Cracks In Ice Research Articles

The influence of environmental microseismicity on detection and interpretation of small-magnitude events in a polar glacier setting

AbstractGlacial environments exhibit temporally variable microseismicity. To investigate how microseismicity influences event detection, we implement two noise-adaptive digital power detectors to process seismic data from Taylor Glacier, Antarctica. We add scaled icequake waveforms to the original data stream, run detectors on the hybrid data stream to estimate reliable detection magnitudes and compare analytical magnitudes predicted from an ice crack source model. We find that detection capability is influenced by environmental microseismicity for seismic events with source size comparable to thermal penetration depths. When event counts and minimum detectable event sizes change in the same direction (i.e. increase in event counts and minimum detectable event size), we interpret measured seismicity changes as ‘true’ seismicity changes rather than as changes in detection. Generally, one detector (two degree of freedom (2dof)) outperforms the other: it identifies more events, a more prominent summertime diurnal signal and maintains a higher detection capability. We conclude that real physical processes are responsible for the summertime diurnal inter-detector difference. One detector (3dof) identifies this process as environmental microseismicity; the other detector (2dof) identifies it as elevated waveform activity. Our analysis provides an example for minimizing detection biases and estimating source sizes when interpreting temporal seismicity patterns to better infer glacial seismogenic processes.

Numerical investigation of ice breaking by a high-pressure bubble based on a coupled BEM-PD model

In this paper, by combining the boundary element method (BEM) and peridynamics (PD), a bubble-ice interaction model is established, which can investigate the dynamic interactions between a high-pressure bubble and an ice plate with particular focus on the mechanical behaviors of ice breaking. The bubble dynamics are solved by BEM based on the potential flow theory. Ice cracks initiation and propagation are simulated by the bond-based peridynamics which is validated by a three-point bending test. The fluid–structure interaction (FSI) is achieved by matching the normal velocity and hydrodynamic loads at the fluid–structure interface. To validate the proposed FSI model, an experiment is carried out in which an oscillating bubble is generated under an ice plate by underwater discharge system. The whole interaction process is captured by a Phantom V711 high-speed camera. Qualitative agreements are achieved between the numerical and experimental results. The underlying mechanism of cracks initiation, propagation, branching, and coalescence of the ice plate is found to highly depend on three parameters, i.e., bubble–ice distance, ice thickness and bubble size. The present study is expected to provide further assists in the understanding of ice breaking problems.

Formation of Ice Microparticles in the Ovarian Fluid and Homogenates of Unfertilized Russian Sturgeon Eggs during Cooling to –196°C

Cryopreservation of fish and amphibian eggs is still an unsolved problem. The formation of ice crystals inside and outside cells acts as a main detrimental factor during a deep freezing of fish eggs, as well as crystal growth (recrystallization and repeated crystallization). Designing efficient cryoprotective media is necessary in order to avoid egg injury from freezing. Additional components that are present in a cryoprotective medium and reduce the thermomechanical stress and cracks of frozen tissues might increase oocyte survival after freezing–thawing. Natural components of eggs and the ovarian fluid are promising as such additives. The formation of ice microparticles was studied in thin layers (0.2 mm) of the ovarian fluid and components of Russian sturgeon egg homogenates upon their cooling to a liquid nitrogen temperature (–196°C). The processes of freezing, ice cracking, and microparticle formation were observed as the temperature was decreased gradually. The shape and size of ice microparticles were found to depend on the composition of the freezing solution. Certain fractions of egg homogenate were assumed to be suitable as components of a cryoprotective medium.

Peridynamic modeling and simulation of thermo-mechanical de-icing process with modified ice failure criterion

De-icing technology has become an increasingly important subject in numerous applications in recent years. However, the direct numerical modeling and simulation the physical process of thermo-mechanical deicing is limited. This work is focusing on developing a numerical model and tool to direct simulate the de-icing process in the framework of the coupled thermo-mechanical peridynamics theory. Here, we adopted the fully coupled thermo-mechanical bond-based peridynamics (TM-BB-PD) method for modeling and simulation of de-icing. Within the framework of TM-BB-PD, the ice constitutive model is established by considering the influence of the temperature difference between two material points, and a modified failure criteria is proposed, which takes into account temperature effect to predict the damage of quasi-brittle ice material. Moreover, thermal boundary condition is used to simulate the thermal load in the de-icing process. By comparing with the experimental results and the previous reported finite element modeling, our numerical model shows good agreement with the previous predictions. Based on the numerical results, we find that the developed method can not only predict crack initiation and propagation in the ice, but also predict the temperature distribution and heat conduction during the de-icing process. Furthermore, the influence of the temperature for the ice crack growth pattern is discussed accordingly. In conclusion, the coupled thermal-mechanical peridynamics formulation with modified failure criterion is capable of providing a modeling tool for engineering applications of de-icing technology.

Numerical simulation of level ice impact on landing craft bow considering the transverse isotropy of Baltic Sea ice based on XFEM

Ice bending is a major failure mechanism of level ice when ships and marine structures interact with level ice. This paper aims to investigate the ice bending and ice load when level ice collides on ships and marine structures using numerical simulation method, and compare the numerical results with field test. The fracture of ice is simulated with extended finite element method (XFEM), and cohesive zone concept is used to describe the crack propagation. In order to consider the characteristics of S2 columnar ice, a transversely isotropic elastic material model is used for the ice bulk elements, and a transversely isotropic Tsai-Wu failure criterion is adopted to predict the initiation of cracks. A well-controlled field test of a landing craft bow colliding with level ice in Baltic Sea is simulated to verify the numerical scheme. The ice plate's continuous deformation, crack initiation and crack propagation at different impact velocities and angles are simulated and the results are discussed. In the simulation, the bending crack emerges at the midline of the top surface of ice plate, then propagates towards free boundary, and finally a circumferential crack forms. It is found that with the impact velocity increases, the bending load increases and the fracture size (perpendicular distance from the crack to the contact edge) decreases. And as the angle between the landing craft bow and vertical direction increases, the bending load and the fracture size decrease. The simulated results corresponds well with the field test. The competition between the circumferential crack and radial crack is also found in the simulation and will be discussed in this paper. The results show that this method well simulates the bending of level ice and predict the ice load, and provides a good approach for investigating the mechanism of different forms of level ice fracture.

Forensic medical assessment of injuries caused by ice cracking tools

The work purpose is to identify objective morphological traits of punctured and stab and slash wounds obtained as a result of using the ice cracking tools. An experimental injury to the skin was carried out, followed by the study and analysis of morphological signs of wounds. It was established that, depending on the design features of the ice-cracking tools and the conditions of injury, the injuries have a number of similar characteristics with wounds from the other puncturing and stab and slash articles, as well as they have certain morphological features.

Acoustic emissions from in situ compression and indentation experiments on sea ice

We present results from measurement of acoustic emissions (AE) during compression and indentation of natural sea ice in situ. We show that AE amplitudes are associated with load, so that periods of loading and unloading, and cyclic oscillations in loading during indentation, can be determined from AE records as well as from load measurements. We show that AE measured during these experiments obeys Gutenberg-Richter-type scaling laws, implying that the crack distribution within the sea ice is self-similar. We show that b-values, which indicate the ratio of small cracks to large cracks, decrease during loading, tending towards a value around 1 at failure, and increase again when loading is removed. This suggests that AE can be used to measure, non-invasively, damage and healing of natural sea ice. We conclude by discussion practical applications of these results, and opportunities for further development of AE measurement as a tool for understanding cracking in ice.

Peridynamic modeling and simulation of coupled thermomechanical removal of ice from frozen structures

In this work, a bond-based peridynamic de-icing model has been developed to simulate the thermo-mechanical ice removal process of frozen structures. In the proposed numerical method, the influence of the deformation on the thermal states is considered. In this work, the ice is treated as an elastic brittle material in the framework of bond-based peridynamics, which can capture ice cracking during temperature increase and other temperature-dependent features of ice. Moreover, the characteristics of thermal load induced crack patterns in an ice sheet are discussed. The developed simulation method is verified and validated in a de-icing system of an aluminum sheet covered with ice, which is done by comparing the results obtained from peridynamic simulation with that obtained from finite element method (FEM) simulation. The results show good consistency between the peridynamic simulation and the FEM simulation. On the other hand, we find that the peridynamic simulations can directly capture the ice crack initiation and the crack propagation during the entire ice removal process, which is difficult to obtain from the FEM simulations.

Group sparse underwater acoustic channel estimation with impulsive noise: Simulation results based on Arctic ice cracking noise.

Many underwater acoustic (UWA) channels exhibit impulsive noise, thereby severely degrading the performance of traditional channel estimation algorithms. This paper presents two channel estimation algorithms for impulsive noise, namely (i) the variable forgetting factor l1,0 recursive least sign algorithm (VFF-l1,0-RLSA) and (ii) the variable forgetting factor l2,0 recursive least sign algorithm (VFF-l2,0-RLSA), both of which exploit the group sparse multipath structure and maintain robustness under impulsive noise. By using the l1 norm of the estimation error as part of the cost function, RLSAs are better at detecting and rejecting impulsive noise than the recursive least squares algorithms. A mixed l1,0 or l2,0 norm is incorporated with a RLSA to achieve better performance in group sparse UWA channel estimation. The time-varying forgetting factor and regularization parameter in the two proposed algorithms help to improve their performance. Simulation results based on Arctic ice cracking noise demonstrate the robustness and superiority of the two proposed algorithms.

FREEZE-THAW BEHAVIOR OF GYPSEOUS SOIL

This research work studied the influence of freeze-thaw (F-T) cycles and gypsum percent on the mechanical properties and durability of clayey soil. Different amount of gypsum percent (varied between 0-25%) was added to the clayey soil and subjected to 12 F-T cycles. The unconfined compressive strength UCS, P-wave velocity, gas permeability, pore size distribution and volume changes properties were measured for both un-cycled and F-T cycled samples. The tests results presented that the UCS, gas permeability and porosity values of samples influenced by F-T cycles. These values depend considerably on the amounts of gypsum percent and F-T cycles. Further, changes in soil porosity were observed during F-T cycles due to ice lenses formation and cracks propagation. Finally, the UCS, gas permeability and volume change values have been proposed to be used to evaluate extent of durability of soil samples.

Computer Model Calibration Based on Image Warping Metrics: An Application for Sea Ice Deformation

Arctic sea ice plays an important role in the global climate. Sea ice models governed by physical equations have been used to simulate the state of the ice including characteristics such as ice thickness, concentration, and motion. More recent models also attempt to capture features such as fractures or leads in the ice. These simulated features can be partially misaligned or misshapen when compared to observational data, whether due to numerical approximation or incomplete physics. In order to make realistic forecasts and improve understanding of the underlying processes, it is necessary to calibrate the numerical model to field data. Traditional calibration methods based on generalized least-square metrics are flawed for linear features such as sea ice cracks. We develop a statistical emulation and calibration framework that accounts for feature misalignment and misshapenness, which involves optimally aligning model output with observed features using cutting-edge image registration techniques. This work can also have application to other physical models which produce coherent structures. Supplementary materials accompanying this paper appear online.

A New Year’s Day icebreaker: icequakes on lakes in Alberta, Canada

Any process that causes a sudden brittle failure of material has the potential to cause earthquake-like seismic events. Cryoseisms represent an underreported class of seismic event due to their (often) small magnitudes. In this paper, we document the phenomenon of some of the largest magnitude lake-associated icequakes (ML2.0) yet reported. These events occurred nearly simultaneously (within ∼2 h) on geographically separate lakes in Alberta, Canada, starting 1 January 2018. We conjecture that these events were caused by the sudden brittle failure of lake ice due to thermal expansion; the effects of the thermal expansion were compounded by the lack of insulating snow cover, high lake water levels, and a rapid onset of atmospheric warming. These factors also contributed to ice-jacking — a repeating process in which thermal contraction produces tensile cracks (leads) in lake ice that are then filled with water that is frozen during the cooling cycle. Thus, any subsequent thermal expansion must be accommodated by new deformation or brittle failure. This ice-jacking process caused creeping ground deformation after the initial brittle failure and again two weeks later following a second warming period. In many cases, the resulting ground deformation was significant enough to cause property damage.

Roly Poly by Mem Fox

Reviewed by: Roly Poly by Mem Fox Kate Quealy-Gainer, Assistant Editor Fox, Mem Roly Poly; illus. by Jane Dyer; photographs by Jeanne Birdsall. Beach Lane/Simon, 2019 40p Trade ed. ISBN 978-1-4814-4556-6 $17.99 E-book ed. ISBN 978-1-4814-4557-3 $10.99 R 4-7 yrs Roly Poly the polar bear is none too pleased when a baby brother shows up unannounced: "I never asked for a little brother and I don't want one now." Of course, little brother Monty toddles around after Roly Poly everywhere, stealing Roly Poly's hard-won fish, grabbing Roly Poly's precious walrus tooth, and just generally being a nuisance. He's such a nuisance, in fact, that when the ice cracks and Monty is stranded on a drifting iceberg, Roly Poly hesitates, but he does finally jump into the icy seas to save him. While baby bro's transition into toddlerhood feels a little rushed, this is a genuinely funny and compassionate affirmation to big brothers and sisters that yes, sometimes a baby sib is an undeniable pain in the rear. Mom's reaction to Roly Poly's insistence that he really has no desire for Monty's presence ("I know. … But we think you will adore him") is the height of adult obliviousness, and it will likely feel familiar to any kid who's only grudgingly welcomed a new addition to the family. Photographs of the posed three-dimensional polar bear figurines, handmade by needle felting, are surprisingly emotive, both in Roly Poly's disdain and his folks' excitement, and the miniature scenes are sure to delight fans of dollhouses and their ilk with their teeny tiny versions of ice skates, a telescope, fishing poles, and even a family "portrait." With a bit of sass and a whole lot of warmth, this will make even the most reluctant older child chuckle. Copyright © 2019 The Board of Trustees of the University of Illinois

Modelling of sea-ice phenomena.

The focus of the present theme issue is on significant recent advances in the understanding and modelling of floating sea ice. This also follows an extended and concerted research programme held in late 2017 at the Isaac Newton Institute in which the mathematics of sea-ice phenomena was addressed. Other forms of ice are included where they help with the phenomenological and/or methodological understanding of sea-ice behaviour. The heart of the theme here is associated with consistent modelling of facets of sea-ice mechanics and thermodynamics, as well as sea-ice interactions with fluids and solids. Particular studies are on multi-scale modelling of ice characteristics and behaviour, ice–fluid interaction, coupled problems of ice-structure interaction, and ice fracture and cracks. Environmental aspects of ice-related problems are included when they relate to sea-ice mechanics, and congruent industrial icing problems are also discussed. The topic is appropriate for a theme issue because of its depth, breadth and timeliness. The content is of a fully inter-disciplinary nature throughout. The new developments presented and discussed hinge on the advances of modelling of ice-related problems giving an appropriate level of both physical and mathematical rigour to such problems. The theme aims to help towards defining a state of the art in floating ice research, but especially …

Behavior of innovative circular ice filled steel tubular stub columns under axial compression

The use of conventional building materials has many limitations in cold regions. Inspired by the idea of concrete filled steel tube (CFT), a new form of construction component named ice filled steel tube (IFT), which effectively combines the advantages of both ice and steel tube, was innovatively proposed in this study. This paper presents an experimental study on circular IFT stub columns under axial compression. The main parameter of the test specimens is the diameter-to-thickness (D/t) ratio of the steel tube. A total of 12 specimens including 3 plain ice columns and 9 circular IFT columns were divided into four series and tested under axial compression. The test results showed that the development of cracks in ice was delayed by the steel tube. As a result, both the ultimate bearing capacity and the ductility of the ice column were improved due to the confinement from the steel tube. The local bucking at the bottom of the steel tube was also delayed by the ice core. Therefore, the circular IFT column has good potential to serve as a structural component in cold regions.

Characteristics of the under-ice soundscape in the southern Beaufort Sea during Ice Exercise 2016

Ice Camp SARGO was the remote hub of operations for the multi-national naval operation Ice Exercise 2016 (ICEX-16), held in March of that year. Over a three-day period in early March, continuous recordings of the under-ice soundscape were collected with receivers deployed at various depths through first-year ice in the vicinity of the ice camp as it drifted westward across the Beaufort Sea approximately 175 nm north of Prudhoe Bay, Alaska. A significant reduction in the strength of easterly winds resulted in deceleration of the ice sheet during the period of observation, inducing notable ice cracking and ridging events near the camp. Ice sheet movement slowed from about 0.5 knots early in the test to virtually coming to a halt near the end of the recording period. Sounds from naturally occurring and anthropogenic sources in the 10-Hz to 10-kHz band detected in the recordings were analyzed in connection to the origins of the sound and correlated to varying environment conditions including wind speed and ice motion. Results show a wide variety of persistent and transient sound sources contribute to the total soundscape at this remote location. Comparisons to other soundscape observations in the region are discussed.

Influence of Sea Ice Crack Formation on the Spatial Distribution of Nutrients and Microalgae in Flooded Antarctic Multiyear Ice

AbstractCracks are common and natural features of sea ice formed in the polar oceans. In this study, a sea ice crack in flooded, multiyear, land‐fast Antarctic sea ice was examined to assess its influence on biological productivity and the transport of nutrients and microalgae into the upper layers of neighboring sea ice. The water inside the crack and the surrounding host ice were characterized by a strong discoloration (brown color), an indicator of a massive algal bloom. Salinity and oxygen isotopic ratio measurements indicated that 64–84% of the crack water consisted of snow meltwater supplied during the melt season. Measurements of nutrient and chlorophyll a concentrations within the slush layer pool (the flooded layer at the snow‐ice interface) revealed the intrusion of water from the crack, likely forced by mixing with underlying seawater during the tidal cycle. Our results suggest that sea ice crack formation provides conditions favorable for algal blooms by directly exposing the crack water to sunlight and supplying nutrients from the under‐ice water. Subsequently, constituents of the crack water modified by biological activity were transported into the upper layer of the flooded sea ice. They were then preserved in the multiyear ice column formed by upward growth of sea ice caused by snow ice formation in areas of significant snow accumulation.

Laser-induced cracks in ice due to temperature gradient and thermal stress

This work presents the experimental and theoretical investigations on the mechanism of laser-induce cracks in ice. The laser-induced thermal gradient would generate significant thermal stress and lead to the cracking without thermal melting in the ice. The crack density induced by a pulsed laser in the ice critically depends on the laser scanning speed and the size of the laser spot on the surface, which determines the laser power density on the surface. A maximum of 16 cracks within an area of 17 cm × 10 cm can be generated when the laser scanning speed is at 10 mm/s and the focal point of the laser is right on the surface of the ice with a laser intensity of ∼4.6 × 107 W/cm2. By comparing the infrared images of the ice generated at various experimental conditions, it was found that a larger temperature gradient would result in more laser-induced cracks, while there is no visible melting of the ice by the laser beam. The data confirm that the laser-induced thermal stress is the main cause of the cracks created in the ice.

Experimental studies of ice cracking tests in an anechoic chamber

As the Northwest passage becomes more frequently traveled by commercial and business interests, it is becoming important to increase existing methods for safety at sea in harsh Arctic conditions. In order to identify ice-floe movements in the Arctic, acoustical signatures for ice behaviors need to be identified and analyzed. Being able to identify the acoustic signature of ice cracking in real-time will help vessels navigate the arctic by identifying moving ice-floes and monitoring present ice conditions. This study identifies a novel method for detecting thermal cracking in ice, ice fracturing, and ice shearing events in an anechoic chamber. Comparing the power spectra and identified peak frequencies against empirically collected data from previous studies, this methodology aims to recreate the arctic environment in a lab without travel to the region for baseline data collection. Furthermore, based on a literature review, little power spectra data exist. The data collected from this study will add to the creation of a baseline identification for future ice fracture studies. Observations are made on the collected data which can be used to improve navigational methods for safety at sea.

Strain field evolution at the ductile-to-brittle transition: a case study on ice

Abstract. This paper presents, for the first time, the evolution of the local heterogeneous strain field around intra-granular cracking in polycrystalline ice, at the onset of tertiary creep. Owing to the high homologous temperature conditions and relatively low compressive stress applied, stress concentration at the crack tips is relaxed by plastic mechanisms associated with dynamic recrystallization. Strain field evolution followed by digital image correlation (DIC) directly shows the redistribution of strain during crack opening, but also the redistribution driven by crack tip plasticity mechanisms and recrystallization. Associated local changes in microstructure induce modifications of the local stress field evidenced by crack closure during deformation. At the ductile-to-brittle transition in ice, micro-cracking and dynamic recrystallization mechanisms can co-exist and interact, the later being efficient to relax stress concentration at the crack tips.