bluuebunny/crossref_metadata_2025 huggingface dataset:
Using laboratory investigations to reveal the palaeohydrological implications of aragonite laminae deposition in the endorheic Dead Sea and its precursors under different climatic conditions
Authors: Ben Dor Yoav , Flax Tomer , Levitan Itamar , Brauer Achim , Enzel Yehouda , Erel Yigal
Published: March 2021

The sedimentary record of the endorheic Dead Sea and its precursors comprises aragonite laminae that make up an environmental archive extending into the Pleistocene, partially in annual resolution. Nevertheless, despite the importance of resolving the conditions that facilitate aragonite precipitation in the Dead Sea, contradictions exist between recent studies that utilized modern observations and the late Pleistocene geological record. The implications of aragonite precipitation in the Dead Sea and in its late Pleistocene predecessor Lake Lisan were investigated in this study by mixing natural and synthetic brines with a synthetic bicarbonate solution representing flood water entering the lake (4mM), with and without additions of extracellular polymeric substances (EPS). This was followed by measurements of aragonite precipitation incubation, rates, yields. Aragonite precipitation took place within days to few weeks after mixing of the brine with the synthetic bicarbonate solution and its incubation time was proportional to bicarbonate concentrations, while precipitation rates were also influenced by ionic strength. The addition of EPS inhibited aragonite precipitation for several months, which provides a reasonable explanation for the proposed summer-time precipitation of aragonite during the late Pleistocene glacials. We suggest that under increased inflow, increased biological activity would result in increased EPS production that could inhibit aragonite precipitation for several months. Finally, previous estimates of the freshwater inflow required to provide the carbonate for a uniform aragonite lamina of a typical thickness deposited during glacials are unreasonably high. This can be resolved by various processes: (1) Patchy aragonite deposition over limited segments of the lake’s floor; (2) Supply of additional carbonate to the lake from aeolian dust and recycled dust deposits; (3) Carbonate production through the oxidation of organic carbon by sulfate-reducing bacteria at the hypolimnion. Altogether, these results indicate that aragonite laminae thicknesses are insufficient to quantitatively reconstruct the hydrological balance for the entire lake, but may still be valuable for identifying climatic periodicities over a continuous record in a specific study site.
Triggering the Indian Ocean Dipole from the Southern Hemisphere
Authors: Zhang Lian-Yi , Du Yan , Cai Wenju , Chen Zesheng , Tozuka Tomoki , Yu Jin-Yi
Published: March 2021

This study identifies a new triggering mechanism of the Indian Ocean Dipole (IOD) from the Southern Hemisphere. This mechanism is independent from the El Niño/Southern Oscillation (ENSO) and tends to induce the IOD before its canonical peak season. The joint effects of this mechanism and ENSO may explain different lifetimes and strengths of the IOD. During its positive phase, development of sea surface temperature cold anomalies commences in the southern Indian Ocean, accompanied by an anomalous subtropical high system and anomalous southeasterly winds. The eastward movement of these anomalies enhances the monsoon off Sumatra-Java during May-August, leading to an early positive IOD onset. The pressure variability in the subtropical area is related with the Southern Annular Mode, suggesting a teleconnection between high-latitude and mid-latitude climate that can further affect the tropics. To include the subtropical signals may help model prediction of the IOD event.
Orbital pacing of redox cycles suggested by red bed color of the Late Triassic Chinle Formation, Arizona
Authors: Lepre Christopher , Yazzie Owen , Olsen Paul
Published: March 2021

Late Triassic records of the orbital pacing of climate are well documented from the stratigraphy of lake basins and marine facies. However, fewer studies have focused on detecting orbital climate signals preserved by fluvial depositional environments, home to terrestrial life. The sedimentary Chinle Formation of the Colorado Plateau (southwestern USA) is a succession of Late Triassic largely red beds that preserves numerous vertebrate fossils, including evidence of the Adamanian–Revueltian tetrapod faunal transition. Floodplain mudstones showing pedogenic features alternate on various thickness scales with channel sandstones. We assessed the cyclostratigraphy of red bed color for a ~250-m-thick interval of the Chinle Formation dated to 209-216 Ma using a scientific drill core from the Petrified Forest National Park, Arizona, 1A. Diffuse reflectance spectroscopy demonstrates that red bed color in this core derives from the mineral hematite, probably formed in response to the wetting and drying of soils under monsoonal rainfall. The magnetochronology and high-precision U-Pb detrital zircon dates of the core, and the astrochronostratigraphic polarity time scale of the Newark-Hartford basins are used to provide an age model for our spectral analyses and cyclostratigraphy. From the red-green and yellow-blue time series, we identified evidence of the long eccentricity, Jupiter-Venus cycle (405 kyr), longer-period grand eccentricity cycles including the Mars-Earth cycle, and possibly the Mars-Earth inclination cycle. There are also hints at higher frequency cycles. Although the relative amount of 405 kyr power is a fraction of the total variability, there is significant coherence between the Newark Basin depth rank record and the Chinle color at the 405 kyr and the ~100 kyr cycles. Our findings support previous interpretations that color and hematite variations formed during the Late Triassic and are unrelated to a younger diagenetic component of the red beds. Fluvial accumulation of the Chinle sediments was not as discontinuous as other studies have suggested, allowing for a reconstruction of orbital climate changes that may have affected the development of terrestrial ecosystems in Western Equatorial Pangaea.
Reduced Complexity Model Intercomparison Project (RCMIP)
Authors: Nicholls Zebedee ,   Reduced complexity model intercomparison project contributors
Published: March 2021

Reduced-complexity climate models form part of the climate model hierarchy and are increasingly relied upon at the science-policy interface. Historically, evaluation of reduced-complexity climate models has been limited to a number of independent studies. Here we present the reduced-complexity model intercomparison project (RCMIP), the first systematic, community-organised evaluation of reduced-complexity climate models. We introduce the motivation behind RCMIP, where to find information about it and key insights arising from its first two scientific outputs. Future phases of RCMIP will examine specific behaviour of reduced-complexity climate models in more detail, for example their carbon cycle response. We are particulalry keen to hear from users of reduced-complexity models to discuss their use cases, how we can evaluate our models in the way most relevant to them and where key model improvements can be made.
Winter upper-ocean thermohaline variability observed from drifting ice platforms in the Amundsen Basin, Arctic Ocean
Authors: Fang Ying-Chih , Rabe Benjamin , Kuznetsov Ivan , Hoppmann Mario , Tippenhauer Sandra , Schulz Kirstin , Regnery Julia , Janout Markus , Rohde Jan , Belter Jakob , Krumpen Thomas , Nicolaus Marcel ,   MOSAiC Ocean Team
Published: March 2021

We analyzed hydrographic data from several autonomous oceanographic buoys within the MOSAiC Distributed Network together with regular CTD casts from the MOSAiC Central Observatory during the 2019/20 winter in the Amundsen Basin. These drifting platforms can yield as small as ~300 m (or 10 min) horizontal resolution, providing unprecedented perspectives for the (sub)mesoscale dynamics. Full-depth CTD profiles yielded the first baroclinic Rossby radii (R1) of ~7.5 km, which is consistent with previous studies based on climatology. Near-surface layers shallower than the halocline were not always mixed. Restratification was commonly observed, suggesting the onset of baroclinic instabilities and/or eddies emanating from the lateral fronts. A surface-layer eddy with estimated radius of ~5 km was fortuitously observed and coincident with the surrounding mixed geostrophic shear in the vertical, that is, oppositely-sloping isopycnals within the depth range of ~20 – 200 m. This structure is reminiscent of the Charney-type baroclinic instability, resulting from a difference in the sign of the vertical gradient of the interior quasigeostrophic potential vorticity and that of the surface buoyancy forcing. A reconstructed surface dynamic height field supports this argument, showing that submesoscale to mesoscale surface lateral buoyancy gradients are ubiquitous. This result implies that the study domain could be inherently unstable and prone to generate baroclinic eddies. We also observed that the slopes of the density horizontal wavenumber spectra changed at the halocline depths (~40 – 75 m) after a ~3-day storm event with peak speeds ~ 20 m s-1. We hypothesize that such change could be related to the Ekman pumping due to large ice drift (~50 cm s-1) and its resultant stress curl during the storm. Our analyses underline that thinning Arctic sea ice and increasing ice drift could together trigger more oceanic heat flux into the cold halocline by storms, further deteriorating winter ice growth in the Amundsen Basin.
Functional data clustering as a powerful tool to group streamflow regimes and flood hydrographs
Authors: Brunner Manuela Irene , Furrer Reinhard , Gilleland Eric
Published: March 2021

Grouping catchments according to their seasonal streamflow or flood behavior can be essential in regionalization studies, climate impact assessments, or model choice and evaluation. Classical clustering approaches often rely on a selection of indices derived from streamflow/flood hydrographs to identify groups of similar hydrographs and ignore valuable information provided through the temporal (auto-)correlation pattern. To exploit this temporal information, we propose a functional clustering approach to identify catchments with similar streamflow regimes or flood hydrographs. Functional data clustering expresses hydrograph shapes as continuous functions by projecting them onto a set of basis functions (here B-splines) and clusters the resulting basis coefficients using classical clustering algorithms such as hierarchical or k-means clustering.
We apply this functional clustering approach to (1) a large set of catchments in the United States in order to identify regions with similar streamflow regimes and (2) a large set of catchments in Switzerland in order to identify regions with similar flood reactivity. We show that both the streamflow regime and flood reactivity regions are not only similar in terms of their streamflow/hydrograph behavior but also in terms of physiography and climate. We use the streamflow regime clusters derived using functional data clustering to assess future streamflow regime changes in the United States and demonstrate that they are beneficial in climate impact assessments, e.g. to indicate which types of catchments are particularly prone to future change. Further, we use the flood reactivity regions in a regionalization study to derive design hydrographs in ungauged catchments. We conclude that functional clustering approaches are beneficial in climate impact assessments and regionalization studies and might potentially also be valuable to cluster other types of hydrological phenomena such as drought events or long-term streamflow behavior.
Manual point-measurements of sea ice mass balance during the MOSAiC Expedition
Authors: Raphael Ian , Perovich Donald , Polashenski Chris , Clemens-Sewall David , Itkin Polona , Jaggi Matthias , Regnery Julia , Smith Madison , Hutchings Jennifer , Nicolaus Marcel , Matero Ilkka , Wagner David , Oggier Marc , Demir Oguz , Macfarlane Amy , Fons Steven
Published: March 2021

Sea ice plays a critical role in the Arctic climate system, regulating much of the energy transfer between the ocean and the atmosphere. Repeat measurements of ice mass balance at discrete points allow us to determine the direct response of sea ice mass to environmental conditions. We installed a network of mass balance measurement sites across the MOSAiC Central Observatories, distributed over a diverse range of ice types and features. The sites were composed of gridded arrays of 9-17 hotwire thickness gauges, each paired with a surface ablation stake. Seven sites were installed on first year ice, and seven on second or multi year ice, with a total of 120+ individual measurement stations. The sites were operational over different periods throughout the year; several were destroyed or became inaccessible during ridging events. Initial ice thicknesses ranged from 0.13-3.50 m. We made measurements of ice and snow interfaces and thicknesses with 1 cm precision at each station, at intervals of 2-3 weeks during the growth season and as few as 1-2 days during the melt season. From these measurements, we infer ice growth, ice bottom melt, ice surface melt, snow deposition, snow erosion, and snow melt. The time series spans October 2019–September 2020, with a five-week measurement gap beginning mid-May 2020. We present an overview of the measurements and preliminary analysis, partitioning results by ice type and comparing mass balance to concurrent atmosphere and ocean measurements. We identify trends in the seasonal evolution of different ice types, and give particular attention to notable events in the time series. As true point-measurements, the data are especially relevant in improving one-dimensional thermodynamic sea ice models. The results also provide validation for satellite and electromagnetic induction ice-thickness measurements made during MOSAiC, which offer higher areal coverage but lower measurement- and spatial-precision.
Building Australia’s Scalable Drone Cloud
Authors: Klump Jens , Brown Tim , Clarke Rohan , Glasgow Robert , Micklethwaite Steve , Guru Siddeswara , Morris Beryl , Quenette Steve , Rawling Tim , Reid Nathan , Robinson Susie ,   ASDC Project Team
Published: March 2021

Remotely Piloted Aircraft (RPA), commonly known as drones, provide sensing capabilities that address the critical scale-gap between ground- and satellite-based observations. Their versatility allows researchers to deliver near-real-time information for society.

Key to delivering RPA information is the capacity to enable researchers to systematically collect, process, manage and share RPA-borne sensor data. Importantly, this should allow vertical integration across scales and horizontal integration across different RPA deployments. However, as an emerging technology, the best practice and standards are still developing and the large data volumes collected during RPA missions can be challenging.

Australia’s Scalable Drone Cloud (ASDC) aims to coordinate and standardise how scientists from across earth, environmental and agricultural research manage, process and analyse data collected by RPA-borne sensors, by establishing best practices in managing 3D-geospatial data and aligned with the FAIR data principles.

The ASDC is building a cloud-native platform for research drone data management and analytics, driven by exemplar data management practices, data-processing pipelines, and search and discovery of drone data. The aim of the platform is to integrate sensing capabilities with easy-to-use storage, processing, visualisation and data analysis tools (including computer vision / deep learning techniques) to establish a national ecosystem for drone data management.

The ASDC is a partnership of the Monash Drone Discovery Platform, CSIRO and key National Collaborative Research Infrastructure (NCRIS) capabilities including the Australian Research Data Commons (ARDC), Australian Plant Phenomics Facility (APPF), Terrestrial Ecosystem Research Network (TERN), and AuScope.

This presentation outlines the roadmap and first proof-of-concept implementation of the ASDC.
A new perspective on tidal mixing at the Strait of Gibraltar from a very high-resolution model of the Mediterranean Sea
Authors: Gonzalez Nicolas , Waldman Robin , Sannino Gianmaria , Giordani Hervé , Somot Samuel
Published: March 2021

The Strait of Gibraltar is a narrow and shallow channel that controls the thermohaline and biogeochemical balances of the Mediterranean Sea. Exchanges across this strait are known to be significantly modulated by tidal currents that induce an intense vertical mixing. However, the turbulent processes that control the location, timing and magnitude of this vertical mixing are still unclear. Based on twin tidal and non-tidal simulations, we shed light on the tidal mixing at the Strait of Gibraltar, as simulated from a regional configuration of the three-dimensional numerical model MITgcm. The model domain covers the entire Mediterranean basin, the Black Sea and a part of the Atlantic Ocean, using a very high spatial resolution around the Strait of Gibraltar (1/200°). In both simulations we analyse the vertical mixing generated by the model's turbulence closure scheme based on a turbulent kinetic energy budget. As expected, tides strongly intensify the vertical mixing within the Strait of Gibraltar. Tidal currents also induce significant vertical motions that feed recirculation cells between Atlantic and Mediterranean layers. Conversely, the absence of tidal currents causes an overestimation of the velocities along with spurious mixing in the vicinity of the strait. We show that tidal mixing relies on two main ingredients: sustained vertical shear of horizontal velocities and the reduction of stratification, performed by the work of tidal currents against buoyancy forces. We conclude by proposing a revised conceptual view of tidal mixing at the Strait of Gibraltar.
Plastic plants: Long-term monitoring of macroplastic entrapment by water hyacinths in the Saigon river 
Authors: Schreyers Louise , van Emmerik Tim , L. Bui Thanh-Khiet , Biermann Lauren , Le Quang Dung , Janssens Niels , Strady Emily , Hong Quan Nguyen , Duc Tran Dung , van der Ploeg Martine
Published: March 2021

Our recent field-based study undertaken at the Saigon river, Vietnam, shows that water hyacinths are responsible for entraining and transporting a majority of floating macroplastic litter. These invasive, free-floating water plants can form patches of several meters in length and width and tend to aggregate large amounts of plastic litter. Over the course of a six-week study, we demonstrated that 78% of the floating macroplastic observed were carried downstream accumulated within these floating plant patches.

The strong seasonality of water hyacinths, coupled with the temporal variability in macroplastic flux, calls for a longer monitoring effort. To this end, a one-year monitoring campaign is currently being undertaken at the Saigon river, which will apply satellite imagery, drone, camera imagery analysis and visual counting from bridges. Combined, these methods can help to characterize the contribution of hyacinths to macroplastic transport and accumulation at different temporal (from hours/days to weeks/months) and spatial (from sample sites to the river system) scales.

We evaluate the selected monitoring techniques, and present the preliminary results of this large-scale monitoring effort. We provide the first scientific overview of the contribution of water hyacinths in plastic transport relative to the total plastic transport, and its spatiotemporal variability. In addition, we assess the monitoring techniques used and provide suggestions for similar long-term monitoring strategies.
Impact of Climate Variability and Land Use Change on Surface Hydrological Processes in the Hilly-Gully Region of the Loess Plateau, China
Authors: Kang Youcai , Gao Jianen , Shao Hui , Zhang Yuanyuan
Published: March 2021

Abstract: Climate and land-use change are the two main driving forces that affect watershed hydrological processes. Separately assessing the impacts of climate and land use change on hydrology is important for water resource management. In this research, the SWAT (Soil and Water Assessment Tool) and statistical methods were employed to evaluate the effects of climate and land-use change on surface hydrology in the hilly-gully region of the Loess Plateau. The results showed that both the temperature and potential evapotranspiration (PET) had significant upward trends (p < 0.05), while the precipitation presented a slightly downward trend in the Yanhe watershed during 1982-2012. The contribution of precipitation to streamflow is concentrated in the flooding periods (from July to September), the average contribution rate of surface runoff on stream flow accounted for 55%, of which the flooding period accounted for 40%. With the 2.17% of slope farmland transformed to the forest and grassland, the average runoff coefficient decreased from 0.36 to 0.15 during 1982-2012. The impact of land use change on soil water content is mainly happened in the upstream stream, while the dominated factor converted to climate from northwest to southeast in the Yanhe watershed. The Evapotranspiration was more sensitive to land-use change than climate variability in all sub-basins, and increased by 209% with vegetation restoration in the Yanhe watershed. Therefore, the impacts of climate variation and land use change on surface hydrological processes were heterogeneity in different geographical regions, climate is the main factor to influence the runoff, while the land use is the dominated factor to evapotranspiration. The quantitative assessment the influence of climate variability and land-use change on hydrology can provide insight into the extent of land use/cover change on regional water balance, and develop appropriate watershed management strategies on the Loess Plateau.

Keywords: climate shift, human activities, hydrological processes, SWAT, the Loess Plateau

Funding: This study was funded by the National Natural Science Foundation of China (No. 41877078, 41371276), Key research and development project of Shaanxi Province (2020ZDLSF06-03-01), National Key Research and Development Program of China (No. 2017YFC0504703) and Knowledge Innovation Program of the Chinese Academy of Sciences (No. A315021615).

 
Assessment of the resilience to flood of a complex system: the case of densely populated city
Authors: Arosio Marcello , Cesarini Luigi , Martina Mario L.V.
Published: March 2021

In the last decades, resilience officially become the worldwide cornerstone around which reducing the risk of disasters and improving preparedness, response and recovery capacities. The theoretical framework developed in this work is based on the resilience definition adopted in 2016 by United Nations General Assembly: “the ability of a system, community or society exposed to hazards to resist, absorb, accommodate, adapt to, transform and recover from the effects of a hazard in a timely and efficient manner, including through the preservation and restoration of its essential basic structures and functions through risk management”. This definition implies 2 main concepts that are the foundation of this work: 1) resilience is a property of a system and 2) a system is resilient when is able to dynamically react to a perturbation in order to maintain or resume its functionalities.

In order to reproduce the complex system of an urban environment, the proposed framework shows the assumptions and operational procedure to construct a weighted and redundant graph. The built graph has the ambition, under the constrains due to the data availability, to represent the interdependencies among the exposed elements, both in ordinary conditions and under perturbations such as disasters. The weight of the graph is represented by the population served by each single service. Furthermore, each element in case of an external perturbation, has the possibility to dynamically adapt and switch to a new graph configuration based on the redundancy and backup capacity of its providers.

The feasibility of the proposed approach is illustrated by an application to a case study in the densely populated urban environment of the city of Monza that is exposed to river and pluvial floods. The case study consists in a directed and weighted graph with 6000+ nodes and almost 1.3 million links. By means of the graph an estimation of the impacted and adapted nodes is made along with a measure of resilience to different flood scenarios for the city of Monza

Acknowledge: This research was partly funded by Fondazione Cariplo under the project “NEWFRAME: NEtWork-based Flood Risk Assessment and Management of Emergencies"
Digital rock physics: A geological driven segmentation workflow for Ruhr sandstone
Authors: Balcewicz Martin , Siegert Mirko , Gurris Marcel , Krach David , Ruf Matthias , Steeb Holger , Saenger Erik H.
Published: March 2021

Over the last two decades, Digital Rock Physics (DRP) has become a complementary part of the characterization of reservoir rocks due to, among other things, the non-destructive testing character of this technique. The use of high-resolution X-ray Computed Tomography (XRCT) has become widely accepted to create a digital twin of the material under investigation. Compared to other imaging techniques, XRCT technology allows a location-dependent resolution of the individual material particles in volume. However, there are still challenges in assigning physical properties to a particular voxel within the digital twin, due to standard histogram analysis or sub-resolution features in the rock. For this reason, high-resolution image-based data from XRCT, transmitted-light microscope, Scanning Electron Microscope (SEM) as well as inherent material properties like porosity are combined to obtain an optimal spatial image of the studied Ruhr sandstone by a geologically driven segmentation workflow. On the basis of a homogeneity test, which corresponds to the evaluation of the grayscale image histogram, the preferred scan sample sizes in terms of transport, thermal, and effective elastic rock properties are determined. In addition, the advanced numerical simulation results are compared with laboratory tests to provide possible upper limits for sample size, segmentation accuracy, and a calibrated digital twin of the Ruhr sandstone. The comparison of representative grayscale image histograms as a function of sample sizes with the corresponding advanced numerical simulations, provides a unique workflow for reservoir characterization of the Ruhr sandstone.
Numerical modeling of hydro-mechanical coupled effects in the cyclic deformation (CD-A) experiment: First results and comparison with observations
Authors: Cajuhi Tuanny , Ziefle Gesa , Maßmann Jobst , Furche Markus
Published: March 2021

The Mont Terri rock laboratory is situated in a clay formation in the northwestern part of Switzerland and is the place of several research focused experiments. These experiments enable the study of relevant coupled effects in the Opalinus Clay formation, an important material in the context of radioactive waste management due to its possible use as geological barrier. Our study focuses on the cyclic deformation (CD-A) experiment, which aims at investigating the coupled hydro-mechanical (HM) behavior of the material, e.g. shrinkage, swelling, changes in permeability. These processes can affect the stability and integrity of the rock. The experiment encompasses seasonal variations such as natural cyclic humidity changes due to winter and summer and consists of two niches. While one niche is open to the influence of the surroundings and hence, subjected to the effects of the seasonal changes of air humidity, the other niche is kept under controlled, high humidity conditions. Long-term quasi-continuous as well as repeating measurements for parameters such as relative humidity, water content, temperature, electrical resistivity and deformation, e.g. tunnel wall convergence via laser scans, are carried out amongst others (start in October 2019). These monitoring data are used as input for calibration and validation of numerical models.

In this contribution we numerically model the HM coupled effects in the context of the CD-A experiment using a macroscopic poromechanical approach. The mathematical model consists of the mass balance of the solid and the liquid phases with displacements and pore pressure as independent variables. Furthermore, it considers unsaturated flow by the Richards approximation. The model is solved numerically with the finite element method using the open-source software OpenGeoSys (OGS 6). Based on a literature review on the material properties of the clay sandy facies and experimental data, a two-dimensional model has been setup stepwise considering (i) in-situ initial pore water pressures and stresses, (ii) the effect of excavation, (iii) the experimentally based seasonal climatic conditions in the niches and (iv) the effect of bedding-induced anisotropy on the HM coupled behavior. With this numerical investigation, we evaluate the temporal evolution of the unsaturated zone. The Nuclear Magnetic Resonance (NMR), Electric Resistivity Tomography (ERT) and Taupe measurements indicate the spatial and temporal evolution of the seasonal hydraulic effects near the niches within the first experimental year. A first comparative study indicates qualitative agreement between monitored ERT data and simulation results and offers paths for model improvement and extension such as in the context of shrinkage-induced cracking.
Bedymo: a combined quasi-geostrophic and primitive equation model in sigma coordinates
Authors: Spensberger Clemens , Spengler Thomas
Published: March 2021

We introduce the idealised atmospheric circulation model Bedymo, which combines the quasi-geostrophic approximation and the hydrostatic primitive equations in one modelling framework. The model is designed such that the two systems of equations are solved as similarly as possible, such that differences can be unambiguously attributed to the different approximations, rather than the model formulation or the numerics. Using either approximation, Bedymo successfully simulates a mid-latitude atmospheric storm track and the stationary wave response to orographic forcing or diabatic heating.

In addition to the atmospheric core, Bedymo also includes a slab ocean model and passive tracer module that could provide the basis for an idealised parametrisation of moisture and latent heat release. Further, Bedymo has a graphical user interface, making it particularly useful in teaching.

In contrast to most other quasi-gestrophic models, Bedymo is using sigma-coordinates in the vertical. This is unique as it ensures mass continuity within the model domain and allows a more direct inclusion of orography. We point out several insights and potential pitfalls when deriving quasi-geostrophy in sigma-coordinates and show that it is possible to obtain a self-consistent set of equations.
Soil moisture estimation over cereals fields using l-band alos2 data (merguellil case – KAIROUAN)
Authors: Ayari Emna , Kassouk Zeineb , Lili Chabaane Zohra , Bousbih Safa , Zribi Mehrez
Published: March 2021

Soil moisture is a key component for water resources management especially for irrigation needs estimation. We analyze in the present study, the potential of L-band data, acquired by (Advanced Land Observing Satellite-2) ALOS-2, to retrieve soil moisture over bare soils and cereal fields located in semi-arid area in the Kairouan plain.

In this context, we evaluate radar signal sensitivity to roughness, soil moisture and vegetation biophysical parameters. Based on multi-incidence radar data (28°, 32.5° and 36°), high correlations characterize relationships between backscattering coefficients in dual-polarization (HH and HV) and root mean square of heights (Hrms) and Zs, parameters, Sensitivity of radar data to soil moisture was discussed for three classes of NDVI (less than 0.25 for bare soils and dispersed vegetation, between 0.25 and 0.5 for medium vegetation and greater than 0.5 for dense cereals). With vegetation development, where NDVI values are higher than 0.25, SAR signal remains sensitive to soil moisture in HH pol. This sensitivity to moisture disappears, in HV pol for dense vegetation. For covered fields, L-band signal is very sensitive to Vegetation Water Content (VWC), with R² values ranging between 0.76 and 0.61 in HH and HV polarization respectively.

Simulating signal behavior is carried out through various models over bare soils and covered cereal fields. Over bare soils, proposed empirical expressions, modified versions of Integral Equation Model (IEM-B) and Dubois models (Dubois-B) are evaluated, generally for HH and HV polarizations. Best consistency is observed between real data and IEM-B backscattering simulations in HH polarization. More discrepancies between real and modelled data are observed in HV polarization.

Furthermore, to simulate L-band signal behavior over covered fields, the inversion of Water Cloud Model (WCM) coupled to different bare soil models is realized through direct equations and Look-up tables. Two options of WCM, are tested (with and without soil-vegetation interaction scattering term). For the first option, results highlight the good performance of IEM-B coupled to WCM in HH polarization with RMSE value between estimated and in situ moisture measurements equal to 4.87 vol.%. By adding soil – cereal interaction term in the second option of WCM, results reveal a stable accuracy in HH polarization and an important improvement of soil moisture estimations in HV polarization, with RMSE values are ranging between 6 and 7 vol.%.
Assessment of the sorption capacity of PET microparticles in natural water with respect to metals
Authors: Kulik Natalia , Efremenko Natalia
Published: March 2021

Contamination of the World Oceans with microplastics (MPs) is one of the most discussed environmental problems of the last decade. MPs are able to accumulate on their surface pollutants present in water in very low concentrations. Concentrations of pollutants, such as metals, can reach values that exceed the natural background in water bodies.Thus, MPs can act as a secondary source of contamination of water bodies with metals.The sorption capacity of artificially grinded and aged in the natural environment microparticles of polyethylene terephthalate (PET) with respect to metals in the natural water of Lake Onego was assessed in laboratory conditions.The Total Content method was used to characterize the sorption process and to obtain the dependence of the concentration of a substance in the stationary phase on its concentration in the mobile phase (experimental sorption isotherms were obtained). Subsequent mathematical processing of the experimentally obtained metal sorption isotherms on PET for Mn, Ni, Cu, Cd, and Pb allowed us to determine the monolayer capacities, adsorption equilibrium constants, and adsorption values at the equilibrium adsorbate concentration for each of the studied metals. This information is valuable to assess the role of MPs in metals transport in water bodies. The study was supported by the Russian Science Foundation grant number 19-17-00035.
Long-term future projections for the Greenland and Antarctic ice sheets with the model SICOPOLIS
Authors: Greve Ralf , Chambers Christopher , Calov Reinhard , Obase Takashi , Saito Fuyuki , Harada Kaho , Abe-Ouchi Ayako
Published: March 2021

The Coupled Model Intercomparison Project Phase 6 (CMIP6) is a major international climate modelling initiative. As part of it, the Ice Sheet Model Intercomparison Project for CMIP6 (ISMIP6) was devised to assess the likely sea-level-rise contribution from the Greenland and Antarctic ice sheets until the year 2100. This was achieved by defining a set of future climate scenarios by evaluating results of CMIP5 and CMIP6 global climate models (GCMs, including MIROC) over and surrounding the Greenland and Antarctic ice sheets. These scenarios were used as forcings for a variety of ice-sheet models operated by different working groups worldwide (Goelzer et al. 2020, doi: 10.5194/tc-14-3071-2020; Seroussi et al. 2020, doi: 10.5194/tc-14-3033-2020).

Here, we use the model SICOPOLIS to carry out extended versions of the ISMIP6 future climate experiments for the Greenland and Antarctic ice sheets until the year 3000. For the atmospheric forcing (anomalies of surface mass balance and temperature) beyond 2100, we sample randomly the ten-year interval 2091-2100, while the oceanic forcing beyond 2100 is kept fixed at 2100 conditions. We conduct experiments for the pessimistic, "business as usual" pathway RCP8.5 (CMIP5) / SSP5-8.5 (CMIP6), and for the optimistic RCP2.6 (CMIP5) / SSP1-2.6 (CMIP6) pathway that represents substantial emissions reductions. For the unforced, constant-climate control runs, both ice sheets are stable until the year 3000. For RCP8.5/SSP5-8.5, they suffer massive mass losses: For Greenland, ~1.7 m SLE (sea-level equivalent) for the 12-experiment mean, and ~3.5 m SLE for the most sensitive experiment. For Antarctica, ~3.3 m SLE for the 14-experiment mean, and ~5.3 m SLE for the most sensitive experiment. For RCP2.6/SSP1-2.6, the mass losses are limited to a two-experiment mean of ~0.26 m SLE for Greenland, and a three-experiment mean of ~0.25 m SLE for Antarctica. Climate-change mitigation during the next decades will therefore be an efficient means for limiting the contribution of the ice sheets to sea-level rise in the long term.
Magnetosheath high speed jets and foreshock transients observed by Cluster and MMS
Authors: Escoubet C.-Philippe ,   Cluster-MMS team
Published: March 2021

Magnetosheath High Speed Jets (HSJs) are regularly observed downstream of the Earth’s bow shock. Determining their origin from spacecraft observations is however a challenge since (1) L1 solar wind monitors are usually used with their inherent inaccuracy when plasma and magnetic data are propagated to the bow shock, (2) the number of measurement points around the bow shock are always limited. Various mechanisms have been proposed to explain HSJs such as bow shock ripples, solar wind discontinuities, foreshock transients, pressure pulses or nano dust clouds and it is difficult to relate these to HSJs with the lack of simultaneous measurements near the bow shock and immediately upstream.  We will use a special Cluster campaign, where one spacecraft was lagged 8 hours behind the three other spacecraft, to obtain near-Earth solar wind measurements upstream of the bow shock, together with simultaneous measurements in the magnetosheath. The event of interest is first observed by ACE on 13 January 2019 as a short 10 minutes period of IMF-Bx dominant (cone angle around 140 deg.). This IMF-Bx dominant period is also observed, one hour later, by THEMIS B and C (ARTEMIS) and Geotail, which were at 60 and 25 RE from Earth on the dawnside. Cluster 1 and Cluster 2 just upstream of the bow shock, at 17 RE from Earth, observed also such IMF-Bx dominant period together with energetic ions reflected from the bow shock and foreshock transients. Preliminary analysis indicate that these transients would be hot flow anomalies. Finally, Cluster 3 and 4 and MMS1-4, a few RE from each other downstream of the shock, observed a turbulent magnetosheath with HSJs for 15 minutes. The HSJ characteristics are investigated with the constellation of 6 spacecraft, as well as their relation to hot flows anomalies observed upstream.
Modelling the effect of mechanical deformation on the peatland carbon stock resilience
Authors: Mahdiyasa Adilan , Large David , Muljadi Bagus , Icardi Matteo
Published: March 2021

Mathematical models of peatland growth have been developed for many purposes, including understanding the effect of past or future climate change on peatland carbon accumulation. This is important because peatland contains a vast amount of carbon and has a significant role in the global carbon cycle through carbon dioxide and methane exchange with the atmosphere. In general, the models produced so far suffer from the fact that the mechanical process has an essential role in the peatland carbon stock resilience because they only focus on ecohydrological feedback. We propose a one-dimensional mathematical model that includes ecological, hydrological, and mechanical feedback on the peatland through the poroelasticity concept, which coupling between fluid flow and solid deformation. The formulation is divided into two categories, fully saturated and unsaturated, to accommodate peatland characteristics. We compare the numerical solution of the fully saturated case with analytical solutions of Terzaghi’s problem for validation. We assume that peat is an elastic material with flat, impermeable, and stiff substrate properties.  Based on the initial simulation results,  we find that compression reduces the thickness of acrotelm, leading to the shorter residence time of plant litter, and consequently, higher cumulative carbon is obtained. Furthermore, mechanical deformation of the pore structure effectively maintains carbon stock in the peatland against climate change because it reduces water table depth fluctuations.
Role of rigid block in tectonic transformation zone at east Tibet 
Authors: Shen Tuo , Xu Xiwei , Zhou Shiyong , Wei Shaogang , Lei Xiaoqiong
Published: March 2021

In recent decades, plateau margins have attracted attention because the understanding of their dynamics and history provides insights into the modes of crustal deformation responsible for the plateau structure and morphology and more widely into the deformation of continental lithosphere. The slip transformation and strain partitioning mechanism at the eastern termination of the Kunlun fault system remain unclear. Geophysics investigations revealed the Ruoergai Basin as a rigid block; however, insufficient information is available on the role of this block in tectonic transformation zone at east Tibet. We employed the finite element method in our simulations to delimitate the presence of the Ruoergai block and determine how it affects the surrounding area. We found that the Ruoergai block moves independently to the east or northeast, and its motion differs from that of the Bayan Har block in the eastward escape process of this last-named block. The formation and behavior of Awancang fault and Longriba fault seems to impact by the Ruoergai block. The influence of the Ruoergai block in the east margin should not be ignored. The Awancang fault and Ruoergai block absorbed the north vector velocity of the Bayan Har block, after which the Bayan Har block started moving southeast. The strain partitioning at the eastern margin of the Tibet Plateau is progressively complete[A1]  from the Awancang fault, Ruoergai block, and Longriba fault area to the Longmenshan block. The presence of the Ruoergai block could decrease the strike-slip rate of the Maqin–Maqu section of the Kunlun fault. Given its influence in the region, the Ruoergai block should be incorporated in future studies on regional deformation and in deformation and tectonic transformation models. Then we compared the deformation and tectonic transformation models in the northern margin of the Tibet Plateau. Proposed a rigid block compression pattern unite the tectonic transformation and deformation issue, further explain most of the fault behaviors in the northern margin and eastern margin of Tibet.

 
Numerical Analysis of the Induced Seismicity Triggered by Hydraulic Fracturing in the Duvernay Formation in Alberta, CA
Authors: Yassine Dima , Yehya Alissar , Maalouf Elsa
Published: March 2021

In the past decades, induced seismicity has become a major concern due to its correlation with oil and gas production and wastewater disposal. Unlike the induced seismicity observed in the United States that is associated with massive saltwater disposal, the induced seismicity observed in the Duvernay formation, a shale target in Alberta, Western Canada, is associated with hydraulic fracturing operations. In this work, we explore the possible mechanisms and the hydro-geological factors responsible for the seismic events that occurred between 2014 and 2015 in the Duvernay formation. By a two-dimensional finite element poroelastic model, using COMSOL Multiphysics, we couple fluid flow and solid deformation to estimate the change in the Coulomb Failure Stress (CFS) along two critically stressed faults existing near the hydraulic fracturing operations. One fault (Fault 1) is 1.01 km away from the location of hydraulic fractures while the second fault (Fault 2) is 0.425 km below the location of hydraulic fractures. The variations of the CFS along the two pre-existing faults are analyzed and compared to the seismic events obtained from the observational data in the Duvernay formation from December 2014 to March 2015 (Bao & Eaton, 2016). Our results show that most of the seismic events correlate spatially and temporally with positive CFS values that imply a risk of failure. During the early stages of hydraulic fracturing, the triggering failure mechanism of “Fault 1” is the increase in the shear stress on portions of the fault that are under extension and that of “Fault 2” is the pore pressure diffusion. Moreover, the distance between the centers of the two faults must range between 1.5 km and 2 km for the CFS results to agree with the observed seismic events. Under this condition, the shallower sections of “Fault 1” are under compression and show a stabilizing behavior (i.e., negative CFS) that is confirmed by the lack of seismic events from observational data, and the deeper sections of “Fault 1” are under extension and show a destabilizing behavior (i.e., positive CFS), which correlates with the measured seismic events. If the distance between “Fault 1” and “Fault 2” is less than 1.5 km, the shallower section of “Fault 1” would be destabilized by the effect of pore pressure, which does not agree with the observed seismic data. Moreover, if the distance between “Fault 1” and “Fault 2” is greater than 2 km, “Fault 1” would be entirely stabilized. Hence, the position of the faults with respect to the location of the hydraulic fracturing operations played an important role in the induced earthquakes triggering mechanisms and in the spatiotemporal distribution of the seismic events.