A new continuum approach to snowdrift modelling is introduced. In addition, numerical studies are carried out to identify the influence of time-varying wind conditions on snowdrift simulations. We compare the snowdrift patterns at Grimming mountain, Austria, derived using a time-averaged wind field and a time-varying wind field obtained from the numerical weather prediction model INCA. The results show significant differences in the deposition patterns and snow depth even after a 6 hour drift period. Using time-averaged boundary conditions leads to an underprediction of the resulting snow depth caused by averaging the wind speed, which lets gusts of wind disappear while snow transport is a non-linear function of the wind speed. Using numerical weather prediction models for snowdrift simulation therefore provides enhanced knowledge of the snow depth for local avalanche warning services.

Our ultimate objective is to study the mass-balance variations of Polar Ural glaciers during the last millennium. We use mass-balance data for two glaciers between 1957 and 1981, climate data obtained by instrumental observations during the 20th century, and tree-ring data compiled for the last 1000 years. Because there is a high correlation between measured glacier mass-balance and climate variables, we reconstruct glacier mass balance for the 20th century using regression equations. Similarly, we use regression equations relating measured climatic variables to tree-ring widths to reconstruct glacier mass balance for the last millennium. According to our reconstructions, the most extensive period of negative mass balance occurred in the late 10th/early 11th century AD, which corresponds to the Medieval Warm Period. A prolonged period of positive glacier mass balance began after the mid-11th century, a time commonly accepted as the onset of the Little Ice Age. This cooling period has three maxima, the last from the early 17th to mid-19th century. Until the beginning of the 20th century, cumulative mass balance over the last millennium varied between ±8mw.e. However, glacier mass balance in the second half of the 20th century is lower than it has been for the past millennium, and cumulative mass balance is now -10mw.e. Polar Ural glaciers are important indicators of regional climate change and should be incorporated into a worldwide glacier-monitoring programme.

Glacierized basins in the high Arctic are believed to be regions of low chemical weathering rates, despite the lack of pertinent data, because it is believed that water does not flow in significant quantities through subglacial drainage systems. We have calculated chemical weathering rates at Finsterwalderbreen, a polythermal, surge-type glacier in Svalbard. Rates of 320 and 150 meq Σ+ m−1 year−1 were measured in 1994 and 1995, respectively. The corresponding water fluxes were 4.1 × 107 and 1.7 × 107 m3. We estimate that we have measured ~72% of the total annual discharge, hence the true annual chemical weathering rates are ~440 and 210 meq Σ+ m−2 year−1, respectively This gives a mean annual chemical weathering rate of 330 meq Σ+ m−2 year−1, which approximates the continental average of 390 meq Σ+ m−2 year−1 and is intermediate between chemical weathering rates measured on cold-based glaciers (~110–160 meq Σ+ m−2 year−1) and temperate glaciers (450–1000 meq Σ+ m−2 year−1). This suggests that there may be a direct link between chemical weathering rates and thermal regime, and that glacierized basins in the high Arctic cannot necessarily be considered as regions of low chemical weathering and CO2 drawdown.

Modeling microwave back-scattering and emission from snow-packs requires the knowledge of snowpack characteristics and their dynamics to select an appropriate model. Both theory and field data show that microwave back-scattering coefficients and brightness temperatures are sensitive to parameters describing snow-microstructure. Stereological methods and other techniques can be applied to images of sections cut from undisturbed snow, and are used to obtain accurate and unbiased estimates of snow-microstructure parameters for discrete scatterer modeling. Assuming that the ice particle-size distribution can be characterized as a log-normal distribution function, we show that the parameters describing the distribution can be obtained from section images. The results show that, in addition to snow density and ice-particle size, the particle-size variation has great effect on dry-snow extinction properties. The optically equivalent ice-particle size for Rayleigh scattering in a snowpack with grain-size variations can be determined from the stereological measurements from snow sections.

The recent topography of Kamchatka was formed by the joint activity of endogenic and exogenic processes among which glacial erosion and sedimentation played the most important role. Glacial erosion is exhibited to different degrees on old and young mountains. Corrie and corrie-valley glaciers are common to the oldest and strongly eroded early Pleistocene volcanoes. The flanks of Holocene volcanoes are only s1ightly affected by exogenic processes. As a result, ice caps and ice belts as well as crater glaciers are developed on them.

During earlier glaciations, the influence of volcanism on glaciers and frozen strata caused the specific conditions for sub-ice eruptions, as a result of which strata of welded tuffs and pumices, and thick strata of fragmented material were formed. Recent and older glaciers in regions of active volcanism are covered by large amounts of pyroclastic material. During intense melting of glacier ice in these regions, thick fields of morainic deposits were formed. Similar conditions are found in Iceland, as describeo by (Thorarinsson 1958, Thorarinsson 1974), among others.

Glaciological data collected at Patriot Hills, Antarctica (80°18'S, 81°22'W), are used to assess the local mass balance of the ice sheet. The data were collected during two field campaigns conducted by the Instituto Antartico Chileno in January and November 1995. Measurements included surveying of stakes, and ice thickness derived from discrete radar soundings with a ground-based high-frequency impulse system.

Ablation occurred on the bare-ice field at the base of Patriot Hills, with a maximum value of 7g cm −2a−1. Net accumulation was detected away from the mountains, over the firn-covered area of the glacier, with a maximum rate of 10 g cm 2 a−1 Ice thickens rapidly away from the mountains, reaching a thickness of 383 m, the maximum range of the radar system, near the center of the blue-ice field. No significant difference in surface elevation of the ice was detected over the 305 d period, which indicates that the ice is in near-equilibrium at Patriot Hills.

The inland advance of supraglacial lakes (SGLs) towards the interior regions of the Greenland ice sheet (GrIS) may have implications for the water volumes reaching the subglacial drainage system, and could consequently affect long-term ice-sheet dynamics. Here, we investigate changes to the areas, volumes and elevation distributions of over 8000 manually delineated SGLs using 44 Landsat images of a 6200 km2 sector of north-west Greenland over three decades (1985–2016). Our results show that SGLs have advanced to higher maximum (+418 m) and mean (+299 m) elevations, and that there has been a near-doubling of total regional SGL areas and volumes over the study period, accelerating after 2000. These changes were primarily caused by an increased SGL area and volume at high (≥1200 m a.s.l.) elevations, where SGL coverage increased by over 2750% during the study period. Many of the observed changes, particularly the post-2000 accelerations, were driven by changes to regional surface-temperature anomalies. This study demonstrates the past and accelerating response of the GrIS's hydrological system due to climatic warming, indicating an urgent need to understand whether the increasingly inland SGLs will be capable of hydrofracture in the future, thus determining their potential implications for ice-sheet dynamics.

The investigation of spatial and temporal variability of the snow cover in northern Eurasia (snow depth, density, thermal characteristics, water equivalent) includes large-scale fieldwork, modelling and analysis of meteorological data of two winters (2004/05 and 2005/06) from 38 weather stations situated in different climatic conditions and physico-geographical zones. Common regularities and features of snow-cover variability are revealed for these winters, despite their contrasting temperature and precipitation regimes and differences from an average winter, as the time of appearance, duration and depth of snow cover, the number of snowfalls and date of melting. The modelling of snow-cover stratigraphy is based on viscous compression and recrystallization laws. Meteorological information (temperature, wind velocity and precipitation) is used as input for the model. The output is the specific snow-cover stratigraphy according to positioning in different physical–geographical regions and due to the possible variation as determined by winter temperature and precipitation regimes. The peculiarity of snow-cover stratigraphy at the regional scale depends on the meteorological conditions of its formation as well as on the character of landscapes. A satisfactory correlation of the modelled typical columns of the snow cover formed in 2004/05 and 2005/06 in different regions of Russia and of real columns is revealed.

The ice cover of the Nianchu river basin, southern Tibetan Plateau, was mapped for 2005, using a SPOT5 scene, and for 1990 and 2000 from Landsat TM/ETM. Digital elevation models (DEMs) were generated from 1 : 50 000 scale topographical maps. The results show that in 2005 there were 136 glaciers in this basin, with a total area of 224 km2. Of these, 37 glaciers had an area >1 km2 and 10 were larger than 5 km2; the average snout altitude was 5608m a.s.l. A comparison of outlines from the last 15 years shows that most glaciers have decreased in size; none have advanced. From 1990 to 2005, Xiaquepu glacier No. 56 and Shimozongpu glacier No. 38 retreated 310 and 560 m, respectively. The mean reduction in glacier surface area was 5% (10 a)–1 while the area of glacial lakes expanded by 10%; nine new lakes formed in this basin over the 15 year period. Because air temperatures here have been increasing, while precipitation has remained steady, glacier retreat is considered to be related to rising temperature.

Detailed studies of the last 20 km of the flow-line leading to the core hole at Dye 3 Greenland, provide a description of ice flow over and around basal hills. The surface pattern is very simple. Velocity vectors are nearly parallel to one another and the largest variations in velocity are speed changes along the direction of flow. The surface elevation is stepped and the speed is faster than average where the surface slope is steepest. These positions correspond to basal highs, and the surface velocity increases as expected, based on the decrease in ice thickness, which indicates that most of the ice thickness must vary in velocity as does surface ice. Further support for this comes from the form of an internal radio-reflecting layer, which, in general, has the same shape as the bed but with much reduced relief. The damping of the relief is the same both along and across the flowline, suggesting that lateral velocity fluctuations are not important and that flow around and between obstacles is not well developed at the surface or at depth. At two sites, however, the internal layer does not match the bed and at one of these there must be important third-dimensional flow at depth.

We describe elongate, wet, subglacial bedforms in the shear margins of the NE Greenland Ice Stream and place some constraints on their formation. Lateral shear margin moraines have been observed across the previously glaciated landscape, but little is known about the ice-flow conditions necessary to form these bedforms. Here we describe in situ sediment bedforms under the NE Greenland Ice Stream shear margins that are observed in active-source seismic and ground-penetrating radar surveys. We find bedforms in the shear margins that are ~500 m wide, ~50 m tall, and elongated nearly parallel to ice-flow, including what we believe to be the first subglacial observation of a shear margin moraine. Acoustic impedance analysis of the bedforms shows that they are composed of unconsolidated, deformable, water-saturated till. We use these geophysical observations to place constraints on the possible formation mechanism of these subglacial features.

The RADARSAT geophysical processor system (RGPS) produces measurements of ice motion and estimates of ice thickness using repeat synthetic aperture radar maps of the Arctic Ocean. From the RGPS products, we compute the net deformation and advection of the winter ice cover using the motion observations, and the seasonal ice area and volume production using the estimates of ice thickness. The results from the winters of 1996/97 and 1997/98 are compared. The second winter is of particular interest because it coincides with the Surface Heat Budget of the Arctic Ocean (SHEBA) field program. The character of the deformation of the ice cover from the two years is very different. Over a domain covering a large part of the western Arctic Ocean (~2.5 × 106 km2), the net divergence of that area during the 6 months of the first winter was 2.7% and for the second winter was 49.3%. In a subregion where the SHEBA camp was located, the net divergence was almost 38% compared to a net divergence of the same subregion of ~9% in 1996/97. The resulting deformation created a much larger volume of seasonal ice than in the earlier year. The net seasonal ice-volume production is 1.6 times (0.38 m vs 0.62 m) that of the first year. In addition to the larger divergence, this part of the ice cover advected a longer distance toward the Chukchi Sea over the same time-span. The total coverage of multi-year ice remained almost identical at ~2.08 × 106 km2, or 83% of the initial area of the domain. In this paper, we compare the behavior of the ice cover over the two winters and discuss these observations in the context of large-scale ice motion and atmospheric-pressure pattern.

Formation of a surface-hoar/depth-hoar complex at the GISP2 site in central Greenland was correlated with large changes in Special Sensor Microwave/Imager (SSM/I) brightness-temperature data. Pass-averaged SSM/I brightness-temperature data over a 1/2° latitude by 1° longitude cell for the 19 and 37 GHz, vertically (V) and horizontally (Η) polarized bands were manipulated to yield differential (V-Η) trends which clearly show a gradual decline as the hoar formation caused a progressively rougher surface with progressively lower density. The hoar episode ended as snowfall, and high winds buried and destroyed the surface-hoar layer and caused rapid V-Η increases in ≈ 1 day. Comparison of the different trends with changes in the field-monitored variables and theoretical values suggest that the V-Η trends are sensitive primarily to changes in surface roughness, and secondarily to near-surface density changes. Consistent expression of trends in microwave brightness temperature over 35 adjacent study cells indicates that this technique may provide a remote-sensing signature capable of defining the timing and spatial extent of surface- and depth-hoar formation in central Greenland.

The mountainous area of west-central Sweden has a varied glacial morphology and three unique landform assemblages appear to mark areas of different basal thermal conditions during the decay of late Weichselian ice. A glacial geomorphological map was constructed through interpretation of aerial photographs at a scale 1:60 000. The relative abundance of landforms interpreted to indicate a frozen bed, a thawed bed, and late-frozen to thawed-bed conditions were used for a first-order reconstruction of the basal temperature pattern of the decaying ice sheet. The features used to outline areas with different temperature regimes during deglaciation are glacial scouring, flutings, eskers, meltwater channels, boulder blankets, Rogen moraines, relict surfaces and thermoerosion features.

In the northern part of the area, as well as along most of the water divide to the Atlantic Ocean, the ice was warm-based during deglaciation. Glacially scoured bedrock, fluting/ drumlinization, subglacial eskers and extensive glacial lake sediments characterize the area. In the high mountain area, lateral meltwater channels are short and curve downslope to form chutes or eskers. The basal ice conditions changed from frozen- to thawedbed in a late stage of the late Weichselian cycle in most of the southern part of the area, shown by the Rogen moraines on both sides of the ice divide. However, substantial areas in the eastern and southern low mountains had frozen-bed conditions during the complete late Weichselian. In the high mountains in the north, only the summits were frozen.

Two uncontrolled mosaics were assembled at an ~1 : 1000 000 scale, covering for the first time almost the entire Larsen Ice Shelf area, using Landsat TM images of 1986-89 and the Kosmos KATE-200 photographic products of late 1975. By comparing them, it was possible to estimate the change along the 600 km north-south ice-shelfs seaward margin where substantial calving has occurred in the recent past. In overall extent, the ice shelf has decreased by ~9300km2 since 1975. The interpretation of the available satellite data also allowed estimates of the ice-shelf’s inland boundary and detection of new surface ice features, especially in the very disturbed region south of Jason Peninsula, which may help to explain the significant calving events occurring in this region. Estimates of surface velocities were derived by photographically co-registering sequential imagery in the chaotic rifted-crevassed area east of Kenyon Peninsula, where conspicuous ice features could be clearly detected even after a 10.4 year time interval. The Landsat TM mosaic, though uncontrolled, provides a basic data set for future studies of global change of the major ice shelf on the Antarctic Peninsula which is probably very sensitive to any climatic trend.

The characteristics of, and the mechanisms causing, multi-decadal variability are currently receiving much attention. This undertaking is particularly challenging in the sub-Antarctic region because of the paucity of data, and the complexity of the governing physical processes.

In this paper we report on aspects of high-southern-latitude variability which appear in the European Centre for Medium-range Weather Forecasts twice-daily analyses for the period 1 January 1980 to 31 August 1996 and in the results of global climate model experiments. We show that the number of cyclone positions in the 50-70°S latitude band exhibits considerable interannual variability, as well as changes on longer time-scales. The seasonal distribution of cyclones is linked with the “semi-annual oscillation". We show that the variability of this phenomenon in a 1000 year run of the GFDL coupled model shows “red” characteristics fand on decadal time-scales is similar to that displayed in the available observationsi. The interaction with the ocean and sea ice is siressed as an important factor in determining the nature of climate variability in sub-Antarctic latitudes.

Detailed ground-penetrating radar (GPR) surveys on the firn–ice transition zones of Kongsvegen, Nordenskjoldbreen, Hansbreen and Werenskioldbreen, Svalbard, are presented. We discuss features seen in GPR radargrams in all polythermal glaciers down-glacier of the firn line. The firn line of a polythermal glacier in GPR data is easily detected with both 50 and 200 MHz radar. By comparison with satellite images, characteristic patterns of reflection are shown to be caused by superimposed ice, but the reflections from the interface between the superimposed ice and the underlying glacier ice are of unknown origin. Layered reflections within the superimposed ice and firn area are likely from layers of ice lenses and relatively low-density firn in the firn area, and from bubble-rich and bubble-poor ice in the superimposed-ice zone. Dipping foliations in the glacier ice down-glacier of the firn line show that the layered reflections from the firn line are preserved, though in much weaker form, even when the firn has been transformed to solid ice.

Radio-echo soundings in four different frequency bands ranging from 30 to 1000 MHz were compared with temperature measurements in boreholes in the accumulation area and ablation area of Finsterwalderbreen (77°26′ N, 15°15′ E), southern Spitsbergen. Finsterwalderbreen is a polythermal surge-type glacier in the quiescent phase after its last surge around AD 1900. The objective of the study was to investigate the relation between internal echos and the glacier ice temperature to map the overall thermal structure of the glacier. The thermal structure is important for ice flow velocities and hydrology of glaciers, and it also affects their ability to surge. At the borehole site in the accumulation area (three boreholes within a range of 60 m), a change in the relative amplitude of the reflected signal is detected in the 320–370 and 600–650 MHz bands at 52–55 m depth. The high-resolution temperature measurements with 2 m intervals show that the transition zone between cold and temperate ice corresponds to the change in the relative amplitude on the 320–370 and 600–650 MHz bandwidth data. The overall thermal structure of the glacier was mapped based on the radar sounding. The radar results show (a) that the glacier is at the pressure-melting point over most of its bed except within 500–700 m of the terminus, and (b) that there is an upper cold ice layer of variable thickness (25–170 m) underlain by temperate ice. This thermal structure is confirmed by the thermistor-instrumented access holes to the bed in both the accumulation and ablation zones of the glacier. The variations in the thermal structure in lower parts of the accumulation area are explained by superimposed ice and ice layers that cause variations in the downward heat transfer by refreezing of meltwater.

The influence of a dam on granular avalanches was investigated. Small-scale laboratory experiments were designed to study the effectiveness of dams built to protect against large-scale dense snow avalanches. These experiments consisted of releasing a granular mass that first flowed down an inclined channel, then hit and overflowed a dam spanning the channel exit and finally spread out on an inclined unconfined run-out zone. First, we measured the volume retained upstream of the obstacle and the overrun length downstream of the obstacle. In the avalanche regime studied here, no simple relation was found between the volume retained and the run-out shortening resulting from the obstacle. The results highlighted that the avalanche run-out was also shortened by complex local energy dissipation. Second, we report the study of the granular deposit propagating upstream of the dam. We show that there was a change in behaviour from an overflow-type regime for low dam heights to a bore regime for higher dam heights. Finally, we show that this change in behaviour directly influenced the local energy dissipation and the resulting avalanche run-out shortening downstream of the dam.

Glaciers on southwestern Bylot Island in the Canadian Arctic flow from an alpine setting in high-grade crystalline Archean terrane, on to coastal lowlands underlain by clastic sedimentary strata of Cretaceous to Tertiary age. We have used the contrasting mineralogy of the substrate as a tool to study subglacial entrainment and transport of debris in two large piedmont glaciers on Bylot Island. High chlorite/ and mica-illite/smectite ratios indicate that most basal debris is derived from crystalline rocks underlying the upper reaches of the glaciers. The subglacial accretion of Cretaceous–Tertiary sediments appears restricted to the lowermost part of the basal zone and is most noticeable near the glaciers’ termini. Ice associated with discrete silly–sandy debris layers is characterized by an isotopic signature indicative of refreezing of meltwater at the glacier sole. The compositional, textural and isotopic characteristics of basal sediment and ice lead us to conclude that subglacial entrainment through basal ice accretion occurs in both the upper and marginal parts of the glaciers.