Windpumping has been identified as a process that could potentially enhance sublimation of surface snow at high forcing frequency and spawn air movement deeper in firn at lower frequencies. We performed an experiment to examine the relationship between high-frequency wind and pressure measurements within the top meter of an alpine snowpack and compared experimental results with two theoretical predictions. We find that both theoretical predictions underestimate high-frequency perturbation pressure attenuation with depth in the near-surface snowpack and the discrepancy between theory and measurement increases with perturbation pressure frequency. The impact of this result for near-surface snow is that potential enhanced sublimation will occur over a shallower snow depth than these two theories predict. Correspondingly, interstitial air mixing at depth in firn will be driven by lower frequencies than these two theories predict. While direct measurement of these energy-rich lower frequencies is beyond the scope of this paper, stationary pressure measurements validate the presence of a pressure field that could drive near-surface circulation.

This study examines the performance of low-cost, low-power GNSS positioning systems for glacier monitoring in high-latitude environments. We compare the positioning performance of co-located low-cost u-blox ZED-F9P GNSS units (a few hundred USDs) and survey-grade Trimble R10 units (> $10,000 USD) under stationary (on land) and dynamic (on glacier) conditions near Terra Nova Bay, Antarctica. Low-cost and survey-grade systems yield almost identical error magnitudes under short (3 m), medium (34 km) and long (390 km) baseline kinematic-positioning scenarios. We further examined the efficacy of low-cost GNSS for glaciological applications by installing four u-blox and two Trimble receivers on Priestley Glacier to observe tide-modulated ice flexure. All receivers successfully detected subtle tidal oscillations with amplitudes < 3 cm, consistent with the predicted phasing from a tide model. These experiments offer a strong rationale for the widespread use of low-cost receivers to expand and densify GNSS monitoring networks, both in Antarctica and in glaciated regions worldwide.

Englacial water transport is an integral part of the glacial hydrologic system, yet the geometry of englacial structures remains largely unknown. In this study, we explore the excitation of fluid resonance by small amplitude waves as a probe of englacial geometry. We model a hydraulic network consisting of one or more tabular cracks that intersect a cylindrical conduit, subject to oscillatory wave motion initiated at the water surface. Resulting resonant frequencies and quality factors are diagnostic of fluid properties and geometry of the englacial system. For a single crack–conduit system, the fundamental mode involves gravity-driven fluid sloshing between the conduit and the crack, at frequencies between 0.02 and 10 Hz for typical glacial parameters. Higher frequency modes include dispersive Krauklis waves generated within the crack and tube waves in the conduit. But we find that crack lengths are often well constrained by fundamental mode frequency and damping rate alone for settings that include alpine glaciers and ice sheets. Branching crack geometry and dip, ice thickness and source excitation function help define limits of crack detectability for this mode. In general, we suggest that identification of eigenmodes associated with wave motion in time series data may provide a pathway toward inferring englacial hydrologic structures.

The effects of notch acuity (crack-tip sharpness) on the fracture toughness of S2 ice were investigated using six groups of single-edge-notched-bend (SENB) specimens with different crack (or notch) root radii fabricated by six different methods. The mean value and standard deviations of the apparent fracture-toughness values KQ of the specimens with blunt notches were significantly higher than those of the specimens with sharp cracks. The results presented in a plot of fracture toughness versus , where p is the crack-tip radius, provide an estimate of the required notch acuity for fracture-toughness testing. The microstructural features in the immediate vicinity of the crack tip and the crack-tip geometry govern the magnitude of the apparent fracture toughness of the ice. The crack-tip-opening-displacement (CTOD) measured in this study indicates the existence of microplastic deformation in the vicinity of the crack tip at the initiation of unstable fracture.

To assess the amount of ice volume stored in glaciers or ice caps, a method to estimate ice thickness distribution is required for glaciers where no direct observations are available. In this study, we use an existing inverse method to estimate the bedrock topography and ice thickness of the Renland Ice Cap, East Greenland, using satellite-based observations of the surface topography. The inverse approach involves a procedure in which an ice dynamical model is used to build-up an ice cap in steady state with climate forcing from a regional climate model, and the bedrock is iteratively adjusted until the modelled and observed surface topography match. We validate our model results against information from airborne radar data and satellite observed surface velocity, and we find that the inferred ice thickness and thereby the stored total volume of the ice cap is sensitive to the assumed ice softness and basal slipperiness. The best basal model parameters for the Renland Ice Cap are determined and the best estimated total ice volume of 384 km3 is found. The Renland Ice Cap is particularly interesting because of its location at a high elevation plateau and hence assumed low sensitivity to climate change.

The first part of the paper is devoted to a historical review of applied glaciology problems in the French Alps since the last century (cog railway to the top of Mont Blanc, construction of mountain huts, preventive emptying of sub glacial water pockets under Tete Rousse glacier, etc.). The second part is devoted to the study of modern projects concerned with construction of cableway stations or cableway pylons on or near the glaciers, with the preparation of ski runs on glaciers during summer, with the different problems met during works to capture subglacial torrents for the needs of hydroelectric companies.

We perform Bayesian inference of the parameters of a time-dependent model of ice flow and calving at Helheim Glacier, East Greenland. We find that, while a time-independent calving parameterization can recover the mean observed terminus position, such a model is unable to recover sub-annual variability, even when forced with seasonally varying climate. To address this, we develop a simple stochastic model relating surface runoff rates and calving threshold. Again inferring model parameters from observations, we find that this parameterization is able to reproduce observations with respect to both mean position and characteristic temporal variability. This result demonstrates the importance of considering potential sub-annual controls on calving rates in numerical models, which may include variable undercutting rates or surface runoff-dependent surface crevasse propagation.

Detailed field mapping in three massifs of the central Andes of Peru indicates that there are four glacial moraine stages. Historical evidence and correlation with Patagonia and South Georgia suggest that the three youngest stages relate to Neoglacial re-advances which culminated before 4000 b.p., between a.d. 1750 and 1800 and during the late nineteenth century. The oldest moraine stage may be of late Wisconsin/Weichselian age. The absence of older moraines suggests that the Peruvian Andes were not high enough earlier in the Pleistocene to support larger glaciers.

It is argued that in temperate mountain glaciers, waterways are subglacial. It is shown that the theory of Spring and Hutter (1981) for intraglacial flooded conduits leads to an equation for the grade line which differs from Röthlisberger’s (1972) only by negligible terms, and a slight modification of the exponent of the discharge. For a subglacial flooded waterway two important processes should instead be introduced: the enhancement of plastic deformation on the up-stream side of bumps, and the heat afforded by ground water (which in winter accounts for most of the discharge). The theory modified in this way explains why Röthlisberger had to adopt an unrealistic value for the rheological parameter of ice. It leads to the conclusion that in areas which are not overdeepened, most of the year subglacial waterways should remain not flooded and at atmospheric pressure. The case of overdeepening is examined. Finally the implications of this new model for glacier sliding theory are demonstrated.

Shipboard observations (in accordance with Norsk Polar-Institutt guidelines) from 6 years of Australian National Antarctic Research Expeditions (ANARE) voyages have provided data giving a detailed knowledge of iceberg sizes and concentrations in the Southern Ocean between long. 60° and 140° E. The resulting size–frequency distributions are examined in conjunction with a knowledge of water movement along known drift tracks in a selected study area (between lat. 59° and 64° S., and long. 90° and 120° E.) to determine iceberg-dissolution rates. The “median life” (before breaking) of icebergs less than 1000 m in horizontal dimension is estimated to be 0.2 a, which is significantly lower than was previously thought. The mean melt rate is estimated to be 0.12 m d–1, which agrees broadly with previous laboratory studies. The relative contributions of melt, calving, and breakage, plus the enhancement effect of roll-over, are examined in estimating the natural dissolution rate. Breakage appears to be the dominant mechanism for larger icebergs with melt and calving able to explain the disappearance of icebergs in the smallest categories only (within the mean “median-life” period). Examination of the historical records of Captain Cook indicates that iceberg concentrations, as well as the northerly extent in this region 200 years ago, were compatible with the present data.

Isotropic points are structurally stable features of any complicated field of stress or strain-rate, and therefore will almost always be present on the surface of a glacier. A given isotropic point for strain-rate will belong to one of six different classes, depending on the pattern (lemon, star, or monstar) of principal directions and the contours (ellipses or hyperbolas) of constant principal strain-rate values in its neighbourhood. The central isotropic point on a glacier should theoretically have a monstar pattern, but the contours around it may sometimes be elliptic and sometimes hyperbolic. Nearby, but not coincident with it there will be an isotropic point for stress. This will also have a monstar pattern but, in contrast to the strain-rate point, the contours around it must be hyperbolic. Published examples are consistent with these conclusions. In addition to isotropic points for strain-rate a glacier surface will contain isolated points of pure shear; these also can be classified into six different types. Stable features of this kind give information about the essential structure of a tensor field and form useful points of comparison between observation and numerical simulation.

Measuring surface mass-balance in the accumulation areas of glaciers is challenging because of the high spatial variability of snow accumulation and the difficulty of conducting annual field glaciological measurements. Here, we propose a method that can solve both these problems for many locations. Ground-penetrating radar measurements and firn cores extracted from a site in the French Alps were first used to reconstruct the topography of a buried end-of-summer snow horizon from a past year. Using these data and surface elevation observations from LiDAR and Global Navigation Satellite System instruments, we calculated the submergence velocities over the period between the buried horizon and more recent surface elevation observations. The differences between the changes in surface elevation and the submergence velocities were then used to calculate the annual surface mass-balances with an accuracy of ±0.34 m w.e. Assuming that the submergence velocities remain stable over several years, the surface mass-balance can be reconstructed for subsequent years from the differences in surface elevation alone. As opposed to the glaciological method that requires substantial fieldwork year after year to provide only point observations, this method, once submergence velocities have been calculated, requires only remote-sensing data to provide spatially distributed annual mass-balances in accumulation areas.

The Barnes Ice Cap on Baffin Island, N.W.T., Canada, was investigated during the summer of 1950. This ice cap, some 6000 sq. km. in extent, appears to have an approximately balanced budget, and yet there is no firn on its surface. It is postulated that its nourishment is by superimposed ice due to immediate refreezing of much of the melt water of summer. It is further inferred that a similar process nourishes many Arctic glaciers and ice caps where elevation, precipitation and temperature are all low. The name “Baffin Type” is proposed for these in the classification of glaciers.

The erosion rate of bedrock by glacier action is analyzed under conditions of constant-state radial convergent and divergent flow, assuming that the quarrying rate increases with increasing sliding velocity, and assuming a conventional power-function sliding law. Ice is modeled as a non-linear Glen material. Deviatoric stresses are computed but are shown to be negligible compared to the basal shear stress, provided that suitable restraints are placed on the ratio of channel radius of curvature to ice thickness. If the ice is sufficiently thick, radial divergent flow results in erosion rates which decrease in the down-stream direction This provides an explanation for the formation of the largest class of fjord thresholds which occur at channel widenings. In contrast, increased erosion rates are predicted at narrows which can explain the presence of deep troughs at gradual narrows. It is argued that the presence of pronounced thresholds in abrupt narrows can be explained by low quarryability or locally high roughness which reduces the sliding velocity. The origin of till overlying thresholds is explained as a natural consequence of a threshold being a position of relative stability for the terminus of a retreating tide-water glacier.