Conventional and reference-surface mass-balance data from Gulkana and Wolverine Glaciers, Alaska, USA, are used to address the questions of how rapidly these glaciers are adjusting (or ‘responding’) to climate, whether their responses are stable, and whether the glaciers are likely to survive in today’s climate. Instability means that a glacier will eventually vanish, or at least become greatly reduced in volume, if the climate stabilizes at its present state. A simple non-linear theory of response is presented for the analysis. The response of Gulkana Glacier is characterized by a timescale of several decades, but its stability and therefore its survival in today’s climate are uncertain. Wolverine seems to be responding to climate more slowly, on the timescale of one to several centuries. Its stability is also uncertain, but a slower response time would make it more susceptible to climate changes.

The ice-core logging procedure used to log the North Greenland Icecore Project (NorthGRIP) ice cores is described. the existence of two deep ice cores, NorthGRIP 1and 2, drilled 25 mapart, allows an independent evaluation of the procedure. the logged depths of the NorthGRIP 1 and 2 cores deviate from the length of the unwound drill cable corrected for elongation of the cable when hanging in the hole, by 1.5‰ and 50.5‰ at depths of 1371 and 2931 m, respectively. Differences between logged depths of identified layers found in both cores are studied in the depth interval where they overlap. Layers are identified by electrical conductivity measurements and dielectric profiling. the difference between the logged depths of layers identified in both cores increases to 0.5 m close to the bottom of the NorthGRIP 1 core, which is <0.5 mm m–1 ice core. the comparison between the two cores shows that the NorthGRIP logging procedure is accurate and reproducible. Further, our results show that the temperature conditions and handling of the core during logging are important for obtaining a precise depth.

A new bedrock map of the Dome C area is presented, based on all radar data collected during Italian Antarctic Expeditions in 1995, 1997, 1999 and 2001. The map clearly distinguishes the Dome C plateau, along with valleys and ridges. The plateau develops at three different altimetric levels, and its morphology is characterized by hills and closed depressions. There are no visible features which can be ascribed to glacial erosion or deposition. The major valley is 15 km wide and 500 m deep; its axis is parallel to that of other valleys and ridges in the plateau. The valley bottom is not flat, but contains a saddle at its centre. The morphology of the major valley may be considered a relict one which was not modified by the overlying ice cap. Two large ridges, characterized by hills, saddles and depressions, lie near the boundaries of the area. The map is used to recalculate ice thickness below the European Project for Ice Coring in Antarctica (EPICA) borehole. The new thickness is 3300 m, 50m greater than before, implying that the expected palaeoclimate record from the ice core could extend back >800 kyr.

We use daily surface velocities measured over several weeks in 2007 and 2008 on a slowly surging glacier in Yukon, Canada, to examine the ordinary melt-season dynamics in the context of the ongoing surge. Horizontal velocities within and just below the ~1.5 km-long zone of fastest flow, where the surge is occurring, are often correlated during intervals of low melt. This correlation breaks down during melt events, with the lower reaches of the fast-flow zone responding first. Velocity variability in this lower reach is most highly correlated with melt; velocities above and below appear to respond at least as strongly to the velocity variations of this reach as to local melt. GPS height records are suggestive of ice/bed separation occurring in the fast-flow zone but not below it, pointing to a hydrological cause for the short-term flow variability in the surging region. Independent velocity measurements over 6 years show a maximum July flow anomaly coincident with the location most responsive to melt. Results from a simple model of dashpots and frictional elements lend support to the hypothesis that this zone partly drives the dynamics of the ice above and below it. We speculate that the slow surge may enhance glacier sensitivity to melt-season processes, including short-term summer sliding events.

Measurements of trace elements in snow and ice are frequently used to describe past atmospheric composition although there is no firm basis for assuming a direct connection. Trace-element concentrations have been measured on samples of aerosol and freshly fallen snow collected simultaneously from two sites in the Antarctic Peninsula during summer. Following improvements in contamination control, the reported concentrations and crustal enrichment factors of Cd, Cu, Pb and Zn in the aerosol are lower than any values previously reported from Antarctica. Even tighter controls will be required in the future.

For a crustal element (A1) and for the marine cations (Na, Ca and K) a consistent ratio (0.48±0.31) for the concentration in air (pg m−3)/concentration in snow (pg g−1) is obtained for simultaneously collected samples. This supports a simple model of aerosol scavenging proposed by Junge which considers aerosol removal over polar ice sheets to be dominated by in-cloud processes. Averaged data for Cd, Cu, Pb and Zn from samples collected at different times appear to behave similarly. These findings suggest that there is no preferential scavenging by snowfall of either crustal or heavy metal components in contemporary aerosol. If proved more general in Antarctica this may help to simplify the interpretation of time series data from ice cores.

Isolated areas of high basal drag, or ‘sticky spots’, are important and poorly understood features in the force balance and dynamics of West Antarctic ice streams. Characterizing sticky spots formed by thin or drying subglacial till using ice-penetrating radar is theoretically possible, as high radar bed-returned power (BRP) is commonly related to an abundance of free water at the ice/bed interface, provided losses from englacial attenuation can be estimated. In this study we use airborne radar data collected over Evans Ice Stream to extract BRP profiles and test the sensitivity of BRP to the adopted englacial attenuation correction. We analyse 11 ~ 2 0 km profiles in four fast-flow areas where sticky spots have been inferred to exist on the basis of model and surface data inversions. In the majority of profiles we note that the increase in basal drag is accompanied by a decrease in BRP and suggest that this is evidence both for the presence of a sticky spot in those locations and that local variations in subglacial hydrology are responsible for their existence. A comparison is made between empirical and numerical modelling approaches for deriving englacial attenuation, and our findings generally support previous studies that advocate a modelling approach.

Sea-ice fluctuations in the Sea of Okhotsk and the Bering Sea during the winters of 1992−99 were investigated by using the Special Sensor Microwave/ Imager dataset and a new ice-property retrieval algorithm This algorithm can distinguish between ice types such as fast ice floes, young ice and new ice, in an area covered by concentrations of >80% ice, and also has improved display resolution because it uses one of the 85 GHz channels. The ice thicknesses derived from the ice-thickness parameter of the new algorithm were compared with ship-based ice-thickness measurements, and were assumed to be 1−10, 11−34, 35−85 and 86−120 cm for new ice, young ice, floes (first-year ice) and fast ice, respectively. The results showed that ice volume can be small even if the ice area is large, due to thinness of the ice (e.g. in 1999 in the Sea of Okhotsk). A significant out-of-phase response, i.e. ice volume is larger in the Sea of Okhotsk when ice volume is smaller in the Bering Sea, was observed. The period of this see-saw showed two different time-scales, which were short (1 week) and long (2−4 weeks).

During March 2003, Autosub, an autonomous underwater vehicle (AUV) operated by the UK National Oceanography Centre, Southampton, was deployed under Sea ice north of Thurston Island, Amundsen Sea, Antarctica (at ∽71˚ S, 100˚ W). The vehicle was fitted with an upward-looking 300 kHz acoustic Doppler current profiler (ADCP) to provide current velocity above the AUV. The ADCP also recorded ranges to the ocean–ice interface. Such data can be used to derive Sea-ice draft by using a number of novel processing Steps Such as correcting for the coordinate Systems of the ADCP unit and the vehicle as well as corrections for changes in Sound Speed. This paper outlines the processing Stages required to obtain a probability density function (PDF) of Sea-ice draft and presents PDFs for the region north of Thurston Island. The distribution of ice draft was found to be unimodal, with modes between 2.2 and 2.4 m. Given the uncertainty in Sound Speed, the limit of accuracy was estimated as ∽6 cm.

Mass-balance measurements were initiated in 2007/08 on Sørbreen, Jan Mayen, including operation of automatic weather stations in the ablation zone. Mean daily melt rate is 3.6 cmw.e. d−1 for the investigated snow-free period of 115 days in June-September 2008. During this period, the net radiation is the largest contributor to melt. However, the relative contribution is highest in June (81%) and less in September (21%). The net longwave radiation is negative, acting as a heat sink. The climate on Jan Mayen is polar maritime with generally high humidity and overcast conditions. This leads to a positive latent heat flux, which represents condensation to the glacier surface. Persistent temperature inversions on the island lead to non-linear lapse rates and an ablation profile where melt does not necessarily decrease with increased elevation. A comparison of air temperatures on the glacier and twice-daily radiosonde ascents from the meteorological station, ∼ 20 km away from the glacier, shows that air temperatures at corresponding elevations are highly correlated (R 2 = 0.94–0.96). This indicates that radiosonde temperature profiles can be valuable for determining lapse rates for melt modeling of the glacier.

In polar regions, the exchange of heat, fresh water and salt water, andmomentum between ocean and atmosphere is strongly affected by the presenceof sea-ice cover. As a growing number of climate models include adynamic–thermodynamic sea-ice component to take these effects into account,it might be asked whether sea ice is adequately represented in thesesimulations, and how far these simulations fit with physicalobservations.

Sea ice in the classical models (Hibler, 1979; Parkinson and Washington, 1979) that have been available for two decades, is regarded as atwo-dimensional (2-D) continuum covering the ocean surface. The prognosticvariables describing the ice pack are horizontal ice velocity, arealcoverage (ice concentration), and ice thickness. In numerical models, thesevariables and their evolution in space and time are solved on an Euleriangrid.

A number of observational data are available to verify the model results.Sea-ice drift is observed from drifting buoys deployed on ice floes. Arealsea-ice coverage can be observed with satellite-borne passive-microwavesensors (SMMR, SSM/I). For ice thickness, which cannot be observed withremote-sensing techniques, rather few, scattered observations fromupward-looking sonars on submarines and moorings are available.

This article gives an overview of three additional variables representingsea ice in large-scale climate models. These are (1) roughness, (2) age ofthe ice, introduced as two prognostic variables, and (3) simulatedtrajectories of ice motion, which are diagnosed from the Eulerian velocitygrid. The new variables enable a more detailed look at sea ice in models,helping to understand better the coupled dynamic–thermodynamic processesdetermining the polar ice cover. Further, the new variables offer important,additional possibilities for comparing the simulated sea-ice properties withavailable observations.

It has been suggested (Hammer 1977, Gudmandsen and Overgaard 1978, Millar 1981) that layers of acidic ice, formed after large volcanic eruptions, are a cause of radio echo layering. The power reflection coefficient (PRO of these reflecting layers may be related to their acid content and thickness. The present paper makes estimates of ice acidity from radio echo-sounding (RES) and compares them with measured values along Greenland ice cores. Dated Antarctic PRC/depth profiles are also presented, and acidity estimates made which give a crude indication of past volcanic activity in the southern hemisphere to ~150 ka BP.

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

A preliminary version of a three-dimensional ice-sheet model for later use in climate models, but excluding ice shelves and basal sliding, is presented and applied to the Antarctic ice sheet. In the model, the three-dimensional fields of velocity and temperature are calculated in the coupled mode, and the temperature equation is integrated for 150 000 years; the shape of the Antarctic ice sheet remains fixed. The results from the model are consistent with a stationary state in the central parts of the Antarctic ice sheet, but not in marginal areas, where the flow in the model is too small. Including a parameterized form of basal sliding that is dependent on the water pressure is likely to improve the situation.

Vestfonna ice cap, northeastern Svalbard, is one of the largest ice bodies in the European Arctic, but little is known about the evolution of its mass balance. This study presents a reconstruction of the climatic mass balance of the ice cap for the period 1979/80-2010/11. The reconstruction is based on calculations using a mass-balance model that combines a surface-elevation-dependent accumulation scheme with a spatially distributed temperature-index ablation model that includes net shortwave radiation. Refreezing is included, based on the basic P max approach. The model accounts for cloud-cover effects and surface albedo variations that are calculated by a statistical albedo model. ERA-Interim derived air temperature, precipitation and total cloud-cover data are used as input. Results reveal a mean climatic mass-balance rate of +0.09 ± 0.15 m w.e. a–1 for the study period. Annual balances show a slight, insignificant trend towards less positive values over the study period. Refreezing is estimated to contribute about one-third to annual accumulation, and a significant positive trend in refreezing is present over the study period. The modelling results reveal a significant steepening of the climatic mass-balance gradient and indicate a lengthening of the characteristic 3 month ablation period in recent years.

Ice-thickness and surface-elevation data gathered from radio echo flights over the Antarctic Peninsula are presented as profiles for five major outlet glaciers in northern Palmer Land and as contour maps for an area of 8 000 km2 to the east of George VI Sound. Glacier profiles appear to be closely related to ice discharge especially to convergent and divergent flow. Comparison of subglacial topography with geological evidence of faulting suggests that the area around George VI Sound is a region where structure is an important influence on the pattern of glacial erosion.

Sea-ice observations have been conducted on board icebreaker shirase as a part of the Scientific programs of the Japanese Antarctic Research Expedition. We Summarize these to investigate Spatial and interannual variability of ice thickness and Snow depth of the Summer landfast ice in Lützow-Holm Bay, East Antarctica. Electromagnetic–inductive observations, which have been conducted Since 2000, provide total thickness distributions with high Spatial resolution. A clear discontinuity, which Separates thin first-year ice from thick multi-year ice, was observed in the total thickness distributions in two voyages. Comparison with Satellite images revealed that Such phenomena reflected the past breakup of the landfast ice. Within 20–30km from the Shore, total thickness as well as Snow depth decrease toward the Shore. This is due to the Snowdrift by the Strong northeasterly wind. Video observations of Sea-ice thickness and Snow depth were conducted on 11 voyages Since December 1987. Probability density functions derived from total thickness distributions in each year are categorized into three types: a thin-ice, thick-ice and intermediate type. Such interannual variability primarily depends on the extent and duration of the Successive break-up events.

Seward Glacier, on the Alaskan/Yukon border along the Gulf of Alaska, sits atop an important structural and morphological junction in the Saint Elias orogen. It is situated at the intersection between the Fairweather and Bagley strike–slip faults, and in the hanging wall of the Malaspina and Chugach–Saint Elias thrust faults. An ice surface velocity map of Seward Glacier derived from interferometric synthetic aperture (InSAR) reveals a complex flow pattern, which implies there is a previously unmapped northwest-trending supra-/subsurface ridge crossing the Seward. Analysis of additional remote-sensing images, ASTER, ERS SAR and the InSAR coherence map, confirms this observation. The presence of this ridge leads to a set of tectonic models describing the possible interaction of the underlying faults.

Ion-chemistry and sulphate-isotope values for snow samples from the Prince of Wales Icefield, Ellesmere Island, Canada, show distinct seasonal trends and spatial patterns. Sixteen surface snow samples from two transects, and 30 samples from five depth profiles, representing fall 2003 to spring 2004 accumulation, have been analyzed. Surface snow samples show decreasing SO4 2– and Na+ concentrations along with decreasing δ34S values with distance inland and increased elevation. These trends follow an expected pattern of decreasing sea-salt aerosol impact with greater vertical and horizontal distance from sea-water sources. Depth-profile total sulphate and non-sea-salt sulphate increase in concentration with height in the snowpack, and these results, combined with δ34S values that are more positive in fall snow, are consistent with increased amounts of anthropogenic sulphate in surface spring snow. Sulphate apportionment was performed on surface snow assuming an isotopically light sulphate source (anthropogenic plus volcanic) mixed with isotopically heavier sulphate from dimethylsulphide (DMS) oxidation and sea water. Isotopically light sulphate in surface snow was apparent at all elevations at a reasonably uniform concentration. DMS sulphate, however, decreased exponentially with altitude, reflecting an ocean level source with oxidation occurring during transport and deposition. The significance to multi-year deposition studies is that sulphate from DMS oxidation may be related to sea-ice conditions in the region.

The electrical properties of water ice impact the study of diverse frozen environments, in particular the radar sounding of ice masses. The high-frequency response of meteoric polar ice depends partly on the bulk concentration of ammonium (NH4 +), but the nature of this response has been unclear. Here we use broadband dielectric spectroscopy to investigate the electrical response of laboratory-frozen solutions. By analyzing the relaxation frequency of these samples and its temperature dependence, we show that the mobility of Bjerrum D-defects formed in the ice lattice by ammonium is 1.4 ±0.8 x 10–9m2 V–1 s–1 at -20°C, or about an order of magnitude smaller than that of Bjerrum L-defects formed by chloride. However, co-substitution of both ions increases the ice-lattice solubility of chloride by a factor of ∼7, causing an enhanced conductivity response due to greater concentrations of Bjerrum L-defects. Thus, despite its low mobility, ammonium can also affect the high-frequency electrical response of polar ice, but its covariance with chloride must be considered.

Thrust-block naled in front of Kuannersuit Glacier, West Greenland, appears to have formed during the termination of a terrestrial surge event by a combination of enhanced winter runoff, rapid advance of the glacier terminus, and proglacial stress release by thrusting and stacking of naled blocks. This process is equivalent to the formation of thrust-block moraines. The thrust-block naled consists of at least seven thrust sheets, which are characterized by stratified ice with beds composed of a lower debris-rich lamina, an intermediate dispersed lamina and a top clean-ice lamina, and underlain by frozen outwash deposits. The thrust-block naled differs from basal stratified ice in the absence of internal deformation structures, a relatively low debris concentration, a clay-rich particle-size distribution and a preferential sorting of lighter minerals. The oxygen isotope composition of the thrust-block naled is indistinguishable from δ18O values from meteoric glacier ice and bulk meltwater, but different from basal stratified ice facies. The d–δD relationship indicates that thrust-block naled has been formed by freezing of successive thin layers of bulk waters with variable isotopic composition, whereas basal stratified ice has developed in a subglacial environment with regelation. This work shows that the association between proglacial naled and rapidly advancing glaciers may have significant consequences for the proglacial geomorphology and the interpretation of basal ice layers.