bluuebunny/crossref_metadata_2025 huggingface dataset:
Simulating lava tube exploration research during analog lunar and Martian missions at HI-SEAS in Hawaii 
Authors: Musilova Michaela , Foing Bernard , Rogers Henk
Published: March 2021

Lava tube exploration has become an important part of discussions relating to the search for life on Mars by both humans and robots. On Mars, lava tubes may contain biosignatures and existing lifeforms. Alternatively, on the Moon, lava tubes may serve as sheltered environments for the construction of human settlements. Nevertheless, lava tubes can also be difficult environments for robotic operations and they can pose a safety hazard to humans as well. It will thus be extremely important to prepare for lava tube exploration by humans and robots in analog environments on Earth. The Hawaii Space Exploration Analog and Simulation (HI-SEAS) habitat is a lunar and Martian analog research station located on the volcano Mauna Loa in Hawaii. The International MoonBase Alliance (IMA) organises missions at HI-SEAS, during which crews of six analog astronauts perform research and technology testing relevant to the exploration of the Moon and Mars. The missions that take place at HI-SEAS can be of varied duration, from several days to several months, depending on the needs of the researchers. They are open to space agencies, organizations and companies worldwide to take part in, provided their research and technology testing will help contribute to the exploration of the Moon and Mars. Since the HI-SEAS habitat is located on lava flows, its surroundings provide valuable access to performing high-fidelity planetary science fieldwork with very little plant or animal life present, and a wide variety of volcanic features to explore, such as lava tubes, channels, and tumuli. This terrain is also ideal for rover and in situ resource utilization (ISRU) testing because of its great similarity to the basaltic terrains on the Moon and Mars. HI-SEAS crews have performed a number of biochemical and geophysical research projects in the lava tubes accessible to them near the habitat. They explored and collected research samples while wearing Extra-vehicular Activity (EVA) analog spacesuits and following strict EVA protocols. These activities are very challenging for the crew, due to the bulky gloves and EVA equipment they have to wear, while performing precise biochemical research that is sensitive to contamination. The crews also have to take into consideration their safety, their limited life support systems during EVAs and a number of other factors relevant to space exploration missions. Further studies will be needed to assess how best to combine scientific goals with human exploration goals during future human missions, which may use lava tubes as a resource as well as a key site for scientific research.
Red-coloured pedosediments of the Lori Basin, Armenia 
Authors: Revunova Anna , Khokhlova Olga
Published: March 2021

In this work, the samples of red-coloured pedosediments were analyzed. They were found in two sections of the Lori Basin, Armenia - Kurtan-IV and Yagdan. Micromorphological analysis, the measurement of magnetic susceptibility, particle size distribution, CHN, determination of bulk, and biomorphic composition was made. Based on the results of previous studies, the age of the deposits overlying these sections was known. The pedosediment from the Kurtan-IV section is overlain by a mixture of sand and volcanic ash, which is dated at about 1.4 Ma (Calabrian). The pedosediment from the Yagdan section is overlain by 2-2.5 Ma basaltic lava (Gelasian). As a result of our research, it was revealed that both pedosediments were formed in conditions differ from current ones and have differences between themselves also. The pedosediment from the Yagdan section was formed during the dominance of the subtropical climate. It was revealed the presence of manganese-ferruginous and clayey films, a low index of carbonization and salinity, and a relatively high index of weathering. Pedo-sediments from the Yagdan section can be classified as Cambisols with vitric, argic, chromic qualifiers. By the time the later section Kurtan-IV was formed, the climate became cooler, which was reconstructed by the appearance of phytoliths of coniferous plants. Pedosediment from the Kurtan-IV section can be classified as Stagnic Luvisols. The later factors influencing the preservation of pedosediments and changes in their composition and properties were identified. Thus, the upper horizon of the Yagdan section sharply differs from the underlying ones in increased weathering and oxidation, and these properties are retained up to the third layer. It has increased indicators of magnetic susceptibility and the content of copper elements, cobalt, nickel, vanadium, chromium, which were brought in by basalt lava. The pedosediment from the Kurtan-IV section was overlain by lacustrine deposits, which led to a decrease in the magnetic susceptibility and an increase in the SiO2 content and carbonation index. This work was supported by RFBR, grant N19-29-05024 mk.
Features of the Lena River runoff influence on the adjacent Laptev Sea shelf
Authors: Rogozhin Vladimir , Polukhin Alexander , Yakushev Evgeniy , Semiletov Igor
Published: March 2021

The annual runoff of river water into the Laptev Sea is 745 km3, most of the runoff belongs to the Lena River - 525 km3.  Long-term variability in the volume of the Lena River runoff play a significant role in the variability of the scale of distribution of freshwater lenses in the Laptev Sea. The processes that take place in the area of ​​intense river runoff have an impact both in the shelf zone and in the open part of the sea due to the transfer of large-area lenses of freshened water. The influence of river runoff is considered from the Lena Delta to the continental slope of the Laptev Sea.

The data on physical and chemical properties of the Laptev Sea shelf used in this investigation was obtained during the expeditions of the Shirshov Institute of Oceanology in 2015 and 2017 and the Pacific Oceanological Institute in 2018-2020.

The distribution of hydrochemical parameters in the Lena Delta area in 2019 was typical for the river-sea mixing zone. The distribution of silicate was mixed, i.e. horizontal stratification prevailed in the near-surface layers, and vertical stratification in the bottom layers. The maximum values ​​were observed in the near-mouth area, reaching indicators over 30 µM / L, which generally coincides with the values ​​of this indicator in 2015 and more than in 2017.

When considering the distribution of specific alkalinity (total alkalinity-salinity ratio), which serves as a proxie of riverine water, it is worth noting the deepening of the boundary by 0.07 units. In 2019, this border was at depths of 20 to 40 meters, which is an atypical indicator for this water area. Apparently, this has happened owing to an increase in the supply of carbonate ions, which is noticeable from an increase in the values ​​of carbonate alkalinity in the Lena River waters (Arctic Great Rivers Observatory data).

The calculation of the parts of fresh water, based on salinity data in 2019, showed that the maximum values ​​were observed near the Lena River delta and amounted to 30-35%. Northward, the part of riverine water was up to 10% only in the surface layer. Comparing with similar calculations performed for the 2015 and 2017 sections, it should be noted that the part of fresh water has decreased. Perhaps this is due to the inflow of continental runoff in 2019 was the lowest over the considered period.

Funding: The work was carried out within the framework of the Shirshov Institute of Oceanology state assignment (theme No. 0149-2019-0008), with funding of the Russian Scientific Foundation (project No. 19-17-00196) and the grant of the President of the Russian Federation MK-860.2020.5.
Runoff regime after heavy rainfall events in view of changing climate in a beech stand at the LTER-CWN site “Klausenleopoldsdorf”
Authors: Günther Gollobich , Karl Gartner , Sebastian Riedel
Published: March 2021

The Austrian Research Infrastructure LTER-CWN (Long-Term Ecosystem Research Infrastructure for Carbon, Water and Nitrogen) aims for measuring extreme events in high temporal resolution. Within the framework of this project a measuring weir was installed near Klausen-Leopoldsdorf (Lower Austria) in order to collect high-resolution data of stream-water quantity and quality. The measuring weir is located in the western part of the „Wienerwald“, the north-eastern edge of the Alps, at about 475m a.s.l. Especially in the year 2020 this area showed humid weather conditions with an annual precipitation of 904mm. The observed catchment has an area of about 46 hectares. The dominating soil types in the catchment are Planosoils and Stagnosols. The observations at the weir with a time resolution of 5 minutes started in February 2019. The plot was set up for recordings of carbon (C), nitrogen (N) and water fluxes theparameters TOC-N, DOC-N, NO3, water level, water temperature, electrical conductivity, turbidity and organic matter values being measured. To answer one of the main research issues - the impact of heavy rainfall events on the runoff regime of a catchment within a dense beech forest in relation to the soil, specific time, the influence of interception and corresponding water level in the observed river - a water level sensor (OTT) and a multifunction spectrolyzer (S:CAN) were installed at the weir. During the measuring period 2019/2020 11 heavy rainfall events (corresponding to more than 20mm daily precipitation sum) were recorded. Due to the small catchment area the average time interval between heavy rainfall events and the corresponding increase of the water level at the measuring weir is about 2 hours. The time and intensity of the rainfall event together with the level of soil moisture before the precipitation event are the key factors for the amount of runoff. Additionally, other measured parameters like the turbidity or the electrical conductivity of the water correspond very well with the amount of runoff. Data with such a high time resolution will help to get a better understanding of extreme events and the consequences of these events in respect to climate change.
A Multi-variable & Multi-objective Optimization Framework for LID Layout in Sponge City
Authors: Tang Sijie , Jiang Jiping , Zheng Yi
Published: March 2021

Practitioners usually design the plan of Sponge City construction (SCC) by combining LID facilities (e.g., rain garden, rain barrels, green roofs, and grassed swales) according to their personal experiences or general guidelines. The layout (including selection, connection and distribution area) of LID facilities is subjective, in the risk of far from optimal combination. Previous researchers have developed some LID optimization tools, which only consider the dimension and number of LIDs in a given scenario. Therefore, it is necessary to develop a flexible and extensible design tool with the support of urban hydrological model to conduct the facilities layout optimization. This study introduced a SWMM-based multi-variable and multi-objective optimization framework called CAFID (Comprehensive Assessment and Fine Design Model of Sponge City) to meet this end. The assessment module with multi-objective couples diverse controlling end-points (e.g., total runoff, peak runoff, pollutant concentration, cost, and customized social-ecological factors) as the candidates of assessment criteria. The optimization module with multi-variable is implemented by SWMM, starting with three steps: 1) Full allocation. Based on the availability, list the candidates of LID facility for each sub-catchment; 2) Full connection. Order the potential stream direction of surface runoff from rainfall to municipal network, based on possible hierarchical structure of sub-catchments and LID facilities; 3) Full coverage. Identify all the suitable area for LID facility in sub-catchment. The optimization on the 3 variables, the selection, connection, and area, is powered by NSGA-II and TOPSIS algorithms, which make it possible that we choose a final result from the set of nondominated solutions according to special weight distribution. The effectiveness of CAFID was illustrated through a case of Sponge City in Fenghuangcheng of Shenzhen City, one of 30 national pilot sponge cities in China. As well, this new framework is expected to be widely verified and applied in Sponge City construction in China or similar concepts all over the world.
Southern Hemisphere Westerly Winds and Holocene climate variability on sub-Antarctic South Georgia
Authors: Zwier Maaike , Bjune Anne , van der Bilt Willem
Published: March 2021

The Southern Hemisphere Westerly Winds play a major role in the global climate system. By driving circulation in the Southern Ocean and its subsequent effect on the upwelling of carbon-rich deep water, the Westerlies affect the oceans ability to take up atmospheric CO2. Furthermore, by impacting temperature conditions and moisture availability, the Westerlies act as a first-order control on local environmental conditions. Uncovering long term natural climatic variability in the sub-Antarctic is therefore crucial to understand how the global system might react under future climate changes. Due to the lack of land mass on the Southern Hemisphere, sub-Antarctic islands are essential for studying climate variability in this region; terrestrial records provide valuable insights into both local and regional surface climate conditions. We use a pollen record from Lake Diamond to provide detailed reconstructions of vegetation and climate on sub-Antarctic South Georgia for the last ~9900 years. Westerly Wind strength and position is inferred from long-distance transport of pollen from South America, Africa, and New Zealand. Additionally, changes in relative pollen abundance of native taxa occupying either upland (cold) or lowland (warm) environments are used to infer local climatic variation, supported by additional sedimentological proxies. On South Georgia we find long-distance transported pollen from several South American taxa, mainly Nothofagus, Ephedra and Asteraceae. They show a general increase in abundance throughout the Holocene, with peak influx between 2800 and 1500 cal yr BP, most likely caused by changes in the strength of the Southern Hemisphere Westerly Winds. In both our record and others, this interval is seen as the end of the Neoglacial period.
LiDAR, UAV SfM and geomorphic change detection in small quarry and landslide interactions
Authors: Ciotină Mihai Cosmin , Niculiță Mihai , Stoilov-Linu Valeriu
Published: March 2021

Quarry activity triggers landslides, especially in small, unplanned, and not maintained quarries. Given the size of these small quarries that are very frequent in the rural areas of north-eastern Romania, their study is difficult because of the lack of topographic data. We show the usage of remote sensing data for geomorphic change detection, which is able to reveal the topographic evolution of the quarrying and landsliding. Legacy LiDAR data from 2012 and field surveyed UAV from 2019 are used to assess the topographic changes, compared to the 1980 5k topographic maps. The quarry location is related to the presence of old landslide bodies (dated to the early medieval period using radiocarbon ages of soil organic matter fractions), from which the clay material is excavated for various construction projects. The unplanned excavation reactivated the body of an old landslide that will continue evolving. The usage of LiDAR data and the UAV SfM survey allowed us to derive 0.25 m DEMS that pinpoint the volumetric change of the quarried material and of the landslide reactivation. As a future prospect, the use of such remote sensing data can pinpoint areas where these unplanned quarries could affect the stability of the hillslopes and become a hazard.
Probing the solar corona magnetic field with sungrazing comets
Authors: Nisticò Giuseppe , Nakariakov Valery M. , Duckenfield Timothy , Druckmüller Miloslav , Zimbardo Gaetano
Published: March 2021

Space telescopes of the SoHO, STEREO and SDO missions have occasionally acquired observations of comets, providing an interesting opportunity to investigate the structure and dynamics of the heliospheric plasma.  Cometary plasma tails exhibit a wave-like motion, which is believed to be a response to the physical conditions of the local interplanetary medium. Furthermore, sungrazing comets diving in the solar atmosphere provide us with an unprecedented way to diagnose the coronal plasma at distances which are unaccessible from the current spacecraft. Here, we present observations of Comet Lovejoy C/2011 W3 from SDO/AIA, which was seen to cross the EUV solar corona in December 2011. The cometary ions produced by the sublimation of the comet nucleus were channelled along the magnetic field lines forming some filamented structures. Such structures appear to show small amplitude kink oscillations, which are used to determine the magnitude of the coronal magnetic field by coronal seismology.
Develop a reduced-complexity model – SCM4OPT v3.0 for integrated assessment-optimization
Authors: Su Xuanming
Published: March 2021

The Simple Climate Model for Optimization version 2.0 (SCM4OPT v2.0) is one of the contributors to the Reduced Complexity Model Intercomparison Project Phase 2 (RCMIP2). However, low effective radiative forcing is emulated in SCM4OPT v2.0, which is driven by the strong negative aerosol effective radiative forcing and considered to be an outlier compared to other models. In addition, the carbon cycles and climate system in SCM4OPT v2.0 are calibrated based on the outputs from Coupled Model Intercomparison Project Phase 5 (CMIP5), which cannot reflect the latest Earth system model results. In this study, we update the reduced-complexity model to SCM4OPT v3.0. First, we re-calibrate the carbon cycles, including land carbon-cycle and ocean carbon-cycle, and the climate system according to 32 coupled atmosphere-ocean general circulation models (AOGCMs) with selected experimental outputs in the latest CMIP6; Second, we fix the aerosol forcing by introducing a constrain in the light of the IPCC AR5 aerosol forcing. We retain the lightweight and efficient nature of this model, in order to make it suitable to be involved in a large-scale optimization process. Using SCM4OPT v3.0, we produce a new set of scenario simulations by using the dataset of harmonized emissions used in CMIP6 and compare with other reduced-complexity models. SCM4OPT v3.0 is expected to simulate climate-related uncertainties regarding the latest understanding of climate change.
Shield wires effect on GICs in Portuguese power network and design of an instrument to monitor GICs in the transformer neutrals
Authors: Santos Rute , Cardoso João , Pais M. Alexandra , Silva Miguel , Alves Ribeiro Joana , J. G. Pinheiro Fernando
Published: March 2021

Geomagnetically Induced Currents (GICs) are the result of rapid variations in the Earth's geomagnetic field and of the finite conductivity of the Earth. Along grounded conducting structures such as the power grids, the induced electric field drives electric currents in closed circuits. Extreme values of GICs can be a threat to the normal operation of the power system. So, there is an increasing interest in the study of the GICs’ risk and the first step to take is the numerical modelling. In order to model GICs, different factors/parameters must be considered, as the distribution of conductivity, laterally and in depth and characteristics of the different components of the network. These include the values of the different resistances in the power network, the types of transformers and also the transmission path for the GICs. Shield wires represent possible paths for GIC currents. In this study the influence of shield wires on GICs in power systems is modelled. Tests were done using realistic values for the circuit parameters provided by the Portuguese high voltage power network company (REN).

The MAG-GIC (Geomagnetically induced currents in Portugal mainland) project has already produced GIC simulations for the South of Portugal. However, there are still no direct records of GICs in the electrical transmission network to validate that model. This study also encompasses the task of producing a measuring instrument to monitor GICs in the neutral of a given transformer. Such an instrument can provide for the measurement and recording of quasi-DC currents with Hall current sensors, with high resolution. It is targeted to operate remotely over a time interval of several months while being minimally invasive to the power transformer (PT). The system relies on LEM high sensitivity closed loop Hall effect current sensors and it is built over a Raspberry Pi 4 Model B platform with a high resolution digitizer (24 bits) expansion board (Waveshare AD/DA). The system also includes temperature monitoring for offset correction. Recorded data are locally stored on a database (InfluxDB) and a wifi interface allows rapid long term trend visualization through a customized dashboard (Grafana).
The impact and fate of fallout radionuclides by Fukushima Daiichi Nuclear Power Plant Accident in hydrological systems and post-accident environmental recovery
Authors: Onda Yuichi , Taniguchi Keisuke , Yoshimura Kazuya , Wakiyama Yoshifumi
Published: March 2021

The Fukushima Daiichi Nuclear Power Plant (FDNPP) accident released the largest quantity of radiocaesium into the terrestrial environment since the Chernobyl nuclear accident. The surrounding land received 2.7 PBq of radiocaesium to forests, agricultural lands, grasslands, and urban areas, from which the radionuclides migrated through soil and waterways. In this presentation, the deposition and distribution of radionuclides, especially radiocaesium, in the terrestrial environment as a result of the FDNPP accident are discussed based on the past 10 years' intensive dataset. Anthropogenic activities such as rice and vegetable cultivation and residential activities in the upstream area have led to a rapid decline in the activity concertation of 137Cs of suspended sediment (SS) transport in the river network, and these declines directly control the dissolved 137Cs concentration in the river water. We outline the environmental and anthropogenic factors that influenced the subsequent transport and impacts of radionuclides through the environment. The environmental aftermath of the accident at Fukushima is compared to Chernobyl, and the relatively rapid remediation of the Fukushima region relative to the region surrounding Chernobyl will be explained.
Characterising the effect of submarine iceberg melting on glacier-adjacent water properties
Authors: Davison Ben
Published: March 2021

Ocean-driven retreat of Greenland’s tidewater glaciers remains a large uncertainty in predictions of sea level rise, partly due to limited constraints on glacier-adjacent water properties. Icebergs are likely important modifiers of fjord water properties, yet their effect is poorly understood. Here, we use a 3-D ocean circulation model coupled to a submarine iceberg melt module to investigate the effect of submarine iceberg melting on glacier-adjacent water properties in a range of idealised settings. Icebergs can modify glacier adjacent water properties in three principle ways: (1) substantial cooling and modest freshening in the upper ~50 m of the water column; (2) warming of Polar Water due to iceberg-induced upwelling of warm Atlantic Water, and; (3) the Atlantic Water layer warms on average when vertical temperature gradients through the Atlantic Water layer are steep (due to vertical mixing of warm water at depth), but cools on average when vertical temperature gradients are shallow. When icebergs extend to-or-below sill depth, they can cause cooling throughout the entire water column. All of these effects are more pronounced in fjords with higher iceberg concentrations and deeper iceberg keel depths. These results characterise the important role of icebergs in modifying ice sheet – ocean interaction and highlight the need to improve representations of fjord processes in ice sheet-scale models.
Estimate of equilibrium climate sensitivity and uncertainties by using observations and CMIP6 global coupled climate models
Authors: Chenal Jonathan , Meyssignac Benoit
Published: March 2021

Energy budget estimates of the effective climate sensitivity (effCS) are derived based on estimates of the historical forcing and of observations of the sea surface temperature variations and the ocean heat uptake. Recent revisions to Greenhouse gas forcing and aerosol forcing estimates are included and the data is extended to 2018. We consider two different approaches to derive the effCS from the energy budget: 1) a difference of the energy budget between the recent period 2005-2018 and a base period 1861-1880 (following Sherwood 2020) and 2)  a regression of the differential form of energy budget over the period 1955-2017 (following Gregory et al. 2020). These estimates of the effCS over the historical period are representative of the climate feedback experienced by the climate during the historical period. When accounting for the uncertainty in the forcing, the surface temperature and the ocean heat uptake estimates plus the uncertainty due to the internal variability we find a range of effCS of [1.0;9.7] (at the 95%CL) with a median of 2.0 K with approach (1) and [1.2;2.7] with a median of 1.7 K with approch (2). We find that the lower and the upper tail of the distribution in effCS arise dominantly from the uncertainty in the historical forcing, particularly for the regression method, and at a lower extent for the difference method. This is consistent with previous studies (e.g. Lewis and Curry 2018 and Sherwood et al. 2020).

Using the same approach based on historical observations but accounting for the pattern effect and the temperature dependence of the feedback estimated with climate model simulations, we derive new estimates of the effECS that should encompass the equilibrium climate sensitivity (assuming that climate model simulate properly the pattern effect and the temperature dependence of feedback). We find that adding the pattern effect and the temperature dependence of the feedbacks shifts upwards the median of the effECS and increases significantly the uncertainty range. For the difference method, the median is now 2.5 K and the uncertainty range [1.1;17.2]. For the regression method the median is now 2.0 K and the uncertainty range is [1.2;4.7] K ((5-95%). On the overall, we find that the regression method performs better to constraint the equilibrium climate sensitivity and that the major source of uncertainties comes from the differences in the simulation of the pattern effect among climate models rather than the uncertainties on the historical forcing.
Predicted bulk compositions and geodynamical properties of terrestrial exoplanets in the Solar neighbourhood
Authors: Spaargaren Rob , Wang Haiyang , Ballmer Maxim , Mojzsis Stephen , Tackley Paul
Published: March 2021

Our knowledge of the physical, chemical, and mechanical (i.e., rheological) properties of terrestrial planets is based almost entirely on our Solar System. Terrestrial exoplanets, however, show a startling diversity compared to our local experience. This observation challenges our understanding of terrestrial planet formation and of the thermal and mechanical behaviour of such worlds, some of which are vastly different from our own. To better understand the range and consequences of exoplanetary diversity, we integrate results from astrophysical models and observations, geodynamical simulations, and petrological experiments. Terrestrial exoplanet modelling requires plausible constraints to be placed on bulk planet compositions; bulk composition modulates interior properties, including core size, mantle mineralogy, and mantle melting behaviour. This may in turn affect the interaction between the planet’s interior and atmosphere, and thereby impact its potential to host a biosphere. Bulk composition may leave a signature on the mass and composition of the atmosphere, which could be detected in the future.

Here, we constrain exoplanetary diversity in terms of bulk planet composition, based on observations of stellar abundances in the Solar neighbourhood. We apply the devolatilization/fractionation trend between a planet and its host star [Wang+, 2019], to stellar abundances from the Hypatia catalogue [Hinkel+, 2014]. After applying a simplified model of rock-metal differentiation, we predict bulk planet and bulk silicate compositions of hypothetical exoplanets in the habitable zones of nearby stars. We further select 20 end-member compositions that span the full range of hypothetical bulk compositions based on our analysis.

With the compositions of these 20 end-members and by assuming Earth-like planetary masses and radii, we infer mineralogy and density profiles, as well as physical properties (e.g., viscosity) of the mantle using thermodynamic model Perple_X [Connolly, 2005]. These profiles and physical properties are prescribed in geodynamical models of exoplanet mantle evolution. We use convection code StagYY [Tackley, 2008] to model mantle convection and surface tectonic behaviour in a 2D spherical annulus geometry. We find that mantle viscosity increases with decreasing Mg:Si ratio of mantle rocks, with strong effects on planetary cooling and the likelihood of plate tectonics. In turn, the propensity of plate tectonics regulates the heat and chemical exchange between mantle and crust, affecting surface conditions and, by extension, atmospheric composition. This establishes a link between interior composition and surface conditions, and shows the importance of studying this aspect of planetary diversity. We recommend our 20 suggested end-members of terrestrial exoplanet compositions for subsequent modelling work.
The ionospheric response to the 2019 and 2021 Northern Hemisphere SSWs
Authors: Siddiqui Tarique Adnan , Yamazaki Yosuke , Stolle Claudia
Published: March 2021

Owing to the progress that have been made in understanding the vertical coupling mechanisms in the last decade, it is now well established that the thermosphere-ionosphere system under quiet geomagnetic conditions is highly sensitive to lower atmospheric forcing.  In this regard, the studies linking the upper atmosphere (mesosphere-lower thermosphere-ionosphere) variability and sudden stratospheric warming (SSW) events have been particularly important. The changes to atmospheric circulation due to SSW events modulate the spectrum of vertically upward propagating atmospheric waves (gravity waves, tides, and planetary waves) resulting in numerous changes in the state of the upper atmosphere. Much of our understanding about the upper atmospheric variability associated due to SSWs events have been gained by studying the 2008/2009 Northern Hemisphere (NH) SSW event, which occurred under extremely quiet geomagnetic conditions. Recently, two major NH SSW events in the winter of 2018/2019 and 2020/2021 occurred under similarly quiet geomagnetic conditions. In this work, both these SSW events have been simulated using Whole Atmosphere Community Climate Model with thermosphere and ionosphere extension (WACCM-X) and the low- and mid-latitude ionospheric response to both these SSW events will be presented.
Investigating the hydrogeological controls of an ephemeral stream’s flow regime on an alluvial fan in an ecologically important setting in North West England
Authors: Blackburn Joel , Comte Jean-Christophe , Foster Gez , Gibbins Christopher
Published: March 2021

Ephemeral streams play a key role in supplying water and sediment which are of high ecological importance for their permanent tributaries. The upper River Ehen (the Lake District, North West England) is the focus of a habitat restoration initiative to conserve populations of the endangered freshwater mussel (Margaritifera margaritifera). A previously diverted ephemeral stream, Ben Gill, was restored to its original course over a small alluvial fan (0.075 km2) connecting to the River Ehen to reactivate sediment supply and improve the habitat for freshwater mussels. Like most temporary streams situated on alluvial fans, the flow regime and sediment dynamics of Ben Gill are strongly influenced by fan sedimentary characteristics and interactions with its shallow groundwater aquifer.

This study combined high spatial resolution, near surface geophysics and outcrop data with hydrological data to characterise the hydrogeological properties of the alluvial fan and further develop a hydrological conceptual model of the fan to understand Ben Gill stream flow regimes and sediment supply to the River Ehen.

The conceptual model showed the alluvial fan aquifer was highly productive at the fan apex and along buried palaeochannels, whilst reduced aquifer productivity occurred towards the fan margins. When the volume of water entering the fan apex (via a perennial stream) reached ~60l/s, the fan apex infiltration rate was exceeded resulting in ephemeral flows. This typically occurred following rainfall events >9-11 mm. During flows, significant infiltration occurred along much of the ephemeral channel, though a less permeable zone was observed in the mid-fan. In the lower reaches of the ephemeral channel, groundwater levels sometimes exceeded streambed levels resulting in groundwater discharge into the stream during prolonged wet periods. Connectivity between the ephemeral stream and the River Ehen occurs for approximately 20% of the year.

Numerical hydrogeological modelling of the fan is underway to integrate data on groundwater and streamflow dynamics and associated sediment export from the ephemeral stream. This will help gain a predictive understanding of the streams flow regime and its long-term impacts on the River Ehen, which in turn, will determine the success of the restoration initiative.
On the potential of multi-source remote sensing data in characterizing the Total Suspended Matter variability in inland waters.
Authors: Ciancia Emanuele , Campanelli Alessandra , Lacava Teodosio , Palombo Angelo , Pascucci Simone , Pergola Nicola , Pignatti Stefano , Satriano Valeria , Tramutoli Valerio
Published: March 2021

The assessment of TSM spatiotemporal variability plays a key role in inland water management, considering how these fluctuations affect water transparency, light availability, and the physical, chemical, and biological processes. All the above-mentioned topics highlight the need to develop innovative methodologies of data analysis that are able to handle multi-mission and multi-source remote sensing data, fostering the implementation of integrated and sustainable approaches. Sentinel-2A multispectral instrument (MSI) and Landsat 8 operational land instrument (OLI) data offer unique opportunities for investigating certain in-water constituents (e.g., TSM and chlorophyll-a) mainly owing to their spatial resolution (10–60 m). Furthermore, the joint use of these sensors offers the opportunity to build time series with an improved revisiting time thus enabling limnologists, aquatic ecologists and water resource managers to enhance their monitoring efforts. In this framework, the potential of MSI–OLI combined data in characterizing the multi-temporal (2014–2018) TSM variability in Pertusillo Lake (Basilicata region, Southern Italy) has been evaluated in this work. In particular, a customized MSI-based TSM model (R2=0.81) has been developed and validated by using ground truth data acquired during specific measurement campaigns. The model was then exported on OLI data through an inter-calibration procedure (R2=0.87), allowing for the generation of a TSM multi-temporal MSI–OLI merged dataset. The analysis of the derived multi-year TSM monthly maps has shown the influence of hydrological factors on the TSM seasonal dynamics over two sub-regions of the lake, the west and east areas. The western side appears more affected by inflowing rivers and water level fluctuations, whose  effects  tend to longitudinally decrease, leading to less sediment within the eastern sub-area. The achieved results highlight how the proposed methodological approach (i.e. in situ data collection, satellite data processing and modeling) can be exported in other inland waters that deserve to be investigated for a better management of water quality and monitoring systems.
Magnetostratigraphic dating of the Paleogene synorogenic sediments of the NE sector of the Ebro Foreland Basin (Spanish Pyrenees)
Authors: Peigney Charlotte , Beamud Elisabet , Gratacós Òscar , Roca Eduard , Sáez Alberto , Valero Luis , Muñoz Josep Anton
Published: March 2021

In foreland settings at the front of active orogens, the aggradation/progradation of fluvial fans and sedimentary changes in lacustrine systems depends greatly on the tectonic activity and the derived drainage pattern changes in the hinterland. As a result of the emplacement and erosion of the South-Pyrenean thrust sheets, a system of N-S fluvial fans prograded into the Ebro foreland basin from late Eocene to Oligocene times. After the synorogenic deposition of the Priabonian (late Eocene) marine evaporites of the Cardona Fm, the Ebro Basin was characterized by internal drainage, with the fluvial fans grading to lacustrine systems at the center of the basin, which developed and migrated in response to subsidence changes. All these deposits were deformed by variably oriented salt-detached folds, evidencing the basinwards propagation of the deformation. In this work, we study the Solsona-Sanaüja fluvial fan system by means of litostratigraphy and magnetostratigraphy aiming to determine the age of the transition from fluvial fan to lacustrine systems in the NE sector of the Ebro Basin. The precise dating of this succession reveals causal relationships between tectonic and climatic processes affecting the source-to-sink system, including changes in the depositional style linked to the evolution of the Pyrenean fold and thrust belt.

Our new magnetostratigraphic study consisted in the sampling and analysis of 195 samples along a ca. 1800m thick stratigraphic section of the late Eocene-Oligocene succession in the northern limb of the NW-SE oriented Sanaüja Anticline. Our results show overall Priabonian to Rupelian ages for the succession, considering an age of 36 Ma. (C16n) for the top of the Cardona Fm from previous magnetostratigraphic studies. This allows dating the end of the evaporitic sedimentation (top of the Barbastro Fm) as Priabonian and establishing a late Priabonian to early Rupelian (C13r) age for the transition from the younger lacustrine deposits (Torà Fm) to the continuous and most important fluvial fan episode of progradation in the study area. The final progradation of the fluvial fan system was coeval to a tectonically controlled reorganization of the drainage pattern of the basin responding to the emplacement of the South-Pyrenean thrust sheets. Meanwhile, smaller scale (hectometric-decametric) alternation between lacustrine and alluvial deposits was possibly driven by climatic changes related to orbital eccentricity cycles. The correlation and integration of these results with previous magnetostratigraphic studies in the area can help analyzing sedimentation patterns and architectural changes in the basin margins at a regional scale.
Do Enhanced Seismicity Catalogs Improve Aftershock Forecasts? A Test on the 2016-2017 Central Italy Earthquake Cascade
Authors: Mancini Simone , Segou Margarita , Werner Maximilian J.
Published: March 2021

Artificial intelligence methods are revolutionizing modern seismology by offering unprecedentedly rich seismic catalogs. Recent developments in short-term aftershock forecasting show that Coulomb rate-and-state (CRS) models hold the potential to achieve operational skills comparable to standard statistical Epidemic-Type Aftershock Sequence (ETAS) models, but only when the near real-time data quality allows to incorporate a more detailed representation of sources and receiver fault populations. In this framework, the high-resolution reconstructions of the seismicity patterns introduced by machine-learning-derived earthquake catalogs represent a unique opportunity to test whether they can be exploited to improve the predictive power of aftershock forecasts.

Here, we present a retrospective forecast experiment on the first year of the 2016-2017 Central Italy seismic cascade, where seven M5.4+ earthquakes occurred between a few hours and five months after the initial Mw 6.0 event, migrating over a 60-km long normal fault system. As target dataset, we employ the best available high-density machine learning catalog recently released for the sequence, which reports ~1 million events in total (~22,000 with M ≥ 2).

First, we develop a CRS model featuring (1) rate-and-state variables optimized on 30 years of pre-sequence regional seismicity, (2) finite fault slip models for the seven mainshocks of the sequence, (3) spatially heterogeneous receivers informed by pre-existing faults, and (4) updating receiver fault populations using focal planes gradually revealed by aftershocks. We then test the effect of considering stress perturbations from the M2+ events. Using the same high-precision catalog, we produce a standard ETAS model to benchmark the stress-based counterparts. All models are developed on a 3D spatial grid with 2 km spacing; they are updated daily and seek to forecast the space-time occurrence of M2+ seismicity for a total forecast horizon of one year. We formally rank the forecasts with the statistical scoring metrics introduced by the Collaboratory for the Study of Earthquake Predictability and compare their performance to a generation of CRS and ETAS models previously published for the same sequence by Mancini et al. (2019), who used solely real-time data and a minimum triggering magnitude of M=3.

We find that considering secondary triggering effects from events down to M=2 slightly improves model performance. While this result highlights the importance of better seismic catalogs to model local triggering mechanisms, it also suggests that to appreciate their full potential future modelling efforts will likely have to incorporate also fine-scale rupture characterizations (e.g., smaller source fault geometries retrieved from enhanced focal mechanism catalogs) and introduce denser spatial model discretizations.
A shallow Vs model from full wave inversion for hydraulic fracturing site 
Authors: Li Guoliang , Chen Min
Published: March 2021

In recent years, small dense arrays with inter-station distances ~1-km are widely deployed for various geotechnical proposes, including exploring the subsurface geothermal reservoirs, monitoring the hydraulic fracturing, and estimate the local seismic hazards. Those small-dense arrays record several hours or days microtremor datasets and can be used to extract noise H/V ratio and short-period Rayleigh wave dispersion curve. To fulfill those geotechnical purposes, the extracted H/V ratio and Rayleigh wave dispersive curves are used to invert for 1-D layered velocity structures based on traditional ray theory, ignoring the 3-D Rayleigh wave propagating effects. In the present-day, with advances in computational power, 3-D numerical seismic wave propagation in realistic Earth models has become feasible and this has led to efforts to invert full waveforms. However, as H/V ratios from microtremors are produced by multiple random sources close to the surface with complex scattering effects, they are still unrealistic to be simulated by 3-D numerical seismic wave simulations. In this study, we use a strategy to incorporate the theories of H/V ratios from microtremor and the 3-D waveform simulations to invert for shallow sub-surface speed model using a small array. The details of the strategy are that we first use the traditional method to build an initial speed model by jointly inverting the Rayleigh wave dispersion curves and H/V ratios, and then, we further update the initial model with full-wave inversion of the Rayleigh waveforms calculated from ambient noise cross-correlations. The small array used here was composed of 21 broadband seismic stations, aimed to monitor the underground hydraulic fracturing. Therefore, the newly build model has important geotechnical usages of locating stimulated micro-seismic events and diagnose the hydraulic fracturing effects.
Investigating the possible measure to protect groundwater from polluted streams in Arid and Semi-Arid Regions: the Eastern Nile Delta case study
Authors: Abd-Elaty Ismail , Zelenakova Martina , Straface Salvatore , Vranayová Zuzana , Abu-hashim Mohamed , Negm Abdelazim , Scozzari Andrea
Published: March 2021

Groundwater is the main source of drinking water in the Nile Delta. Unfortunately, it might be polluted by seepage from polluted streams. This study was carried out to investigate the possible measures  to  protect groundwater  in the Nile delta aquifer using a numerical model (MT3DMS - Mass Transport 3-Dimension Multi-Species). The sources of groundwater contamination were identified and the total dissolved solids (TDS) was taken as an indicator for the contamination. Different strategies were investigated for mitigating the impact of polluted water: i) allocating polluted drains and canals in lower permeability layers; ii)  installing cut-off walls in the polluted drains, and finally, iii) using lining materials in polluted drains and canals. Results indicated these measures effective to mitigate the groundwater pollution. In particular, the cut-off wall was effective for contamination reduction in shallow aquifers, whereas it had no effect in the deep aquifer, while lining materials in polluted drains and canals were able to prevent contamination and to protect the freshwater in the aquifers.  It is worth mentioning that this study was partially supported by a bilateral project between ASRT (Egypt) and CNR (Italy).

 

 