Net changes in glacier area in the region 50–51˚ N, 116–125˚W, which includes the Columbia and Rocky Mountains (1951/52–2001) and the Coast Mountains (1964/65–2002), were determined through a comparison of historic aerial photography and contemporary Landsat 7 ETM+ imagery. The volumes of individual glaciers were estimated using an empirical volume–area scaling relationship. The area of glaciers in the Coast Mountains decreased by 120±10km2, or 5%of the initial ice-covered area here. The areas of glaciers in the Columbia and Rocky Mountains decreased by 20 and 6km2 respectively, corresponding to relative changes in total area of –5% and –15%. The estimated total ice volume loss from the whole region was 13 ±3 km3. In all parts of the study area, the relative changes in area of individual glaciers showed considerable variability, while the smallest glaciers remained essentially unchanged. This suggests that local factors unique to individual glaciers largely determine their sensitivity to climatic change, and that the very small glaciers are collectively less sensitive to such change.

Indian rivers originating in the Himalaya depend on seasonal snow-cover melt during crucial summer months. The seasonal snow cover was monitored using Advanced Wide Field Sensor (AWiFS) data of the Indian Remote Sensing Satellite (IRS) and using the Normalized Difference Snow Index (NDSI) algorithm. The investigation was carried out for a period of 3 years (2004/05, 2005/06 and 2006/07) between October and June. A total of 28 sub-basins of the Ganga and Indus river basins were monitored at intervals of 5 or 10 days. Approximately 1500 AWiFS scenes were analyzed. A combination of area–altitude distribution and snow map was used to estimate the distribution of snow cover in altitude zones for the individual basins and for the western and central Himalaya. Hypsographic curve and snow-free area was used to estimate monthly snow-line elevation. The lowest snow-line altitude in the winters of 2004/05, 2005/06 and 2006/07 was observed at 2480 ma.s.l. on 25 February 2005. In Ravi basin for the year 2004/05, snow accumulation and ablation were continuous processes throughout the winter. Even in the middle of winter, the snow area was reduced from 90% to 55%. Similar trends were observed for 2005/06 and 2007/08. In Bhaga basin, snowmelt was observed in the early part of the winter, i.e. in December, and no significant melting was observed between January and April.

A simple quasi one-dimensional model of flowing avalanches is presented. It is a further development of that used in the Swiss Guidelines for practitioners. It is shown that shearing in avalanche movement is concentrated near the ground and that, due to the geometrical roughness of the ground, a flow resistance proportional to the square of velocity must be taken into account in addition to dry friction. For the change of flow on changing slope angles it is demonstrated that under certain conditions for internal friction a “normal” flow on a flat lower part can no longer be attained; the avalanche behaves like a rigid body. The runout distance is in fair agreement with the Guidelines if a larger internal friction is used. The main differences lie in much smaller deposition depths and smaller velocities during runout.

The impact of spatial and temporal variations in the surface albedo and aerodynamic roughness length on the surface energy balance of Haut Glacier d’Arolla, Switzerland, was examined using a semi-distributed surface energy-balance model (Arnold and others, 1996). The model was updated to incorporate the glacier-wide effects of albedo and aerodynamic roughness-length variations using parameterizations following Brock (1997). After the model’s performance was validated, the glacier-wide patterns of the net shortwave, turbulent and melt energy fluxes were examined on four days, representative of surface conditions in late May, June July and August. In the model, meteorological conditions were held constant on each day in order that the impact of albedo and aerodynamic roughness-length variations could be assessed independently. A late-summer snowfall event was also simulated. Albedo and aerodynamic roughness-length variations, particularly those associated with the migration of the transient snowline and the decay of the winter snowpack, were found to exert a strong influence on the magnitude of the surface energy fluxes The importance of meteorological conditions in suppressing the surface energy fluxes and melt rate following a fresh snowfall was highlighted

In this paper, we explore geomorphological evidence allowing a first- order reconstruction of the extent and pattern of frozen-bed conditions under the last Fennoscandian ice sheet. We mapped relict landscapes, i.e. glacial landforms and subaerially developed ground surfaces predating the last ice sheet and marking sustained frozen- bed conditions, at four different spatial scales. At the ice-sheet scale, relict landscapes are most abundant between the Last Glacial Maximum ice divide and the elevation axis of the Scandinavian mountain range. The location of frozen-bed zones was mainly a function of dispersal centre location (low surface temperatures and small strain heating) and small ice thickness over the eastern flank of the mountain range. At the mesoscale (260 × 360 km map area), the pattern of relict surfaces is governed by inward-cutting ice-stream erosion.Topographical control was weak, but relation to flow pattern was strong, with the major frozen-bed zone located where ice flow was strongly divergent. At the regional scale (40 × 65 km map area) in hilly terrain, topographical control was strong with relict surfaces only appearing above a plane dipping in the up-ice direction. At the local scale (12 × 14 km map area), control by topography was likewise strong, but the detailed boundary pattern was irregular, with specific landforms occurring both up- and down-ice of frozen patches.

This paper presents an assessment of biological activity associated with ice surface debris (cryoconite) at the ice-sheet scale. Estimates of the mass distribution of cryoconite over the Greenland ice sheet (GIS) and the biological activity associated with it are presented and then coupled with a surface mass-balance model to estimate total carbon fluxes due to respiration and photosynthesis. We find an average loading of 66gm−2 at Kangerlussuaq, southwest Greenland, which compares well with recent estimates from Kronprins Christians Land (17–440 gm−2: Bøggild and others, 2010) in northeast Greenland. We also report a significant microbial biomass in cryoconite at both these places (103–104 cells mg−1) and carbon fluxes of the order of 1–3 μM C g−1d−1 for both respiration and photosynthesis. The modelling indicates that total respiration and photosynthesis fluxes are likely to be ∼101–102 GgCa−1 and thus far from trivial. However, estimation of the net ecosystem impact across the entire ice sheet on atmospheric CO2 concentrations is problematic because photosynthesis rates were almost certainly low during our field campaign. Therefore, like its water balance, the carbon balance of the GIS is now known to be important, but its accurate quantification will remain elusive until more data are forthcoming.

Two spectral snow-reflectance models that account for the effects of grain-size and liquid-water fraction are described and initial validation results presented. The models are based upon the spectral complex refractive index of liquid water and ice in the region from 400 to 2500 nm. Mie scattering calculations are used to specify the essential optical properties of snow in the models. Two approaches are explored to model the effect of liquid water in the snow. The first accounts for the liquid water as separate spheres interspersed with ice spheres in the snow layer. The second accounts for the liquid water as coatings on ice grains in the snow layer. A discrete-ordinate radiative transfer code is used to model the spectral reflectance of the snow for the Mie-calculated optical properties. Both the interspersed- and coated-sphere models show that the snow-absorption feature at 1030 nm shifts to shorter wavelength as the liquid-water content increased. The expression of these shifts is different for the two models. A comparison of the models with a spectral measurement of frozen and melting snow shows better agreement with the coated-sphere model. A spectral fitting algorithm was developed and tested with the coated-sphere model to derive the grain-size and liquid-water fraction from snow spectral reflectance measurements. Consistent values of grain-size and liquid water were retrieved from the measured snow spectra. This research demonstrates the use of spectral models and spectral measurements to derive surface snow grain-size and liquid-water fraction. The results of this research may be extended to regional and greater scales using data acquired by airborne and spaceborne imaging spectrometers for contributions to energy balance and hydrological modeling.

Between austral late winter 1993 and austral autumn 1998, during five cruises aboard the research vessel Nathaniel B. Palmer, almost 300 m of core was obtained from first-year ice floes in the Ross, Amundsen and Bellingshausen Seas. Analysis of the texture, stratigraphy and stable-isotopic composition of the ice was used to assess the magnitude of the role of flooding and snow-ice formation at the base of the snowpack in the thickening of the ice cover and the thinning of the snow cover. Snow ice occurred in all ice-thickness categories and made a significant contribution to the total ice mass (12−36%) in both autumn and winter. Although the amount of snow ice was often exceeded by the amount of frazil ice and congelation ice, the thickness of individual layers of each ice type indicated that snow ice often made a greater contribution to the thermodynamic thickening of the ice cover than the other ice types. The larger quantities of frazil ice and congelation ice were primarily the result of dynamic thickening. Flooding and snow-ice formation reduced the snow cover to 42−70% of the total snow accumulation depending on time and location. On the basis of this information, ship-based snow-depth estimates were adjusted to estimate the total snow accumulation on different ice-thickness categories.

Two- and three-dimensional avalanche dynamics models are being increasingly used in hazard-mitigation studies. These models can provide improved and more accurate results for hazard mapping than the simple one-dimensional models presently used in practice. However, two- and three-dimensional models generate an extensive amount of output data, making the interpretation of simulation results more difficult. To perform a simulation in three-dimensional terrain, numerical models require a digital elevation model, specification of avalanche release areas (spatial extent and volume), selection of solution methods, finding an adequate calculation resolution and, finally, the choice of friction parameters. In this paper, the importance and difficulty of correctly setting up and analysing the results of a numerical avalanche dynamics simulation is discussed. We apply the two-dimensional simulation program RAMMS to the 1968 extreme avalanche event In den Arelen. We show the effect of model input variations on simulation results and the dangers and complexities in their interpretation.

We present a series of benchmark experiments designed for testing and comparing numerical ice-sheet models. Following the outcome of two EISMINT workshops organized to intercompare large-scale ice-sheet models currently in operation, model benchmark experiments ate described for ice sheets under fixed and moving margin conditions. These address both steady-state and time-dependent behaviour under schematic boundary conditions and with prescribed physics. A comparison was made of each model’s prediction of basic geophysical variables such as ice thickness, velocity and temperature. Consensus achieved in the model inter-comparison provides reference solutions against which the accuracy and consistency of ice-sheet modelling codes can be assessed.

Air temperatures at the Marambio (MAR), Esperanza (ESP) and Matienzo (MAT) stations have been analyzed to investigate recent climate change on the eastern part of the Antarctic Peninsula. They are compared with data from the Oreadas station on the South Orkney Islands, the longest record available in Antarctica, and from the Faraday (FAR) station on the western coast of the Peninsula. Though the interannual variability is comparatively high and the stations are located in different climatic regimes, a pronounced warming trend shows up in all records. At MAR a temperature increase of 1.5°C has been observed since the beginning of the record in 1971. This is of similar magnitude to the increase at FAR on the west coast, which was 2.5°C for the longer period since 1945. The steady retreat and collapse of the northern Larsen Ice Shelf (LIS) coincided with this warming trend. of particular importance for the ice-shelf mass balance in this region are the summer temperatures which show a statistically significant warming trend at MAR and ESP. The representativity of the summer temperatures of MAR for northern LIS is confirmed by intercomparison with the parallel measurements at MAT which is located on the ice shelf.

The Tibetan Plateau interior area (TPIA), often termed the Qangtang Plateau, is distinguished by many dome-like mountains higher than 6000 ma.s.l. These mountains provide favourable conditions for the development of ice caps and glaciers of extreme continental/subpolar type. According to historical topographic maps (1959–80) and recent Landsat images (2004–11), continuous retreat was observed and the glacierized part of this area decreased by 9.5% (0.27% a–1) with respect to the total glacier area of 8036.4 km2 in the 1970s. Glaciers in the Zhari Namco basin have experienced the highest area shrinkage, with a reduction rate of 0.72% a–1, while the smallest reduction occurred in Bangong Co (0.12% a–1) and Dogai Coying basins (0.11% a–1). A regional gradient of area loss was found, with a larger decrease in the south and a smaller decrease in the north of the plateau. Comparisons indicate glaciers have experienced smaller shrinkage in the TPIA than in surrounding regions. Glacier shrinkage in the TPIA is mainly attributed to an increase in air temperature, while precipitation, glacier size and positive difference of glaciation also played an important role.

An improved understanding of fresh water stored in the Himalaya is crucial for water resource management in South Asia and can be inferred from glacier mass-balance estimates. However, field investigations in the rugged Himalaya are limited to a few individual glaciers and short duration. Therefore, we have recently developed an approach that combines satellite-derived snowlines, a temperature-index melt model and the accumulation-area ratio method to estimate annual mass balance of glaciers at basin scale and for a long period. In this investigation, the mass balance of 146 glaciers in the Chandra basin, western Himalaya, is estimated from 1984 to 2012. We estimate the trend in equilibrium line altitude of the basin as +113 m decade−1 and the mean mass balance as −0.61 ± 0.46 m w.e. a−1. Our basin-wide mass-balance estimates are in agreement with the geodetic method during 1999–2012. Sensitivity analysis suggests that a 20% increase in precipitation can offset changes in mass balance for a 1 °C temperature rise. A water loss of 18% of the total basin volume is estimated, and 67% for small and low-altitude glaciers during 1984–2012, indicating a looming water scarcity crisis for villages in this valley.

The majority of glaciers in central Chile have receded in recent decades, from >50m to only a few meters per year, mainly in response to an increase in the 0˚C isotherm altitude. The Aconcagua river basin (33˚ S) is one of the major glaciated basins in central Chile, with 121 km2 of ice in 2003. An earlier inventory using 1955 aerial photographs yielded a total surface area of 151 km2, implying a reduction in glacier area of 20% (0.63km2 a–1) over the 48 years. Photographic stereo models, high-resolution satellite images (Landsat, ASTER) and SRTM data have been used to delineate glacier basins. A focus on Glaciar Juncal Norte, one of the largest glaciers in the basin, allows a more detailed analysis of changes. The glacier has exhibited a smaller reduction (14%) between 1955 and 2006, and the resulting elevation changes over this smaller period are not significant. The above reduction rates are lower than in other glaciers of central Chile and Argentina. This trend emphasizes water runoff availability in a river where most of the water in the dry summers is generated by glaciers and snowpack, and where most of the superficial water rights are already allocated. Ongoing hydrological research including modelling of future water runoff will improve our understanding.

Flow stripes along the surface of rapidly moving ice streams are shown to be an expected reaction of a viscous medium flowing over an irregular bed, whenever the velocity at the bed is large compared to shearing through the thickness. The principal features of the process are as follows. At high basal speeds the ice acts as a strongly selective band-pass filter transmitting basal undulations on spatial scales of a few ice thicknesses very effectively to the surface. The decay of the short-scale features by diffusion is strongly retarded by horizontal stress gradients. Consequently, localized disturbances at the bed produce topographic effects on the surface that are advected long distances downstream before decaying away. This mechanism may explain many of the flow stripes on active ice streams moving by rapid basal motion.

There has been a marked decline in the summer extent of Arctic sea ice over the past few decades. Data from autonomous ice mass-balance buoys can enhance our understanding of this decline. These buoys monitor changes in snow deposition and ablation, ice growth, and ice surface and bottom melt. Results from the summer of 2008 showed considerable large-scale spatial variability in the amount of surface and bottom melt. Small amounts of melting were observed north of Greenland, while melting in the southern Beaufort Sea was quite large. Comparison of net solar heat input to the ice and heat required for surface ablation showed only modest correlation. However, there was a strong correlation between solar heat input to the ocean and bottom melting. As the ice concentration in the Beaufort Sea region decreased, there was an increase in solar heat to the ocean and an increase in bottom melting.

Different types of fast ice flow (both spatial and temporal) in valley glaciers (surging glaciers, tidewater glaciers and deforming-bed glaciers) and ice sheets (ice streams and deforming-bed ice-sheet flow) are discussed briefly. Although there are unlikely to be any specific individual landforms associated with fast ice flow, there may be landform assemblages.

At valley glacier scale, it is suggested that there are two landform assemblages: (1) an ice-thrust type, dominated by bulldozed push moraines and hummocky moraines (associated with glaciers with a high supraglacial sediment supply, a coarse-grained substrate and a coarse-grained proglacial sediment wedge); and (2) a bed-flow type dominated by “squeeze” push moraines, flutes and drumlins (associated with glaciers with a low supra- glacial sediment supply and fine-grained substrate). The ice-thrust type alone is only associated with discontinuous fast flow (on both rigid and deforming beds); whilst the bed-flow type is associated with both continuous and discontinuous fast flow.

It is suggested that these two landform assemblages may also be indicative of fast ice flow at ice-sheet scale, in particular the bed-flow style. If that is the case, then discontinuous fast ice flow may be indicated by the ice-thrust landform assemblage and the bed-flow style where drumlins are present.

It is also suggested that specific evidence for ice streams includes the distinctive land-form assemblages within valley or fan-like locations, and a predictable pattern of velocity reflected by drumlin elongation ratios.

River ice plays a fundamental role in biological, chemical and physical processes that control freshwater regimes of the cold regions. Moreover, it can have enormous economic implications for river-based developments. All such activities and processes can be modified significantly by any changes to river-ice thickness, composition or event timing and severity. This paper briefly reviews some of the major hydraulic, mechanical and thermodynamic processes controlling river-ice events and how these are influenced by variations in climate. A regional and temporal synthesis is also made of the observed historical trends in river-ice break-up/freeze-up occurrence from the Eurasian and North American cold regions. This involves assessment of several hydroclimatic variables that have influenced past trends and variability in river-ice break-up/freeze-up dates including air-temperature indicators (e.g. seasonal temperature, 0˚C isotherm dates and various degree-days) and large-scale atmospheric circulation patterns or teleconnections. Implications of future climate change on the timing and severity of river-ice events are presented and discussed in relation to the historical trends. Attention is drawn to the increasing trends towards the occurrence of mid-winter break-up events that can produce especially severe flood conditions but prove to be the most difficult type of event to model and predict.

Radar profiles of bed echo intensity can survey conditions at the ice–bed interface and test for the presence or absence of water. However, extracting information about basal conditions from bed echo intensities requires an estimate of the attenuation loss through the ice. We used the relationship between bed echo intensities from constant-offset radar data and ice thickness to estimate depth-averaged attenuation rates at several locations on and near Kamb Ice Stream (KIS), West Antarctica. We found values varying from 29 dBkm–1 at Siple Dome to 15 dBkm–1 in the main trunk region of KIS, in agreement with a previous measurement and models. Using these attenuation-rate values, we calculated the relative bed reflectivity throughout our KIS surveys and found that most of the bed in the trunk has high basal reflectivities, similar to those obtained in the location of boreholes that found water at the bed. Areas of lower bed reflectivity are limited to the sticky spot, where a borehole found a dry bed, and along the margins of KIS. These results support previous hypotheses that the basal conditions at locations like the sticky spot on KIS control its stagnation and possible reactivation.

Local observations of snow layers are used as the basis for spatial extrapolation of snow properties and for establishing a time record of snow deposition, yet significant lateral variations in layer thickness, density and microstructure are well documented. Here we examine the nature of layer heterogeneity over distances of 10– 100 000 m using data from primarily flat locations in Alaska, Antarctica and Greenland. We find that at a scale of 10 m or less, perennial snow layers on glaciers and ice sheets are more uniform and laterally continuous than seasonal layers, which, in addition to heterogeneity introduced by wind and water percolation, are also affected by local topography and vegetation. At a scale of about 100 m, heterogeneity of seasonal and perennial snow layers converges and approaches a peak value. At larger scales (103–105m), local (order 100 m) forcing continues to produce most of the layer heterogeneity, with synoptic-scale variations adding small amounts. Cross-correlation at these larger scales is based on recognizing distinctive layer sequences or matching a few key layers of snow. Many layers cannot be correlated because they pinch out or change at scales (i.e. 100 m) smaller than the spacing between snow pits.