Glacier responses to future climate change will affect hydrology at sub-basin scales. The main goal of this study is to assess glaciological and hydrological sensitivities of sub-basins throughout the Hindu Kush-Himalaya region. We use a simple geometrical analysis based on a full glacier inventory and digital elevation model to estimate sub-basin equilibrium-line altitudes (ELAs) from assumptions of steady-state accumulation area ratios. The ELA response to an increase in temperature is expressed as a function of mean annual precipitation, derived from a range of high-altitude studies. Changes in glacier contributions to streamflow in response to increased temperatures are examined for scenarios of both static and adjusted glacier geometries. On average, glacier contributions to streamflow increase by ~50% for a +1 K warming based on a static geometry. Large decreases (-60% on average) occur in all basins when glacier geometries are instantaneously adjusted to reflect the new ELA. Finally, we provide estimates of sub-basin glacier response times that suggest a majority of basins will experience declining glacier contributions by 2100.

Correlation between glaciochemical time Series from an ice core collected on Devon Ice Cap, Nunavut, Canada, and gridded time Series of Sea-ice concentrations reveals Statistically Significant inverse relationships between Sea-salt concentrations (mainly Na+, Mg2+ and Cl–) in the ice core and Sea-ice cover in Baffin Bay over the period 1980–97. An empirical orthogonal function (Eof) analysis performed on all major ions Shows that the dominant mode of glaciochemical variability (Eof1) represents a Sea-salt Signal, which correlates best with Sea-ice concentration in Baffin Bay. On a Seasonal basis, the Strongest and most Spatially extensive anticorrelations are found in Baffin Bay during the fall, followed by Spring, Summer and winter. These results Support the notion that increased open-water conditions in Baffin Bay during the Stormy Seasons (fall and Spring) promote increased production, transport and deposition of Sea-salt aerosols on Devon Ice Cap. Comparison of ice-core time Series of Eof1, δ18O and melt percentage, with air temperatures recorded in Upernavik, Greenland, Suggests that ice-cover variations in Baffin Bay over the past ∽145 years were dynamically rather than thermodynamically controlled, with periods of Strengthened cyclonic circulation leading to increased open-water conditions, and a greater Sea-salt flux on Devon Ice Cap.

The Kodar mountains in eastern Siberia accommodate 30 small, cold-based glaciers with a combined surface area previously estimated at ~19 km2. Very little is known about these glaciers, which were first surveyed in the late 1950s. In this paper, we use terrestrial photogrammetry to calculate changes in the surface area, elevation, volume and geodetic mass balance of Azarova glacier between 1979 and 2007 and relate these to meteorological data from nearby Chara weather station (1938–2007). The glacier surface area declined by 20±6.9% and the surface lowered by an average of 20±1.8m (mean thinning 0.71 ma–1), resulting in a strongly negative cumulative and average mass balance of –18±1.6mw.e. and –640±60mm w.e. a–1, respectively. The July–August air temperature increased at a rate of 0.036˚Ca–1 between 1979 and 2007, and the 1980–2007 period was on average ~1˚C warmer than 1938–79. In comparison to the 1961–90 period, regional climate projections for the A2 and B2 CO2 emission scenarios developed using the PRECIS regional climate model indicate that summer temperatures will increase by 2.6–4.7˚C and 4.9–6.2˚C, respectively, during the 2071–2100 period. The annual total of solid precipitation will increase by 20% under the B2 scenario but is projected to decline by 3% under the A2 scenario. Azarova glacier exhibits high sensitivity to climatic warming due to its low elevation and exposure to comparatively high summer temperatures. Further summer warming and a decline in solid precipitation projected under the A2 scenario will force Azarova glacier to retreat further, but the impact of an increase in solid precipitation projected under the B2 scenario is more uncertain and requires further investigation before a more conclusive prediction can be made.

We present a 1-D enthalpy-based model of sea ice that allows for quantitative studies of sea ice and its interaction with radiative processes, melt ponds, oceanic heat and salt fluxes, internal density changes and surface heat fluxes on a single computational domain. The model provides new insight into the interior structure and the salinity evolution of sea ice. We compare our model results with measurements from laboratory experiments and show for example that no salt is lost from sea ice by brine expulsion.

Based on presented field data, it is shown that snow contributes roughly 8% to the total mass of ice in the Weddell Sea. Snow depth averages 0.16 m on first-year ice (average thickness 0.75 m) and 0.53 m on second-year ice (average thickness 1.70 m). Due to snow loading, sea ice is depressed below water level and flooded by sea water. As a result of flooding, snow ice forms through congelation of sea water and brine in a matrix of meteoric ice (i.e. snow). Sea-ice growth has been simulated with a one-dimensional model, treating the evolution of salinity, porosity and thermal properties of the ice. Simulations demonstrate that in the presence of a snow cover, ice growth is significantly reduced. Brine volumes increase by a factor of 1.5–2, affecting properties such as ice strength. Snow-ice formation depends on the evolution of freeboard and ice permeability. Effects of accumulation-rate changes have been assessed, for the Weddell Sea with a large-scale sea-ice model accounting for snow-ice formation. Results for different scenarios are presented and compared with field data and one-dimensional simulations. The role of snow in modulating the response of Antarctic sea ice to climate change is discussed.

Stability indices for skier-triggering of slab avalanches are discussed in terms of an adjustment to the skier-induced stress to allow for ski penetration and an adjustment to shear strength (measured with a shear frame) to allow for normal load due to the slab overlying the weak layer. The proposed adjustment to shear strength depends on the microstructure of the weak layer. These adjustments are incorporated into a refinement of the previously established Swiss stability index for skier-triggering. The percentage of correct predictions for the Swiss and refined indices are evaluated using data from 115 weak layers on skier-tested avalanche slopes, 83 of which were classified as persistent weak layers of surface hoar, faceted crystals or depth hoar and 32 as non-persistent weak layers. The refined index reduces the number of incorrectly predicted slab avalanches for the persistent weak layers.

Airborne radar sounding is difficult in South Greenland because of the presence of englacial water, which prevents the signal from reaching the bed. Data coverage remains suboptimal for traditional methods of ice-thickness and bed mapping that rely on geostatistical techniques, such as kriging, because important features are missing. Here we apply two alternative approaches of high-resolution (~300m) ice-thickness mapping, that are based on the conservation of mass, to two regions of South Greenland: (1) Qooqqup Sermia and Kiattuut Sermiat, and (2) Ikertivaq. These two algorithms solve optimization problems, for which the conservation of mass is either enforced as a hard constraint, or as a soft constraint. For the first region, very few measurements are available but there is no gap in ice motion data, whereas for Ikertivaq, more ice-thickness measurements are available, but there are gaps in ice motion data. We show that mass-conservation algorithms can be used as validation tools for radar sounding. We also show that it is preferable to apply mass conservation as a hard constraint, rather than a soft constraint, as it better preserves elongated features, such as glacial valleys and ridges.

To study the past and future evolution of Rhonegletscher, Switzerland, a flowline model was developed to include valley shape effects more accurately than conventional flowband models. In the model, the ice flux at a gridpoint was computed by a two-dimensional ice-flow model applied to the valley cross-section. The results suggested the underestimation of the accumulation area, which seems to be a general problem of flowline modelling arising from the model’s one-dimensional nature. The corrected mass balance was coupled with the equilibrium-line altitude (ELA) change, which was reconstructed for the period 1878–2003 from temperature and precipitation records, to run the model for the past 125 years. The model satisfactorily reproduced both changes in the terminus position and the total ice volume derived from digital elevation models of the surface obtained by analyses of old maps and aerial photographs. This showed the model’s potential to simulate glacier evolution when an accurate mass balance could be determined. The future evolution of Rhonegletscher was evaluated with three mass-balance conditions: the mean for the period 1994–2003, and the most negative (2003) and positive (1978) mass-balance values for the past 50 years. The model predicted volume changes of –18%, –58% and +38% after 50 years for the three conditions, respectively.

The Canadian Lake Ice Model (CLIMo) is used to simulate the effects of climate variability and change on lake ice phenology (freeze-up (FU), break-up (BU), ice-cover duration) and total thickness and composition (snow ice, congelation ice) in central Alaska, USA. The model results suggest that, due to the Pacific Decadal Oscillation shift that occurred in 1976, the ice-cover duration is shorter (4 days) due to earlier BU in spring, and thinner (0.05 m) due to a reduction in the formation of snow ice. Sensitivity tests indicate that air-temperature changes cause the duration change, and snow-depth changes cause the total ice-thickness and composition change. The role of annual and monthly air-temperature and snow-depth changes is examined further in a series of experiments designed to elucidate the possible effects of future climate change. Air temperature is varied in 1˚C increments between –4 and +4˚C, and snow depth is varied in 25% increments between –100% and +100% of the long-term averages for 1952–75 and 1977–2000. The FU and BU dates (ice duration) are most affected by annual air-temperature change. Total ice thickness and composition are most affected by annual and monthly snow-depth change. A key finding is that snow-depth increases cause total ice thickness to increase as a consequence of increased snow-ice formation on top of the ice cover at the expense of congelation-ice formation at the bottom of the ice cover.

A two-dimensional surface mass-balance model is coupled to a three-dimensional higher-order ice flow model to assess the imbalance between climate and glacier geometry for the Morteratsch (Engadine, Switzerland) glacier complex. The climate–geometry imbalance has never been larger than at present, indicating that the temperature increase is faster than the geometry is able to adapt to. We derive response times from transient and steady-state geometries and find that the volume response time is correlated to the magnitude of the mass-balance forcing. It varies between 22 and 43 years, while the length response time is between 47 and 55 years. Subsequently, the modelled response times are compared with different analytical methods from the literature. The effect of a climatic perturbation on the response time, which produces a spatially distributed mass-balance forcing, is also examined. We investigate the effect of glacier size on the response time and project that the response time will decrease in the future due to a surface steepening. Finally, volume–area scaling methods with different parameters are tested and an alternative method is proposed that takes into account the surface slope. The effect of a transient state on the method is also evaluated.

We identified ikaite crystals (CaCO3·6H2O) and examined their shape and size distribution in first-year Arctic pack ice, overlying snow and slush layers during the spring melt onset north of Svalbard. Additional measurements of total alkalinity (TA) were made for melted snow and sea-ice samples. Ikaite crystals were mainly found in the bottom of the snowpack, in slush and the surface layers of the sea ice where the temperature was generally lower and salinity higher than in the ice below. Image analysis showed that ikaite crystals were characterized by a roughly elliptical shape and a maximum caliper diameter of 201.0±115.9 μm (n = 918). Since the ice-melting season had already started, ikaite crystals may already have begun to dissolve, which might explain the lack of a relationship between ikaite crystal size and sea-ice parameters (temperature, salinity, and thickness of snow and ice). Comparisons of salinity and TA profiles for melted ice samples suggest that the precipitation/dissolution of ikaite crystals occurred at the top of the sea ice and the bottom of the snowpack during ice formation/melting processes.

High-resolution (>10 samples a−1) glaciochemical analyses covering the last 110 years from a Siplc Dome, Antarctica, ire core reveal limited migration of certain soluble ionic species (methane sulfonic acid, NO3− and Mg2+). The observed chemical migration may be due in part to seasonal alternation between less acidic winter (from high sea-salt concentrations) and more acidic summer (from high marine biogenic acid concentrations) layers, common at coastal siles such as Siplc Dome. Exact mechanisms to expla in the migration are unclear, although simple diffusion and gravitational movement are unlikely since new peaks are formed where none previously existed in each case. Initial migration of each species is both shallower and earlier at Siple Dome than at other sites in Antarctica where similar phenomena have been observed, which may be related to the relatively low accumulation rate at Siple Dome (~13.3 cm ice a−1). Migration appears to be limited to either the preceding or following seasonal layer for each species, suggesting that paleoclimatic interpretations based on dala with lower than annual resolution are not likely to be affected.

The disintegration of Larsen A and B ice shelves in 1995 and 2002, respectively, was preceded by intense surface melting during the summer of ice-shelf collapse and previous summers. To understand the transition of the ice-shelf surface from dry to wet conditions, we developed a one-dimensional model, describing the mass, heat and force balances of water and firn within the ice-shelf surface layer. The model is run using atmospheric data from an automatic weather station on Larsen C ice shelf (World Meteorological Organization station ‘Larsen Ice Site’) located south of Larsen A and B. The model’s derived melting rate is greater than melting predicted by the positive degree-day (PDD) approach, common in studies of ablating ice sheets, such as Greenland. The model shows that the years of ice-shelf break-up (1995 and 2002) are distinguished from previous years by local maxima in the number of melting days. When the PDD approach is considered, however, a maximum in the number of positive degree-days appears in the 2002 break-up year, but not in 1995.

Passive microwave remote-sensing imagery has proven to be a useful Source for Sea-ICE motions because of its all-sky capabilities. However, the low Spatial resolution of the passive microwave Sensors has not allowed the retrieval of Small-scale motion details Such as lead and ridge formation. The NAsA Earth Observing System Advanced Microwave Scanning Radiometer (AMSR-E) has more than double the Spatial resolution of previous passive microwave Sensors, allowing it to track the formation of moderate-sized leads and yield much more detailed and more accurate ICE-motion estimates. Comparisons with buoys indicate that AMSR-E motions have errors >30% lower than ICE motions derived from the previous passive microwave Sensors. While AMSR-E Still cannot retrieve the Same level of detail as Synthetic aperture radars or visible/infrared Sensors, AMSR-E’s complete coverage can better capture the ephemeral motions of the Sea-ICE cover on daily, and potentially Sub-daily, timescales.

The bacterial DNA structures at different depths in the Puruogangri (Tibetan Plateau) ice core (83.45m) were investigated by the denaturing gradient gel electrophoresis (DGGE) DNA fingerprinting technique. DGGE profiles indicated that the bacterial species diversity in glacial ice is high, and indigenous species represented by common bands in all samples may grow on the glacial surface. Bacterial diversity, as estimated by Shannon indices (mean 2.91; SD 0.25; n = 13), was comparable to that of soil habitats and had a positive correlation with Ca2+ concentration (R = 0.71; P< 0.01), a good proxy of dust. This suggested that the soil ecosystem was the main source of bacteria in this glacier. The low similarity indices (0–43%) were found between the ice-core samples, which corresponded to the episodic deposition under defined climatic conditions and low activity of microorganisms in glacial ice. The profiles of bacterial species composition in glacial ice may be a bio-indicator of climatic changes or dating.

High resolution (TIMS) U-series dating of sea-level events obtained from coral-reef complexes suggests that global deglaciation from the Saale (penultimate) glacial to the Eem Interglacial (marine δ18O stages 6/5) may have occurred earlier in relation to Milankovitch insolation forcing than that from the Wisconsinan glacial to the Holocene Interglacial (marine δ18O stages 2/1). However, the interpretation of these data has been problematic because of the possibility of isotope exchange. In order to investigate whether these different lead—lag relations between Milankovitch forcing and ice volume are feasible from the point of view of large-scale ice-sheet dynamics and thermodynamics, the three-dimensional polythermal ice-sheet model SICOPOLIS (Simulation Code for Poly- thermal Ice Sheets) is applied to the entire Northern Hemisphere (which gives the major contribution to global ice-volume changes due to the relative stability of the Antarctic ice sheet) and simulations through the last two climatic cycles are conducted. The simulations cover the interval from 250 kyr BP until today and are driven by surface-temperature reconstructions of deep ice cores (GRIP, Vostok) and simple parameterizations for the change of precipitation with time. Discussion of the results is focused on the Saale/Eem and the Wisconsinan/Holocene transitions. The amount and rate of deglaciation are in good agreement with the SPECMAP record for both cases, and the evidence of the data for an early start of the Eem Interglacial is supported.

We use remote-sensing and GIS technologies to monitor glacier changes in the Koshi River basin, central Himalaya. The results indicate that in 2009 there were 2061 glaciers in this region, with a total area of 3225 ±90.3 km2. This glacier population is divided into 1290 glaciers, with a total area of 1961 ±54.9 km2, on the north side of the Himalaya (NSH), and 771 glaciers, with a total area of 1264 ± 35.4 km2, on the south side of the Himalaya (SSH). From 1976 to 2009, glacier area in the basin decreased by about 19±5.6% (0.59±0.17%a–1). Glacier reduction was slightly faster on SSH (20.3 ±5.6%) than on NSH (18.8±5.6%). The maximum contribution to glacier area loss came from glaciers within the 1-5 km2 area interval, which accounted for 32% of total area loss between 1976 and 2009. The number of glaciers in the Koshi River catchment decreased by 145 between 1976 and 2009. Glacier area on SSH decreased at a rate of 6.2 ±3.2% (0.68 ±0.36% a–1), faster than on NSH, where the rate was 2.5 ±3.2% (0.27±0.36% a–1) during 2000-09. Based on records from Tingri weather station, we infer that temperature increase and precipitation decrease were the main causes of glacier thinning and retreat during the 1976-2000 period. Glacier retreat during the 2000-09 period appears to be controlled by temperature increase, since precipitation increase over this period did not offset ice losses to surface melting.

Formation of supercooled water and frazil ice was studied in the Chukchi Sea coastal polynya off Barrow, Alaska, USA, in winter 2009/10, using moored salinity/temperature sensors and Ice Profiling Sonar (IPS) data along with satellite data. Oceanographic data from two moorings revealed episodic events of potential supercooling at 30–40m depth, including the possibility of in situ supercooling, while the polynya was open. We identified frazil ice-like signals in the IPS data down to 5–15 m depth, associated with large heat loss and windy, turbulent conditions in an active polynya. This likely represents the first IPS observation of frazil ice in the marine environment. On the day of the maximum signal of frazil ice, spaceborne synthetic aperture radar shows streaks of high backscatter within the polynya, indicating active frazil ice formation just downwind of the mooring sites. In addition, the longer-term potential supercooling that persisted for 1–3 weeks occurred twice despite the absence of polynya activity at the mooring sites. These events occurred during periods dominated by the northeastward current. A series of coastal polynyas had formed southwest of the mooring sites prior to these events. Thus, the water masses with potential supercooling were likely advected from these polynyas.

Sea ice on the large scale is characterized by leads and ridges that typically have a given orientation. Because of various flaws, we would expect that the ice will form oriented leads and ice-thickness characteristics that control the heat and moisture fluxes into the atmosphere. Prediction of these oriented leads, ridges and slip lines is relevant to understanding the role of ice mechanics in global climate change as they can play a significant role in the ice-thickness distribution.

In this paper we develop a model for the dynamical treatment of leads and oriented flaws in large-scale sea-ice models. Two particular isotropic realizations of this model relevant to climate studies are examined: (a) an isotropic composite with oriented leads in all directions imbedded in thick ice, and (b) a simple "strain hardening" isotropic model where only oriented leads having the potential to open rapidly are allowed. Under applied stress both models yield preferential deformation along a symmetric pair of intersecting leads or ridges with the intersection angles dependent on the confinement stress. The "uniform-orientation" model results in a yield curve that approximates a sine lens, while the "strain hardening" model has a teardrop-like yield curve. How the resulting fracture-based yield curves and non-normal flow rules may be cast in a form usable in numerical investigations of climate is discussed.

This paper describes a new triaxial testing apparatus designed to determine the creep (viscoelastic) behavior of snow. The device is deformation-controlled and can apply strain rates between 10–7 s–1 and 10–2s–1 in tension and compression. The sample volume change is determined by measuring the displaced pore-air volume. During winters 1997/98 and 1998/99, >100 compression and tension tests were carried out. It is shown that snow is a highly non-linear but ideal viscoelastic material with a strong strain-rate dependency. A selection of test results is provided. We show how snow viscosity varies with density and strain rate. In a final analysis we interpret our results with respect to snow microstructure in order to develop microstructure-based constitutive relations which can be implemented in finite-element programs. Our results clearly show that for snow densities and strain rates tested, straining of the grain bonds is the primary mechanism of deformation within the snow ice lattice.