Ice blocks from Norway: the importation of natural ice to Britain, Circa 1870–1925

Abstract. Grain growth can modify the microstructure of natural ice, including the grain size and crystallographic preferred orientation (CPO). To better understand grain-growth processes and kinetics, we compared microstructural data from synthetic and natural ice samples of similar starting grain sizes that were annealed at the solidus temperature (0 ∘C) for durations of a few hours to 33 d. The synthetic ice has a homogeneous initial microstructure characterized by polygonal grains, little intragranular distortion, few bubbles, and a near-random CPO. The natural ice samples were subsampled from ice cores acquired from the Priestley Glacier, Antarctica. This natural ice has a heterogeneous microstructure characterized by a considerable number of air bubbles, widespread intragranular distortion, and a CPO. During annealing, the average grain size of the natural ice barely changes, whereas the average grain size of the synthetic ice gradually increases. These observations demonstrate that grain growth in natural ice can be much slower than in synthetic ice and therefore that the grain-growth law derived from synthetic ice cannot be directly applied to estimate the grain-size evolution in natural ice with a different microstructure. The microstructure of natural ice is characterized by many bubbles that pin grain boundaries. Previous studies suggest that bubble pinning provides a resisting force that reduces the effective driving force of grain-boundary migration and is therefore linked to the inhibition of grain growth observed in natural ice. As annealing progresses, the number density (number per unit area) of bubbles on grain boundaries in the natural ice decreases, whilst the number density of bubbles in the grain interiors increases. This observation indicates that some grain boundaries sweep through bubbles, which should weaken the pinning effect and thus reduce the resisting force for grain-boundary migration. Some of the Priestley ice grains become abnormally large during annealing. We speculate that the contrast of dislocation density amongst neighbouring grains, which favours the selected growth of grains with low dislocation densities, and bubble pinning, which inhibits grain growth, are tightly associated with abnormal grain growth. The upper 10 m of the Priestley ice core has a weaker CPO and better-developed second maximum than deeper samples. The similarity of this difference to the changes observed in annealing experiments suggests that abnormal grain growth may have occurred in the upper 10 m of the Priestley Glacier during summer warming.

Abstract. The air bubble structure is an important parameter to determine the radiation properties of graupel and hailstones. For 3-D imaging of this structure at micron resolution, a cryo-stage was developed. This stage was used at the tomography beamline of the Swiss Light Source (SLS) synchrotron facility. The cryo-stage setup provides for the first time 3-D-data on the individual pore morphology of ice particles down to infrared wavelength resolution. In the present study, both sub-mm size natural and artificial ice particles rimed in a wind tunnel were investigated. In the natural rimed ice particles, Y-shaped air-filled closed pores were found. When kept for half an hour at −8 °C, this morphology transformed into smaller and more rounded voids well known from literature. Therefore, these round structures seem to represent an artificial rather than in situ pore structure, in contrast to the observed y-shaped structures found in the natural ice particles. Hence, for morphological studies on natural ice samples, special care must be taken to minimize any thermal cycling between sampling and measurement, with least artifact production at liquid nitrogen temperatures.

: Natural and simulated icing tests were conducted during February and March 1978 with a UH-1H helicopter equipped with an advanced ice protection system. This was the fourth program of icing tests accomplished with this test aircraft and the second to include natural icing. The objective of this year's program was to expand the icing test envelope, to gather additional data on ice protection system design and performance characteristics, and to obtain specific data for use in a product improvement program for the UH-1 Partial Ice Protection System (Kit A). The testing was conducted at Ottawa, Ontario, Canada. Seven tests in the spray rig and twelve natural icing flights were made totaling 25.8 hours of icing tests. Icing was encountered on seven of the natural icing flights.

<div class="htmlview paragraph">Sikorsky Aircraft Corporation flew the S-92A® helicopter into natural and tanker artificial icing conditions as part of the certification program for the rotor ice protection system (RIPS). Icing tanker tests were conducted during the late winter of 2004, and natural icing flights were made during the spring of 2004, winter of 2004-05, and early fall of 2005. One goal of the natural icing flight program was to obtain water-dominated icing encounters at temperatures between -15 and -23.33°C. Past studies have shown that mixed-phase icing is often found in this temperature range, and that most icing occurs at temperatures warmer than -15°C. Tanker tests were conducted at specific temperatures at altitudes below about 3 km (10,000 ft), and under prolonged weather conditions meeting visual flight rules (VFR). This represents a challenging combination of conditions to find within a small radius of operation from a given airport.</div> <div class="htmlview paragraph">Weather climatology and forecasting support was provided in an effort to maximize the efficiency of the flight program. During tanker tests, short-term and long-term daily forecasts of temperatures aloft, ceiling, and visibility were needed. They were used to determine if VFR conditions were expected and to optimize the choice of test plan conditions to be attempted. In advance of the natural icing flight campaigns, climatological information was used to aid in the selection of base locations.</div> <div class="htmlview paragraph">Once the aircraft was deployed for flight in natural icing conditions, daily briefings on the expected location, altitude, timing, probability, consistency, temperature, liquid water content, and drop size of the icing conditions were provided. After takeoff, the weather conditions were monitored and provided to the crew in an effort to make the most of the conditions that were available for a given flight. A wide variety of natural icing conditions were sampled in stratiform and stratocumulus clouds over the twenty-month period of the flight campaign, covering substantial portions of the certification envelope. Several rather difficult points were acquired, including those with liquid water contents as high as 1.0 gm<sup>-3</sup> and temperatures as cold as -23°C.</div>

<strong class="journal-contentHeaderColor">Abstract.</strong> Grain growth can modify the microstructure of natural ice, including the grain size and crystallographic preferred orientation (CPO). To understand better grain-growth processes and kinetics, we compared microstructural data from synthetic and natural ice samples that were annealed at ice-solidus temperature (0 &ordm;C) to successfully long durations. The synthetic ice has a homogeneous initial microstructure, which is characterised by polygonal grains, little intragranular distortion and bubble content, and a near-random CPO. The natural ice samples were sub-sampled from ice cores acquired from the Priestley Glacier, Antarctica; they have a heterogeneous microstructure, which is characterised by a considerable number of air bubbles, widespread intragranular distortion, and a preferred crystallographic alignment. During annealing, the average grain size of natural ice barely changes, whilst the average grain size of synthetic ice gradually increases. This observation suggests grain growth in natural ice can be much slower than synthetic ice; the grain-growth law derived from synthetic ice data cannot be directly applied to estimate the grain-size evolution in natural ice. The microstructure of natural ice characterised by many bubbles pinning at grain boundaries. Previous studies suggest bubble pinning reduces the driving force of grain boundary migration, and it should be directly linked to an inhibition of grain growth observed in natural ice. As annealing progresses, the number density (number per unit area) of bubbles on natural-ice grain boundaries decreases, whilst the number density of bubbles in grain interior increases. This observation indicates that some ice grain boundaries sweep through bubbles, which should weaken the bubble-pinning effect and thus enhance the driving force for grain boundary migration. Consequently, the grain growth in natural ice might comprise more than one stage and it should correspond to more than one set of grain-growth parameters. Some of the Priestley ice grains become abnormally large during annealing. We suggest the bubble-pinning, which inhibits the grain growth of ice matrix, and the contrast of dislocation-density amongst neighbouring grains, which favours the selected growth of individual grains with low dislocation densities, are tightly correlated with the abnormal grain growth.

<strong class="journal-contentHeaderColor">Abstract.</strong> Grain growth can modify the microstructure of natural ice, including the grain size and crystallographic preferred orientation (CPO). To understand better grain-growth processes and kinetics, we compared microstructural data from synthetic and natural ice samples that were annealed at ice-solidus temperature (0 &ordm;C) to successfully long durations. The synthetic ice has a homogeneous initial microstructure, which is characterised by polygonal grains, little intragranular distortion and bubble content, and a near-random CPO. The natural ice samples were sub-sampled from ice cores acquired from the Priestley Glacier, Antarctica; they have a heterogeneous microstructure, which is characterised by a considerable number of air bubbles, widespread intragranular distortion, and a preferred crystallographic alignment. During annealing, the average grain size of natural ice barely changes, whilst the average grain size of synthetic ice gradually increases. This observation suggests grain growth in natural ice can be much slower than synthetic ice; the grain-growth law derived from synthetic ice data cannot be directly applied to estimate the grain-size evolution in natural ice. The microstructure of natural ice characterised by many bubbles pinning at grain boundaries. Previous studies suggest bubble pinning reduces the driving force of grain boundary migration, and it should be directly linked to an inhibition of grain growth observed in natural ice. As annealing progresses, the number density (number per unit area) of bubbles on natural-ice grain boundaries decreases, whilst the number density of bubbles in grain interior increases. This observation indicates that some ice grain boundaries sweep through bubbles, which should weaken the bubble-pinning effect and thus enhance the driving force for grain boundary migration. Consequently, the grain growth in natural ice might comprise more than one stage and it should correspond to more than one set of grain-growth parameters. Some of the Priestley ice grains become abnormally large during annealing. We suggest the bubble-pinning, which inhibits the grain growth of ice matrix, and the contrast of dislocation-density amongst neighbouring grains, which favours the selected growth of individual grains with low dislocation densities, are tightly correlated with the abnormal grain growth.

<strong class="journal-contentHeaderColor">Abstract.</strong> Grain growth can modify the microstructure of natural ice, including the grain size and crystallographic preferred orientation (CPO). To understand better grain-growth processes and kinetics, we compared microstructural data from synthetic and natural ice samples that were annealed at ice-solidus temperature (0 &ordm;C) to successfully long durations. The synthetic ice has a homogeneous initial microstructure, which is characterised by polygonal grains, little intragranular distortion and bubble content, and a near-random CPO. The natural ice samples were sub-sampled from ice cores acquired from the Priestley Glacier, Antarctica; they have a heterogeneous microstructure, which is characterised by a considerable number of air bubbles, widespread intragranular distortion, and a preferred crystallographic alignment. During annealing, the average grain size of natural ice barely changes, whilst the average grain size of synthetic ice gradually increases. This observation suggests grain growth in natural ice can be much slower than synthetic ice; the grain-growth law derived from synthetic ice data cannot be directly applied to estimate the grain-size evolution in natural ice. The microstructure of natural ice characterised by many bubbles pinning at grain boundaries. Previous studies suggest bubble pinning reduces the driving force of grain boundary migration, and it should be directly linked to an inhibition of grain growth observed in natural ice. As annealing progresses, the number density (number per unit area) of bubbles on natural-ice grain boundaries decreases, whilst the number density of bubbles in grain interior increases. This observation indicates that some ice grain boundaries sweep through bubbles, which should weaken the bubble-pinning effect and thus enhance the driving force for grain boundary migration. Consequently, the grain growth in natural ice might comprise more than one stage and it should correspond to more than one set of grain-growth parameters. Some of the Priestley ice grains become abnormally large during annealing. We suggest the bubble-pinning, which inhibits the grain growth of ice matrix, and the contrast of dislocation-density amongst neighbouring grains, which favours the selected growth of individual grains with low dislocation densities, are tightly correlated with the abnormal grain growth.

<strong class="journal-contentHeaderColor">Abstract.</strong> Grain growth can modify the microstructure of natural ice, including the grain size and crystallographic preferred orientation (CPO). To understand better grain-growth processes and kinetics, we compared microstructural data from synthetic and natural ice samples that were annealed at ice-solidus temperature (0 &ordm;C) to successfully long durations. The synthetic ice has a homogeneous initial microstructure, which is characterised by polygonal grains, little intragranular distortion and bubble content, and a near-random CPO. The natural ice samples were sub-sampled from ice cores acquired from the Priestley Glacier, Antarctica; they have a heterogeneous microstructure, which is characterised by a considerable number of air bubbles, widespread intragranular distortion, and a preferred crystallographic alignment. During annealing, the average grain size of natural ice barely changes, whilst the average grain size of synthetic ice gradually increases. This observation suggests grain growth in natural ice can be much slower than synthetic ice; the grain-growth law derived from synthetic ice data cannot be directly applied to estimate the grain-size evolution in natural ice. The microstructure of natural ice characterised by many bubbles pinning at grain boundaries. Previous studies suggest bubble pinning reduces the driving force of grain boundary migration, and it should be directly linked to an inhibition of grain growth observed in natural ice. As annealing progresses, the number density (number per unit area) of bubbles on natural-ice grain boundaries decreases, whilst the number density of bubbles in grain interior increases. This observation indicates that some ice grain boundaries sweep through bubbles, which should weaken the bubble-pinning effect and thus enhance the driving force for grain boundary migration. Consequently, the grain growth in natural ice might comprise more than one stage and it should correspond to more than one set of grain-growth parameters. Some of the Priestley ice grains become abnormally large during annealing. We suggest the bubble-pinning, which inhibits the grain growth of ice matrix, and the contrast of dislocation-density amongst neighbouring grains, which favours the selected growth of individual grains with low dislocation densities, are tightly correlated with the abnormal grain growth.

The ice thermal parameters are the key to reasonably simulating ice phenology, distribution, and thickness, but they have always been a “vulnerable group” in ice research. Technically, it may seem simple to obtain accurate ice thermal property parameters, but in reality, there are numerous impact factors, requiring a rigorous research process. In the 1980s, the thermal conductivity of ice was explored in the field and laboratory, after which there has been no significant progress in China. In this century, mathematics is introduced, after which the inversion identification and analysis with the time-series data of the vertical temperature profiles of ice layers by in situ testing are carried out. The in situ thermal diffusivities of different natural ices were obtained and cross-validated with the inversion identification results. Both natural freshwater ice and sea ice exhibited differences in the thermal diffusivity of the pure ice chosen for the current simulations due to impurities within the unfrozen water among the ice crystals, but the trends are consistent with the results of a small number of laboratory tests on different types of saltwater frozen ice. In this paper, the inversion identification results of the thermal diffusivity of typical ice were selected, and the factors constraining the thermal diffusivities were analyzed. The importance of parameterizing the thermal diffusivity in the phase transition zone of ice under the trend of global warming was illustrated. Future research ideas on the physical mechanism, application value, and parameterization scheme of the thermal diffusivity of natural ice were envisaged.

Ice model-scale tests are a frequently used mean to assess and predict the performance of ships and structures in ice. However, ice model-scale tests may not be treated as a black-box where any full-scale scenario can be tested and a Froude-scalable result is obtained. Prior to scaling a thorough analysis of the physical processes is required and whether they can be transferred to full-scale. Model-scale ice is an empirically developed compound-material, consisting of frozen water, voids of air and other artificial dopants. The model ice manufacturing process and dopant amounts have been adjusted to achieve Froude-scalability for the ice thickness and certain force response levels, i.e. ice resistance tests of ships breaking ice in the bending mode. However, not much is known about the internal mechanical processes of model-scale ice and how the scaled force levels are reached. This may add uncertainty to ice model tests and their application on new fields. Recent research indicated that the internal mechanics of model-scale ice and natural sea ice are different, which is also challenging some of the existing scaling approaches. Mechanical specimen tests in full-scale and model-scale are usually compared by stresses, i.e. relating the failure load to the cross-sectional properties. However, depending on the tests different stress combinations might lead to failure, such as different geometries and dimensions may cause qualitatively different stress distribution, which ultimately limits the comparability of the tests. Subsequently, this paper presents a qualitative assessment on selected topics to assess the differences of model-scale ice and natural ice and the influence of the specimen geometry. Furthermore, existing scaling approaches are discussed in context with recent research findings.

This paper presents a new method for determining the microstructural location of impurities in polycrystalline ice, which involves allowing the ice to sublimate under vacuum and then identifying the concentrated impurities using energy dispersive X-ray microanalysis in a low-vacuum scanning electron microscope. The method allows the presence of impurities in both the grain boundaries and the lattice of natural polycrystalline ice to be observed. Using this technique on natural ice, filaments consisting chiefly of NaCl were observed in some grain boundaries, small amounts of sulfur and chlorine were found in the grain interiors of the ice, and large concentrations of sulfur were observed in inclusions.

An experimental method is described to measure and compare the convective heat transfer coefficient of natural and simulated ice accretion roughness and to provide a rational means for determining accretion-related enhanced heat transfer coefficients. The natural ice accretion roughness was a sample casting made from accretions at the NASA Lewis Icing Research Tunnel (IRT). One of these castings was modeled using a Spectral Estimation Technique (SET) to produce three roughness elements patterns that simulate the actual accretion. All four samples were tested in a flat-plate boundary layer at angle of attack in a dry wind tunnel test. The convective heat transfer coefficient was measured using infrared thermography. It is shown that, dispite some problems in the current data set, the method does show considerable promise in determining roughness-induced heat transfer coefficients, and that, in addition to the roughness height and spacing in the flow direction, the concentration and spacing of elements in the spanwise direction are important parameters.

This paper describes the ‘method used to drill an expendable delineation well from an ice platform 8 miles offshore in the Hecla and Gripe? Bay of the Arctic Ocean. Planning pf the Panarclic Tonn etal CS W Hecla N-52 well began in early 1978. However, a considerable amount of horizontal ice movement data had been collected in 1971 and 1972 in several areas of the Arctic Islands to determine the feasibility of drilling from the ice in the latter months of the’ Winter.(1) The design and construction of the ice platform, the drilling 1'ig selected for the project, the subsea equipment used and the sequence of operations which were followed to drill the Hecla N-52 well are presented in the paper Flooding of the ice platform began on November 28, 1973 and was completed on February 3, 1974. The Hecla, N-52 well was spudded on March 6 and the rig was released on April 15, 1974. Performance of the ice platform and the special subsea equipment used during the drilling period is reviewed. Operating experience gathered from the Hecla N-52 well demonstrates that drilling an offshore well in. certain areas of the Arctic Ocean from the ice is feasible. Introduction IN ITS OPERATIONS OVER the past five years, Panarctic Oils Ltd. has used heavy aircraft on ocean ice airstrips and moved heavy loads by truck across the ocean ice between islands, recognizing that the thick. ocean ice is capable of being used to advantage in the late winter months. Ice strength calculations indicated that it should be possible to drill offshore wells using the ocean ice as a platform for a conventional landtype rig. The feasibility of drilling offshore with a slim-hole land rig was demonstrated in the spring of 1973 when a small 150-ton Gardner-Denver 2000 drilling rig was used to drill four stratigraphic tests ranging in depth from 833 to 1700 feet in Kristoffer Bay near Ellef Ringnes Island. The wells were drilled from 1 to 3.5 miles from shore in water depths ranging from 137 to 290 feet. Natural ocean ice, ranging in thickness from 6 to 8 feet, proved to be adequate to support the weight of the rig, for the average 8-day drilling period, with no problems. Successful completion of the stratigraphic test program, and the results of a load test conducted on natural ice (discussed later in this paper), led to the drilling of the Panaretie Tenn etal CS W Hecla N-52 well in 1974. The expendable delineation well was drilled to a depth of 3080 feet in a known gas field using a conventional rig capable of drilling to 6000 feet, Because the weight of the rig could not be supported by natural ice thickness, an ice platform had to be constructed. Geographic Location The Hecla N-52 wellsite is located in the Hecla and Griper Bay, 1800 miles north of Calgary, 950 miles south of the North Pole and 8 miles east of the Sabine Peninsula on Melville Island, N.W.T. as shown in Figures 1 and 2.

: Natural and artificial icing tests were conducted on a JUH-1H helicopter. An ice phobic coating was applied to both the main and tail rotor blades. A total of 4.0 productive hours were flown in the artificial environment, and 9.3 hours in natural icing conditions. Artificial tests were conducted utilizing the Helicopter Icing Spray System (HISS) with ambient temperatures ranging from -6 to -23 deg C, and relative humidities of 60 to 90 percent. Natural icing tests were conducted within the ambient temperature range of -2 to -12.5 deg C, with liquid water contents (LWC) ranging from 0.1 to 0.32 gm/ cu m. The artificial icing tests verified proper operation of the test helicopter ice protection system for use as a safety device in subsequent tests. Natural icing tests were conducted to determine the operational potential of G661 ice phobic compound and to gather data to aid in defining icing phenomenon and ice protection equipment design requirements. Due to insufficient quantitative baseline UH-1H rotor blade icing data, it was not possible to determine if the G661 ice phobic compound affected the operational icing capability of the UH-1H helicopter. Nine minor asymmetric ice sheds were encountered, however, no predetermined limit conditions were reached during testing. Excessive equipment and man-hour requirements degrade the practicality of G661 use. The LWC indicators were not adequate to determine ice accretion level and the Integrating Rate Unit (IRU) did not provide a repeatable cue of impending asymmetric ice shed.

Mechanics and microstructure of deformed natural anisotropic ice