A survey of icebergs using satellite radar images has been made in the seasonal sea-ice zone of East Antarctica in the .sector between longitudes 50° and 145° E. These data provide information on the spatial distribution and size statistics of icebergs near the coast in areas not often visited by shipboard observers, and close to their sources at ice shelves and glacier tongues. The icebergs are detected and their dimensions extracted by analysis of the texture properties present in satellite images acquired with ERS-1 synthetic aperture radar during the austral winter. The minimum size of iceberg reliably detected and measured is 0.06 km2.

A significant variation, by up to a factor of two, is found in the area of icebergs close to different sections of the coast, which suggests a characteristic size for different sources. The average value of the length-to-width ratio for icebergs in the whole population shows some variability with size. The probability of finding icebergs is greatest close to the coast, decreasing in general with distance from the coast, such that few icebergs were detected more than 160 km from the coast. in one sector about 85° E, icebergs are found to at least 550 km from the coast, which is consistent with the transport of icebergs northwards in this region by a branch of the westward-heading near-coastal current (East Wind Drift) which connects with the southern margins of the eastward-heading Antarctic Circumpolar Current.

The dataset of Northern Hemisphere EASE-Grid Weekly Snow Cover and Sea Ice Extent for the period October 1966-July 2001 is analyzed to examine the height dependence of declining tendencies of seasonal snow cover in the Himalaya and the Tibetan Plateau region (25−45˚ N, 70−110˚E). It is found that the annual mean snow-covered area is decreasing in the Himalaya/Tibet region at a rate of ∼ 1 % a−1, implying that the mean snow-covered area has decreased by one-third from 1966 to 2001. The rate of decrease is largest (1.6%) at the lowest elevations (0−500 m). On the other hand, the length of the snow-cover season is declining at all elevations, with the greatest rate of decline in the 4000−6000 m height range. On the Tibetan Plateau (∼4000−6000 m a.s.l.), the length of the snow-cover season has decreased by 23 days, and the end date for snow cover has advanced by 41 days over this 35 year period. These rates might be somewhat overestimated by the binary definition of snow cover on satellite images. It is likely that the reduction of the snow surface albedo by deposition of Asian dust and anthropogenic aerosols may be at least partly responsible for earlier snowmelt.

We have reconstructed the ice thickness distribution of the Morteratsch glacier complex, Switzerland, and used this to simulate its flow with a higher-order 3-D model. Ice thickness was measured along transects with a ground-penetrating radar and further extended over the entire glacier using the plastic flow assumption and a distance-weighted interpolation technique. We find a maximum ice thickness of 350 ±52.5 m for the central trunk of Vadret da Morteratsch, resulting from a bedrock overdeepening. The average thickness of the glacier complex is 72.2 ±18.0 m, which corresponds to a total ice volume of 1.14 ± 0.28 km3. The flow of the glacier is modelled by tuning the rate factor and the sliding parameters taking into account higher-order terms in the force balance. The observed velocities can be reproduced closely (root-mean-square error of 15.0 m a-1, R2 = 0.93) by adopting a sliding factor of 12 x 10–16 m7 N–3 a-1 and a rate factor of 1.6 x 10-16 Pa-3 a-1 . In this setting, ice deformation accounts for 70% of the surface velocity and basal sliding for the remaining 30%. The modelled velocity field reaches values up to 125 ma-1, but also indicates an almost stagnant front and confluence area, which are crucial for understanding the ongoing glacier retreat.

Liligo Glacier is a small glacier located in a transverse valley, which flows on the south side of Baltoro Glacier, Karakoram, Pakistan. Terminus variations of Liligo Glacier since 1892 were reconstructed using various methods and sources (historical documents, cartography, photographs, satellite images and field surveys). The glacier is characterized by two phases of strong advance (beginning and end of the 20th century), separated by at least half a century of retreat. The advance rates, together with some ice-surface features such as the heavily crevassed surface and terminus morphology, are considered to be indicative of a surge-type glacier.

Between 1999 and 2001, a 724 m long ice core was drilled on Akademii Nauk, the largest glacier on Severnaya Zemlya, Russian Arctic. The drilling site is located near the summit. The core is characterized by high melt-layer content. The melt layers are caused by melting and even by rain during the summer. We present high-resolution data of density, electrical conductivity (dielectrical profiling), stable water isotopes and melt-layer content for the upper 136m (120 m w.e.) of the ice core. The dating by isotopic cycles and electrical conductivity peak identification suggests that this core section covers approximately the past 275 years. Singularities of volcanogenic and anthropogenic origin provide well-defined additional time markers. Long-term temperatures inferred from 12 year running mean averages of δ18O reach their lowest level in the entire record around 1790. Thereafter the δ18O values indicate a continuously increasing mean temperature on the Akademii Nauk ice cap until 1935, interrupted only by minor cooling episodes. The 20th century is found to be the warmest period in this record.

Glacier monitoring enables us to detect influences of global warming in high mountain regions. To initiate the establishment of a glacier-monitoring network in northern Eurasia, we studied recent glacier variations in Mongolia using topographical maps, aerial photographs and satellite images (Corona and Landsat). Glaciers in Mongolia exist in the Altai mountains which span approximately 1400 km within Russia, China and Mongolia. Four regions were selected to form the study area: Tavan Bogd region, Turgen massif, Kharkhiraa massif and Tsambagarav massif. During the period from the 1940s to 2000 or from 1968 to 2000, the glaciers in these regions lost 10.2%, 19.3%, 28.0% and 28.8% of their area respectively. The glaciers in the Tavan Bogd, Kharkhiraa and Turgen regions were found to have been almost stationary since 1987/88, while those in Tsambagarav massif showed no significant change in area since 1963. Shrinkage of the glaciers occurred between 1945/68 and 1987/88 in the former regions and between 1948 and 1963 in the latter. Mongolian glaciers seem to behave differently from other glaciers which have been experiencing steady shrinkage recently.

Large variations in both snow water equivalent (SWE) and snow slope stability are known to exist in the alpine snowpack, caused by wind, topographic and microclimatic effects. This variability makes extrapolation of point measurements of snowpack properties difficult and prone to error, but these types of measurements are used to estimate SWE and stability across entire mountain ranges. Radar technology provides a promising alternative to point measurements, because large areas can be covered quickly and non-intrusively. There is great potential for obtaining information on a large spatial scale from airborne applications. Frequency-modulated continuous wave (FMCW) radar measurements were made from the ground in several different alpine snowpacks, along with manual and in situ electrical measurements. The surface and ground reflections from the radar data, combined with an average density estimate, can provide a useful estimate of SWE. In addition, the locations of internal reflections are highly correlated with both visually identified layers and measured changes in in situ dielectric properties.

Repeat photographs and field survey reveal the mechanism of short-term ice-cliff evolution at Maud Glacier, a temperate lake-calving glacier in New Zealand. Calving is cyclic, each cycle involving four stages: (1) waterline melting and collapse of the roof of a sub-horizontal notch at the cliff foot; (2) calving of ice flakes from the cliff face leading to a growing overhang from the waterline upwards, and crack propagation from the glacier surface; (3) large but infrequent calving of slabs in response to the developing overhang, returning the cliff to an “initial” vertical profile; (4) rare subaqueous calving ofa submerged ice foot. Results indicate that the rate-controlling process is the speed of waterline melting, and that calving rate is independent of water depth (at least at time-scales of weeks to months). Slowly calving lake-terminating glaciers have mass balances more negative than land-terminating glaciers, but nevertheless advance and retreat in response to mass-balance driven changes in ice velocity.

Finsterwalderbreen (77°26’ N, 15° 15’ E) is a 35 km2 polythermal, surge-type glacier in southern Spitsbergen, Svalbard. Extensive field investigations have been carried out on the glacier, including mapping of bed topography by radio-echo soundings, mass-balance measurements and hydrological and meteorological registrations. In this paper we have used surface and bed topography and observations of summer ablation to estimate total runoff and subglacial drainage pattern by means of spatial map analysis in standard geographic information system software. The location and relative importance of the water-channel outlets from the glacier were estimated, as well as the change in drainage pattern over the period 1970–90. The results could be compared to direct observations of drainage pattern and discharge recordings. The analyses indicate that the location of the subglacial channels is dominated by the surface topography and thus that the channels are partly pressurized.

Sea-ice hazard causes serious harm to aquaculture, marine navigation, offshore oil production and other activities in the Bohai Sea, China. To study the spatial distribution characteristics of sea-ice-hazard risk in Bohai is therefore desirable. The thickness and area of sea ice in the Bohai Sea during the winters (December–March) of 1987–2011 were estimated using data from the NOAA (US National Oceanic and Atmospheric Administration) satellite. The sea-ice thickness was converted into a sea-ice-hazard index after defining this index, and the different sea-ice-hazard risk grades were classified. The occurrence probability of sea-ice hazard was also calculated using fuzzy risk theory, and the spatial distribution characteristics of sea-ice-hazard risk in the Bohai Sea were studied. The results show that the sea-ice-hazard risk for offshore aquaculture decreased as the offshore distance increased. All the oilfields in Liaodong Bay are influenced by sea-ice hazard, two of the fields in Bohai Bay are slightly affected and the remaining fields are not influenced. The risk for marine navigation is related to the location of the port and the distance from the port. The risk in the port area is the highest; it is reduced by more than 30% at distances 10 km away from the port.

Since the beginning of the 1900s, the polythermal valley glacier midre Lovénbreen (area 5 km2) in northwestern Svalbard has retreated approximately 1km. The glacier has not surged for at least 110 years, and the present smooth longitudinal profile and negative mass balance suggest that it is not currently building up to a surge. Based on limited evidence, it has often been assumed that midre Lovénbreen surged around 1880. The ongoing retreat is probably due to quiescent-phase stagnation amplified by 20th-century climate change, as is the case for several other glaciers in Svalbard. Recently, small eskers have been found in the glacier forefield. Based on their geomorphological appearance, these are interpreted as concertina eskers, and they add to the dynamic history of the glacier. Midre Lovénbreen is interpreted as an example of a change from surge-type to non-surge-type glacier behaviour.

The NEMO numerical model of drifting snow, whose general outlines are presented in this paper, is based on a physical model for saltation and turbulent diffusion. The model needs a set of input parameters including fall velocity, threshold shear velocity, shear velocity, mass concentration and roughness, which are obtained from empirical formulae and wind speed measured at a given height. To better determine the required field data in an alpine context, our experimental site, Col du Lac Blanc (2700ma.s.l.), French Alps, was first equipped with one anemometer and blowing-snow acoustic sensors, which proved not to be accurate enough for research purposes in the current state of development even though a new calibration curve was used. We therefore set up a Snow Particle Counter and we returned to the traditional, robust mechanical traps and a 10 m mast with six anemometers, two temperature sensors and a depth sensor to better determine friction velocity and aerodynamic roughness. Based on the studied drifting-snow events we conclude: (1) the proportionality of the aerodynamic roughness to the square of the friction velocity was confirmed, but with a varying proportionality ratio depending on the snowdrift event; (2) values of σsUF were relatively well approximated by empirical formulae from data originating from Antarctica, and (3) snowdrift concentration profiles obtained by Pomeroy’s semi-empirical formulae for the saltation layer coupled with a theoretical approach for the diffusion layer overestimated the concentration profiles for the studied blowing-snow event.

We outline how to incorporate microscale effects of polycrystalline ice into a continuum description. Actually, analyses of ice cores in Antarctica show that different microstructures generally produce different responses, i.e. a non-uniform distribution of c axes gives rise to anisotropic behaviour. It has been recognized that, to describe certain microstructural processes, like recrystallization or polygonization, we need a parameter able to switch them on (e.g. dislocation density or its associated lattice distortion energy). With this in mind, balance equations for a continuum theory of an anisotropic ice sheet undergoing recrystallization have been recently proposed. In this work, we examine relations for some constitutive quantities, in order to take into account the effects of grain-boundary migration, nucleation and polygonization. We check our assumptions by explicit comparison with the first 1200 m of the Byrd (Antarctica) ice core. Current literature usually gives a relation between normal grain growth and grain boundary migration rate. Here, an equation for normal grain growth which also incorporates the influence of polygonization is suggested. It is based on experimental data from the same core in Antarctica. Polygonization is a microscopic process, but here we present a continuum description of the bending stresses which promote the fragmentation of crystallites in terms of the theory of mixtures with continuous diversity.

Observational and experimental evidence suggests that it is important to explicitly account for the fluidized flow regime in avalanche hazard mapping due to its high mobility, intermediate density and high velocity. We explore the differences from conventional runout modelling by implementing an extension of the Norem–Irgens–Schieldrop (NIS) rheology in a simple mass-point model. When the dispersive stresses and the excess pore pressure equal the overburden pressure, the flow height increases and the density diminishes until a new equilibrium is reached, determined by the different density dependencies of the two parameters of the dispersive stresses. Fluidization requires sufficiently steep terrain; when it occurs it leads to substantially higher velocities than compared to the dense-flow regime. The model parameters are strongly constrained by their physical meaning and vary little between widely different avalanches. However, in all test cases we obtained better agreement between simulated and observed runout distances and pressure effects than with conventional models.

Hubbard Glacier is the largest tidewater glacier in North America. In contrast to most glaciers in Alaska and northwestern Canada, Hubbard Glacier thickened and advanced during the 20th century. This a typical behavior is an important example of how insensitive to climate a glacier can become during parts of the calving glacier cycle. As this glacier continues to advance, it will close the seaward entrance to 50 km long Russell Fjord and create a glacier-dammed, brackish-water lake. This paper describes measured changes in ice thickness, ice speed, terminus advance and fjord bathymetry of Hubbard Glacier, as determined from airborne laser altimetry, aerial photogrammetry, satellite imagery and bathymetric measurements.The data show that the lower regions of the glacier have thickened by as much as 83 m in the last 41 years, while the entire glacier increased in volume by 14.1 km 3. Ice speeds are generally decreasing near the calving face from a high of 16.5 md −1in1948 to11.5 md −1in 2001. The calving terminus advanced at an average rate of about 16 m a−1 between 1895 and 1948 and accelerated to 32 m a−1 since 1948. However, since 1986, the advance of the part of the terminus in Disenchantment Bay has slowed to 28 m a−1. Bathymetric data from the lee slope of the submarine terminal moraine show that between 1978 and 1999 the moraine advanced at an average rate of 32 m a−1, which is the same as that of the calving face.

Wind effects on snow distribution and increasing avalanche hazard are well known. Forecasting such phenomena is based on empirical rules and experience. For two years, the CEN has tested a new analysis program for forecasting blowing-snow events at an Alpine site. The aim is to improve avalanche-forecasting tools so as to increase the accuracy of avalanche-hazard forecasts. Our understanding of blowing-snow mechanisms began with observations and field measurements at a high altitude site during periods of strong wind. Using an empirical approach, snow-grain morphology, cohesion between snow particles and grain-size have been combined to define a function for the calculation of a “driftabilily index”. By comparing this index with the wind thresholds observed in field, a snowdrifting index has been defined. Snow profiles calculated by SAFRAN (estimation of relevant meteorological parameters for snow models) and Crocus (snowpack-evolution model) were analysed using an application called PROTÉON. Forecasts of wind velocity and snow profiles have been used to discriminate between periods with or without snow transport. For the subsequent 24 hours and for each snow layer, the value of this snowdrifting index is calculated and displayed on a graph. Validation consists of a comparison of forecasted blowing-snow periods with the field observations and measurements at a pass situated at 2700 m a.s.l. Meteorological and snow-parameter data are available at this site.

Sortebræ, a large tidewater-terminating glacier in East Greenland, underwent a major surge between 1992 and 1995 during which the glacier terminus advanced by nearly 10 km. In this paper, intensity tracking, interferometry and visual interpretation have been used to characterize the ice dynamics during the surge from satellite synthetic aperture radar images. The surge had a rapid initiation that saw velocities increase by 60–1500 times, and within 13 months the entire lower 53 km of the glacier was affected. Surge termination occurred very rapidly during summer, and ice velocity dropped from around 20 md–1 to around 2 md–1 in only 3 months. Uniquely, part of the upper glacier remained fast-flowing even after the main surge event had terminated. Ice dynamics together with observations of large turbid lakes at the glacier margins suggest that the surge resulted from a throttling of basal water by a switch in the hydrological system.

In 1997, three ice cores were recovered from Dasuopu glacier on the northern slope of the central Himalaya. the first core, 159.9 m long, was drilled at 7000ma.s.l. down the flowline from the top of the col. the second core, 149.2m long, was drilled on the col at 7200ma.s.l. the third core, 167.7 m long, was also drilled on the col at 7200ma.s.l., 100 maway from the second core. the present paper discusses the δ18O and methane results reconstructed for the past 1000 years based on the second core. the δ18O can be interpreted as an air-temperature signal. the methane concentration is mainly representative of atmospheric methane concentration. Both δ18O and methane records show an obvious increasing trend in the past 1000 years. Methane concentration in the record is similar to the fluctuations of δ18O, decreasing during cold periods and increasing during warm periods. the Little Ice Age was well recorded in the core by both δ18O and methane. the coldest period appeared in the late 18th century, accompanied by a decrease in methane concentration. the abrupt methane-concentration increase starting after the 18th century is no doubt due to anthropogenic input. the observed methane-concentration decrease during World Wars I and II clearly demonstrates the importance of the anthropogenic input to atmospheric methane concentration if further measurements prove that it is a true atmospheric signal.

We present a detailed analysis of the microstructure in the shallow part (100–580m) of the European Project for Ice Coring in Antarctica (EPICA) ice core at Dome Concordia. In the Holocene ice, the average grain-size increases with depth. This is the normal grain-growth process driven by a reduction of the total grain-boundary energy. Deeper, associated with the Holocene–Last Glacial Maximum (LGM) climatic transition, a sharp decrease of the average grain-size is observed. to explain modifications to the microstructure with climatic change, we discuss the role of soluble and insoluble (microparticles) impurities in the grain-growth process of Antarctic ice, coupled with an analysis of the pinning of grain boundaries by microparticles. Our data indicate that high soluble impurity content does not necessarily imply a slowing-down of grain-growth kinetics, whereas the pinning of grain boundaries by dust particles located along the boundaries does explain modifications to the microstructure (small grain-sizes; change in grain-size distributions, etc.) observed in volcanic ash layers or dusty LGM ice.Moreover, classical mean-field models of grain-boundary pinning are in good quantitative agreement with the evolution of grain-size along the EPICA ice core. This suggests a major role for dust in the modification of shallow polar ice microstructure.

In 2010 a reflection seismic survey was carried out on the Alpine glacier Colle Gnifetti. The processed and depth-converted data could be compared to a nearby ice core, drilled almost to the bed. Comparisons showed that the depth of the P-wave bed reflection was too shallow, while the depth of the SH-wave bed reflection fitted the ice-core length well. We are now able to explain the major part of these differences using the existing crystal orientations of the ice at Colle Gnifetti. We calculate anisotropic velocities for P- and SH-waves that are usually picked for stacking and compare them with zero-offset velocities needed for the depth conversion. Here we take the firn pack at Colle Gnifetti into account for P- and S-wave analysis. To incorporate the S-wave analysis we first derive a new equation for the relationship between density and S-wave velocity from diving waves. We show that anisotropic fabrics observed at Colle Gnifetti introduce a difference of only 1% between stacking and depth-conversion velocities for the SH-wave, but 7% for the P-wave. We suggest that this difference in stacking and depth-conversion velocity for the P-wave can be used to derive information about the existing anisotropy by combining our seismic data with, for example, radar data.