bluuebunny/crossref_metadata_2025 huggingface dataset:
Study on Stratospheric Carbonyl Sulfide Transport and Chemistry using ‘Age of Air’
Authors: Qiu Chenxi , Ploeger Felix , Grooß Jens-Uwe , von Hobe Marc
Published: March 2021

Carbonyl sulfide (OCS or COS) is the longest lived and the most abundant reduced sulfur gas in the atmosphere. As chemical loss of OCS in the troposphere is slow, it can reach the stratosphere, where it is  photochemically oxidized and converted to stratospheric sulfate aerosol, being the largest source thereof in times of volcanic quiescence. Chemistry transport models show that OCS conversion occurs mainly in the ‘tropical pipe’ region, while along the lower branch of Brewer-Dobson circulation (BDC), OCS is passively transported without significant chemical loss. The OCS depleted air is transported along the upper branch of BDC and descends again at high latitudes. Using the distinct characteristics of  ‘age of air’ in the upper and lower branches of the BDC, this picture of OCS transport and especially the role of the ‘tropical pipe’ as the main region of OCS conversion can be supported by looking at the relationship between age spectra and OCS mixing ratios.

In this study, we will investigate the relation of OCS mixing ratios and mean age of air as well as mass fractions of air with different transit times using satellite-based measurements from MIPAS (Michelson Interferometer for Passive Atmospheric Sounding) and ACE-FTS (Atmospheric Chemistry Experiment - infrared Fourier Transform Spectrometer), and age spectra of air from CLaMS (Chemical Lagrangian Model of the Stratosphere).

In addition to satellite data analysis, we will investigate the distribution of OCS in the UTLS (upper troposphere and lower stratosphere) region and its relation to the age spectra using high-resolution in-situ observations of OCS. This unique dataset was obtained during the SOUTHTRAC mission in autumn 2019 by AMICA (Airborne Mid-Infrared Cavity enhanced Absorption spectrometer) on board the HALO (High Altitude Long Range) research aircraft. Flights from the main  campaign base in Río Grande, Argentina (53.8S, 67.7W) covered a wide latitude range from 48° N to 70° S, even reaching the southern polar vortex where aged air masses having descended from high altitudes are typically found.

Our analysis of both satellite and in-situ data generally supports the established picture of OCS conversion in the ‘tropical pipe’.
ForBioFunCtioN: Forest soil carbon and the effects of climate change and forest management
Authors: Johannesson Carl-Fredrik , Larsen Klaus Steenberg , Malicki Brunon , Nordén Jenni
Published: March 2021

Boreal forests are among the most carbon (C) rich forest types in the world and store up to 80% of its total C in the soil. Forest soil C development under climate change has received increased scientific attention yet large uncertainties remain, not least in terms of magnitude and direction of soil C responses. As with climate change, large uncertainties remain in terms of the effects of forest management on soil C sequestration and storage. Nonetheless, it is clear that forest management measures can have far reaching effects on ecosystem functioning and soil conditions. For example, clear cutting is a widely undertaken felling method in Scandinavia which profoundly affects the forest ecosystem and its functioning, including the soil. Nitrogen (N) fertilization is another common practice in Scandinavia which, despite uncertainties regarding effects on soil C dynamics, is being promoted as a climate change mitigation tool. A more novel practice of biochar addition to soils has been shown to have positive effects on soil conditions, including soil C storage, but studies on biochar in the context of forests are few.

In the face of climate change, the ForBioFunCtioN project is dedicated to investigating the response of boreal forest soil CO2 and CH4 fluxes to experimentally increased temperatures and increased precipitation – climatic changes in line with projections over Norway – within a forest management context. The experiment is set in a Norwegian spruce-dominated bilberry chronosequence, including a clear-cut site, a middle-aged thinned stand, a mature stand and an old unmanaged stand. Warming, simulated increased precipitation, N fertilizer and biochar additions will be applied on experimental plots in an additive manner that allows for disentangling the effects of individual parameters from interaction effects. Flux measurements will be undertaken at high temporal resolution using the state-of-the-art LI-7810 Trace Gas Analyzer (©LI-COR Biosciences). The presentation will show the experimental setup and first measurements from the large-scale experiment.
Employing Legacy Road Salt and Soil Electrical Conductivity as Tracers to Unlock Glyphosate Transport Processes in a Variable Source Area
Authors: Payne Emma , Pacenka Steven , Richards Brian , Brindt Naaran , Schatz Anna , Steenhuis Tammo
Published: March 2021

Glyphosate is the most widely used herbicide active ingredient in the world, with 1.35 Tg used globally in 2017. Despite a strong affinity for binding to soil and rapid microbial degradation, in recent studies glyphosate has been detected in agricultural runoff at significant concentrations. This unexplained phenomenon necessitates further study into the mechanism of glyphosate transport from agricultural fields. This study was an investigation into the internal hydrology at a 4.9 ha agricultural catchment and the hydrological processes driving glyphosate transport at this site. Chloride is introduced to this standalone watershed via a point source of sodium chloride road de-icer salt at the top edge of the catchment. The goal of this project was to employ chloride as a tracer to unlock how water moves in the catchment. Since 2015, we have been undertaking annual extensive field sampling campaigns to monitor runoff for glyphosate at an outlet weir. In this project, we used archived samples from the 2018, 2019 and 2020 field campaigns and analyzed over 700 samples for electrical conductivity, over 400 samples for chloride and over 500 samples for glyphosate. During storms, chloride concentration and electrical conductivity decreased as the baseflow component carrying dissolved ions was diluted by the fast response overland flow. During the peak flow of a storm, chloride makes up a consistent fraction of electrical conductivity as the entire catchment contributes to flow at the outlet. We also found that the ratio of glyphosate concentration to electrical conductivity increased linearly with flow rate. The rate of increase (ie., the slope of glyphosate to conductivity ratio versus flow rate) decreases between sequential storms as glyphosate adsorbs and microbially degrades, and from this we extrapolated an empirical degradation half-life of less than 10 days. Cumulatively, the observations of chloride and electrical conductivity suggest that the catchment behaves as a series of connected reservoirs, each with a slow-moving subsurface component and a fast-response overland component. By exploiting the existence of a road salt chloride tracer and soil electrical conductivity in a variable source area, we were able to unlock the hydrological processes at play in areas where surface runoff is generated.
Fractures in Granite: Results from United Downs Deep Geothermal well UD-1
Authors: Fellgett Mark W. , Haslam Richard
Published: March 2021

The geothermal potential of the granites of SW England has long been known. The first significant exploration of the resource was in the Carnmenellis Granite under the ‘Hot Dry Rock (HDR) Project’ during the 80’s and early 90’s. Following completion of the HDR project there was little further exploration in the area for geothermal power generation. Recently however, development of the United Downs Deep Geothermal Power (UDDGP) project marks a significant leap forward, and this aims to be the first commercial project to explore deep geothermal power generation in SW England.

 

The UDDGP project targets the Porthtowan Fault zone, a regional scale NW to NNW striking strike-slip fault that is inferred to transect the NE margin of the Carnmenellis Granite. Two directional wells were drilled to intersect this fault zone, maximising the surface area of the fault exposed. A production well with a measured depth of 5275 m true vertical depth of 5054 m and an injection well vertically above the production well at a measured depth of 2393 m and a true vertical depth of 2214 m. A full suite of geophysical wireline logs were collected for the production well, including borehole image logs from 900 mMD to 5160 mMD (900 - 4097mTVD).

 

Interpretation of the borehole imaging across the 4260 m identified a total of 12031 discontinuities. The features were classified using a simple schema and provide new insights into the complex nature of faulting and fracturing within the Granite. Stress field indicators including Borehole Breakouts and Drilling Induced Tensile Fractures (DIFs) were also interpreted.

 

The orientations of the borehole breakouts and DIFs are consistent and are comparable to previous measurements in the region and the regional stress field, indicating the direction of maximum compression is, approximately horizontal trending towards 320°.

 

The data show variable fracture density along the imaged section of the well with the maximum density tentatively associated with discreet fault zones. At least 3 fracture sets are identified with the largest concentration of fractures approximately parallel to inferred Porthtowan Fault Zone, suggesting UD-1 intersected the target fault zone. Key fracture attributes are explored and discussed including orientation, spacing, intensity, and spatial correlation.
Investigation of the reaction OH+CH2ClOOH of atmospheric interest
Authors: Srour Zainab , Taamalli Sonia , Fèvre-Nollet Valérie , Marécal Virginie , Cernusak Ivan , Louis Florent
Published: March 2021

Alkyl hydroperoxides are essential intermediates in the atmospheric oxidation of hydrocarbons and in low-temperature combustion processes [1]. Chlorinated alkyl hydroperoxides play a similar role in the atmospheric oxidation of chlorinated hydrocarbons. It is important to study the thermodynamic parameters for these species to understand and predict the reaction pathways, rate constants, and equilibrium constants. There are relatively few experimental studies on the thermodynamic properties of alkyl hydroperoxides due to their rapid interconversion and instability, which makes the studies of these species complex.

The main objective of this work is to provide reliable kinetic and thermodynamic data for the gas phase reaction of hydroxyl radicals with chloromethyl hydroperoxyl (CH2ClOOH). Several possible reaction pathways could be feasible: H-abstraction, Cl-abstraction, and OH-abstraction. The reaction mechanism involves many stationary points on the potential energy surface and reveals some unusual features for the H-abstraction. Theoretical calculations were performed with the augmented correlation consistent basis sets aug-cc-pVTZ for H and O atoms and the aug-cc-pV(T+d)Z for Cl atom including tight d polarization functions. The potential energies have been calculated at the DK-CCSD(T)/ANO-RCC (VTZP and VQZP) level of theory on the geometries optimized previously.

Implications for atmospheric chemistry are presented and discussed.

References

[1] H. Sun, C. Chen, and J. Bozzelli, “Structures, Intramolecular Rotation Barriers, and Thermodynamic Properties (Enthalpies, Entropies and Heat Capacities) of Chlorinated Methyl Hydroperoxides (CH2ClOOH, CHCl2OOH, and CCl3OOH)”, The Journal of Physical Chemistry A, 2000; 104 (35): 8270-8282, https://doi.org/10.1021/jp0013917

 
Feasibility study of high precision measurement of Earth Albedo in space
Authors: Löffler Thorben , Petri Jona , Fléron René , Thejll Peter , Klinkner Sabine
Published: March 2021

The Earth Albedo is one of the important parameters in the study of climate change. In this work, the scientific background and mission analysis of a space based earthshine-telescope to observe Earth Albedo using relative photometry on the Moon with an accuracy of 0.1% is presented. The earthshine, which is the sunlight reflected from Earth on the Moon, is proportional in intensity to the surface-averaged Earth Albedo. This gives an advantage over LEO observations of Earth’s surface in that a global average can only be constructed from such data by overcoming difficult and well-known issues in surface reflectance studies.  A measurement with ground-based telescopes is limited by atmospheric variability, even at the best high-altitude sites; thus, a spaceborne instrument is proposed, which provides an increase in scientific performance. ROMEO, a satellite for research in Low and Medium Earth Orbit developed by IRS, serves as a test platform for the JULIET instrument. The JULIET instrument is the first space-based earthshine-telescope, developed by the DTU. A preliminary analysis is done to verify the feasibility of carrying JULIET on ROMEO. The orbit simulation software ASTOS is used to gather realistic observability time of the moon in different orbits.  Furthermore, an optical analysis shows that the scientific performance of JULIET can exceed that of current ground-based Earth Albedo measurements. This mission is seen as the precursor of further decades-long observations of Earth Albedo using a space-based earthshine-telescope. The data will raise the accuracy of current Earth Albedo measurements by one order of magnitude and thus contribute towards increasing the overall accuracy of climate data.
A statistical framework to analyse the stratigraphy of glaciofluvial terraces from topographic data
Authors: Pollhammer Thomas , Salcher Bernhard , Kober Florian , Deplazes Gaudenz
Published: March 2021

Alluvial staircase terraces are typical Quaternary features of mid- to high latitude rivers. Their formation is linked to i) repeated events of increased sediment production, triggered by Quaternary climatic fluctuations and ii) tectonic uplift. Accordingly, terraces may act as important terrestrial archives of climatic and geodynamic information.  Comprehensive stratigraphic and topographic data qualifies the North Alpine Foreland as an ideal study region. Even though it has been subject to extensive investigations for more than a century consistent, basin wide stratigraphic models have not been proposed for more than a century (Penck and Brückner, 1909). Advances in local stratigraphy created major stratigraphic inconsistencies between the related parts of Switzerland, Germany and Austria.

In an aim to resolve these inconsistences we focus on foreland-wide high-resolution topographic data by investigating syn- and postdepositional signals behind the hypsometry and morphology of tributary terraces to the rivers Rhine and Danube.

By utilizing data from digital elevation models, geologic maps as well as outcrop information, morphostratigraphic analyses are provided via a new toolset within the framework of the software R. Semiautomatic projection of terrace data on 2D profiles allow to perform statistical analysis (based on slope, relative heights, concavity) of river long profiles and terrace-tops. We show that extracted parameters are highly suitable to make quantitative statements on fluvio-, glacio- and geodynamic processes controlling Quaternary terrace formation.

 

Penck, A., & Brückner, E. (1909). Die Alpen im Eiszeitalter. Leipzig: Tauchnitz.
Wintertime Methane Emission From the Barents and Kara Seas and Sea of Okhotsk: Satellite Evidence.
Authors: Yurganov Leonid , Carroll Dustin , Pnyushkov Andrey , Polyakov Igor , Zhang Hong
Published: March 2021

Existence of strong seabed sources of methane, including gas hydrates, in the Arctic and sub-Arctic seas with proven oil/gas deposits is well documented. Enhanced concentrations of dissolved methane in deep layers are widely observed. Many of marine sources are highly sensitive to climate change; however, the Arctic methane sea-to-air flux remains poorly understood: harsh natural conditions prevent in-situ measurements during winter. Satellite remote sensing, based on terrestrial outgoing Thermal IR radiation measurements, provides a novel alternative to those efforts. We present year-round methane data from 3 orbital sounders since 2002. Those data confirm that negligible amounts of methane are fluxed from the seabed to the atmosphere during summer. In summer, the water column is strongly stratified from sea-ice melt and solar warming. As a result,  ~90% of dissolved methane is oxidized by bacteria. Conversely, some marine areas are characterized by positive atmospheric methane anomalies that begin in November. During winter, ocean stratification weakens, convection and winter storms mix the water column efficiently. We also find that the amplitudes of the seasonal cycles over Kara and Okhotsk Seas have increased during last 18 years due to winter concentration growth. There may be several factors responsible for sea-air flux: growing emission from clathrates due to warming, changes in methane transport from the seabed to the surface, changes in microbial oxidation, ice cover, etc. Finally, methane remote sensing results are compared to available observations of temperature in deep ocean layers, estimates of Mixed Layer Depth, and satellite microwave sea-ice cover measurements.

 
On the Feasibility of Long-term Seismic Monitoring Using Freight Train Signals
Authors: Sheng Yixiao , Brenguier Florent , Boué Pierre , Mordret Aurélien , Ben-Zion Yehuda , Vernon Frank
Published: March 2021

Recent studies (Brenguier et al., 2019; Pinzon-Rincon et al., 2020) have successfully retrieved body waves between seismic arrays through the correlations of train-generated seismic signals. It remains uncertain whether these train-derived body waves are suitable for long-term seismic monitoring, which requires repeatable measurements over the years. This study tests the feasibility of obtaining stable body waves between individual broadband stations, using freight trains as noise sources. We use stations close to the railroad as markers to identify trains and pinpoint their potential locations. We select proper station pairs and perform seismic interferometry, focusing on the time windows when trains are detected. We test our workflow in southern California, with the freight trains running through the Coachella Valley. We successfully retrieve stable body-wave signals over ten years. We perform a weekly stacking to improve the signal-to-noise ratio and estimate the relative time shift. Our preliminary time-shift measurements reveal a systematic long-term increasing trend for station pairs locating on two sides of the San Jacinto fault. The next step is to examine the results statistically to reduce the bias introduced by moving sources. Despite that the long-term trend still needs further study, our experiment demonstrates that it is possible to perform long-term seismic monitoring using train generated seismic signals.
Transdisciplinary ecosystem-based approaches to flood risk reduction supported by traditional ecological knowledge in Mikatagoko Lakes, Japan
Authors: Yoshida Takehito
Published: March 2021

Rainfall-induced floods and landslides have occurred and caused devastating impacts in recent years in Japan, and adaptation to natural disaster risks is a key to the sustainability of local communities. Traditional ecological knowledge in Japanese communities exists abundantly, such as those in disaster risk reduction and natural resource use, and it has been passed down from generation to generation. These traditional knowledge and skills have been used to benefit from nature’s gifts or ecosystem services as well as to avoid devastating impacts from natural disasters. Collaboration and cooperation by diverse stakeholders are crucial for recognizing and utilizing traditional ecological knowledge in actual solutions and actions. In this presentation, I introduce how traditional ecological knowledge has been used in disaster risk reduction in Mikatagoko Lakes area located in Fukui Prefecture, Japan. Rainfall-induced floods occur frequently in this area, but traditional land use helps to reduce inundation damage of houses and conserve biodiversity and ecosystem services including local food culture. Embankment built around the lakes has been renovated not only for flood risk reduction but also for biodiversity conservation, also supported by traditional ecological knowledge in this area. The Mikatagoko nature restoration committee, in which diverse local stakeholders participate and collaborate, has played a significant role in these actions and solutions. Our experiences suggest that transdisciplinary ecosystem-based approaches contribute to the sustainability of local communities and the collaborative platform among local stakeholders is important in taking advantage of traditional ecological knowledge in actual solutions and actions.
Felsic melt migration via porous flow – a numerical modeling approach
Authors: Maierová Petra , Hasalová Pavlína , Schulmann Karel
Published: March 2021

Melting of the continental crust and subsequent melt transport has been most thoroughly described in the case of metasedimentary rocks. In these rocks segregation and migration of melt occur either through an interconnected network of veins and melt-rich layers (leucosome) or in form of diapirs. For these rocks, porous flow of melt at grain scale is mostly regarded only as a transient stage of separation of melt from the solid rock.

An entirely different style of melting and melt transport occurs in the case of felsic metaigneous rocks. We use the example from the Bohemian Massif, the eastern European Variscan belt, where metaigneous migmatites were studied in large detail. Here, melt did not segregate from the solid rock but migrated pervasively along most of the grain boundaries and equilibrated with the host rock. This equilibration resulted in formation of a continuous sequence of texturally, geochemically and compositionally different migmatites.

The question arises, what are the conditions and driving forces for this unusual behavior. We attempt to address this question by means of numerical modeling of two-phase flow (i.e. flow of porous solid matrix and melt), using the open-source finite-element ASPECT code (aspect.geodynamics.org). Most previous numerical studies of this process were either purely generic or focused on the melting of the mantle. In order to study this process in crustal conditions, we set up a 2D crustal-scale thermo-mechanical model that includes melting and freezing. We investigate the role of material properties (viscosity, solidus and liquidus temperatures, solid matrix permeability, melt composition) and thermal and velocity boundary conditions, as well as the effect of grid resolution. The results are discussed in terms of realistic parameter values and possible styles of melt migration and deformation of the matrix.
Do fungi and bacteria respond similar across a steep local pH gradient?
Authors: Kjoller Rasmus , Cruz-Paredes Carla
Published: March 2021

Soil pH is consistently recorded as the single most important variable explaining bacterial richness and community composition locally as globally. Bacterial richness responds to soil pH in a bell-shaped pattern, highest in soils with near-neutral pH, while lower diversity is found in soil with pH >8 and <4.5. Also, community turnover is strongly determined by pH for bacteria. In contrast, pH effects on fungi is apparently less pronounced though also much less studied compared to bacteria. Still, pH appears to be a significant determinant for fungal communities but typically not the most important. Rarely are bacterial and fungal communities co-analyzed from the same field samples taken across pH gradients. Here we analyze the community responses of fungi and bacteria in parallel over an extreme pH gradient ranging from pH 4 to 8 established by applying strongly alkaline wood ash to replicated plots in a Picea abies plantation. Bacterial and fungal community composition were assessed by amplicon-based meta-barcoding. Bacterial richness were not significantly affected by pH, while fungal richness and a-diversity were stimulated with higher pH. We found that both, bacterial and fungal communities increasingly deviated from the untreated plots with increasing amount of wood ash though fungal communities were more resistant to changes than bacterial. Soil NH4, NO3 and pH significantly correlated with the NMDS pattern for both bacterial and fungal communities. In the presentation we will discuss resistance versus sensitivity of different fungal functional guilds towards higher pH as well as the underlying factors explaining the community changes.
Teaching and learning about ethical aspects of environmental science with graduate students
Authors: Palinkas Cindy
Published: March 2021

Humans and their environment are inherently linked, especially in coastal and estuarine regions, and scientific and social values often must be balanced in ecosystem management and decision-making. Graduate students discuss these balances in a 1-credit seminar offered via the Marine, Estuarine and Environmental Science (MEES) program, an inter-institutional program within the University System of Maryland. The MEES program uses an interdisciplinary approach to train students in scientific discovery, integration, and application to generate new knowledge and to solve environmental problems, including social sciences. In the seminar, graduate students examine these problems through the lens of Geoethics, the ethical, social and cultural implications of geoscience research and practice, using a case-study approach. After a brief introduction to the concept, students develop a list of topics to examine throughout the seminar. In Spring 2020, these topics included climate-change communication, field harassment, community-based science, sustainability science, and preserving biodiversity. At the end of the semester, students give a presentation on ethical aspects of their own research.
Applicability of carbonate reference materials as matrix-matched standards for in-situ LA-ICPMS U-Pb dating of Sulphates 
Authors: Beranoaguirre Aratz , Vasiliev Iuliana , Gerdes Axel
Published: March 2021

Recent developments on analytical capabilities in the field of in-situ laser ablation mass spectrometry (LA-ICPMS) have expanded the applications of U-Pb geochronometers in low-U minerals such as carbonates (Roberts et al. 2020) or garnets (Millonig et al., 2020). The rapid development of the technique requires well-characterized, matrix-matched reference materials, which are essential for ion probes or LA-ICPMS due to potential matrix effects. However, given the unavailability of standards for some minerals, the use of non-matrix-matched standards, i.e. reference materials that are different to the sample, have been also addressed (Piccione et al., 2019).

In this contribution, we explored the possibility of using carbonate reference materials for in-situ U-Pb dating of sulphates. For that purpose, we selected samples from the Messinian Salinity Crisis because their ages are well established by cyclostratigraphy and thus can be compared with ages obtained by LA-ICPMS analysis. Data was acquired using a RESOLution 193 nm ArF excimer laser coupled to a (I) sector field ICP-MS (ElementXR) or (II) multicollector ICP-MS (Neptune Plus).

The majority of the samples (27 out of 32) failed due to the elevated common-Pb content and low 238U/204Pb ratios. Nevertheless, five of the samples showed greater amounts of U and U/Pb ratios of up to 600; therefore, regression lines could be drawn and ages are calculated with 5-10 % of uncertainty. These ages obtained are within error of the cyclostratigraphic ages already published (Vasiliev et al., 2017).

 

Millonig et al., (2020) Earth Planet. Sci. Lett. 552, 116589; Piccione et al. (2019) Geosphere 15 (6), 1958– 1972; Roberts et al. (2020) Geochronology 2, 33–61; Vasiliev et al. (2017) Palaeogeogr. Palaeoclimatol. Palaeoecol. 471, 120-133.
Improve Drone Survey Hazard Mapping technology to decipher landslide activity and geomorphological evolution
Authors: Chang Kuo-Jen , Chang Ho-Hsuan , Hsieh Yu-Chung , Huang Mei-Jen
Published: March 2021

The Tsaoling Landslide is one of the largest landslides in Taiwan caused by the Chi-Chi Earthquake in 1999. More than 130 million cubic meters of rocks and debris blocked the Chingshui Stream channel and formed a landslide dammed lake. In July 2004, Typhoon Mindulle completely filled the dam by the debris of the landslides initially situated on the higher upstream regions. Since then, the river channel in the region of the filled dam lake and the seismogenic Tsaoling landslide accumulation began to cut down by fluvial erosion and transportation, eventually forming multiple river terraces and deep valley. In 2009, extreme heavy rain fall hit the area again by the typhoon Morakot, causing deformation of the eastern flank of the landslide area and major river channel migration. However, relative environmental changes and geomorphical evolution in Tsaoling landslide area have received less attention. In recent years, the remote sensing technology improves rapidly, providing a wide range of image, essential and precise geoinformation. The Small unmanned aircraft system (sUAS) has been widely used in landslide monitoring and geomorphic change detection. On the basis of self-made drones, we have established a multi-temporal high-resolution DTMs, so as to access and to monitoring the post-landslide activities and topographic changes the Tsaoling area regularly and continuously. The result shows that, especially during the monsoon (spring rainy season) in June 2017, the small cliff of minor scarp on the main sliding surface has an important cliff line retreat. The maximum retreat distance exceeds 150 meters, and the volume of the landslide situated on the original sliding surface exceeds 1.5 million cubic meters. Over the next few years, the data set indicated that the topography of the area change continued. In this study, on the one hand, we are actively exploring new algorithms to minimize the relative error of the terrain in each period to accurately calculate the morphological changes in each period. On the other hand, the geomorphic changes indicate the landslide activity, and the characteristics of the river processes in the Tsaoling landslide area. Since 2016, through 8 multi-temporal UAS missions in Tsaoling area, the results indicate that the area is continues to deform and remain active. As a result, it is still worthwhile to monitor continuously.
Capturing Glacier-Wide Cryoseismicity With Distributed Acoustic Sensing
Authors: Walter Fabian , Paitz Patrick , Fichtner Andreas , Edme Pascal , Gajek Wojciech , Lipovsky Bradly P. , Martin Eileen
Published: March 2021

Over the past 1-2 decades, seismological measurements have provided new and unique insights into glacier and ice sheet dynamics. At the same time, sensor coverage is typically limited in harsh glacial environments with littile or no access. Turning kilometer-long fiber optic cables placed on the Earth’s surface into thousands of seismic sensors, Distributed Acoustic Sensing (DAS) may overcome the limitation of sensor coverage in the cryosphere.

First DAS applications on the Greenland and Antarctic ice sheets and on Alpine glacier ice have highlighted the technique’s superiority. Signals of natural and man-made seismic sources can be resolved with an unrivaled level of detail. This offers glaciologists new perspectives to interpret their seismograms in terms of ice structure, basal boundary conditions and source locations. However, previous studies employed only relatively small network scales with a point-like borehole deployment or < 1 km cable aperture at the ice surface.

Here we present a DAS installation, which aims to cover the majority of an Alpine glacier catchment: For one month in summer 2020 we deployed a 9 km long fiber optic cable on Rhonegletscher, Switzerland, and gathered continuous DAS data. The cable followed the glacier’s central flow line starting in the lowest kilometer of the ablation zone and extending well into the accumulation area. Even for a relatively small mountain glacier such as Rhonegletscher, cable deployment was a considerable logistical challenge. However, initial data analysis illustrates the benefit compared to conventional cryoseismological instrumentation: DAS measurements capture ground deformation over many octaves, including typical high-frequency englacial sources (10s to 100s of Hz) related to crevasse formation and basal sliding as well as long period signals (10s to 100s of seconds) of ice deformation. Depending on the presence of a snow cover, DAS records contain strong environmental noise (wind, meltwater flow, precipitation) and thus exhibit lower signal-to-noise ratios compared to conventional on-ice seismic installations. This is nevertheless outweighed by the advantage of monitoring ground unrest and ice deformation of nearly an entire glacier. We present a first compilation of signal and noise records and discuss future directions to leverage DAS data sets in glaciological research.

 

 

 
Automated Mapping of Radar-Dark Fluvial Features on Saturn's Moon, Titan
Authors: Skaggs Elizabeth
Published: March 2021

Titan, Saturn's moon, is the only body in our solar system besides Earth to have liquids on its surface in the form of lakes, rivers, and seas - although the liquids are mainly hydrocarbons like methane and ethane. The liquids on Titan appear to flow in similar ways to those on Earth and create comparable fluvial patterns such as meandering rivers and dendritic fluvial systems. This project utilizes SAR data obtained from the Cassini-Huygens mission via Titan Trek to identify networks of inferred fluvial systems. We focus on data swaths T28 and T29 surrounding Ligeia Mare and Kraken Mare between 210 and 360 Longitude in Titan’s northern hemisphere. Previous studies (e.g. Burr et al., 2013) interpreted fluvial networks, principally from radar-light features. We focus on radar-dark features, applying an automated technique from Yang et al (2015) to map networks of presumed fluvial origin and compare them with our own visual mapping. Yang et al. used these automated techniques to map various known fluvial systems on Earth that appear radar-dark. Our application of the technique to the Titan study area is successful in identifying features that we had mapped by hand and other features that we had not identified in our visual mapping. The technique was more successful for imagery with less noise and less successful as noise level increased. The automated technique shows great promise for more widespread, rapid identification and mapping of the fluvial network.
Quantitative Sediment Storage Chronology Associated with European Colonization of the Mid-Atlantic U.S. and its Application to Watershed Scale Sediment Routing
Authors: Pizzuto James
Published: March 2021

As sediment is carried through watersheds, it may be stored in floodplains and other alluvial deposits, remaining in place for hundreds to millions of years before being remobilized and transported farther downstream.  Sediment routing models based on reservoir theory can account for time-varying sediment storage and predict lags in sediment delivery imposed by sediment storage, but observational data are needed to construct and validate these models.  Because of the long timescales involved, direct observations are rarely useful, but stratigraphic observations coupled with sediment dating techniques can be used to quantify the amount of sediment stored through time and its associated age and storage (or transit) time distributions. To illustrate this approach, a meta-analysis of published geologic data is used to quantify river corridor storage through time associated with European colonization of the mid-Atlantic U.S.  The history of floodplain growth from Holocene to the present is summarized by empirical distributions extracted from stratigraphic data; distributions were sampled to create thousands of synthetic age-depth curves.  Deposits predating European colonization range in age from >18,000 yrs. to 225 yrs. B.P. and with a median thickness of 40% of the total accumulation; sedimentation rates for these deposits are low (median = 0.06 cm/yr).  The median thickness of sediments deposited between 1750 and 1900 (“legacy sediments”) comprises 36% of the total; the median accumulation rate of legacy sediments is 0.32 cm/yr.  The median thickness of sediments deposited after 1950 represents 11% of total accumulation, and the median contemporary sedimentation rate of 0.26 cm/yr is statistically indistinguishable from that of legacy sediments.  Synthetic vertical sequences can be recast as age distributions, and when combined with geomorphic mapping and assessment of patterns of erosion through time, as storage time distributions as well.  Age and storage time distributions at 1000 yrs. B.P., in 1900 A.D., and at present are highly variable, and could be represented by many different mathematical functions, though averaged data appear to be heavy-tailed.   Records of mass accumulation through time and the present and past age and storage time distributions provide useful summaries of the history of sediment storage, and can be used to calibrate and verify watershed scale sediment routing models over millennial timescales.
Landscape Patches Influencing Runoff and Sediment Yield and Flow Hydrodynamics in The Loess Plateau, China
Authors: Sun Ruoxiu , Zhang Jianjun , Ma Li
Published: March 2021

The Loess Plateau is located in arid and semi-arid region, and the fragmentation of vegetation patches is large. However, the combination of vegetation patches to the runoff and sediment yield on the slope is not clear yet. To evaluate the influence of vegetation patch type and number on runoff, sediment and hydrodynamic parameters, this study established field runoff plots with different landscape patch types, including bare land, S-road patches, strip patches, grid patches and random patches, as well as different quantities patches of 5, 10, 15 and 20. The results showed that the runoff yields of the four vegetation patch types decreased by 16.1%–48.7% (p<0.05) compared with that of bare land, whereas sediment yields decreased by 42.1%–86.5% (p<0.05). Also, the resistance coefficients of the poorly connected patch patterns, including strip patches, grid patches and random patches, ranged between 0.2–1.17 times higher than that of the well-connected S-road patch pattern, and the stream power decreased by 33.3%–50.7% (p<0.05). Under a uniform distribution of vegetation patches, the runoff rate and sediment yield decreased significantly with an increased number of patches. Although the increase in the number of vegetation patches also resulted in a decrease inflow shear stress and stream power to different degrees, the differences between the combinations with similar patch numbers were not significant. Besides, the sensitivity of soil to erosion decreased with an increasing number of the patch in the vegetation landscape, whereas the sensitivities of patch combinations with poor connectivity were lower than those with good connectivity. From this perspective, the optimization of vegetation in the Loess Plateau region requires sufficient consideration to reducing the connectivity of vegetation patches and increasing the density of patches.
Applying cluster analysis to seismic tomography models: Uncovering similarities and differences in the spatial and spectral domains
Authors: Rahimzadeh Bajgiran Moloud , Colli Lorenzo
Published: March 2021

In recent years, several types of Machine Learning (ML) methods have been employed by Earth scientists to extract patterns and structures from multi-dimensional feature spaces. In this regard, images of the mantle obtained by different seismic tomography (ST) models are diverse datasets with varying structures due to their different theoretical approximations and input data. In this work, we apply an unsupervised ML method, K-means clustering, on ST models to explore their similarities and differences to improve our physical understanding of the Earth’s interior. The K-means clustering method requires ST models to be standardized in a three-dimensional domain. For this purpose, we implement a weighted average technique to resample ST models to radial structural zones with uniform horizontal grid resolutions. However, the homogenized ST models still have 103-104 parameters, which need to be distilled into a small number of summary features. Feature selection is thus a key part of this study: features should be independent from unphysical effects of inversion choices (e.g., the damping factor) and should instead capture the essence of the geological structure. Preliminary results obtained using the center of mass as the attribute to represent the longest wavelength part of the mantle structure show that P-wave and S-wave models do not cluster separately. Therefore, compositional anomalies do not play an essential role at these spatial scales. We plan to expand our analysis by including more summary attributes from both the spatial as well as the frequency domain. 
A probabilistic approach to oxygen isotope modelling of speleothem data with age uncertainties
Authors: Axelsson Josefine , Nilsson Andreas , Sjolte Jesper
Published: March 2021

Due to age uncertainties and poor resolution in speleothems, age-depth modelling techniques are often implemented for cross-examinations. In this study, we use a variation of the analogue method to perform a pseudo-proxy reconstruction of the large-scale variability in Indian and East Asian monsoon precipitation using synthetic oxygen isotope records from speleothem sites and an isotope-enabled climate model.

We present a probabilistic approach to synchronize speleothems through oxygen isotope data and individual independent age constraints, achieved by co-estimating the regional δ18O variations through time. The δ18O variability is modelled using Gaussian processes, and an adaptation of BACON age-depth model is further used for the individual speleothem chronologies.

The method is tested using synthetic speleothem data generated from the ECHAM/MPI-OM climate model and corrupted through realistic noise from speleothems from the SISAL database.

By incorporating accurate and realistic depth-dependent age-uncertainties rather than shifting, stretching or compressing the time-series of oxygen isotope data, this modelling approach may lead to advancements of handling speleothem data for regional to global evaluations on variability between speleothems and timescales.
Dynamic and Thermodynamic Impacts of Climate Change on Organized Convection in Alaska
Authors: Poujol Basile , Prein Andreas , Muller Caroline , Molina Maria
Published: March 2021

Organized convective systems produce heavier downpours and can become more intense with climate change. While organized convection is well studied in the tropics and mid-latitudes, few studies have focused on the physics and climate change impacts of pan-Arctic convective systems, where they can produce flash flooding, landslides, or ignite wildfires.

We use a convection-permitting model to simulate Alaska’s climate under current and end of the century high emission scenario conditions. We apply a precipitation tracking algorithm to identify intense, organized convective systems, which are projected to triple in frequency and extend to the northernmost regions of Alaska under future climate conditions. The present study assesses the reasons for this rapid increase in organized convection by investigating dynamic and thermodynamic changes within future storms and their environments, in light of canonical existing theories for mid-latitude and tropical deep convection.

 

In a future climate, more moisture originates from Arctic marine basins and relative humidity over continental Alaska is projected to increase due to sea ice loss, which is in sharp contrast to lower-latitude land regions that are expected to become drier. This increase in relative humidity favors the onset of organized convection through more unstable thermodynamic environments, increased low-level buoyancy, and weaker downdrafts.

Our confidence in these results is increased by showing that these changes can be analytically derived from basic physical laws. This suggests that organized thunderstorms might become more frequent in other pan-Arctic continental regions highlighting the uniqueness and vulnerability of these regions to climate change.
Drivers of intermittent reduction in ocean heat transport into the Getz Ice Shelf cavity
Authors: Steiger Nadine , Darelius Elin , Wåhlin Anna , Assmann Karen
Published: March 2021

Ice shelves in West Antarctica have been thinning during the last decades due to an increased supply of ocean heat that melts the ice from below. The Getz Ice Shelf in the western Amundsen Sea has experienced an inflow of warm water during 2016-2017, but intermittent events of reduced heat content occur during this period. The processes behind the variability of heat transport towards the Antarctic ice shelves on daily to decadal time scales are not well known.
Here, we present possible drivers and implications of these events of reduced heat content. We find that they are preceded by strong easterly winds that open up a coastal polynya and depress the cold Winter Water towards the ocean floor. Simultaneously, the ocean current flowing towards the ice shelf veers to the right and aligns with the ice shelf front rather than entering the ice shelf cavity. The heat transport into the ice shelf cavity is consequently reduced by 22% in winter 2016. These events do not occur during winter 2017, possibly due to stronger stratification and weaker winds.