bluuebunny/crossref_metadata_2025 huggingface dataset:
Geodynamic Evolution of Datça Basin Since the Pliocene
Authors: Sümer Ökmen , Şiş Fatih Seçkin , İnce Meryem Dilan , Özkaymak Çağlar , Tosun Levent , Uzel Bora , Stoica Marius , Langereis Cor , Kaymakci Nuretdin
Published: March 2020

The slab edge processes related to the subduction of the African slab along the Aegean-Cyprian trench, beneath Anatolia, played a significant role in Cenozoic extension in western Anatolia. The Datça Basin, which includes various Late Miocene depositional environments characterised by continental to marine transitions, is a WSW-ESE trending asymmetric depression developed on the Datça Peninsula, which separates the Aegean and Eastern Mediterranean Seas at the SW corner of Anatolia. Presently, the region is seismically active and is dominated by the E-W-trending Gökova Graben in the north and the NE-SW-trending Pliny-Strabo Trench in the south. Here, we conduct high resolution integrated stratigraphic study, that includes biostratigraphy, magnetostratigraphy as well as kinematic studies involving paleostress analysis to unravel geodynamic evolution of the region within the context of Africa-Eurasia convergence.  

 

Three prominent sequences separated by unconformities are recognised in the  Datça Basin; i) facies associations related to alluvial fan to fluvio-lacustrine deposits of Pliocene age, ii) facies extending from alluvial fan to fluvio-deltaic to marine incursions interlayered with two air-fall ash deposits of Pleistocene age, and iii) alluvial fan to fluvial to marine coastal facies of the modern basin infill. Integration of available information and our findings indicate that the basin experienced three distinct deformation phases associated with reactivation of pre-existing structures since Pliocene. First, the Datça Basin was initially developed as a transtensional basin in Pliocene possibly due to strike-slip deformation related to the Pliny-Strabo Trench, then orthogonal extensional deformation dominated and the basin evolved into a superimposed half-graben as a result of NNE to NNW directed extensional strain and subsequently became a full graben under N-S directed extension by the late Pliocene onwards.  

This research is supported by The Scientific and Technological Research Council of Turkey (TUBITAK) with Grant Number of 117R012.

Keywords: Integrated stratigraphy, kinematics, basin evolution, Datça Basin, Southwestern Anatolia
A stochastic rainfall model that can reproduce important rainfall properties across the timescales from several minutes to a decade
Authors: Kim Dongkyun , Onof Christian
Published: March 2020

We introduce a stochastic model reproducing various rainfall characteristics at timescales between 5 minutes and one decade. The model is composed of three moduels as follow: First, the model generates the fine-scale rainfall data based on a type of Bartlett-Lewis rectangular pulse model; Second, sequence of the generated rainstorms are shuffled so that their correlation structure can be preserved; Third, the time series is rearranged at the monthly timescale to reflect the coarse scale correlation structure. The method was tested based on the 69 years of 5-minute rainfall data of Bochum, Germany. The mean, variance, covariance, skewness, and proportion of wet/dry periods were well reproduced at the timescales from 5 minutes to a decade. The extreme values were also successfully reproduced at the timescales between 5 minutes and 3 days. The antecedent moisture condition before an extreme rainfall event was reproduced well too.
Aeolus: ESA’s wind mission. Status and future challenges
Authors: Parrinello Tommaso , Straume Anne Grete , Von Bismark Jonas , Bley Sebastian , Tran Viet Duc , Fischer Peggy , Kanitz Thomas , Wernham Denny , Fehr Thorsten , Alvarez Emilio , Reitebuch Oliver , Krisch Isabell
Published: March 2020

The European Space Agency (ESA)’s wind mission, Aeolus, was launched on 22 August 2018. Aeolus is a member of the ESA Earth Explorer family and its main objective is to demonstrate the potential of Doppler wind Lidars in space for improving weather forecast and to understand the role of atmospheric dynamics in climate variability. Aeolus carries a single instrument called ALADIN: a high sophisticated spectral resolution Doppler wind Lidar which operates at 355 which is the first of its kind to be flown in space. It provides profiles of single horizontal line-of-sight winds (primary product) in near-real-time (NRT), and profiles of atmospheric backscatter and extinction. The instrument samples the atmosphere from about 30 km down to the Earth’s surface, or down to optically thick clouds. The required precision of the wind observations is 1-2.5 m/s in the troposphere and 3-5 m/s in the stratosphere while the systematic error requirement be less than 0.7 m/s. The mission spin-off product includes information about aerosol and cloud layers. The satellite flies in a polar dusk/dawn orbit (6 am/pm local time), providing ~16 orbits per 24 hours with an orbit repeat cycle of 7 days. Global scientific payload data acquisition is guaranteed with the combined usage of Svalbard and Troll X-band receiving stations.

The status of the Aeolus mission will be provided, including its performance assessment, planned operations and exploitation in the near future. This comprises the outcome of the instrument in its early operation phase, calibration and validation activities and a general review of the main scientific findings. Scope of the paper is also to inform about the programmatic highlights and future challenges.
Transpolar Arc Observed by the Wide-Field Auroral Imager Onboard Fengyun Satellite
Authors: He Fei , Zhang Xiao-Xin , Yao Zhonghua , Wei Yong , Wan Weixing
Published: March 2020

Transpolar arcs that occur primarily under northward interplanetary magnetic field (IMF) are a class of auroral features in the polar cap region. Many mechanisms have been proposed to interpret the generation of the arcs, including reconnection and sudden change in the IMF. It is now generally accepted that IMF BYcomponent plays a key role in the generation and evolution of the arcs. Here we report an interesting long-lasting and moving transpolar arc observed during a geomagnetically quiet period (Dst<10 nT and AE<50 nT) by the wide-field auroral imager (WAI) onboard the Chinese Fengyun satellite. The WAI is a recently launched imager operated in far ultraviolet wavelength (LBH band in 140-180 nm) in a sun-synchronous orbit with a height of ~840 km. It is shown that the arc was initiated at the poleward auroral boundary on dawnside after the IMF turned to be northward and persisted for more than 5 hours. The arc moved toward the noon-midnight line as the IMF BYcomponent changed its direction and then moved back toward dawnside. An interesting phenomenon was that the arc was accompanied with strong energetic proton (30-80 keV) precipitations with geomagnetic latitude greater than 70° but no significant electron precipitations. However, the origin of these energetic protons is unknown and is worthy study in future.
Controlling factors and formation mechanism of fractures in the tight-gas sandstones of the Upper Triassic Xujiahe Formation, western Sichuan Basin, China
Authors: Lyu Wenya , Zeng Lianbo , Chen Shuangquan , Tang Lei , Zhang Yunzhao
Published: March 2020

Based on cores, image logs and thin sections, five sets of fractures are developed in the study area, where faults are developed. Most of fractures are open without fillings, and some fractures are filled with calcite, quartz, bitumen, pyrite and mud. Fractures are mainly controlled by lithology, mechanical stratigraphy and faults. Based on mutual crosscutting relationships of fractures, mineral filling sequence of fracture fillings, fluid inclusion and carbon-oxygen isotope analysis of calcite fillings in fractures, and quartz spintronic resonance analysis of quartz fillings in fractures, in combination with thermal and burial history, the formation sequence and time of fractures were analyzed. The results show that fractures mainly formed over three period, that is, the late Triassic, Middle to Late Jurassic, and Late Cretaceous to Paleogene. Then，combined with the paleostress evolution and fracture characteristics of the study area, the formation mechanism of fractures was discussed.
Geochemistry of geothermal fluids in Moil Valley geothermal field, NW Iran
Authors: Masoumi Rahim , Bakhshandeh GharehTapeh Farahnaz , Bakhshandeh GharehTapeh Bahman
Published: March 2020

The Moil valley geothermal field is located in the northwest of Sabalan volcano in the northwest of Iran. The geothermal activities attributed to the Sabalan volcano was intensified during Plio-Quaternary time and the manifestations of these activities are observable around the volcano especially in the northwestern corner. The hot springs, surficial manifestations, and extracted fluids from drilled wells represent the whole composition of underground reservoir fluids. The thermal measurement of fluids show wide ranges of temperature of fluids where the hottest spring show 89˚C and the fluids obtained from well samplings show maximum temperature of 202˚C.  

The reservoir temperature estimations based on different geothermometers show 250˚C for the reservoir. The interpretation of carried out chemical analyses represent Na-K-Cl dominant composition for the studies samples taken from hot springs and drilled wells. All of sampling stations show pH ranges of 4.2-7.6 which reveal acidic to neutral pH range. The variation of TDS for the studied samples ranges between 209 to 320 mg/L. The evaluation of correlation coefficients between main parameters gives notable results. The positive and good correlation coefficient between temperature and Cl is obvious in most of samples and consequently the Cl content of samples increases in high temperature samples.        

Boron as a key constituent in geothermal fluids show variable concentrations in Moil Valley geothermal fluids and shows 0.28-35 mg/L Boron content in the studied samples. The correlation between Boron and pH for the studied samples is positive. This correlation displays the highest concentrations in pH=7. The main Boron species in this pH value is B(OH)3 which is more stable comparing to the other Boron phases.  

The stable isotope analyses of the studied samples show -12 to -9.1‰ for δ18O and -71.3 to -77.6‰ for δD. The interpretation of obtained δ18O and δD values represents the main role of meteoric waters in reservoir fluids of Moil Valley geothermal field. Magmatic waters show negligible share of the reservoir fluids.      

The Tritium analyses for the studied samples show 0.1 to 41.7 TU amounts. The evaluation of obtained Tritium contents reveals the circulation of young waters inside the reservoir and considering to the δD/δ18O ratios, it is most likely that the recharge zones of the reservoir are situated in close distance and there are evidences of mixing with meteoric waters.
A coupled heat and moisture tracking framework to assess water cycle changes in a warming climate
Authors: Keune Jessica , Schumacher Dominik L. , Miralles Diego G.
Published: March 2020

The expected intensification of the global water cycle in a warming climate comes along with an increase in the frequency and intensity of extreme events, such as droughts and floods. From a drought perspective, local limitations of terrestrial evaporation can cause a reduction of water vapor in the atmosphere and thus further induce local and remote precipitation deficits. Despite the existing myriad of tools and models to assess the origin of precipitation, trends and uncertainties in such source–sink relationships remain largely unexplored. The main reason is the scarcity of observations to explore these relationships and validate moisture-tracking models, which are commonly subject to assumptions that limit their reliability and applicability. Lagrangian models, for example, typically establish source–sink relationships based on moisture changes along air parcel trajectories, yet tend to be heavily affected by numerical noise. Moreover, they do not assess the plausibility of a given moisture change by considering the increasing saturation point of air with increasing temperatures, which hampers reliable assessments of trends under global warming. 

Here, we present a holistic framework for the process-based evaluation of atmospheric trajectories to infer source–sink relationships of moisture. Building upon previous process-based evaluations of trajectories, we extend the analysis to a coupled heat and moisture diagnosis that includes physics-based limits for the detection of evaporation and precipitation from humidity changes along each trajectory. The framework comprises three steps: (i) the coupled moisture and heat diagnosis of fluxes from Lagrangian trajectories using multi-objective criteria, (ii) the attribution of sources following a mass- and energy-conserving algorithm, and (iii) the bias correction of diagnosed fluxes and the corresponding source–sink relationship. Applying this framework to simulations from the Lagrangian particle dispersion model FLEXPART, driven with ERA-Interim reanalysis data, allows us to quantify errors and uncertainties associated with the resulting source–sink relationships. A comparison to alternative methodologies illustrates the benefit of our coupled heat and moisture tracking approach. Moreover, the multivariate character of this framework paves the way for a cohesive assessment of the spatial dependencies that cause water cycle changes in a warming climate.
Rhizosphere hotspots: root hairs and warming control microbial efficiency, carbon utilization and energy production
Authors: Zhang Xuechen , Kuzyakov Yakov , Zang Huadong , Dippold Michaela A. , Shi Lingling , Spielvogel Sandra , Razavi Bahar S.
Published: March 2020

Among the factors controlling root exudation, root hair proliferation and warming strongly influence exudate release, microbial substrate utilization and enzyme activities. The interactions of these two factors are important but poorly known in the rhizosphere. To clarify these interactions, two maize varieties – a wild type with root hairs and a hairless mutant – were grown at 20 and 30 °C for 2 weeks. We applied a unique combination of zymography to localize hotspots of β-glucosidase with microcalorimetry and substrate-induced respiration from soil sampled in hotspots. This approach enabled monitoring exudate effects on microbial growth strategy, enzyme kinetics (Vmax and Km), heat release and CO2 production in the hotspots in response to warming.

Root hair effects on enzyme activity and efficiency were pronounced only at the elevated temperature: i) β-glucosidase activity of the wild type at 30 °C was higher than that of the hairless maize; ii) temperature shifted the microbial growth strategy, whereas root hairs (i.e. C input) promoted the fraction of growing microbial biomass; iii) Km and the activation energy for β-glucosidase under the hairless mutant was lower than that under wild maize. These results suggest that microorganisms inhabiting hotspots of the wild type synthesized more enzymes to fulfill their higher energy and nutrient demands than those of the hairless mutant. In contrast, at higher temperature the hairless maize produced an enzyme pool with higher efficiencies rather than higher enzyme production, enabling metabolic needs to be met at lower cost. These changes in enzyme kinetics and metabolic shifts confirmed evolutionary theory on tradeoffs of enzyme structure–function and thermal–substrate under warming at the soil hotspot level. We conclude that, if microbial and enzymatic activities are stimulated by more substrate input under warming, then this shift in the microbial community and in enzyme systems to a lower efficiency could offset C losses.
A new Moho depth model for Fennoscandia and surroundings
Authors: Abrehdary Majid , Sjöberg Lars
Published: March 2020

Seismic data are the preliminary information for investigating Earth’s interior structure. Since large parts of the world are not yet sufficiently covered by such data, products from Earth satellite gravity and altimetry missions can be used as complimentary for this purpose. This is particularly the case in most of the ocean areas, where seismic data are sparse. One important information of Earth’s interior is the crustal/Moho depth, which is widely mapped from seismic surveys. In this study, we aim at presenting a new Moho depth model from satellite altimetry derived gravity and seismic data in Fennoscandia and its surroundings using the Vening Meinesz-Moritz (VMM) model based on isostatic theory. To that end, the refined Bouguer gravity disturbance (reduced for gravity of topography, density heterogeneities related to bathymetry, ice, sediments, and other crustal components by applying so-called stripping gravity corrections) is corrected for so-called non-isostatic effects (NIEs) of nuisance gravity signals from mass anomalies below the crust due to crustal thickening/thinning, thermal expansion of the mantle, Delayed Glacial Isostatic Adjustment (DGIA) and plate flexure. As Fennoscandia is a key area for GIA research, we particularly investigate the DGIA effect on the gravity disturbance and Moho depth determination from gravity in this area. To do so, the DGIA effect is removed and restored from the NIEs prior to the application of the VMM formula. The numerical results show that the RMS difference of the Moho depth from the (mostly) seismic CRUST1.0 model is 3.6/4.3 km when the above strategy for removing the DGIA effect is/is not applied, respectively. Also, the mean value differences are 0.9 and 1.5 km, respectively. Hence, our study shows that our method of correcting for the DGIA effect on gravity disturbance is significant, resulting in individual changes in Moho depth up to several kilometres.
Reconstruction of cropland cover changes in the European part of Tsarist Russia from 1500 to 1914 based on historical documents
Authors: Zhao Zhilong , Fang Xiuqi , Ye Yu , Zhang Chengpeng , Zhang Diyang
Published: March 2020

To evaluate the climatic and ecological impacts of anthropogenic activities in global change research, it is essential to reconstruct historical land use and land cover change on regional and global scales. In this study, we reconstructed cropland areas for 54 provinces within the European part of Tsarist Russia (ETR) over the periods of 1500-1914 using historical data, including cropland area, population, grain consumption, and grain yield per unit area. The main results are as follows. (1) Total cropland areas and fractional cropland areas of ETR for 11 time sections (1500 AD, 1540 AD, 1585 AD, 1696 AD, 1719 AD, 1725 AD, 1763 AD, 1796 AD, 1856 AD, 1887 AD and 1914 AD) during 1500-1914 were reconstructed, respectively. The total cropland area of ETR increased from 4.26×104 km2 in 1500 AD to 147.40×104 km2 in 1914 AD. The fractional cropland area increased from 2.40% to 29.20%, and the per capita cropland area decreased from 2.58 ha to 1.13 ha during 1500-1914. (2) Cropland expanded from the central and southwest of ETR to the black soil region, surrounding area of the Volga River, Ukraine region, the new Russia region, and the vicinity of Ural for the increase and migration of population. While in the northern region of ETR, cropland area remained stable due to unfavorable climatic conditions throughout the study period. (3) In 1914 AD, the cropland area and fractional cropland area of each province varied from 0.16×104 km2 and 0.76% to 5.65×104 km2 and 76.68%, respectively. (4) The comparisons show that the cropland areas on the ETR in this study for 1500-1914 are higher than those of the HYDE 3.2 dataset. The main reason might come from the underestimation of per capita cropland areas in HYDE 3.2 dataset, which values remained about 1 ha from 1500 to 1920 in that dataset.
Ferruginous bioforms accumulations in deep marine environments: an approach to their origin and formation mechanisms in the Transitional Zone province of the Galician Continental Margin (NW Iberian Peninsula)
Authors: López-Pérez Ángel Enrique , Rubio Belén , Rey Daniel , Pinheiro Luís
Published: March 2020

Ferruginous tubular structures concretions are widely distributed over the seafloor surrounding the Gran Burato depression in the Transitional Zone (TZ) province of the Galician Continental Margin (NW Iberian Margin). These bioforms-like structures are created by iron oxides precipitations into the tube-dwelling macrozoobenthos as a result of Fe2+ upward diffusion and O2 ventilation and diffusion acting in the water-sediment interphase in a non-steady state early diagenesis. X-ray diffraction analyses display that goethite is the main mineralogical component of these bioforms-like structures. Furthermore, non-steady state diagenesis has been identified by several oxidations fronts recognised in three piston cores, reflecting that the redoxcline has not achieved the deeper equilibrium in the study area. Afterwards, these ferruginous tubes were eroded, remobilised and redistributed over the seabed by bottom currents. Ocean-floor observations show erosion and sea-bottom current structures as ripples, grooves, erratic blocks, accumulations of pteropods and carbonate crusts associated with hardgrounds. Sedimentation rates calculated in a piston core display very low values for the last 30 cal ka BP (mean of 1.57 cm ky−1) with a marked hiatus between 17.80 to 10.45 cal ka BP, meanwhile abraded surfaces have been identified by high-resolution seismic data confirming erosional processes in this area of the TZ province. We conclude that the ferruginous bioforms accumulation over the deep-ocean floor is indicative of a present-day vigorous seafloor current acting and eroding the sediments of the TZ province. This bottom current is a direct consequence of the general seafloor elevation of the TZ province that causes constriction of the water masses (MOW and LSW) that induces a general intensification of the bottom currents and greater erosional capacity. This erosional process causes the continuous oxygenation of the upper sediments, and it prevents to reach the steady-state diagenesis, playing this fact an essential role in the ferruginous formations and accumulations in the study area.
Mechanics and paleo geomorphy of the platform margin of Dengying formation in the Jiulongshan field, Sichuan Basin, China
Authors: Wang Lining
Published: March 2020

The northwestern Sichuan region experienced the evolutionary process of a marine Craton basin in the Sinian-Middle Triassic and a continental basin in the Mesozoic-Cenozoic. Several regional tectonic activities cause the complicated stratigraphic distribution and structural deformations in deep layers. During key tectonic periods, the characteristic sedimentary and deformation structures were formed, including the platform margin of Dengying formation, the western palaeohigh at the end of Silurian, and the passive continental margin of late Paleozoic-middle Triassic. The Meso-Cenozoic intra-continental compressional tectonic processes since the late Triassic controlled the formation of complex thrusting structures surrounding and inside the basin. The northern Longmenshan fold-thrust belt has footwall in-situ thrust structures, controlled by two sets of detachments in the Lower Triassic and the Lower Cambrian, presenting a multi-level deformation structure with shallow folds, the middle thin-skin thrusts and the deeper basement-involved folds. From the perspective of structural geology, the Dengying formation of the Upper Sinian is mainly distributed in the eastern and northern areas of the northwest Sichuan basin where the Jiulongshan fold is the favorable exploration belts. Using the three-dimensional seismic reflection data, we recognize the structural characteristics of the platform margin of Dengying formation. Meanwhile, we apply new methods of two-dimensional and structural restoration based on mechanical constrains to gain insights into the development of the Jiulongshan anticline which forms the trap for the Jiulongshan field. The result of structural restoration indicates that, the formation of the Jiulongshan anticline is controlled by two-stage contractional thrusts. In the early days, there was no significant relief in Jiulongshan area, and the southwestern top of the Sinian Dengying formation was the paleo-high. The anticline was gradually formed in the Late Jurassic-the Early Cretaceous, presenting an approximately E-W strike structure. This structure was transformed by the N-E contractional stress to become an anticline in NE-SW direction.

 
A structure-preserving approximation of the discrete split rotating shallow water equations
Authors: Bauer Werner , Behrens Jörn , Cotter Colin J.
Published: March 2020

We introduce an efficient split finite element (FE) discretization of a y-independent (slice) model of the rotating shallow water equations. The study of this slice model provides insight towards developing schemes for the full 2D case. Using the split Hamiltonian FE framework [1,2], we result in structure-preserving discretizations that are split into topological prognostic and metric-dependent closure equations. This splitting also accounts for the schemes' properties: the Poisson bracket is responsible for conserving energy (Hamiltonian) as well as mass, potential vorticity and enstrophy (Casimirs), independently from the realizations of the metric closure equations. The latter, in turn, determine accuracy, stability, convergence and discrete dispersion properties. We exploit this splitting to introduce structure-preserving approximations of the mass matrices in the metric equations avoiding to solve linear systems. We obtain a fully structure-preserving scheme with increased efficiency by a factor of two.

References

[1] Bauer, W. and Behrens, J. [2018], A structure-preserving split finite element discretization of the split wave equations, Applied Mathematics and Computation, 325, 375--400.

[2] Bauer, W., Behrens, J., Cotter, C.J. [2019], A structure-preserving split finite element discretization of the rotating shallow water equations in split Hamiltonian form, preprint: http://arxiv.org/abs/1912.10335.
Numerical study of heat transfer across rough fracture surfaces
Authors: Heinze Thomas
Published: March 2020

Maximizing heat exploitation in geothermal systems is crucial for the economic efficiency of many geothermal systems. As the hydraulic flow in most geothermal systems is primarily due to fracture flow, heat transfer processes along the fracture surfaces are essential. However, while flow and mass transport in a single fracture have been studied experimentally and theoretically to a great extent, heat transfer processes have been rarely investigated. Laboratory experiments show the influence of the fracture surface morphology on flow and heat transfer processes, though a physical interpretation has been missing so far. Further, in many geothermal systems but also in many natural hydrothermal systems, the solid and fluid phases are not in local thermal equilibrium. Parameterization of local thermal non-equilibrium models was originally developed for porous media and adoptions to fractures have been cumbersome. In this work, I present a numerical study on heat transfer processes across rough fracture surfaces. Using a three-dimensional steady-state flow model, heat transfer across the fracture surface is studied for both scenarios: assuming and neglecting a thermal equilibrium across phase boundaries. Also, separate fracture morphologies have been studied using natural sandstone probes as well as synthetically generated fractures. The numerical simulations results are compared to laboratory experiments using artificially generated and 3D-printed fracture surfaces of various fracture morphologies for code validation. The full three-dimensional simulations reveal the role of flow channeling effects on the heat transfer taking place along rough surfaces, which is not captured by simulations with reduced spatial dimensions. The simulations results suggest a re-examination of the effective heat transfer coefficient for fractured reservoirs under local thermal non-equilibrium conditions incorporating characteristics of fracture morphology. The simulations results can also be linked to thermal stress generation and possibly explaining the deformations of fracture surfaces observed in the laboratory. However, parameterization of surface roughness is neither distinct nor trivial. Various parameters exist, such as the joint roughness coefficient, Hurst exponent or statistical descriptions, but none has been successfully linked to flow, transport or transfer characteristics. Relating fracture morphology with results of numerical simulations and laboratory findings regarding transfer and transport processes indicate a shortfall of conventional roughness parameterizations to sufficiently describe the observed variation in heat transfer parameters.
Climate controlled catchment erosion in the Himalaya during the late Quaternary
Authors: Amir Mohd , Tarique Mohd , Rahaman Waliur , Paul Debajyoti
Published: March 2020

The alluvial sediments deposited in the Indo-Gangetic Plains originated as a result of tectonic and climatic factors controlling the exhumation and erosion of the Hinterland Himalaya. However, erosion distribution over the Himalaya and sediment delivery to the plains, on a shorter millennial time scale, are primarily controlled by the climatic factors such as glacial cover over the Himalaya and intensity of Indian summer monsoon (ISM) precipitation. Therefore, these alluvial sediment archives record important information about the past climatic changes. Here, we report the geochemical record of 87Sr/86Sr, 143Nd/144Nd (εNd), and δ13C of sediment organic matter (δ13CSOM) in a ~45 m long drill-sediment core collected from a buried channel of the paleo-Yamuna River in the northwest Indo-Gangetic Plains, Haryana to infer variations in provenance, paleoclimate, and paleovegetation during the late Quaternary. The Sr–Nd isotopic compositions (87Sr/86Sr: 0.75144–0.79241, εNd: –15.9 to –19.7) of the core sediments suggest their derivation from isotopically distinct Higher Himalaya and Lesser Himalaya end-member sources in the catchment. Down-core variability in the isotopic compositions show increased contribution from the Higher Himalaya during marine isotope stage (MIS) 1 and late MIS 3 interglacial periods due to receding glacial cover and intense ISM. The δ13CSOM values (−21.6‰ to −27.0‰, average: −25.6‰) in the core samples imply a C3 dominant paleovegetation in the catchment. Down-core variability in the δ13CSOM exhibits significant correlation with the ISM precipitation intensity, implying an increased abundance of C4 plant in response to the ISM intensification during MIS 1, and early and late MIS 3.
Forward-inverse modeling based on scalar and vector radiative transfer models for coupled atmosphere-surface systems and machine learning tools
Authors: Stamnes Knut , Hamre Børge , Stamnes Snorre , Chen Nan , Fan Yongzhen , Li Wei , Lin Zhenyi , Stamnes Jakob
Published: March 2020

Reliable retrieval of atmospheric and surface properties from sensors deployed on satellite platforms rely on accurate simulations of the electromagnetic (EM) signal measured by such sensors. A forward radiative transfer (RT) model of the coupled atmosphere-surface system can be used to simulate how the EM signal responds to changes in atmospheric and surface properties. Realistic RT modeling is a prerequisite for solving the inverse problem, i.e. to infer atmospheric and surface parameters from the EM signals measured at the top of the atmosphere. The surface may consist of a soil-plant canopy, a snow/ice covered surface or an open water body (ocean, lake, river system). An overview will be provided of forward and inverse RT in such coupled atmosphere-surface systems. A coupled system consisting of two adjacent slabs separated by an interface across which the refractive index changes abruptly from its value in air to that in water /ice [1] will be used as an example. Several examples of how to formulate and solve inverse problems involving coupled atmosphere-water systems [2] will be provided to illustrate how solutions to the RT equation can be used as a forward model to solve practical inverse problems. Cloud screening [3], atmospheric correction [4], treatment of two-dimensional surface roughness, Earth curvature effects, and ocean bottom reflection for shallow water in coastal areas will be discussed, and the advantage of using powerful machine learning techniques to solve the inverse problem will be emphasized.

References

[1] Stamnes, K., and J. J. Stamnes, Radiative Transfer in Coupled Environmental Systems, , 2015.

[2] Stamnes, K., B. Hamre, S. Stamnes, N. Chen, Y. Fan, W. Li, Z. Lin, and J. J. Stamnes, Progress in forward-inverse modeling based on radiative transfer tools for coupled atmosphere-snow/ice-ocean systems: A review and description of the AccuRT model, , 8, 2682, 2018.

[3] Chen N., W. Li, C. Gatebe, T. Tanikawa, M. Hori, R. Shimada; T. Aoki, and K. Stamnes, New cloud mask algorithm based on machine learning methods and radiative transfer simulations, , 219, 62-71, 2018.

[4] Fan, Y., W. Li, C. K. Gatebe, C. Jamet, G. Zibordi, T. Schroeder, and K. Stamnes, Atmospheric correction and aerosol retrieval over coastal waters using multilayer neural networks, , 199, 218-240, 2017.
A drone-borne contactless method to jointly estimate discharge and Manning’s roughness in rivers
Authors: Bandini Filippo , Lüthi Beat , Peña-Haro Salvador , Bauer-Gottwein Peter
Published: March 2020

Unmanned Aerial Systems (UASs) can monitor streams and rivers also in remote, inaccessible locations during extreme hydrological events. Image cross-correlation analysis techniques, such as Particle Image Velocimetry (PIV), applied to videos acquired using UASs can provide estimates of water surface velocity (WSV) in rivers. However, estimation of discharge from WSV is not trivial: it requires water depth and the mean vertical velocity (Um). Scientific studies show that Um is generally between 70% and 90% of WSV; however, an accurate estimation of Um from WSV requires assumptions on the full vertical velocity profile. We developed a new method for estimating WSV applying PIV techniques on UAS-borne videos. This method does not require any Ground Control Point (GCP), because the conversion of the velocity field from pixels into meters is performed by using a camera pinhole model where the distance from the pin-hole to the water surface is measured by an on-board radar altimeter. For approximately uniform flow conditions, Um becomes a function of Gauckler–Manning–Strickler roughness coefficient (Ks) and WSV. Our method can be used to jointly estimate Ks and discharge by informing a non-linear system of 2 equations and 2 unknowns (Ks and discharge): i) Manning equation ii) mid-section method equation for computing discharge from Um, which is a function of WSV and ks. This approach merely relies on bathymetry knowledge, on UAV-borne measurements of WSV and water surface slope.  Our approach was extensively validated in 27 case studies, in multiple Danish streams with different hydraulic conditions. Compared to discharge measured with a multi-depth electromagnetic velocity probe, PIV-estimates of discharge showed a mean absolute error of 18% and a mean bias error of -9%. The underestimation of discharge is caused by inaccuracies in WSV, by deviations from the uniform flow assumption and by the assumption of constant Ks coefficient for the entire cross section.
Surface mass balance modeling of mountain glaciers in the Caucasus and in the High Mountain Asia
Authors: Rybak Oleg , Rybak Elena , Popovnin Victor , Gubanov Afanasy , Satylkanov Rysbek , Shahgedanova Maria , Kapitsa Vassiliy
Published: March 2020

 

            The most significant quantity characterizing current state of a mountain glacier is its surface mass balance (SMB). SMB responds to changing climatic conditions and therefore determines present and future behavior of the glacier. Formulation of SMB in terms of a mathematical model allows better understanding complex processes of the atmospheric impact on glacier dynamics. After several decades of development, common universal modeling principles and approaches have been elaborated. At present, most of the newly developed models are quite similar with only varying details mostly concerning parameterization of heat fluxes.

SMB is an interplay between positive (accumulation) and negative (ablation) components. Ablation is formulated either using temperature-index (positive degree day) approach or surface energy balance calculation (or combination of both). Both these approaches are based on genuine physical principles and that is why they can be easily transformed into computational algorithms. Results of ablation model calculations are relatively easily constrained by observations. In contrast, evaluation of accumulation is much more dependent on poorly constrained factors such as local atmospheric circulation, snow-storm transport (including post-depositional) and avalanche feeding.

Our approach to simulate components of SMB is based on energy balance approach and emulation of meteorological conditions using a simple stochastic weather generator. To validate the model, we use observed SMB data from several mountain glaciers in different environmental conditions – Djankuat (Central Caucasus), Tuyuksu (Zailiyski Alatau), Sary-Tor and Karabatkak (Inner Tien Shan). Suggested approach allows to easily construct an ensemble of numerical experiments and implement Monte Carlo method for the SMB evaluation. This possibility is especially significant for simulation of future states of glaciers according to one or another climatic scenario on a coupled ice flow-SMB model.

The reported study was funded by RFBR, project number 20-05-00681 (“Evolution of glaciation of Inner Tien Shan under climate change and technogenic influence”)
Low-frequency seismic properties of olivine-orthopyroxene mixtures
Authors: Qu Tongzhang , Jackson Ian , Faul Ulrich
Published: March 2020

Although the seismic properties of polycrystalline olivine have been the subject of systematic and comprehensive study at seismic frequencies, the role of orthopyroxene as the major secondary phase in the shallow parts of the Earth’s upper mantle has so far received little attention. Accordingly, we have newly prepared synthetic melt-free polycrystalline specimens containing different proportions of olivine (Ol, Fo90) and orthopyroxene (Opx, En90) by the solution-gelation method. The resulting specimens, ranging in composition between Ol95Opx5 and Ol5Opx95 composition, were mechanically tested by torsional forced oscillation at temperatures of 1200 ºC to 400 ºC accessed during staged cooling under a confining pressure of 200 MPa. The microstructures of tested specimens were evaluated by BSE, EBSD and TEM. The forced-oscillation data, i.e. shear modulus and associated strain-energy dissipation at 1-1000 s period, were closely fitted by a model based on an extended Burgers-type creep function. This model was also required to fit data from previous ultrasonic and Brillouin spectroscopic measurements at ns-µs periods. Within the observational window (1-1000 s), the shear modulus and dissipation vary monotonically with period and temperature for each of the tested specimens, which is broadly comparable with that previously reported for olivine-only samples. There is no evidence of the superimposed dissipation peak reported by Sundberg and Cooper (2010) for an Ol60Opx40 specimen prepared from natural precursor materials and containing a melt fraction of 1.5%. The higher orthopyroxene concentrations are associated with systematically somewhat lower levels of dissipation and corresponding weaker modulus dispersion. The new findings suggest that the olivine-based model for high-temperature viscoelasticity in upper-mantle olivine requires only modest modification to accommodate the role of orthopyroxene, including appropriate compositional dependence of the unrelaxed modulus and its temperature derivative.
Crustal magnetic field advection on Mars from MAVEN observations
Authors: de Oliveira Isabela , Fränz Markus , Franco Adriane , Echer Ezequiel
Published: March 2020

The plasma environment of Mars is highly influenced by regions of remnant magnetism in the planetary crust, above which mini-magnetospheres are created. In this work, we study whether the ionospheric plasma flow can move crustal magnetic field lines, by the process of advection. According to this hypothesis, the magnetic field lines are dragged away in anti-solar direction, westward at dawn and eastward at dusk-side, due to the day-to-night flow of the ionospheric plasma. The altitude of interest is between 200 km and 1000 km, because the plasma flow velocity is significant in this region.

MAVEN (Mars Atmosphere and Volatile EvolutioN) data is used for a direct comparison between magnetic field data and a crustal magnetic field model. The difference between the observed and the model field at each point of the grid is a measure of the sum of the induced day magnetic field and the possible displacement of the crustal field lines by advection. The results of the analysis show that, except for the lowest altitude range, minimum value of this difference is always observed for westward shift at dawn-side and eastward shift at dusk-side, in agreement with the expected motion of the crustal magnetic field lines.

For a general idea of the relative forces between the moving plasma and the crustal fields, we use MAVEN data to analyze the pressures involved in the advection process. These are the dynamic pressure of the ionospheric plasma flow, the magnetic pressure of the field lines and the thermal pressure of the plasma related to the mini-magnetospheres. The balance between these quantities should dictate the occurrence of advection. This analysis suggests that advection could take place at low altitude (up to ~450 km) dawn-side regions above low intensity magnetic fields.

Although the global analysis results showed agreement with our hypothesis, we could not observe evidence of advection from the local observations in order to unambiguously prove the occurrence of this process. Future works include the investigation of single orbit data in regions of low intensity magnetic field, especially at dawn-side, and also magnetohydrodynamic modeling of the process using the plasma conditions prevalent in the Martian ionosphere.
Preliminary report on the sedimentary record of SCORE Site C9035 of Tokai, Nankai Trough, southwest Japan
Authors: Hsiung Kan-Hsi , Kanamatsu Toshiya , Ikehara Ken , Miura Io , Ashi Juichiro , Kodaira Shuichi , Arai Kohsaku , Okutsu Natsumi , Aoike Kan
Published: March 2020

Chikyu Shallow Core Program (SCORE) is a short and shallow ocean drilling program arranged by Japan Drilling Earth Science Consortium (J-DESC), Japan. SCORE provides opportunities for scientific ocean drilling test and project which can complete in a short period of time by using the ocean drilling vessel D/V Chikyu except for IODP expedition period. The title of this project is “Enigmatic recurrence pattern of Tokai earthquake in Nankai Trough, southwest Japan: the link between great earthquakes and ridge subduction”. The objective of our program is to investigate the past earthquake occurrence from a continuous sedimentary sequence at a local tectonic basin (i.e., Kanasunose Trough) in Nankai Trough. The target of this drilling program is to find an enigmatic recurrence pattern of Tokai earthquake in Nankai Trough, southwest Japan. Hydraulic Piston Coring System (HPCS) of the ocean drilling vessel (D/V) Chikyu can provide an opportunity to obtain an excellent long and continuous sedimentary record to unravel the earthquake recurrence pattern of this study area.

 

Expedition 912 was conducted by D/V Chikyu sailing from Shimizu to Sasebo, Japan from 4 January - 15 January 2020. The Leg 1 of Expedition 912 was cored Hole A and B in Site C9035 which are located in 34°05.7’N, 138°08.03’E with 2442 meters of water depth in the Kanasunose Trough, Tokai, Nankai Trough. The Penetration depth at site C9035 is 80.19 meters with HPCS drilled from 5 January to 8 January 2020. The thickness of Hole C9035A sediments was 9.5 m with a recovery of 105%. The thickness of cored sediments was 80.19 meters at Hole C9035B, with a recovery of 104.7%. The shipboard measurements of whole-round core samples involved X-ray CT scan and Physical properties. After splitting, the visual core description (VCD), smear slides, split surface image, Natural Remanent Magnetisation (NRM), penetration strength, and moisture and density (MAD) measurements, and Vane shear test were conducted.

 

The sedimentary succession is dominated by silty sediments with numerous coarse-grained (coarse silt–very fine sand) layers and some volcanic ash layers and spots. Two lithological units (Unit I and II) can be distinguished on the basis of sedimentary facies. Unit I consists of bioturbated silt and layered coarse silt–very fine sand with massive silt. Three ashes can be founded in Unit I and will provide good age control. Unit II is characterized by matrix-supported gravelly mud–muddy gravel and angular mudstone gravel. After measurements, the extended work of the recurrence intervals of seismo-turbidite in geological time will be built to stimulate the link between great earthquakes and ridge subduction.
Internal Solitary Waves with shear: beyond DJL theory
Authors: Stastna Marek , Coutino Aaron , Walter Ryan
Published: March 2020

While background shear is ubiquitous in the natural environment, the vast majority of theoretical and numerical studies of internal solitary waves do not include a background shear.  Walter et al 2016, Continental Shelf Research reported on measurements in Monterey Bay in which large amplitude internal solitary wave trains were observed but corresponding waves could not be computed from DJL theory due to the strength of the background shear.  In this talk I will revisit this issue using a classical stratified adjustment set up.  For the case of an exponential, surface trapped background current I will demonstrate that internal solitary wave trains with and without trapped cores coexist with a substantial region dominated by stratified shear instability and/or Rayleigh Taylor instability.  I will then demonstrate the type of internal wave train that results in cases when the the variational formulation of the DJL equation fails to converge. I will speculate on implications for theoretical description of such waves and for more realistic simulations in the coastal ocean.
Observed energy cascade from internal solitary waves to turbulence via near N-waves in the ocean
Authors: Zhang Xiaojiang , Zhang Weimin , Wang Huizan , Zhang Ren
Published: March 2020

High temporal resolution mooring observations reported here revealed that there exist energy cascades from internal solitary wave (ISW) to turbulent mixing via smaller, high-frequency internal waves near the maximum local buoyancy frequency (near N-waves), which are transient, inhomogeneous in space. These near N-waves, riding on the parent ISW, emerged at the trough and gradually extended to the rear face of ISW with their ampltiudes becoming larger and larger. Most of the enlargement occurred in the primary stratifed layer, where the displacements between the density surfaces are largest. The near N-waves riding on a typical ISW held approximately 5 percent of the energy of ISW during its passage. Simulations of the KdV-Burgers equation confirmed the emergence of the near N-waves due to the energy cascade, similar as in the observation. The above results point out a new route of energy cascade from ISWs to turbulence in the ocean, which would be helpful on deepening the understanding of the mechanism of wave-induced mixing and energy cascade in internal waves.