A minimal model of a tidewater glacier based solely on mass conservation is compared with two one-dimensional numerical flowline models, one with the calving rate proportional to water depth, and the other with the flotation criterion as a boundary condition at the glacier terminus. The models were run with two simplified bed geometries and two mass-balance formulations. The models simulate the full cycle of length variations and the equilibrium states for a tidewater glacier. This study shows that the branching of the equilibrium states depends significantly on the bed geometry. The similarity between the results of the three models indicates that if there is a submarine undulation at the terminus of a tidewater glacier, any model in which the frontal ice loss is related to the water depth yields qualitatively the same non-linear behaviour. For large glaciers extending into deep water, the flotation model causes unrealistic behaviour.

Satellite altimetric time series allow high-precision monitoring of ice-sheet mass balance. Understanding elevation changes in these regions is important because outlet glaciers along ice-sheet margins are critical in controlling flow of inland ice. Here we discuss a new airborne altimetry dataset collected as part of the ICECAP (International Collaborative Exploration of the Cryosphere by Airborne Profiling) project over East Antarctica. Using the ALAMO (Airborne Laser Altimeter with Mapping Optics) system of a scanning photon-counting lidar combined with a laser altimeter, we extend the 2003–09 surface elevation record of NASA’s ICESat satellite, by determining cross-track slope and thus independently correcting for ICESat’s cross-track pointing errors. In areas of high slope, cross-track errors result in measured elevation change that combines surface slope and the actual Δz/Δt signal. Slope corrections are particularly important in coastal ice streams, which often exhibit both rapidly changing elevations and high surface slopes. As a test case (assuming that surface slopes do not change significantly) we observe a lack of ice dynamic change at Cook Ice Shelf, while significant thinning occurred at Totten and Denman Glaciers during 2003–09.

The experimental evidence for the distortion of a water molecule when it is condensed to form ice is reviewed. The specific distortions considered are the changes in inter-nuclear distances, energy and its derivatives with respect to nuclear motion, and electrical moments and polarizabilities and their response to nuclear motion. Some of the properties of ice can be expanded as Fourier or Taylor series in the ratio r/R of the O–H to the O—O distances, and these expansions are used to relate various properties of the intermolecular potential energy, of the electrical dipole moments, and of the polarizability. For example, the amplitude of the orientation polarization can be related to the infrared intensity of the fundamental and first overtone infrared bands.

We present a newly developed 1-D numerical energy-balance and phase transition supraglacial lake model: GlacierLake. GlacierLake incorporates snowfall, in situ snow and ice melt, incoming water from the surrounding catchment, ice lid formation, basal freeze-up and thermal stratification. Snow cover and temperature are varied to test lake development through winter and the maximum lid thickness is recorded. Average wintertime temperatures of −2 to $-30^{\circ }{\rm C}$ and total snowfall of 0 to 3.45 m lead to a range of the maximum lid thickness from 1.2 to 2.8 m after ${\sim }250$ days, with snow cover exerting the dominant control. An initial ice temperature of $-15^{\circ }{\rm C}$ with simulated advection of cold ice from upstream results in 0.6 m of basal freeze-up. This suggests that lakes with water depths above 1.3 to 3.4 m (dependent on winter snowfall and temperature) upon lid formation will persist through winter. These buried lakes can provide a sizeable water store at the start of the melt season, expedite future lake formation and warm underlying ice even in winter.

Microfossil records from ice archives allow vegetation, fire and land-use activity reconstructions on broad spatial scales. Samples typically contain low microfossil concentrations. Therefore, large ice volumes are often needed for palynology. Hence, it is crucial to extract maximum microfossil numbers through appropriate physical-chemical treatments. We compare six methods covering the main water reduction procedures: evaporation, filtration and centrifugation with snow samples. Adding a known number of Lycopodium marker spores prior to sample treatment and a second marker (Eucalyptus) after laboratory processing allows a quantitative microfossil loss assessment during pollen extraction. We applied the best-performing method (average loss of 22%) to high-alpine firn cores from Colle Gnifetti glacier for validation with a natural archive containing extremely low microfossil concentrations. We conclude that samples processed with different microfossil extraction protocols may give different results for pollen concentrations, percentages and ratios between different pollen types, especially if vesiculate conifer pollen is an important pollen assemblage component. We recommend a new evaporation-based method which delivers the smallest and least variable losses among the tested approaches. Since microfossil losses are inevitable during laboratory procedure, adding markers prior to sample processing is mandatory to achieve reliable microfossil concentration and influx estimates.

We use surface velocity derived from sequential Landsat imagery and a control method to estimate the basal-friction distribution of a major West Antarctic ice stream. The area-averaged basal stress is approximately 1.4 × 104 Pa, or about 29% of the area-averaged driving stress of 4.9 × 104 Pa. Uncertainty of the derived area-averaged basal stress is difficult to assess and depends primarily on spatial variation of the flow-law rate factor in the constitutive law. Spatial variation associated with depth-averaged temperature variation gives an uncertainty of approximately ±103 Pa. Approximately 60% of the ice stream has a basal-stress magnitude less than 104 Pa, and approximately 30% has less than 103 Pa. These characteristics suggest the presence of a mechanically weak, water-charged subglacial till. Small-scale sticky spots where basal friction exceeds the area-averaged driving stress are scattered irregularly across the subglacial regime and comprise approximately 15% of the ice-stream area. Sticky spots cluster in regions where Landsat imagery suggests structural features in the underlying bedrock.

As the continental shelves of the Arctic become important as source areas for the oil and minerals required by human society, sea ice becomes an increasing challenge to engineers. The present paper starts with a consideration of the different fields of engineering which require information on sea ice with the tasks ranging from the design of ice-breaking ships to Arctic drilling platforms and man-made ice islands. Then the structure of sea ice is described as it influences the observed variations in physical properties. Next the status of our knowledge of the physical properties important to engineering is reviewed. Properties discussed include mechanical properties (compressive, tensile, shear and flexural strengths; dynamic and static elastic moduli; Poisson’s ratio), friction and adhesion, thermal properties (specific and latent heats, thermal conductivity and diffusivity, density) and finally electromagnetic properties (dielectric permittivity and loss, resistivity). Particular attention is given to parameters such as temperature, strain-rate, brine volume, and loading direction as they affect property variations. Gaps, contradictions in the data, and inadequacies in testing techniques are pointed out. Finally suggestions are made for future research, especially for more basic laboratory studies designed to provide the data base upon which further theoretical developments as well as field studies can be built.

Passive-microwave 37 GHz vertically polarized (V) brightness temperature (Tb) measurements from the Advanced Microwave Scanning Radiometer for Earth Observing System (AMSR-E) are used to monitor the extent and timing of snowmelt on the Southern Patagonia Icefield (SPI) in Chile and Argentina. Twice daily Tb’s for 2002–08 for high-elevation (>1200 m a.s.l.) pixels exhibit a bimodal histogram, typical of snow-covered regions in Yukon, Alaskan icefields and the Greenland ice sheet. The low count between the two populations represents the Tb threshold for melt (252 K). This Tb value with the ±18 K diurnal amplitude variation threshold quantifies onset and duration of the spring melt–refreeze period and is used to identify melt regimes and seasonal Tb signals. Tb histograms for pixels west of the Andean divide have a normal distribution above the melt threshold. We interpret the Tb histogram as controlled by surface moisture; the shape and position with respect to Tb are retained with changes in both latitude and elevation, and the region is known to have a moist climate. Tb is not driven by seasonal temperature changes in the northwest sector of the icefield because the Tb threshold is exceeded 75% of the time. For all pixels, the spring melt–refreeze period has shortened by a mean of 10 days a−1 and a mean of 16 days a−1 for pixels with bimodal distributions between 2002 and 2008.

Rock debris covers ~30% of glacier ablation areas in the Central Himalaya and modifies the impact of atmospheric conditions on mass balance. The thermal properties of supraglacial debris are diurnally variable but remain poorly constrained for monsoon-influenced glaciers over the timescale of the ablation season. We measured vertical debris profile temperatures at 12 sites on four glaciers in the Everest region with debris thickness ranging from 0.08 to 2.8 m. Typically, the length of the ice ablation season beneath supraglacial debris was 160 days (15 May to 22 October)—a month longer than the monsoon season. Debris temperature gradients were approximately linear (r2 > 0.83), measured as −40°C m–1 where debris was up to 0.1 m thick, −20°C m–1 for debris 0.1–0.5 m thick, and −4°C m–1 for debris greater than 0.5 m thick. Our results demonstrate that the influence of supraglacial debris on the temperature of the underlying ice surface, and therefore melt, is stable at a seasonal timescale and can be estimated from near-surface temperature. These results have the potential to greatly improve the representation of ablation in calculations of debris-covered glacier mass balance and projections of their response to climate change.

Ice-shelf basal melting is the largest contributor to the negative mass balance of the Antarctic ice sheet. However, current implementations of ice/ocean interactions in ice-sheet models disagree with the distribution of sub-shelf melt and freezing rates revealed by recent observational studies. Here we present a novel combination of a continental-scale ice flow model and a calibration technique to derive the spatial distribution of basal melting and freezing rates for the whole Antarctic ice-shelf system. The modelled ice-sheet equilibrium state is evaluated against topographic and velocity observations. Our high-resolution (10-km spacing) simulation predicts an equilibrium ice-shelf basal mass balance of −1648.7 Gt a−1 that increases to −1917.0 Gt a−1 when the observed ice-shelf thinning rates are taken into account. Our estimates reproduce the complexity of the basal mass balance of Antarctic ice shelves, providing a reference for parameterisations of sub-shelf ocean/ice interactions in continental ice-sheet models. We perform a sensitivity analysis to assess the effects of variations in the model set-up, showing that the retrieved estimates of basal melting and freezing rates are largely insensitive to changes in the internal model parameters, but respond strongly to a reduction of model resolution and the uncertainty in the input datasets.

Non-surface mass balance is non-negligible for glaciers in Iceland. Several Icelandic glaciers are in the neo-volcanic zone where a combination of geothermal activity, volcanic eruptions and geothermal heat flux much higher than the global average lead to basal melting close to 150 mm w.e. a−1 for the Mýrdalsjökull ice cap and 75 mm w.e. a−1 for the largest ice cap, Vatnajökull. Energy dissipation in the flow of water and ice is also rather large for the high-precipitation, temperate glaciers of Iceland resulting in internal and basal melting of 20–150 mm w.e. a−1. The total non-surface melting of glaciers in Iceland in 1995–2019 was 45–375 mm w.e. a−1 on average for the main ice caps, and was largest for Mýrdalsjökull, the south side of Vatnajökull and Eyjafjallajökull. Geothermal melting, volcanic eruptions and the energy dissipation in the flow of water and ice, as well as calving, all contribute, and thus these components should be considered in mass-balance studies. For comparison, the average mass balance of glaciers in Iceland since 1995 is −500 to −1500 mm w.e. a−1. The non-surface mass balance corresponds to a total runoff contribution of 2.1 km3 a−1 of water from Iceland.

In recent years, researchers have focused on the applications of uncrewed aerial vehicles (UAVs) in environmental remote sensing tasks. However, studies on glacier monitoring using UAV technology are relatively scarce, especially for high mountain glacier monitoring. To explore the feasibility of UAV technology for high mountain glaciers, four UAV surveys were deployed on two glaciers of the central Tibetan Plateau. Based on the images retrieved by UAV in 2017 and 2019, orthomosaics and digital elevation models were produced to quantify the length, area and elevation changes in the ablation zone of these two glaciers at different times. Additionally, we utilized several Landsat scenes to derive glacier changes over the last 30 years and combined these with the UAV data to assess the advantages and disadvantages of UAV technology in mountain glacier monitoring.

Precipitation downscaling in mountainous regions with sparse station data is challenging, but needed to link global climate datasets with high-resolution glacier models. In this study, we apply a linear orographic precipitation model (OPM) to generate orographic precipitation fields for mass-balance studies at Gran Campo Nevado (GCN), Southern Patagonia. The OPM is driven by large-scale atmospheric input variables taken from the reanalysis data of the US National Centers for Environmental Prediction and the US National Center for Atmospheric Research. The orographic precipitation fields are compared to precipitation fields assessed by a linear precipitation gradient, widely used in earlier mass-balance studies of GCN and elsewhere. Both downscaling methods are implemented into a degree-day model to analyze the sensitivity of mass-balance modeling to different precipitation inputs. Significant spatio-temporal differences are found, particularly in the summit region. The mass-balance modeling shows high sensitivity to the different precipitation distribution methods, leading to differences in the mass-balance gradients on the east side of GCN.

The energy budget of a snow or ice surface is determined by atmospheric variables like solar and atmospheric long-wave radiation, air temperature, and humidity; the transfer of energy from the free atmosphere to the surface depends on the stability of the atmospheric boundary layer, where vertical profiles of wind speed and temperature determine stability, and on surface conditions like surface temperature (and thus surface humidity), roughness, and albedo.

This paper investigates the conditions exactly at the onset or the end of melting using air temperature, humidity, and as the radiation term the sum of global and reflected short-wave plus downward long-wave radiation. For the turbulent exchange in the boundary layer, examples are computed with a transfer coefficient of 18.5 W m−2 K−1 which corresponds to the average over the ablation period on an Alpine glacier. Ways to estimate the transfer coefficient for various degrees of stability are indicated in the Appendix.

It appears from such calculations that snow may melt at air temperatures as low as –10°C and may stay frozen at +10°C.

Numerical model studies describing the dynamics of ice sheets are usually aimed at cold- ice regions of mainland Antarctica. Contrary to these ice bodies with temperatures well below the pressure-melting point at the ice surface, the ice caps on sub-Antarctic islands, such as King George Island, can be considered as polythermal or even temperate. This implies that they may contain nonnegligible amounts of water percolating through the ice matrix. We present three different modifications to a three-dimensional, thermomechanically coupled, higher-order model previously applied to cold-ice regions. We discuss the effect of these modifications on the ice dynamics obtained for diagnostic model runs. The modifications comprise changes to the enhancement factor in Glen’s flow law, the choice of negligible or non-negligible water content and the choice of a threshold altitude below which the ice surface is set to pressure-melting point conditions. All modifications lead to non-linear changes in the resulting horizontal flow velocities. The changes in velocity amplitudes obtained with these modifications compared to simulations without any modification range between 64% and ~400%. This implies that they should be considered in time-dependent simulations of temperate-ice dynamics.

The finite-element method (FEM) is one of the main numerical analysis methods in continuum mechanics and mechanics of solids (Huebner and others, 2001). Through mesh discretization of a given continuous domain into a finite number of sub-domains, or elements, the method finds approximate solutions to sets of simultaneous partial differential equations, which express the behavior of the elements and the entire system. For decades this methodology has played an accelerated role in mechanical engineering, structural analysis and, in particular, snow mechanics. To the best of our knowledge, the application of finite-element analysis in snow mechanics has never been summarized. Therefore, in this correspondence we provide a table with a detailed review of the main FEM studies on snow mechanics performed from 1971 to 2012 (40 papers), for facilitating comparison between different mechanical approaches, outlining numerical recipes and for future reference. We believe that this kind of compact review in a tabulated form will produce a snapshot of the state of the art, and thus become an appropriate, timely and beneficial reference for any relevant follow-up research, including, for example, not only snow avalanche questions, but also modeling of snow microstructure and tire–snow interaction. To that end, this correspondence is organized according to the following structure. Table 1 includes all essential information about previously published FEM studies originally developed to investigate stresses in snow with all corresponding mechanical and numerical parameters. Columns in Table 1 provide references to particular studies, placed in chronological order. Rows correspond to the main model parameters and other details of each considered case.

The partitioning between till deformation and sliding in the fast flow of ice streams with active basal melting is examined assuming no adhesion of the till to the ice base and incompressible viscous fluid behavior for the till. For deforming-till thickness of 10 m or less the predicted contribution to basal motion by sliding is larger than shearing in the till unless there is short-scale roughness with wavelengths less than order 0.1 m on the ice sole. At such short scales strain heating within the till and focused melting on the ice sole would quickly eliminate the roughness. Thus, fast flow over a till bed would be expected to be mostly by sliding over the subglacial till. More realistic continuum behavior of the till including non-linear and compressible deformation strengthens the conclusion. If sliding is not dominant, then there must be adhesion of the till to the ice base, some mechanism that continuously generates short-scale roughness on the ice–till interface, or very weak internal slip boundaries within the till.

Digital terrain models (DTM) are a very important tool for all sorts of glacier studies and serve as a basis for many applications. The latest development is the combination of DTM with digital image-processing techniques which enable a much better visualization of the DTM, and thus a better interpretation of glaciological phenomena.

These new technologies have been applied in an investigation of the Vaughan Lewis Icefall, Juneau Icefield, Alaska. A DTM has been produced by means of photogrammetrie measurements, and a glacier-flow velocity of up to 5.70 m d−1 in the steepest part has been derived. The possibilities for the interpretation of the glacier topography have been significantly improved by using digital image-processing algorithms for the visualization of the DTM.