bluuebunny/crossref_metadata_2025 huggingface dataset:
Horizontal distribution of temperature in a building-block using a Mobile Cart for Meteorological Observation (MCMO)
Authors: Kang Minsoo , Park Moon-Soo , Chae Jung-Hoon , Min Jae-Sik
Published: March 2020

Horizontal distribution of building block scale meteorological information is important to understand the disastrous weather phenomena occurred at urban areas. Most meteorological models assume the same surface temperature, or an ideal surface temperature to simulate the high-resolution wind field in or above urban boundary-layer. This study aims to establish the basic foundation for producing the high-resolution and high-quality user-specific horizontal meteorological information at an urban building block in the Seoul Metropolitan Area. Therefore, the Mobile Cart for Meteorological Observation (MCMO) was developed and used in a meteorological experimental campaign during heat wave event days.
The MCMO includes 3 air temperature sensors, 1 weather transmitter, 1 infrared surface temperature sensor, 1 GPS (global positioning system), and video camera on the mobile cart. The MCMO measures the temperature at 4 altitudes (surface, 0.5m, 1.5m, and 2.5m), latitude, longitude, and surrounding environment condition of measurement site. The observation cycle is 1 second to produce pedestrian-friendly weather information. The meteorological experimental campaign was conducted in Gwanghwamun square in the Seoul, Korea. Gwanghwamun square is complex area which has high-rise building block, wide roads of heavy traffic, and green lung. Observation period was from 1200 LST 5 August 2019 to 2200 LST 6 August 2019 including the hottest day of the year. Through the meteorological experimental campaign, the MCMO shows the detail temperature change over time, location, and altitudes. The temperature was changed as the altitude of the sun changed. When the MCMO was move through the green lung or building block, also the temperature was changed. Temperature changes were the largest at surface temperature and tended to decrease as altitude increased. The MCMO can be used to understand high-resolution weather information and horizontal distribution of temperature in urban area. Additionally, another meteorological experimental campaign will be held in the summer of 2020.
Fracture characterisation using frequency-dependent shear-wave splitting analysis of azimuthal anisotropy: application to fluid flow pathways at the Scanner Pockmark area, North Sea
Authors: Robinson Adam , Bayracki Gaye , MacDonald Calum , Callow Ben , Provenzano Giuseppe , Minshull Timothy , Chapman Mark , Henstock Timothy , Bull Jonathan
Published: March 2020

Scanner pockmark, located in the Witch Ground Graben region of the North Sea, is a ~900 m by 450 m, ~22 m-deep elliptical seafloor depression at which vigorous and persistent methane venting is observed. Previous studies here have indicated the presence of chimney structures which extend to depths of several hundred meters, and which may represent the pathways along which upwards fluid migration occurs. A proposed geometry for the crack networks associated with such chimney structures comprises a background pattern outside the chimney with unconnected vertical fractures preferentially aligned with the regional stress field, and a more connected, possibly concentric fracture system within the chimney. The measurement of seismic anisotropy using shear-wave splitting (SWS) allows the presence, orientation and density of subsurface fracture networks to be determined. If the proposed model for the fracture structure of a chimney feature is correct, we would expect, therefore, to be able to observe variations in the anisotropy measured inside and outside of the chimney.

Here we test this hypothesis, using observations of SWS recorded on ocean bottom seismographs (OBS), with the arrivals generated using two different air gun seismic sources with a frequency range of ~10-200 Hz. We apply a layer-stripping approach based on observations of SWS events and shallow subsurface structures mapped using additional geophysical data to progressively determine and correct for the orientations of anisotropy for individual layers. The resulting patterns are then interpreted in the context of the chimney structure as mapped using other geophysical data. By comparing observations both at the Scanner pockmark and at a nearby reference site, we aim to further contribute to the understanding of the structures and their role in governing fluid migration. Our interpretation will additionally be informed by combining the field observations with analogue laboratory measurements and new and existing rock physics models.

This work has received funding from the NERC (CHIMNEY; NE/N016130/1) and EU Horizon 2020 programme (STEMM-CCS; No.654462).
SO2 volcanic clouds detected from space: a new database
Authors: Tournigand Pierre-Yves , Cigala Valeria , Hammouti Mohammed , Prata Fred , Brenot Hugues , Clarisse Lieven , Steiner Andrea K. , Kirchengast Gottfried , Biondi Riccardo
Published: March 2020

Explosive volcanic eruptions can generate ash and SO2 clouds rising to the stratosphere and dispersing on a global scale. Such volcanic features are at the origin of many hazards including aircraft engine damages, ash fallouts, acid rains, short-term climate changes and health threats. It is thus crucial to monitor volcanic clouds altitude and dispersion over time in order to prevent these hazards. In the past decades, satellite monitoring techniques have proven to be efficient at detecting volcanic aerosols in the atmosphere. In particular the detection of SO2 (e.g. IASI, AIRS, GOME-2) spatial and temporal dispersion and altitude (e.g. CALIOP). However, satellite data are scattered amongst the different institutes and agencies acquiring and processing them, and their retrieval is time-consuming.

In this study, we are building a whole new database gathering SO2 volcanic cloud altitude and dispersion data of 12 VEI 4 volcanic eruptions from 2008 to 2019. The spatial and temporal dispersion is retrieved from AIRS, IASI and GOME-2 sensors, as well as from collocated backscatter data of CALIOP sensor. Cloud altitude estimations are retrieved based on IASI, CALIOP and Global Navigation Satellite System (GNSS) radio occultation (RO) data when available. Besides, GNSS RO atmospheric profiles collocated with the other sensors at 12h temporal window and 0.2° spatial window, will be included. For the first time a dataset gathering several of the primary sensors used to monitor volcanic clouds and new ones will be freely available. Such new tool provides direct access to volcanic clouds data, and enables to perform original analysis and comparisons between different techniques. Applications for this dataset will impact many fields of volcanology and atmospheric physics, including but not restricted to volcanic clouds dispersal numerical modelling and volcanic aerosol impact on the atmosphere and climate. In fact, the collocation with GNSS RO will allow the study of the atmospheric structure with high vertical resolution.
Large-sample hydrology to foster open and collaborative research: a review of recent progress and grand challenges
Authors: Coxon Gemma , Addor Nans , Alvarez-Garreton Camila , Do Hong X. , Fowler Keirnan , Mendoza Pablo A.
Published: March 2020

Large-sample hydrology (LSH) relies on data from large sets (tens to thousands) of catchments to go beyond individual case studies and derive robust conclusions on hydrological processes and models and provide the foundation for improved understanding of the link between catchment characteristics, climate and hydrological responses. Numerous LSH datasets have recently been released, covering a wide range of regions and relying on increasingly diverse data sources to characterize catchment behaviour. These datasets offer novel opportunities for open hydrology, yet they are also limited by their lack of comparability, accessibility, uncertainty estimates and characterization of human impacts.

Here, we underscore the key role of LSH datasets in open hydrologic science and highlight their potential to enhance the transparency and reproducibility of hydrological studies.  We provide a review of current LSH datasets and identify their limitations, including the current difficulties of inter-dataset comparison and limited accessibility of hydrological observations. To overcome these limitations, we propose simple guidelines alongside long-term coordinated actions for the community, which aim to standardize and automatize the creation of LSH datasets worldwide. This presentation will highlight how, by producing and using common LSH datasets, the community can increase the comparability and reproducibility of hydrological research.

This research was performed as part of the Panta Rhei Working Group on large-sample hydrology and is based on https://doi.org/10.1080/02626667.2019.1683182.
Regional effects of synoptic situations on soil drought in the Czech Republic
Authors: Řehoř Jan , Brázdil Rudolf , Trnka Miroslav , Řezníčková Ladislava , Balek Jan , Možný Martin
Published: March 2020

Soil drought has an important influence on plant development. The SoilClim model was used to investigate episodes of soil drought with 10-year return periods at the 0–100-cm profile during the 1961–2017 period for four selected regions of the Czech Republic (North-western Bohemia, Southern Bohemia, North-eastern Moravia, and Southern Moravia). It emerged that the frequency of soil drought significantly increases in the summer half-year (SHY) and exhibits insignificant trends in the winter half-year (WHY). The dynamic climatology of soil drought is based herein upon synoptic situations as classified by the Czech Hydrometeorological Institute, in terms of which changes in the occurrence and precipitation intensity of drought episodes in the four individual regions were studied. Drought episodes are generally related to decreases in the frequency of precipitation-rich situations and in their precipitation intensity. This is particularly true of situations C (central cyclone over central Europe), B (trough over central Europe) and Bp (travelling trough). Situations B and Bp, together with south-west cyclonic situations SWc1-3, appeared as the most relevant to regional differences in drought episodes during SHY in the four regions studied, while western cyclonic situations (Wc and Wcs) emerged as particularly important in WHY. Regional differences are clearly marked between the Bohemian and Moravian regions, especially in SHY. Discussion of the results obtained concentrates on the uncertainty of soil drought data, differences between SHY and WHY, the effects of synoptic situations, and the broader context of soil droughts.
Constraining North Atlantic Igneous Province (NAIP) activity during the late Paleocene and early Eocene
Authors: Jones Morgan , Stokke Ella , Augland Lars , Pogge von Strandmann Philip , Liu Emma , Mather Tamsin , Rooney Alan , Tierney Jessica , Whiteside Jessica , Tegner Christian , Schultz Bo , Planke Sverre , Svensen Henrik
Published: March 2020

The close temporal correlation between the emplacement of large igneous provinces and environmental crises in the geological record suggests a causal relationship. One such example is the emplacement of the North Atlantic Igneous Province (NAIP) and the Paleocene-Eocene Thermal Maximum (PETM), an extreme climate change event that occurred ~56 Ma. The main pulse of activity from the NAIP is around this time, but current radioisotopic ages are too low-resolution to constrain whether this activity was before, during and/or after the PETM. An ideal locality for understanding the initiation and development of the PETM is the island of Fur, northwest Denmark. The sedimentary sequence consists of clays and diatomites deposited in an epicontinental, shallow marine sea. The high sedimentation rates and close proximity to the NAIP means there are numerous volcanic and climatic proxies in the strata that can be used to provide high-resolution records constraining the relative and absolute timings of these events.

Here we present the findings of the project ‘Ashlantic’, which focuses on pre- to post-PETM strata. We adopt a multiproxy approach using volcanic tracers, including tephra horizons, Hg anomalies, and Os isotopes, to infer the intensity and timing of NAIP activity. Volcanic glass morphology and chemistry suggests a hydromagmatic origin for key tephra intervals, while U-Pb dating of magmatic zircon constrains the timing of NAIP activity and the development of the PETM. Detailed chemostratigraphic logs and datasets (e.g. δ13C analyses) define the onset and duration of the PETM, while clay chemistry, Li isotopes, total organic carbon (TOC), and the paleothermometer TEX86 are used to assess the climate response to global warming during the PETM. In concert, our results suggest that the NAIP was active just before, during, and after the PETM, but the relationship between the NAIP and the marine and terrestrial environments is complex. These findings call for further work, such as ICDP and/or IODP drilling of North Sea sediments.
Systematic comparison of different numerical approaches for tsunami simulations at the Chilean coast as part of the RIESGOS project
Authors: Harig Sven , Zamora Natalia , Gubler Alejandra , Rakowsky Natalja
Published: March 2020

There is a growing number of numerical models for tsunami propagation and inundation available, based on different spatial discretizations and numerical approaches. Since simulations carried out with such models are used to generate warning products in an early warning context, it is crucial to investigate differences emerging from the chosen algorithms for simulation and warning product determination. Uncertainties regarding the source determination within the first minutes after a tsunami generation might be of major concern for an appropriate warning at the coast, still, the sensitivity of warning products with respect to pre-computed simulation database contents or on-the-fly calculations are of crucial importance as well.

In this study, we investigate the performance of three models (TsunAWI, HySEA, COMCOT) in the oceanic region offshore central and northern Chile with inundation studies in Valparaíso and Viña del Mar. The investigation forms part of the tsunami component in the RIESGOS project dealing more general with multi hazard assessments in the Andes region. The numerical implementation of the models include both a finite element approach with triangular meshes of variable resolution as well as finite difference implementations with nested grids for the coastal area. The tsunami sources are identical in all models and chosen from an ensemble of events used in an earlier probabilistic study of the region. Additionally, two historic events are considered as well to validate the models against the corresponding measurements.

We compare results in virtual gauges as well as actual tide gauge locations at the Chilean coast. Inundation areas are determined with high resolution and employing the model specific wetting and drying implementations. We compare the model results and sensitivities with respect to spatial resolution and parameters like bottom friction and bathymetry  representation in the varying mesh geometries.
Catalog of 3C rotations measured at the LSBB’s antenna.
Authors: Rusch Roxanne , Sebe Olivier , Décitre Jean-Baptiste , Gaffet Stéphane
Published: March 2020

Rotational seismology refers to the study of the 3 components of rotation that are part of the
seismic wave field equation (Aki and Richards, 2002). Using the Geodetic Method (GM)
[Spudich et al, 1995], that is, using spatial finite differences of the local ground motions, the
3C of rotations were calculated at the dense broadband seismic array of the LSBB (Low
background noise underground research Laboratory, France, http://lsbb.eu). A catalog of 3C
rotations was created by systematically applying this method to several seismic events. The
uncertainty of the rotation measurements has been estimated through a sensitivity analysis.
This catalog will be presented and illustrated using examples. The analysis of the rotational
motions relatively to the seismic events source’s properties will be discussed as well.
The effects of living roots and arbuscular mycorrhiza fungi (AMF) on soil N2O emissions
Authors: Shen Yawen , Xu Tianle , Zhu Biao
Published: March 2020

Living roots and arbuscular mycorrhiza fungi (AMF) are widespread in most terrestrial ecosystems and play an important role in ecosystem nitrogen (N) cycling. However, the influence of living roots and AMF on soil N2O emissions remains poorly understood. In this study, we conducted a pot experiment with ryegrass (Lolium perenne) growing in a greenhouse for three months with three factors: root and AMF presence (None or unplanted, Root or with roots, and Root+AMF or with roots colonized by AMF), two N addition levels (N0 and N1 with 0 and 50 mg N kg-1 soil) and two P addition levels (P0 and P1, with 0 and 20 mg P kg-1 soil).

 

Our results showed that N addition didn’t have significant effect on N2O emission, however, we detected significant effects of Root and Root+AMF, particularly under P addition. Though the colonization of AMF didn’t significantly influence N2O emission, the presence of roots (Root and AMF+Root treatments) deceased N2O emission by 58%-67% compared with the None treatment. P addition increased (+134%) N2O emission from unplanted soil but decreased (74%-98%) N2O emission under planted soil regardless of AMF colonization. Moreover, there were no significant relationship between N2O emission and soil pH, NH4+-N and net N mineralization. The lower N2O emission from rooted treatments were mainly due to the lower soil NO3--N (and MBN) content which might be immobilized by plant biomass, while the higher N2O emission from unplanted soil under P addition was attributed to increased soil available (r=0.760, P<0.01) and total (r=0.654, P<0.01) phosphorus content. We conclude that root presence and P addition played an important role in regulating N2O emission from P-limited soils.
Recurrence of historical drought events over the Iberian Peninsula in different observational datasets and reanalyses
Authors: Moemken Julia , Pinto Joaquim G.
Published: March 2020

Extreme climate events such as droughts can have very strong impacts both for society and the environment. In particular, the occurrence of severe droughts can endanger the balance of an ecosystem. While intact woodlands, e.g. the Iberian cork-oak ecosystem, are well adapted to withstand single severe drought events, both competition with invading species and recurrent droughts (i.e. droughts in consecutive years) may drive these systems towards critical limits. This is of crucial importance considering that the frequency, intensity and duration of extreme droughts are projected to increase in future decades in various regions all over the world, including the Mediterranean region.
We evaluate the occurrence and intensity of historical extreme drought events over the Iberian Peninsula for the past decades. Special focus is given to consecutive/recurrent drought events. Our study compares various indices for the identification of droughts, e.g. the SPEI (Standardized Precipitation Evapotranspiration Index), the SPI (Standardized Precipitation Index) or indices from the “Expert Team on Climate Change Detection and Indices” (ETCCDI). All indices are based on precipitation and/or temperature. We analyse different observational (E-OBS V17, V20, IBERIA01) and reanalysis datasets (ERA-Interim, ERA5) at several spatial resolutions, ranging roughly between 10 km and 25 km. The high resolution of the datasets enables the consideration of small-scale processes and local topographic effects which are relevant for extreme droughts, thus enabling a deeper insight on the physical mechanisms associated with droughts in the study area.
Sequential modelling of the Earth magnetic field
Authors: Lesur Vincent , Ropp Guillaume
Published: March 2020

Geomagnetic field models derived from satellite data cover now more than twenty years and are obtained through the processing and analyses of a massive amount of vector magnetic data. As our understanding of the geomagnetic field progresses, these models have to describe contributions of more and more sources with rather complex mathematical representation. In order to handle this increasing complexity and amount of available data, we use a sequential modelling approach (a Kalman filter), combined with a correlation based modelling step (Holschneider et al; 2016). In order to reach high temporal resolution for the core field, a sequence of snapshot models, 3-months apart, has been built. The main characteristics of the derived series of Gauss coefficients are the same as those of recently released field models based on classic modelling techniques. The results we obtained show the importance of a careful calibration of the Kalman prediction steps as well as applying Kalman smoother at the end of the modelling. We identify also the induced fields as the main limitation for an increase resolution of the core field. We will present how these induced fields have been handle in a recent version of the model and future steps to progress further in the representation of the different sources of the geomagnetic field.
A new furnace for improving thermal demagnetization in paleomagnetism
Authors: Qin Huafeng , Zhao Xiang , Liu Shuangchi , Paterson Greig , Jiang Zhaoxia , Cai Shuhui , Liu Qingsong , Zhu Rixiang
Published: March 2020

Thermal demagnetization furnaces are routine facilities for paleomagnetic studies. The ideal thermal demagnetizer should maintain “zero” magnetic field during thermal treatments. However, magnetic field noises, including residual magnetic fields of material and induced fields caused by the heating current in the furnace are always present. The key to making high-performance demagnetization furnace is to reduce the magnetic field noises. By combining efficient demagnetization of shielding and a new structure of heating wire, we have developed a new demagnetization furnace with low magnetic field noises. Repeated progressive thermal demagnetization experiments using specimens that were previously completely thermal demagnetized above their Curie temperature were carry out to explore the effects of field within various types of furnace during demagnetization. These experiment confirm that magnetic field noises in the furnace can have an observable and detrimental impact on demagnetization behavior. Comparison between commercial furnaces and our new design show a notable reduction in the impacts of on thermal demagnetization behavior. The new heating element design and procedure for reducing magnetic field noises represent a significant improvement in the design of thermal demagnetizers and allows for extremely weak specimens to be successfully measured.
Understanding the long-term concentration, flux, composition and processing of dissolved organic carbon in UK rivers
Authors: Worrall Fred , Howden Nicholas , Burt Timothy
Published: March 2020

Dissolved organic carbon (DOC) represents an important component of the terrestrial and fluvial carbon cycle as it represents a flux from terrestrial carbon stores and while it transfers through the fluvial network it can be processed to release greenhouse gases to the atmosphere. Furthermore, DOC is a major water resource limitation as the dissolved organic matter has to be removed prior to treatment. Therefore, we need to understand the concentration and fluxes of DOC and they change across a landscape between the terrestrial source and the tidal limit.

Our ability to understand the processing of terrestrial and fluvial carbon has been limited by the range of catchments that have been considered and the time scale over which they have been considered. Studies focused on similar catchment types and very little means of comparing between catchments. However, if we can access and understand large datasets we can find general principles which control DOC and the relative importance of these controls. In this study we use two datasets. The first, is a dataset sampled across the UK for major rivers (270 catchments) from 1974 and this dataset is ideal for understanding flux to the continental shelf and this dataset has over 50000 datapoints. Secondly, many of these sites are monitored for a rang e of other parameters that are related to the composition of the dissolved organic matter. The important covariates for DOM composition are BOD, which is a measure of DOM decomposition, and COD which is measure of the oxidation state of the DOM. All the study catchments could be characterised by a range of covariate information, eg. soil cover, land use, hydro-climatology. To make maximum use of this data the dataset was considered within a Bayesian hierarchical framework.

The concentrations of DOC from the UK rose for the 1974 on to the late 1990s before a decline to 2007-08. The decline was driven by changes in urban sources, particular by improvements in sewage treatment. The DOC flux from the UK has declined since a peak in 2000 and in 2017 was 767 ktonnes C/yr (95% credible interval 644 – 909 ktonnesC/yr). Modelling composition turnover gives the DOC flux from source as 3.5 Mtonnes C/yr with 2.6 Mtonnes C/yr lost to atmosphere (14 Mtonnes CO2eq/yr = 59 tonnes CO2eq/km2/yr).
Proton and electron fluxes in the plasma sheet transition region and their dependence on the solar wind parameters
Authors: Nikita Stepanov , Sergeev Viktor , Sormakov Dmitry , Dubyagin Stepan , Runov Andrey
Published: March 2020

Proton and electron spectra in the plasma sheet usually consist of spectral core and high energy tail. These two populations are formed by different processes, driven by the various combinations of the solar wind parameters.These processes include different time delays and may act differently on protons or electrons. In this work we evaluate empirically the magnitude and the time delay of the impact of different solar wind parameter combinations on the protons and electrons with energies (30-300 keV) and reveal the mechanisms behind these impacts. To do this we build a model of the fluxes at different energy channels in the transition region (nightside central plasma sheet between 6 and 15 Re) for the THEMIS spacecraft observations in 2007-2018. We use normalized values of solar wind parameter combinations (incl. speed, density, pressure, electric field, etc) as inputs of the model, with regression coefficients indicating their impact magnitudes. We investigate different time delays up to 16 hours. The model obtained shows that protons and electrons are controlled differently by solar wind parameters: dynamic pressure is important for protons, whereas solar wind speed and VBs are important for electrons. Larger time delays are required to describe higher energy electron fluxes.
Does stand age affect methane consumption of forest soil? A study in a chronosequence of sessile oak.
Authors: Bras Nicolas , Plain Caroline , Epron Daniel
Published: March 2020

Soils play an important role of atmospheric methane sink, consuming about 30 Tg year-1. Methane consumption is carried out by methanotrophic bacteria whose activity can be affected by different environmental factors. One of the most important factors that impact on methane consumption is the air-filled porosity of soil (AFP), which depends on its total porosity (P) and its water content (SWC). A high AFP enhances gas diffusion in soil, and therefore methane consumption. In forests, P is thought to increase with stand age because of soil decompaction by tree roots and SWC is thought to decrease because of a high evapotranspiration. Another factor that can affect methane consumption and thought to decrease with the aging of forest stands is mineral nitrogen (Nmin) and particularly ammonium that competes with methane for the active site of methane monooxygenase, thus reducing methane oxidation. However only few studies have addressed the effects of stand aging on soil methane consumption.

Our objective was to confirm the hypothesis that methane consumption by forest soil increases with stand age, in relation with an increase AFP and a decrease Nmin. We carried out this study in a chronosequence of 16 stands of sessile oak divided into six age classes (20-30, 40-60, 60-70, 85-90, 125-130 and 140-145). Three sampling campaigns were conducted in late summer 2018 and 2019 (periods of maximum AFP) and in early spring 2018 (period of minimum AFP). Soil methane consumption was measured by incubating the five first centimetres of soil cores at 20°C and by measuring the decrease of CH4 concentration in the incubation chamber with a laser-based CH4 analyser.

In contrast to our hypothesis, we did not find any significant effect of stand age on Nmin, P, SWC and AFP, nor on methane consumption. However, methane consumption was higher in stands with high values of AFP and low value of SWC, whatever their age. AFP, through differences in SWC, appeared to be the main driver of soil methane consumption in our study site, explaining both seasonal variations and variations among stands, that could not however be related to their age.
Impact of various soil hydraulic properties and water source-sink relations on plant rings formation and sizes under arid conditions
Authors: Katz Ofir , Herooty Yair , Bar (Kutiel) Pua , Yizhaq Hezi
Published: March 2020

In semi-arid and arid environments, clonal plants occasionally appear in ring patterns with a barren soil centre. There is a general agreement that this pattern forms when ramets grow radially, leaving a dead centre where the parent plant once was. Nevertheless, there is still some controversy over the nature of water source-sink relations in and around the rings, and the mechanism that drive the ring formation. We studied Asphodelus ramosus rings in two sites with different soil types (sand and loess) but comparable climate, in order to understand whether differences in soil hydraulic properties create different water source-sink relations and mechanisms that drive ring formation. We characterised soil hydraulic properties and dynamics along the rainy season and during the dry season, accompanied by measurements of soil texture and of belowground storage root biomass. We found that the nature of source-sink relations varies with soil type and properties. In sandy soils, water supply to ring perimeters is mainly from their centre. In loessial soils, water supply to ring perimeters is mainly from the surrounding matrix. Consequently, rings are larger in sandy soils than in loessial soils, in each case in order to optimise water source area. Therefore, studying the formation of rings and other vegetation spatial patterns should consider local soil properties and the possibility that similar patterns may emerge through various mechanisms.
New apatite fission track thermochronology data from the Siberian Permian-Triassic Traps
Authors: Bagdasaryan Tanya , Veselovskiy Roman , Myshenkova Maria , Zaitsev Viktor , Thomson Stuart , Latyshev Anton , Zakharov Vladimir
Published: March 2020

The thermal history of the Siberian platform has not been studied and only single thermochronological study is available now [Rosen et al., 2009]. According to high-precision U-Pb dating the main phase of magmatic activity of the Siberian Traps Large Igneous Province took place ~252.0-251.3 Ma [Kamo et al., 2003] and its duration didn’t exceed ~1 Myr. But according to Ar/Ar dating (~240 Ma) [Ivanov et al., 2013] the total duration of the Siberian Traps formation may be estimated as long as ~10 Myr. In addition, single apatite fission track (AFT) ages are approximately 222-185 Ma [Rosen et al., 2009].

We present the first results of AFT dating from the Guli pluton and computer modeling of its post-magmatic cooling, as well as some new AFT ages from other magmatic bodies within the Siberian platform. Based on these data we present the first model of the tectonothermal evolution of the Siberian platform in Mesozoic and Cenozoic.

The Guli massif is located within the Maymecha-Kotuy region of the Siberian Permian-Triassic Traps and is the world's largest alkaline-ultrabasic complex. Results of U-Pb dating of baddeleyite from the carbonatites – the latest intrusion phase – 250.2±0.3 Ma [Kamo et al., 2003] correspond to the time of massif’s crystallization.

AFT dating was conducted by an external detector method at the University of Arizona (Tucson). The fission track ages of the Guli are in the range of ~250-231 Ma with the mean standard error (1σ) ±34 Myr. In addition, we obtain five new AFT ages as well as U-Pb age obtained from different intrusive bodies within the Siberian platform: Kontayskaya intrusion, Odikhincha massif and Padunsky sill. All obtained AFT ages are in the range of 195-173 ±13 (1σ) Ma, which corresponds to the Early-Middle Jurassic. At the same time, the U-Pb LA-ICPMS age of apatite from Padunsky sill is 242±7 Ma.

Thermal history modeling using fission track age data and track lengths distribution was performed in HeFTy v.1.8.3. Based on the obtained results we consider the following model of tectonic-thermal evolution of the studied intrusive massifs: (1) the emplacement of intrusions ca. 250 Ma; (2) their burial under a thick sedimentary (volcanic?) cover; (3) regional exhumation and cooling below 110°C about 220-190 Ma.

The research was carried out with the support of RFBR (grants 18-35-20058 and 18-05-00590) and Programs of development of Lomonosov Moscow State University.
Fictitious Domain methods for simulating thermo-hydro-mechanical processes in fractures
Authors: von Planta Cyrill , Nestola Maria G.C. , Vogler Daniel , Zulian Patrick , Hassanjanikhoshkroud Nasibeh , Chen Xiaoqing , Saar Martin O. , Krause Rolf
Published: March 2020

Fictituous domain methods provide an promising way for simulating fluid structure interaction in fractures with complex geometries. The main characteristic of the method is that the solid and the fluid problem are simulated on different, non-matching meshes, with the solid being immersed into the fluid. The problems are coupled by L2 - projections, which transfer physical variables between the two computational domains and either the penalty, augmented Lagrangian or Lagrange multiplier method to represent the solid in the fluid. We show the evolution of our framework in the last three years, starting with benchmark problems such as Poiseulle flow, with successive extension to contact, fracture intersections and thermal coupling.
The impact of climate change decrease of winter precipitation on the water use efficiency and sustainability of a Mediterranean forest.
Authors: Sirigu Serena , Corona Roberto , Montaldo Nicola , Oren Ram , Soru Dora
Published: March 2020

Over the past century, climate change has been reflected in altered precipitation regimes worldwide.  Recently, Montaldo and Sarigu (2017) showed that Sardinia runoff decreased over the 1975-2010 period, with mean annual values 40% lower than the 1922-1974 period.

These trends will have dramatic consequences on basin water resources, therefore forests are frequently exposed to periods characterized by a reduced water availability that influences the evapotranspiration process (ET), the water use efficiency and could be also the main cause of tree mortality or change of tree spatial distribution and density.

The Marganai forest, located in South West Sardinia (Italy), is a Long-Term Ecosystem Research (LTER) Italian site and a European Site of Community Importance (Natura 2000) managed by FORESTAS. The vegetation is mainly composed by Quercus Ilex trees and the soil depth varies between 10 cm and 50 cm. Historical data are from 16 rain stations (1922-2018 period) over the entire area and data of runoff of the Fluminimaggiore basin (area of 83 km2) are available. From 1922 a persistent decrease trend of winter precipitation in that area (Mann-Kendall t of -0.26) impacted runoff, which decreased of 2.52 mm/y.

Future climate scenarios are selected from IPCC climate change scenarios. From the 12 Atmosphere-Ocean General Circulation Models (AOGCMs) of Flato et al. (2013), we selected theHadGEM2-AO that simulates reasonable approximation of observed past seasonal precipitation and air temperature changes (1976-2004 compared with 1951-1975) in Sardinia.Using a distributed ecohydrologic model and the HADGEM2-AO future climate (rainfall and air temperature ) scenarios we predict both hydrologic (soil moisture, runoff, ET) and vegetation dynamic (CO2, biomass, leaf area index and vegetation fraction) outputs.

The model has been successfully calibrated for runoff and ET estimation for the 1922 – 2018 period. Then, the eco-hydrological model, forced with the generated future scenarios, predict a significant change on tree leaf area index, with the reduction of tree density, spatial distribution, forest productivity and runoff. Future scenario predicting further decline is particularly alarming for the Marganai forest, requiring new strategies in both forestal and water resources planning and management.
Predicting water retention curves of fine texture soils from particle size distribution
Authors: Pollacco Joseph , Fernández-Gálvez Jesús , Carrick Sam
Published: March 2020

Indirect methods for estimating soil hydraulic properties from particle size distribution have been developed due to the difficulty in accurately determining soil hydraulic properties, and the fact that particle size distribution is one piece of basic soil physical information normally available. The similarity of the functions describing the cumulative distribution of particle size and pore size in the soil has been the basis for relating particle size distribution and the water retention function in the soil. Empirical and semi-physical models have been proposed, but these are based on strong assumptions that are not always valid. For example, soil particles are normally assumed to be spherical, with constant density regardless of their size; and the soil pore space has been described by an assembly of capillary tubes, or the pore space in the soil matrix is assumed to be arranged in a similar way regardless of particle size. However, in a natural soil the geometry of the pores may vary with the size of the particles, leading to a variable relation between particle radius and pore radius.

 

The current work is based on the hypothesis that the geometry of the pore size and the void ratio depends on the size of the soil particles, and that a physically based model can be generalised to predict the water retention curve from particle size distribution. The rearrangement of the soil particles is considered by introducing a mixing function that modulates the cumulative particle size distribution, while the total porosity is constrained by the saturated water content.

 

The model performance is evaluated by comparing the soil water retention curve derived from laboratory measurements with a mean Nash–Sutcliffe model efficiency a value of 0.92 and a standard deviation of 0.08. The model is valid for all soil types, not just those with a marginal clay fraction.
Identification of magnetosonic modes in Galactic turbulence
Authors: Yan Huirong
Published: March 2020

The multiphase nature of astrophysical environment and diversity of driving mechanisms give rise to spatial variation of turbulence properties. Nevertheless, the employed model of magneto-hydrodynamic turbulence is often oversimplified being assumed to be only Alfvenic due to a lack of observational evidence. Here we report the employment of our novel method, the signature from polarization analysis (SPA), on unveiling the plasma modes in interstellar turbulence. The method is based on the statistical properties of the Stokes parameters (I,Q,U) of the synchrotron radiation polarization. The application of SPA on the synchrotron polarization data from the Galactic medium has for the first time revealed that interstellar turbulence is magnetized with different plasma modes composition, pinpointing the necessity to account for plasma property of turbulence, which is neither hydrodynamic nor purely Alfvenic, but depends on local physical conditions, particularly the driving process. A highly promising research field is foreseen to unroll with ample results anticipated from the advanced analysis of high resolution synchrotron polarization data and multiple wavelength comparison, that will shed light on the role of turbulence in various physical processes.
Monitoring rapid permafrost thaw using elevation models generated from satellite radar interferometry
Authors: Bernhard Philipp , Zwieback Simon , Leinss Silvan , Hajnsek Irena
Published: March 2020

Vast areas of the Arctic host ice-rich permafrost, which is becoming increasingly vulnerable to terrain-altering thermokarst in a warming climate. Among the most rapid and dramatic changes are retrogressive thaw slumps. These slumps evolve by a retreat of the slump headwall during the summer months, making them detectable by comparing digital elevation models over time using the volumetric change as an indicator. Despite the availability of many topographic InSAR observations to generate digital elevation models, there is currently no method to map and analyze retrogressive thaw slumps. 
Here, we present and assess a method to detect and monitor thaw slumps using time-series of elevation models (DEMs), generated from single-pass InSAR observations, which have been acquired across the Arctic at high resolution since 2011 by the TanDEM-X satellite pair.  At least three observations over this timespan are available with a spatial resolution of about 12 meter and the height sensitivity of 0.5-2 meter. We first difference the generated digital elevation and detect significant elevation changes taking the uncertainty estimates of each elevation measurement into account. In the implementation of the processing chain we focused on making it as automated as much as possible to be able to cover large areas of the northern hemisphere. This includes detecting common problems with the data and apply appropriate algorithms to obtain DEMs with high accuracy. Additionally we implemented methods to deal with problematic features like wet-snow, vegetation and water bodies. After generating the DEMs we us DEM differencing followed by a blob detection and cluster algorithm to detect active thaw slumps. To improve the accuracy of our method we apply and compare different machine learning methods, namely a simple threshold method, a Random Forest and a Support-Vector-Machine. To estimate the accuracy of our method we use data from past studies as well as a classification based on optical satellite data.
The obtained locations of thaw slumps can be used as a starting point to extract important slump properties, like the headwall height and volumetric change, which are currently not available on regional scales. Additionally to the thaw slump detection, we show first results of the thaw slump property extraction for thaw slumps located in Northern Canada (Peel Plateau, Mackenzie River Delta, Banks Island, Ellesmere Island). 
Contrasting response of West and East Antarctic ice sheets to Glacial Isostatic Adjustment
Authors: Coulon Violaine , Bulthuis Kevin , Sun Sainan , Haubner Konstanze , Pattyn Frank
Published: March 2020

The Antarctic ice sheet (AIS) lies on a solid Earth that displays large spatial variations in rheological properties, with a thin lithosphere and low-viscosity upper mantle (weak Earth structure) beneath West Antarctica and an opposing structure beneath East Antarctica. This contrast is known to have a significant impact on ice-sheet grounding-line stability. Here, we embedded a modified glacial-isostatic ELRA model within an Antarctic ice sheet model that considers a weak Earth structure for West Antarctica supplemented with an approximation of gravitationally-consistent local sea-level changes. By taking advantage of the computational efficiency of this elementary GIA model, we assess in a probabilistic way the impact of uncertainties in the Antarctic viscoelastic properties on the response of the Antarctic ice sheet to future warming by using an ensemble of 2000 Monte Carlo simulations that span a range of plausible solid Earth structures for both West and East Antarctica.
We show that on multicentennial-to-millennial timescales, model projections that do not consider the dichotomy between East and West Antarctic solid Earth structures systematically overestimate the sea-level contribution from the Antarctic ice sheet because regional solid-Earth deformation plays a significant role in promoting the stability of the West Antarctic ice sheet (WAIS). However, WAIS collapse cannot be prevented under high-emissions climate scenarios. At longer timescales and under unabated climate forcing, future mass loss may be underestimated because in East Antarctica, GIA feedbacks have the potential to re-enforce the influence of the climate forcing as compared with a spatially-uniform GIA model. In this context, the AIS response might be an even larger source of uncertainty in projecting sea-level rise than previously thought, with the highest uncertainty arising from the East Antarctic ice sheet where the Aurora Basin is very GIA-dependent.
Disintegration of the marine based parts of the last Eurasian Ice Sheet
Authors: Sejrup Hans Petter , Hjelstuen Berit Oline , Esteves Mariana Ramos , Patton Henry , Winsborrow Monica , Andreassen Karin , Rasmussen Tine , Hubbard Alun
Published: March 2020

 The timing, rates and patterns of retreat of western sectors of the last Eurasian Ice Sheet (EurIS) are poorly constrained, hampered by limited observations from the marine domain. A better knowledge of the deglaciation of the NW European marine areas/continental margins is essential for efforts to understand the role of different controlling factors (such as ice streams, atmospheric and oceanic conditions, relative sea level, morphology and substrate) on the stability of the EurIS, and also for ice-sheet stability in general. Based on new and existing mapping of glacial landforms, together with a compilation of existing and recalibrated dates from the NW European shelf, a new reconstruction of the retreating EurIS between 20 and 14 ka BP will be presented. Our reconstruction suggests an initial modest withdrawal from maximum extent to c. 19 ka BP along the entire western marine-terminating margin. From 19ka the two major marine-terminating ice streams, in the Norwegian Channel and Bear Island Trough, begin to retreat/collapse. This destabilisation leads to rapid interior downdraw and the eventual unzipping of the British-Irish and Fennoscandian ice sheets at c. 18.5 ka BP, and the Barents-Kara and Fennoscandian ice sheets between 16 and 15 ka BP. Based on our new reconstruction and modelling results, the importance of factors controlling the nonsynchronous and rapid deglaciation of marine-based sectors and the implications for the stability of the ice sheet, will be discussed. The chronology and patterns of past marine deglaciations provide contextual insight into ice sheet instabilities and the mechanisms behind, underpinning the ongoing retreat of the Greenland and Antarctic ice sheets today.

 