bluuebunny/crossref_metadata_2025 huggingface dataset:
Ice Accretion Under Natural and Laboratory Conditions
Authors: Itagaki K. , Lemieux G. E. , Bosworth H. W.
Published: September 2017

To compare results of icing studies conducted in wind tunnels with natural icing conditions, a series of rotor icing studies were made on top of Mt. Washington, New Hampshire. The results indicated that considerable differences exist between the two under conditions of similar liquid water content and temperature. The wet-to-dry growth transition temperature, for instance, with comparable temperature and liquid water content, may be more than 10°C higher under natural conditions than in wind tunnel studies. The possible cause of such discrepancies was found to be the vapor saturation existing in most laboratory experiments. The transition temperature of ice accretion measured in natural fog on board an aircraft agreed better with the results of the Mt. Washington study.
Formation Mechanisms of Snow Crystals at Low Temperature
Authors: Sato Noboru , Kikuchi Katsuhiro
Published: September 2017

To study crystal shapes, and formation and growth mechanisms of snow crystals formed below -20 °C, a new type of diffusion chamber was constructed. Using this chamber, different kinds of “peculiar shaped” crystals previously observed in nature have been produced, together with normal types of snow crystals. Gohei twins, one of the most typical polycrystalline shapes in nature, have been produced artificially. The vapor pressure was at or near water saturation at the time of nucleation. Analysis of photomicrographs and replicas of Gohei twins that were replicated in the polar regions show that the number frequency of the tip angle has a maximum frequency at about 77° and a minor one at about 54°.

On the basis of these results, a formation mechanism for some Gohei twins is proposed in this paper.
Remote Sensing of Snow in High Mountain Basins in Norway
Authors: Andersen T. , Haakensen N.
Published: September 2017

Information on snow conditions in high mountain river basins is of vital interest for flood predictions and power production. Based on techniques derived for mapping of snow cover from digital NOAA-data, relations are established between snow covered area and remaining snow storage for three basins in southern Norway. Together with estimates of the precipitation and information on maximum accumulated snow, the relation can be useful in run-off predictions for the snow-melt period.
Measurement and Analysis of the Motion of Dense Flow Avalanches
Authors: Salm B. , Gubler H.
Published: September 2017

Continuous avalanche flow speed measurements from start to stop of dense flow avalanches, and localized flow depth and slope perpendicular flow speed profiles, have been measured using X-band radar equipment- Maximum flow speeds of up io 65 m/s have been measured in large avalanches. Comparison of measured flow speeds with Voellmy-type model calculations shows that traditionally chosen sets of parameters, evaluated from runout measurements, cannot model the measured high speeds in the track.

To get an improved quantitative understanding of flowing avalanches, it is proposed that from the start to the stop different flow regimes with different mechanical characteristics are passed through. This is based on theoretical studies of the movement of granular materials, where in adddition to the flow velocity a mean random fluctuation velocity of grains is introduced. A partly or fully fluidized state may be taken according to whether the ratio of frictional to collisional energy loss is smaller or larger than unity. In a third regime the snow is non-fluidized, ie pure gliding of the rigid snow. A good agreement of measurements with the proposed mechanisms is shown.
Effects of Precipitation on the Isotopic Composition of Falling Snow Particles
Authors: Hlgucm K. , Tokuoka A. , Wtanabe O.
Published: September 2017

Observation on the isotopic composition of falling snow particles was carried out at two points 30 km apart in the coastal area of the Sea of Japan, between 20 January to 25 February 1983. Sampling periods of snow particles were from 10 minutes to several hours. Time variation of 6 hours running mean of δ18O values showed good correlation with the variation of surface air temperature. The δ18O value is maximal at the beginning of a snowfall, except when large graupels were observed at the beginning. Comparison of the results between the two observation points showed that the differences in the δ18O values are great when precipitation is plentiful and precipitation cells are small.
Visibility in Blowing Snow Observed by the Luminance Contrast
Authors: Ishtmoto Keishi , Fukuzawa Yoshifumi
Published: September 2017

The effect of surrounding luminance on visual range in blowing snow condition was investigated in daytime, by comparing visibility derived from luminance contrast with that derived from transmissivity observed simultaneously. A volume of air sampled for monitoring may not accurately represent the atmosphere from which it was taken. Differences in measurements through two types of visibility meters increased from daytime to twilight, and with cloudy or lightly blowing snow conditions in daytime. In heavy blowing snow, visual range measured by transmissivity coincided with that by luminance contrast.

We was concluded that visual range obtained by transmissometer was inclined to be over-estimated in conditions of cloud and light blowing snow.
Hardness of Wet Snow
Authors: Izumi Kaoru , Akitaya Eizi
Published: September 2017

Dependence of Kinosita’s hardness R of wet snow on its dry density ρd and free water content W was obtained in the following form

where a, b and c are constants. When wet snow was qualitatively classified into two types, I (coarse-grained granular) and II (new and fine-grained compact) and the constants were determined separately for each type, the correlation coefficients of the above relation were high except between In R and W for snow I. For further investigation of the effect of W on R, a dry snow sample was prepared and R was measured before and after water addition. Aging effect on R was also investigated.
Macropores in Snowpacks of Sierra Nevada
Authors: Kattelmann Richard
Published: September 2017

Macropores - large open channels that can conduct water - have been found within snowpacks of the Sierra Nevada of California. Extensive networks of channels as well as apparently isolated single channels have been documented. These openings, which are usually found near the base of the snowpack, were recognized at several widespread sites. Such basal channels may be an important means of draining liquid water from the snowpack. The presence of open conduits in snow helps to explain such phenomena as rapid streamflow response to percolating rain and melt water.
Mechanical Properties of First Year Sea Ice in Saroma Lagoon
Authors: Matsushita Hisao , Yashima Nobuyoshi
Published: September 2017

This paper deals with compressive strength vs temperature characteristics (-40 ºC to -2ºC), size effect (cross-sectional area of test specimen) and probability distribution of compressive strength and fracture toughness KIC (corresponding to notch effect in bending strength), of first year sea ice sampled from Saroma Lagoon. The main experimental results are as follows. (1) Temperature dependent compressive fracture modes: at temperatures of -20 ºC to 0ºC, crush fracture is dominant, and at temperatures of -40 ºC to -20 C, brittle fracture is dominant. (2) The larger the cross-sectional area of a test specimen, the lower the compressive strength becomes. It is inferred that the number of weak spots increases with increase in the cross-sectional area of the test piece, which thus becomes more susceptible to fracture. (3) The scatter of compressive strength can be approximated by a normal distribution curve. (4) The KIC values of sea ice are below 10 kg/cm2cm, though they change slightly depending on the dimensions of test pieces, the relative angle between crystal growth direction and load direction, environmental condition (air or water), and testing method.
Thickness and Structure of Antarctic Sea Ice Measured by Drilling and Impulse Radar
Authors: Ohmae Hirokazu , Nlshio Fumihiko
Published: September 2017

Sea ice thickness was profiled in investigating the internal structure of sea ice in August 1982 near Syowa Station, East Antarctica, by drilling and using an impulse radar system. In this connection, the anisotropic properties of sea ice were studied by rotating the radar antenna on the horizontal surface of ice around the vertical axis. Ice cores 155 cm long were drilled for analysis of their internal structure, which showed that a brine-soaked layer existed at the depth of 90 cm. This layer corresponded to an internal echo of very strong intensity at this depth that did not change during the rotation of the antenna. Meanwhile, a bottom echo gave maxima and minima approximately every 90 degrees of rotation of the antenna; this alternation is attributable to the structure of newly grown ice with the preferred c-axis Orientation. From these findings we consider that two types of sea ice covered the area near Syowa Station: one with a brine-soaked layer; the other without. Irregularities in shape of the bottom echo suggest that the sea ice plane was composed of accumulated small plates of sea ice.
Net Accumulation and Oxygen Isotope Composition of Snow on Mizuho Plateau. Antarctica
Authors: Satow Kazuhide , Watanabe Okitsugu
Published: September 2017

Characteristics of annual net accumulation were studied in time and space in Mizuho Plateau, Antarctica. Annual variation of net accumulation was obtained from 1914 to 1981 from the analysis of a 30 m core bored in a high accumulation zone. Power spectral analysis of the annual accumulations shows two predominant periodicities, one of 45 years, and the other of 18 years.

Inland, with small accumulation and strong temperature gradient at the surface, developments of depth hoar and the metamorphism of oxygen isotope composition (δ18O) profile of snow take place near the snow surface. From experimental results, the authors propose some models of the metamorphism of δ18O profile of snow with temperature gradient. These models can be divided into two groups: one where a cap, such as an ice crust, is present, and the other without.
Light Attentuation and Visibility in Blowing Snow
Authors: Takeuchi Masao , Fukuzawa Yoshifumi
Published: September 2017

Visibility in blowing snow was investigated by measurements of visibility using optical targets, light attenuation of parallel beam and snow concentration and mass flux of airborne snow particles.

Visibility is thought to be inversely proportional to extinction coefficient of light according to Koschmeider’s equation of visibility. However, visually observed values are not in accordance with those calculated from extinction coefficient of light when visibility is at a very low range. The extinction coefficient of light is proportional to the total cross section of airborne snow particles in a light path. The total cross section is also in proportion to concentration of airborne snow particles. There are many reported investigations of relation between visibility and snow concentration with widely differing results. The extinction coefficient of light varies with the shape and size of the particles, but cannot totally account for observed differences.

Transforming the snow concentration into mass flux of snow particles, a better relation between visibility and mass flux was found. These facts are explained in terms of the size of snow particles which are large enough to be seen. Visibility through visible particles is determined not only by the homogeneous attenuation of light discovered by Koschmeider, but also by the influence of visible particles themselves and their afterimage.
Characteristics of Drifting Snow at Mizuho Station, Antarctica
Authors: Takahashi Sbuhei
Published: September 2017

Observations of drifting snow were carried out at Mizuho Station (70°42'S, 44°20'E, 2230 m above sea level), East Antarctica, in 1982. Drift flux was proportional to about the 8th power of wind velocity above 1 m and about the 4th power below 0.1 m, while snow drift transport rate was proportional to about the 5th power. For drift flux at 1 m height, the power had a temperature dependence, decreasing above -20 °C. Visibility was proportional to about the -8th power of wind velocity; this is explained by the power relation between drift flux and wind velocity. The repose angle of drifting snow particles was observed by the inclination of a cone-shaped deposit on a disk; it was more than 80° when snow was falling and less than 80° without precipitation. The fall velocity of drifting snow particles, obtained by time-marked trajectories of particles, was between 0.3 and 0.9 m/s, and depended on wind velocity and snow particle shape.
Acidity of Snow and its Reduction by Alkaline Aerosols
Authors: Kumai Motoi
Published: September 2017

Snow crystals scavenge aerosols in the atmosphere during the processes of growth and precipitation. Several kinds of flyash are found in acid snow by scanning electron microscope examination. Flyash particles from coal fired electric power plants in Fairbanks, Alaska, were found to be spherical or irregular in shape with a 0.2 to 50μm diameter, and were rich in calcium, silicon, aluminum and iron. The pH of 35 snow samples in Fairbanks ranged from 5.60 to 7.48. The acid snow was changed to alkaline snow by dry fallout of calcium-rich flyash from the electric power plants, which were using calcium-rich Alaskan coal.

Flyash particles from three oil fired heating plants in Hanover, New Hampshire, were spherical and 10 to 80 μm in diameter, with gas escape holes, and were always sulfur rich. The pH values of fresh snow from 44 snowfalls were measured to range from pH 3.96 to 5.45 in Hanover. The mean hydrogen ion concentration was calculated to be 10-448 mol/L for 22 snowfalls in 1980-84, and 10-4 mol/L for 22 snowfalls in 1972-73.
Coupling between the ocean and an ice shelf
Authors: Fox Colin , Squire Vernon A.
Published: September 2017

The possibility of long-period ocean waves coupling to an ice shelf is investigated. A thick elastic plate model is used for the ice shelf with comparisons made to the simpler thin-plate model. The strain set up on the ice shelf by a normally incident single frequency ocean wave is calculated by completely solving the equations governing the velocity potential for such a system. In the absence of measurements on an ice shelf, existing measurements of long-period strain on an ice tongue are used to estimate the required incident amplitude in the open water to induce the observed oscillations. It is found that the height of seas required indicates that ocean wave driving is a plausible forcing mechanism for observed oscillations.
Sedimentary processes may cause fluctuations of tidewater glaciers
Authors: Alley Richard B.
Published: September 2017

A temperate glacier ending in water advances by depositing a moraine shoal, which “dams” tidewater calving, and then recycling this shoal in conveyor-belt fashion. A simple model suggests that conveyor-belt recycling of the shoal must continue until calving stops and all ice flux is removed by surface ablation, or until the glacier retreats rapidly from the shoal; retreat can occur without external forcing if the glacier advances into deepening water and if sediment recycling is rapid compared to supply of new sediment to the moraine shoal.
Massive, ancient sea-ice strata and preserved physical-structural characteristics in the Ward Hunt Ice Shelf
Authors: Jeffries Martin O.
Published: September 2017

Two sea-ice layers, one measured as 9 m thick, the other at least 12 m thick and estimated to be 24.5 m thick, have been located by ice core drilling in the west Ward Hunt Ice Shelf. To examine the preservation of physical-structural characteristics over long time intervals, the crystal structure and brine volumes in the sea ice, which possibly dates back to about 3000 BP, have been studied. The structural characteristics are immediately recognizable as those of undeformed congelation sea ice accreted by Stefan growth. Brine volumes in the ancient sea ice are higher than those in modern multi-year ice at the same temperature. The preservation of brine over a time span of hundreds to thousands of years is attributed to an absence of surface meltwater to effect brine flushing and the very slow, even negligible action of gravity drainage, brine pocket migration and brine expulsion. The congelation structures indicate that sea ice can grow by the Stefan accretion mechanism to thicknesses exceeding the equilibrium thickness (2.5–5 m) of most undeformed multi-year ice. The observed physical-structural characteristics of the Ward Hunt sea ice strongly suggest that many of the properties attained by sea ice are permanent and not affected by slow-acting physical processes.
A quasi-analytical model for the under-ice boundary layer
Authors: McPhee Miles G.
Published: September 2017

An implicit, analytical model for momentum, heat and salt flux within a sea-ice/upper-ocean system is developed. The model comprises three parts: (a) an equation for turbulent stress in the oceanic boundary layer and upper pycnocline, from which turbulent scalar fluxes are derived; (b) a model for heat and mass transfer in a thin sub-layer near the ice/ocean interface; and (c) a model for momentum flux lost to the internal wave-field if the ice under-surface has large-scale (pressure-ridge keel) relief. Features of the model are demonstrated by simulating response of the ice drift and upper-ocean temperature and salinity structure to constant heating and variable surface stress.
Estimates of ice-edge melt rates off Labrador and eastern Newfoundland, Canada
Authors: Prinsenberg S. J. , Peterson I.K. , Fowler G.A.
Published: September 2017

For the winters of 1985 to 1989, ice-edge melt rates off Labrador and eastern Newfoundland were calculated from ice charts and satellite-tracked ice beacon data. The ice charts provided ice-edge motion and ice thicknesses, while the beacons provided ice-drift rates and rates of ice-edge retreat. Over the continental slope, ice-edge melt rates, ice-drift rates and heat fluxes required to melt the ice were all higher than those over the continental shelf. Ice-edge melt rates had a mean value of 18.0 km d−1 over the slope but reduced to 4.8 km d−1 over the shelf. Similarly, the mean ice-drift rate was higher over the slope (41.5 km d−1) than over the shelf (12.7km d−1). Ice-edge melt rates increased linearly, as ice-drift rates perpendicular to the edge increased. Estimates of heat fluxes (±30%), required to melt the ice at the ice edge, reached values of 700 W m−2 for 3-day periods and had a mean of 340 W m−2 over the slope and 130 W m−2 over the shelf.
Textural characteristics of sea ice and the major mechanisms of ice growth in the Weddell Sea
Authors: Lange M. A. , Eicken H.
Published: September 2017

We report on studies of sea-ice texture conducted during a number of expeditions into the Weddell Sea. Sea ice in the Antarctic is dominated by granular ice of frazil origin in floes of all ages, in contrast to ice in the Arctic, which consists predominantly of columnar ice of congelation origin. The large fraction of granular ice in first-year sea ice is a result of the dominant ice-formation process in the advancing ice edge, the pancake cycle. The dominance of granular over columnar ice in second- and/or multi-year ice is a result of the large degree of deformational activity in the Southern Ocean.
Fatigue-crack growth in fresh-water ice: preliminary results
Authors: Nixon Wilfrid A. , Weber Larry J.
Published: September 2017

Very little data exist on the fatigue behavior of ice, yet fatigue may have an important role to play in a number of ice failure situations. Whilst reversed-bending tests and cyclic-compression tests have been performed on ice, no attempts have been made previously to measure fatigue-crack growth rates in ice. This paper presents the results of fatigue-crack growth experiments on S2 (i.e. columnar grained with the c axes randomly aligned within the horizontal plane) fresh-water ice. There is clear evidence that crack growth has occurred under cyclic loading but, as yet, the data are insufficient to determine the validity of da/dΝ versus δK type behavior. Preliminary results are presented and the implications of the results are discussed.
The kinetic friction of saline ice against itself at low sliding velocities
Authors: Jones D. E. , Kennedy F. E. , Schulson E. M.
Published: September 2017

An experimental investigation was performed on the kinetic friction coefficient of laboratory-grown, columnar saline ice sliding against itself. Tests were performed on a dual-opposing load apparatus specially manufactured for attachment to an MTS testing system. The mean kinetic friction coefficient, μ, was measured for sliding velocities from 10−6 to 5 × 10−2 m s−1 at temperatures from —3° to —40°C under a contact pressure of about 20 kPa. The ice specimens were oriented with grain columns perpendicular to the sliding interface. At -3°C and at —10°C, three distinct regions were observed: from 10−6 to about 10−5ms−1, μwas nearly constant at 0.5; at velocities from 10−5 to 10−3 m s−1, μ began to drop rapidly to about 0.1; and, above 10−3 m s−1, μ began to level off at ~0.05. The velocity at which μ began to decline increased with decreasing temperature. At temperatures below —10°C, μ increased from ~0.5 at v =10−6ms−1 to a peak value of ~0.7 near a velocity of 5 × 10−5ms−1 and then fell rapidly to about 0.1 at 10−2ms−1. In general, μ increased with decreasing temperature and sliding velocity.
Evidence for pressure melting and heat generation by viscous flow of liquid in indentation and impact experiments on ice
Authors: Gagnon Robert E. , Mølgaard John
Published: September 2017

Indentation experiments have been performed on fresh-water ice at -9°C using an apparatus which permitted visual observation of the contact zone at the ice/indentor interface by viewing through the specimens. Analysis of the video records and test data indicated that at least 50% of the energy dissipated during the process of indentation was consumed by pressure melting and heat generation through the rapid viscous flow of the liquid. The thickness of the liquid layer was estimated to be 16/μm and the contact pressure in the melting zone was at least 90 MPa. Video records of small-scale impact tests on ice indicated that the same process of pressure melting and extrusion was taking place.
On the relationship between local stresses and strains in Arctic pack ice
Authors: Tucker W. B. , Perovich D. K. , Hopkins M. A. , Hibler W. D.
Published: September 2017

Local ice strains and in situ ice stresses were simultaneously measured on the Coordinated Eastern Arctic Experiment (CEAREX). The experiment took place in the fall of 1988 and was centered about an ice-strengthened ship moored to a multi-year floe in the pack ice northeast of Spitsbergen. During the period of data collection, which extended from early October to late November, the ship and the ice surrounding it drifted from 82°40′N, 32°32′E to 78°54′N, 31°27′E.

As soon as ice temperatures were low enough to permit installation, stress sensors were placed at four sites, two sites on each of two adjacent multi-year floes. Principal stress components and the principal stress direction were determined at each sensor. At the same time, microwave transponders, capable of measuring ice deformation to accuracies better than 1 m, were positioned within 1 km of the stress sensors and provided an approximation of the local strain field.

What makes this joint dataset particularly interesting is that it includes some large ridging events and a particularly large event which terminated the experiment when the multi-year floes in the local area were broken into small fragments. A wide range of ice stresses was measured during the period. The largest compressive stresses, about 250 kPa, were measured by the near-surface sensors. Although sensors in different locations responded differently to ice movement, the large events were common to all shallow sensors.
Ridge-sail statistics at the shear edge of Lancaster Sound, March 1984
Authors: Sayed M. , Frederking R.M.W
Published: September 2017

Ice-surface geometry at the shear edge of landfast ice has been examined. An aerial survey was conducted at the intersection of Lancaster Sound and Navy Board Inlet during March 1984. Surface profiles were then obtained in three representative areas and used to evaluate height statistics. A region, 150 m wide, at the ice edge was distinct from the rest of the ice cover. In the region at the shear edge, the surface height followed lognormal distributions. The average and maximum heights were 2.3 m and 5.6 m, respectively. In the region inside the shear edge, the height followed negative exponential distributions, with average and maximum values of 1.5 m and 4.2 m, respectively.
An initial numerical investigation of the extent of sea-ice ridging
Authors: Flato Gregory M. , Hibler William D.
Published: September 2017

A two-level, viscous-plastic, sea-ice model is modified to allow ridged and unridged ice to be treated separately. This is accomplished by introducing a third continuity equation with additional terms to transform level ice into ridged ice during deformation. The standard model is run for three years using observed forcing from 1981–83, along with three sensitivity runs, to investigate the role of strength parameterization and energetically consistent deformation on ridge production. As expected, most of the ridging occurs near the coast, with the highest ridged-ice fraction produced off the Canadian archipelago and northern Greenland coast. The sensitivity studies indicate that, although the ridged-ice fraction is very sensitive to the strength parameterization, the lead fraction and total ice volume are much less affected. Requiring the deformation to be energetically consistent with the assumed yield curve almost doubles the amount of ridged ice produced.
On the role of ocean circulation in seasonal and interannual ice-edge variations in the Bering Sea
Authors: Zhang Jinlun , Hibler William D.
Published: September 2017

A 40 km-resolution ice—ocean model of the Bering Sea is used to investigate the effects of ocean circulation and vertical convection on the seasonal and interannual ice extent variations in the Bering Sea. The model is driven with daily time-varying atmospheric forcing from 1981–83. A series of sensitivity studies is carried out to examine the effects of the vertical diffusion and precipitation on the ice margin and the effect of stratification on the ocean circulation. For comparison, an ice-only simulation, with a motionless oceanic boundary layer of fixed depth, is also carried out. In the Aleutian Basin, the ice-ocean model exhibits a cyclonic ocean circulation which consists mainly of a baroclinic current component. On the eastern Bering Sea shelf the flow is mainly barotropic, with a northwestern shelf flow along the Alaskan coast and a return southeastern flow along the shelf break. The seasonal and interannual variability of the ice margin is significantly better simulated by the ice-ocean model than by the ice-only model, especially when an enhanced vertical diffusion is used. However, the seasonal cycle of ice extent exhibits too little ice in the southeastern Bering Sea and excessive ice in the northwest. The advance and retreat of the ice edge also tends to lag behind the observed results by a few weeks. The inclusion of precipitation improves the ice extent in the southeast. The results suggest that an enhanced vertical resolution, together with a more complete boundary layer formulation, will be required to achieve realistic seasonal simulations of the Bering Sea ice–ocean system.
The role of incoming waves in ice-edge dynamics
Authors: Squire Vernon A. , Colin Fox
Published: September 2017

The radiation stress at an ice edge due to incident sea and swell is reconsidered in the light of new theoretical results concerned with the calculation of the reflection and transmission coefficients at the edge of a thin elastic sheet. Both monochromatic seas and seas made up of a spectrum of periods are discussed, the latter invoking the Pierson-Moskowitz spectral model. It is found that the force per unit length due to radiation stress is comparable in magnitude with other driving mechanisms at the edge, i.e. with winds and currents.
Glacioclimatological features in the Tanggula mountains, China
Authors: Yongjian Ding , Zhongqin Li , Shiyin Liu , Xinzhi Yu
Published: September 2017

Air temperature and precipitation data have been obtained from the Geladandong region at the headwaters of the Yangtze River. At the equilibrium line altitude of the glaciers, mean annual and summer air temperatures are –10 to –12.0°C and 1.0 to –1.0°C, respectively. Accumulation on the glaciers on the south side of the Tanggula mountains depends mainly on water vapour transported from the south and southeast. The moisture source for the glaciers on the north side is from the east. Precipitation increases with altitude in the glaciated areas. An estimated annual accumulation in the firn areas is about 400 to 600 mm of water equivalent. The Geladandon region has a cold, dry climate and the glaciers in the region can be classified as continental. The present climatic conditions result in a negative mass budget for most glaciers.
Basal deformation of Ürümqi Glacier No. 1, Tien Shan mountains, China
Authors: Jing Xiaoping , Maohuan Chen , Mingxie Jin , Lorrain R. D.
Published: September 2017

Basal deformation was studied in tunnel 2 in the east tributary of Ürümqi Glacier No. 1, Tien Shan mountains. Beneath the tunnel there is an ice-laden till layer, about 11 m thick and at a sub-freezing temperature. This layer is deformable and provides a significant part of the overall surface motion. The basal velocity in the tunnel gradually decreases from the back wall towards the entrance, with a compressive strain rate ranging from −0.579 to −5.739 × 10−2 a−1. The inclination of the principal strain rate to the horizontal gradually decreases from the back wall towards the tunnel entrance. The study provides data on the longitudinal compression and vertical uplift in the basal ice and ice-laden till layer resulting from interaction of glacier with recently exposed proglacial deposits.
An outline of avalanches in the southeastern Tibet Plateau, China
Authors: Yanlong Wang , Maohuan Huang
Published: September 2017

Avalanches are a widespread hazard that cause serious damage in the southeastern Tibetan Plateau. Abundant solid precipitation and high relief are favourable for avalanche occurrence. The monsoon climate brings a lot of precipitation which, however, is not well distributed. Avalanches are most common around the margins of the plateau. Wet snow avalanches occur most frequently. Based on data on precipitation and topographical relief, a map is drawn showing the areal distribution of avalanche hazards.
Progress and prospect for research on mountain glaciers in China
Authors: Zichu Xie
Published: September 2017

In the past decade the interest of many scientists worldwide has been attracted to the central Asian area of China. A number of gaps in scientific knowledge have been closed, and many significant discoveries have been made.

The most important achievement is the ice-core research by the Sino-American Joint Expedition to the Dunde Ice Cap, Qilian mountains, that established a record of ten thousand years of climatic and environmental change. In addition, in cooperation with scientists from Japan, Switzerland and the Soviet Union, studies have been carried out focusing on glacier mass balance, heat balance, the mechanism and formation of glacial runoff, and high mountain climates. This work has been done in the Tien Shan, west Kunlun, Tanggula, Nyaingentanglha and Gongga mountains.

In addition, through joint efforts of scientists from China, Nepal and Canada, important advances have also been made in studies of glacier lake outburst floods and debris flows in the Karakoram and the Himalayas, and in mountainous areas in southeastern Tibet.

The glaciers in central Asia will continue to be an important research area for glaciologists from all over the world in the coming decade.
Industrial influence on glacial processes in mountains of circumpolar regions
Authors: Grebenets V.I. , Fedoseyev D.B.
Published: September 2017

Industrial activity in the Noril’sk mountains since the 1930s has changed the landscape and formed artificial banks, ridges and terraces. New water courses have been formed and snow has been removed to places where it has accumulated year by year. The ground temperature has increased by 0.3 to 0.5°C down to a depth of 30 to 50 m, melting has increased in the permafrost layer and artificial ground has become more unstable, leading to landslides and mudflows. Material in dumping sites has frozen and turned into rock glaciers, chemical pollutants have accumulated in snow and extremely high concentrations are observed in meltwater during spring. The gravitational instability of mountain and piedmont landscapes increases with human activities and the landscapes thus changed cause greater danger from slumps, mud flows and avalanches.
The use of microwave radiometer data for characterizing snow storage in western China
Authors: Chang A. T. C. , Foster J. L. , Hall D. K. , Robinson D.A. , Peiji Li , Meisheng Cao
Published: September 2017

In this study a new microwave snow retrieval algorithm was developed to account for the effects of atmospheric emission on microwave radiation over high-elevation land areas. This resulted in improved estimates of snow-covered area in western China when compared with the meteorological station data and with snow maps derived from visible imagery from the Defense Meteorological Satellite Program satellite. Some improvement in snow-depth estimation was also achieved, but a useful level of accuracy will require additional modifications tested against more extensive ground data.
Preliminary observations of brittle compressive failure of columnar saline ice under triaxial loading
Authors: Gratz E. T. , Schulson E. M.
Published: September 2017

Experiments were performed on columnar saline ice prepared in the laboratory. Specifically, using a true multiaxial loading system, relatively large cubes (159 mm on edge) were proportionally loaded along three orthogonal directions; viz. perpendicular to (σ13 and σ22) and parallel to (σ33), the long axis of the columnar grains. The ice was strained at 10−2 s at −10°C where it behaved in a brittle mariner. Four sets of experiments were performed by setting the ratio σ22/σ11 to 0, 0.25, 0.5 or 1, and varying the ratio σ22/σ11 and σ22/σ11. Sections through the failure surface were then constructed. For loading along σ22 = 0, the confining stress did not significantly affect the maximum principal stress at failure. For loading along σ22 =0.25σ11, σ22 = 0.5 σ11 and σ22 = 0.5 σ11, the application of a moderate confining stress resulted in a large increase in failure stress. However, further increase in the level of the confining stress did not have a significant effect on the failure stress. The observations are presented in terms of a failure surface and are discussed in terms of the possible failure mechanisms.
The response of a seasonal snow cover to explosive loading
Authors: Johnson Jerome B. , Solie Daniel J. , Barrett Stephen A.
Published: September 2017

An explosive detonation in snow produces high intensity shock waves that are rapidly attenuated by momentum spreading as the snow is compacted. Our experimental measurements and numerical calculations indicate that the maximum shock-wave attenuation in seasonal snow (250 kgm−3) is proportional to between x−1.6 and x−3 for plane waves and x−3 for spherical waves (x is the propagation distance). Outside the region of shock-compacted snow or in air over snow, stresses are transmitted as acoustic/seismic waves. Attenuation of these waves depends on snow permeability and the effective modulus of the ice frame and is proportional to about x−0.7 for plane waves in seasonal snow and to about x−1 for spherical waves in air over seasonal snow. Increasing the scaled detonation height of an explosive up to 2mkgf−1/3 above a snow cover increases the far field (scaled distances greater than about 8m kgf−1/3 snow surface pressures. Scaled detonation heights greater than about 2mkgf−1/3 have little additional effect.
Transient creep of polycrystalline ice under uniaxial compression: an assessment of internal state variable models
Authors: Meyssonnier J. , Goubert A.
Published: September 2017

The efforts to develop damage models for ice cannot be disconnected from a better knowledge of the undamaged ice behaviour. In this respect the transient behaviour of polycrystalline ice still needs to be investigated. The present paper is a contribution to the development of rheological models which can be used in varying load situations. The deformation processes which should be the foundation of the models are described. The models of Le Gac and Duval (1980) and of Sunder and Wu (1989a) are tested against two uniaxial compression tests on isotropic granular ice under varying load. They fail to describe both primary creep and the response to increments/decrements of the applied load. A new model, based on a decomposition of the viscoplastic strain into two components which account separately for kinematic and isotropic hardening, is shown to give better results.
Seasonal trend in suspended-sediment transport from an Arctic glacier, and implications for drainage-system structure
Authors: Hodgkins Richard
Published: September 2017

Suspended-sediment concentration (SSC) and discharge time series have been obtained for a proglacial stream draining from Scott Turnerbreen, a non-temperate glacier at 78° N in the Svalbard archipelago. These time series exhibit seasonal trends in diurnal hysteresis between SSC and discharge, which changes progressively from clockwise (SSC lead) to anticlockwise (SSC lag), and in the availability of sediment for fluvial transport, which increases during the season. These results contrast with those for streams draining temperate glaciers, in which a seasonal trend in diurnal hysteresis is typically not observed, and sediment supply is usually exhausted during the melt season. This contrast indicates differences in the processes of sediment acquisition and in temporal patterns of sediment transport between temperate and non-temperate glaciers, which reflect different drainage-system structures. The principal mechanism of suspended-sediment acquisition by meltwater is subaerial sediment supply to ice-marginal channels at non-temperate glaciers, whereas at temperate glaciers it is subglacial supply to basal channels. The hysteresis trend probably arises from a delaying effect, because of sediment circulation in pools and slack water adjoining the ice-marginal channels, which varies with discharge. Continuing subaerial sediment supply from heavily debris-covered ice-cored moraines during the melt season precludes sediment-supply exhaustion at Arctic glaciers but means that measurements of sediment flux give a misleading indication of the contemporary rate of glacial erosion.
Lumped-element model for subglacial transport of solute and suspended sediment
Authors: Clarke Garry K. C.
Published: September 2017

Present understanding of the subglacial water system and its role in transporting solute and sediment is largely based on subglacial observations of water pressure, turbidity and electrical conductivity and on portal measurements. Such data reveal a wealth of intriguing phenomena, but convincing interpretations can be elusive. Although a proper mathematical description of the subglacial water system would unquestionably lead to a coupled system of non-linear partial differential equations, it is not fruitful to introduce this level of complexity until the important physical processes have been identified and quantified. Lumped-element models offer an efficient approach to examining the complex but dimly perceived physics of the subglacial water system. Water volume, hydraulic head, discharge and flow resistance have the respective electrical analogues of charge, voltage, current and ohmic resistance. Thus, subglacial hydraulic circuits can be approximated by electrical circuits. Mathematically, this circuit description commonly leads to a coupled system of algebraic and differential equations which can be solved numerically. It is straightforward to enrich this representation by adding sources and sinks of solute and sediment. To demonstrate the method, model results are compared to records of subglacial pressure, electrical conductivity and turbidity measured beneath Trapridge Glacier, Yukon Territory, Canada.
Observations of tunnel channels in glacial sediments with shallow land-based seismic reflection
Authors: Pugin A. , Pullan S. E. , Sharpe D. R.
Published: September 2017

A regional hydrogeological study conducted by the Geological Survey of Canada acquired 35 line-km of 12-fold seismic reflection profiles on or adjacent to the Oak Ridges moraine, north of Toronto, Ontario, Canada. The three-dimensional geometry provided by these data aids in understanding the erosional and depositional processes that occurred beneath the Laurentide ice sheet during the late stages of glaciation. The seismic sections indicate large infilled channels in the subsurface which are interpreted as tunnel channels eroded by large, subglacial meltwater discharges. Two seismic profiles from different areas of the moraine show channel-cutting events of different ages and different types of infilling.
Supraglacial debris-transport variability over time: examples from Switzerland and Iceland
Authors: Whalley W.B. , Palmer C.F. , Hamilton S.J. , Kitchen D.
Published: September 2017

The volume of debris in the left-lateral, Little Ice Age (LIA: AD 1550–1850) moraine of the Feegletscher, Valais, Switzerland was compared with the actual volume being transported currently by the glacier. The latter is smaller by a factor of about two. In Tröllaskagi, north Iceland, a surface cover of debris on top of a very slow moving glacier ice mass (glacier noir, rock glacier) has been dated by lichenometry. The age of the oldest part is commensurate with LIA moraines in the area. Knowing the volume of debris of a given age allows an estimate of the debris supply to the glacier in a given time. Again, there appears to have been a significant reduction in debris to the glacier since the turn of the 19th century. Debris input in the early LIA seems to have been particularly copious and this may be important in the formation of some glacier depositional forms such as rock glaciers.
A conceptually based model of the interaction between flowing meltwater and subglacial sediment
Authors: Collins David N.
Published: September 2017

Detailed measurements of sediment flux in meltwaters draining from the portal of Gornergletscher, Valais, Switzerland, each ablation season between 1987 and 1990 indicate the nature of interactions between the developing basal drainage system and sediment stored at the glacier subsole. Sediment-flux maxima, which were generally smaller and less frequent later in a season, occurred at times of rising discharge. Overall, sediment flux first increased then decreased during a season. A simple conceptually based model is proposed for the subglacial interaction between flowing meltwater and sediment derived from glacial abrasion. The model was developed in order to allow investigation of relationships between suspended-sediment flux and discharge in meltwaters draining from temperate glaciers, In the model, water spreads out over a grid-square bed such that the area of subsole integrated with flow is a function of discharge. Sediment is abraded from the bed at a uniform rate in cells not covered by water. In winter, sediment accumulates over almost all the bed. Periods of rising flow at the start of the ablation season lead to drainage net expansion, much entrainment of stored sediment and large flux events in portal meltwaters. The model allows redistribution and deformation of stored sediment in two directions. Sediment squeezed to the margins of the wetted area throughout summer provides the background level of sediment flux between events. Reduction in total channel-margin length with progressive changes in drainage-network topology explains declining background flux later in summer. The model replicates well the timing, but not the absolute and relative magnitudes, of sediment-flux maxima in portal meltwaters draining from Gornergletscher.
Sediment-mass exchange between turbid meltwater streams and proglacial deposits of storglaciären, northern Sweden
Authors: Holmlund Per , Burman Helene , Rost Torbjörn
Published: September 2017

Detailed changes in surface elevation of a recently deglaciated area have been mapped using a high-resolution photogrammetric method, with a view to estimating the contribution of debris from the proglacial area to the meltwater streams draining Storglaciären, northern Sweden, over the period 1980-90. The net contribution of sediments originating from the deglaciated area immediately in front of the glacier was of the order of 50% of the suspended silt load transported by meltwater at the flume Rännan downstream from the glacier, but at the same time, a similar amount of sediment accumulated along the streams. Though there is a significant exchange of mass, the net change is close to zero. Moreover, the survey provides detailed information about morphological changes in the landscape. Different processes, such as melting of permafrost, fluvial erosion and sedimentation, have been active.

Erosion and sedimentation rates were calculated from the difference between digital terrain models based on aerial photographs taken in 1980 and 1990. The result shows erosion in the central part of the proglacial area and accumulation of coarser sediments along the braided streams. In places, the ground is sinking, possibly due to melting of permafrost.

Where the ice is thinner, in the marginal zone, the thermal regime of ice in the tongue of Storglaciären corresponds well with the proglacial geomorphology. At present, the glacier has a 30-40 m thick cold surface layer which at the thinner marginal zone corresponds to a 100-200 m wide frozen rim. The temperature distribution within the ice was mapped using high-resolution radar.
Objective determination of snow-grain characteristics from images
Authors: Lesaffre Bernard , Pougatch Evelyne , Martin Eric
Published: September 2017

The determination of snow-grain characteristics (such as type or size) is crucial for validating snow models and interpreting remote-sensing data. Until now, the size and type of snow grains have been estimated in the field. Nowadays, the transport of a snow sample in iso-octane allows laboratory analyses. The objective analysis of snow-grain digital images has been developed at the Centre d'Études de la Neige since the mid 1980s. The images are taken in a cold room and stored on a video disk. The calculation of the relevant parameters for snow characterization has been developed. Recently, the hardware- and software-systems have been upgraded, allowing quicker and easier analyses. Finally, a procedure designed to determine snow types from image analysis has been developed and calibrated using 65 snow samples. For that purpose, independent experts have determined the snow type (as defined by the International Classification) of each sample. The procedure has been verified using an independent set of snow images. This semi-automated determination gives 97% correct results on granular-snow types. However, it is not reliable for precipitation particles.