An experimental study of the fracture mechanics and rheology of ice from the Ronne Ice Shelf, Antarctica, is currently being undertaken. The apparent critical stress-intensity factor (or apparent fracture toughness, KQ) for crack propagation has been measured using a three-point bend method for inducing crack growth perpendicular to the axis of cylindrical ice-core specimens. Tensile crack nucleation under applied uniaxial compressive stress has also been evaluated. Both methods have allowed a profile of ice elastic and fracture properties with depth through the ice shelf to be constructed. Preliminary results indicate that the measured elastic modulus increases with depth through the firn and upper meteoric ice before reaching a constant value in the deeper, dense meteoric and basal marine ice. The resistance to fracture, as measured by changes in apparent fracture toughness and crack-nucleation stress, increases with depth right through the firn and meteoric ice layers. A simple fracture mechanics model applied to the Ronne Ice Shelf indicates that crevasses form from small surface cracks, less than 40 cm deep, which quickly grow to depths of 40–60m and then remain stable.

Measurements of sensible- and latent-heat fluxes under stable conditions are rare. In order to obtain indirect measurements of turbulent fluxes, meteorological data measured at the Col de Porte laboratory (1320 m a.s.l, France) under very stable conditions (cold, clear night with low wind) are used. The radiative fluxes are measured, the conduction within the snowpack is calculated using the snow model Crocus and the turbulent fluxes are determined as a residual term of the surface-energy balance equation. These data were used to fit a new parameterization of the turbulent fluxes for the snow model. The turbulent fluxes are increased as compared to the theory. Crocus was also applied to the data from the LEADEX92 experiment and the turbulent fluxes calculated by the model were compared to the fluxes measured using sonic anemometers/thermometers on the site.

Based on the results of geochemical and glaciological investigations in snow pits and shallow cores, regional stack series of air temperature in central Antarctica (in the southern part of Vostok Subglacial Lake) were obtained, covering the last 350 years. It is shown that this parameter varied quasi-periodically with a wavelength of 30–50 years. The correlation of the newly obtained record with the circulation indices of the Southern Hemisphere (SH) shows that the central Antarctic climate is mainly governed by the type of circulation in the SH: under conditions of zonal circulation, negative anomalies of temperature and precipitation rate are observed, whereas the sign of the anomalies is positive during meridional circulation. In the 1970s the sign of the relationship between many climatic parameters changed, which is likely related to the rearrangement of the climatic system of the SH. The data suggest that during the past 350 years such events have taken place at least five times. The stable water isotope content of the central Antarctic snow is governed by the summer temperature rather than the mean annual temperature, which is interpreted as the influence of ‘postdepositional’ effects.

During the twentieth century, glacial outburst floods have been the most destructive natural events on Mount Rainier, a stratovolcano in the Cascade Range in Washington State, U.S.A. In the period between 1930 and 1980 numerous floods were reported from five glaciers on the mountain, most of which flowed from Nisqually, Kautz, or South Tahoma Glaciers on its southern flank. Such floods threaten lives and property because they occur without warning and quickly mobilize the loose volcanic debris into debris flows.

A monitoring program was begun in 1987 which was designed to measure the dimensions and timing of outburst floods, but this has been unsuccessful because no floods have yet occurred on the monitored streams. Four floods did burst from South Tahoma Glacier that was unmonitored, but in spite of this they have been useful in providing evidence of flood storage and release mechanisms. All flood volumes were found to be of approximately similar orders of magnitude, of 1 × 105 m3 of water, indicating that all floods probably had similar mechanisms for storage and release of water. Hydraulic pressure considerations indicate that such a large volume of flood water would be stored at the bed of the glacier rather than in isolated englacial cavities. The stepped bedrock terrain provides an ideal setting for the formation of subglacial cavities capable of storing the volumes of flood water noted.

A surface-energy/mass-balance model with an explicit calculation of meltwater refreezing and superimposed ice formation is applied to midre Lovénbreen, Spitsbergen, Svalbard. The model is run with meteorological measurements to represent the present climate, and run with scenarios taken from global climate model predictions based on the IS92a emissions scenario to represent future climates. Model results indicate that superimposed ice accounts for on average 37% of the total net accumulation under present conditions. The model is found to be highly sensitive to changes in the mean annual air temperature and much less sensitive to changes in the total annual precipitation. A 0.5˚C decade–1 temperature increase is predicted to cause an average mass-balance change of –0.43 ma–1, while a 2% decade–1 increase in precipitation will result in only a +0.02 ma–1 change in mass balance. An increase in temperature results in a significant decrease in the size of the accumulation area at midre Lovénbreen and hence a similar decrease in the net volume of superimposed ice. The model predicts, however, that the relative importance of superimposed ice will increase to account for >50% of the total accumulation by 2050. The results show that the refreezing of meltwater and in particular the formation of superimposed ice make an important positive contribution to the mass balance of midre Lovénbreen under present conditions and will play a vital future role in slowing down the response of glacier mass balance to climate change.

We analyze sea-ice conditions along seven segments of the Northern Sea Route (NSR) over four time periods. We researched sea ice by segment, using data from the satellite microwave sensors SMMR, SSM/I and AMSR-E. The four analysis periods (periods I–IV: 1980–88, 1989–2001, 2002–06 and 2007–11, respectively) were determined based on changes in the extent of minimum sea ice throughout the Arctic Ocean. Sea ice showed a decreasing tendency from period I to period IV. For example, sea-ice area in period IV decreased compared to previous periods in the eastern East Siberian Sea and around Severnaya Zemlya, areas that had very high sea-ice concentrations in period I. Sea-ice area in the eastern East Siberian Sea decreased sharply during period III, whereas the Severnaya Zemlya area maintained a high ice concentration. In period IV, sea-ice coverage around Severnaya Zemlya was low, although it remained at 25% in the area east of Severnaya Zemlya, which is a key area for navigation. The proportion of multi-year (MY) ice drastically decreased after winter 2002, and only a small amount of MY ice existed in the winters of 2003–06. MY ice disappeared from the eastern East Siberian Sea after 2007. On the other hand, around Severnaya Zemlya the proportion of MY ice showed cyclic ups and downs between 1997 and 2008. Thus, the persistence of various types of sea ice varies according to region. The persistence of various types of sea ice around Severnaya Zemlya also varied each year.

Finding a new safe and ecologically friendly borehole fluid is one of the most pressing problems for forthcoming ice-drilling projects. Not all recent borehole fluids qualify as intelligent choices from safety, environmental and other technological standpoints. We propose the use of silicone oils as the borehole fluid. The most suitable type of silicone oils for deep ice drilling are low-molecular (or volatile) dimethyl siloxane oils (DSOs). Low-molecular DSOs are clear, water-white, tasteless, odorless, neutral liquids. They are hydrophobic and inert substances that are stable to water, air, oxygen, metals, wood, paper, plastics, etc. Of the DSOs, class 2 grades of KF96-1.5cs and KF96-2.0cs most fully fit our criteria for choice as borehole fluids. The final conclusion as to the suitability of DSOs for ice deep drilling will be made after the experiments in a test borehole.

The glaciers of central Asia provide suitable locations from which to recover continuous, high-resolution glaciochemical records on a continental scale. Although the glaciochemical investigations undertaken to date in central Asia are few in number and limited in terms of spatial coverage and length of record, some preliminary observations can be made concerning regional and seasonal trends in snow chemistry in this region.

The sodium chloride ratio for most snow samples collected in central Asia approaches the ratio found in sea water (0.86 in μeq kg−1), reflecting a marine source for these constituents. Sodium and chloride concentrations are, on average, 3–10 times higher in the Himalayas than in the Karakoram, demonstrating the greater influence of monsoonal sources of moisture in the Himalayas. Very high sodium concentrations from Khel Khod Glacier probably reflect a local crustal source from surrounding ice-free areas. Low nitrate concentrations were found in snow collected from the southern margin of the Himalayas and high concentrations in snow deposited on the north margin of the Himalayas. This strong regional trend in the spatial distribution of nitrate suggests the influx of continental aerosols, rich in nitrate, originating from the arid regions of central Asia. High calcium concentrations measured in snow from Mount Everest and the north-west corner of China are also indicative of dust derived from the arid regions of central Asia. Very high sulfate concentrations found in snow from the Tien Shan and the Bogda Shan most likely reflect local anthropogenic sources. The altitude effect on isotopie composition is not apparent from snow samples collected in central Asia.

Understanding the processes which control the chemical content of snow, the local-to-regional scale complexities, and the seasonal variability are fundamental steps necessary to assess the potential for recovering representative long-term glaciochemical records from central Asia.

We investigate the relationships between meteorological, hydrological and glaciological data collected at Haig Glacier, Alberta, Canada, for the 2002 and 2003 ablation seasons. Correlation, lag cross-correlation and multivariate regression analyses are employed to assess the seasonal evolution of relationships between temperature, temperature residuals, total daily radiation, albedo, accumulation-area ratio (AAR) and total daily discharge (Qi). Early-season melt is temperature-dependent, when AAR remains high and the hydraulic properties of the snowpack limit both diurnal discharge variability and a rapid hydrologic response. As the melt season progresses, a decreasing AAR and ripening of the snowpack induce a glacier-wide decrease in albedo, and a structured radiation–discharge response is observed. Radiation-detrended temperature values offer modest improvements over physical temperature values in multivariate regression models estimating daily discharge values. Using a detrended-temperature indexed melt model, we assess the transport efficiency of the glacial hydrologic system through a comparison of total modelled daily melt and observed discharge. Transport efficiency values support the notion of a purge effect during freezing events and at the end of the ablation season, and suggest that it is the evolution of the supraglacial drainage system that controls diurnal discharge variability.

The results from long-term simulations with a climate model using historical sea surface temperatures (SSTs) are used to study Antarctic accumulation rates and their relationship, or sensitivity, to temperature changes. The model used has a horizontal resolution of approximately 2° by 2°. The SST data comprise reconstructed monthly values on a global grid for the period 1950-91. The results yield an estimate for the area-averaged value accumulation rate over grounded ice of 160-180 mm w.e. a−1. The spatial pattern of the simulated trends over the period of integration indicates that the results for much of East Antarctica are consistent with evidence deduced from ice cores. The ice-sheet surface is estimated to have warmed by +0.73°C (a rate of +0.18°C per decade), while the accumulation rate is estimated to have increased by + 7.7 mm a−1 (a rate of + 1.9 mm a−1 per decade). The estimate for sensitivity is +12.5 mm a−1 per degree of warming, which can be interpreted as about -0.4 mm of sea level per year.

Snow-accumulation rates and rates of ice-thickness change (mass balance) are studied at several sites on Siple Dome,West Antarctica. Accumulation rates are derived from analyses of gross beta radioactivity in shallow firn cores located along a 60 km transect spanning both flanks and the crest of the dome. There is a north–south gradient in snow-accumulation rate across the dome that is consistent with earlier radar mapping of internal stratigraphy. Orographic processes probably control this distribution. Mass balance is inferred from the difference between global positioning system (GPS)-derived vertical velocities and snow-accumulation rates for sites close to the firn-core locations. Results indicate that there is virtually no net thickness change at four of the five sites. the exception is at the northernmost site where a small amount of thinning is detected, that appears to be inconsistent with other studies. A possible cause of this anomalous thinning is recent retreat of the grounding line of Ice Stream D.

The geodetic mass balance of the western Svartisen ice cap in northern Norway is determined, in this work, from photogrammetry on vertical aerial photographs taken in 1968, 1985 and 2002. The existing 1968 digital terrain model (DTM) was generated using analogue photogrammetry, and the 1985 and 2002 DTMs are newly generated using digital photogrammetry. The geodetic mass balance for 1968–85 is –2.6±0.8mw.e., and for 1985–2002 it is –2.0±1.6mw.e. The area of western Svartisen decreased from 190 km2 in 1968, to 187 km2 in 1985 and to 184 km2 in 2002. The outlet glacier Flatisen in the southeast retreated 1700 m over the two periods. The geodetic mass balance is also determined for Engabreen drainage basin, as –2.1±0.9mw.e. for the first period, and –0.3±2.4mw.e. for the second. The results for Engabreen are compared to traditional mass balances, and the large deviations cannot be explained from uncertainties determined for the geodetic method. The assessed errors contributing to the uncertainty in the geodetic mass balance are elevation errors, uncertainties from the applied melt correction, and the use of Sorge’s law, assuming constant snow thickness and density.

A probabilistic approach to modelling avalanche origin and dynamics is developed. An avalanche process is considered as a single event. As a basis, the physically established deterministic models describing the processes of avalanche origin and motion are used. On the other hand, input data and/or parameters of these models are treated as random variables. The study is restricted only with respect to the dynamic stage of the avalanche process. It is assumed that the initial volume of snow, entrained into the motion, and the coefficients of dry and turbulent friction of the avalanche body are random variables. The other input data are deterministic. Three kinds of distribution laws for random variables are examined: uniform, normal and exponential. Several hundred numerical tests, carried out for the selected avalanche path No. 22 in the Khibiny region, Russia, allowed construction of the distribution functions for the output parameters of the dynamic model. These parameters are the front velocity, the height and the volume of the avalanche body at fixed points of the avalanche path. No very strong dependence of distribution functions on the kind of distribution laws was found. The model and empirical distribution functions are very close to one another for run-out distances and sufficiently close for depths and volumes of snow deposits.

Knowledge of permafrost characteristics and distribution in Antarctica and their relationships with present and past climates is still poor. This paper reports investigations on permafrost in an area located between Nansen Ice Sheet to the south and Mount Melbourne (2732 m a.s.l.) to the north. Investigation methods included geomorphological surveys and geoelectrical soundings as well as crystallography, chemical and isotopic analyses of the ground ice. Geomorphological surveys helped to explain the relationships between periglacial landforms (e.g. rock glaciers and patterned ground) and the glacial history of the area. Geoelectrical soundings allowed us to define different ground-ice units in the ice-free areas. Each unit was characterised by a different type of permafrost (dry or ice-poor permafrost, marine or continental massive buried ice and sub-sea permafrost). To identify the nature of ground ice, trenches were dug and some shallow boreholes were drilled to a maximum depth of-3.6 m in massive buried ice. Samples of both ice-poor permafrost and massive ice were collected and analyzed. Chemical, isotopic δ18O and crystal analyses were also carried out. The relationships between climate and thermal regimes of the active layer and the upper part of permafrost were determined using a monitoring station for ground temperatures at Boulder Clay Glacier, near the Italian Antarctic station. During winter, there were several significant thermal-inversion events in the ground, which cannot be explained only by air-temperature changes, suggesting a possible influence of winter snowfall, even if these events are usually considered very rare.

We investigate the sensitivity of the ocean circulation in the Filchner Trough to changes in the large-scale oceanic environment and its impact on the mass balance of the Filchner Ice Shelf, Antarctica. Three experiments with a three-dimensional ocean model describe (i) the current situation, (ii) a scenario with increased ocean temperatures, and (iii) a scenario with reduced sea-ice formation rates on the adjacent continental shelf. in the final discussion brief results of a combined scenario with increased ocean temperatures and reduced sea-ice formation are presented. The changes from the current situation affect the circulation in the Filchner Trough, and melting and freezing processes beneath the ice shelf. The latter affect the amount and properties of Ice Shelf Water (ISW), a component of Antarctic Bottom Water. Net basal melt rates provide an overall measure for the changes: while the control run yields 0.35 m a−1 net melting averaged over the Filchner Ice Shelf area, the warming scenario results in a more than twofold increase in ice-shelf mass loss. Reduced production of High Salinity ShelfWater due to smaller sea-ice formation rates in the second scenario leads, on the other hand, to a decrease in basal mass loss, because the deep cavity is less well ventilated than in the control run. ISW is cooled and the ice shelf is stabilized under this scenario, which is arguably the more likely development in the southern Weddell Sea.

The horizontal divergence of drifting snow was estimated from the ice-sheet topography on Mizuho Plateau, East Antarctica. The calculation was made by using a relationship between the snow-drift transport rate and wind speed estimated from the surface slope. The divergence thus estimated for Mizuho Station (70°42′S, 44°20′E) was consistent with observations of surface net mass balance, precipitation and sublimation. Around the southern region of the Yamato Mountains, a large divergence was predicted and this is believed to be the principal cause of the bare ice field. Other factors in the formation and preservation of the bare-ice area are discussed.

The preferred c-axes orientation (fabric) observed in cold polar ice is induced by intracrystalline slip only when the grain-boundary migration rate is low enough (i.e. corresponding to grain growth or rotation recrystallization regimes). Fabrics reflect the entire thermomechanical history of the ice and strongly influence its mechanical behaviour. Large viscoplastic anisotropy is always associated with pronounced fabrics. We use a viscoplastic self-consistent (VPSC) polycrystal deformation model to calculate fabric development. In this model, stress- and strain-rate fields are not uniform within the polycrystal and both equilibrium and compatibility conditions are fulfilled. We compare fabrics measured on thin sections along the GRIP ice core (central Greenland) with those calculated down to a depth of 2800 m. Behaviours predicted by uniform stress and uniform strain bounds are presented for comparison. Predictions of the VPSC model are in close agreement with measurements within the upper 650 m, which corresponds to the entire grain-growth zone. Deeper clown, the simulated fabric strength appears to be too high. A simple calculation shows that this discrepancy may be fully attributed to the effects of rotation recrystallization.

Radiocarbon dates of 13 000 a BP at the Cheboygan bryophyte bed in Michigan and 11 800 a BP at the Two Creeks site in Wisconsin bracket three ice advance/retreat cycles and one advance to the Two Creeks site of the Lake Michigan lobe. These advances are documented by individual till sheets separated by lacustrine fine sand and silt-clay units. The tills are distinguishable only by small differences in grain-size distribution and clay-mineral content. They probably reflect closely the composition of the sediment being deposited in the Lake Michigan basin between advances. Because of lack of exposure and probable erosion of pre-existing material by each successive ice advance, the maximum extent of retreat between the deposition of the tills cannot be documented. We can demonstrate, however, that a total of at least 850 and perhaps over 1 000 km of combined retreat and advance took place during this period of 1 200 a. This implies that the change in ice-margin position averaged 0.7 to 0.9 km a-1, a rate higher than most recorded on modern glaciers. Since this is an average rate over 1 200 a and encompasses several advances and retreats, the actual rate of change in ice-margin position must at times have been considerably more rapid.

There is very little evidence in the pollen record of climatic changes that would explain rapid advances and retreats of this magnitude. This observation has led to suggestions that late Wisconsin age advances in various parts of the Great Lakes were surges unrelated to climate change.

We suggest instead that the shape of the Lake Michigan basin, and the substantial changes in water level that might have occurred in it, could have greatly amplified the smaller fluctuations of the ice margin that have been documented across the eastern United States (presumably resulting from changes in mass balance), and so could have produced the rapid advances and retreats seen in the stratigraphic record.

The Lake Michigan basin consists of two deep areas with a high area in between. Present water depths are over 280 m in the northern basin, less than 60 m on the mid-lake high, and more than 160 m in the southern basin. All of the ice advances discussed above seem to have stopped either on the northern (up-stream) side or on the crest of the mid-lake high. Even conservative estimates of the amount of isostatic crustal depression at that time suggest that if water could drain into the eastern Great Lakes during retreat of the ice to the north end of the basin, lake level could have dropped as much as 220 m. Although there is no stratigraphic evidence that drainage out of the north end of the basin took place between these ice advances, there are valleys cut in drift and bedrock extending from the north basin eastward toward the Lake Huron basin. It is possible that these valleys formed during the rapid draining of the lake between ice advances. Whenever ice advanced, blocking the northern outlet, lake level rose back to the Glenwood level (which has well-developed beaches), and the lake drained through the Chicago outlet to the south.

Our model is as follows. Consider a grounded ice sheet filling the northern basin and terminating at an equilibrium position on the crest or up-stream side of the mid-lake high. The ice sheet would be unstable in that any initial retreat of the grounding line (i.e. the boundary between the grounded ice and either floating ice or open water) would accelerate as the grounding line moved northward into deeper water. Now let a general marginal retreat occur. Rapid retreat of the grounding line follows until the grounding line passes the northern lake outlet. The consequent large drop in lake level leads then to a readvance of the grounding line, re-blocking the outlet and causing the basin to refill with water. A new equilibrium position of the grounding line is established on the northern side of the basin. As the mass balance increases again, associated with a general marginal advance of the ice sheet, an ice shelf forms (if it was not already there) and grows southward until it grounds on the mid-lake high. That then causes the grounding line to advance rapidly to the position of the margin, whereupon the process is ready to repeat. Each advance would be smaller than the previous because rebound would be tilting the north end of the lake upward, shoaling the water and causing ice shelves to ground further north on the mid-lake high. In addition, the mass of ice to the north was probably shrinking.

Grain-size distribution and mineralogic characteristics of the tills along the Lake Michigan shoreline have been analyzed extensively. However, the existence of a floating ice shelf in the basin at various times during this period cannot, at present, be deduced from the sediment.

With the launch of Landsat 7 a new band was added to the Landsat Enhanced Thematic Mapper Plus (ETM+). The new panchromatic band 8 covers wavelengths of 0.52–0.92μm and extends over band 2 (0.525–0.605 μm), band 3 (0.630–0.690 μm) and band 4 (0.750–0.900 μm). Its high resolution, with a pixel length of 15 m, is of interest for high-spatial-resolution analysis. This project focused on using Landsat 7 band 8 as a precise tool to obtain remotely the size and shape of permanent snowpatches in the mountainous area west of Abisko, Sweden. In the supervised classification employed, shadowed and non-shadowed areas were classified separately. Supervision of the classification was based on ground-truthing consisting of photographic mapping of the snow cover in the study area. The results from this single-band classification were compared to the results from the normalized- difference snow index (NDSI) and false-color images using bands 2, 4 and 5. This comparison showed similar estimates of the total amount of snow-covered area, with the additional advantage that the Landsat 7 band 8 (LB8) classification detects details in the extent of individual snowfields. This new application and the insights documented here support the use of Landsat 7 band 8 for snow-cover investigations in the future.

Co-registered and continuous satellite data of sea-ice concentrations and surface ice temperatures from 1981 to 2000 are analyzed to evaluate relationships between these two critical climate parameters and what they reveal in tandem about the changing Arctic environment. During the 19 year period, the Arctic ice extent and actual ice area are shown to be declining at a rate of –2.0±0.3% dec –1 and 3.1 ±0.4% dec–1, respectively, while the surface ice temperature has been increasing at 0.4 ±0.2 K dec–1, where dec is decade. The extent and area of the perennial ice cover, estimated from summer minimum values, have been declining at a much faster rate of –6.7±2.4% dec–1 and –8.3±2.4% dec–1, respectively, while the surface ice temperature has been increasing at 0.9 ±0.6K dec–1. This unusual rate of decline is accompanied by a very variable summer ice cover in the 1990s compared to the 1980s, suggesting increases in the fraction of the relatively thin second-year, and hence a thinning in the perennial, ice cover during the last two decades. Yearly anomaly maps show that the ice-concentration anomalies are predominantly positive in the 1980s and negative in the 1990s, while surface temperature anomalies were mainly negative in the 1980s and positive in the 1990s. The yearly ice-concentration and surface temperature anomalies are highly correlated, indicating a strong link especially in the seasonal region and around the periphery of the perennial ice cover. The surface temperature anomalies also reveal the spatial scope of each warming (or cooling) phenomenon that usually extends beyond the boundaries of the sea-ice cover.