bluuebunny/crossref_metadata_2025 huggingface dataset:
Seismic surveys at an artificially created field-test cavern within a salt pillar
Authors: Richter Heike , Giese Rüdiger , Zirkler Axel , Strauch Bettina
Published: March 2020

Salt rocks serve as host rock for technical caverns due to their impermeability but their can also be influenced by fluid migration due to geological fracture zones. Seismic methods can be used to monitor cavernous structures in the transition zone between cavity and undisturbed salt rocks. Around an artificially created cavity (field-test cavern) in a salt pillar with a volume of approximately 100 litre, travel time tomography was utilized to image structures related to caverns and fluid-storage. Seismic surveys were performed at different stages of an experimental simulation of gas-water-rock interaction in the field-test cavern aiming for a better understanding of the multiphase system in the cavern-near area. The baseline survey (1) was carried out using 8 three-component piezo-electrical sensor rods and a seismic vibrator source at the surface of the salt pillar, first without an installed field-test cavern. After drilling and installing the field-test cavern, seismic cross-hole measurements were performed after producing partial vacuum in the test cavern (2) and infill of gas (3) and water (4). To finalize the field experiments the last seismic survey (5) was again conducted at the surface of the salt pillar as a repeat measurement to the baseline survey. The seismic monitoring of the salt pillar was carried out in a frequency range of 100 Hz to 14000 Hz allowing a spatial resolution in the cm-range. This was followed by pre-processing of the seismic data sets to apply the picked travel times in a tomography program. On the basis of the tomography results and reflection seismic data we want to assess the potential enlargement of the field-test cavern due to water-infill and to image the differences between unaffected salt rocks, cavernous structures and developing transition zones.
Hydroclimatic fluctuation in Lake Yakhi, eastern Mongolia
Authors: Orkhonselenge Alexander , Bulgan Odmaa , Gerelsaikhan Dashtseren , Davaagatan Tuyagerel , Altansukh Nyamdorj
Published: March 2020

This study aims to reconstruct paleoclimate change in eastern Mongolia inferred from sedimentological and geochronological records from Lake Yakhi in the drainage basin of the Pacific Ocean. In a context of the study goal the hydroclimatic fluctuation in eastern Mongolia resulted from Lake Yakhi is presented here. Result from changes in lake area of Lake Yakhi shows it decreased from 79.72 km2 in 1970 to 53.76 km2 in 1986 and 35.03 km2 in 2018. The hydraulic dynamics and field observation show that Lake Yakhi is shifting into a playa lake. For shrinking Lake Yakhi, shifting toward a playa lake is directly related to the global warming, i.e., it implies the lake is extremely sensitive to climate change in the late Holocene. This coincides with those conditions of large lakes in the Govi region in southern Mongolia (Orkhonselenge et al., 2018). The major element compositions of the lake sediments show that the core Y18-1 is dominated by SiO2, Al2O3, K2O and Na2O, while the cores Y18-2 and Y18-3 largely contain SiO2, Al2O3, CaO and Fe2O3. In addition to the dominant semimetal and transition metal, presence of oxides of alkali earth metals in the core Y18-1 and of alkaline earth metals in the cores Y18-2 and Y18-3 show a derivation of intermediate sedimentary and volcanic rocks in the drainage basin of Lake Yakhi. This coincides with the tectonostratigraphic terrane structure of the cratonal clastic sedimentary rocks (Badarch et al., 2002) in the Lake Yakhi area. Further detail geomorphological and geochronological records from Lake Yakhi would not review only the hydrogeochemical evolution, but the paleoclimate changes in eastern Mongolia. Leading the dates would precisely determine the paleohydroclimatic fluctuations in eastern Mongolia.
Modulation of the solar wind driven ion escape from unmagnetized planets by ultra-low-frequency foreshock waves in a global hybrid simulation
Authors: Jarvinen Riku , Kallio Esa , Pulkkinen Tuija
Published: March 2020

We study the solar wind interaction with Venus in a 3-dimensional global hybrid model where ions are treated as particles and electrons are a charge-neutralizing fluid. We concentrate on large-scale ultra-low frequency (ULF) waves in the ion foreshock and how they affect the energization and escape of planetary ions. The ion foreshock forms in the upstream region ahead of the quasi-parallel bow shock, where the angle between the shock normal and the magnetic field is smaller than about 45 degrees. The magnetic connection with the bow shock allows backstreaming of the solar wind ions leading to the formation of the ion foreshock. This kind of beam-plasma configuration is a source of free energy for the excitation of plasma waves. The foreshock ULF waves convect downstream with the solar wind flow and encounter the bow shock and transmit in the downstream region. We analyze the coupling of the ULF waves with the planetary ion acceleration and compare Venus and Mars in a global hybrid simulation.
Combined application of manure and mineral fertilizers weakens the impact of manure on soil biochemical properties
Authors: Liu Shibin , Kuzyakov Yakov , Pu Shengyan , Razavi Bahar
Published: March 2020

Manure application has been considerably emphasized to mitigate global soil degradation and improve soil fertility. Though there have been investigations on the contribution of manure application on soil properties in comparison with mineral fertilization, a comprehensive understanding of manure application on soil organic matter (SOM), total nitrogen (TN), microbial biomass carbon (MBC) and nitrogen (MBN) and activities of 7 enzymes is yet to be identified. This study extensively quantified the response of soil biochemical properties to manure application based on a meta-analysis of 83 articles including 460 observations with time span from days to years. The impact of explanatory factors (i.e. climatic factors, experimental types, soil properties and manure characteristics) was also elucidated. Manure application increased SOM, TN, MBC and MBN by 27 ± 3% and 41 ± 5.3%, 87 ± 4.3% and 88 ± 6.7 %. Soil C/N ratio did not vary but MBC/MBN ratio decreased after manure application, indicating a shift in microbial community. The activities of β-glucosidase, dehydrogenase, acid phosphatase, alkaline phosphatase, N-acetyl-β-D-glucosaminidase, urease and sulfatase were also elevated by 150%, 110%, 40%, 110%, 59%, 106% and 221%, respectively. Besides, all soils were neutralized following manure application, suggesting that manure accelerates soil nutrient cycling by adjusting pH to optimum. When mean annual temperature is within the range of 10-20 °C or initial soil pH within 6-8, the highest increase of enzyme activities was revealed. Furthermore, composting manure has stronger impact on soil enzyme activities compared to non-composted manure, which was attributed to beneficial microbial community composition as well as favourable soil organic compound composition in the compost. Contrarily, combined application of manure with mineral fertilizers induces an antagonistic effect and weakens the impact of manure on soil biochemical properties as compared to only manure application. This weakening effect may mitigate the competition between microbes and plant roots for nutrients. In conclusion, necessary differentiation of only manure and manure + chemical fertilizers application is required when developing and modeling the influence of management practices on arable lands.
A Stochastic Framework to Optimize the Monitoring Strategy for the Delineation of a Groundwater Divide
Authors: Allgeier Jonas , Gonzalez-Nicolas Ana , Erdal Daniel , Nowak Wolfgang , Cirpka Olaf A.
Published: March 2020

The boundaries of surface-water catchments can be delineated by analyzing digital elevation models using geographic information systems. Surface-water divides and groundwater divides, however, might significantly differ from each other because the groundwater surface does not necessarily follow the surface topography. Hydraulic-head measurements are needed to properly delineate a groundwater divide and thereby the subsurface boundary of a catchment, but piezometers are expensive. It is therefore vital to optimize the placement of the necessary piezometers. In this work, we introduce an optimal design analysis, which can identify the best configuration of potential piezometer placements within a given set. The method is based on the formal minimization of the expected posterior uncertainty within a sampling-based Bayesian framework. It makes use of a random ensemble of behavioral steady-state groundwater flow models. For each behavioral realization we compute virtual hydraulic-head measurements at all potential well points and delineate the groundwater divide by particle tracking. We minimize the uncertainty of the groundwater-divide location by marginalizing over the virtual measurements. We test the method mimicking a real aquifer in South-West Germany. Previous works in this aquifer indicated a groundwater divide that is shifted compared to the surface-water divide. The analysis shows that the uncertainty in the localization of the groundwater divide can be reduced with each new well. A comparison of the maximum uncertainty reduction at different numbers of wells quantifies the added value of information for each new well. In our case study, the uncertainty reduction obtained by three monitoring points is maximized when the first well is close to the topographic surface water divide, the second one in the valley, and the third one in between. 
Towards zero emission geothermal plants in the framework of the H2020 GECO project: Insights on gas re-injection in geothermal reservoir and serpentinite carbonation from batch reactor experiments
Authors: Bicocchi Gabriele , Orlando Andrea , Ruggieri Giovanni , Borrini Daniele , Rielli Andrea , Boschi Chiara
Published: March 2020

The EU H2020 GECO (Geothermal Emission Gas Control) project is aimed to produce new technologies to limit emissions from geothermal power generation by either gas re-injection or its use to produce commercial material through serpentinite carbonation. In this framework, the realization of a closed loop geothermal power plant has been planned in the Lardello geothermal area (Italy), where gas will be re-injected in a reservoir constituted by phyllites and micaschists.

A set of water-gas-rock interaction experiments was performed in order to: i) investigate the interaction between CO2-H2S gas mixture, representative of the geothermal fluids exploited at Larderello, and phyllites and micaschists of the reservoir ii) optimize the conditions for CO2 mineral sequestration by reacting CO2-H2S gas mixture with different serpentinised ultramafic rocks buried in the nearby area. During the experiments, rock powder suspended in ultrapure ion-free MilliQ® water were reacted with a gas phase (CO2-H2S=98-2% or CO2=100%) in a PARR 5500 HP stirred reactor at P-T conditions ranging from 20 to 60 bar and 90 to 250 °C, respectively. The liquid phase resulting from the experiments was analysed via ion chromatography and ICP-MS to determine ion contents, whilst rock and rock powder were examined with SEM-EDS and EPMA to identify mineral phases and determine mineral chemistry.

Preliminary results highlighted that H2S plays a pivotal role in controlling the reaction pathways with phyllites and micaschists, allowing the formation of pyrite in a wide range of P-T conditions. This process induces a selective removal of Fe from the solution, while the exceeding SiO2 deriving from mica and chlorite alteration re-precipitate as quartz. In this experiment, carbonate precipitation is prevented by the low Ca and Mg content of the samples and by the high water to rock ratio constrained by the experimental set-up. Experiments with ultramafic rocks were performed using serpentinised harzburgite and brucite-rich dunite in order to identify the most reactive lithology for mineral carbonation. Preliminary results show that CO2 sequestration is strongly enhanced by the presence of brucite compared to serpentine but further experiments are required to establish the most efficient reaction conditions.

This research is supported by European Horizon 2020 “GECO” project (Grant n° 818169).
Global imaging of the lithosphere-asthenosphere system
Authors: Debayle Eric , Ricard Yanick , Durand Stéphanie , Bodin Thomas
Published: March 2020

Massive surface wave datasets constrain upper mantle seismic heterogeneities with horizontal wavelengths larger than 1000 km, allowing us to investigate the large-scale properties and alignment of olivine crystals in the lithosphere and asthenosphere. The azimuthal anisotropy projected onto the direction of present plate motion shows a very specific relation with the plate velocity. Plate-scale present-day deformation is remarkably well and uniformly recorded beneath plates moving faster than ∼4 cm/yr. Recent geodynamic models suggest that cold sinking instabilities tilted in the direction opposite to plate motion below fast plates could produce a pattern of large-scale azimuthal anisotropy consistent with our observations. Beneath slower plates, plate-motion aligned anisotropy is only observed locally, which suggests that the lithospheric motion does not control mantle flow below these plates.

Radial anisotropy extends deeper beneath continents than beneath oceans, but we find no such difference for azimuthal anisotropy, suggesting that beneath most continents, the alignment of olivine crystal is preferentially horizontal and azimuthally random at large scale. As most continents are located on slow moving plates, this supports the idea that azimuthal anisotropy aligns at large scale with the present plate motion only for plates moving faster than ∼4 cm/yr.

The same inversion also provides 3D models of seismic velocity and attenuation. The simultaneous interpretation of global 3D shear attenuation and velocity models has a great potential to decipher the effect of temperature, melt and composition on seismic observables. We will discuss our findings from the simultaneous interpretation of our latest models.
Consolidation of Aeolus FMA and FMB datasets in the DSI X-PReSS Consortium: Methodology used to generate Master Datasets and the results that have been achieved
Authors: Comparetti Nicola , Colamussi Gianluca , De Laurentis Marta , Douzal Michel , Fischer Peggy , Paciucci Alessandra , Schipperijn Bart , Smeets Joost , Veneziani Marcella
Published: March 2020

We present the methodology and results of the Aeolus VC01 and L0 FM-A and FM-B datasets consolidation performed by the X-PReSS team as part of the ESA (European Space Agency) Data Service Initiative (DSI) managed by ESA’s Ground Segment Operations Division. The goal of this activity is to generate master datasets and gap lists as well as assess data completeness for both future ESA reprocessing campaigns and data preservation activities. The consolidation was carried out first by removing fully overlapping products, products completely covered by other products (inside) and black-listed products. Secondly, remaining products HDR and DBL files were scanned to detect filename misalignments with specifications, intra-products and inter-products gaps and corrupted products. Ancillary data from several Aeolus facilities (KSAT, DISC, FOS, PDGS) were used for gaps justification and blacklisted products identification. For FM-A VC01, 4219 products were analysed. Out of these, 3927 were classified as Master, 142 as inside, 3 as Duplicates and 147 as Blacklisted. 57 gaps were found. No data corruption was found. No duplicated source packet data was found. Consolidation results are available at ESA and includes: list of gaps with metadata and known justification,  list of duplicated events with metadata, list of Instrument Function IDs with metadata, master dataset list and a list of discarded products including known justification.
Unusually high thermospheric hydrogen density prior to severe storm of September 8, 2017 and its impact on the storm manifestations
Authors: Kotov Dmytro , Richards Philip , Bogomaz Oleksandr , Shulha Maryna , Maruyama Naomi , Fedrizzi Mariangel , Truhlík Vladimír , Lichtenberger János , Hernández-Pajares Manuel , Miyoshi Yoshizumi , Kasahara Yoshiya , Kumamoto Atsushi , Tsuchiya Fuminori , Shoji Masafumi , Matsuoka Ayako , Shinohara Iku , Zhivolup Taras , Emelyanov Leonid , Chepurnyy Yakiv , Domnin Igor
Published: March 2020

Atomic hydrogen plays a key role for the plasmasphere, exosphere, and the nighttime ionosphere. It directly impacts the rate of plasmasphere refilling after strong magnetic storms as atomic hydrogen is the primary source of hydrogen ions. It is the source of the geocorona, which significantly affects ring current decay during the recovery phase of magnetic storms.

Our previous studies with the Kharkiv incoherent scatter radar (49.6 N, 36.3 E), Arase and DMSP satellite missions, and FLIP physical model showed that during magnetically quiet periods of 2016–2018 the hydrogen density was generally a factor of 2 higher than from the NRLMSIS00-E model (Kotov et al., 2018).

Even larger values of thermospheric hydrogen density were detected prior to the severe storm of September 8, 2017. With Kharkiv IS radar, AWDANet whistler receivers, Arase satellite, and TEC data we found that during the nights of September 5 to 6 and September 6 to 7, the thermospheric hydrogen density had to be at least a factor of 4 higher than the values from NRLMSIS00-E model i.e. ~100% higher than expected from our previous studies. We discuss the possible mechanisms that could lead to the increased hydrogen density.

Such high hydrogen densities may be the reason for very quick recovery of inner plasmasphere after the severe depletion by the storm of September 8, 2017 (Obana et al., 2019).

References:

1. Kotov, D. V., Richards, P. G., Truhlík, V., Bogomaz, O. V., Shulha, M. O., Maruyama, N., et al. ( 2018). Coincident observations by the Kharkiv IS radar and ionosonde, DMSP and Arase (ERG) satellites, and FLIP model simulations: Implications for the NRLMSISE‐00 hydrogen density, plasmasphere, and ionosphere. Geophysical Research Letters, 45, 8062– 8071. https://doi.org/10.1029/2018GL079206

2. Obana, Y., Maruyama, N., Shinbori, A., Hashimoto, K. K., Fedrizzi, M., Nosé, M., et al. (2019). Response of the ionosphere‐plasmasphere coupling to the September 2017 storm: What erodes the plasmasphere so severely? Space Weather, 17, 861–876. https://doi.org/10.1029/2019SW002168
Investigations of the Oligocene-Miocene opening of the Ligurian Basin using refraction seismic data
Authors: Kopp Heidrun , Dannowski Anke , Grevemeyer Ingo , Lange Dietrich , Thorwart Martin , Caielli Grazia , Franco Roberto , Petersen Florian , Wolf Felix Noah , Schramm Bettina
Published: March 2020

The Ligurian Basin is located north-west of Corsica at the transition from the western Alpine orogen to the Apennine system. The Back-arc basin was generated by the southeast trench retreat of the Apennines-Calabrian subduction zone. The opening took place from late Oligocene to Miocene. While the extension led to extreme continental thinning and un-roofing of mantle material little is known about the style of back-arc rifting.

To shed light on the present day crustal and lithospheric architecture of the Ligurian Basin, active seismic data have been recorded on short period ocean bottom seismometers in the framework of SPP2017 4D-MB, the German component of AlpArray. An amphibious refraction seismic profile was shot across the Ligurian Basin in an E-W direction from the Gulf of Lion to Corsica. The profile extends onshore Corsica to image the necking zone of continental thinning.

The majority of the refraction seismic data show mantle phases at offsets up to 70 km. The arrivals of seismic phases were picked and inverted in a travel time tomography. The results show a crust-mantle boundary in the central basin at ~12 km depth below sea surface. The mantle shows rather high velocities >7.8 km/s. The crust-mantle boundary deepens from ~12 km to ~18 km within 25 - 30 km towards Corsica. The results do not map an axial valley as expected for oceanic spreading. However, an extremely thinned continental crust indicates a long lasting rifting process that possibly does not initiated oceanic spreading before the opening of the Ligurian Basin stopped.
Tropospheric trace gas slant column densities derived from MAX-DOAS measurements on pacific transit cruises of the German research vessel Sonne in 2019
Authors: Dörner Steffen , Ruhtz Thomas , Donner Sebastian , Beirle Steffen , Kinne Stefan , Wagner Thomas
Published: March 2020

Between January and July 2019 the German research vessel Sonne was on several cruises in the Pacific, crossing the ocean from Suva, Fiji to Manzanillo, Mexico in February (SO267-2) and from Vancouver, Canada to Singapore in June (SO268-3). A Multi Axis-Differential Optical Absorption Spectroscopy (MAX-DOAS) instrument was in operation outside the national exclusive economic zone (EEZ) regions allowing for profile measurements of trace gases and aerosol on the open seas under background conditions. Both transit cruises cover a wide range of marine biomes and climatic zones affecting the trace gas and particle composition of the atmosphere.

Ship measurements of Nitrogen Dioxide (NO2) and Sulphur Dioxide (SO2) are especially important for the validation of satellite measurements as the remote Pacific Ocean is typically used as a reference region. Off the coast of North America an enhanced signal of halogen species, i.e. bromine oxide (BrO) and iodine oxide (IO) was observed. The abundance of formaldehyde (HCHO) and its interrelation with the marine bio-activity could also be observed.
Discovery of radiocesium-bearing microparticles from ocean samples emitted from the Fukushima Daiichi Nuclear Power Plant accident
Authors: Miura Hikaru , Ishimaru Takashi , Ito Yukari , Kanda Jota , Kubo Atsushi , Otosaka Shigeyoshi , Kurihara Yuichi , Tsumune Daisuke , Takahashi Yoshio
Published: March 2020

Introduction: A large amount of radioactive Cs was emitted into the environment by the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident. Adachi et al. (2013) first reported radiocesium-bearing microparticles (CsMPs) from aerosol filters. Subsequent researches showed that the CsMP is SiO2 glass with Cs, Cl, K, Fe, and Zn mainly contained in the particle. Diameter of CsMP is ~1-10 μm and 137Cs radioactivity is ~0.5 to 102 Bq. It has been suggested that the CsMP was mainly emitted from Unit 2 or Unit 3 of FDNPP based on the 134Cs/137Cs activity ratio in the samples. Miura et al. (2018) reported CsMPs from the suspended particles in river water and their effect on Kd value, which suggested CsMPs may exist in the ocean transported through rivers. Kubo et al. (2018) and Ikenoue et al. (2018) reported hot spots in the ocean samples by autoradiography but they did not separate CsMPs from these spots. In this presentation, we first report CsMPs separated from marine suspended particles, sinking particles, and sediments in coastal area of Fukushima and compare them with CsMPs from the terrestrial samples.

Method: We collected suspended particles (2011, 2013, 2015), sinking particles (2014), sediment cores (2011) from coastal area of Fukushima. By a wet separation method (Miura et al., 2018), we separated CsMPs from these samples. After measurement of radioactivity with a high-purity germanium semiconductor detector, scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDS) analyses were performed for separated CsMPs. Using autoradiography, we calculated 137Cs activity of unseparated hot spots over 0.1 Bq, which may be CsMPs.

Results and discussion: We separated 5 CsMPs from marine samples. The results of SEM-EDS analyses showed that these CsMPs have almost similar characteristics to the reported CsMPs because they mainly consist of Si, Cs, Fe, and Zn.  Their 134Cs/137Cs showed that the CsMPs were from Unit 2 or 3 of FDNPP. 137Cs radioactivity per volume is also similar to reported CsMPs from Unit 2 or 3. In this presentation, we will show the effect of CsMPs on Kd values. CsMPs in the ocean samples will make apparent Kd values be higher than intrinsic Kd values related to the adsorption-desorption reaction to the clay minerals, which may explain the large variation of Cs concentration in marine samples.
Evaluation of different erosion models for debris flow modeling
Authors: Lee Seungjun , An Hyunuk , Kim Minseok
Published: March 2020

The shallow landslide-generated debris flow on hillside catchment plays a critical role in the change of landscape features caused by natural hazards. Numerous studies has been conducted on the analysis of the transported and deposited sediments by debris flows that were developed at the hillside catchments. Among these researches, the debris flow numerical modeling approach has an advantage of being able to predict and simulate the movement of the flow over irregular topographic terrains. A number of modeling approaches have been studied to explore the process of debris flow development. However, there are still a lot of uncertainties in the erosion-entrainment process, although several erosion models have been proposed to simulate debris flow. The objective of this study is to test and analyze several erosion models for debris flow simulation. Deb2D model, a two-dimensional debris flow simulation software based on quadtree-grid, is used to simulate the debris flow. The study case was 2011 Mt. Umyeon landslide in the Republic of Korea. The total debris flow volume, maximum velocity and inundated depth generated from Deb2D were compared with the field validation data. In particular, the spatial distribution of erosion depth was extracted from the LiDAR-based DEM data gauged before and after the event to compare the performance of the erosion model. The research showed each erosion model accuracy and shortcomings through comparison with field validation data.

Keywords : debris flow, numerical simulation, entrainment, erosion model, Deb2D
The effect of latent heat transport by waves on Greenland Surface Mass Balance
Authors: Heiskanen Tuomas Ilkka Henrikki , Graversen Rune Grand
Published: March 2020

The Arctic region shows some of the world's most significant signs of climate change. The atmospheric energy transport plays an important role for the Arctic climate; the atmospheric transport contributes an amount of energy into the Arctic that is comparable to that provided directly by the sun. From recently developed Fourier and wavelet based methods it has been found that the planetary component of the latent heat transport affects that Arctic surface temperatures stronger than the decomposed dry-static energy transport and the synoptic scale component of the latent heat transport. 

A large concern for humanity is that the climate change in polar regions will lead to significant melting of the ice sheets and glaciers. In fact the discharge water from the Greenland ice sheet has recently increased to the extent that this ice sheet is one of the major contributorsto sea-level rise. Here we test the hypothesis that the recent rapid increase in melt of the Greenland ice sheet is linked to a shift of planetary-scale waves transporting warm and humid air over the ice sheet.

The effect of the atmospheric energy transport is investigated by correlating the divergence of energy over the Greenland ice sheet with the surface mass balance of this ice sheet. The divergence of latent heat transport is found to correlate positively with the surface mass balance along the edges of the ice sheet, and negatively in the interior. This indicates that a convergence of latent at the edges of the ice sheet lead to a increased mass discharge from the ice sheet, whilst in the interior converging latent heat indicates an accumulation of mass to the ice sheet. 

To investigate the effect of transport by planetary and synoptic scale waves on the Greenland ice sheet surface mass balance the mass flux component of the transport divergence is decomposed into wavenumbers through the application of a Fourier series. The divergences of transport contributions of each wavenumber are then correlated with the surface mass balance of the Greenland ice sheet. The correlations between the surface-mass balance and divergence of transport contributions by different wavenumbers reveals the relative impact of atmospheric circulation systems, such as Rossby waves and cyclones, on the Greenland ice sheet mass balance. Further, identifying shifts in the circulation patterns over Greenland by applying self organizing maps, or similar methods, and investigations of how these circulation patterns affect the energy transport over Greenland by atmospheric waves of different scales are also pursued.
 
  
A multi-disciplinary materials study as a contribtion to evaluate degradation issues of monuments and archaeological sites towards their preservation
Authors: Curulli Antonella , Montesperelli Giampiero , Ronca Sara , Carvalho Fernanda , Veiga Joao P. , Cavalagli Nicola , Ubertini Filippo , Aguas Hugo , Kavoulaki Elisabeth , Padeletti Giuseppina
Published: March 2020

The preservation of archaeological sites, often considered as open-air museum, is a priority and a challenge due to their exposure to environmental actions and natural hazards. Every day, the artifacts populating these sites, which can have either structural or decorative functions, are subjected to continuous degradation processes, related to frost-thaw cycles, humidity and temperature variations, causing a deterioration of the materials mechanical properties. Anthropogenic pressure (visitors, human actions) can acts towards his direction, as well. In order to evaluate the ongoing process of degradation affecting a specific site, the study of the actual conditions of the materials is typically one of the first steps of the analysis. With this perspective, in this work, the results of the investigations carried out on the constituent materials of the Knossos Palace in Crete are presented. The Knossos Palace is one of the most important archaeological sites in Crete. The main excavation work took place at the beginning of the 20th century, directed by Sir Arthur Evans. The importance of this site led him and his collaborators to design and perform preservation actions, which included the reconstruction of relevant parts of the Knossos Palace. In addition for preserving the site, reconstructions were a way of highlighting the palace magnificence and the importance of the Minoan civilization. At that time concrete was already one of the most widely used building material. Considered a durable material, the concrete was used in the construction of reinforcement structures and new architectural elements, often placed in direct contact with the original ones. Nevertheless, the restoration/reconstruction made by Evans, using concrete, is nowadays considered an integral part of the monument and its history, to be studied and protected.

In the context of the HERACLES Project [1], samples of stones and concrete used in the Palace of Knossos were analysed to determine their morphological and chemical characteristics and their mechanical properties. For this purpose, an integrated approach, i.e. the use of several analytical techniques, was considered essential to support the material preservation actions.

[1]European Project HERACLES has received funding from the European Union Framework Programme for Research and Innovation HORIZON 2020 under GA n° 700395

 
Observations of turbulence at a near-surface temperature front in the Arctic Ocean
Authors: Koenig Zoé , Fer Ilker , Kolås Eivind , Fossum Trygve , Norgren Petter , Ludvigsen Martin
Published: March 2020

Measurements made at an Arctic thermohaline front show turbulence production through convection and forced symmetric instability, a mechanism drawing energy from the frontal geostrophic current. Destabilizing surface buoyancy fluxes from a combination of heat loss to the atmosphere and cross-front Ekman transport by down-front winds reduce the potential vorticity in the upper ocean. The front, located in the Nansen Basin close to the sea ice edge, separates the cold and fresh surface melt water from the warm and saline mixed layer. High resolution temperature, salinity, current and turbulence data were collected in the upper 100 m, on 18 September 2018 across the front from a research vessel and an autonomous underwater vehicle. The AUV was deployed to autonomously collect high resolution data across the front using adaptive sampling. Both front detection and sampling location were decided by a state-based autonomous agent running onboard the AUV, optimizing data collection across and along the front.

In addition to convection by heat loss to atmosphere and mechanical forcing by moderate wind in the mixed layer, forced symmetric instability contributed with comparable magnitude in generation of turbulence at the front location down to 40 m depth. This turbulence was associated with turbulent heat fluxes of up to 10 W.m-2, eroding the warm and cold intrusions observed at respectively 35 and 55 m depth. A similar frontal structure has been crossed by a Seaglider in the same region 10 days after our survey. The submesoscale-to-turbulence scale transitions and resulting mixing can be widespread and important in the Atlantic sector of the Arctic Ocean.
Modelling the source of glacial earthquakes for a better understanding of the impact of iceberg capsize on glacier stability
Authors: Bonnet Pauline , Yastrebov Vladislav , Leroyer Alban , Queutey Patrick , Mangeney Anne , Castelneau Olivier , Stutzmann Eleonore , Montagner Jean-Paul , Sergeant Amandine
Published: March 2020

One current concern in climate science is the estimations of the amount of ice loss by glaciers each year and the corresponding rate of sea level rise. Greenland ice sheet contribution is significant with about 30% to the global ice mass losses. Ice loss in Greenland is distributed approximately equally between loss in land by surface melting and loss at the front of marine-terminating glaciers that is modulated by dynamic processes. Dynamic mass loss includes both submarine melting and iceberg calving. The processes that control ablation at tidewater glacier termini, glacier retreat and calving are complex, setting the limits to the estimation of dynamic mass loss and the relation to glacier dynamics. It involves interactions between bedrock – glaciers – icebergs – ice-mélange – water – atmosphere. Moreover, the capsize of cubic kilometer scale icebergs close to a glacier front can destabilize the glacier, generate tsunami waves, and induce mixing of the water column which can impact both the local fauna and flora.

We aim to improve the understanding of iceberg capsize using a mechanical modeling of iceberg rotation against the glacier terminus, constrained by the generated seismic waves that are recorded at teleseismic distances. To achieve this objective, we develop a fluid-structure interaction model for the capsizing iceberg. Full scale fluid-structure interaction models enable accurate simulation of complex fluid flows in presence of rigid or deformable solids and in presence of free surfaces. However, such models are computationally very expensive. Therefore, our strategy is to construct a simple solid dynamics model involving contact and friction, whose simplified interaction with water is governed by parametrized forces and moments. We fine tune these parametrized effects on an iceberg capsizing in contact with a glacier with the help of reference direct numerical simulations of fluid-structure interactions involving full resolution of Navier-Stokes equations. We assess the sensitivity of the glacier dynamics to the glacier-bedrock friction law and the conditions for triggering a stick-slip motion of the glacier due to iceberg capsize. The seismogenic sources of the capsizing iceberg in contact with a glacier simulated with our model are then compared to the recorded seismic signals for well documented events.
Antarctica crustal model by means of the Bayesian gravity inversion
Authors: Capponi Martina , Sampietro Daniele
Published: March 2020

The Antarctica crustal structure is still not completely unveiled due to the presence of thick ice shields all over the continent which prevent direct in situ measurements. In the last decades, various geophysical methods have been used to retrieve information of the upper crust and sediments distribution however there are still regions, especially in central Antarctica, where our knowledge is limited. For these kind of situations, in which the indirect investigation of the subsurface is the only valuable solution, the gravity data are an important source of information. After the recent dedicated satellite missions, like GRACE and GOCE, it has been possible to obtain global gravity field data with spatial resolution and accuracy almost comparable to those of local/regional gravity acquisitions, paving the way to new geophysical applications. The new challenge today is the capability to invert such gravity data on large areas with the aim to obtain a 3D density model of the Earth crust. This is in fact a problem characterized by intrinsic instability and non-uniqueness of the solution that to be solved requires the definition of strong constrains and numerical regularization.

In this work the authors propose the application of a Bayesian inversion algorithm to the Antarctica continent to infer a model of mass density distribution. The first operation is the definition of an initial geological model in terms of geological horizons and density. These two variables are considered as random variables and, within the iterative procedure based on Markov Chain Monte Carlo methods, they are adjusted in such a way to fit the gravity field on the surface. The test performed show that the method is capable of retrieving an estimated model consistent with the prior information and fitting the gravity observations according to their accuracy.
Modeling summer heat load in Zagreb due to climate change effect
Authors: Nimac Irena , Herceg Bulić Ivana , Žuvela-Aloise Maja
Published: March 2020

Changes in surface and atmosphere characteristics in urban areas can alter radiation, heat and water balance and generate excessive heat load in those areas. One of the associated consequences is higher temperatures in built-up areas compared to the rural surrounding, also known as urban heat island (UHI). Here, summer heat load in Zagreb, the largest city of Croatia, is investigated. Summer season is in the focus of the study, not only because it is shown that trend in summer temperatures in Zagreb is stronger compared to the winter one, but also as it is the season when intense and prolonged extreme weather events, like heat-weaves, are likely to occur.

In this work, urban climate model MUKLIMO_3 with 100 m horizontal resolution is applied for a broader area of Zagreb. To explore the effect of climate change on the heat load, two separate experiments with the same land-use (corresponding to the current state of the city), but for different climate conditions are made. Daily data measurements for the period 1951–1980 are used as past climate, while 1981–2010 period represents the current climate conditions. Heat load is here estimated by a number of days with the maximum air temperature above 25 °C, i.e. by summer days. Both simulations indicated the lowest values of heat load in mountainous forest area accompanied by increased values in densely built-up regions and old city center. However, lower number of summer days is also found for green and blue areas within the city. The spatial pattern of difference in the number of summer days between considered periods is mainly influenced by orography with a much lower increase in the mountain area of the domain than in the lowland city region.
Extreme summer heat and drought acts as an environmental veto for fruit production in European beech
Authors: Nussbaumer Anita , Meusburger Katrin , Schmitt Maria , Waldner Peter , Gehrig Regula , Haeni Matthias , Rigling Andreas , Brunner Ivano , Thimonier Anne
Published: March 2020

European beech is known to be a masting species, i.e. fruit production does not occur every year. It is thought to be a species which is flowering controlled, i.e. that after successful pollination, fruits and seeds would be produced. In the last two decades, years with high fruit production occurred every two to three years in Middle Europe, which may be indication for an inherent biennial cycle. However, successful fruit production can be hampered by disadvantageous weather conditions, such as frost events, during the pollination season.

In Switzerland, after high beech pollen concentration was measured in spring of 2018, high fruit production was expected. However, during the extremely hot and dry European summer of 2018, beech produced no, or only small amounts of beechnuts in two of three long-term monitoring beech stands in Switzerland, which are part of the Swiss Long-Term Forest Ecosystem Research Programme. We observed that beechnuts were aborted in early summer already. Over the last decades, we found similar examples of mast failure and fruit abortion in years with hot and dry summer conditions. These extreme conditions can thus act as an “environmental veto”, similar to frost events during flowering. In years with fruit abortion, summer mean temperatures were 1.2°C higher, and precipitation sums were 45% lower than the long-term average. Our findings are evidence for a biennial masting cycle in European beech, which can be interrupted by extreme weather conditions such as extreme summer heat and drought or frost during flowering.
First Record of Conodonts from the Permo-Triassic Khartam Member, Khuff Formation in Central Saudi Arabia
Authors: Babiker Jarrah , Humphrey John , Al-Ramadan Khalid , Kaminski Michael
Published: March 2020

The Permo-Triassic boundary has been proposed to lie between the upper and lower Khartam Members of the Khuff Formation in central Saudi Arabia. Earlier studies relied on sequence stratigraphy and geochemistry as tools for identifying the Permo- Triassic boundary. This resulted in placing the boundary in different stratigraphic positions. Worldwide, conodonts are known to be the best indicators for defining the Permo-Triassic boundary biostratigraphically. In this study, we discovered two lithological units containing conodonts in different stratigraphic positions in the Khartam Member. Conodonts in the lower stratigraphic unit were recovered from calcareous silty mudstone, while conodont samples from the upper stratigraphic unit were recovered from calcareous siltstone. Thin section petrography initially revealed the conodonts, while XRF, XRD, SEM, and QEMSCAN techniques were used to confirm the presence of biogenic apatite. Conodonts collected from the two stratigraphic intervals of the Khartam Formation showed distinct and different morphological features. Conodonts of the lower unit mainly belong to the Neogondolellids group, while conodonts from the upper unit belong to the Anchignathodontids group. This new discovery represents the first step for a clear definition of the Permo-Triassic boundary in the Arabian Peninsula.  
The transient sensitivity of sea level rise
Authors: Grinsted Aslak , Christensen Jens Hesselbjerg
Published: March 2020

We are warming our planet, and sea levels are rising as oceans expand and ice on land melts. This instigates a threat to coastal communities and ecosystems, and there is an urgent need for sea level predictions encompassing all known uncertainties to plan for it. Comprehensive assessments have concluded that sea level is unlikely to rise by more than about 1.1m this century but with further increase beyond 2100. However, some studies conclude that considerably greater sea level rise could be realised and an expert elicitation assign a substantially higher likelihood to this scenario. Here, we show that models used to assess future sea level in AR5 & SROCC have a lower sea level sensitivity than inferred from observations. By analyzing mean rate of change in sea level (not sea level itself), we identify a near linear relationship with global mean surface temperature in both model projections, and in observations. The model projections fall below expectations from the more recent observational period. This comparison suggests that the likely range of sea level projections in IPCC AR5 and SROCC would be too low.
Reconstruction of the magnetic connection from Mercury to the solar corona
Authors: Ippolito Alessandro , Plainaki Christina , Zimbardo Gaetano , Massetti Stefano , Milillo Anna
Published: March 2020

The magnetic foot point of Mercury on the solar disk has been reconstructed for selected case studies, in order to better understand the interaction between the solar corona and the planet. The transport of the magnetic field lines in the heliosphere is here evaluated with a Monte Carlo code that gives a random displacement at each step of the integration along the Parker magnetic field model. Such displacement is proportional to a “local” diffusion coefficient, which is a function of the fluctuation level and magnetic field correlation lengths. The simulation is tailored to specific events by using the observed values of solar wind velocity and magnetic fluctuation levels. Magnetic data from MAG/MESSENGER have been considered to compute the magnetic fluctuation level, while, concerning proton fluxes, FIPS/MESSENGER data has been taken into account. A number of SEP events observed on Mercury during 2011 and 2012 have been analysed, studying, for each event, the magnetic connection from Mercury to the solar corona, and the position of the active region possibly source of the accelerated particles observed.
Does vegetation greening partly offset increasing rainfall pressure? Risk assessment of the water erosion tendency in China over the past 20 years.
Authors: Wang Han , Zhao Wenwu , Liu Yanxu
Published: March 2020

Soil water erosion is a severe environmental issue which seriously damaging the sustainability of agriculture. Regional climate change could aggravate the threat of erosion, whereas vegetation greening in China (an increasing trend in vegetation cover) could act as a mitigation to the threat. On the basis of the Revised Universal Soil Loss Equation, we proposed a framework for performing an assessment of water erosion risk in China during 1998-2018. A contribution index was constructed to describe the influences of rainfall erosivity and cover management on water erosion risk changes in China during 1998-2018. The research objective was to explore the spatial pattern of water erosion risk change in China in recent decades and to identify the factor that has the largest contribution to the risk change. Results showed that: (a) The area with decreasing water erosion risk in China accounted for 34.97%, and the area with significant decreasing trends accounted for 20.04% of the middle and highly risky state areas. (b) The region that rainfall erosivity contributed more than cover management for absolute value accounted for 76.54%, whereas the contribution of cover management was increasing. (c) Vegetation greening can partly offset the stress caused by climate change. Water erosion risk in China decreased more than increased in risky state area. The pixels with cover management contribute more than rainfall erosivity was concentrated within the area where risk is decreasing, indicating a great contribution of vegetation greening to the risk mitigation. Consequently, enhancing the vegetation growth in the highly risky state water erosion region could reduce the erosion threat in China.