Debris-covered ice is widespread in mountain regions with debris an important control on surface ice melt and glacier retreat. Quantifying debris cover extent and its evolution through time over large regions remains a challenge. This study develops two Normalized Difference Supraglacial Debris Indices for mapping debris-covered ice based on thermal and near Infrared Landsat 8 bands. They were calibrated with field data. Validation suggests that they have a high level of accuracy. They are then applied to Landsat data for 2016 to produce the first detailed glacier inventory of the Afghanistan Hindu Kush Himalaya that includes debris cover. 3408 glaciers were identified which, for those ⩾0.01 km2 in area, gives an ice cover of 2,222 ± 11 km2 and a debris cover of 619 ± 40 km2. Principal components analysis was used to identify the most influential drivers of debris-covered ice extent. Lower proportions of debris cover were associated with glaciers with a higher elevation range, that were larger, longer and wider. These relations were statistically clearer when the dataset was broken down into climate and geological zones. A glaciers continue to shrink, the proportion of debris cover will become higher, making it more important to map debris cover reliably.

The importance of glacier sliding has motivated a rich literature describing the thermomechanical interactions between ice, liquid water and bed materials. Early recognition of the gradient in melting temperature across small bed obstacles led to focused studies of regelation. An appreciation for the limits on ice deformation rates downstream of larger obstacles highlighted a role for cavitation, which has subsequently gained prominence in descriptions of subglacial drainage. Here, we show that the changes in melting temperature that accompany changes in normal stress along a sliding ice interface near cavities and other macroscopic drainage elements cause appreciable supercooling and basal mass exchange. This provides the basis of a novel formation mechanism for widely observed laminated debris-rich basal ice layers.

This paper describes fine-resolution measurements of glacier surface strain rates very close to the margin of Russell Glacier, West Greenland. Measurements at a small scale make possible detailed analysis of strain patterns close to the glacier margin, and suggest that strain rates vary over small areas. The strain pattern is determined by ice flexure over subglacial obstacles as well as by seasonally variable marginal retardation and by the orientation of the ice margin relative to the flow direction.

Surface and core samples of Neh–nar Glacier in the Kashmir Valley have been analysed for the radionuclides 32Si. 210Pb, 40K, and 137Cs. The lateral and vertical profiles (at an altitude of about 4 140 m) reveal:

(1)32Si activity decreasing slowly from the accumulation zone to 4 050 m altitude and then abruptly towards the snout.

(2)Five zones of alternating high and low 210Pb activity in the surface samples.

(3)An horizon at between 2 and 3 m depth containing 210Pb activity above natural levels. This horizon is also associated with 137Cs and a maximum in total ß activity.

The ice samples have been dated on the basis of a simplified two–component model, the “fresh“contribution determined by 2l0Pb and the old component by 32Si. The following conclusions can be drawn from these observations:

(1)The model age of the snout ice is c. 850 years.

(2)The average rate of ice movement in the lower glacier is about 2 m/year, which compares well with the annual movement rate of 2.65 m/year observed since 1974.

Rifts are full-thickness fractures that propagate laterally across an ice shelf. They cause ice-shelf weakening and calving of tabular icebergs, and control the initial size of calved icebergs. Here, we present a joint inverse and forward computational modeling framework to capture rifting by combining the vertically integrated momentum balance and anisotropic continuum damage mechanics formulations. We incorporate rift–flank boundary processes to investigate how the rift path is influenced by the pressure on rift–flank walls from seawater, contact between flanks, and ice mélange that may also transmit stress between flanks. To illustrate the viability of the framework, we simulate the final 2 years of rift propagation associated with the calving of tabular iceberg A68 in 2017. We find that the rift path can change with varying ice mélange conditions and the extent of contact between rift flanks. Combinations of parameters associated with slower rift widening rates yield simulated rift paths that best match observations. Our modeling framework lays the foundation for robust simulation of rifting and tabular calving processes, which can enable future studies on ice-sheet–climate interactions, and the effects of ice-shelf buttressing on land ice flow.

Borehole inclinometers are standard equipment for field glaciologists and are commonly used for investigating the flow law of ice and for measuring the spatial position of englacial and sub-surface sensors. The recent development, at the University of British Columbia (UBC), of a prototype inclinometer that employs a three-component fluxgate magentometer to obtain a compass bearing has stimulated our interest in borehole inclinometry. Following a review of various approaches to glacier inclinometry, we present a unified theory of data interpretation that can be applied to all inclinometers, discuss the application of the theory to the UBC inclinometer, and discuss the sensitivity of the theory to error in the data.

From 2017 to 2020, three significant calving events took place on Pine Island Glacier, West Antarctica. Ice-shelf velocities changed over this period and the calving events have been suggested as possible drivers. However, satellite observations also show significant changes in the areal extent of fracture zones, especially in the marginal areas responsible for providing lateral support to the ice shelf. Here, we conduct a model study to identify and quantify drivers of recent ice-flow changes of the Pine Island Ice Shelf. In agreement with recent studies, we find that the calving events caused significant velocity changes over the ice shelf. However, calving alone cannot explain observed velocity changes. Changes in the structural rigidity, i.e. ice damage, further significantly impacted ice flow. We suggest that ice damage evolution of the ice-shelf margins may have influenced recent calving events, and these two processes are linked.

Compaction experiments on porous samples of granular ice and ice/rock mixtures were conducted at low temperature, primarily to obtain rheological data useful in modeling the internal structure and evolution of icy satellites of the giant planets. The data may also be of interest for studying Earth’s glaciers and the Martian polar caps.

The samples tested were prepared from three types of ice: water, carbon dioxide and ammonia; three types of rock components were also used in the samples. The time-dependent compaction of samples a few centimeters in size was studied for a range of rock contents, pressures (2.2–17.7 MPa) and temperatures (140–261 K). An Equation (16), giving the compaction rate as a function of porosity, pressure, temperature and concentration of the rock component was fitted to the observed results. The presence of rock fragments strongly inhibits the compaction process.

Mean annual air temperatures and precipitation on the Greenland Ice Sheet, as estimated from snow profile studies and long-term meteorological records at coastal stations, have been used to prepare mean annual air temperature and mean annual precipitation charts for the Greenland Ice Sheet. It is shown that melting of surface snow may occur at elevations of about 1,300 m. in north Greenland and up to 2,700 m. in south Greenland. The warming trend in the Arctic, as indicated by increases in mean annual air temperature, may have occurred to a lesser extent on the ice sheet than at sea-level coastal stations. Annual accumulation of precipitation is two or three times as great at 2,700 m. on the west side of the ice sheet as at the crest. South of lat. 66° N., precipitation may be about twice as great on the east side of the crest as on the west side.

Despite their importance for regional water resource planning and as indicators of climate change, records of in situ glacier mass balance remain short and spatially sparse in the Himalaya. Here, we present an updated series of in situ mass-balance measurements from Rikha Samba Glacier, Nepal, between 2011 and 2021. The updated in situ mass balance is −0.39 ± 0.32 m w.e. for this period. We use an energy-mass balance model to extend the annual mass-balance series back to 1974. The model is forced using daily meteorological variables from ERA5-Land reanalysis data that is linearly bias-corrected using observations from an automatic weather station situated near the glacier terminus. The modeled mass balance is consistent with the in situ mass-balance series measured 2011–2021 and with previous glaciological and geodetic estimates. The model results indicate a mass balance of −0.56 ± 0.27 m w.e. a−1 over the reconstruction period of 1974–2021, which is comparable to the mass losses experienced by other Himalayan glaciers during this time. An assessment of the sensitivity of the glacier mass balance to meteorological forcing suggests that a change in temperature of ±1 K has a stronger effect on the calculated mass balance compared to a ±20% change in either precipitation, or relative humidity, or solar radiation.

This paper contains a critical survey of the literature on the bearing capacity of floating ice plates. It consists of a discussion of general questions, a critical survey of analytical attempts to determine the bearing capacity of floating ice plates and a survey of field and laboratory tests on floating ice plates and their relation to the analytical results. It concludes with a systematic summary of the results, a discussion of observed shortcomings, and suggestions for needed investigations.

This report is of a preliminary nature; detailed analyses are being carried on at the present time. The tunnel project on a small cirque glacier in the Jotunheim area of Norway, made possible observations of englacial movements in August and December of 1951 which are correlated with surface movements. Emphasis was placed on detailed three-dimensional studies. A marked divergence of flow lines was noted in both the vertical and horizontal planes. Bands previously thought to be thrust planes were found to be of sedimentary origin and not to be discrete planes of shear. Rates of contractions of tunnel sections up to a depth of 50 m. were observed and the englacial temperature distributions were taken in both zones of ablation and accumulation.

Due to the abnormally warm summers of 1955 and 1956 the glaciers of Mount Ruapehu deteriorated to such an extent that the ash layer of the eruption of 1945 was exposed everywhere. This caused a development of ice cones similar to those occurring in Iceland. Various factors, especially heavy crevassing, which took place at the same time, are responsible for the different ways of development of dirt cones on Ruapehu.

We use a global coupled ocean-sea ice model to test the hypothesis that the disintegration of the West Antarctic ice sheet (WAIS), or just its ice shelves, may modify ocean circulation and sea-ice conditions in the Southern Ocean. We compare the results of three model runs: (1) a control run with a standard (modern) configuration of landmask in West Antarctica, (2) a no-shelves run with West Antarctic ice shelves removed and (3) a no-WAIS run. In the latter two runs, up to a few million square kilometres of new sea surface area opens to sea-ice formation, causing the volume and extent of Antarctic sea-ice cover to increase compared with the control run. In general, near-surface waters are cooler around Antarctica in the no-shelves and no-WAIS model runs than in the control run, while warm intermediate and deep waters penetrate further south, increasing poleward heat transport. Varying regional responses to the imposed changes in landmask configuration are determined by the fact that Antarctic polynyas and fast ice develop in different parts of the model domain in each run. Model results suggest that changes in the extent of WAIS may modify oceanographic conditions in the Southern Ocean.

The cutting force components and the cutting moment on the cutting tool were measured during the orthogonal machining of ice with cutting tools inclined at negative rake angles. The variables included the cutting depth (< 1 mm), the cutting speed (0.01 ms−1 to 1 ms−1), and the rake angles (–15° to –60°). Results of the experiments showed that the cutting force components were approximately independent of cutting speed. The resultant cutting force on the tool was in a direction approximately normal to the cutting face of the tool. The magnitude of the resultant force increased with the negative rake angle. Photographs of ice-chip formation revealed continuous and segmented chips at different cutting depths.

The elastic stresses have been determined, in a single-layer homogeneous snowpack on a realistic avalanche slope, by a two-dimensional finite-element analysis. Calculation of the state of stress throughout the 0.96 m snow layer on a slope approximately that of the Lift Gully at Berthoud Pass, Colorado, resulted in reasonable stress values. In particular, both field experience and the calculated shear stresses predict avalanching in the lower-density snows. Also, tensile stresses were present only in the area of the observed fracture line.

Modes of formation and rates of collapse have been determined for kame terraces and a fan delta in the Adams Inlet area, Alaska. The hummocky and trenched surface of the kame terrace develops by mass-wasting processes caused by differential melting of buried ice. The dry channels in the collapsed part of the terrace are formed by melt water during stagnant-ice bursts. Measurements over a period of 17 years indicate that terrace back-wasting averages 4.3 m a−1. The fan delta is forming near sea-level by streams that derive part of their load from the kame terrace. The fan delta seaward of the retreating kame terrace is undergoing partial collapse to produce kettles ringed by concentric fractures. Vegetation, now as much as 5 m below high tide, suggests a fan-delta collapse rate of about 0.5 m a−1.

Bottom melting rates have been calculated for a large number of sites on George VI Ice Shelf from measurements of its kinematic behaviour. No simple explanation for the melt-rate pattern was found in terms of ice-shelf parameters, assuming steady-state conditions. Values of apparent melt rates varied from 1 to 8 m a−1 of ice. Along different flow lines the melt rate would sometimes increase with distance from the grounding line and sometimes the melt rate would decrease with distance. Large melt rates were found both where ice flowed off Palmer Land and where the ice shelf butted against Alexander Island. Although oceanographic conditions probably control bottom melting rates the complex pattern with large spatial variation seems to indicate that some areas of ice shelf are changing in thickness.

This paper examines the basal ice sequence of Rhone Glacier, a cold-based glacier in the McMurdo Dry Valleys, Antarctica, using isotopic and solute chemistry data. Three different ice facies are identified: englacial, amber and stratified. The englacial facies is clean, bubbly ice of meteoric origin and is underlain by an amber facies. Amber ice is a characteristic of cold alpine glaciers in the McMurdo Dry Valleys and is distinctive for its high solute concentrations and much higher strain rates compared with the overlying englacial ice and the underlying stratified ice. Analysis of the stratified facies reveals an isotopic signature indicative of melt then refreeze processes and it is most likely associated with apron entrainment at the margin. By contrast, the amber facies has a co-isotopic slope of 8 and plots on a meteoric waterline. The inclusion of impurities in the amber ice reveals prolonged contact with the bed, and its depleted isotopic signature is consistent with ice formed during a cooler period. Comparison of the basal sequence of Rhone Glacier with other cold-based glaciers in the McMurdo Dry Valleys reveals strong similarities between valley-side glaciers (e.g. Meserve and Rhone Glaciers), whereas valley-floor glacier basal sequences (e.g. Suess Glacier) are characterized by structurally complex amalgamations of ice and debris.

Measurements have been made on Austerdalsbreen, Norway, to test the theory that wave ogives at the foot of an ice fall are formed by pressure. The pattern of deformation over the first three waves from the Odinsbre ice fall was studied by measuring the absolute and relative motions of 35 stakes during August 1956. There are large variations of longitudinal compression through the wave pattern, but no simple correlation exists between the compression and the crests; nor are the crests consistently rising with respect to the average surface. We conclude that the waves are not forming by pressure in this area. A detailed quantitative explanation of the observed pattern of deformation is found by improving the existing theory of glacier flow. The deformations taking place are explained as essentially independent of the presence of the waves; they are primarily due (a) to the compression that must occur in the ice as its slope decreases and it becomes thicker, and (b) to the bending and unbending to which the ice is subjected as it passes over a bed of changing curvature. Additional contributions to the deformation arise from the widening of the glacier channel, which is important at the immediate foot of the ice fall, and from the annual ablation.

The theory explains quantitatively the rotation and bending of the tunnel excavated in 1955; it was also used to make a prediction, which was successfully verified in a further experiment on the glacier in July and August 1957.

A pressure mechanism of wave formation can be reconciled with the observations if it is supposed that the compression in the lower two-thirds of the ice fall, which was measured photogrammetrically in August 1956, varies significantly with the seasons. However, the positions and amplitudes of the observed waves are fully accounted for by the combined plastic deformation and ablation mechanism recently described in another paper. There is therefore no longer any need for the pressure hypothesis as a primary cause of the waves.