From data taken on the British Trans-Arctic Expedition it is calculated that 9% of the Arctic Ocean surface between the North Pole and Spitsbergen was hummocked or ridged ice, 17% was unridged ice less than a year old, 73% was unridged old ice and 0.6% was ice-free. The mode of 250 thickness measurements taken through level areas of old floes along the entire traverse lies between 2.25 and 2.75 m. The mean end-of-winter thickness of the ice is calculated to be 4.6 m in the Pacific Gyral and 3.9 m in the Trans-Polar Drift Stream. From measurements of the percentage coverage and thickness of the various ice forms, it is calculated that the total annual ice accumulation in the Arctic Ocean is equivalent to a continuous layer of ice 1.1 m thick. 47% of this accumulation occurs in ice-free areas and under ice less than 1 year old. 20% of the total ice production is either directly or indirectly related to ridging or hummocking. An ice-ablation rate of 500 kg m−2 measured on a level area of a multi-year floe is compared with the rate on deformed and ponded ice. Greatest melting occurs on new hummocks and least on old smooth hummocks. The annual balance of ice older than 1 year but younger than multi-year ice is calculated from a knowledge of ice-drift patterns and the percentage coverage of first-year ice. The same calculations give a mean-maximum drift period of 5 years for ice in the Trans-Polar Drift Stream and 16 years in the Pacific Gyral. It is calculated that for the period February 1968 to May 1969 the annual ice export was 5 580 km3.

An extensive system of mirabilite (Na2SO4 · 10H2O) beds has been mapped on the Ross Ice Shelf near Black Island. The salt beds are normally underlain by a thin layer of mud and their surface is covered by a non-marine algal mat and boulder lag. These authors suggest the salt has been formed by the displacement of sub-ice-shelf brines to the ice-shelf surface. Evidence also suggests that other terrestrial mirabilite beds in the McMurdo Sound area were formed in the same manner and deposited by the Ross Ice Shelf during its Wisconsin retreat from McMurdo Sound. Mirabilite salt in the dry valleys, southern Victoria Land, may have also originated from melt waters which dissolved ice-shelf mirabilite beds.

Ice shelves, which regulate ice flow from the Antarctic ice sheet towards the ocean, are shaped by spatiotemporal patterns of surface accumulation, surface/basal melt and ice dynamics. Therefore, an ice dynamic and accumulation history are imprinted in the internal ice stratigraphy, which can be imaged by radar in the form of internal reflection horizons (IRHs). Here, IRHs were derived from radar data combined across radar platforms (airborne and ground-based) in coastal eastern Dronning Maud Land (East Antarctica), comprising three ice rises and adjacent two ice shelves. To facilitate interpretation of dominant spatiotemporal patterns of processes shaping the local IRH geometry, traced IRHs are classified into three different types (laterally continuous, discontinuous or absent/IRH-free). Near-surface laterally continuous IRHs reveal local accumulation patterns, reflecting the mean easterly wind direction, and correlate with surface slopes. Areas of current and past increased ice flow and internal deformation are marked by discontinuous or IRH-free zones, and can inform about paleo ice-stream dynamics. The established IRH datasets extend continent-wide mapping efforts of IRHs to an important and climatically sensitive ice marginal region of Antarctica and are ready for integration into ice-flow models to improve predictions of Antarctic ice drainage.

A study of 30 slab avalanches at Whistler Mountain ski area, British Columbia, indicates that slab instability initiates with highest frequency on 40° slopes, that the temperature at the slab bed surface is about –5°C averaged for the 30 cases, and that on the average the slabs have a snow density of about 220 kg/m3. These results agree well with results from earlier studies. A rich variety of crystals appear in photomicrographs of samples extracted from the bed surfaces of the 30 slabs. In many cases, crystals extracted from the plane of critical weakness do not differ markedly from crystals extracted from adjacent strata.

We use a mathematical model to investigate the effect of basal topography and ice surface slope on transport and deposition of sediment within a water-filled subglacial channel. In our model, three zones of different behaviour occur. In the zone furthest upstream, variations in basal topography lead to sediment deposition under a wide range of conditions. In this first zone, even very small and gradually varying basal undulations (~5 m amplitude) can lead to the deposition of sediment within a modelled channel. Deposition is concentrated on the downstream gradient of subglacial ridges, and on the upstream gradient of subglacial troughs. The thickness and steepness of the ice sheet has a substantial impact on deposition rates, with shallow ice profiles strongly promoting both the magnitude and extent of sediment deposition. In a second zone, all sediment is transported downstream. Finally, a third zone close to the ice margin is characterised by high rates of sediment deposition. The existence of these zones has implications for esker formation and the dynamics of the subglacial environment.

A variation in the α−β model which is a regression model that allows a deterministic prediction of the extreme runout to be expected in a given path, was applied for calculating avalanche runout in the Catalan Pyrenees. Present knowledge of major avalanche activity in this region and current mapping tools were used. The model was derived using a dataset of 97 ‘extreme’ avalanches that occurred from the end of 19th century to the beginning of 21st century. A multiple linear regression model was obtained using three independent variables: inclination of the avalanche path, horizontal length and area of the starting zone, with a good fit of the function (R2 = 0.81). A larger starting zone increases the runout and a larger length of the path reduces the runout. The new updated equation predicts avalanche runout for a return period of ~100 years. To study which terrain variables explain the extreme values of the avalanche dataset, a comparative analysis of variables that influence a longer or shorter runout was performed. The most extreme avalanches were treated. The size of the avalanche path and the aspect of the starting zone showed certain association between avalanches with longer or shorter runouts.

The last five years have seen an increasing interest in clathrate ices as a result of the discovery of extensive deposits of natural gas hydrates in permafrost regions. Twenty-six new clathrate hydrates have been identified, mainly by NMR, including a tetragonal hydrate of dimethyl ether. N-butane and neopentane have been found to be enclathrated in natural gas hydrates, the former as a gauche conformer. As a result of their high symmetries, encaged neopentane, CF4, SF6, and SeF6 exhibit a Resing apparent-phase-change effect in the temperature range of NMR line narrowing. There is increasing evidence that reorientational jumps of water molecules are more frequent than translational jumps in clathrate ices. This is certainly so for ethylene oxide-d4 and tetrahydrofuran-d8 hydrates for which two regions of proton line narrowing and two T1ρ minima have been observed. The reorientational motions of most guest molecules in structure II hydrates only become isotropic on a time scale long enough to permit the cage configurations to be averaged to 43m symmetry by reorientation of the water molecules. The orientations of the water molecules remain disordered to the lowest temperatures.

The first extensive and far-reaching investigations of the Sino-German Joint Expedition to the Ch’ing-hai–Hsi-tsang (Qinghai–Xizang) Plateau in the glacierized region of the Amne Machin (Anyemaqen) started work in the area and compiled the glacial inventory in that region. In the past 15 years scientists have found that the majority of glaciers in the Amne Machin (Anyemaqen) have been advancing whereas most glaciers in Ch’i-lien Shan (Qilian Shan), adjacent to Amne Machin (Anyemaqen), have been retreating during the same period. This is a problem worthy of study by glaciologists. Through investigation and analysis, it is also found that Ha-lung (Halong) glacier has the character of a surging glacier. The author tentatively forecasts the next surge of Ha-lung (Halong) glacier and the tendency of variations of glaciers in Ch’i-lien Shan (Qilian Shan) in the near future.

Dielectric experiments have been undertaken at temperatures between −2° and −70° C in the frequency range 10Hz to 100 kHz on 14 firn and ice samples retrieved from the Antarctic Peninsula. This investigation shows that the dielectric behaviour of polar samples from the Antarctic Peninsula is very similar to that of polar firn and ice from Greenland and from elsewhere in Antarctica. In contrast, temperate samples from the Antarctic Peninsula have relaxation times up to ten times shorter for a given temperature between –20° and –70°C, and have higher values of high-frequency conductivity than those of polar samples. Consequently, the thermal regime (temperate or polar) can be distinguished by the dielectric behaviour of the samples.

High-frequency conductivities of polycrystalline samples from the Antarctic Peninsula match the trends of published conductivity data for HF- and HCl-doped laboratory ice; higher conductivities are associated with coastal sites where greater concentrations of marine ions occur in snow.

Annealing polar firn above −10°C results in elevated conductivities across all frequencies measured and shortened relaxation times. Thus, samples for dielectric analysis should not be warmed to above –10°C for risk of irreversibly altering their dielectric behaviour.

Air temperature inversions, a situation in which atmospheric temperature increases with height, are key components of the Arctic planetary boundary layer. The present study investigates the spatial and temporal variations of temperature inversions over different surface types (rock, gravel, snow, ice) along the Mittivakkat valley (southeast Greenland). For this purpose, 113 vertical profiles with high spatio-temporal resolution of air temperature and relative humidity were collected with unoccupied aerial vehicles (UAVs) during a 13-day field campaign in summer 2019. Air temperature inversions were present in 83% of the profiles, of which 24% were surface-based inversions and 76% were elevated inversions. The proglacial area covered with bare rock and gravel induces surface heating and convection during the day and, through interaction with local circulation patterns, leads to the frequent formation of elevated inversions. In contrast, the glacier surface itself acts as a persistent cooling surface and leads to the formation of surface-based inversions. A low-level fog layer that forms under the inversion layer may be causing non-linear vertical ablation gradients on Mittivakkat Gletsjer. Furthermore, we demonstrate that atmospheric measurements using UAVs can better capture small-scale processes than other products like radiosonde or modeled reanalysis data.

Processes driving changes in sea-ice seasonality and sea-ice thickness were explored for a ‘warm-shelf’ region along the West Antarctic Peninsula using vertically coupled sea-ice-ocean thermodynamic simulations, with and without assimilated satellite sea-ice observations and moored ocean temperature observations. Simulations with assimilated sea-ice observations permitted investigation of surface [thermodynamic and dynamic (e.g., wind-driven)] processes affecting sea-ice thickness and seasonality. Assimilation of quasi-weekly variability in the depth and temperature of the deep warm pycnocline permitted examination of subsurface processes affecting sea-ice. Simulations using assimilated sea-ice observations (and implied motion) always produced greater surface heat fluxes and overall thinner sea ice. Assimilating seasonal and quasi-weekly variability in the depth and temperature of the pycnocline modified the start of the sea-ice season by −23 to +1 d, and also modified the sea ice thickness/seasonality to be thinner/shorter or thicker/longer at sub-seasonal and seasonal timescales, highlighting a mechanism where a shoaling pycnocline enhanced upward deep-water heat fluxes as transient surface-induced turbulence had a greater effect on a reduced mixed layer volume. The observed interplay of surface, subsurface, and sea-ice modulation of ocean-atmosphere heat transfer underscores the importance of representing the interaction between sea-ice concentration and upper ocean variability in climate projections.

Two–dimensional hydrodynamic equations for laminar, viscous flow, and admitting a frictional slip-plane lower boundary are applied to the modeling of snow-avalanche impact on rigid wall structures. Predicted maximum pressures and pressures versus time are compared with published experimental results, and general correspondence is established. Impact pressure versus time is found to depend upon the shape of the avalanche leading edge, for which general information is lacking. Computer modeling of more complex structural configurations is feasible using the methodology reported.

Observations and measurements were made of high-speed avalanches at Shiai-dani, the Kurobe canyon, to reveal their real features and properties, using strain-gauge-type load cells in measuring impact force and speed. A maximum impact pressure of 140 - 104 N m-2 was obtained, as well as data indicating the existence of a number of wave fronts, ranging in speed from 9 to 60 m s -1 inside an avalanche. Violent changes in atmospheric pressure ranging from -21 to +5 mbar were observed near its path when a high-speed avalanche passed by.

A procedure is described for testing cored ice specimens under uniaxial tension. The procedure incorporates an end-capping system described by Cole and others (1985), two carpeted Synthane end caps, and extensometers mounted directly on the ice. Use of the procedure has resulted in a successful test rate of 75%

Using a global climate model coupled with an ocean and a sea-ice model, we compare the effects of doubling CO2 and halving CO2 on sea-ice cover and connections with the atmosphere and ocean. An overall warming in the 2 × CO2 experiment causes reduction of sea-ice extent by 15%, with maximum decrease in summer and autumn, consistent with observed seasonal sea-ice changes. The intensification of the Northern Hemisphere circulation is reflected in the positive phase of the Arctic Oscillation (AO), associated with higher-than-normal surface pressure south of about 50° N and lower-than-normal surface pressure over the high northern latitudes. Strengthening the polar cell causes enhancement of westerlies around the Arctic perimeter during winter. Cooling, in the 0.5 × CO2 experiment, leads to thicker and more extensive sea ice. In the Southern Hemisphere, the increase in ice-covered area (28%) dominates the ice-thickness increase (5%) due to open ocean to the north. In the Northern Hemisphere, sea-ice cover increases by only 8% due to the enclosed land/sea configuration, but sea ice becomes much thicker (108%). Substantial weakening of the polar cell due to increase in sea-level pressure over polar latitudes leads to a negative trend of the winter AO index. The model reproduces large year-to-year variability under both cooling and warming conditions.

Experimental procedure and measured estimates of the tensile strength of snow are given by a new method utilizing large sample sizes of naturally deposited snow. Data are presented as a function of average sample density, temperature, loading rate, and snow type. The results show less scatter in the data than previous in-situ estimates and lower mean strength values as a function of density. The relevance of the data to tensile fracture as observed in slab avalanche release is discussed.

Observations were carried out on each significant layer of the snow cover at Ottawa (lat. 45° 24′ N., long. 75° 43′ W.) on the thickness of the layer, and the density, grain size distribution and degree of bonding of the snow in each layer. A logarithmic dependence on time was found for the layer thickness, and the density and grain size distribution. The product of layer thickness times the corresponding snow density was found to be constant when no melting occurred.

This paper presents a preliminary account of the glaciological observations made by the Antarctic Expedition of the U.S.S.R. Academy of Sciences in Kaiser Wilhelm II Land, Queen Mary Land and Knox Coast in 1956. The topography of the edge of the ice sheet is described, and the ice regime is discussed, particularly in relation to the existence of ice-free areas such as “Bunger’s oasis”.

As polar ice descends from the free surface to depth in a large ice sheet, it undergoes deformations which give rise to the formation and subsequent evolution of a fabric and associated anisotropy. In this paper two orthotropic models of such strain-induced anisotropy are considered. Model A is based on analysis of the microscopic behaviour of an individual ice crystal with transversely isotropic response and assumed uniform stress in a polycrystal. The macroscopic response of the ice aggregate is then derived by applying the concept of an orientation distribution function, and the resulting viscous law relates the strain rate to the stress and three structure tensors. In model B it is assumed that the macroscopic response of ice is determined by the fabric induced entirely by macroscopic deformations, and all microprocesses taking place at the grain level are ignored. A constitutive relation is derived from a general frame-indifferent law for orthotropic materials, and expresses the stress in terms of the strain rate, strain and throe structure tensors. The two models are applied to determine the viscous response of ice to continued uniaxial compression and simple shearing in order to compare the predictions of both theories.