The effect of the blocking of impact ocean waves by the crevasse-ridden ice shelf

2020 ◽  
Author(s):  
Yuri Konovalov
Keyword(s):  
Band Gap ◽  
Numerical Experiments ◽  
Amplitude Spectrum ◽  
Ocean Waves ◽  
Band Gaps ◽  
Elastic Model ◽  
Ice Shelf ◽  
Impact Wave ◽  
Wide Range ◽  
The Impact

<p>The propagation of high-frequency elastic-flexural waves through an ice shelf was modeled by a full 3-D elastic model, which also takes into account sub-ice seawater flow. The sea water flow is described by the wave equation. Numerical experiments were undertaken both for an intact ice shelf free of crevasses, which has idealized rectangular geometry, and for a crevasse-ridden ice shelf. The crevasses were modeled as triangle/rectangular notches into the ice shelf. The obtained dispersion spectra (the dispersion curves describing the wavenumber/periodicity relation) are not continuous. The spectra reveal gaps that provide the transition from n-th mode to (n+1)-th mode. These gaps are observed both for an intact ice shelf free of crevasses and for a crevasse-ridden ice shelf. They are aligned with the minimums in the amplitude spectrum. That is the ice shelf essentially blocks the impact wave at this transition. However, the dispersion spectrum obtained for a crevasse-ridden ice shelf, has a qualitatively difference from that obtained for an intact ice shelf free of crevasses. Moreover, the dispersion spectrum obtained for a crevasse-ridden ice shelf reveals the band gap – the zone there no eigenmodes exist (Freed-Brown and others, 2012). The numerical experiments with the crevasse-ridden ice tongue that is 16 km in longitudinal extent, 0.8km width and 100m thick, were undertaken for a wide range of the periodicities of the incident wave: from 5 s to 250 s. The obtained dispersion spectra reveal two band gaps in this range: the first band gap at about 20 s and the second band gap at about 7 s for 1km spatial periodicity of the crevasses. The width of the band gap significantly increases when the crevasses depth increases too. Respectively, the amplitude spectra reveal significantly increasing area of periodicities/frequencies where the ice shelf blocks the impact wave.</p><p><strong>References</strong></p><p>Freed-Brown, J., Amundson, J., MacAyeal, D., & Zhang, W. (2012). Blocking a wave: Frequency band gaps in ice shelves with periodic crevasses. Annals of Glaciology, 53(60), 85-89. doi:10.3189/2012AoG60A120</p><p>Konovalov, Y.V. (2019). Ice-shelf vibrations modeled by a full 3-D elastic model. Annals of Glaciology, 1-7. doi:10.1017/aog.2019.9</p>

scholarly journals Ice shelf flexures modeled with a 2-D elastic flow line model

2011 ◽  
Vol 5 (5) ◽  
pp. 2841-2863 ◽  
Author(s):  
Y. V. Konovalov
Keyword(s):  
Water Flow ◽  
Numerical Experiments ◽  
Sea Water ◽  
Flow Line ◽  
Wide Spectrum ◽  
Elastic Model ◽  
Ice Shelf ◽  
Sea Levels ◽  
The Impact ◽  
Pressure Perturbations

Abstract. Ice shelf flexures modeling was performed using a 2-D finite-difference elastic model, which takes into account sub-ice-shelf sea water flow. The sub-ice water flow was described by the wave equation for the sub-ice-shelf pressure perturbations (Holdsworth and Glynn, 1978). In the model ice shelf flexures result from variations in ocean pressure due to changes in prescribed sea levels. The numerical experiments were performed for a flow line down one of the fast flowing ice streams of the Academy of Sciences Ice Cap. The profile includes a part of the adjacent ice shelf. The numerical experiments were carried out for harmonic incoming pressure perturbations P' and the ice shelf flexures were obtained for a wide spectrum of the pressure perturbations frequencies, ranging from tidal periods down to periods of a few seconds (0.004..0.02 Hz). The amplitudes of the ice shelf deflections obtained by the model achieve a maxima at about T ≈ 165 s in concordance with previous investigations of the impact of waves on Antarctic ice shelves (Bromirski et al., 2010). The explanation of the effect is found in the solution of the corresponding eigenvalue problem revealing the existence of a resonance at these high frequencies.

scholarly journals Abatement of Ocean-Wave Impact by Crevasses in an Ice Shelf

2021 ◽  
Vol 9 (1) ◽  
pp. 46
Author(s):  
Yuri V. Konovalov
Keyword(s):  
Water Layer ◽  
Ocean Waves ◽  
Point Of View ◽  
Band Gaps ◽  
Ice Shelf ◽  
Average Amplitude ◽  
Difference Model ◽  
Wave Impact ◽  
Pressure Oscillations ◽  
The Impact

Forced ice-shelf oscillations modeling was undertaken employing a full 3D finite-difference model of an elastic ice shelf that was coupled to a treatment of under-shelf seawater flux. The seawater flux was described by the wave equation, which includes the pressure excitements in the shallow water layer under the ice shelf. Thus, ice-shelf flexure was produced by hydrostatic pressure oscillations in the below-shelf seawater. Numerical calculations were performed for an idealized rectangular crevasse-ridden ice-shelf geometry. The crevasses were modeled as rectangular notches into the ice shelf. In the numerical experiments, the ice-plate flexures were forced by harmonic-entering pressure oscillations having a range of periodicities 5–250 s. The dispersion spectra derived for a crevasse-ridden ice shelf revealed “band gaps”—frequency ranges where no eigenmodes exist. The results further showed that the impact of ocean waves on the ice plate is abated from the point of view of a decrease in the spectral average amplitude in the vicinity of the spectrum where the “band gaps” are observed. This impact depends on the depth of crevasse penetration to the ice.

scholarly journals Ice-shelf forced vibrations modelled with a full 3-D elastic model

2014 ◽  
Vol 8 (6) ◽  
pp. 6059-6078
Author(s):  
Y. V. Konovalov
Keyword(s):  
Thin Plate ◽  
High Frequency ◽  
Numerical Experiments ◽  
Wide Spectrum ◽  
Forced Vibrations ◽  
Elastic Model ◽  
Ice Shelf ◽  
Plate Vibrations ◽  
The Impact ◽  
Pressure Perturbations

Abstract. Ice-shelf forced vibrations modelling was performed using a full 3-D finite-difference elastic model, which takes into account sub-ice seawater flow. The sub-ice seawater flow was described by the wave equation, so the ice-shelf flexures result from the hydrostatic pressure perturbations in sub-ice seawater layer. The numerical experiments were performed for idealized ice-shelf geometry, which was considered in the numerical experiments in Holdsworth and Glynn (1978). The ice-plate vibrations were modelled for harmonic ingoing pressure perturbations and for a wide spectrum of the ocean swell periodicities, ranging from infragravity wave periods down to periods of a few seconds (0.004–0.2 Hz). The spectrums for the vibration amplitudes were obtained in this range and are published in this manuscript. The spectrums contain distinct resonant peaks, which corroborate the ability of resonant-like motion in suitable conditions of the forcing. The impact of local irregularities in the ice-shelf geometry to the amplitude spectrums was investigated for idealized sinusoidal perturbations of the ice surface and the sea bottom. The results of the numerical experiments presented in this manuscript, are approximately in agreement with the results obtained by the thin-plate model in the research carried out by Holdsworth and Glynn (1978). In addition, the full model allows to observe 3-D effects, for instance, vertical distribution of the stress components in the plate. In particular, the model reveals the increasing in shear stress, which is neglected in the thin-plate approximation, from the terminus towards the grounding zone with the maximum at the grounding line in the case of considered high-frequency forcing. Thus, the high-frequency forcing can reinforce the tidal impact to the ice-shelf grounding zone additionally exciting the ice fracture there.

scholarly journals The Band-Gap Studies of Short-Period CdO/MgO Superlattices

2021 ◽  
Vol 16 (1) ◽  
Author(s):  
Ewa Przeździecka ◽  
P. Strąk ◽  
A. Wierzbicka ◽  
A. Adhikari ◽  
A. Lysak ◽  
...  
Keyword(s):  
Band Gap ◽  
Layer Thickness ◽  
Energy Gap ◽  
Band Gaps ◽  
Short Period ◽  
Wide Range ◽  
Salt Structure ◽  
Short Period Superlattices ◽  
Direct Band ◽  
Sublayer Thickness

AbstractTrends in the behavior of band gaps in short-period superlattices (SLs) composed of CdO and MgO layers were analyzed experimentally and theoretically for several thicknesses of CdO sublayers. The optical properties of the SLs were investigated by means of transmittance measurements at room temperature in the wavelength range 200–700 nm. The direct band gap of {CdO/MgO} SLs were tuned from 2.6 to 6 eV by varying the thickness of CdO from 1 to 12 monolayers while maintaining the same MgO layer thickness of 4 monolayers. Obtained values of direct and indirect band gaps are higher than those theoretically calculated by an ab initio method, but follow the same trend. X-ray measurements confirmed the presence of a rock salt structure in the SLs. Two oriented structures (111 and 100) grown on c- and r-oriented sapphire substrates were obtained. The measured lattice parameters increase with CdO layer thickness, and the experimental data are in agreement with the calculated results. This new kind of SL structure may be suitable for use in visible, UV and deep UV optoelectronics, especially because the energy gap can be precisely controlled over a wide range by modulating the sublayer thickness in the superlattices.

scholarly journals Viscous and elastic buoyancy stresses as drivers of ice-shelf calving

2020 ◽  
Vol 66 (258) ◽  
pp. 643-657 ◽  
Author(s):  
Cyrille Mosbeux ◽  
Till J. W. Wagner ◽  
Maya K. Becker ◽  
Helen A. Fricker
Keyword(s):  
Ice Sheet ◽  
Elastic Model ◽  
Ice Shelf ◽  
Ice Shelves ◽  
Bending Stresses ◽  
Iceberg Calving ◽  
Basal Melting ◽  
The Antarctic ◽  
The Impact ◽  
Maximum Stresses

AbstractThe Antarctic Ice Sheet loses mass via its ice shelves predominantly through two processes: basal melting and iceberg calving. Iceberg calving is episodic and infrequent, and not well parameterized in ice-sheet models. Here, we investigate the impact of hydrostatic forces on calving. We develop two-dimensional elastic and viscous numerical frameworks to model the ‘footloose’ calving mechanism. This mechanism is triggered by submerged ice protrusions at the ice front, which induce unbalanced buoyancy forces that can lead to fracturing. We compare the results to identify the different roles that viscous and elastic deformations play in setting the rate and magnitude of calving events. Our results show that, although the bending stresses in both frameworks share some characteristics, their differences have important implications for modeling the calving process. In particular, the elastic model predicts that maximum stresses arise farther from the ice front than in the viscous model, leading to larger calving events. We also find that the elastic model would likely lead to more frequent events than the viscous one. Our work provides a theoretical framework for the development of a better understanding of the physical processes that govern glacier and ice-shelf calving cycles.

scholarly journals Ice-shelf vibrations modeled by a full 3-D elastic model

2019 ◽  
Vol 60 (79) ◽  
pp. 68-74 ◽  
Author(s):  
Yuri V. Konovalov
Keyword(s):  
Thin Plate ◽  
Sea Water ◽  
Elastic Model ◽  
Ice Shelf ◽  
Incoming Wave ◽  
Plate Vibrations ◽  
Wide Range ◽  
Pressure Perturbations ◽  
D Model ◽  
Vibration Modeling

ABSTRACTForced ice-shelf vibration modeling is performed using a full 3-D finite-difference elastic model, which also takes into account sub-ice seawater flow. The sea water flow is described by the wave equation. Ice-shelf flexure therefore results from hydrostatic pressure perturbations in the sub-ice seawater layer. Numerical experiments were undertaken for idealized rectangular ice-shelf geometry. The ice-plate vibrations were modeled for harmonic incoming pressure perturbations and for a wide range of incoming wave frequencies. The spectra showed distinct resonant peaks, which demonstrate the ability of the model to simulate a resonant-like motion. The spectra obtained by the full 3-D model are compared with exact solutions for the elastic thin plate with two fixed edges and two free edges. The spectra are also compared with the spectra modeled by the thin-plate Holdsworth and Glynn model (1978).

Critical trigger condition of seabed liquefaction under ocean waves

2021 ◽  
Author(s):  
Cheng-Jung Hsu ◽  
Ching Hung
Keyword(s):  
Shallow Water ◽  
Deep Water ◽  
Water Wave ◽  
Ocean Waves ◽  
Theoretical Modelling ◽  
Stokes Wave ◽  
Wave Condition ◽  
Soil Response ◽  
Wide Range ◽  
The Impact

<p>Soil liquefaction in seabed not only drives vertical sediment transportation but also weakens coastal infrastructures such as pipeline or underwater foundation. The damage of seabed liquefaction events had been documented in literature. Due to the threat to lives and environment, it is important to have an exhaustive analysis on the risk assessment of seabed liquefaction subjected to ocean waves. The objective of this study is to assess the critical wave condition triggering seabed liquefaction in oceanic environment through theoretical modelling. Our investigation focused on the wave condition of momentary liquefaction induced by periodic wave loading. The scenario considers a permeable seabed on which a wide range of ocean waves propagates, and the critical wave parameters of wave height and wavelength causing liquefaction are examined. A two-dimensional analytical solution of seabed response based on Biot’s consolidation theory is applied with nonlinear water wave theory to predict the soil response and the consequence of liquefaction.  In contrast to the previous studies of seabed response applying the analytical solutions which only valid for a restricted wave range, we use a numerical approach of finite-amplitude wave to reflect the nonlinearity effect in a wide range of water wave from deep water to shallow water.  The present assessment of liquefaction is compared with the extant solution of seabed response under Stokes wave and cnoidal wave for validation. In additional, the potential of liquefaction instability is performed by a critical curve of wave condition covering the range of ocean waves from deep water to shallow water. Our study provides advanced theoretical framework and robust mathematical model for the assessment of wave-induced seabed instability under water waves, and the detailed analysis sheds insight into the impact of ocean waves on the seabed liquefaction.</p>

scholarly journals Blocking a wave: frequency band gaps in ice shelves with periodic crevasses

2012 ◽  
Vol 53 (60) ◽  
pp. 85-89 ◽  
Author(s):  
Julian Freed-Brown ◽  
Jason M. Amundson ◽  
Douglas R. MacAyeal ◽  
Wendy W. Zhang
Keyword(s):  
Band Gap ◽  
Mechanical Response ◽  
Normal Modes ◽  
Small Region ◽  
Band Gaps ◽  
Flexural Waves ◽  
Ice Shelf ◽  
Ice Shelves ◽  
Spatially Periodic ◽  
Lateral Extent

AbstractWe assess how the propagation of high-frequency elastic-flexural waves through an ice shelf is modified by the presence of spatially periodic crevasses. Analysis of the normal modes supported by the ice shelf with and without crevasses reveals that a periodic crevasse distribution qualitatively changes the mechanical response. The normal modes of an ice shelf free of crevasses are evenly distributed as a function of frequency. In contrast, the normal modes of a crevasse-ridden ice shelf are distributed unevenly. There are ‘band gaps’, frequency ranges over which no eigenmodes exist. A model ice shelf that is 50 km in lateral extent and 300 m thick with crevasses spaced 500 m apart has a band gap from 0.2 to 0.38 Hz. This is a frequency range relevant for ocean-wave/ice-shelf interactions. When the outermost edge of the crevassed ice shelf is oscillated at a frequency within the band gap, the ice shelf responds very differently from a crevasse-free ice shelf. The flexural motion of the crevassed ice shelf is confined to a small region near the outermost edge of the ice shelf and effectively ‘blocked’ from reaching the interior.

THE IMPACT OF LEADERSHIP PRACTICES TO TEAM MEMBERS’ SATISFACTION

2009 ◽  
Vol 8 (1) ◽  
Author(s):  
Chalimah .
Keyword(s):  
Conflict Resolution ◽  
Leadership Practices ◽  
Hotel Industry ◽  
Leader Behavior ◽  
Team Leader ◽  
Shop Floor ◽  
Team Members ◽  
Top Executives ◽  
Wide Range ◽  
The Impact

eamwork is becoming increasingly important to wide range of operations. It applies to all levels of the company. It is just as important for top executives as it is to middle management, supervisors and shop floor workers. Poor teamwork at any level or between levels can seriously damage organizational effectiveness. The focus of this paper was therefore to examine whether leadership practices consist of team leader behavior, conflict resolution style and openness in communication significantly influenced the team member’s satisfaction in hotel industry. Result indicates that team leader behavior and the conflict resolution style significantly influenced team member satisfaction. It was surprising that openness in communication did not affect significantly to the team members’ satisfaction.

Efficient Prediction of Structural and Electronic Properties of Hybrid 2D Materials Using DFT and Machine Learning

2018 ◽  
Author(s):  
Sherif Tawfik ◽  
Olexandr Isayev ◽  
Catherine Stampfl ◽  
Joseph Shapter ◽  
David Winkler ◽  
...  
Keyword(s):  
Machine Learning ◽  
Band Gap ◽  
Density Functional ◽  
2D Materials ◽  
Van Der Waals ◽  
Building Blocks ◽  
Machine Learning Techniques ◽  
Interlayer Distance ◽  
Computational Screening ◽  
Wide Range

Materials constructed from different van der Waals two-dimensional (2D) heterostructures offer a wide range of benefits, but these systems have been little studied because of their experimental and computational complextiy, and because of the very large number of possible combinations of 2D building blocks. The simulation of the interface between two different 2D materials is computationally challenging due to the lattice mismatch problem, which sometimes necessitates the creation of very large simulation cells for performing density-functional theory (DFT) calculations. Here we use a combination of DFT, linear regression and machine learning techniques in order to rapidly determine the interlayer distance between two different 2D heterostructures that are stacked in a bilayer heterostructure, as well as the band gap of the bilayer. Our work provides an excellent proof of concept by quickly and accurately predicting a structural property (the interlayer distance) and an electronic property (the band gap) for a large number of hybrid 2D materials. This work paves the way for rapid computational screening of the vast parameter space of van der Waals heterostructures to identify new hybrid materials with useful and interesting properties.

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