scholarly journals A generalized stress correction scheme for the MEB rheology: impact on the fracture angles and deformations

2021 ◽  
Author(s):  
Mathieu Plante ◽  
L. Bruno Tremblay
Keyword(s):  
Stress Tensor ◽  
Yield Curve ◽  
Elastic Response ◽  
The Arctic ◽  
Critical Stresses ◽  
Fracture Deformation ◽  
Correction Scheme ◽  
Simulated Material ◽  
Residual Errors

Abstract. A generalized damage parameterization is developed for the Maxwell Elasto-Brittle (MEB) rheology that reduces the growth of residual errors associated with the correction of super-critical stresses. In the generalized stress correction, a decohesive stress tensor is used to bring the super-critical stresses back on the yield curve based on any correction path. The sensitivity of the simulated material behaviour to the magnitude of the decohesive stress tensor is investigated in uniaxial compression simulations. Results show that while the decohesive stress tensor influences the short-term fracture deformation and orientation, the long-term post-fracture behaviour remains unchanged. Divergence first occurs when the elastic response is dominant followed by post-fracture shear and convergence when the viscous response dominates – contrary to laboratory experiment of granular flow and satellite imagery in the Arctic. The post-fracture deformations are shown to be dissociated from the fracture process itself, an important difference with classical Viscous Plastic (VP) models. Using the generalized damage parameterization together with a stress correction path normal to the yield curve brings the simulated fracture angles closer to observations (from 40–50° to 35–45°, compared to 20–30° in observations) and reduces the growth of errors sufficiently for the production of longer-term simulations.

scholarly journals A generalized stress correction scheme for the Maxwell elasto-brittle rheology: impact on the fracture angles and deformations

2021 ◽  
Vol 15 (12) ◽  
pp. 5623-5638
Author(s):  
Mathieu Plante ◽  
L. Bruno Tremblay
Keyword(s):  
Sea Ice ◽  
Stress Tensor ◽  
Yield Curve ◽  
Yield Criterion ◽  
Elastic Response ◽  
The Arctic ◽  
Critical Stresses ◽  
Correction Scheme ◽  
Added Benefit

Abstract. The Maxwell elasto-brittle (MEB) rheology uses a damage parameterization to represent the brittle fracture of sea ice without involving plastic laws to constrain the sea ice deformations. The conventional MEB damage parameterization is based on a correction of super-critical stresses that binds the simulated stress to the yield criterion but leads to a growth of errors in the stress field. A generalized damage parameterization is developed to reduce this error growth and to investigate the influence of the super-critical stress correction scheme on the simulated sea ice fractures, deformations and orientation of linear kinematic features (LKFs). A decohesive stress tensor is used to correct the super-critical stresses towards different points on the yield curve. The sensitivity of the simulated sea ice fractures and deformations to the decohesive stress tensor is investigated in uniaxial compression experiments. Results show that the decohesive stress tensor influences the growth of residual errors associated with the correction of super-critical stresses, the orientation of the lines of fracture and the short-term deformation associated with the damage, but it does not influence the long-term post-fracture sea ice deformations. We show that when ice fractures, divergence first occurs while the elastic response is dominant, and convergence develops post-fracture in the long term when the viscous response dominates – contrary to laboratory experiments of granular flow and satellite imagery in the Arctic. The post-fracture deformations are shown to be dissociated from the fracture process itself, an important difference with classical viscous plastic (VP) models in which large deformations are governed by associative plastic laws. Using the generalized damage parameterization together with a stress correction path normal to the yield curve reduces the growth of errors sufficiently for the production of longer-term simulations, with the added benefit of bringing the simulated LKF intersection half-angles closer to observations (from 40–50 to 35–45∘, compared to 15–25∘ in observations).

scholarly journals Non-normal flow rules affect fracture angles in sea ice viscous–plastic rheologies

2021 ◽  
Vol 15 (6) ◽  
pp. 2873-2888
Author(s):  
Damien Ringeisen ◽  
L. Bruno Tremblay ◽  
Martin Losch
Keyword(s):  
Sea Ice ◽  
Axial Compression ◽  
Yield Curve ◽  
Axial Loading ◽  
The Arctic ◽  
Flow Rule ◽  
Normal Flow ◽  
Fracture Deformation ◽  
Plastic Potential ◽  
Ice Model

Abstract. The standard viscous–plastic (VP) sea ice model with an elliptical yield curve and a normal flow rule has at least two issues. First, it does not simulate fracture angles below 30∘ in uni-axial compression, in contrast with observations of linear kinematic features (LKFs) in the Arctic Ocean. Second, there is a tight, but unphysical, coupling between the fracture angle, post-fracture deformation, and the shape of the yield curve. This tight coupling was identified as the reason for the overestimation of fracture angles. In this paper, these issues are addressed by removing the normality constraint on the flow rule in the standard VP model. The new rheology is tested in numerical uni-axial loading tests. To this end, an elliptical plastic potential – which defines the post-fracture deformations, or flow rule – is introduced independently of the elliptical yield curve. As a consequence, the post-fracture deformation is decoupled from the mechanical strength properties of the ice. We adapt Roscoe's angle theory, which is based on observations of granular materials, to the context of sea ice modeling. In this framework, the fracture angles depend on both yield curve and plastic potential parameters. This new formulation predicts accurately the results of the numerical experiments with a root-mean-square error below 1.3∘. The new rheology allows for angles of fracture smaller than 30∘ in uni-axial compression. For instance, a plastic potential with an ellipse aspect ratio smaller than 2 (i.e., the default value in the standard viscous–plastic model) can lead to fracture angles as low as 22∘. Implementing an elliptical plastic potential in the standard VP sea ice model requires only small modifications to the standard VP rheology. The momentum equations with the modified rheology, however, are more difficult to solve numerically. The independent plastic potential solves the two issues with VP rheology addressed in this paper: in uni-axial loading experiments, it allows for smaller fracture angles, which fall within the range of satellite observations, and it decouples the angle of fracture and the post-fracture deformation from the shape of the yield curve. The orientation of the post-fracture deformation along the fracture lines (convergence and divergence), however, is still controlled by the shape of the plastic potential and the location of the stress state on the yield curve. A non-elliptical plastic potential would be required to change the orientation of deformation and to match deformation statistics derived from satellite measurements.

Diatoms and aquatic palynomorphs in the sediments of the Eurasian Arctic seas and their significance for paleooceanological investigations in the Arctic

2019 ◽  
pp. 246-251
Author(s):  
Yelena I. Polyakova ◽  
Yekaterina I. Novichkova ◽  
Tatiana S. Klyuvitkina ◽  
Elizaveta A. Agafonova ◽  
Irina M. Kryukova
Keyword(s):  
Bering Sea ◽  
Surface Sediments ◽  
Sea Water ◽  
The Arctic ◽  
Marginal Filter ◽  
Arctic Seas ◽  
Hydrological Parameters ◽  
The Arctic Ocean ◽  
Long Term Studies

Presented the results of long-term studies of diatoms and aquatic palynomorphs in surface sediments of the Arctic seas and the possibility of their use for the reconstructions of paleocirculation water masses, advection of Atlantic and Bering sea water into the Arctic ocean, changes in the river runoff to the seas, sedimentary processes in the marginal filter of the largest rivers, seasonal sea ice cover and other hydrological parameters.

Trends and Prospects of Development of the Oil and Gas Sector in the Context of Digitalization

2020 ◽  
Vol 26 (1) ◽  
pp. 35-45 ◽  
Author(s):  
A. G. Kazanin
Keyword(s):  
Oil And Gas ◽  
Digital Technologies ◽  
Oil And Gas Industry ◽  
Global Market ◽  
The Arctic ◽  
Business And Society ◽  
Gas Industry ◽  
Exploration And Production ◽  
Oil And Gas Sector

The modern oil and gas industry is heavily dependent on the processes and trends driven by the accelerating digitalization of the economy. Thus, the digitalization of the oil and gas sector has become Russia’s top priority, which involves a technological and structural transformation of all production processes and stages.Aim. The presented study aims to identify the major trends and prospects of development of the Russian oil and gas sector in the context of its digitalization and formation of the digital economy.Tasks. The authors analyze the major trends in the development of the oil and gas industry at a global scale and in Russia with allowance for the prospects of accelerated exploration of the Arctic; determine the best practices of implementation of digital technologies by oil and gas companies as well as the prospects and obstacles for the subsequent transfer of digital technologies to the Russian oil and gas industry.Methods. This study uses general scientific methods, such as analysis, synthesis, and scientific generalization.Results. Arctic hydrocarbons will become increasingly important to Russia in the long term, and their exploration and production will require the implementation of innovative technologies. Priority directions for the development of many oil and gas producers will include active application of digital technologies as a whole (different types of robots that could replace people in performing complex procedures), processing and analysis of big data using artificial intelligence to optimize processes, particularly in the field of exploration and production, processing and transportation. Digitalization of the oil and gas sector is a powerful factor in the improvement of the efficiency of the Russian economy. However, Russian companies are notably lagging behind in this field of innovative development and there are problems and high risks that need to be overcome to realize its potential for business and society.Conclusions. Given the strategic importance of the oil and gas industry for Russia, its sustainable development and national security, it is recommendable to focus on the development and implementation of digital technologies. This is crucial for the digitalization of long-term projection and strategic planning, assessment of the role and place of Russia and its largest energy companies in the global market with allowance for a maximum number of different internal and external factors.

scholarly journals Microplastic contamination of the drilling bivalve Hiatella arctica in Arctic rhodolith beds

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Sebastian Teichert ◽  
Martin G. J. Löder ◽  
Ines Pyko ◽  
Marlene Mordek ◽  
Christian Schulbert ◽  
...  
Keyword(s):  
Polyethylene Terephthalate ◽  
Water Depth ◽  
The Arctic ◽  
Polymer Composition ◽  
Bivalve Species ◽  
Filter Feeder ◽  
Hiatella Arctica ◽  
Long Term Consequences ◽  
Water Depths

AbstractThere is an increasing number of studies reporting microplastic (MP) contamination in the Arctic environment. We analysed MP abundance in samples from a marine Arctic ecosystem that has not been investigated in this context and that features a high biodiversity: hollow rhodoliths gouged by the bivalve Hiatella arctica. This bivalve is a filter feeder that potentially accumulates MPs and may therefore reflect MP contamination of the rhodolith ecosystem at northern Svalbard. Our analyses revealed that 100% of the examined specimens were contaminated with MP, ranging between one and 184 MP particles per bivalve in samples from two water depths. Polymer composition and abundance differed strongly between both water depths: samples from 40 m water depth showed a generally higher concentration of MPs and were clearly dominated by polystyrene, samples from 27 m water depth were more balanced in composition, mainly consisting of polyethylene, polyethylene terephthalate, and polypropylene. Long-term consequences of MP contamination in the investigated bivalve species and for the rhodolith bed ecosystem are yet unclear. However, the uptake of MPs may potentially impact H. arctica and consequently its functioning as ecosystem engineers in Arctic rhodolith beds.

scholarly journals Human–environment interactions at a short-lived Arctic mine and the long-term response of the local tundra vegetation

Polar Record ◽  
2021 ◽  
Vol 57 ◽  
Author(s):  
Frigga Kruse ◽  
Gary R. Nobles ◽  
Martha de Jong ◽  
Rosanne M. K. van Bodegom ◽  
G. J. M. (Gert) van Oortmerssen ◽  
...  
Keyword(s):  
Isotope Analysis ◽  
Isotopic Analysis ◽  
The Arctic ◽  
Human Environment ◽  
Habitat Creation ◽  
Waste Dumps ◽  
Threatened Plant Species ◽  
Visual Impact ◽  
Local Ecosystem

Abstract Arctic mining has a bad reputation because the extractive industry is often responsible for a suite of environmental problems. Yet, few studies explore the gap between untouched tundra and messy megaproject from a historical perspective. Our paper focuses on Advent City as a case study of the emergence of coal mining in Svalbard (Norway) coupled with the onset of mining-related environmental change. After short but intensive human activity (1904–1908), the ecosystem had a century to respond, and we observe a lasting impact on the flora in particular. With interdisciplinary contributions from historical archaeology, archaeozoology, archaeobotany and botany, supplemented by stable isotope analysis, we examine 1) which human activities initially asserted pressure on the Arctic environment, 2) whether the miners at Advent City were “eco-conscious,” for example whether they showed concern for the environment and 3) how the local ecosystem reacted after mine closure and site abandonment. Among the remains of typical mining infrastructure, we prioritised localities that revealed the subtleties of long-term anthropogenic impact. Significant pressure resulted from landscape modifications, the import of non-native animals and plants, hunting and fowling, and the indiscriminate disposal of waste material. Where it was possible to identify individual inhabitants, these shared an economic attitude of waste not, want not, but they did not hold the environment in high regard. Ground clearances, animal dung and waste dumps continue to have an effect after a hundred years. The anthropogenic interference with the fell field led to habitat creation, especially for vascular plants. The vegetation cover and biodiversity were high, but we recorded no exotic or threatened plant species. Impacted localities generally showed a reduction of the natural patchiness of plant communities, and highly eutrophic conditions were unsuitable for liverworts and lichens. Supplementary isotopic analysis of animal bones added data to the marine reservoir offset in Svalbard underlining the far-reaching potential of our multi-proxy approach. We conclude that although damaging human–environment interactions formerly took place at Advent City, these were limited and primarily left the visual impact of the ruins. The fell field is such a dynamic area that the subtle anthropogenic effects on the local tundra may soon be lost. The fauna and flora may not recover to what they were before the miners arrived, but they will continue to respond to new post-industrial circumstances.

A Note Concerning the Dynamics of Government Bond Yields

2021 ◽  
pp. 056943452098827
Author(s):  
Tanweer Akram
Keyword(s):  
Interest Rate ◽  
Financial Markets ◽  
Yield Curve ◽  
Empirical Studies ◽  
State Theory ◽  
Government Bond ◽  
Bond Yields ◽  
Short Term ◽  
Government Bonds

Keynes argued that the central bank can influence the long-term interest rate on government bonds and the shape of the yield curve mainly through the short-term interest rate. Several recent empirical studies that examine the dynamics of government bond yields not only substantiate Keynes’s view that the long-term interest rate responds markedly to the short-term interest rate but also have relevance for macroeconomic theory and policy. This article relates Keynes’s discussions of money, the state theory of money, financial markets, investors’ expectations, uncertainty, and liquidity preference to the dynamics of government bond yields for countries with monetary sovereignty. Investors’ psychology, herding behavior in financial markets, and uncertainty about the future reinforce the effects of the short-term interest rate and the central bank’s monetary policy actions on the long-term interest rate. JEL classifications: E12; E40; E43; E50; E58; E60; F30; G10; G12; H62; H63

Exceptional long-term starvation ability and sites of lipid storage of the Arctic pteropod Clione limacina

Polar Biology ◽  
2006 ◽  
Vol 30 (5) ◽  
pp. 571-580 ◽  
Author(s):  
Marco Böer ◽  
Martin Graeve ◽  
Gerhard Kattner
Keyword(s):  
Lipid Storage ◽  
The Arctic ◽  
Clione Limacina

scholarly journals The influence of the lunar nodal cycle on Arctic climate

2006 ◽  
Vol 63 (3) ◽  
pp. 401-420 ◽  
Author(s):  
Harald Yndestad
Keyword(s):  
Time Series ◽  
Signal To Noise Ratio ◽  
Phase Relationship ◽  
Harmonic Spectrum ◽  
Arctic Climate ◽  
The Arctic ◽  
Major Influence ◽  
Sea Temperature ◽  
Arctic Ice

Abstract The Arctic Ocean is a substantial energy sink for the northern hemisphere. Fluctuations in its energy budget will have a major influence on the Arctic climate. The paper presents an analysis of the time-series for the polar position, the extent of Arctic ice, sea level at Hammerfest, Kola section sea temperature, Røst winter air temperature, and the NAO winter index as a way to identify a source of dominant cycles. The investigation uses wavelet transformation to identify the period and the phase in these Arctic time-series. System dynamics are identified by studying the phase relationship between the dominant cycles in all time-series. A harmonic spectrum from the 18.6-year lunar nodal cycle in the Arctic time-series has been identified. The cycles in this harmonic spectrum have a stationary period, but not stationary amplitude and phase. A sub-harmonic cycle of about 74 years may introduce a phase reversal of the 18.6-year cycle. The signal-to-noise ratio between the lunar nodal spectrum and other sources changes from 1.6 to 3.2. A lunar nodal cycle in all time-series indicates that there is a forced Arctic oscillating system controlled by the pull of gravity from the moon, a system that influences long-term fluctuations in the extent of Arctic ice. The phase relation between the identified cycles indicates a possible chain of events from lunar nodal gravity cycles, to long-term tides, polar motions, Arctic ice extent, the NAO winter index, weather, and climate.

scholarly journals Predictors of invertebrate biomass and rate of advancement of invertebrate phenology across eight sites in the North American Arctic

Polar Biology ◽  
2021 ◽  
Vol 44 (2) ◽  
pp. 237-257
Author(s):  
Rebecca Shaftel ◽  
Daniel J. Rinella ◽  
Eunbi Kwon ◽  
Stephen C. Brown ◽  
H. River Gates ◽  
...  
Keyword(s):  
Prey Availability ◽  
Population Level ◽  
The Arctic ◽  
Environmental Drivers ◽  
Chick Survival ◽  
The North ◽  
Phenological Mismatch ◽  
Nesting Sites ◽  
North American Arctic

AbstractAverage annual temperatures in the Arctic increased by 2–3 °C during the second half of the twentieth century. Because shorebirds initiate northward migration to Arctic nesting sites based on cues at distant wintering grounds, climate-driven changes in the phenology of Arctic invertebrates may lead to a mismatch between the nutritional demands of shorebirds and the invertebrate prey essential for egg formation and subsequent chick survival. To explore the environmental drivers affecting invertebrate availability, we modeled the biomass of invertebrates captured in modified Malaise-pitfall traps over three summers at eight Arctic Shorebird Demographics Network sites as a function of accumulated degree-days and other weather variables. To assess climate-driven changes in invertebrate phenology, we used data from the nearest long-term weather stations to hindcast invertebrate availability over 63 summers, 1950–2012. Our results confirmed the importance of both accumulated and daily temperatures as predictors of invertebrate availability while also showing that wind speed negatively affected invertebrate availability at the majority of sites. Additionally, our results suggest that seasonal prey availability for Arctic shorebirds is occurring earlier and that the potential for trophic mismatch is greatest at the northernmost sites, where hindcast invertebrate phenology advanced by approximately 1–2.5 days per decade. Phenological mismatch could have long-term population-level effects on shorebird species that are unable to adjust their breeding schedules to the increasingly earlier invertebrate phenologies.

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