bluuebunny/crossref_metadata_2025 huggingface dataset:
Scientific workflow scheduling based on data transformation graph for remote sensing application
Authors: tian Zhuojing , huang Zhenchun , zhang Yinong , zhao Yanwei , fu En , wang Shuying
Published: March 2021

Abstract: As the amount of data and computation of scientific workflow applications continue to grow, distributed and heterogeneous computing infrastructures such as inter-cloud environments provide this type of application with a great number of computing resources to meet corresponding needs. In the inter-cloud environment, how to effectively map tasks to cloud service providers to meet QoS(quality of service) constraints based on user requirements has become an important research direction. Remote sensing applications need to process terabytes of data each time, however frequent and huge data transmission across the cloud will bring huge performance bottlenecks for execution, and seriously affect the result of QoS constraints such as makespan and cost. Using a data transformation graph(DTG) to study the data transfer process of global drought detection application, the specific optimization strategy is obtained based on the characteristics of application and environment, and according to this, one inter-cloud workflow scheduling method based on genetic algorithm is proposed, under the condition of satisfying the user’s QoS constraints, the makespan the cost can be minimized. The experimental results show that compared with the standard genetic algorithm, random algorithm, random algorithm, and round-robin algorithm, the optimized genetic algorithm can greatly improve the scheduling performance of data computation-intensive scientific workflows such as remote sensing applications and reduce the impact of performance bottlenecks.

Keywords: scientific workflow scheduling; inter-cloud environment; remote sensing application; data transformation graph;
Inferring mantle viscosity through data assimilation of relative sea level observations in a glacial isostatic adjustment model
Authors: Schachtschneider Reyko , Saynisch-Wagner Jan , Klemann Volker , Bagge Meike , Thomas Maik
Published: March 2021

We suggest to apply data assimilation in glacial isostatic adjustment (GIA) to constrain the mantle viscosity structure based on sea level observations. We apply the Parallel Data Assimilation Framework (PDAF) to assimilate sea level data into the time-domain spectral-finite element code VILMA in order to obtain better estimates of the mantle viscosity structure. In a first step, we reduce to a spherically symmetric earth structure and prescribe the glaciation history. A particle filter is used to propagate an ensemble of models in time. At epochs when observations are available, each particle's performance is estimated and the particles are resampled based on their performance to form a new ensemble that better resembles the true viscosity distribution.

Using this algorithm, we show the ability to recover mantle viscosities from a set of synthetic relative sea level observations. Those synthetic observations are obtained from a reference run with a given viscosity structure that defines the target viscosity values in our experiments. The viscosity estimation is applied to a three-layer model with an elastic lithosphere and two mantle layers, and to a multi-layer model with a smoother viscosity profile. We use various subsets of realistic observation locations (e.g. only observations from Fennoscandia) and show that it is possible to obtain the target viscosity values in those cases. We also vary the time from which observations are available to evolve the test cases towards a realistic scenario for the availability of relative sea level observations. The most relevant cases start at 26.5ka BP and at 10ka BP as they mark the beginning of the maximum glaciation and the end of deglaciation with a larger amount of observations following, respectively, and end at present day.
Assessing the impact of land-use change for solar park development in the UK: implications for biodiversity and ecosystem services
Authors: Carvalho Fabio , Armstrong Alona , Ashby Mark , Howell Belinda , Montag Hannah , Parker Guy , Cruz Joana , White Piran , Smart Simon
Published: March 2021

According to the latest IPCC report, 70 to 85% of electricity generation worldwide will need to come from renewable sources of energy by 2050 if countries are to meet internationally agreed greenhouse gas emissions targets. In the rush to decarbonise energy supplies to meet such targets, solar parks (SPs) have proliferated around the world, with uncertain implications for the biodiversity and ecosystem service (ES) provision of hosting ecosystems. SPs necessitate significant land-use change that could disproportionately affect the local environment compared to other low-carbon sources.

In Britain, SPs are commonly built on intensive arable land and managed as grasslands. This offers both risks and opportunities for ecosystem health, yet evidence for assessing ecosystem consequences is scarce. Therefore, there is an urgent need to understand how net environmental gains can be integrated into land-use change for solar energy development to address the current biodiversity and climate crises.

We used vegetation data from over 70 SPs and 50 countryside survey plots (1 km2) in England and Wales to assess the effects of land-use change for SPs on plant diversity and ES provision. We assessed ten habitat indicator variables (e.g., species richness, larval food plants, forage grasses, bird food plants) associated to functionally important plant species that have the potential to enhance ecosystem service delivery.

SPs showed higher diversity of habitat indicator species than arable land and improved grasslands, with vegetation between solar arrays showing higher numbers of species important for ES provision (e.g., N-fixing species important for nutrient cycling) than vegetation under solar panels. Overall, the diversity of habitat indicator species seemed highly dependent on former land-use, showing SPs have the potential to enhance ecosystem services provision if built on degraded agricultural land.

Developing this understanding will enable optimisation of SP design and management to ensure delivery of ecosystem co-benefits from this growing land-use.
The impact of atmosphere-ocean-wave coupling on extreme surface wind forecasts
Authors: Gentile Emanuele Silvio , Gray Suzanne L. , Barlow Janet F. , Lewis Huw W. , Edwards John M.
Published: March 2021

Accurate modelling of air-sea surface exchanges is crucial for reliable extreme surface wind forecasts.  While atmosphere-only weather forecast models represent ocean and wave effects through sea-state independent parametrizations, coupled multi-model systems capture sea-state dynamics by integrating feedbacks between atmosphere, ocean and wave model components.

Here, we present the results of studying the sensitivity of extreme surface wind speeds to air-sea exchanges at kilometre scale using coupled and uncoupled configurations of the Met Office's UK Regional Coupled Environmental Prediction (UKC4) system. The case period includes the passage of extra-tropical cyclones Helen, Ali, and Bronagh, which brought maximum gusts of 36 ms-1 over the UK.

Compared to the atmosphere-only results, coupling to ocean decreases the domain-average sea surface temperature by up to 0.5 K. Inclusion of coupling to waves decreases the 98th percentile 10-m wind speed by up to 2 ms-1 as young, growing wind waves decrease wind speed by increasing the sea aerodynamic roughness. Impacts on gusts are more modest, with local reductions of up to 1ms -1, due to enhanced boundary-layer turbulence which partially offsets air-sea momentum transfer.

Using a new drag parametrization based on the COARE~4.0 scheme, with a cap on the neutral drag coefficient and decrease for wind speeds exceeding 27 ms-1 , the atmosphere-only model achieves equivalent impacts on 10-m wind speeds and gusts as from coupling to waves. Overall, the new drag parametrization achieves the same 20% improvement in forecast 10-m wind skill as coupling to waves, with  the  advantage  of saving the computational cost of the ocean and wave models. 
Gradient-boosted equivalent sources for gridding large gravity and magnetic datasets
Authors: Soler Santiago Rubén , Uieda Leonardo
Published: March 2021

The equivalent source technique is a well known method for interpolating gravity and magnetic data. It consists in defining a set of finite sources that generate the same observed field and using them to predict the values of the field at unobserved locations. The equivalent source technique has some advantages over general-purpose interpolators: the variation of the field due to the height of the observation points is taken into account and the predicted values belong to an harmonic field. These make equivalent sources a more suited interpolator for any data deriving from a harmonic field (like gravity disturbances and magnetic anomalies). Nevertheless, it has one drawback: the computational cost. The process of estimating the coefficients of the sources that best fit the observed values is very computationally demanding: a Jacobian matrix with number of observation points times number of sources elements must be built and then used to fit the source coefficients though a least-squares method. Increasing the number of data points can make the Jacobian matrix to grow so large that it cannot fit in computer memory.

We present a gradient-boosting equivalent source method for interpolating large datasets. In it, we define small subsets of equivalent sources that are fitted against neighbouring data points. The process is iteratively carried out, fitting one subset of sources on each iteration to the residual field from previous iterations. This new method is inspired by the gradient-boosting technique, mainly used in machine learning solutions.

We show that the gradient-boosted equivalent sources are capable of producing accurate predictions by testing against synthetic surveys. Moreover, we were able to grid a gravity dataset from Australia with more than 1.7 million points on a modest personal computer in less than half an hour.
Fine-Scale Climate Projections for Africa: What Additional Robust Spatial Detail is Provided by a Convection-Permitting Model?  
Authors: Rowell Dave , Berthou Segolene
Published: March 2021

Regional climate projections using ultra-high resolution convection-permitting (CP) models are now increasingly available, with recent endeavours also focussing on vulnerable tropical regions. A number of recent studies have examined a pair of pan-Africa integrations of the Met Office CP model (CP4A), run at 4.4km resolution with 10 years of both a present-day simulation and a circa-2100 projection. However, experience from inter-disciplinary discussions has revealed different perspectives on the value of such experiments, with climate scientists emphasising the importance of an improved representation of convection, whereas applied scientists emphasise the importance of the unprecedented spatial scale of the available climate data. This raises critical questions about the usable spatial scales of such projections. Can CP models really provide robust information about future climate change at finer scales than parameterised regional climate models? We address this question with a focus on projected changes in rainfall, both seasonal means and daily extremes, both of which may be expected to exhibit heterogeneous climate responses in regions of large surface forcing. Although the capacity for statistically significant detail is found to be small in this short projection, detectable sub-25km variability is indeed apparent in regions of high topographic variability. Coastal regions, such as lakes and marine bays are also examined, along with urban boundaries. Furthermore, where no significant fine-scale detail is apparent (spatial heterogeneity is only due to sampling variability), we also examine the extent to which the robustness of climate information (better signal-to-noise ratios) can be enhanced for users by the spatial aggregation of model data.
Photooxidation and ozonolysis of Δ3-carene and its oxidation product caronaldehyde in the atmospheric simulation chamber SAPHIR
Authors: Hantschke Luisa , Novelli Anna , Bohn Birger , Cho Changmin , Reimer David , Tillmann Ralf , Rohrer Franz , Glowania Marvin , Hofzumahaus Andreas , Wahner Andreas , Kiendler-Scharr Astrid , Fuchs Hendrik
Published: March 2021

Of the total global annual monoterpene emissions, Δ3-carene contributes 4.5 %, making it the 7th most abundant monoterpene worldwide. As it is primarily emitted by pine trees, Δ3-carene can regionally gain in importance, for example in boreal forests and Mediterranean regions.  Oxidation products of monoterpenes such as organic nitrates and aldehydes are known to impact the formation of secondary pollutants such as ozone and particles, so understanding their atmospheric formation and fate is crucial.

The photooxidation and ozonolysis of Δ3-carene and the photooxidation and photolysis of its main daytime photooxidation product caronaldehyde were investigated in the atmospheric simulation chamber SAPHIR. Oxidation reactions were studied under atmospheric conditions with high (> 8 ppbv) and low (< 2 ppbv) NOx concentrations. Reaction rate constants of the reaction of Δ3-carene with OH and O3, and of the reaction of caronaldehyde with OH as well as photolysis frequencies of caronaldehyde were determined. Production and destruction rates of the sum of hydroxyl and peroxy radicals (ROx = OH+HO2+RO2) were analysed to determine if there were unaccounted production and loss processes of radicals in the oxidation of Δ3-carene. The yield of Δ3-carene’s oxidation product caronaldehyde was determined from measured timeseries from OH photooxidation and ozonolysis experiments. Additionally, the OH yield from ozonolysis of Δ3-carene was determined.

Organic nitrate (RONO2) yields of the reaction of RO2 + NO, from RO2 produced from the reactions of Δ3-carene and caronaldehyde with OH were determined by analyzing the reactive nitrogen species (NOy) in the chamber.
Morphodynamics of active meandering rivers in a hierarchy of spatial and temporal scales
Authors: Hooke Janet
Published: March 2021

Active meandering rivers have the advantage of exhibiting morphodynamic changes at such a rate that changes are detectable on a range of timescales, from event, through decadal, to centennial.  The evidence from river reaches that have been investigated directly for 40 years by various methods is used to examine the morphodynamics over differing spatial and temporal scales. Several questions can be addressed, including:   what channel changes are produced by different events, discharge periods and sequences; how do events and phases combine to produce changes in position and in morphology; to what extent are such changes coherent, systematic and predictable. The combination of evidence from detailed cross-sectional surveys, field mapping, drone and aerial photographic surveys and use of historical maps demonstrates how the morphodynamics at different scales combine and interact. Analysis indicates some systematic changes at cross-sectional and bend scale but contrasts between different reaches, bends and within bends, and reveals complex patterns and lags in propagation of change. Survey and monitoring requirements to detect and understand the interactions are identified. Research into these active meandering rivers may be indicative and helpful for our wider understanding of less dynamic rivers, where changes are less easily detected. It raises the question of whether the mechanisms are similar in more stable rivers and reaches.
Applying machine learning for drought prediction using a large ensemble of climate simulations
Authors: Felsche Elizaveta , Ludwig Ralf
Published: March 2021

There is strong scientific and social interest to understand the factors leading to extreme events in order to improve the management of risks associated with hazards like droughts. Recent events like the summer 2018 drought in Germany already had severe und unexpected impacts, e.g. forest fires and crop failures; in order to increase preparedness robust prediction tools are  urgently required. In this study, machine learning methods are applied to predict the occurrence of a drought with lead times of one to three months. The approach takes into account a list of thirty atmospheric and soil variables as predictor input parameters from a single regional climate model initial condition large ensemble (CRCM5-LE). The data was produced the context of the ClimEx project by Ouranos with the Canadian Regional Climate Model (CRCM5) driven by 50 members of the Canadian Earth System Model (CanESM2) for the Bavarian and Quebec domains.

Drought occurrence was defined using the Standardized Precipitation Index. The training and test datasets were chosen from the current climatology (1955-2005) for the Munich and Lisbon subdomain within the CRCM5-LE. The best performing machine learning algorithms managed to obtain a correct classification of drought or no drought for a lead time of one month for around 60 % of the events of each class for the both domains. Explainable AI methods like feature importance and shapley values were applied to gain a better understanding of the trained algorithms. Physical variables like the North Atlantic Oscillation Index and air pressure one month before the event proved to be of high importance for the prediction. The study showed that better accuracies can be obtained for the Lisbon domain, due to the stronger influence of the North Atlantic Oscillation Index on Portugal’s climate.
Measuring Carbon Dioxide from the International Space Station: An Overview of the OCO-3 Mission
Authors: Eldering Annmarie , O'Dell Christopher , Fisher Brendan , Kiel Matthäus , Nelson Robert , Taylor Tommy , Somkuti Peter , Osterman Greg , Pavlick Ryan , Kurosu Thomas , Spiers Gary
Published: March 2021

The Orbiting Carbon Observatory 3 (OCO-3) was installed on the International Space Station (ISS) in May 2019 and began routine operations in August 2019 to continue global CO2 and solar-induced chlorophyll fluorescence (SIF) observations using the flight spare instrument from OCO-2. The first version of the data, called vEarly, was released in early 2020, and an update, v10, is being prepared.

The growing OCO-3 dataset includes the standard ocean and land measurements, as well as a large set of validation measurements over TCCON stations and a new locally focused measurement. The new Snapshot Area Map (SAM) mode, where 80km by 80km areas are sampled with 2km by 2km footprints in 2 minutes is measurement approach unique to OCO-3. This is a new observation mode made possible by the agile pointing mirror assembly of OCO-3. Data has been collected over hundreds of cities, volcanos, over areas of interest to the terrestrial carbon community, and in coordination with field campaigns.

The cross comparison of OCO-3 and OCO-2 data, for radiances, XCO2, and SIF is underway to gain insights into data quality and to create and OCO-3 dataset that can be used seamlessly with OCO-2 measurements. We will discuss these intercomparisons, highlighting a few examples, such as the OCO-2 and OCO-3 target and SAM measurements in Los Angeles that were collected on the same day. Highlights from validation activities and global XCO2 data characteristics will be presented, as well as details of the SAM collection statistics and most sampled regions. The value of the OCO-3 dataset for characterization of diurnal patterns will also be shared.

Highlights of the key scientific findings from the mission to date will be included. Finally, looking forward, I will also discuss the mission status, including the expectations for the remaining mission life and progress on developing an improved data version to be released in late spring/early summer 2021.
An implicit model for soil thermal conductivity and matric potential
Authors: Lu Yili , Ren Tusheng , Lu Sen , Horton Robert
Published: March 2021

Soil thermal conductivity (λ) is affected by the energy status of water and is closely related to soil matric potential (h). In this study, a soil water retention curve and a soil thermal conductivity curve were linked via the critical point that separated the adsorption water and capillary water regimes. Based on existing water retention curve and a thermal conductivity curve models, we derived a new implicit mathematical formulation of the λ-h relationship. The λ-h relationship was valid for the entire water content range at room temperature. The new model parameter values for adsorption, capillarity and soil thermal conduction were optimized, and a linear relationship between critical water content and maximum adsorption capacity was established by fitting the SWRC and STCC models to measurements from eight soils. Laboratory evaluations using λ and h measurements on a loam soil and a clay loam soil showed that the new model well described observed values with coefficients of determination greater than 0.97. The implicit model can quantify λ-h behaviors for various soil textures over the entire water content range.
The unique behavior of stable water isotopes profiles during interglacial periods at Talos Dome, Antarctica
Authors: Crotti Ilaria , Landais Amaelle , Stenni Barbara , Frezzotti Massimo , Quiquet Aurélien , Prié Frédéric , Minster Bénédicte , Dreossi Giuliano , Barbante Carlo
Published: March 2021

The growth and decay of marine ice sheets act as important controls on regional and global climate, in particular, the behavior of the ice sheets is a key uncertainty in predicting sea-level rise during and beyond this century. The East Antarctic Ice Sheet (EAIS), which contains deep subglacial basins with reverse-sloping, is considered to be susceptible to ice loss caused by marine ice sheet instability. Sediment core offshore Wilkes Subglacial Basin reveals oscillations in the provenance of detrital sediment that have been interpreted to reflect an erosion of Wilkes Basin during interglacial periods MIS 5, MIS 7, and MIS 9 greater than Holocene period (Wilson et al., 2018). The aim of our study is to investigate past climate and environmental changes in the coastal area of the East Antarctic Ice Sheet during MIS 7.5 and 9.3 with the help of a new high-resolution water isotopes record of the TALDICE ice core.

Here we present new δ18O and δD high resolution (5 cm) records covering the oldest portion of the TALDICE ice core. MIS 7.5 and 9.3 isotopic signal reveals a unique feature, already observed for MIS 5.5, that has not been spotted in other Antarctic ice cores (Masson-Delmotte et al., 2011). Interglacial periods at TALDICE are characterized by a first peak, observed in correspondence to the culmination of the deglaciation event as for all Antarctic cores, followed by a less pronounced isotopic peak (for MIS 5.5 and 9.3) or a plateau (for MIS 7.5) prior to the glacial inception. Several factors might drive this peculiar behavior of the water stable isotopes record, as an increase in temperatures due to a drop in surface elevation or changes in moisture sources.

The new δ18O and δD high-resolution records for the TALDICE ice core reveal a unique pattern that characterizes interglacial periods at Talos Dome. Taking into account the coastal position of the core and its vicinity to the Wilkes Subglacial Basin we intend to investigate the possible decrease in surface elevation, through the application of the GRISLI ice sheet model (Quiquet et al., 2018), and changes in moisture sources, traceable from the d-excess record.
Sub-grid scale representation of halogen chemistry in volcanic plumes based on 1D MOCAGE model simulations
Authors: Marécal Virginie , Voisin-Pessis Ronan , Roberts Tjarda , Hamer Paul , Aiuppa Alessandro , Guth Jonathan , Narivelo Herizo
Published: March 2021

Halogen halides emitted by volcanoes are known to rapidly convert within plumes into BrO while depleting ozone, as clearly shown by observations and models over the past 2 decades (e.g. review by Gutmann et al., 2018). So far, most of the modelling studies have focused on the plume processes occurring in the first few hours after the emission. The only study at the regional scale is that of Jourdain et al. (2016). They assessed the impact of volcanic halogens for a period of strong degassing of the Ambrym volcano, showing in particular its effect on the atmospheric oxidizing capacity and methane lifetime.

A step further would be to quantify the impact of volcanic halogens at the global scale using global chemistry models. This type of model uses a horizontal resolution (greater than 50 km) that is much coarser than the plume size. This raises the issue of, whether at this resolution, it is possible to represent the chemistry occurring under high concentrations within the plume. To assess this, a sub-grid scale parameterization is proposed. It has been tested in the 1D version of MOCAGE global and regional chemistry transport model for a short eruption of Mt Etna on the 10th of May 2008. The results show that while using the subgrid-scale plume parameterization or not does change the timing of when the maximum BrO occurs but does not affect the predicted maximum concentration. The same finding is made when using a range of different settings in the parameterization regarding dilution of the plume with its environment. The 1D model results show a sensitivity of BrO formation to parameters other than the sub-grid scale effects: composition of the plume at the vent, injection height of the emissions, and time of the day when the eruption takes place.
Experimental and Simulated Spectral Gamma-Ray Response of a NaI(Tl) Scintillation Detector used in Airborne Gamma-Ray Spectrometry
Authors: Breitenmoser David
Published: March 2021

The objective of this work is to simulate the spectral gamma-ray response of NaI(Tl) scintillation detectors for airborne gamma-ray spectrometry (AGRS) using Monte Carlo radiation transport codes. The study is based on a commercial airborne gamma-ray spectrometry detector system with four individual NaI(Tl) scintillation crystals and a total volume of 16.8 l. Monte Carlo source-detector simulations were performed in an event-by-event mode with the commercial multi-purpose transport codes MCNP6.2 and FLUKA. Validation measurements were conducted using 241Am, 133Ba, 60Co, 137Cs and 152Eu radiation sources with known activities and source-detector geometries. Energy resolution functions were derived from these measurements combined with additional measurements of natural Uranium, Thorium and Potassium sources. The simulation results are in good agreement with the experimental data with a maximum relative error in the full-energy peak counts of 10%. In addition, no significant difference between the two Monte Carlo radiation transport codes was found with respect to a 95% confidence level. The validated detector model presented herein can be adopted for angular detector response analysis and calibration computations relating radionuclide activity concentrations with spectral detector counts.
Alternative viscous-plastic rheologies for the representation of fracture lines in high-resolution sea ice models
Authors: Ringeisen Damien , Losch Martin , Tremblay L. Bruno
Published: March 2021

Fracture lines dominate the dynamics of sea ice. They affect the ice mass balance and the heat transfer between the atmosphere and the ocean. Therefore, climate modeling and sea ice prediction require an accurate fracture representation. Most sea ice models use viscous-plastic (VP) rheologies to simulate sea ice internal stresses. One of the issues with these rheologies is that they overestimate the intersection angles between fracture lines, with consequences for the subsequent sea ice drift. In idealized experiments, we investigate the mechanisms linking VP rheologies and fracture angles and assess alternative rheologies for high-resolution modeling. Results show that the definition of the transition between viscous and plastic states is essential for the creation of sharp fracture lines. The fracture angles with Mohr-Coulomb yield curves agree with the Arthur fault orientation theory. Further, rheologies with Mohr-Coulomb yield curves or teardrop yield curves appear to reduce intersection angles. Finally, experiments show that these results are reproduced for different sea ice initial conditions. With rheologies that favor smaller intersection angles, sea ice models move a step closer to accurate sea ice dynamics at high-resolution.
Large scale thermospheric density enhancements in relation to downward Poynting fluxes: Statistics from CHAMP, AMPERE and SuperDARN
Authors: Billett Daniel , Perry Gareth , Clausen Lasse , Archer William , McWilliams Kathryn , Haaland Stein , Burchill Johnathan
Published: March 2021

Large thermospheric neutral density enhancements in the cusp region have been examined for many years. The CHAMP satellite for example has enabled many observations of the perturbation, showing that it is mesoscale in size and exists on statistical timescales. Further studies examining the relationship with magnetospheric energy input have shown that fine-scale Poynting fluxes are associated with the density perturbations on a case-by-case basis, whilst others have found that mesoscale downward fluxes also exist in the cusp region statistically.

In this study, we use nearly 8 years of the overlapping SuperDARN and AMPERE datasets to generate global-scale patterns of the high-latitude and height-integrated Poynting flux into the ionosphere, with a time resolution of two minutes. From these, average patterns are generated based on the IMF orientation. We show the cusp is indeed an important feature in the Poynting flux maps, but the magnitude does not correlate well with statistical neutral mass density perturbations observed by the CHAMP satellite on similar spatial scales. Mesoscale height-integrated Poynting fluxes thus cannot fully account for the cusp neutral mass density enhancement, meaning energy deposition in the F-region or on fine-scales, which is not captured by our analysis, could be the primary driver.
Environmental impact and treatment of hydraulic fracturing in shale gas
Authors: Wang Heng , Zhou Lifa
Published: March 2021

Hydraulic fracturing is one of the key technologies to stimulate shale gas production and may have some environmental impacts while enhancing shale gas development. Through the introduction of hydraulic fracturing technology from the design and construction aspects, analysis of its potential adverse environmental impacts in water resource consumption, surface water and groundwater pollution, geological disasters, and other aspects, and based on the existing problems to form targeted solutions.

According to EIA report, during the stimulation process of shale gas fracturing, the amount of water resources is about 10,000m3, of which 20%-80% can be returned, and the flowback rate of Shale gas in China is 20%-60%, which means that at least 20%-40% polluted water containing various chemical raw materials will be hidden in the formation for a long time. The shale flowback rate in China is significantly lower than that in the United States, not only due to formation conditions, but also due to equipment and technology. In view of this situation, it is necessary to control the whole process from design to construction.

In the design process of hydraulic fracturing of shale gas, real-time control of the fracture range is carried out in conjunction with seismic monitoring and software simulation fitting, so as to reduce the consumption of water resources on the premise of achieving the purpose of increasing production. Especially, to reducing the fracturing program as much as possible in the water-scarce areas, so as to ensure the security of public water resources. Reduce the use of chemical additives to alleviate the pollution of surface water and groundwater. After detection of possible pollution, determine the amount of pollution sources on site and carry out comprehensive pollutant recovery and treatment. Strictly prohibit high-risk pollution sources from entering the fracturing fluid process. At the same time, the fracturing fluid is used to recycled and purified. In terms of geological disasters caused by fracturing, high-risk geological disaster zones should be identified and monitored in advance to prevent large-scale geological activities caused by micro-earthquakes caused by fracturing from causing uncontrollable geological disasters.
Investigating the plate kinematics of continental blocks and their role on the deformation experienced along the Iberia-Eurasia plate boundary using deformable plate tectonic models
Authors: King Michael , Welford Kim , Cadenas Patricia , Tugend Julie
Published: March 2021

The kinematics of the Iberian plate during Mesozoic extension and subsequent Alpine compression and their implications on the partitioning of strain experienced across the Iberia-Europe plate boundary continue to be a subject of scientific interest, and debate. To date, the majority of plate tectonic models only consider the motion of rigid tectonic plates. In addition, the lack of consideration for the kinematics of intra-continental domains and intervening continental blocks in-between has led to numerous discrepancies between rigid plate kinematic models of Iberia, based mainly on tight-fit reconstruction of M-series magnetic anomalies, and their ability to reconcile geological and geophysical observations. To address these discrepancies, deformable plate tectonic models constrained by previous plate reconstructions, geological, and geophysical studies are built using the GPlates software to study the evolution of deformation experienced along the Iberia-Eurasia plate boundary from the Triassic to present day. These deformable plate models consider the kinematics of small intra-continental blocks such as the Landes High and Ebro Block situated between large tectonic plates, their interplay with pre-existing structural trends, and the collective impact of these phenomena on the deformation experienced during Mesozoic rifting and Alpine compressional re-activation along the Iberia-European plate boundary. Preliminary results suggest that the independent kinematics of the Landes High played a key role on the distribution of oblique extension between different rift arms and resultant deformation within the Bay of Biscay. Within the Pyrenean realm, deformation experienced prior to and during the Alpine Orogeny was more largely controlled by the interplay between the Ebro Block kinematics and rift segmentation induced by the orientation of inherited trends.
Sediment drifts at the eastern Kerguelen Plateau: Achives of climate and circulation development
Authors: Uenzelmann-Neben Gabriele , Schneider Matthias , Westerhold Thomas , Zirks Eleen
Published: March 2021

The Kerguelen Plateau, southern Indian Ocean rises up 2000 m above the surrounding seafloor and hence forms an obstacle for the flow of the Antarctic Circumpolar Current (ACC) and the Antarctic Bottomwater (AABW). The ACC is strongly deviated in its flow towards the north. A branch of the AABW flows northwards along the eastern flank of the plateau and in its path is steered by several basement highs and William’s Ridge. Seismic data collected during RV Sonne cruise SO272 image sediment drifts shaped in the Labuan Basin, which document onset and variabilities in pathway and intensity of this AABW branch in relation to the development of the Antarctic ice sheet and tectonic processes, e.g., the opening of the Tasman gateway. The eastern flank of the Kerguelen shows strong erosion of the post-mid Eocene sequences. In places, the Paleocene/early Eocene sequences are also affected by thinning and erosion. A moatcan be observed along the Kerguelen Plateau flank indicating the flowpath of the north setting AAWB branch. Sediment drifts and sediment waves are formed east of the moat. Similar features are observed at the inner, western flank of William’s Ridge thus outlining the recirculation of the AABW branch in the Labuan Basin. The chronological and spatial will be reconstructed via the analysis of those sedimentary structures to provide constraints on climate and ocean circulation variability.
The effects of bed topography and strength on stability of marine ice sheets
Authors: Sergienko Olga , Wingham Duncan
Published: March 2021

The "marine ice-sheet instability hypothesis", which states that unconfined marine ice sheets are unconditionally unstable on retrograde slopes, was developed under assumptions of negligible bed slopes. Realistic ice sheets, however, flow over beds which topographies have a wide range of bed slopes (for example, Thwaites Glacier in the Amundsen Sea sector, West Antarctica). Reexamining the original model of marine ice sheets proposed by Schoof (2007), and relaxing an assumption of negligible bed slopes, we find that a steady-state ice flux at the grounding line is an implicit function of the grounding-line ice thickness, bed slope and accumulation rate. Depending on the sliding conditions, the magnitudes of the ice flux at the grounding line differ by one-to-three orders of magnitudes from that computed with a power-law expression derived by Schoof (2007) under assumptions of the negligible bed slopes. Non-negligible bed slopes also result in conditions of stability of the grounding line that are significantly more complex than those associated with the "marine ice sheet instability hypothesis". Bed slopes are no longer the sole determinant of whether the grounding line is stable or unstable. We find that the grounding line can be stable on beds with retrograde slopes and unstable on beds with prograde slopes. 
The Global Energy Balance as represented in CMIP6 climate models  
Authors: Wild Martin
Published: March 2021

A plausible simulation of the global energy balance is a first-order requirement for a credible climate model. In the present study I investigate the representation of the global energy balance in 40 state-of-the-art global climate models participating in the Coupled Model Intercomparison Project phase 6 (CMIP6). In the CMIP6 multi-model mean, the magnitudes of the energy balance components are often in better agreement with recent reference estimates compared to earlier model generations  such as CMIP5 on a global mean basis. However, the inter-model spread in the representation of many of the components remains substantial, often on the order of 10-20 Wm-2 globally,  except for aspects of the shortwave clear-sky budgets, which are now more consistently simulated by the CMIP6 models. The substantial inter-model spread in the simulated global mean latent heat fluxes in the CMIP6 models, exceeding 20% (18 Wm-2),  further implies also large discrepancies in their representation of the global water balance. From a historic perspective of model development over the past decades, the largest adjustments in the magnitudes of the simulated present-day global mean energy balance components occurred in the shortwave atmospheric clear-sky absorption and the surface downward longwave radiation. Both components were gradually adjusted upwards over several model generations, on the order of 10 Wm-2, to reach 73 and 344 Wm-2, respectively in the CMIP6 multi-model means. Thereby, CMIP6 has become the first model generation that largely remediates long-standing model deficiencies related to an overestimation in surface downward shortwave and compensational underestimation in downward longwave radiation in its multi-model mean (Wild 2020).

Published in: Wild, M., 2020: The global energy balance as represented in CMIP6 climate models. Clim Dyn 55, 553–577. https://doi.org/10.1007/s00382-020-05282-7

 
A Tale of Two Deltas: Comparative Study on the Effects of Dam Regulation on Deltaic Hydrological Regime and Morphological Evolution
Authors: Gao Weilun , Li Dongxue , Amenuvor Mawusi , Tong Yao , Shao Dongdong , Cui Baoshan
Published: March 2021

Deltas are among the most populous areas and most productive ecosystems on Earth. Despite their critical importance for human society and coastal ecosystems, many of the world’s deltas are drowning due to substantial decrease in sediment supply, sea level rise, etc. Previous studies have demonstrated the effects of dam regulation on the hydrological regime and morphological evolution of river deltas. However, past attention was mostly paid to individual deltas or deltas at a global scale, while comparative studies on selected deltas are scarce in the literature. In this study, a comparative study on two wave-influenced deltas, namely, the Volta River Delta in Ghana and the Yellow River Delta in China, was conducted. The trend of change of the annual river discharge and sediment load of the two deltas before and after the construction of the major dams were analyzed, and the resultant effects on deltaic morphological evolution were also examined and compared between the two deltas. The results show that the average annual river discharge and sediment load and their inter-annual variation decreased significantly after the construction of major upstream dams for both deltas. However, presumably due to the differences in reservoir capacity and upstream location of the dams, the sediment load of the Volta River Delta decreased abruptly to <10% of the sediment load in the pre-dam period after the construction of the Akosombo Dam in 1964 and became stable afterwards, whereas the sediment load of the Yellow River Delta decreased substantially to ~10% of pre-dam level but in a more gradual stepwise manner since the 1950s. As a result, after the intense shoreline retreat in the 1960s, the delta area of the Volta River Delta appeared to adjust to the reduced yet stable sediment load and shift to a new quasi-equilibrium with minimal change (maximum 0.53%). On the contrary, the Yellow River Delta still kept prograding at the river mouth given the current sediment load. However, it is foreseeable that if the trend of sediment reduction persists, it may potentially turn net delta progradation to erosion and further into a new quasi-equilibrium like the Volta River Delta. Our study provides a new perspective for understanding the future evolution of the Yellow River Delta as well as other deltas around the world that share similar characteristics and forcing factors.
Unexpected frequency-sweep reverse of subelements in chorus rising tone
Authors: Liu Si , Gao Zhonglei
Published: March 2021

Nonlinear resonance between energetic electrons and chorus waves is widely used to explain the frequency sweep of chorus, which predicts that rising tone elements are comprised by multiple subpackets with the frequency gradually increasing. Here we report two events that subelements with their frequencies downward chirping occur in rising tone chorus. The duration of those subelements is comparable with the regular subpackets, and their frequency sweep rates 6-12 kHz/s are consistent with previous theory and observations. Waveform of the subelement shows similar morphology to regular chorus element, consisting several finer structures "hyper-subpackets". We propose a possible scenario that the falling tone subelements are formed by nonlinear process with much shorter timescale. The starting frequency of each subelement controlled by the linear growth phase increases may because the electron distribution varies fast. This study provides new insight on chorus generation and also brings challenges.
Physical properties and spatial distribution of the sea ice surface layer (SSL/snow) during the autumn phase of the MOSAiC expedition
Authors: Dadic Ruzica , Schneebeli Martin , Hannula Henna-Reeta , Macfarlane Amy , Pirazzini Roberta
Published: March 2021

Snow cover dominates the thermal and optical properties of sea ice and the energy fluxes between the ocean and the atmosphere, yet data on the physical properties of snow and its effects on sea ice are limited. This lack of data leads to two significant problems: 1) significant biases in model representations of the sea ice cover and the processes that drive it, and 2) large uncertainties in how sea ice influences the global energy budget and the coupling of climate feedback. The  MOSAiC research initiative enabled the most extensive data collection of snow and surface scattering layer (SSL) properties over sea ice to date. During leg 5 of the MOSAiC expedition, we collected multi-scale (microscale to 100-m scale) measurements of the surface layer (snow/SSL) over first year ice (FYI) and MYI on a daily basis. The ultimate goal of our measurements is to determine the spatial distribution of physical properties of the surface layer. During leg 5 of the MOSAiC expedition, that surface layer changed from the  surface scattering layer (SSL),   characteristic for the melt season, to an early autumn snow pack. Here,  we will present data showing both a) the physical properties and the spatial distribution of the SSL during the late melt season and b) the transition of the sea ice surface from the SSL to the fresh autumn snowpack. The structural properties of this transition period are poorly documented, and this season is critical  for the initialization of sea ice and snow models. Furthermore, these data are crucial to interpret simultaneous observations of surface energy fluxes, surface optical and remote sensing data (microwave signals in particular), near-surface biochemical activity, and to understand the sea ice  processes that occur as the sea ice transitions from melting to freezing.
Seasonal contribution to the spice generation in subtropical south Indian salinity maxima
Authors: Kaundal Madhu , Nadimpalli Jithendra , Dash Mihir
Published: March 2021

Regions of salinity maxima (Smax) in the world oceans experience spiciness changes which in-turn subduct and advect towards equator along the shallow meridional overturning cell. Advection results in stabilizing vertical salinity gradient (salinity increasing with depth) along westward and equatorward edges of Smax region whereas eastward and poleward edges holds destabilizing vertical salinity gradient with maximum salinity at surface (salinity decreasing with depth). Based on this contrast vertical salinity gradient, subtropical south Indian Ocean salinity maxima region is divided into two boxes along 30ºS. Seasonal evolultion of spiciness with respect to atmospheric and oceanic forcings, are investigated by using high frequency (3-day), high resolution (0.25º) ECCO (Estimating the Circulation and Climate of the Ocean) estimate. It is observed that in both these boxes, spice generation mechanisms are different. During austral winter, 25-sigma isopycnal outcrops to the north of 30S (northern box), along which the Temperature/Salinity changes subduct and hence spiciness anomalies are formed below the mixed layer. However, destabilization of vertical salinity gradient to the south of 30S (southern box), concomitant with weak stratification results in convective mixing at the mixed layer base and hence the spiciness changes penetrate the main thermocline. Seasonal mixed layer heat and salt budget analysis show that the surface heat and freshwater fluxes are the main forcings controlling monthly evolution of spiciness in the northern box, whereas in the southern box entrainment and meridional advection terms are mainly contributing for the spiciness changes.