bluuebunny/crossref_metadata_2025 huggingface dataset:
Seismic waveform modelling and inversion with velocity-deviatoric stress-isotropic pressure formulation
Authors: Zhang Yi , de Siena Luca , Stovas Alexey
Published: March 2021

In waveform inversion, most of the existing adjoint-state methods are based on the second-order elastic wave equations subject to displacement. The implementation of the acoustic-elastic coupling problem and free-surface in this formulation is not explicit, especially for arbitrary boundaries. The formulation of velocity-deviatoric stress-isotropic pressure can tackle the above issue. We firstly review the difference between velocity stress equations and velocity-deviatoric stress-isotropic pressure equations. Then the adjoint state of the velocity-stress equations are derived, decomposing stresses into their deviatoric and isotropic parts. To simulate the unbounded wavefield, perfectly matched layers (PML) are embedded into the system of equations. It is modified for cheap computation, which avoids PML-related memory variables by applying complex coordinate stretch to three Cartesian axes in parallel.

A 3D velocity-deviatoric stress-isotropic stress formulation is implemented with the staggered finite-difference method for several synthetic models (including anisotropic models). And inversions are then performed to reconstruct the model parameters, which is followed by a sensitivity analysis.

This method has the potential to be used with real data, both for active and passive seismics. However, in its current form, since it does not treat fluid/anisotropic solid interfaces correctly, it is limited to fluid or isotropic solid problems.
Fungi as Ecosystem Engineers in the Soil Pore Space
Authors: Hammer Edith , Mafla Endara Micaela P. , Arellano Caicedo Carlos G. , Pucetaite Milda , Aleklett Kadish Kristin , Ohlsson Pelle
Published: March 2021

Soils are characterized by their largely varying microhabitats that determine their microbial communities and functions such as nutrient cycling. Microbes, and especially fungi, do not only react to those microhabitats but also contribute to shaping them.

We used transparent, microstructured chips simulating the internal pore space of soils, to microscopically study fungal mycelia at the hyphal scale. We investigated the variety of fungal morphologies in maze structures, and hyphal interactions with their biotic and abiotic microenvironments. We studied both a variety of laboratory strains including an arbuscular mycorrhizal fungus and natural soil inocula, and we quantified their growth strategies in different microstructures and their interactions with bacteria, protists and soil mineral particles.

We could observe how the rigid hyphae of fungi opened up passages through chip- or soil solids and aggregates, increasing the spatial availability of the pore space. They, on the other hand, also filled up pores and pore necks with their biomass, creatingbarriers for both organisms, flow of water and sedimentation of matter, and thus changing the pore size distribution and -connectivity. Hyphae also increased the wettability of pores, which led to a higher connectivity of water films across air pockets and thus benefiting the dispersal of water-dwelling microorganisms, a phenomenon earlier termed “fungal highways”. We found the abundance of both bacteria and protists strongly increased in pore spaces containing hyphae in comparison to those without, dispersal events via fungal hyphae that happened frequently and were quantifiable in the high internal replication of our chip’s pore space channels. This allowed us to conclude on a high relevance of this mode of dispersal in soils with intermediate moisture. Fungal hyphae had thus a strong and obvious effect on their surrounding microenvironments and organisms.

We consider the study of microbial behaviour and interactions at the cellular scale in microhabitats to be essential for a better understanding of soil functions, and to gain mechanistic insight into phenomena observable at macroscale.

 
Rapid intensity variations during the second half of the first millennium BCE in Central Asia and global implications.
Authors: Bonilla-Alba Raquel , Gómez-Paccard Miriam , Pavón-Carrasco Francisco Javier , Beamud Elisabet , Martínez-Ferreras Verónica , Gurt-Esparraguera Josep Maria , Ariño-Gil Enrique , del Rio Judit , Palencia-Ortas Alicia , Martín-Hernández Fátima , Chauvin Annick , Osete María Luisa
Published: March 2021

Recent archeomagnetic studies performed in different regions of the world have revealed unusual periods of sharp changes in intensity during the first millennium. Here we focus on the study of intensity variations between 600 BCE and 600 CE in central Asia, where an important intensity decrease seems to be present during the second half of the 1st millennium BCE. For this purpose, we present a new paleosecular variation (PSV) curve obtained from 51 new archeointensities and the selected previous data located within a radius of 1000 km around Termez (Uzbekistan). The new curve shows an intensity maximum around 400 BCE followed by a rapid decrease. When the virtual axial dipole moment (VADM) values are compared with the Dipole Moment estimations derived from different global geomagnetic models key differences are observed, suggesting an important non-dipolar effect for this feature. Finally, in order to constrain the spatial behaviour of this phenomenon and its global implications, we investigate the PSV intensity and VADM trends from twelve regions distributed among Central America, Europe and Asia. A VADM maximum is observed in Western Europe (Iberia and Germany) around 450 BCE, associated to rates of change of about 9 µT/century. This feature is also observed eastwards, in the Caucasus and the Levant, but associated to lower rates of changes. In Central Asia (Uzbekistan) our new study suggests that maximum values of about 14 µT/century, between 400-300 BCE, were achieved. In other regions, as Eastern Asia and Central America, rapid variations of the intensity are not observed during the targeted period.

 
Event synchrony based complex network analysis of heavy precipitation in different monsoon regions revealing dynamical patterns of extreme event formation and propagation
Authors: Donner Reik , Wolf Frederik
Published: March 2021

Investigating the synchrony and interdependency of heavy rainfall occurrences across and between different tropical regions offers a new perspective on the underlying physical mechanisms. In this context, studies utilizing functional network representations have recently contributed to significant advances in the understanding and prediction of extreme weather events. Here, we systematically contrast previous results on spatiotemporal extreme precipitation patterns in three key monsoon regions (India, South America and East Asia) based on the concept of event synchronization (ES) with corresponding patterns obtained using the closely related event coincidence analysis (ECA) approach. Our findings demonstrate that an additional window size parameter of ECA not involved in ES allows for a more detailed analysis of the formation and propagation processes associated with heavy precipitation events. While the resulting network connectivity patterns based on both approaches closely resemble each other for the case of the South American monsoon system and the Indian summer monsoon, there exist subtle differences that carry climatologically relevant information. We further exploit the advanced potentials provided by ECA for studying in greater detail the spatial organization of East Asian summer monsoon (EASM) related heavy precipitation across the relevant season in a time-dependent fashion. Our results show that the formation of the Baiu front as a main feature of the EASM is accompanied by a double-band of synchronous heavy rainfall with two spatially dislocated centers north and south of the front. Although these bands are closely related to low- and high-level winds which are commonly assumed to be independent of each other, it is rather their mutual interconnectivity that changes during the different phases of the EASM season in a characteristic way. The thus obtained insights could provide relevant information for improving existing forecasting strategies for monsoon onset and strength.

 

References:

Odenweller, R.V. Donner: Disentangling synchrony from serial dependency in paired-event time series. Physical Review E, 101(5), 052213 (2020)

Wolf, J. Bauer, N. Boers, R.V. Donner: Event synchrony measures for functional climate network analysis: A case study on South American rainfall dynamics. Chaos, 30(3), 033102 (2020)

Wolf, U. Öztürk, K. Cheung, R.V. Donner: Spatiotemporal patterns of synchronous heavy rainfall events in East Asia during the Baiu season. Earth System Dynamics Discussions. doi:10.5194/esd-2020-69 (2020)

Wolf, R.V. Donner: Spatial organization of connectivity in functional climate networks describing event synchrony of heavy precipitation. European Physical Journal Special Topics (in review)
Trade-offs between hydrolytic and oxidative extracellular enzyme activity under climate change: Implications for soil carbon cycle
Authors: Chen Ji
Published: March 2021

Soil extracellular enzymes (EEs) catalyze rate-limiting steps in soil carbon (C) decomposition, which may have important implications for soil C cycling. Hydrolytic and oxidative EEs are targeting the decomposition of different soil C pools with distinct microbial C use efficiency. Here, we analyzed the responses of hydrolytic and oxidative EEAs to experimental warming, enhanced N deposition and altered precipitation. Experimental warming profoundly increased oxidative EEAs by 21%, while having no effect on hydrolytic EEAs. Enhanced N addition significantly decreased oxidative EEAs by 21% but enhanced hydrolytic EEAs by 15%. Increased precipitation substantially stimulated oxidative EEAs by 21%, while having no effect on hydrolytic EEAs. On the contrary, decreased precipitation significantly suppressed oxidative EEAs by 11% but enhanced hydrolytic EEAs by 26%. Those results together showed that hydrolytic and oxidative EEAs generally responded asymmetrically to the experimental treatments, representing the trade-offs between microbial hydrolytic and oxidative EEs production. Moreover, experimental treatments were more likely to have positive effects on soil C stock when oxidative EEAs respond negatively, and vice versa. One explanation might be that degradation of soil C pools that targeted by oxidative EEs were typical with lower microbial C use efficiency, since additional energy was required for the deconstruction of those complex and recalcitrant soil C pools. Altogether, our results highlight that soil EEAs can potentially be harnessed towards soil C sequestration if we can better understand the underlying mechanisms associated with the trade-offs between hydrolytic and oxidative EEAs.
Seasonal variability of natural methane seepage offshore Western Svalbard
Authors: Moser Manuel , Dølven Knut Ola , Ferré Bénédicte
Published: March 2021

Natural methane seepage from the seafloor to the water column occurs worldwide in marine environments, from continental shelves to deep-sea basins. Depending on water depth, methane fluxes, and mixing rate of the seawater, methane may partially reach the atmosphere, where it could contribute to the global greenhouse effect. Estimates of annual marine methane fluxes are commonly calculated from hydro-acoustic data collected during single research surveys. These snapshot estimates neglect short (i.e., tide) and long (seasonal) variations.

Here we compare the seepage activity along the upper limit of the gas hydrate stability zone offshore Western Svalbard in August 2017 (bottom water temperature (BT) ~3.46°C), June 2020 (BT ~1.75°C), and November 2020 (BT ~3.96°C) using high-resolution vessel-based multibeam data. Our results complete annual methane flux estimates by Ferré et al. (2020) and confirm a significantly reduced seepage activity during the cold bottom-water conditions. We investigate short-term variation by comparing a 7.5 km long multibeam section at three phases of the lunar semidiurnal (M2) tide. We will discuss how these processes affect annual methane fluxes estimates offshore Svalbard and further Arctic methane fluxes estimates.

The research is part of the Centre for Arctic Gas Hydrate, Environment and Climate (CAGE) and is supported by the Research Council of Norway through its Centres of Excellence funding scheme grant No. 223259 and UiT.

 

Ferré, B., Jansson, P. G., Moser, M., Serov, P., Portnov, A., Graves, C. A., et al. (2020). Reduced methane seepage from Arctic sediments during cold bottom-water conditions. Nat. Geosci. 13, 144–148. DOI: 10.1038/s41561-019-0515-3
Pyrogenic carbon and forest dynamics during drought in Amazonian forests
Authors: Vedovato Laura , Carvalho Lidiany , Aragão Luiz , Feldpausch Ted
Published: March 2021

During extreme drought events, aboveground biomass (AGB) dynamics in Amazonian forests are altered through reduced productivity and increased tree mortality and carbon loss. Tree adaptations developed in response to historical drought may reduce the severity of carbon loss. Past droughts were likely associated with fire, which produced Pyrogenic Carbon (PyC), a form of carbon formed by the incomplete combustion of biomass burn and fossil fuel. PyC has specific properties that improve soil fertility and water holding capacity and decrease aluminium toxicity, among others. PyC can be found in different concentrations across the Amazon Basin, since it can be produced by local fires and aerosol deposition. It is unknown whether PyC could explain tree adaptations or contributes to Amazon forest dynamics, especially for extreme drought events. We hypothesize that PyC in soil can serve as a proxy of fire history and fire/drought adaptations and also support the forest during drought events because of its properties, decreasing mortality rates and maintaining rates of AGB gain equivalent to a non-extreme drought year. To evaluate this hypothesis, we used a dataset with more than 70 plots with repeat censuses distributed across the Amazon Basin and classified extreme drought events using maximum cumulative water deficit (MCWD) analysis. Soil samples were collected from the same plots during an intensive fieldwork campaign and PyC was quantified by hydrogen pyrolysis (HyPy). Forest plots were classified into high and low PyC based on the median across the whole dataset. Our preliminary results show that during extreme drought events, plots that have a greater concentration of PyC had significantly higher rates of AGB gain when compared with plots with lower concentrations of PyC (t-test, p < 0.05). During non-extreme drought years there was no significant difference in rates of AGB gain between plots with different concentrations of PyC. When we focus on plots with lower concentrations of PyC there is a significant decrease in rates of AGB gain during drought years compared to non-extreme drought years (t-test, p < 0.05). However, in plots with high concentrations of PyC there is no significant difference in rates of AGB gain, showing trees are able to maintain normal forest dynamics during extreme drought years. We conclude that PyC has an important role in mediating drought resistance and productivity in Amazonian forests.
Investigation of volcanic emissions in Antikythera PANGEA station using near-real-time alerts
Authors: Kampouri Anna , Amiridis Vassilis , Solomos Stavros , Gialitaki Anna , Marinou Eleni , Spyrou Christos , Georgoulias Aristeidis K. , Akritidis Dimitris , Papagiannopoulos Nikolaos , Mona Lucia , Scollo Simona , Pytharoulis Ioannis , Karacostas Theodore , Zanis Prodromos
Published: March 2021

In the last years, several Etna eruption events are documented, forming lava flows and explosive activity. The Pilot EO4D_ash – Earth observation data for detection, discrimination & distribution (4D) of volcanic ash of the e-shape project provides the PANhellenic GEophysical observatory of Antikythera (PANGEA) of the National Observatory of Athens (NOA), in Greece with near-real-time alerts from Etna volcano eruptions. These alerts are used in the PANGEA station to monitor and reveal the presence of volcanic particles above the area the days following an eruption, also the station is supported by a volcanic particle monitoring and forecasting warning system. In this work, we investigate the volcano eruption between 30 May and 6 June 2019 which affected the southern parts of Greece and reaching the Antikythera station. Due to the prevailing meteorological conditions, volcanic particles and gases followed an easterly direction and were dispersed towards Greece. FLEXPART dispersion model simulations confirm the volcanic plume transport from Etna towards PANGEA, mixing also with co-existing desert dust particles. Model simulations are evaluated with PollyXT lidar measurements performed at PANGEA and satellite-based SO2 observations from the TROPOspheric Monitoring Instrument onboard the Sentinel-5 Precursor (TROPOMI/S5P). This is the first time that Etna volcanic products are monitored at the Antikythera station, in Greece with implications for the investigation of their role in the Mediterranean weather and climate.

Acknowledgments: We acknowledge the support by EU H2020 E-shape project (Grant Agreement n. 820852). Also, this research was supported by data and services obtained from the PANhellenic Geophysical Observatory of Antikythera (PANGEA) of the National Observatory of Athens (NOA), Greece, and by the project “PANhellenic infrastructure for Atmospheric Composition and climatE change” (MIS 5021516) which is implemented under the Action “Reinforcement of the Research and Innovation Infrastructure”, funded by the Operational Programme "Competitiveness, Entrepreneurship and Innovation" (NSRF 2014-2020) and co-financed by Greece and the European Union (European Regional Development Fund). NOA team acknowledges the support of the Stavros Niarchos Foundation (SNF).
Amine Emissions from Agricultural Sources
Authors: Håland Alexander , Mikoviny Tomas , Syse Elisabeth Emilie , Oskam Irma Caroline , Wisthaler Armin
Published: March 2021

In recent years there has been growing scientific interest in agricultural emissions of volatile organic compounds (VOCs) and their potential effects on air quality and the biogeochemical cycling of carbon and nitrogen. Among the many VOCs emitted, amines are particularly challenging to measure with currently available instruments.

In light of these analytical challenges, the Atmospheric Chemistry Group at the Department of Chemistry of the University of Oslo has developed a novel analytical instrument for the detection of atmospheric amines. The instrument is a modified version of a commercial Proton-Transfer-Reaction Time-of-Flight Mass Spectrometer (PTR-ToF-MS). After modification, this instrument has proven able to detect atmospheric amines down to single-digit-ppt levels. This instrument also benefits from a very short response time, which makes it possible to monitor rapid dynamic changes of amine concentrations in the atmosphere.

The novel instrument was deployed at the Livestock Production Research Centre (SHF) of the Norwegian University of Life Sciences (NMBU) in Ås (Norway) for characterizing agricultural emissions of VOCs in general, and of amines in particular.

Data analysis has so far revealed a very complex VOC emission pattern. Methylamine, trimethylamine and skatole were among the atmospheric amines detected in the ambient air in proximity of the facility. In addition to the field measurements, we also carried out laboratory experiments for analyzing VOCs in the dynamic headspace of different source materials (manure, animal feed, straw litter, etc.).

We will present the new instrument and preliminary data collected from this measurement campaign.   
CrowdWater: How well can citizens observe water levels and other hydrological variables using a smartphone app?
Authors: Seibert Jan , Etter Simon , Strobl Barbara , Blanco Sara , Scheller Mirjam , Schwarzenbach Franziska , van Meerveld Ilja
Published: March 2021

Citizen science observations are potentially useful to complement existing monitoring networks. This is also the case in hydrology, where we often lack spatially distributed observations. Engaging the public might help to overcome the lack of data in hydrology. So far, most hydrological citizen science projects have been based on the use of different instruments or installations. For stream level observations, a staff gauge is installed in the river but it is difficult to scale this type of citizen science approach to a large number of sites because these gauges cannot be installed everywhere (or by everyone). Here, we present an evaluation of the CrowdWater smartphone app that allows the collection of hydrological data without any physical installation or specialized instruments. With the help of a free app, citizens can report the stream level, soil moisture conditions, the presence of water in temporary streams, plastic pollution in streams and on streambanks, as well as general information on streams. The approach is similar to geocaching, with the difference that instead of finding treasures, hydrological measurement sites are set up. These sites can be found by the initiator or other citizen scientists to take additional measurements at a later time. For the water level measurements, a virtual staff gauge approach is used instead of a physical staff gauge. A picture of a staff gauge is digitally inserted into a photo of a stream bank or a bridge pillar and serves as a reference of the water level. During a subsequent field visit, the stream level is compared to the virtual staff gauge on the first picture. In this presentation, we discuss how well the water level class observations agreed with measured stream levels, and in which months and during which flow conditions citizens submitted their stream level observations. We also highlight methods to ensure data quality, and illustrate how these water level data can be used in hydrological model calibration. We also give an update on new activities in the CrowdWater project.
Assessing the time-step dependency of calculating supraglacial debris thermal diffusivity from vertical temperature profiles
Authors: Beck Calvin , Nicholson Lindsey
Published: March 2021

Debris thermal conductivity is a critical parameter in calculating a glacier’s sub-debris ice melt. The method widely used in publications to calculate apparent thermal conductivity of supraglacial debris layers is based on an estimate of volumetric heat capacity of the debris and simple heat diffusion principles and is presented in . The analysis of heat diffusion requires a vertical array of temperature measurements through the supraglacial debris cover. This study explores the effect of the temperature sampling interval on the thermal conductivity values derived using this method. Initial results indicate that the thermal diffusivity decreases linearly with an increasing sampling time from 30min to 6h by 0.2-0.4 mm²/s for glaciers in high mountain Asia during the monsoon season. These results suggest that care must be taken in choosing the analysis time interval for computing debris thermal conductivity and for comparing values between datasets sampled at different intervals. Current research aims to further investigate the cause of the artifact and determine how this problem can be solved. An open-source web application is therefore developed to help other scientists investigate the effect of the sampling interval on their calculated sub-debris ice melt. This study falls under the remit of the on debris-covered glaciers and is supported by data provided from within this group.
A century of geomagnetic storms, CMEs and HSS/SIRs
Authors: Mursula Kalevi , Qvick Timo , Holappa Lauri
Published: March 2021

Geomagnetic storms are mainly driven by the two main solar wind transients: coronal mass ejections (CME) and high-speed solar wind streams with related (corotating) stream interaction regions (HSS/SIR). CMEs are produced by new magnetic flux emerging on solar surface as active regions, and their occurrence follows the occurrence of sunspots quite closely. HSSs are produced by coronal holes, whose occurrence at the ecliptic is maximized in the declining phase of the solar cycle.

Geomagnetic storms are defined and quantified by the Dst index that measures the intensity of the ring current and is available since 1957. We have corrected some early errors in the Dst index and extended its time interval from 1932 onwards using the same stations as the Dst index (CTO preceding HER). This extended storm index is called the Dxt index. We have also constructed Dxt3 and Dxt2 indices from three/two of the longest-operating Dst stations to extend the storm index back to 1903, covering more than a century of storms.

We divide the storms into four intensity categories (weak, moderate, intense and major), and use the classification of solar wind by Richardson et al. into CME, HSS/SIR and slow wind -related flows in order to study the drivers of storms of each intensity category since 1964. We also correct and use the list of sudden storm commencements (SSC) collected by Father P. Mayaud, and divide the storms of each category into SSC-related storms and non-SSC storms.

Studying geomagnetic storms of different intensity category and SSC relation allows us to study the occurrence of CMEs and HSS/SIR over the last century. We also use these results to derive new information on the centennial evolution of the structure of solar magnetic fields.
Determinants of geoheritage conservation: Multiple correspondence analysis to explore interrelations between socio-economic and bibliometric data
Authors: Németh Boglárka , Németh Károly
Published: March 2021

Geoheritage is an emerging research subject with increasing global interest to define, characterize and quantify it in diverse geological and geomorphological settings. As being a new research subject there are great variety of conceptual approaches to do its definition and quantification. Geoheritage conservation is in the process of establishing a common ground that become necessary in the transnational collaboration for a sustainable future. Geoheritage conservation generates ever increasing number of scientific publications based on heterogenous evaluation methods with limited consensus within the field. The produced material, also part of various Big Data repositories, conceals valuable patterns and information on the level of agreement and the solution to draw the line for the acceptable level of subjectivity. Analysing bibliometric data of scientific publication appear in accessible global data bases (e.g. Web of Science) broken down to country levels allow us to find potential indicators for geoheritage designation. Finding determinants that positively influences decision makers and end users within the conservation arena helps geoscientists to achieve policy impact and increase the number of recognised and protected geological and geomorphological sites. Multiple Correspondence Analysis was used to detect and explore relationships between population, land, tourism, protected areas and bibliometric variables. The result revealed very important links between the socio-economic background and geoheritage conservation outcomes. The fact that there was no one major determinant found that would affect geoheritage conservation globally means that a common ground awaits to be established on which countries can build upon with the unique and special values local communities have to contribute toward geoheritage conservation.

The research is aligned with the goals of the “Geoheritage for Resilience” UNESCO IGPC project 692 program.
Monitoring the Evolution of a Tidal Salt Marsh Restoration Site with an RTK-enabled UAV
Authors: Lewis Samantha , Baker Greg , Bowron Tony , Graham Jennie , van Proosdij Danika
Published: March 2021

Since 1900 AD, 64-71% of the world’s natural wetlands have been lost due to anthropogenic influences. Wetland restoration projects, such as managed realignment and tidal salt marsh restoration, act to combat these losses, but are also being used as a form of nature-based adaptation to the effects of climate change, including sea level rise. New advances in Unmanned Aerial Vehicle (UAV) technology offer a unique opportunity to quantify the restoring landscape at resolutions and accuracies previously unachievable. This presentation will focus on the use of hyperspatial datasets collected with a Real-Time Kinematic (RTK) GNSS enabled UAV at a managed realignment site in the Bay of Fundy, Canada, to monitor and quantify the geomorphic evolution of the site, including the development of a semi-automated method for mapping embryonic creek networks. Analyzed datasets were collected seasonally over the course of 1 year following the reintroduction of tidal flow, and range in resolution from 2.0 - 3.5 cm. Preliminary results show significant spatial variation in channel evolution patterns, related to the presence and absence of antecedent landscape features. A greater understanding of restoration site evolution, and the effects of the antecedent landscape on that evolution, will allow for a more informed design and implementation of future restoration projects to encourage site resilience and sustainability in terms of climate change adaptation.
Laboratory study on seismicity mitigation: The role of loading pattern and rate
Authors: Naderloo Milad , Barnhoorn Auke , Veltmeijer Aukje , Jansen Jan Dirk
Published: March 2021

Reactivation of pre-existing faults/fractures in the reservoir due to the deep injection is a key concern in designing and running geothermal and water/CO2 injection projects. Therefore, we investigate potential methods to manage injection-induced seismicity. Recent laboratory and field studies recommend that changes in injection pattern (e.g., cyclic injection) might trigger less seismicity than monotonic injection. This study presents results from uniaxial compressive laboratory experiments performed on high porosity Red Felser sandstone that provide new information about the effect of loading pattern and rate on injection‐driven seismicity. Red Felser sandstone samples with identical porosity and dimensions were subjected to three different loading patterns, including cyclic recursive (CR), cyclic progressive (CP), and monotonic loading. Besides, three different loading rates (displacement control) were applied for each loading pattern: low, medium, and high rates that are 10-4 mm/s, 5×10-4 mm/s, and 5×10-3 mm/s, respectively. Microseismicity analysis shows that (i) the maximum magnitude of seismic events and seismic radiated energy at failure decrease for lower loading rates and during the cyclic loading scenario, (ii) the b-value (magnitude-frequency distribution of events) increases on average 40% for a low-rate cyclic recursive loading in comparison with high-rate cyclic recursive and monotonic loading at different rates. The largest b-value resulted from a low-rate cyclic recursive (LCR) loading pattern. The b-value was estimated and compared using different methods, including a least-square regression on either an incremental frequency distribution or a cumulative frequency distribution, and with the maximum likelihood method (MLM) to provide a reliable b-value estimation. The analyses indicate that by considering the accurate magnitude of completeness, MLM, and, with a least-square regression, the incremental frequency distribution, both result in a reliable b-value. From a mechanical perspective, a low loading rate reduces the sample's final strength by 19%. Moreover, samples subjected to cyclic loading display more complex fracture patterns and more disintegration. In our laboratory study, a combination of low-rate loading and a recursive cyclic loading pattern resulted in reduced seismicity through decreasing the maximum seismicity magnitude and increasing the b-value.
The role of shallow open system processes in the evolution of South Tepeldag Pluton (NW Turkey): insights and constraints from thermodynamic modelling
Authors: Arık Tunahan , Kamacı Ömer , Güraslan Işıl Nur , Altunkaynak Şafak
Published: March 2021

Eocene granitoids in NW Anatolia occurred following the continental collision between Sakarya Continent and Tauride-Anatolide Platform and mark the onset of post-collisional magmatism in the region. One of the representative members of the Eocene granitoids, the Tepeldağ pluton crops out as two isolated granitic bodies and is intruded into the Cretaceous blueschist assemblages (Kocasu formation) and ophiolitic rocks within the Izmir-Ankara-Erzincan suture zone (IAESZ). South Tepeldağ pluton (STP) is composed mainly of granodiorite with subordinate quartz diorite, which show transitional contacts. Aplitic dykes crosscut the pluton as well as the country rocks. STP includes a number of mafic microgranular enclaves (MME) of gabbro/diorite composition.

Geochemically, STP shows distinct I-type affinity with a metaluminous to slightly peraluminous (ASI ≤1.02) nature. The samples are medium-K to high-K calc-alkaline in character. They exhibit depletion in HFSE (Ti, Hf, Zr, Nb and Ta) compared to large ion lithophile elements (Rb, Ba, Th, U, K) and presents negative Nb, P, Ti anomalies. STP displays slight negative Eu anomalies (Eu/Eu* = 0.7–1.2), enrichment in LREE and flat HREE patterns in chondrite-normalized spider diagrams. MELTS modeling (with initial parameters of 1–3 kbar pressure, 2–3% water and QFM-NNO oxygen fugacity buffers) indicate that compositional variations in STP samples can be interpreted as a result of open system processes (assimilation fractional crystallization) rather than a reflection of fractional crystallization in the upper crustal magma chamber. All thermodynamic simulations dictate a crustal assimilation, especially in the late stages of the magmatic process, with a MgO, Na2O and Al2O3-rich assimilant similar to the suture zone (IAESZ) rocks.
Mass balance study of the Znosko glacier, Antarctica, using remote sensing and in situ measurements
Authors: Bello Cinthya , Suarez Wilson , Brondi Fabian , Gonzales Gilbert
Published: March 2021

Glaciers are a key indicator of climate change. Since the second half of the 20th century several glaciers in Antarctica have retreated. In situ measurements of glacier mass balance in the Antarctic Peninsula and its surrounding islands are very scarce because this area is inaccessible due to rough terrain and inhospitable atmospheric conditions, but there is a necessity in study peripheral glaciers dynamics to know their future contribution to sea level rise. To fill this gap, remote sensing is an alternative tool to enable timely monitoring of dynamic glaciers and quantifying spatial-temporal changes. Here we combine remote sensing (satellite imaginary and aerial photos) and in situ measurements to calculate mass balance for the Znosko glacier (King George Island, Antarctic Peninsula) and compare the accuracy of this methods. Two field campaigns were carried out during the XXVI and XXVII Peruvian Antarctic Operation (austral summer 2018/19 and 2019/20). 19 stakes were fixed on the glacier surface, in situ mass balance data were collected from yearly stake measurements. Also, digital elevation models were generated through aerial photogrammetry and auxiliary data from the ICESat-2 mission were included into the analysis.  We find that mass balances estimated with these methods are consistent and confirm the mass loss (heterogeneous pattern between accumulation and ablation zone) and retreat of Znosko glacier. We illustrate how participatory mapping (interdisciplinary team) can complement initial remote sensing land cover classification and assist ground checks.
A parallel adaptive finite element solver for global electromagnetic induction modeling using hierarchal tetrahedral meshes 
Authors: Yao Hongbo , Ren Zhengyong , Tang Jingtian
Published: March 2021

We present an accurate and fast finite element solver for global electromagnetic induction forward modeling problems in spherical Earth. We solve for the electric field equation using the first-order Nedelec elements. The magnetic field is then obtained by computing the curl of the electric field. The computational domain composed of the air space and the conductive Earth is discretized by disjoint unstructured tetrahedral elements. To improve the accuracy with an optimal number of unknowns, we propose a simple two-step goal-oriented adaptive mesh refinement (AMR) strategy. In the first step, an h-type AMR procedure is used to obtain an optimal finite element mesh. The mesh refinement is accomplished by bisection to generate a set of hierarchal tetrahedral meshes. The AMR procedure is driven by a goal-oriented error estimator, which is based on face jumps of normal components of current density. In the second step, we adopt the high-order finite elements at the last iteration to update the accuracy of final numerical solutions. This simple two-step adaptive strategy takes advantage of both h-type AMR and high-order basis functions, and in the meanwhile, it is also computationally economical. To improve efficiency, the solver is parallelized with an MPI-based domain decomposition technique. The sophisticated auxiliary space preconditioned linear solver is adopted to efficiently solve the linear system of equations. This new solver is verified on both semi-analytic and realistic 3-D Earth models. It can be used as a core to derive the inversion of global electromagnetic induction data.

 
Landsat thermal infrared to detect sub-canopy riparian flooding
Authors: Storey Emanuel , Krajewski Witold , Nikolopoulos Efthymios
Published: March 2021

Satellite based flood detection can enhance understanding of risk to humans and infrastructures, geomorphic processes, and ecological effects.  Such application of optical satellite imagery has been mostly limited to the detection of water exposed to sky, as plant canopies tend to obstruct water visibility in short electromagnetic wavelengths.  This case study evaluates the utility in multi-temporal thermal infrared observations from Landsat 8 as a basis for detecting sub-canopy fluvial inundation resulting in ambient temperature change.

We selected three flood events of 2016 and 2019 along sections of the Mississippi, Cedar, and Wapsipinicon Rivers located in Iowa, Minnesota, and Wisconsin, United States.  Classification of sub-canopy water involved logical, threshold-exceedance criteria to capture thermal decline within channel-adjacent vegetated zones.  Open water extent in the floods was mapped based on short-wave infrared thresholds determined parametrically from baseline (non-flooded) observations.  Map accuracy was evaluated using higher-resolution (0.5–5.0 m) synchronic optical imagery.

Results demonstrate improved ability to detect sub-canopy inundation when thermal infrared change is incorporated: sub-canopy flood class accuracy was comparable to that of open water in previous studies.  The multi-temporal open-water mapping technique yielded high accuracy as compared to similar studies.  This research highlights the utility of Landsat thermal infrared data for monitoring riparian inundation and for validating other remotely sensed and simulated flood maps.
Dynamic process and failure mechanism of rammed building structure subject to debris flow
Authors: Zou Qiang , Li Cong , Zhou Bin , Hu Zhenru , Jiang Hu
Published: March 2021

The failure mechanism of building structure is important for quantitatively assessing vulnerability of elements at risk, which is a critical step in risk assessment of debris flow. Scholars have recently made great processes in the researches on debris flow hazard effects and vulnerability of elements at risk. Statistical analysis methods have widely used to analyze field survey data and build vulnerability functions. Based on numerical simulation and model experiment, structural dynamic response process was analyzed to evaluate structure vulnerability. However, due to the lack of quantitative relationship between the debris flow hazard-forming mechanism and the dynamic response of building structure, it is essential to analyze the dynamic response characteristics and process of building structure subject to debris flow, which would play an important guiding role in disaster prevention and disaster mitigation.

Through hazard field investigation, the failure modes of rammed earth building caused by debris flow were summarized as burying, scouring and impact. Figure 1 shows the debris flow hazard in Jiende Gully, Liangshan. In addition, by using the finite element analysis method, the structure model of rammed earth building was established to simulate to the impact process of debris flow on the structure. During the dynamic failure process of rammed earth building shown in Figure 2, the failure types of building wall impacted by the debris flow mainly presented at crushed failure of the impact point, tensile failure of the inside wall and shear failure of the corner. Then debris flow destroyed the gable wall, rushed into the room, and broke the doorway, which resulted in damage of the longitudinal wall. Moreover, the response characteristics and failure mechanism of rammed earth buildings under the impact of debris flow further show that the integrity of rammed earth building is poor and the development of cracks cuts off the propagation path of stress, which effectively protects other walls. The transform-shape locations of the rammed earth building including were initially destroyed at the points of the wall foundation, corners of wall and the points impacted by big rocks of debris flow. Therefore, the reinforced measures on the locations where stress suddenly changes, such as wall foundations and wall corners should be paid more attention to protect rammed structure of buildings.
A 3-D Model of Surface Water and Groundwater Interaction in the Central Passaic River Basin, New Jersey.
Authors: Ophori Duke
Published: March 2021

A 3-D Model of Surface Water and Groundwater Interaction in the Central Passaic River

Basin, New Jersey.

 

Duke U. Ophori

Department of Earth and Environmental Studies

Montclair State University

Upper Montclair

New Jersey 0743

Ph: (973) 464 6238, Email: Ophorid@montclair.edu

 

Abstract

 

Hydrogeologists have believed, over the years, that the development of a groundwater basin results in increase in the basin’s groundwater recharge and decrease in discharge. This basin’s response to development is intricately tied with the natural recharge-discharge behavior of regional groundwater flow systems. A 3-D regional groundwater flow model is developed for the Central Passaic River Basin, New Jersey to evaluate its surface water-groundwater interactions. The models show that groundwater pumping increases recharge and decreases discharge in the basin. Groundwater-fed wetlands are reduced in size by groundwater pumping. These findings will enhance groundwater management in the basin.
Assessing the Turbulence Kinetic Energy Budget in the Boundary Layer Using WRF-LES: Impact of Momentum Perturbation
Authors: Kumar Mukesh , Banerjee Tirtha , Jonko Alex , Mirocha Jeff , Lassman William
Published: March 2021

Mesoscale-to-Large Eddy Simulation (LES) grid nesting is an important tool for many atmospheric model applications, ranging from wind energy to wildfire spread studies. Different techniques are used in such applications to accelerate the development of turbulence in the LES domain. Here, we explore the impact of a simple and computationally efficient Stochastic Cell Perturbation method (SCPM) to accelerate the generation of turbulence in the Weather Research and Forecasting (WRF) LES model on the Turbulence Kinetic Energy (TKE) budget. In a convective boundary layer, we study the variation of TKE budget terms under the initial conditions of the Scaled Wind Farm Technology (SWiFT) facility located in West Texas. In this study, WRF LES is used with a horizontal grid resolution of 12 m, and is one-way nested within an idealized mesoscale domain. It is crucial to understand how forced perturbation shifts the balance between the terms of the TKE budget. Here, we quantify the shear production, and buoyant production in an unstable case. Since additional production terms are introduced in the SCPM method, we investigate the dissipation term of TKE. In addition, we also study the generation of turbulent transport. Generally, it integrates over height to null in a planar homogeneous case without subsidence, indicating it is positive over some heights and negative over other heights. Furthermore, we also study the variation of the TKE transport term after extending the random perturbation up to a certain height. The findings of this study will provide a better understanding of the contribution of different budget terms in a forced LES simulation.
Mini ozone holes due to dust release of iodine 
Authors: Volkamer Rainer , Koenig Theodore , Apel Eric , Bresch James , Cuevas Carlos , Dix Barbara , Eloranta Edward , Fernandez Rafael , Hall Samuel , Hornbrook Rebecca , Pierce Bradley , Reeves Michael , Saiz-Lopez Alfonso , Spuhler Scott , Ullman Kirk
Published: March 2021

Desert dust as a source of iron and other micronutrients is recognized to fertilize oceans, but little attention has been paid to dust as a source of iodine. Empirical observations find iodate on dust measured during ship cruises downwind of the Sahara desert. However, it remains unclear whether iodine in dust is the result of marine iodine uptake on dust during transport in the marine boundary layer, or whether such iodine accumulates over geological time scales, and is emitted together with dust. Significant enhancements of iodine have been observed in Sahara dust events in form of methyl iodide (CH3I) and iodine monoxide (IO) radicals, but atmospheric models currently do not consider dust as a source of iodine. Furthermore, dust plumes are often accompanied by significant ozone loss, which is commonly attributed to reactive uptake of O3 and other odd oxygen species (i.e., N2O5, HNO3) on dust surfaces. However, laboratory experiments struggle to reproduce the large reactive uptake coefficients needed to explain field observations, and do not consider iodine chemistry. We present evidence that dust induced "mini ozone holes" in the remote (Southern Hemisphere) lower free troposphere west of South America (TORERO field campaign) are largely the result of gas-phase iodine chemistry in otherwise unpolluted (low NOx) dust layers that originate from the Atacama and Sechura Deserts. Ozone concentrations inside these elevated dust layers are often 10-20 ppb, and as low as 3 ppb, and influence entrainment of low ozone air from aloft into the marine boundary layer. Ozone depletion is found to be widespread, extending up to 6km altitude, and thousands of kilometers along the coast. Elevated IO radical concentrations inside decoupled dust layers are higher than in the marine boundary layer, and serve as a source of iodine, and vigorous ozone sink following entrainment to the marine boundary layer. The implications for our perception of iodine sources, surface air quality, oxidative capacity, and climate are briefly discussed.