bluuebunny/crossref_metadata_2025 huggingface dataset:
Mapping 3-D mantle electrical conductivity using Swarm, Cryosat-2 and ground observatory data
Authors: Kuvshinov Alexey , Grayver Alexander , Tøffner-Clausen Lars , Olsen Nils
Published: March 2020

In this contribution, we report on our recent attempts to detect lateral variations of the electrical conductivity at mid mantle depths (400­ – 1600 km) using 6 years of Swarm, Cryosat-2 and observatory magnetic data. The approach involves a three-dimensional (3-D) inversion of matrix Q-responses. These responses relate spherical harmonic coefficients of external (inducing) and internal (induced) parts of the magnetic potential, derived for geomagnetic variations at periods longer than 1 day and hence mainly describing signals of magnetospheric origin (i.e. external also to satellites, as required). In addition to the inversion results, we discuss potential ways to improve the recovery of 3-D conductivity structures in the mantle.
Three-dimensional depth-to-basement modelling based on seismic and potential field data – basement configuration in the westernmost Polish Outer Carpathians
Authors: Mikołajczak Mateusz , Barmuta Jan , Ponikowska Małgorzata , Mazur Stanislaw , Starzec Krzysztof
Published: March 2020

The Silesian Nappe in the westernmost part of the Polish Outer Carpathians Fold and Thrust Belt exhibits simple, almost homoclinal character. Based on the field observations, a total stratigraphic thickness of this sequence equals to at least 5400 m. On the other hand, the published maps of the sub-Carpathian basement show its top at depths no greater than 3000 m b.s.l. or even 2000 m b.s.l. in the southern part of the Silesian Nappe. Assuming no drastic thickness variations within the sedimentary sequence of the Silesian Nappe, such estimates of the basement depth are inconsistent with the known thickness of the Silesian sedimentary succession. The rationale behind our work was to resolve this inconsistency and verify the actual depth and structure of the sub-Carpathian crystalline basement along two regional cross-sections. In order to achieve this goal, a joint 2D quantitative interpretation of gravity and magnetic data was performed along these regional cross-sections. The interpretation was supported by the qualitative analysis of magnetic and gravity maps and their derivatives to recognize structural features in the sub-Carpathian basement. The study was concluded with the 3D residual gravity inversion for the top of basement. The cross-sections along with the borehole data available from the area were applied to calibrate the inversion.

In the westernmost part of the Polish Outer Carpathians, the sub-Carpathian basement comprises part of the Brunovistulian Terrane. Because of great depths, the basement structure was investigated mainly by geophysical, usually non-seismic, methods. However, some deep boreholes managed to penetrate the basement that is composed of Neoproterozoic metamorphic and igneous rocks. The study area is located within the Upper Silesian block along the border between Poland and Czechia. There is a basement uplift as known mainly from boreholes, but the boundaries and architecture of this uplift are poorly recognized. Farther to the south, the top of the Neoproterozoic is buried under a thick cover of lower Palaeozoic sediments and Carpathian nappes.

Our integrative study allowed to construct a three-dimensional map for the top of basement the depth of which increases from about 1000 m to over 7000 m b.s.l. in the north and south of the study area, respectively. Qualitative analysis of magnetic and gravity data revealed the presence of some  basement-rooted faults delimiting the extent of the uplifted basement. The interpreted faults are oriented mainly towards NW-SE and NE-SW. Potential field data also document the correlation between the main basement steps and important thrust faults.

 

This work has been funded by the Polish National Science Centre grant no UMO-2017/25/B/ST10/01348
The spatial and temporal distribution of Arsenic speciation along Lao-Jie stream on Taoyuan tableland, Taiwan
Authors: Tzu-Jung Liu , Chuen-Fa Ni , Jiin-Shuh Jean , Chu-Ching Lin
Published: March 2020

Arsenic pollution was recognized to be an important environmental problem. Most relevant studies have focused on the groundwater systems in alluvial fans. This study aims to assess the spatial and temporal distributions of arsenic concentration and the variations of arsenic species along Lao-jie Stream in Taoyuan City, Taiwan. The river sediment, pore water, and surface water (river) samples were taken at fixed locations along Lao-jie stream. There were 10 surface water, 8 pore water, and 8 shallow river sediment samples included in the analysis. s (n = 8). Results show that the arsenic concentration changes significantly in summer (June) and autumn (September). The phase characteristic is also different in different seasons. There is no obvious concentration change in rivers. The averaged concentration in June and September were 1.609μg / L and 1.067μg / L. However, the averaged pore water concentration was 4.089μg / L in June and was 4.829μg / L in September. The averaged concentration in shallow riverbed sediment samples were 4.435 mg / Kg in June and 6.223 mg / Kg in September. Because of stream discharge rates at different sampling times, the total arsenic concentration in autumn was generally higher than that in summer. Additionally, and the arsenic concentration for surface water and pore water showed significantly different pattern along the stream. The correlation of arsenic concentration was obtained based on samples taken from surface water and pore water in summer time. However, in the summer time the inverse proportional relation was obtained as compared with the arsenic concentration obtained from the shallow sediments. In autumn, the arsenic concentration in the pore water samples is proportional to the arsenic concentration in the sediment samples. The spatial distributions of pore water and sediment samples along the stream are similar. The results also showed that the arsenic concentration of sediments in the autumn was higher than that in the summer, which might be influenced by the content of iron oxide. The concentration ratios of As (III) with As (V) for pore water is 23.8: 76.2 and for sediments is 15:85 in summer. However, the ratios for pore water is 51.4: 48.6 and for sediment is 11.4: 88.6 in autumn. The As (III) in pore water increased 27.6% in autumn and As (V) in sediments increased 3.6% in winter.
A Lightweight, Microservice-Based Research Data Management Architecture for Large Scale Environmental Datasets
Authors: Götz Alexander , Munke Johannes , Hayek Mohamad , Nguyen Hai , Weber Tobias , Hachinger Stephan , Weismüller Jens
Published: March 2020

LTDS ("Let the Data Sing") is a lightweight, microservice-based Research Data Management (RDM) architecture which augments previously isolated data stores ("data silos") with FAIR research data repositories. The core components of LTDS include a metadata store as well as dissemination services such as a landing page generator and an OAI-PMH server. As these core components were designed to be independent from one another, a central control system has been implemented, which handles data flows between components. LTDS is developed at LRZ (Leibniz Supercomputing Centre, Garching, Germany), with the aim of allowing researchers to make massive amounts of data (e.g. HPC simulation results) on different storage backends FAIR. Such data can often, owing to their size, not easily be transferred into conventional repositories. As a result, they remain "hidden", while only e.g. final results are published - a massive problem for reproducibility of simulation-based science. The LTDS architecture uses open-source and standardized components and follows best practices in FAIR data (and metadata) handling. We present our experience with our first three use cases: the Alpine Environmental Data Analysis Centre (AlpEnDAC) platform, the ClimEx dataset with 400TB of climate ensemble simulation data, and the Virtual Water Value (ViWA) hydrological model ensemble.
NaFoLiCA: Synoptic-scale controls of fog and low cloud variability in the Namib Desert
Authors: Andersen Hendrik , Cermak Jan , Fuchs Julia , Knippertz Peter , Gaetani Marco , Quinting Julian , Sippel Sebastian , Vogt Roland
Published: March 2020

This contribution presents new findings on synoptic-scale mechanisms that control the day-to-day variability of fog and low clouds (FLCs) in the Namib region.
FLCs are a defining element of the Namib-region climate and a crucial source of water for many species and ecosystems. Still, little is known on the processes driving Namib-region FLCs, in large part due to the very sparse observational records. Specifically, there is an ongoing debate in the scientific literature concerning the relevance of different mechanisms responsible for fog formation in the region. In this contribution, a new long-term satellite-based data set of FLC occurrence is used in conjunction with reanalysis data and backtrajectories to systematically analyze dynamical and thermodynamical differences between days with and without FLCs in the central Namib during two different seasons. The main findings are:

Central-Namib FLCs are nearly always associated with the advection of marine-boundary-layer air masses.

The variability of the overall FLC coverage in the central Namib is largely driven by dynamics at the synoptic scale.

Seasonally different synoptic-scale mechanisms determine the probability of the occurrence of FLCs in the central Namib.

The findings lead to a better understanding of Namib-region FLCs and help broaden the understanding of low clouds along the southwestern African coastline and the southeast Atlantic. 
The impact of SST front on the surface wind in the southern Indian Ocean
Authors: Cheng Xuhua
Published: March 2020

 Using 28-year satellite-borne Special Sensor Microwave Imager observations, features of high-wind frequency (HWF) over

the southern Indian Ocean are investigated. Climatology maps show that high winds occur frequently during austral winter,

located in the open ocean south of Polar Front in subpolar region, warm flank of the Subantarctic Front between 55oE-78oE, 

and south of Cape Agulhas, where westerly wind prevails. The strong instability of marine atmospheric boundary layer

accompanied by increased sensible and latent heat fluxes on the warmer flank acts to enhance the vertical momentum mixing,

thus accelerate the surface winds. Effects of sea surface temperature (SST) front can even reach the entire troposphere

by deep convection. HWF also shows distinct interannual variability, which is associated with the Southern Annual Mode

(SAM). During positive phase of the SAM, HWF has positive anomalies over the open ocean south of Polar Front, while

has negative anomalies north of the SST front. A phase shift of HWF happened around 2001, which is likely related to the

reduction of storm tracks and poleward shift of westerly winds in the Southern Hemisphere.
Volcanic impact on cirrus clouds
Authors: Sporre Moa , Friberg Johan , Sourdeval Odran , Sandvik Oscar , Martinsson Bengt
Published: March 2020

Cirrus clouds have a net warming effect on climate due to their high altitude and low optical thickness. Small changes in their properties may however shift this to a stronger warming or a cooling. Aerosol particles can strongly affect cirrus cloud properties since they can act as ice nuclei (IN) for the ice crystals. How downwelling sulfate aerosols from the stratosphere affect cirrus clouds is highly unknown but important both in terms of volcanic impact on climate and possible geoengineering through sulfate injections in the stratosphere. In this study we investigate how the microphysical properties of cirrus clouds change with aerosol loading in the lowermost stratosphere (LMS). The study is focused on the midlatitudes where the descending air motion in the stratosphere result in aerosol downwelling from the stratosphere to the troposphere. The study is conducted during 11 years (2006 - 2016) when the stratosphere had varying levels of aerosol load due to volcanic eruptions. 

The cirrus clouds are studied using the satellite dataset DARDAR (raDAR/liDAR) which combines data from the CloudSat radar and CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation) lidar. Also the aerosol loading in the LMS is retrieved using a satellite dataset, from CALIPSO (Friberg2018). The first results show that the ice water content of the cirrus clouds decrease when the aerosol loading in the LMS increase. This change occur mainly during spring and autumn for homogeneously frozen cirrus clouds. The results regarding the effective radius of the ice crystals are more uncertain but the effective radius also seem to decrease with increased aerosol loading in the LMS. However, this is mainly seen in the northern hemisphere which has experienced the largest changes in aerosol load due to volcanic eruptions during this period. Also data of ice crystal number concentration are being processed and will be studied to better understand the impact on the cirrus clouds from the downwelling stratospheric aerosol.

References

Friberg, J., Martinsson, B. G., Andersson, S. M., and Sandvik, O. S.: Volcanic impact on the climate - The stratospheric aerosol load in the period 2006-2015, Atmospheric Chemistry and Physics, 18, 11 149–11 169, https://doi.org/10.5194/acp-18-11149-2018, 2018.
Do we need more trees to achieve carbon neutrality on livestock farms? Accounting for the negative emissions on small tropical livestock farms in Ecuador
Authors: Iñamagua Uyaguari Juan Pablo , Sangoluisa Pamela , Green David R , Fitton Nuala , Smith Pete
Published: March 2020

Ecuador, as a signatory to the United Nations Framework Convention on Climate Change, in its Nationally Determined Contribution, has expressed its intention to reduce greenhouse gas emissions (GHG), with a focus on the energy and forest sectors. Despite the socio-economic importance and the growing pressure of agricultural and livestock activities on land use change, this sector is not explicitly considered in the national mitigation goals. Currently, grasslands occupy 57% of agricultural land in Ecuador and cattle, being the main livestock activity, is responsible for at least 46% of agricultural emissions, the third largest source of GHG emissions, after land use change and energy. The foot and mouth disease national eradication campaign carried out in 2016, shows that the cattle population is distributed over approximately 275000 farms, where 80% of these farms can be considered as subsistence systems (<20 animals/farm). Due to the heterogeneity of these systems, mitigation strategies focused on reducing methane from enteric fermentation can be difficult to apply, measure, and report. Another possibility for cattle livestock systems is to focus the mitigation opportunities on maintaining carbon stocks and enhancing carbon sequestration through the management of trees on farms. This study analyses the contribution of trees in pasture areas and forests on small livestock systems for offsetting GHG emissions from cattle activities. In 2018, a survey was performed on 101 farms distributed across the Amazon and coastal region in Ecuador, where herd characteristics and management were recorded.  Farmers were asked to draw the boundaries of the farm on a Google Earth map, identifying the extent of primary and secondary forest areas. Trees in pasture areas were measured on plots of 1000m2, with two plots per farm. A UAV survey was performed using a DJI Mavic Pro quadcopter, equipped with an RGB camera, over plots off 125m2, and at a flying altitude of 70m. For this work, 37 farms were selected (13 in the Amazon region and 24 in the Coastal region) and GHG emissions calculated from cattle livestock activities using IPCC Tier 1 equations. The aboveground biomass for pasture areas was estimated using the Jucker et al., 2017 equation, with tree characteristics derived from the UAV survey. Average results were extrapolated to the total pasture area reported by farmers in the survey. Primary and secondary forest areas were identified from satellite images. Forest state (degradation level) was estimated using NIR data from SENTINEL-2/LANDSAT 8/PlanetScope. Aboveground biomass estimates for forests were obtained from published data using similar site conditions. Emissions from cattle activities are expressed as carbon equivalent. Biomass carbon was estimated as 0.47 of total biomass.
Benthic foraminifera as tracers in one of Africa's most polluted water bodies: The Lagos Lagoon (Nigeria)
Authors: Sariaslan Nisan , Fajemila Olugbenga T. , Langer Martin
Published: March 2020

The Lagos Lagoon is among Africa’s largest estuarine ecosystems. It is bordered by one of the fastest growing megacities in the world (Lagos) and the ultimate repository of contaminants carried in industrial, municipal and agricultural wastes. The high levels of pollutants have progressively deteriorated the water quality, adversely affected marine ecosystems, impacted the livelihood of the coastal population and pose serious risks to human health. Benthic foraminifera are excellent proxies and sensitive bioindicators of environmental disturbances but comprehensive studies on the structure, distribution, diversity and impact of pollution upon foraminiferal communities have not yet been conducted. In order to demonstrate the potential of foraminifera as proxies of environmental perturbations, benthic foraminifera were investigated on a lagoon-wide basis.

Lagos Lagoon has areas that range from low levels of direct impact to severely affected by various forms of anthropogenic disturbance. The goal of this study was to elucidate foraminiferal community structure, to analyze patterns of distribution and species richness and to identify taxa that track documented records of pollution in Lagos Lagoon sediments. The sediments were analyzed for a range of physicochemical properties via a multi-parameter sensor probe-device including temperature, pH, depth and total dissolved solids (TDS) measurements. Quantitative analysis of 24 sediment samples yielded a total 3872 individuals of benthic foraminifera that belong to 42 species and 25 genera. They comprise 10 porcelaneous, 22 hyaline perforate and 10 agglutinated species. Ammobaculites aff. A. exiguus, Ammotium salsum, Ammonia tepida, Ammonia parkinsoniana and Trochammina sp. have been found to be the most abundant species.

Heat maps were generated from abundance records for selected species to illustrate environmental preferences and relative resistance levels to individual forms of anthropogenic disturbance. The features recorded allow to delineate the spatial effects of hydrocarbon and heavy metal pollutants, urban sewages, and sand dredging activities. The data generated may ultimately form the basis to assess the progressive deterioration of Lagos Lagoon environments from cores by using benthic foraminifera as bioindicators of environmental perturbation.
Characterising water sources in glacierized catchments in the northern Tien Shan using stable isotopes
Authors: Saidaliyeva Zarina , Shahgedanova Maria , Wade Andrew , Yapiyev Vadim , Kapitsa Vassiliy , Kasatkin Nikolay , Severskiy Igor
Published: March 2020

The Kishi and Ulken Almaty rivers drain glacierized catchments in the northern Tien Shan, Kazakhstan. Both rivers supply water for the Almaty agglomeration with population around 2.5 million. Changes in discharge of these [and many other regional] rivers are affected by changes in all components of the cryosphere (seasonal snow, glacier ice, ground ice) as well as precipitation and ground water. Uncertainties of projections of water availability in the context of the observed climatic warming are an important economic and politic issue in this region. Knowledge of the extent, to which discharge of these rivers depends on different sources of nourishment, is important for the formulation of regional adaptation strategies and policies.

A comprehensive data set on concentrations of daily values of stable isotopes of oxygen and hydrogen, temperature, precipitation, and discharge was collected in both catchments in 2017 and 2018 in order to characterize contribution of different sources of water to total discharge. There is a clear correlation between isotopic concentrations in stream water with temperature, precipitation and discharge enabling separation between contributions of ground water (δ2H=–78.25 ‰; δ18O=–11.80 ‰), snow melt (δ2H=–84.56 ‰; δ18O=–13.20 ‰), and glacial melt (δ2H=–78.97 ‰; δ18O=–12.41 ‰). Analysis of isotopic signatures of sources of water shows separation between seasonal snow, glacier ice, rock glaciers and permafrost.

Following these preliminary results, the sampling programme has been extended in 2019 to the Ulken Almaty and Kishi Almaty (Kazakhstan), Ala-Archa and Chon Kyzyl-Cuu (Kyrgyzstan), Chirchik (Uzbekistan), Varzob-Kofarnihon (Tajikistan) catchments in 2019-2020 enabling the development of the most comprehensive data set on water isotopes in Central Asia.
Using machine learning method to classify polar stratospheric cloud types from Envisat MIPAS observations
Authors: Sedona Rocco , Hoffmann Lars , Spang Reinhold , Cavallaro Gabriele , Griessbach Sabine , Höpfner Michael , Book Matthias , Riedel Morris
Published: March 2020

Polar stratospheric clouds (PSC) play a key role in polar ozone depletion in the stratosphere. Improved observations and continuous monitoring of PSCs can help to validate and enhance chemistry-climate models that are used to predict the evolution of the polar ozone hole. Here we present the results of our study in which we explored the potential of applying machine learning (ML) methods to classify PSC observations of infrared limb sounders. Two datasets have been considered. The first dataset is a collection of infrared spectra captured in Northern Hemisphere winter 2006/2007 and Southern Hemisphere winter 2009 by the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) instrument onboard ESA's Envisat satellite. The second dataset is the cloud scenario database (CSDB) of simulated MIPAS spectra. We first performed an initial analysis to assess the basic characteristics of these datasets and to decide which features to extract from them. More than 10,000 Brightness temperature differences (BTDs) features have been generated and fed as input to the ML methods instead of directly using the infrared spectra. Next, we assessed the use of ML methods for the reduction of the dimensionality of this large feature space using principal component analysis (PCA) and kernel principal component analysis (KPCA) as well as the classification with the random forest (RF) and support vector machine (SVM) techniques. All methods were found to be suitable to retrieve information on the composition of PSCs. Of these, RF seems to be the most promising method, being less prone to overfitting and producing results that agree well with established results based on conventional classification methods.
Assessment of sediment transfer based on discharge indices for Cauvery River basin, India
Authors: Chavan Sagar , Maheshwari Shobhit
Published: March 2020

The mechanism of sediment transport is mainly governed by surface water flow within the river basins. Excessive sediment transport plays an important role in reducing the carrying capacity of channel networks, storage capacity of reservoirs/dams. An important task for most of the hydrologists is to determine the reliable stream flow estimate which causes majority of the sediment transport within river basins/stream channels. The transport effectiveness of a stream flow event of a particular magnitude in carrying a sediment load is defined as the product of the effect of that event (i.e. sediment transport rate corresponding to the stream flow event) and the frequency with which the event occurs. This approach is famously known as magnitude frequency analysis (MFA). MFA provides a mathematical framework to determine various discharge indices such as effective discharge, fraction-load discharge and functional-equivalent discharge. These indices provide information on long-term transport of sediments through river networks and are linked to the exponent of sediment rating curve (which is correlated to the size of sediments, bed armouring and river morphology). Effective discharge index represents that single discharge which carries the most amounts of sediments, whereas fraction-load discharge and functional-equivalent discharge indices deal with mean sediment load which considers the contribution of entire probability distribution of discharge. There is a dearth of attempts to study these discharge indices for Indian catchments. In the present study, lognormal distribution and Gamma distribution -based MFA approaches are used to estimate discharge indices for Cauvery River basin, India. Effectiveness of the approaches was assessed based on their ability to predict discharge indices for 12 catchments in the river basin. Results indicate that Gamma distribution-based approach provides reliable estimates of fraction-load discharge and functional-equivalent discharge. The fraction-load discharges were computed for the catchments by considering various fractions of sediment loads ranging from 10% to 90%. Plots of cumulative sediment yield were prepared for both approaches and compared with empirical cumulative sediment yield. It was observed that the Gamma distribution-based MFA approach tends to provide close match with the empirical yield.
CO2 driven changes in leaf biochemistry may have influenced fire behaviour at the Triassic-Jurassic boundary
Authors: Baker Sarah , Dewhirst Rebecca , McElwain Jennifer , Haworth Matthew , Belcher Claire
Published: March 2020

The Triassic-Jurassic Boundary marks one of the largest mass extinction events of the Phanerozoic. Across the boundary, a rise in carbon-dioxide levels and global temperatures are hypothesized to have driven significant environmental changes inducing a major floral turnover, causing vegetation structure, composition and leaf morphology to alter, and inferred wildfire activity to increase.

An example of these changes can be observed at the Astartekløft site in East Greenland, where previous work identified a change in flora from broad-leaved conifer dominated to an assemblage dominated by narrow leaved conifers, coeval with a five-fold increase in charcoal abundances.

Variations in carbon-dioxide concentrations have been shown to be capable of influencing leaf chemistry. It could therefore be hypothesized that carbon-dioxide-driven climate changes across the Triassic-Jurassic boundary may have been capable of not only inducing changes in leaf morphological fuel properties, but also variations in biochemical properties that are both capable of altering wildfire behaviour.

In order to assess this, we selected three plant species that have ancient evolutionary origins and correspond to the dominant leaf morphotypes of litter-forming vegetation observed at the Astartekløft site across the Triassic-Jurassic boundary. We grew these species in current ambient and high carbon-dioxide (Triassic-Jurassic boundary) atmospheric conditions and analysed variations in the chemistry of the leaves, using gas chromatography mass spectrometry, and assessed aspects of their flammability using micro-calorimetry. These data were used to inform a fire behaviour model to produce estimates of variations in fire behaviour, such as surface fire spread, flame length and fireline intensity across the Triassic-Jurassic boundary at Astartekløft.

Our results reveal a change in leaf chemistry that is expressed as a suppression of volatile content in the three species grown under elevated carbon-dioxide concentrations, compared to those grown under ambient conditions. By accounting for these variations in a fire behaviour model, we estimate that fire behaviour was more extreme prior to the increase in carbon-dioxide across the boundary, suggesting a switch from a period of infrequent but intense fast-moving surface fires during the Triassic, to a period of frequent but low intensity and slow spreading fires during the earliest Jurassic. Our results indicate that that increases in carbon-dioxide concentrations may have impacted leaf chemistry and thus flammability, and may therefore have played an interesting role in determining fire behaviour characteristics during this marked period of Earth’s past.  
Pushing the limits of electrical resistivity tomography measurements on a rock glacier at 5500 m a.s.l. on the Tibetan Plateau: Successes and Challenges
Authors: Krebs Nora , Voigtländer Anne , Bücker Matthias , Hördt Andreas , Schroeckh Ruben , Buckel Johannes
Published: March 2020

Geophysical methods provide a powerful tool to understand the internal structure of active rock glaciers. We applied Electrical Resistivity Tomography (ERT) to a rock glacier at an elevation of 5500 m a.s.l. in the semi-arid Nyainqêntanglha mountain range on the Tibetan plateau, China.  The investigations comprised three transects across the rock glacier and its catchment, each spanning over a distance of 296 m up to 396 m, equipped with 75 up to 100 electrodes respectively. Our measurements were successful in revealing internal structures of the rock glacier, but were also accompanied by challenges.

We successfully detected first-order permafrost structures, such as a shallow about 4 m thick active layer of low electrical resistivity values that was underlain by potentially ice rich zones of high resistivity. Further high-resistivity zones were found and interpreted as dense bed rock of adjacent slopes that undergird the loose rock glacier debris.

Challenges, we faced in the application of ERT, were mainly posed by the morphology and internal structure of the rock glacier itself. Coarse debris created a rough surface that prevented a uniform setup with accurate 4 m spacing. The presence of loosely nested blocks of pebble size up to boulders with large interspaces resulted in high contact resistances. The consequent low injection current densities and possible noisy voltage readings downgraded part of the data, causing low data density and resolution. Coupling was partly improved by attaching salt-watered sponges to the electrodes and adding more conductive fine-grained materials to the electrodes. The detected high resistivity ice layer impeded deep penetration of electrical currents, which caused that the lower limit of the permanently frozen zone could not be defined.

Despite these challenges, the captured ERT profiles are an indispensable contribution to the sparse field data on the internal structure of rock glaciers on the Tibetan plateau. Our results contribute to a better understanding of the prospective evolution of rock glaciers in dry, high mountain ranges under a changing climate.
New Total Least Squares Algorithm and Model with Applications to the Transformation among ITRF Realizations
Authors: Cai Jianqing , Dong Dalu , Sneeuw Nico
Published: March 2020

A newly developed Converted Total Least Squares (CTLS) algorithm is introduced, which is to take the stochastic design matrix elements as virtual observations, and to transform the TLS problem into a traditional Least Squares problem. This new algorithm has the advantages that it can not only easily consider the weight of observations and the weight of stochastic design matrix, but also deal with TLS problem without complicated iteration processing, which enriches the TLS algorithm and solves the bottleneck restricting the application of TLS solutions. The notable development of the CTLS reveals also that CTLS estimator is identical to Gauss-Helmert model estimator in dealing with EIV model, especially in the case of similarity coordinate transformation. CTLS has been successfully applied to the estimation of the transformation parameters, their rates and related transformed residuals between actual ITRF realizations of ITRF2014 and ITRF2008 with obvious improvement of their accuracies.
A multi-tracer study of submarine groundwater discharge into Wismar Bay, southern Baltic Sea
Authors: Ehlert von Ahn Catia Milene , Scholten Jan , Schmiedinger Iris , Liu Bo , Böttcher Michael
Published: March 2020

Submarine groundwater discharge (SGD) is considered as an important route for water and dissolved material exchange between land and coastal seas. Both freshwater and (recirculated) seawater are referred to as SGD and may impact the composition and biogeochemical processes in coastal waters. The present study focuses on the identification and the spatial variability of SGD into the Wismar Bay, in the southern Baltic Sea. On across-shore transects covering Wismar Bay waters were sampled for analysis of Radium (Ra) isotopes, stable isotopes (H, O, C, S), dissolved inorganic carbon (DIC), nutrients and major cations. In addition, sediment cores were retrieved from several stations. The detection of short-living radium isotopes (223Ra and224Ra) in surface waters of the bay indicate benthic-pelagic coupling via pore water exchange with the water column that may be an indication for SGD. Moreover, enhanced concentration of dissolved manganese and barium, resulted from anoxic pore waters, were found in areas with higher Ra activity. Pore water profiles of salinity and major ions highlight the presence of freshwater about 50 cmbsf in sediments in the central part of the bay, probably related to the presence of a coastal aquifer. In contrast, other sediments demonstrate relatively constant pore water salinity distribution with increasing depth. Slight salinity maxima in almost all core at around 6 to 12 cmbsf seems to be relict from changing bottom water salinity in the past. The water isotope composition (δ18O, δ2H) of the low saline pore water is plot close to the local meteoric water line established for Warnemünde. Saline pore waters, in contrast, have water isotope composition aligned with southern Baltic Sea surface waters. The DIC concentrations increased with depths suggesting the mineralization of organic matter within the 50 cm sediments depth at all sides. Moreover, the values of DIC even exceeding the concentration found on the percolating fresh ground water. Thus, the overall contribution of elements to the coastal ecosystem is a function of the transport processes regulating element flux across the sediment-water interface.

The investigation is supported by the DFG research training school Baltic TRANSCOAST, DAAD, and Leibniz IOW.
Possibilities and challenges of modelling the agricultural tracks at field scale
Authors: Augustin Katja , Kuhwald Michael , Duttmann Rainer
Published: March 2020

The application “FiTraM” (Field Traffic Model) models the spatially explicit wheel tracks and the field traffic intensity of agricultural vehicles from recorded GPS points. The spatial location of traffic intensities are required to analyse the effect of field traffic on the soil structure, e.g. with regard to mitigate soil compaction. The modelling is based on geometrical and geodetical calculations. The application is written in python and uses PostgreSQL and PostGIS for data storing and calculation of statistics.
The results of FiTraM are the spatially mapped wheel tracks, wheel pass frequency, wheel load and the soil pressure induced by machines (optionally). With continuous route recording various operations (sowing, harvesting, soil tillage) can be analysed in terms of the intensity of travel and the complete process chain during single crops can be mapped. These results (e.g. amount of wheel passages, summed wheel load) can be related to further soil measurements to link field traffic intensities with loss of soil functionality or reduced yield.
This contribution intends to illustrate the process of modelling the field traffic intensity by means of different agricultural working processes - from data acquisition to the statistical evaluation of the spatial modelling results. Examples of different traffic operations are used to explain how driving behaviour needs to be taken into account for modelling, such as reversing and lifting equipment (e.g. during soil tillage). The difficulties, such as the evaluation of the positional accuracy in the field and the processing of the large data sets, will be addressed.
How certain physical and meteorological catchment parameters influence water ages and transit times
Authors: Heidbüchel Ingo , Yang Jie , Musolff Andreas , Fleckenstein Jan
Published: March 2020

We employed a physically-based spatially explicit 3D model to investigate how certain catchment parameters influence water ages and water transport dynamics in low-order catchments. The parameters we explored were catchment shape, porosity, bedrock conductivity, soil conductivity decay with depth, water retention curve, precipitation frequency, precipitation sequence and precipitation event amount. Each one of the parameters has its own specific influence on water ages and transport. Some of the results were expected (higher porosity = longer transit times), some were surprising to us. For example, we found that bedrock conductivity does not have a simple straightforward relationship with catchment transit time (i.e. an increase in conductivity causing a decrease in transit time). Instead, an increase in bedrock conductivity can also result in the overall increase in catchment transit time – e.g., when this increase allows a larger proportion of water to infiltrate into the comparatively less conductive bedrock instead of flowing towards the outlet in the more conductive soil. Also, the sequence of precipitation events that constitute the atmospheric forcing does play a less important role than we expected, i.e. it does not matter how the differently-sized precipitation events driving the water flow through the catchment are arranged – as long as the precipitation event frequency is high (≤3 days) and the event amounts are Poisson-distributed. We conclude that the multitude of influences from the different parameters makes it very challenging to find rules and underlying principles in the integrated catchment response, therefore it is necessary to look at the individual parameters and their potential interactions and interdependencies in a bottom-up approach.
230Th-excess inventory and distribution in a southern Mendeleev Ridge core (Arctic Ocean): linkage with late Quaternary sedimentological and paleogeographical changes
Authors: Song Tengfei , Hillaire-Marcel Claude , Liu Yanguang
Published: March 2020

In addition to 14C-data, sedimentary excesses in 230Th  (230Thxs) in central Arctic Ocean cored sequences yielded critical time constrains and sedimentation rates estimates, at least, at sites characterized by very low sedimentation rates (<< 1cm/ka). Closer to the Russian margin, where higher accumulation rates are recorded based on 14C-ages, the setting of a reliable stratigraphy based on 230Thxs reveals more challenging, as illustrated here, based on the analysis of  a gravity core raised from the southern Mendeleev Ridge (core ARC7-E25; -179.4°E, 79.0°N; 1200 m water depth; 320 cm long). Subsamples were collected at a 4 to 8 cm interval. Measurements included: AMS 14C in foraminifera, grain size, bulk Xray mineralogy, clay mineralogy, geochemistry (Corg, Cinorg,13Corg, 238U, 234U, 230Th, 226Ra, 210Pb). Data indicate that some sediment were lost at core top. Nevertheless, 14C and 230Thxs  data allow estimating a mean sedimentation rate of about 6 to 7 mm/ka during the last two climatic cycles. A comparison of the 230Thxs inventory and distribution pattern with those from other cores allows identifying important parameters involved in the cycling of the water column-produced 230Th in this basin and its sporadic sedimentary accumulation, in particular linkages with sea-ice production over shelves, thus sea-levels, sea-ice rafting routes, grain-size and mineralogy, potential winnowing of fine fractions, role of brines and relative duration of intervals with reduced or nil sedimentation preceding 230Thxs-accumulation intervals.
Anthropogenic desilication of agricultural soils – Results from a long-term field experiment in NE Germany
Authors: Puppe Daniel , Kaczorek Danuta , Sommer Michael
Published: March 2020

Due to intensified land use (agriculture, forestry) humans directly influence silicon (Si) cycling on a global scale. In this context, especially Si exports by harvested crops (most of them are Si accumulators) and increased erosion rates generally lead to a Si loss in agricultural soils (anthropogenic desilication). Harvesting of field crops can cause Si losses of up to 100 kg Si ha-1 per year. On a global scale about 35% of total phytogenic Si is synthesized by field crops due to their relatively high Si contents as well as biomasses and this proportion is going to increase with increased agricultural production within the next decades. In order to avoid (natural) limitations of plant available Si and enhance plant growth and resistance against abiotic and biotic stresses, Si fertilization is widely used, especially in (sub)tropical agricultural systems. In this context, specific Si fertilization, for example, in the form of recycled organic siliceous materials (e.g., straw, biochar), might be a promising strategy for both increasing crop yields and decreasing desilication of agricultural soils. However, most studies focus on rice and sugarcane production and there is still only little knowledge about Si cycling in agricultural systems of the temperate zone. We analyzed soil and plant samples from an ongoing long-term field experiment (established 1963, randomized block design: plots with low, medium, and high mineral NPK fertilization rates, plots with straw fertilization in addition to NPK fertilization, control plots) in NE Germany to answer the following questions: (i) Can we observe a significant desilication (indicated by a decrease in plant available Si in soils) of agricultural systems in the temperate zone in the long term?, (ii) Is this potential desilication affected by NPK fertilization rates?, (iii) Is this potential decrease of plant available Si in soils reflected in Si concentrations of the grown plants (e.g., wheat)?, and (iv) Can we prevent potential anthropogenic desilication by straw fertilization? Here we present our first results to answer these questions. The answers to these questions will help us to obtain a deeper understanding of Si cycling in agricultural biogeosystems in the temperate zone in general and to derive practice-oriented recommendations for a more environmentally friendly and sustainable crop production in particular.
Bubble nucleation and growth in basaltic magmas as a possible source of Deep Long Period Volcanic earthquakes
Authors: Shapiro Nikolai M. , Melnik Oleg , Lyakhovsky Vladimir , Galina Natalia , Bergal-Kuvikas Olga
Published: March 2020

Deep Long Period (DLP) earthquakes have been observed in many volcanic regions and are often considered as one of the important precursors to volcanic eruptions. At the same time, the physics of the source of these earthquakes remains unclear. We focus our study on Klyuchevskoy group of volcanoes in Kamchatka, Russia, one of the World’s most active volcanic system. The DLP earthquakes in this region occur at the limit between the lower crust and the upper mantle at depths of 30-35 km where ductile flow is expected to dominate rock deformation. Their occurrence also appears to correlate with the eruptive activity. Therefore, this is natural to consider that their generating mechanism is not related to brittle mechanism but rather to pressure fluctuations in the magmatic system as often suggest for the LP seismicity in general. We suggest a possible generating mechanism related to the rapid pressure changes caused by nucleation and growth of gas bubbles in response to the slow decompression of over-saturated magma. The pressure variation is simulated using the mathematical model of bubble nucleation and growth accounting for multiple dissolved volatiles (H2O-CO2) and diffusive gas transfer from magma into growing bubbles. Results of simulations show that fast pressure increase followed by its relaxation almost to its initial level is not very sensitive to the assumptions on the values of governing parameters. Typical pressure changes of a few tens of MPa in a volume of 3500 m3 occurring on time scales of fractions of a second to a second following bubble nucleation and growth can generate seismic waves with amplitudes similar to those recorded by seismographs in the vicinity of the Klyuchevskoy volcano.
Constraining subglacial geology using ambient noise Rayleigh wave ellipticity
Authors: Jones Glenn , Kulessa Bernd , Ferreira Ana , Schimmel Martin , Berbellini Andrea , Morelli Andrea
Published: March 2020

Basal slip is an important mechanism by which glaciers and ice-sheets flow, and is a major source of uncertainty in simulations of ice-mass loss and sea level rise from the Greenland Ice Sheet (GrIS). Sub-ice geology is a dominant control on ice flow velocity with fast flow often coinciding with the presence of deformable subglacial till eroded from underlying sedimentary rocks. The subglacial geology of Greenland has received relatively little attention thus far and its control on ice flow is poorly understood. Seismic studies of the crust beneath the GrIS have been limited due to a lack of seismic stations and the reliance on earthquake event data. However, in the past decade, there has been a rapid increase in the number of both permanent and temporary seismic stations deployed in Greenland as well developments in ambient noise methods, allowing for improved spatial resolution of crustal geology.

 

Ellipticity measurements, the ratio of the horizontal to vertical component of a Rayleigh wave, have been shown to be particularly sensitive to the geological structure directly beneath the station. Ambient noise H/V measurements have been used for decades in geotechnical and civil engineering for site characterisation, making them a well-suited technique to determine the subglacial geology of the GrIS. Using all available broadband stations deployed on Greenland from 2012 to 2018 we extract Rayleigh wave ellipticity measurement from ambient noise data using the degree-of-polarization (DOP) method where meaningful signals are defined as a waveform with an arbitrary polarization which remains stable for a given time window. We invert these ellipticity measurements in the period range of 4 – 9 s to generate Vs profiles of the first 5 km beneath each station. Our inversions indicate that: (1) off-ice stations along the margins of the GrIS produce a good agreement with the litho1.0 model to within error and (2) an additional subglacial layer 1.0 - 2.0km thick with a Vs < 3.0km is necessary to match the data recorded at several of the on-ice stations. We attribute these observations to the widespread presence of sedimentary rocks beneath the GrIS, potentially capable of sustaining extensive subglacial till layers that can support enhanced basal slip.
Geoeffectiveness of the ‘Battle of Grunwald day’ in 2012
Authors: Gil Agnieszka , Modzelewska Renata , Moskwa Szczepan , Siluszyk Agnieszka , Siluszyk Marek , Wawrzynczak Anna
Published: March 2020

During the solar activity cycle 24, which started at the end of 2008, Sun was behaving silently and there were not many spectacular geoeffective events. Here we analyze the geomagnetic storm which happened on July 15 of 2012 in the 602 anniversary of the famous Polish Battle of Grunwald. According to the NOAA scale, it was G3 geomagnetic storm with Bz heliospheric magnetic field component dropping up to -20 nT, Dst index below -130 nT, AE index greater than 1300 nT and ap index being above 130 nT. It was proceeded by the solar flare of X1.4 class on 12 of July. This geomagnetic storm was accompanied by the fast halo coronal mass ejection 16:48:05 on 12 of July-the first C2 appearance, with the apparent speed 885 km/s and space speed 1405 km/s. This geomagnetic storm was classified as the fourth of the strongest geomagnetic storms from SC 24. Around that time in Polish electric transmission lines infrastructure, there was observed a significant growth of the number of failures that might be of solar origin.

Acknowledgments: the Polish National Science Centre, grant number 2016/22/E/HS5/00406.