We describe a project to retrieve a 948m deep ice core from Berkner Island, Antarctica. Using relatively lightweight logistics and a small team, the drilling operation over three austral summer seasons used electromechanical drilling technology, described in detail, from a covered shallow pit and a fluid-filled borehole. A basal temperature well below pressure-melting point meant that no drilling problems were encountered when approaching the bed and the borehole penetrated through to the base of the ice sheet, and sediment was retrieved from beneath the ice.

The one-dimensional snow model SNTHERM is validated using field measurements of snow and superimposed ice thickness and surface energy fluxes. These were performed during the spring-to-summer transition in Svalbard and in the Weddell Sea, Antarctica. Both the seasonal snow-thickness decrease and the formation of superimposed ice are well reproduced by the model. During the three observation periods, observed and modeled snow thickness differ only by 13.1–27.1mm on average. In regional studies, the model is forced with atmospheric re-analysis data (European Centre for Medium-Range Weather Forecasts) and applied to several meridional transects across the Arctic and Southern Ocean. These show fundamental regional differences in the onset, duration and magnitude of snow thinning in summer. In the central Arctic, snowmelt onset occurs within a narrow time range of ±11 days and without significant regional differences. In contrast, the snow cover on Antarctic sea ice begins to melt about 25 days earlier and the length of the Antarctic snow-thinning season increases with increasing latitude. The importance of melting and evaporation for the modeled snow-thickness decrease is very different in the two hemispheres. The ratio of evaporated snow mass to melted snow mass per unit area is derived from the model, and amounts to approximately 4.2 in the Antarctic and only 0.75 in the Arctic. This agrees with observations and model results of the surface energy balance, and illustrates the dominance of surface cooling by upward turbulent fluxes in the Antarctic.

A flow model for cold firn proves to be very successful in calculating the age-depth relation of several deep ice cores drilled on Colle Gnifetti, Monte Rosa, Swiss Alps. The compressibility of firn is taken into account by an appropriate constitutive equation, first employed in glaciology by Gagliardini and Meyssonnier (1997), which is implemented in a finite-element code. Flow models of the Colle Gnifetti saddle glaciation in two and three dimensions are based on digital elevation maps of the surface σnd the bedrock, based on radio-echo soundings of the ice thickness. Firn density and the englacial temperature fields are either prescribed or calculated in coupled models. Measured surface velocities, density profiles, the ages of chemically dated layers in ice cores and the closure of a 100 m deep borehole provide benchmarks for the models. The good agreement of modeled and measured quantities confirms that the model includes the relevant physical processes and particularly that the firn flow law is well suited for this type of glacier. The study provides new constraints on the age of the ice near the base as well as the source regions of the ice in the cores.

An exceptional flow behavior of the basal ice layer was detected in measurements of borehole closure and inclination. Measurtxl6ed deformation rates exceed upper bounds derived from the flow models, and are thus attributed to altered rheological properties.

This paper provides the results of semi-distributed positive degree-day (PDD) modelling for a glacierized river basin in Nepal. The main objective is to estimate the present and future discharge from the glacierized Langtang River basin using a PDD model (PDDM). The PDDM is calibrated for the period 1993–98 and is validated for the period 1999–2006 with Nash–Sutcliffe values of 0.85 and 0.80, respectively. Furthermore, the projected precipitation and temperature data from 2010 to 2050 are obtained from the Bjerknes Centre for Climate Research, Norway, for the representative concentration pathway 4.5 (RCP4.5) scenario. The Weather Research and Forecasting regional climate model is used to downscale the data from the Norwegian Earth System Model general circulation model. Projected discharge shows no significant trend, but in the future during the pre-monsoon period, discharge will be high and the peak discharge will be in July whereas it is in August at present. The contribution of snow and ice melt from glaciers and snowmelt from rocks and vegetation will decrease in the future: in 2040–50 it will be just 50% of the total discharge. The PDDM is sensitive to monthly average temperature, as a 2°C temperature increase will increase the discharge by 31.9%. Changes in glacier area are less sensitive, as glacier area decreases of 25% and 50% result in a change in the total discharge of –5.7% and –11.4%, respectively.

Remote sensing has provided a means of obtaining estimates of snow-covered area, yet traditional methods have had difficulty mapping snow in shaded and vegetated areas. Spectral mixture analysis is a linear mixture modeling technique that shows promise for mapping land surface covers, particularly when imaging spectrometer data are used. Applying this technique to AVIRIS data collected over the Sierra Nevada, California, we have estimated the fraction of snow cover in each pixel, even in areas that are shaded or forested. This modeling technique enables us to map snow cover at the sub-pixel level and provides a means of estimating the errors associated with the calculation.

A new implementation of a calving model, using the finite-element code Elmer, is presented and used to investigate the effects of surface water within crevasses on calving rate. For this work, we use a two-dimensional flowline model of Columbia Glacier, Alaska. Using the glacier’s 1993 geometry as a starting point, we apply a crevasse-depth calving criterion, which predicts calving at the location where surface crevasses cross the waterline. Crevasse depth is calculated using the Nye formulation. We find that calving rate in such a regime is highly dependent on the depth of water in surface crevasses, with a change of just a few metres in water depth causing the glacier to change from advancing at a rate of 3.5 kma–1 to retreating at a rate of 1.9 km a–1. These results highlight the potential for atmospheric warming and surface meltwater to trigger glacier retreat, but also the difficulty of modelling calving rates, as crevasse water depth is difficult to determine either by measurement in situ or surface mass-balance modelling.

The snow/ice albedo was studied during a 4 week field experiment over first-year sea ice in the Gulf of Bothnia, Baltic Sea, in spring 2004. Observations were made on radiative fluxes, cloud cover, wind, air temperature and humidity, as well as snow/ice temperature, thickness, density and grain size. The albedo variation during the observation period was large: the daily mean albedo ranged from 0.79 over a new snow cover to 0.30 over bare, melting ice. The evolution of the albedo was related to the surface properties, but existing parameterizations based on Arctic data did not explain the observations well. The snow thickness was found to be the most critical factor affecting the albedo. A new parameterization was derived for the albedo dependence on snow thickness, to be applied over the Baltic Sea in spring, when periods of melting and freezing alternate but the ice is still relatively thick (about 0.6 m). The diurnal cycle of solar radiation was large, and the snow/ice metamorphism due to the melting during daylight and refreezing during the night caused a diurnal albedo cycle with a maximum in the early morning and a minimum in the afternoon, with an albedo difference up to 0.14 between the two.

State-of-the-art thermomechanical models of the modern Greenland ice sheet and the ancient Laurentide ice sheet that covered Canada at the Last Glacial Maximum (LGM) are not able to explain simultaneously the observed forms of these cryospheric structures when the same, anisotropy-enhanced, version of the conventional Glen flow law is employed to describe their rheology. The LGM Laurentide ice sheet, predicted to develop in response to orbital climate forcing, is such that the ratio of its thickness to its horizontal extent is extremely large compared to the aspect ratio inferred on the basis of surface-geomorphological and solid-earth-geophysical constraints. We show that if the Glen flow law representation of the rheology is replaced with a new rheology based upon very high quality laboratory measurements of the stress-strain-rate relation then the aspect ratios of both the modern Greenland ice sheet and the Laurentide ice sheet, that existed at the LGM, are simultaneously explained with little or no retuning of the flow law.

Monitoring the glacier mass balance of summer-accumulation-type Himalayan glaciers is critical to not only assess the impact of climate change on the volume of such glaciers but also predict the downstream water availability and the global sea-level change in future. To better understand the change in meteorological parameters related to glacier mass balance and runoff in a glacierized basin and to assess the highly heterogeneous glacier responses to climate change in the Nepal Himalaya and nearby ranges, the Cryosphere Monitoring Project (CMP) carries out meteorological observations in Langtang Valley and mass-balance measurements on Yala Glacier, a debris-free glacier in the same valley. A negative annual mass balance of –0.89m w.e. and the rising equilibrium-line altitude of Yala Glacier indicate a continuation of a secular trend toward more negative mass balances. Lower temperature lapse rate during the monsoon, the effect of convective precipitation associated with mesoscale thermal circulation in the local precipitation and the occurrence of distinct diurnal cycles of temperature and precipitation at different stations in the valley are other conclusions of this comprehensive scientific study initiated by CMP which aims to yield multi-year glaciological, hydrological and meteorological observations in the glacierized Langtang River basin.

We give a review of drilling to the beds of the Greenland and Antarctic ice sheets, with a history of just a century. We use a chronological rather than a geographical ordering to emphasize the way drilling has developed. The review is divided into two parts: core drilling and hole-only drilling for access to the beds or the deep interior of the ice sheets. This is an overview, not a comprehensive report on each project. While we have endeavoured to include all projects that fit our selection criteria, we have not provided all the technical details.

In Switzerland three large snowfall periods led to numerous large avalanche events, causing the deaths of 17 people, damage to about 1000 buildings and blockage of many important traffic systems. This situation was a valuable test of the avalanche-hazard mapping procedure developed in Switzerland since the last extreme avalanche winter in 1951. In most cases, the avalanches stopped within the avalanche-hazard zones. However, approximately 40 of about 1200 large avalanche events passed the limits of the existing hazard zones. The primary deficiency was underestimation of the hazard of powder-snow avalanches. The other reason the hazard-zone boundaries were passed was multiple avalanche events in a single track within a short time period. In addition, some fracture depths were larger than those used in avalanche-dynamics calculations. Therefore, the guideline assumptions for defining the fracture depths are questioned. Winter 1999 impressively underlined the danger of avalanches in mountainous regions. It emphasized the importance of avalanche-hazard mapping, showed the existing deficiencies and provided a large amount of field data that will help to improve our knowledge of avalanche dynamics.

The Canadian Lake Ice Model (CLIMo), a one-dimensional, thermodynamic model with unsteady heat conduction and penetrating solar radiation, is used to simulate ice growth and decay on shallow ponds in and near Fairbanks, central Alaska, USA. Simulations are compared with observations of ice thickness and composition (snow ice, congelation ice), freeze-up, break-up and duration. Simulations run using US National Weather Service meteorological data as input variables do not agree well with ice-thickness measurements. The simulations improve significantly when the model is run with more representative, locally measured data for air temperature and depth of snow on the ice. The causes of some discrepancies between simulations and observations are discussed and some suggestions for model improvements are made.

Svalbard ice cores have not yet been fully exploited for studies of climate and environmental conditions. In one recently drilled ice core from Lomonosovfonna, we have studied the methanesulfonic acid (MSA) records in relation to temperature and sea ice. Under the present climatic conditions, MSA appears to be negatively correlated with the sea-ice conditions in the Barents Sea, and positively correlated with the instrumental temperature record from Svalbard. However, prior to about 1920 the MSA concentrations were about twice as high, despite the more extensive sea-ice coverage. After exploring different possibilities, we suggest that MSA concentrations were higher in the 19th century than in the 20th century due to increased primary production, in response to increased vertical stability of the sea surface layers, caused by increased meltwater production from the more extensive sea-ice cover. Thus, the MSA record from Lomonosovfonna probably both is a measure of the regional sea-ice variability on the multi-decadal scale and reflects locally favorable conditions for marine biogenic dimethyl sulfide (DMS) production on the sub-decadal scale.

The ongoing retreat of mountain glaciers necessitates the development of future scenarios of glacier runoff. These scenarios are not only governed by future climate scenarios influencing glacier mass balance but also by the glacier volumes, which are subject to melt. Ground-penetrating radar (GPR) is a valuable tool for measuring the thickness of mountain glaciers, although ground-based measurements are labour-intensive, so not all glaciers can be surveyed. This study presents the results of GPR surveys on 64 Alpine glaciers, carried out between 1995 and 2010. The glacier areas range from 0.001 to 18.4 km2, and their ice thickness was surveyed with an average density of 36 points km-2. The point measurements were extrapolated manually to derive volume maps. The mean ice thickness varies between 10 and 92 m; the maximum ice thickness is about three times the mean thickness. According to the glacier state recorded in the second glacier inventory, the 64 glaciers cover an area of 223.3 ± 3.6 km2, with a mean thickness of 50 ± 3 m and a glacier volume of 11.9 ± 1.1 km3. The mean maximum ice thickness is 119 ± 5m.

The kinetics of ice growth on the prismatic and basal planes is studied by molecular dynamics simulations. The time evolution of two systems has been investigated. In one a slab of ice is initially in contact with supercooled water, while in the second the ice is in contact with a supercooled salt solution. The simulations were done at a temperature below the eutectic temperature, and complete solidification is observed. The total freezing time is longer in the systems with ions than in the systems with pure water. The final state for the salt systems always shows the formation of ion clusters. For the ionic system growing on the prismatic plane, an intermediate metastable state is observed before total solidification. The duration of this metastable state depends on the ability of the system to get all the ions participating in cluster formation. The simulations enable understanding of the mechanisms for ice formation under different solution conditions.

This paper aims to show how recent knowledge developed in the field of avalanche research can be used for a real case study, the Taconnaz avalanche path, where passive structures already existed but had to be improved. First a morphological analysis of the site is done and historical data are analysed. Second, each recorded event is back-calculated using a numerical model of dense-flow avalanches. For each surveyed avalanche, parameters at the entry of the runout zone upstream of the defence structures are defined. Third, a statistical analysis of these parameters allows characterization of 100 year return period events. Fourth, physical and numerical models of dense avalanches interacting with defence structures are combined in order to design the most effective passive structure able to contain the reference scenarios. Finally, physical and numerical modelling of the interaction between the powder avalanche and the designed defence structure is performed, to show that the proposed improvements do not increase the residual risk due to the powder part in areas downstream of the defence structures.

Ship-borne and airborne infrared radiometric measurements during the Arise cruise of September–October 2003 permitted in Situ validation Studies of two Satellite-based ice Surface Skin temperature algorithms: the AVHRR Polar Pathfinder Ice Surface Temperature and the MODIS Sea Ice Surface Temperature. Observations of Sea ice from the Aurora Australis Ship’s rail using a KT-19.82 radiometer were conducted between 25 September and 21 October during clear-sky overflights by AVHRR (41 passes) and MODIS (17 passes) on their respective Satellite platforms. Data from both Sensors Show highly linear fits to 1 min integrated radiometer Spot measurements, Spanning the range 245–270 K with a ±1.4˚C, 1σ (AVHRR) and ±1.0˚C (MODIS) variation relative to a 1: 1 relationship. There was no Significant offset. Helicopter observations made with a KT-19.85 radiometer on three dates (8, 19 and 20 October) provided more data (236 gridcell Sites total), but over a more limited Sea-ice Skin temperature range (252–268 K), with higher variation (±1.7˚C, 1σ) due to mixed-pixel issues. Comparison of MODIS and AVHRR algorithms directly, with both images acquired during a helicopter flight, indicates very high correlation and near-unity Slope for the two Satellite-based algorithms. Ship air-temperature data during the validation indicated moderate to Strong inversions over Sea ice under clear Skies. These formed and decayed rapidly (tens of minutes) as clouds moved out of and into the zenith area.

In this paper we first summarise major findings of recent atmospheric studies of nitrogen and sulphur species present in the boundary layer of coastal Antarctic regions. We then discuss the implications of such atmospheric data for the interpretation of nitrate, ammonium, methanesulphonate and sulphate records in deep ice cores extracted from central Antarctica in terms of past atmospheric chemistry changes.

The 2008/09 surge of central Yulinchuan glacier (CYG) on the northwestern slope of Muztag mountain, Tibetan Plateau, is studied based on satellite remote sensing. The widely used cross-correlation feature-tracking method was used to collect satellite image control points and validate their geometric accuracies, as well as to derive glacier surface velocity. Changes in glacier length and area were also retrieved. Results show that the surge of CYG initiated in May 2008 and terminated in July 2009. Two diffluent glacier termini advanced 590 ± 26 m (5.1 ± 0.2% of the 2004 length) and 182 ± 26m (1.8 ± 0.3%), respectively, and glacier area increased by ∼1.41 ± 0.11 km2 (4.6 ± 0.4% of the 2004 area) during this period. The most significant surge period was October 2008 to March 2009, when most of the terminus advances and area increases occurred. The glacier surface drastically crevassed during this time, as much as 1657 ± 297 m of horizontal surface displacements were produced by surge ice, and maximum surface speed reached 13 ± 1.5 m d-1. Results of transverse and longitudinal velocity profiles revealed two surge waves during this surge of CYG.

In the framework of the PNRA–ITASE (Programma Nazionale di Ricerche in Antartide–International Trans-Antarctic Scientific Expedition) project, during the field season 1998/99, surface snow (1m cores and pits) and shallow firn cores (10–50m) were collected along a traverse from Terra Nova Bay (northern Victoria Land) to Dome C (East Antarctic ice sheet). Results of chemical, tritium and stable-isotope composition are presented here for the 1 m cores, some snow pits and the first 2 mof some shallow firn cores. the δ18O values show a regular trend with altitude, and the regression line between δ18O and surface temperature is δ18O = 0.99T (˚C) – 0.67. Primary aerosol components such as Na+, Cl–, Ca2+,Mg2+ and K+ show high concentrations decreasing with increasing altitude in the first 250–350km from the coast. At greater distances, concentrations of these species remain more constant. NO3– concentration shows an irregular profile with a progressive decreasing trend as altitude increases. Non-sea-salt (nss) SO42– concentration decreases up to about 250 km from the coast, increases 250–770 km from the coast and remains relatively constant in the most remote stations. Methanesulphonate (MSA) concentration shows high variability. the MSA/nssSO42– ratio exhibits a decreasing trend 250–550km from the coast. With increasing distance, the ratio shows moderate oscillations. nssCl– concentration shows a progressive increase as distance from the coast increases, in agreement with the increasing influence of HCl on the Cl– budget of the inland Antarctic atmosphere. Post-depositional re-emissions of Cl– and NO3– were found at stations characterized at the surface by long-term accumulation hiatus (wind crusts). the chemical-species distribution is consistent with the presence in the studied area of local and long-range transport processes, post-depositional effects and snow-accumulation variations observed along the traverse.