulties related to this data sparseness in the Mediterranean Sea by combining the available tide gauge records with satellite altimetry observations. The vast majority of such studies represent sea level through a combination of altimetry-derived empirical orthogonal functions whose temporal amplitudes are then inferred from the tide gauge data. Such methods, however, have tremendous difficulty in separating trends and variability, make no distinction between relative and geocentric sea level, and tell us nothing about the causes of sea level changes. Here, we combine observational data from tide gauges and altimetry with sea-level fingerprints of land-mass changes through a Bayesian hierarchical model to quanify the sources of sea-level rise since 1960 at any arbitrary location in the Mediterranean Sea. We find that Mediterranean sea level rose at a relatively low rate from 1960 to 1990, primarily due to dynamic sea-level changes in the nearby Atlantic, at which point it started rising significantly faster with comparable contributions from dynamic sea level and land-mass changes.
Water Decision Support System for Urban Water Security under Uncertain Future: A Case Study of Upper Yamuna River Basin, India
Authors: Kumar Dinesh , Dhanya Chandrika Thulaseedharan , Gosain Ashvani
Published: March 2021

Ensuring water security considering the near- and far-future climatic and socio-economic uncertainties, is one of the grand global challenges. In developing countries, supply-side management like the construction of new dams, rehabilitation and augmentation of the existing water resources and supply infrastructure are the widely adopted solutions. Often, the importance of the requirement of water for environmental well-being is neglected. Here, we develop a modelling framework using Water Evaluation and Planning and Qual2K models, considering ‘environment’ also as a stakeholder. This water decision support system is demonstrated on the Upper Yamuna River Basin, a complex and polluted river system in India. Further, to raise risk awareness among stakeholders about the extreme plausible future conditions, the storyline-based approach is adopted to develop future scenarios. The developed framework is deployed to explore the National Capital Territory of Delhi's urban water security for different plausible future scenarios. Based on this, reliability of different policy management options and strategies are explored. The simulated results show that the localized (urban level) management strategies are more reliable than the basin level management strategies, especially under a prolonged plausible warmer climate and better standard of living based socio-economic development conditions. The model building, scenario development, and analysis demonstrate the importance of incorporating the local system knowledge to build an effective decision support system for physically and legally complex river basins.
Seismic imaging combining active and passive sources using distributed acoustic sensing
Authors: Faucher Florian , Scherzer Otmar , de Hoop Maarten V.
Published: March 2021

DAS finds growing interest in seismic exploration by offering a dense and low-cost coverage of the area investigated. Nonetheless, contrary to the usual geophones that measure the displacement, DAS provides information on the strain. In this work, we perform quantitative imaging of elastic media designing a new misfit functional that is adapted to these data-sets. This misfit criterion is based on the reciprocity-gap, hence defining the full reciprocity-gap waveform inversion. The main feature of our misfit is that it does not require the knowledge of the exciting source positions, and it allows us to combine data from active and passive (of unknown location) sources. In particular, the data from passive sources contain the low-frequency information needed to build initial models, while the exploration data contain the higher frequencies. We consequently follow a multi-resolution framework that we illustrate with two-dimensional elastic experiments.
Monitoring diffuse CO2 emissions by means of an automatic geochemical station at Cumbre Vieja volcano, La Palma, Canary Islands.
Authors: Barrancos José , Rodríguez Claudia , Padrón Eleazar , Hernández Pedro A. , Padilla Germán D. , D’Auria Luca , Pérez Nemesio M.
Published: March 2021

La Palma Island (708.3 km2) is located at the north-west and is one of the youngest (~2.0My) of the Canarian Archipelago. Volcanic activity has taken place exclusively at the southern part of the island, where Cumbre Vieja volcano, the most active basaltic volcano in the Canaries, has been constructed in the last 123 ky. Cumbre Vieja has suffered seven eruptions in the last 500 years, being the last in 1971 (Teneguía volcano). Since the last eruptive episode, Cumbre Vieja volcano has remained in a relative seismic calm that was interrupted on October 7th and 13rd, 2017, by two remarkable seismic swarms with earthquakes located beneath Cumbre Vieja volcano at depths ranging between 14 and 28 km with a maximum magnitude of 2.7. The frequency of these seismic episodes increased in 2020 with the occurrence of five more seismic swarms

As part of the volcano monitoring program of Cumbre Vieja, diffuse degassing of CO2 has been continuously monitored since 2005 at the southernmost part of Cumbre Vieja according to the accumulation chamber method. The monitoring site (LPA04) was selected because it shows anomalous diffuse CO2 degassing emission values with respect to the background values that had been measured in different surveys (Padrón et al., 2015). Meteorological and soil physical variables are also measured in an hourly basis and transmitted to ITER facilities about 150 Km far away.

Since its installation, CO2 emissions ranged from non-detectable (<1.5 gm-2d-1) to 1,464.0 gm-2d-1. The time series was characterized by a strong variability in the measured values that are modulated mainly by the atmospheric and soil parameters. Soil moisture is the monitored parameter that explains the highest variability of the data, being the dry season (spring y summer) the period with the highest observed diffuse emission values. This behavior in the time series has changed after 2017 as an increasing trend in being observed in a good temporal agreement with the increase of seismic activity recorded. The observed diffuse CO2 emissions trend in the LPA04 geochemical station support the occurrence of an upward magma migration towards a subcrustal magma reservoir beneath La Palma island.

Padrón et al., (2015). Bull Volcanol 77:28. DOI 10.1007/s00445-015-0914-2
High local nutrient input influence on oligotrophic phytoplankton production and lipid biogeochemistry
Authors: Novak Tihana , Gašparović Blaženka , Vrana Špoljarić Ivna , Čanković Milan
Published: March 2021

Marine phytoplankton are crucial for ecosystem function and responsible for almost half of world’s primary production. In order to grow and reproduce phytoplankton need sufficient amount of macro and micro nutrients. Nutrient concentrations are changeable in different water mases and dependable on different natural and anthropogenic sources such as terrestrial water inputs, recycling by sloppy feeding, remineralization with bacteria and atmospheric deposition. High nutrient input to oligotrophic regions raises phytoplankton biomass that leads to higher organic matter production and heterotrophs` development.  Anthropogenic nutrient inputs are considered as the main cause of coastal eutrophication. Marine lipids, dominantly produced by phytoplankton, are good biogeochemical traces of organic matter origin and processing in marine environment and phytoplankton adaptation to environmental perturbations. They are important for multiple cell mechanisms functioning.

The goal of this research was to investigate the influence of a point source of nutrients on organic matter production and lipid composition as a consequence of phytoplankton acclimation to different nutrient loads. We sampled at two geographically close stations in the Krka River Estuary mouth, oligo- to mesotrophic Martinska station and station in vicinity of the town of Šibenik that is under high anthropogenic influence. Samples were taken from three depths (above, on and below halocline) and in four different seasons covering annual cycle. Lipid classes were characterized by thin–layer chromatography–flame ionization detection. Data are supported by hydrographic, dissolved organic carbon and particulate organic carbon parameters. We will discuss the changes of organic matter accumulation and estuarine lipid biogeochemistry caused by human activity.

 

Acknowledgement

This research was financed by the Croatian Science Foundation project BiREADI (IP-2018-01-3105).
Convolutional Neural Networks for Sea Ice Concentration Charting for Maritime Navigation in the Arctic
Authors: Stokholm Andreas , Pedersen Leif , Forsberg René , Hvidegaard Sine
Published: March 2021

In recent years the Arctic has seen renewed political and economic interest, increased maritime traffic and desire for improved sea ice navigational tools. Despite a rise in digital technology, maps of sea ice concentration used for Arctic maritime operations are still today created by humans manually interpreting radar images. This process is slow with low map release frequency, uncertainties up to 20 % and discrepancies up to 60 %. Utilizing emerging AI Convolutional Neural Network (CNN) semantic image segmentation techniques to automate this process is drastically changing navigation in the Arctic seas, with better resolution, accuracy, release frequency and coverage. Automatic Arctic sea ice products may contribute to enabling the disruptive Northern Sea Route connecting North East Asia to Europe via the Arctic oceans.

The AI4Arctic/ASIP V2 data set, that combines 466 Sentinel-1 HH and HV SAR images from Greenland, Passive Microwave Radiometry from the AMSR2 instrument, and an equivalent sea ice concentration chart produced by ice analysts at the Danish Meteorological Institute, have been used to train a CNN U-Net Architecture model. The model shows robust capabilities in producing highly detailed sea ice concentration maps with open water, intermediate sea ice concentrations as well as full sea ice cover, which resemble those created by professional sea ice analysts. Often cited obstacles in automatic sea ice concentration models are wind-roughened sea ambiguities resembling sea ice. Final inference scenes show robustness towards such ambiguities.
Grounding-zone flow variability of Priestley Glacier, Antarctica, in a diurnal tidal regime
Authors: Drews Reinhard , Wild Christian , Marsh Oliver , Rack Wolfgang , Ehlers Todd , Neckel Niklas , Helm Veit
Published: March 2021

Dynamics of polar outlet glaciers vary with ocean tides, providing a natural laboratory to understand basal processes beneath ice streams, ice rheology and ice-shelf buttressing. We apply Terrestrial Radar Interferometry to close the spatiotemporal gap between localized, temporally well-resolved GNSS and area-wide but sparse satellite observations. Three-hour flowfields collected over an eight day period at Priestley Glacier, Antarctica, validate and provide the spatial context for concurrent GNSS measurements. Ice flow is fastest during falling tides and slowest during rising tides. Principal components of the timeseries prove upstream propagation of tidal signatures $>$ 10 km away from the grounding line. Hourly, cm-scale horizontal and vertical flexure patterns occur $>$6 km upstream of the grounding line. Vertical uplift upstream of the grounding line is consistent with ephemeral re-grounding during low-tide impacting grounding-zone stability. On the freely floating ice shelves, we find velocity peaks both during high- and low-tide suggesting that ice-shelf buttressing varies temporally as a function of flexural bending from tidal displacement. Taken together, these observations identify tidal imprints on ice-stream dynamics on new temporal and spatial scales providing constraints for models designed to isolate dominating processes in ice-stream and ice-shelf mechanics.
Reducing Nutrient Loads in Northern Irish Catchments: A Modelling Approach Based on Load Apportionment and Flow Pathway Identification
Authors: Adams Russell , Doody Donnacha
Published: March 2021

Northern Ireland has been somewhat overlooked in terms of water quality modelling in the past. Many of its catchments have consistently failed to meet Water Framework Directive targets especially due to high levels of dissolved nutrients and poor ecological status. A catchment based modelling study to address this issue has not been undertaken here previously and the approach described here uses two water quality models to achieve this aim. The objectives of the modelling were firstly to identify the total load reductions (in terms of Phosphorus (P)) required to reduce in-stream loadings sufficiently for concentrations of soluble reactive P (SRP) to be reduced to achieve the WFD “Good” status levels, and secondly to split these loadings into diffuse and point components. The third objective was to identify the most likely flow pathways for the transport of the diffuse component of P to the watercourses particularly for the agricultural (mostly intensive grassland farming) land use which dominates in almost all NI catchments.

The first model applied is the Source Load Apportionment Model (SLAM) developed by the Irish EPA. This model provides a large-scale assessment of the point and diffuse load components across catchments where multiple pressures are occurring. The second model us the Catchment Runoff Flux Assessment Tool (CRAFT) which is able to back-calculate nutrient loads associated with three major flow pathways. SLAM is a static model which uses averaged loadings from diffuse agriculture and non-agricultural land uses, and point sources (where information can be obtained from various sources) to calculate N and P exports. For P, the agricultural diffuse load component uses an enhanced version of the export coefficient approach based on combining the sources of P from applied nutrients (slurry and fertiliser) and soil P. A modelling tool allows the user to evaluate load reduction scenarios where one or several components of P (both point and diffuse) are adjusted downwards to achieve the catchment’s required load reduction. The CRAFT model works on a dynamic (daily) modelling scale and has simulated sub-catchments where the SLAM model has identified the need for significant load reductions. It identifies the different reductions (P export) that are required for each flow pathway, which will then inform on the type of additional measures (e.g. sediment traps, riparian buffer strips and wetlands) that may also be required.

The initial aim of this study is to complete a pilot application to the trans-border (UK and ROI) Blackwater catchment (1360 km2). Through a review of alternative modelling options for the whole area of NI, an assessment of whether this approach is suitable for application to the entire territory can be made.
Geometrical characterisation of fault arrays in three dimensions
Authors: Roche Vincent , Camanni Giovanni , Childs Conrad , Manzocchi Tom , Walsh John , Conneally John , Saqab Muhammad Mudasar , Delogkos Efstratios
Published: March 2021

Normal faults are often complex three-dimensional structures comprising multiple sub-parallel segments separated by intact or breached relay zones. In this study we outline geometrical characterisations capturing this 3D complexity and providing a semi-quantitative basis for the comparison of faults and for defining the factors controlling their geometrical evolution. Relay zones are classified according to whether they step in the strike or dip direction and whether the relay zone-bounding fault segments are unconnected in 3D or bifurcate from a single surface. Complex fault surface geometry is then described in terms of the relative numbers of different types of relay zones to allow comparison of fault geometry between different faults and different geological settings. A large database of 87 fault arrays compiled primarily from mapping 3D seismic reflection surveys and classified according to this scheme, reveals the diversity of 3D fault geometry. Analysis demonstrates that mapped fault geometries depend on geological controls, primarily the heterogeneity of the faulted sequence and the presence of a pre-existing structure. For example, relay zones with an upward bifurcating geometry are prevalent in faults that reactivate deeper structures, whereas the formation of laterally bifurcating relays is promoted by heterogeneous mechanical stratigraphy. In addition, mapped segmentation depends on resolution limits and biases in fault mapping from seismic data. In particular, the results suggest that the proportion of bifurcating relay zones increases as data resolution increases. Overall, where a significant number of relay zones are mapped on a single fault, a wide variety of relay zone geometries occurs, demonstrating that individual faults can comprise segments that are both bifurcating and unconnected in three dimensions. Models for the geometrical evolution of fault arrays must therefore account for the full range of relay zone geometries that appears to be a characteristic of all faults.
Data-driven and physically informed modelling of the Terrestrial Water Storage dynamics 
Authors: Douch Karim , Saemian Peyman , Sneeuw Nico
Published: March 2021

The Gravity Recovery and Climate Experiment (GRACE) mission, and its successor GRACE Follow-On, have enabled to map on a monthly basis the Terrestrial Water Storage Anomaly (TWSA) since 2002. This unprecedented capability has provided hydrologists with new observations of the spatiotemporal evolution of TWSA, which have been used, among others, to better constrain numerical runoff models, to characterize empirically the relations between runoff and TWSA, or to simply monitor and quantify groundwater depletions. In this study, we explore the possibility to infer from GRACE observations a physically informed and linear dynamical system that models the intrinsic dynamics of TWSA at sub-basin scales.

First, we apply a hexagonal binning over the study area and aggregate the total water volume anomaly derived from GRACE data for each bin. Assuming that each bin exchanges water with the others in proportion to its water content, we then reformulate the mass balance equation of the whole basin as a first order matrix differential equation. All the proportionality coefficients encoding the bin exchanges are gathered in an unknown transition matrix to be determined.  Such a transition matrix must satisfy different algebraic properties to be physically consistent and interpretable. In particular, we show that this matrix is necessarily a left stochastic matrix. Finally, we used the time series of total water volume anomaly to estimate this transition matrix by solving an optimization problem on the manifold defined by the aforementioned matrix constraint. This method is applied to the Amazon basin and to mainland Australia respectively, and the predictive performances of the derived dynamical systems are quantified and discussed.