Ice Pieces Research Articles

Watergel in liquid helium

Semitransparent soft water clouds forming in superfluid He-II by condensation of a gaseous mixture of 4He with water impurities transform with time to more rigid, highly porous ‘icebergs’. The icebergs suspended in the bulk of He-II are stable at a constant temperature T≤1.6 K, and they can beak down to small ice pieces on heating the liquid above Tλ. The temperature of decomposition of the icebergs in He-I depends strongly on the vapor pressure above the surface of the liquid: at P∼0.2 atm they start to decompose at Td∼2.5 K, but increasing the pressure to 1 atm causes Td to rise to ∼4 K. When withdrawn from He-II the “dry” icebergs segregate to an ice powder and He on heating them above 1.8 K in He gas atmosphere. The total content of the water in the bulk of the icebergs, estimated from the ratio by volume of icebergs and powder, is ≤1020 molecules/cm3. From observations of acoustic oscillations in the cell filled with He-1 (the ratio of amplitudes of vibrations of the iceberg and He-I level is about 0.2–0.3) it can be estimated that the density of the iceberg is only a few percent higher than the density of the surrounding liquid. We suggest that the highly porous water condensate (watergel) is composed of water nanoclusters, coated with 1-2 layers of solidified helium, which form a dispersed system of gel, and of liquid Helium, filling the pores between these van-der-Waals complexes, which serves as the dispersion medium of the gel.

Some clinical factors related to rate of resorption of residual ridges

Resorption of residual ridges is a complex biophysical process. Sometimes a simile is made between bone and ice. If a measured weight is placed on a measured piece of ice for a given length of time at a given temperature and atmospheric pressure, a predictable degree of melting of the ice occurs. This is a physical process subject to certain physical laws. However, if a measured force is applied on alveolar bone, either through natural teeth or through a denture, different effects are observed in different patients. The force in this second situation is subject to the same physical laws, but in addition, the response of the bone is governed by certain physiologic laws.

Preparation method of porous polymer materials by radiation technique and its application

AbstractThe radiation polymerization of hydrophilic hydroxyethyl methacrylate monomer solution at temperatures below 0 °C leads to the formation of a porous structure in the polymers. The melting peak of the eutectic water–monomer composition at the eutectic point (above −24 °C) could be distingushed and a glass transition temperature was observed at −96 °C.The porous structure was developed after melting small ice pieces in the polymers after polymerization. The porous structure formed above 0 °C contained discontinuous pores and that formed below 0 °C had continuous pores leading to reticular structure. In a mixture of water –dioxane –monomer, the pore diameter decreased with increasing monomer concentration. Replacing dioxane with decane led to a maximum pore diameter at 70% monomer concentration. The pore diameter in 70% monomer concentration using water and dioxane was 1∼4 µm, maximum activity in immobilized enzyme tablets was observed at this diameter. The porous structure was also varied by controlling the polymerization temperature. The durability of the immobilized enzyme tablets was demonstrated by the retention of high enzyme activities after repeated batch enzyme reactions. Copyright © 2001 John Wiley & Sons, Ltd.

Bergy bit and growler melt deterioration

The Canadian Ice Service, Environment Canada, is currently developing an operational iceberg forecasting model; the present work forms part of that effort. While existing models predict iceberg drift and deterioration, the new model will account for calving that produces smaller ice pieces and subsequently track the drift and melt of the calved pieces. Bergy bits and growlers, which we consider here to be ice pieces in the size range from 3 to 20 m, can cause large forces upon impact with offshore structures. The probability of encountering these bergy bits and growlers is of significant interest to marine transportation and offshore resource development. Calving due to wave‐induced erosion at the waterline of a floating iceberg can produce many thousands of small ice pieces having a wide distribution of sizes. These small ice pieces then melt as individual entities and eventually disappear. Since the calving events occur periodically, there is a continual supply of small ice pieces in the neighborhood of the parent iceberg. The focus of the present paper is on the evolution of the size‐frequency distribution function for the calved ice pieces. It makes use of the initial distribution function following the calving event discussed by Savage et al. (2000). Dimensional analysis, laboratory tests, and field observations are applied to obtain simple correlations and devise a melt law for the smaller ice pieces. This melt law is then used to determine the temporal evolution of the small ice piece size‐frequency distribution function.

A modified extraction technique for liberating occluded gases from ice cores

We have developed a new dry extraction technique to extract air from large pieces of glacial ice. The primary reason for developing this technique was to be able to perform a single extraction and measure a single sample of air from an ice core sample for as many atmospheric constituents as possible. The procedure is modeled after the dry extraction ‐“cheese grater” design of Etheridge et al. [1988]. Extracted air samples are analyzed for the elemental and isotopic composition of O2 and N2 as well as the CH4 concentration. Extensive experimental work to determine the integrity of the extraction procedure yielded blank values and external precision which are comparable with exiting extraction procedures. Overall external precision for δO2/N2, δ18O of O2, and δ15of N2 analyses is ±2.1‰, ±0.074‰, and ±0.045‰, respectively. Variable δO2/N2 results from ice which is either completely bubbly or clathrated are in good agreement with previous measurements. Variable δO2/N2 results from Greenland Ice Sheet Project (GISP) II ice samples spanning the clathrate formation region (1000–1500 m) are markedly different from previous results obtained with a “wet” extraction procedure. We attribute the differences to variable δO2/N2 ratios in bubbles and clathrates in the clathrate formation region combined with a 21% difference in our extraction efficiency for bubbly versus clathrated ice. The overall uncertainty and blank value for CH4 measurements are ±19 ppb and 16 ppb, respectively. CH4 concentrations for ice between 115 and 140 meters below the surface (mbs) from the GISPII ice core appear to be 4.3% higher than the average value measured by five other laboratories. We attribute our elevated values to uncertainties in the actual concentration of our working standard and small differences in the CH4 concentration of the liberated air relative to the total air trapped in ice. Our corrected CH4 data spanning the last 25 kyr are indistinguishable from the Brook et al. (1996) CH4 record from the same period.

Size distributions of small ice pieces calved from icebergs

This study was part of a larger project currently underway to develop an operational iceberg drift and deterioration model for the Canadian Ice Service (CIS), Environment Canada. This new iceberg model, as distinct from previous drift computations, will include estimates of iceberg calving and production of smaller ice pieces in the bergy bit and growler size ranges. These smaller size pieces can cause large forces upon impact with offshore structures. It is important to have information about the probability of encountering these small ice pieces in the neighborhood of the parent iceberg. Calving can result from wave-induced erosion at the waterline of a floating iceberg. When the waterline notch caused by wave erosion reaches a critical size, the weight of the overhanging slab will be large enough to cause it to break off and fracture into many thousands of small ice pieces. The focus of the present paper is on the size-frequency distribution function for the ice pieces that are generated. The correlations presented are based primarily on the field observations of calving by Crocker [Crocker, G.B., 1993, Size distributions of bergy bits and growlers calved from deteriorating icebergs. Cold Reg. Sci. Technol., 22, 113–119.]. The initial size distribution of the calved pieces forms an essential starting point for the subsequent analyses of small ice piece deterioration and drift that are embodied in the operational model.

Formation of Cyclic Water Hexamer in Liquid Helium: The Smallest Piece of Ice

The cyclic water hexamer, a higher energy isomer than the cage structure previously characterized in the gas phase, was formed in liquid helium droplets and studied with infrared spectroscopy. This isomer is formed selectively as a result of unique cluster growth processes in liquid helium. The experimental results indicate that the cyclic hexamer is formed by insertion of water molecules into smaller preformed cyclic complexes and that the rapid quenching provided by the liquid helium inhibits its rearrangement to the more stable cage structure.

Tolerance for Freezing in Hatchling Turtles

Tolerance for Freezing in Hatchling Turtles

Information states in radar imagery of sea ice

It is shown empirically that information in an image of sea ice exists in two forms-textural and structural. It is shown that such information can be extracted from the conditional probability of intensity differences between neighboring pixels. There exists a relationship between the two forms of information, called the information curve, which has identifiable subsections, each related to an ice type. The overall state of the sea ice image, composed as it is of a mixture of ice types, can therefore be given by the location of phase transition points that mark the end points of the subsections on the information curve composed of the two types of information. This result leads to a segmentation of the image by ice type. The properties of the information within the image are examined. It is shown that the textural information associated with individual ice pieces is scale invariant, whereas the structural information associated with the size and shape of these pieces, which dominates the image, has a scaling or fractal property. These results led to the examination of similarity sets, describing scaled intensity differences and separation jointly. Significantly, a multifractal relationship for these sets holds at all intensities, at least for ice types associated with brittle fracture. Another result inspired by the need to identify paths of least resistance through an ice field is the existence of a distinct change in the connectivity of these similarity sets at a critical value of the index parameter of the set. Such a critical value is in turn related to that of the local textural information, which is related to the phase transitions associated with the relationship between textural and structural information.

An examination of the distribution of snow on sea‐ice

Snow on sea‐ice is an integral, yet poorly understood, component of the ocean‐sea‐ice‐atmosphere interface. Snow exerts a significant control on both shortwave and conductive fluxes due to its high albedo and low thermal conductivity. Parameters pertaining to snow distribution and/or thickness are hard to model and/or to measure using geospatial techniques. In terms of Arctic hydrology, we consider three aspects of snow important to understanding processes operating within the ocean‐sea‐ice‐atmosphere interface: i) the average magnitude of snow thickness on sea‐ice; ii) the spatial distribution of snow as a function of location and ice type; and iii) the seasonal evolution of both magnitude and distribution. In this paper we focus on the second aspect; distribution. The distribution patterns of snow over first‐year (FYI), multiyear (MYI) and rubble (RI) sea‐ice were evaluated at 15 sites, sampled during two years of field research in the Canadian Arctic. A geostatistical technique known as the variogram was used to model the statistical pattern of the snow distribution. The significance of different snow distribution patterns was then evaluated using a radiative transfer model under various snow and ice type distributions. Results of this study indicate that the variogram provided a good estimate of the type and change of spatial dependence of snow depths over various types of sea‐ice. Over FYI, the regular smooth ice topography produced a periodicity in the snow drifts which was best estimated using a wave (hole‐effect) theoretical variogram in combination with a Gaussian model. The more uneven ice topographies characteristic of MYI and RI produced a more irregular snow drift pattern. The most appropriate models were a combination of the spherical and Gaussian variogram models (MYI sites) or a single Gaussian model (RI sites). The nugget values of the variograms increased as the sea‐ice topography became more irregular (smooth FYI to large uplifted ice pieces in RI). This was attributed to the presence of snow drifts in the MYI and RI sites that were less than the sampling interval. Geometric anisotropy was present in all 15 sites, indicating a directional trend in the spatial continuity of the snow distribution patterns which we attribute to the prevailing wind direction during depositional storm events. The ramifications of the snow distribution as a function of ice type were illustrated by the transmission of photosynthetically active radiation (PAR) through the three ice types. As the ice topography becomes more irregular, the areally averaged transmission of PAR decreases, thereby illustrating the non‐linear nature of the relationship between PAR extinction and snow thickness. The findings of this case study suggest that by knowing the type of sea‐ice we can make predictions about the statistical pattern of the associated snow distribution. More importantly, the main finding suggests that this snow distribution pattern will dominate the areally averaged transmission of PAR across the ocean‐sea‐ice‐atmosphere interface.

氷水の局部圧力損失特性と分岐特性 : 空調設備における氷水搬送システムの研究 その2

Ice/water mixture can transport much greater amount of cooling energy than ordinary water pipings. To find a basic flow characteristics of the ice/water mixture, the model experiments were performed about the flow characteristics at the bend piping and branch piping. It was found that the local pressure loss of the ice/water mixture at the bend was not affected so much by the ice packing factor nor the direction of bend piping, however some influence of the size of ice piece was found. At the branch piping, the amount of the ice in the branch pipe was influenced by branch directions. The amount of branched ice was increased at the downward branch. It was decreased at the upward and horizontal branch.

Cold tolerance in hatchling painted turtles (Chrysemys picta): supercooling or tolerance for freezing?

We studied tolerance for cold in hatchling painted turtles (Chrysemys picta) from Lake Metigoshe, Bottineau County, North Dakota, to determine whether neonates in populations near the northern limit of distribution rely on a tolerance for freezing or on a capacity for supercooling to survive their first winter of life. We placed hatchlings individually into artificial hibernacula constructed in jars of damp, loamy sand and then cooled the jars to approximately -0.45 degrees C, which was below the equilibrium freezing point for water held by the sand but above that for body fluids of the neonatal turtles. A piece of ice next was placed on the surface of the sand in each jar to induce freezing of the soil water. After the soil water had frozen to an equilibrium, the temperature in the jars was lowered by 1 degrees C/d to minima averaging -2.5 degrees C, -4.5 degrees C, -6.5 degrees C, and -10.5 degrees C in different treatments. These temperatures were maintained for varying periods, so that animals in each treatment were exposed to temperatures below the equilibrium freezing point for their body fluids for a total of 11 d. Thirty of 32 hatchlings survived exposure to -2.5 degrees C; 24 of 32 survived at -4.5 degrees C; 14 of 32 withstood -6.5 degrees C; and 7 of 32 tolerated -10.5 degrees C. Freezing exotherms were detected in temperature profiles for turtles that succumbed but not in those for hatchlings that survived. Thus, the ability of hatchlings to withstand subzero temperatures for extended periods apparently requires that they avoid freezing. Although other workers contend that tolerance for freezing is the key to survival over winter by hatchling painted turtles from the region of Lake Metigoshe, our findings indicate that neonates rely primarily on their ability to remain unfrozen and supercooled.

Low-Cost Ice-Control Structure

Communities located on small, northern rivers can experience severe breakup ice jams. While flood damages may be significant locally, they are often insufficient to justify the cost of conventional flood-control structures. Environmental concerns also tend to render these structures unattractive. A new, low-cost structure appears to be well suited to control breakup ice jams on small rivers. It consists of massive sloped blocks, partially buried in riprap, placed across the river adjacent to a natural floodplain. The blocks will arrest a breakup ice run and form a stable, partially grounded ice jam. Trees or boulders on the floodplain retain ice pieces in the river channel while allowing flow to bypass the structure. Large gaps between blocks allow easy fish and canoe passage. Refrigerated hydraulic model tests indicate that the structure should perform well even during severe breakup events. A prototype built in Hardwick, Vt., has performed well during the four mild breakup events experienced to date. Its cost of $3,600/m of river width represents about an order-of-magnitude reduction compared with previous ice-control structures.

The nature of noctilucent clouds and the Earth’s ozone layer

It has been revealed theoretically that hydrogen self-ignites at a height of120 km and burns up nearly completely at heights of165–200 km. Still higher, its concentration falls off in proportion to pressure because of burning and, therefore, hydrogen does not leave the terrestrial atmosphere. The water vapor that forms during hydrogen combustion descends and changes, under definite temperature conditions, to very small pieces of ice at a height of ∼85 km, the number of which is enough to form noctilucent clouds which are easily observable in twilight. Atomic oxygen forms during the same process of hydrogen combustion. Atomic oxygen combines with molecular oxygen to form ozone. It is noted that the power of this source of ozone is proportional to the hydrogen concentration near the Earth’s surface and can be higher than that of all other sources. Apparently, this circumstance will make it necessary to develop a new approach to clarify the causes of the appearance of the ozone layer and ozone “holes.” The energy released during hydrogen combustion is sufficient to account for the existence of the thermosphere.

Dramatic Demonstration of Oxygen Sensing by Luminescence Quenching

Luminescence-based oxygen sensors are of great interest, especially in biomedical areas, but explaining their operation to the inexperienced can be difficult. We describe a dramatic demonstration that illustrates the principles of oxygen sensors using luminescence quenching of a transition metal complex, either [Ru(bpy)3]Cl2, (bpy= 2,2'-bipyridine) or [Ru(Ph2phen)3]Cl2, (Ph2phen = 4,7-diphenyl-1,10-phenanthroline). The demonstration is simple, quick, and comprehensible even by non-chemists. It requires three solutions of the Ru(II) complex, a black light, oxygen, and some dry ice. One solution is air saturated and two are oxygen saturated. The visual differences in emission intensity for the different oxygen concentrations are easily discernible even to a large audience. By dropping a piece of dry ice into one of the oxygen saturated solutions, the oxygen is removed in seconds, and a spectacular increase in emission intensity can be observed. Students and faculty alike find this a clever demonstration of quenching and its analytical applications.

A Study on Effect of Bow Shape on Icebreaking Resistance

In the 1st report, it was shown that the icebreaking resistance at low ship speed is proportional to the total crack length independently of the bow shape, and is determined by the tangent of hull stem angle at the hull/ice contact point. The effect of bow shape on the icebreaking resistance is investigated in detail by analyzing the results of extensive model experiment with three different bow forms. The icebreaking resistance is obtained by subtracting the resitance in pre-sawn ice from that in level ice.This paper studies the speed dependency of icebreaking resistance, i.e. the increase of icebreaking resistance with ship speed, comparing it with the vertical motion of ship bow. The major results are as follows : (1) As the ship speed increases, icebreaking resistance increases as a linear function of bow vertical motion. A spoon bow shows the lowest speed dependency, a wedge-shaped bow is the second, and a concave bow is the highest. The icebreaking resistance nondimensionalized by ice flexural strength, ice thickness and tangent of stem angle at the hull/ice contact point increases linearly with the heave amplitude at bow nondimensionalized by ice thickness, independently of the bow shape.(2) Frequency analyses of resistance and bow heave have shown three origins of icebreaking resistance. They are (a) resistance due to hull motion, (b) resistance due to icebreaking at the shoulder, and (c) resistance due to icebreaking at the bow center. The former two components are large in case of the wedge-shaped and concave bows. The third component is large in case of the spoon bow.(3) The rotation of broken ice piece is closely related to ship motion and broken ice piece size and shape. Such ice/ship motion coupled resistance can not be well removed by a pre-sawn ice test.(4) The resistance increase due to broken ice piece rotation is determined by the rotation speed and broken ice piece shape. The rotation speed depends on the hull inclination angle at hull/ice contact point. The broken ice piece shape depends on the bow waterline angle and curvature.(5) Because of the above-mentioned relationship between bow shape and broken ice piece, the wedge-shaped and concave bows produce very large and long ice pieces at the shoulder and the ice piece rotation speed is high, while the spoon bow gives wider but shorter (less slender shaped) ice pieces whose rotation speed is low. This is the reason why the spoon bow shows the lowest speed dependency of ice resistance.

Experiments on the damage process in ice under compressive states of stress

AbstractDuring ice-structure interaction, ice will fail in a brittle manner dominated by two processes. The first corresponds to the formation of macrocracks and the consequent spalling-off of large ice pieces. The second includes an intense shear-damage process in zones, termed critical zones, where high pressures are transmitted to the structure. The shear-damage process results in microstructural changes including microcrack formation and recrystallization. A range of tests on laboratory-prepared granular ice have been conducted to determine the fundamental behaviour of ice under various stress states and stress history, particularly as it relates to changes in microstructure. The test series was designed to study three aspects: the intrinsic creep properties of intact, undamaged ice; the enhancement of creep and changes in microstructure due to damage; and the effects of different stress paths. Tests on intact ice with triaxial confining pressures and low deviatoric stresses, aimed at defining the intrinsic creep response in the absence of microcracking, showed that an accelerated creep rate occurred at relatively low deviatoric stresses. Hence, a minimum Creep rate occurred under these conditions. Recrystallization to a smaller grain-size and void formation were observed. Ice damaged uniaxially and triaxially prior to testing showed enhancement of creep under both uniaxial and triaxial loading conditions Creep rates in triaxially damaged ice were found to be non-linear with high deviatoric stresses, corresponding to a power-law dependence of creep rate. Uniaxially damaged specimens contained microcracks parallel to the stressed direction which tended to close under triaxial confinement. Damage under triaxial conditions at low confining pressures produced small recrystallized grains near zones of microcracking. At high confining pressures, a fine-grained recrystallized structure with no apparent cracking was observed uniformly across the specimen. The recrystallization process contributes significantly to the enhanced creep rates found in damaged specimens.

Experiments on the damage process in ice under compressive states of stress

AbstractDuring ice-structure interaction, ice will fail in a brittle manner dominated by two processes. The first corresponds to the formation of macrocracks and the consequent spalling-off of large ice pieces. The second includes an intense shear-damage process in zones, termed critical zones, where high pressures are transmitted to the structure. The shear-damage process results in microstructural changes including microcrack formation and recrystallization. A range of tests on laboratory-prepared granular ice have been conducted to determine the fundamental behaviour of ice under various stress states and stress history, particularly as it relates to changes in microstructure. The test series was designed to study three aspects: the intrinsic creep properties of intact, undamaged ice; the enhancement of creep and changes in microstructure due to damage; and the effects of different stress paths. Tests on intact ice with triaxial confining pressures and low deviatoric stresses, aimed at defining the intrinsic creep response in the absence of microcracking, showed that an accelerated creep rate occurred at relatively low deviatoric stresses. Hence, a minimum Creep rate occurred under these conditions. Recrystallization to a smaller grain-size and void formation were observed. Ice damaged uniaxially and triaxially prior to testing showed enhancement of creep under both uniaxial and triaxial loading conditions Creep rates in triaxially damaged ice were found to be non-linear with high deviatoric stresses, corresponding to a power-law dependence of creep rate. Uniaxially damaged specimens contained microcracks parallel to the stressed direction which tended to close under triaxial confinement. Damage under triaxial conditions at low confining pressures produced small recrystallized grains near zones of microcracking. At high confining pressures, a fine-grained recrystallized structure with no apparent cracking was observed uniformly across the specimen. The recrystallization process contributes significantly to the enhanced creep rates found in damaged specimens.

A predictive model for underwater noise level variations with an application to the fracturing of sea ice

A model of the thermal fracturing of the sea is coupled with a model of acoustic propagation in ice and the underlying water to provide a means of predicting underwater noise variations with time. Numerical simulations using the ice-fracturing model provides a time history of the number of fractures per time step, as well as the location of the fracture relative to the surface of the ice. An analytical model is presented that relates such fracturing within an ice floe to noise levels at a given frequency in the water column under the ice. This model accounts for temporal and spatial variations of the elastic modulus of the ice. The analytical solution predicts that most thermally induced, under-ice noise at 500 Hz is a result of fracturing occurring between 5 and 25 cm below the ice surface for a 1.6-m-thick piece of sea ice. When used in conjunction with the fracture time histories determined by the rheological model, the under-ice noise levels predicted by the analytical solution compare quite well with noise observations in the eastern Arctic Ocean.

A simple experiment for demonstration of phase diagram of carbon dioxide

A simple experiment for demonstration of phase diagram of carbon dioxide has been developed. The experiment involves the compression of small pieces of dry ice and carbon dioxide gas mixture in a 1-mL tuberculin syringe with the needle end of the syringe sealed. During the course of the experiment, equilibrium exists from between solid and gas, to solid, liquid and gas, and finally to liquid and gas phases of carbon dioxide. The experiment is simple and easy to perform and can be completed in minutes.