A simple model for crystal growth in the ice shell of Europa has been made in order to estimate the size of ice crystals at Europa’s surface. If mass is lost from the surface of Europa due to sputtering processes, and the ice thickness is constant in time, ice crystals will be transported upwards in the ice shell. The crystals will therefore grow under varying conditions through the shell. The model predicts that ice crystals are 4 cm– 80 m across at the surface. For the preferred parameter values, a crystal size of the order of 7 m is calculated.

The first set of sequential measurements by two different sets of satellite altimetry data indicate that the Greenland ice sheet, south of 65.1° north latitude, thickened at the rate of 35 ± 17 cm a−1 during 1975 to 1978. The average change in surface elevation was calculated from the elevation differences determined at 525 locations observed by both GEOS-3 and Seasat radar altimeters. The observed thickening is consistent with the 8 cm a−1 thickening previously measured in the accumulation zone, approximately 900 km farther north, during conventional, surface, survey methods. The increase in ice thickness suggests a higher precipitation than the long-term average, which is one possible result of a warmer climate in polar regions. The excess ice accumulation, in the 10 % of the Greenland ice sheet observed, is estimated to be 53 km3 a−1, which is equivalent to a sea-level reduction of 0.15 mm a−1. Additional, high-precision, sequential, altimetric measurements could be used to determine the overall mass balance of the Greenland and Antarctic ice sheets.

Curvilinear flow stripes appear on aerial photographs and satellite imagery of polar ice. On Byrd Glacier, Antarctica, flow stripes are especially prominent and can be detected on AVHRR imagery down to the ice shelf margin.

Aerial photographs of Byrd Glacier (Brecher, 1986) are used to determine photogrammetrically the relief associated with flow stripes on two transverse profiles separated by a distance of 65 km. Two kinds of stripes are found, topographic and textural flow stripes. Topographic flow stripes are associated with a ridge-trough topography with double amplitudes of 7 m to 45 m and slopes of 1–7 %. The valleys of the topographic flow stripes appear bright in the photographs and correspond to snow-covered areas, while ridges appear in general as dark stripes that correspond to bare ice areas with abundant crevasses. Textural flow stripes correspond to bands of distinct crevasse pattern which are not associated with topography.

The photogrammetric information is correlated with the brightness pattern across flow stripes that appears on Advanced Very High Resolution Radiometer (AVHRR) data. Flow stripes decay rapidly on the AVHRR imagery over the first 40 km downstream from Byrd Glacier and some persist for nearly 400 km to the front of the Ross Ice Shelf.

Velocity was measured across a transect on the upstream photogrammetric profile. There are no velocity discontinuities across the boundaries of flow stripes, which shows that lateral shear between flow stripes is not a valid mechanism for explaining their persistence.

The debris-rich glacier that grew in the crater of Mount St Helens after the volcano’s cataclysmic 1980 eruption was split in two by a new lava dome in 2004. For nearly six months, the eastern part of the glacier was squeezed against the crater wall as the lava dome expanded. Glacier thickness nearly doubled locally and surface speed increased substantially. As squeezing slowed and then stopped, surface speed fell and ice was redistributed downglacier. This sequence of events, which amounts to a field-scale experiment on the deformation of debris-rich ice at high strain rates, was interpreted using a two-dimensional flowband model. The best match between modeled and observed glacier surface motion, both vertical and horizontal, requires ice that is about 5 times stiffer and 1.2 times denser than normal, temperate ice. Results also indicate that lateral squeezing, and by inference lava-dome growth adjacent to the glacier, likely slowed over a period of about 30 days rather than stopping abruptly. This finding is supported by geodetic data documenting dome growth.

In the Arctic, Sea-ice motion and ice export are prominent processes and good indicators of Arctic climate System variability. Sea-ice drift is Simulated using a dynamic–thermodynamic Sea-ice model, validated with retrievals from SsM/I Satellite observations. Both datasets agree well in reproducing the main Arctic drift patterns. In order to Study inner Arctic transports and ice volume anomalies, the Arctic Ocean is Split by ten boundaries, Separating the central Arctic Ocean from the Nordic and marginal Seas. It is found that the already dominant Sea-ice export through Fram Strait has increased at the expense of export through the Barents Sea in the most recent years investigated. Furthermore, ice export from the Eurasian marginal Seas increased Slightly, followed by greater ice production during the winter. In contrast to this, the Sea-ice volume moved within the Beaufort Gyre distinctly decreased. In total, the ice volume in the central Arctic decreased during the 40 year period covered by this Study. The changes in the ice volume correspond to two wind-driven circulation regimes of the Arctic Sea-ice motion, which recur approximately every 11 years. For the volume anomalies we derived a correlation of –0.59 to the North Atlantic Oscillation (NAO) index, lagging the NAO by 2 years.

Envisat Advanced Synthetic Aperture Radar (ASAR) Wide Swath Mode (WSM) images are used to derive C-band HH-polarization normalized radar cross sections (NRCS). These are compared with ice-core analysis and visual ship-based observations of snow and ice properties observed according to the Antarctic Sea Ice Processes and Climate (ASPeCt) protocol during two International Polar Year summer cruises (Oden 2008 and Palmer 2009) in West Antarctica. Thick first-year (TFY) and multi-year (MY) ice were the dominant ice types. the NRCS value ranges between –16.3 ± 1.1 and –7.6 ± 1.0 dB for TFY ice, and is –12.6 ± 1.3 dB for MY ice; for TFY ice, NRCS values increase from –~15 dB to –9 dB from December/January to mid-February. In situ and ASPeCt observations are not, however, detailed enough to interpret the observed NRCS change over time. Co-located Advanced Microwave Scanning Radiometer–Earth Observing System (AMSR-E) vertically polarized 37 GHz brightness temperatures (TB37V), 7 day and 1 day averages as well as the TB37V difference between ascending and descending AMSR-E overpasses suggest the low NRCS values (–15 dB) are associated with snowmelt being still in progress, while the change towards higher NRCS values (–9 dB) is caused by commencement of melt– refreeze cycles after about mid-January.

An analysis is presented of stress and strain measurements made during an investigation of the characteristics of cracks formed in columnar-grain, type S2 fresh-water ice, during uniaxial, compressive loading at the nominal strain rates of 10−3, 10−4 and 10−5s−1, and temperatures of −5°, −10°, −20° and −30°C. The analysis shows that for this range of strain rate and temperature, ice behaves as an anelastic solid. Results are given for the time, grain-size and temperature dependence of the elastic modulus in the plane perpendicular to the long direction of the grains. They are shown to be in reasonable agreement with results of an earlier study of the anelastic behaviour of the same type of ice. It is suggested that the grain-size and temperature dependence of the elastic moduli of ice for this range of strain rate and temperature may be due, in part, to the dependence of the relaxation time on these variables.

The sensitivity of Arctic sea-ice thickness to the optical properties of clouds is investigated. Pollution aerosol has the potential to modify cloud optical properties significantly, which in turn could perturb the radiation balance at the surface of the pack ice. A one-dimensional thermodynamic model of sea ice is employed in this study. Radiative fluxes are parameterized in terms of integrated liquid (ice) water path and the particle effective radius. Results from these calculations show that, for a constant liquid (ice) water path, increasing cloud droplet concentration and the associated reduction in drop size results in a significantly altered surface radiation balance, contributing to an increase in sea-ice thickness. Considerable sensitivity has also been shown of the surface radiation balance to the frequency of occurrence and optical depth of lower tropospheric ice crystals that are present during the cold part of the year.

P-band interferometric synthetic aperture radar (InSAR) data at 5 m resolution from Kahiltna Glacier, the largest glacier in the Alaska Range, Alaska, USA, show pronounced spatial variation in penetration depth, δP. We obtained δP by differencing X- and P-band digital elevation models. δP varied significantly over the glacier, but it was possible to distinguish representative zones. In the accumulation area, δP decreased with decreasing elevation from 18 ± 3 m in the percolation zone to 10 ± 4 m in the wet snow zone. In the central portion of the ablation area, a location free of debris and crevasses, we identified a zone of very high δP (34 ± 4 m) which decreased at lower elevations (23 ± 3 m in bare ice and 5-10m in debris-covered ice). We observe that the spatial configuration of δP is consistent with the expected thermal regime of each zone: δP is high in areas where cold firn/ice likely occurs (i.e. percolation zone and upper ablation area) and low in areas where temperate surface firn/ice likely exists (wet snow zone and lower ablation area). We suggest that the very high δP observed in the upper ablation area is due to the presence of a cold surface layer.

The widespread occurrence of snow-ice formation on the pack ice plays a critical role in the mass balance of Antarctic sea ice. The stable isotope composition, ice texture and salinity of eight ice cores, obtained from the Amundsen Sea during the Oden Southern Ocean 2010/11 expedition from late December 2010 to January 2011, were investigated to illustrate the snow-ice growth process and its contribution to sea-ice development. Most previous research has utilized δ18O as an index tracer to determine the percentages of core length that contain meteoric water, i.e. snow ice. However, this standard practice of snow-ice identification might be biased due to normally low-resolution isotopic measurements and mixing/diffusion processes between the snow ice and underlying ice layers. Snow-ice contributions in these ice cores based instead on an updated isotope mixing model are also presented. Depth profiles of ice texture and salinity are described to serve as representations of the structures of these ice cores. Our isotope mixing model produced an average of 15.9% snow-ice contribution for pack ice in the Amundsen Sea, and meteoric water occupying 40% of snow-ice mass for all ice stations. These results are compared to previous investigations of snow-ice occurrence around Antarctica.

Mini-avalanche systems were constructed both in a low-temperature laboratory and in a snowfield, and the behaviour of the flowing snow was observed in each case. Velocity profiles for the individual snow particles were determined and these implied that a viscous force, which has been neglected in most previous numerical simulations of snow-avalanche motion, needs to be taken into account for many avalanches. Kinematic viscosity coefficients for the fluidized snow were also measured using a modified Stormer-type viscometer. Substituting the dry-friction value and the kinematic viscosity coefficient for fluidized snow into the equation for avalanche motion, numerical simulation of natural events was achieved for the Shiai-dani region. Taking viscous resistance factors into account led to the conclusion that the magnitude of turbulent resistance of snow in avalanche systems is probably much smaller than that represented by the values previously in use.

A two-dimensional particle simulation model of the sea-ice ridging process is developed. In this model, ridges are formed from an intact layer of newly frozen lead ice colliding with a thick multi-year floe. Blocks broken from the leading edge of the lead ice collect above and beneath the multi-year floe to form the characteristic ridge structure seen in the central Arctic. The total energy consumed in ridging ice, which is converted into the potential energy of the ridge structure and dissipated by the frictional and inelastic contacts between blocks of ice, is calculated explicitly. The results of preliminary numerical experiments using this model indicate that the amount of energy required to ridge ice may be much larger than previous estimates.

The preparation of a US Geological Survey Professional Paper, “Satellite image atlas of glaciers”, has produced a 1:5 000 000 scale “Landsat index map of Antarctica”, in which each of the 2 470 Landsat nominal scene centers is represented by a symbol showing the suitability of available Landsat images for the preparation of planimetric image maps and for glaciological studies. Landsat has the potential for imaging about 79% of the area of Antarctica, and 70% of the Landsat imaging area, or about 55% of the continent, was found to have excellent or good (less than 10% cloud cover) coverage.

Australia, Japan, New Zealand, the United Kingdom, and the United States of America have published Landsat image maps, either as single Landsat scenes or as mosaics of two or more images. The Federal Republic of Germany and the Republic of South Africa also plan to publish Landsat image maps in the near future.

Available Landsat images could be used, in combination with Doppler satellite technology for geodetic control, to triple the area of Antarctica presently mapped at scales of 1:250 000 or larger. Landsat-3 RBV images can also be used to prepare 1:100 000 scale image maps.In addition to eventually using Landsat images to compile an accurate coastline of Antarctica, Landsat images have been successfully used for glaciological studies. Recent measurements of successive images of Pine Island Glacier, Walgreen Coast, West Antarctica, showed an average speed of flow of the terminus of 6 m d−1 over 750 d.

An avalanche dynamics model, appropriate for complex terrain, for real avalanche paths was developed by Perla, Cheng and McClung in 1980. The model has two friction terms, one for sliding friction which is independent of speed, and one for turbulent friction which is proportional to V2, where V is the centre-of-mass speed along the incline. By introducing speed maxima for avalanches, along with start and stop reference positions, it is possible to determine the the two constant friction coefficients for the model. When this is done, it is found that speed data often exceed a model speed limit implied by the application of V = 0 at the start and stop positions. This effect is illustrated by analytic solutions of the relevant equations, as well as numerical solutions for actual avalanche paths. Some limitations and properties of the fundamental modelling are outlined and suggestions given for future use of such models.

Satellite images from 1972 to 1997 have been used to prepare a map showing glaciological features of the Saunders Coast area, Antarctica. Analysis of the imagery shows a trend toward ice-front retreat that may be a result of changing environmental conditions.

While the capability of global and regional climate models in reproducing current climate has significantly improved over the past few years, the confidence in model results for remote regions, or those where complex orography is a dominant feature, is still relatively low. This is, in part, linked to the lack of observational data for model verification and intercomparison purposes.

Glacier and permafrost observations are directly related to past and present energy flux patterns at the Earth-atmosphere interface and could be used as a proxy for air temperature and precipitation, particularly of value in remote mountain regions and boreal and Arctic zones where instrumental climate records are sparse or non-existent. It is particularly important to verify climate-model performance in these regions, as this is where most general circulation models (GCMs) predict the greatest changes in air temperatures in a warmer global climate.

Existing datasets from glacier and permafrost monitoring sites in remote and high altitudes are described in this paper; the data could be used in model-verification studies, as a means to improving model performance in these regions.

Recent studies have shown that stratigraphically disturbed meteoric ice bedded at Vostok Station between 3318 and 3539 m dates back to 1.2 Ma BP and possibly beyond. As part of the VOICE (Vostok Oldest Ice Challenge) initiative, a new deviation from parent hole 5G-1 was made at depths of 3270–3291 m in the 2018/19 austral season with the aim of obtaining a replicate core of the old ice. Sidetracking was initiated using the standard KEMS-132 electromechanical drill routinely employed for deep ice coring at Vostok, without significant changes to its initial design. Here we describe the method and operating procedures for replicate coring at a targeted depth in an existing slant hole, involving the use of a cable-suspended electromechanical drill. The design of the milling cutter head used for sidetracking is presented. The performance characteristics and the experience of drilling branch-hole 5G-5 at Vostok are described and discussed.

Snowdrift is one of the many manifestations of two-phase flows in which the inherently stably stratified drift-density profile acts to destroy turbulence. This can be quantified by using an appropriate “particle” Richardson number, equivalent to thermally stratified flow. This Richardson number is proportional to the mean fall velocity of the particles (averaged over the particle-size spectrum) and the drift density and therefore depends strongly on height above the surface. It exhibits a maximum close to the surface, where drift densities are largest. It then decreases to minimum values at intermediate heights, above which Richardson numbers increase with height. The particle Richardson number and the associated decrease in turbulent exchange coefficient depend strongly on wind speed, particle-eddy exchange coefficient and mean particle radius It is found that particle-buoyancy effects in snowdrift are non-negligible for large wind speeds and large particle-eddy exchange coefficients.

Enhancement and classification of digital Landsat data has been carried out for two Canadian glaciers. The objective of the study was to determine the role that such data might play in preparing glacier inventories, It was difficult to measure accurately areas of glaciers and to map moraine-covered ice directly from information derived from digitally classified data. Digital enhancements, however, provide considerable, interpretive detail. Although Landsat imagery is not a substitute for aerial photographs in compiling glacier inventories, grey-tone prints can be used to identify changes rapidly and to provide a base map for recording information.

An analysis of field data for the lower reach of Columbia Glacier, Alaska, U.S.A., indicates that, during the time of the field work, glacier-speed variations in the tidal frequency range are dependent on tidal period variations in sea-level at the terminus, and diurnal period variations in melt-water input at the surface. A simple model based on a perturbation expansion of the flow equation provides a suitable framework in which to understand the observations. Variations in sea- level cause variations in the normal stress at the terminus and are transmitted up the glacier by way of the longitudinal stress. The variations in melt-water input affect glacier speed, presumably through changes in basal water pressure. The data set does not allow a detailed analysis of the relation between melt-water input, basal water pressure, and speed.