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.

Satellite observations of microwave emission are a key resource for estimating surface temperatures in Antarctica. Use of these data to examine climate variability, however, relies on the assumption of constancy through time in the relationship between surface temperatures and the proxy brightness temperatures. Thus we are motivated to study the physical relationship between surface and brightness temperature time series, and to seek indicators of possible temporal variability in that relationship. Here we report an initial study using near-surface temperatures from the Byrd Station automated weather station in West Antarctica and 37 GHz, vertically polarized brightness temperatures from the Scanning Multichannel Microwave Radiometer. We begin with the simplest model of the relevant thermal and microwave physics and derive a convolution expression that relates surface and brightness temperatures. The convolution kernel depends on firn thermal diffusivity and the microwave extinction coefficient in a particularly simple way: solely through a single characteristic time-scale. For the Byrd data, we find that the (fractional variation in) observed brightness temperatures can be reproduced by our model in considerable detail, on scales from interannual down to a few days. The time-scale is tightly constrained by minimization of the discrepancy between observed and simulated time series, and the optimized value agrees closely with that derived from independent estimates of firn thermal and microwave parameters. We find no evidence thus far of temporal variability in the relation between surface and brightness temperatures, though investigation across a wider domain in space and time is needed before such variability can be ruled out.

Where polythermal glaciers have frozen margins that buttress otherwise temperate-based sliding ice, longitudinal compression can strongly influence ice-flow trajectory, and consequently sediment transport paths. Past efforts to model flow in the vicinity of a basal thermal transition (BTT) have generally relied on simplified boundary conditions or rheological idealizations, making these model results difficult to apply to real glacier termini. Herein, we present results of numerical simulations using a power-law rheology and with boundary conditions that better represent the frozen margin. Model results indicate that a transition to a non-sliding frozen margin causes a decline in surface velocity made possible by upward ice flow, implying either enhanced ablation for steady-state simulations or the formation of a surface bulge. Permitting ice loss by ablation combined with numerical smoothing of the basal slip transition subdues basal stress concentrations and thereby inhibits development of structural discontinuities such as thrust faults. Upward ice flow is accommodated by vertical extension up-glacier of the BTT. This strain regime can potentially account for key structural features in polythermal glacier termini without appealing to thrusting.

This study determines variations in ice extent of Nevado Illimani, Bolivia (16°38' S, 67°44' W), from 1963 to 2009. The results are compared with net accumulation rate variations obtained from a local ice core. We then propose an interpretation of the recent environmental history (last 46 years) of the region based on a study of remotely sensed and ice-core data. From 1963 to 2009, Nevado Illimani lost a total ice area of 9.49 ±1.09 km2, a 35% reduction. Area variations generally followed variations in net accumulation rates during this period. Despite the current glacier area reduction trend, the Nevado Illimani glaciers will not completely disappear in the next few decades.

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

Sea ice in the classical models (Hibler, 1979; Parkinson and Washington, 1979) that have been available for two decades, is regarded as a two-dimensional (2-D) continuum covering the ocean surface. The prognostic variables describing the ice pack are horizontal ice velocity, areal coverage (ice concentration), and ice thickness. In numerical models, these variables and their evolution in space and time are solved on an Eulerian grid.

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

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

The problem of recovering the small aspect ratio of the ICE-4G reconstruction of the Last Glacial Maximum Laurentide ice sheet has proven to be a challenge for state-of-the-art thermomechanically-coupled three-dimensional ice-sheet models coupled to reduced climate models. Flow enhancements to Glen’s flow law, 20 to 30 times those required to adequately simulate the present-day Greenland ice sheet, have been found necessary in order to reproduce both the thickness and areal extent of the geophysical reconstruction. Within the confines of the Glen flow rheology, it is unclear what mechanism might explain the magnitude of this discrepancy in required flow enhancement for the Laurentide relative to the Greenland ice sheet We present a comparative analysis of three alternative explanations of such a questionable flow-law enhancement: radical changes to mass balance; radical changes to ice-sheet history; and strongly enhanced basal flows Based on this analysis, we argue that none of these alternatives provide a fully acceptable explanation for the small ICE-4G LGM aspect ratio of the Laurentide ice sheet, that has been inferred geophysically.

An ion chromatographic method for the determination of fluoride and some organic anions (lactate, acetate, glycolate, propionate, formate, methane sulphonate and pyruvate) at sub-μgl−1 concentration levels is applied to a 22 m (63 years) firn core drilled at Hercules Névé, northern Victoria Land, Antarctica. The first effective distribution data of acetate, propionate and formate for this region are reponed here. Mean values of 9.9,7.7 and 2.4 μgl−1 were calculated for acetate, Formate and propionate, respectively, in the absence of particular events (background values).

The temporal (1928-82) concentration/depth profiles of these components showed a probable long-term biomass-burning event in the 1930s that can be related back to processes in the Southern Hemisphere. Such burning events may be demonstrated from the simultaneous concentration increase of carboxylic acid, potassium, ammonium and fluoride and from a very high dust content. Similar increasing trends in the same time period are not shown by other snow components usually considered as source indicators (methane sulphonic acid: biogenic marker; nssSO42- : biogenic and volcanic indicator; Na+ and Cl−: sea-spray contribution; Ca2+ : crustal input), so it was possible to exclude such alternative explanations.

As an iceberg melts, the resulting change of shape can cause it to list gradually or to become unstable and topple over suddenly. Similarly, when an iceberg breaks up some of the individual pieces may capsize. We have used Zeeman’s analysis of the stability of ships, which is based on catastrophe theory, to examine this problem. We deal only with statical equilibrium; dynamical effects induced by water motion are important for ships, but very large icebergs have correspondingly small oscillations and therefore dynamical aspects are ignored in this first study. The advantage of the catastrophe-theory approach over the conventional stability theory used by naval architects lies in the conceptual clarity that it provides. In particular, it gives a three-dimensional geometrical picture that enables one to see all the possible equilibrium attitudes of a given iceberg, whether they are stable or unstable, whether a stable attitude is dangerously close to an unstable one, and how positions of stable equilibrium can be destroyed as the shape of the iceberg evolves with time.

By making two-dimensional computations we examine the stability of two different shapes of cross-section, rectangles and trapezia, with realistic density distributions. These shapes may list gradually or topple suddenly as a single parameter is changed. For example, we find that a conversion of the vertical sides of a rectangular section into the slightly inward-sloping sides of a trapezium has a comparatively large adverse effect on stability. The main purpose of this work is to suggest how the stability characteristics of any selected iceberg may be investigated systematically.

Using June–August surface meteorological measurements for 2004–10 we found that the duration of the summer melt season at elevations of 1800, 1300 and 1000 m a.s.l. on Devon Ice Cap, Canada, increased at a rate of 3.4 (p < 0.1; weak significance), 6.1 (p< 0.01) and 8.8 (p < 0.05) days a−1, respectively. The calculated surface melt rate at 1300m a.s.l. increased from 74 to 133 cm w.e. a−1 between 2007 and 2010. These changes are linked to two types of change in the Arctic atmospheric circulation. Strengthening of the 500 hPa ridge over the Arctic in June–July resulted in increases in both the advection of warm air into the region and the occurrence of cloud-free conditions over the ice cap, causing the available melt energy to increase by 4–24% relative to June–July 2007–10 mean conditions. More frequent southwesterly low-pressure systems in August after 2004 accounted for a 12–38% increase in available melt energy relative to the August 2007–10 daily mean due to advection of warm air into the Arctic, reduced incoming shortwave radiation and increased net longwave radiation. This delayed the timing of freeze-up by an average of 5.5 days a–1 (p < 0.05) at the three sites over 2004–10.

Casa Pangue glacier is a regenerated valley glacier, covered by supraglacial moraine of variable thickness (1 to 3 m). Seven moraine in-transit arcs have originated from avalanches falling on the ice from the steep walls at the head of the valley. The debris has been relocated by glacier movement, and vegetation has become established on areas with sediment cover. Primitive soil has developed very rapidly, probably in less than 100 a. Chemical analysis of soil samples show that it is acid (pH 4.6 to 4.7), nitrogen and organic matter are absent, calcium content is low, and potassium content is high. Pedogenic processes are mostly related to intense chemical weathering, under conditions of more than 4 000 mm a−l of total precipitation.

The plant communities established on the moraine are essentially similar to the Va1divian rain forest that characterizes the region. The most frequent tree is “coihue” (Nothofagus dombeyi), followed by “teniú“ (Weinmannia trichosperma) and “notro” (Embothrium coccineum). One specimen of N.dombeyi was found to be 18 m tall and 0.62 m in diameter; many others were taller than 12 m and reproduction was abundant. Dendrochronological analysis indicates a minimum age of 45 a for the oldest tree. Other plants found here are shrubs, some hemiparasitic and creeping plants, mosses, lichens, ferns, and fungi.

Using air photographs of 1942, 1953, 1970, and our own oblique photographs of 1978, taken from the summit of a neighbouring peak 1 200 m above the glacier tongue, average surface velocity of the glacier tongue was estimated at 22.5 m a−l for the lower and intermediate sectors where the trees are growing. If the total length of the regenerated valley glacier is taken into account, the mean annual movement rate is 35.0 m a−l. If this value is extrapolated over the last 45 a, the trees have moved an average distance of at least 1 000 m in that time.

The discovery of established communities (also observed at Río Blanco glacier, southwest of Mt Tronador) on moving ice constitutes an event not previously recorded in glaciological literature. Some significant aspects are discussed: time lapse for soil development on moraine deposits, primary plant succession on moraine deposits, the need of stable ground for plant colonization, the absolute validity of radiocarbon dating of glacier advances using fossil wood found within terminal moraines, and the validity of lichenometric techniques in deglaciated terrain.

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.

Ice-front change may well be a sensitive indicator of regional climate change. We studied the coastal sector of Wilkes Land, East Antarctica, along the Adélie and Banzare Coasts, extending from Buchanan Bay (67°05’ S, 144°30’ E) to Porpoise Bay (67°S, 128°E). The glaciers in this area drain the northern part of Dome C (area 270 000 km2). A comparison of maps, photographs and satellite images, dated several years apart, led to an estimation of the fluctuations of 18 ice fronts over the 50 years 1947–97 .The area of the floating glaciers in 1963 was 3035 km2, and in 1989, 2785 km2. The main glaciers in the area are Zélée, Astrolabe, du Français, Commandant Charcot and Pourquoi Pas for the Adélie Coast, and Dibble, May, Sandford and Frost Glaciers for the Clarie and Banzare Coasts. Most of the floating glaciers have shown cyclical behaviour without a marked trend, but a general reduction since 1947. The reduction in the area of floating glaciers since the 1950s may be linked to changes in ice–ocean interaction, as noted for the floating glaciers of the George V Coast and the Cape Adare area, and sea-ice extent. The calving behaviour of the main glacier tongues is characterized by an accumulation of icebergs projecting from the coast to form iceberg tongues, held in place by grounding and joined together by annual or perennial fast ice.

To prevent spinning of the upper non-rotated part of the electromechanical drill, an ‘anti-torque system’ has to be included in the downhole unit. At the same time, the anti-torque must allow the drill to move up and down the borehole during drilling and tripping operations. Usually the anti-torque system has a blade form of various designs that engages with the borehole wall and counteracts the torque from the stator of the driving motor. This paper presents a review of the different anti-torque systems and test results with selected designs (leaf spring, skate and U-shaped anti-torque systems). Experiments showed that the skate anti-torque system can provide the maximal holding torque between 67 and 267 Nm−1 depending on the skates’ outer diameter and ice temperature, while the leaf spring anti-torque system can provide only 2.5–40 N m−1 (in case of straight contact between the ice and the leaf springs). The total resistance force to axial movement of the skate anti-torque system lies in the range 209–454N if the system is vibrating. For the leaf spring anti-torque system, the total axial resistance force is far less (19–243 N).

Analysis of AVHRR data collected during the summer and winter over the Ross Ice Shelf reveals complex patterns of curvilinear stripes. In particular, a large, looping pattern of stripes is observed west of Crary Ice Rise in an area where conventional glaciological data collected with surface and airborne methods have been interpreted to suggest uncomplicated flow. On the basis of previous work using radar data to study ice flow downstream of Crary Ice Rise, we conclude that the stripes represent relict flowlines. The mechanism that produces these stripes is unclear, but we hypothesize that they are associated with subtle topography. Based solely on the patterns of stripes and their location in the outflow of major ice streams, we propose that they are related to an ice raft torn from the grounded ice sheet about 400 km upstream from its present position.

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 characteristics of summer energy budgets in the ablation zones during the summer at the surface of two glaciers in the Antarctic Peninsula are investigated and compared to the findings of previous studies. The study areas are located on King George Island (62° S) and in Marguerite Bay (68° S). The summer energy balance was computed from automatic weather station data. The results reveal that turbulent heat fluxes dominate over radiation balance in Marguerite Bay whereas on King George Island ablation is driven by net radiation. The summer energy balance on King George Island reflects the more maritime subpolar climate along the northwest tip of the peninsula in contrast to a more continentally toned polar climate in Marguerite Bay and areas further south. The terms of the energy balances are partitioned very differently but ad-vection from northerly directions causes the highest summer snowmelt rates at both study sites. It is concluded that sensitivity studies should consider not only the mean air-temperature increase, but also possible changes in other climate parameters.

Analyses of atmospheric air extracted from air bubbles in polar glacier ice provide a measure of past CO2 concentrations and their temporal variations. Earlier measurements have shown that the atmospheric CO2 concentration was significantly lower during the late Wisconsin stage and that the change from low to high CO2 concentration occurred in a relatively short time period.

We measured the CO2 concentration of ice samples from the deep ice core recently drilled at Dye 3 (south Greenland). The core section investigated represents ice from about 40 to 30 ka BP. The air extracted from the ice samples shows large variations of CO2 concentration which are correlated with δ18O values of the ice samples. A probable explanation of the results is that corresponding changes of the atmospheric CO2 concentration occurred during that glacial period. These changes could have had a significant influence on the climate. Possible reasons for the variations of the atmospheric CO2 concentration are discussed.

The effect of freshwater sources on wintertime sea-ice CO2 processes was studied from the glacier front to the outer Tempelfjorden, Svalbard, in sea ice, glacier ice, brine and snow. March–April 2012 was mild, and the fjord was mainly covered with drift ice, in contrast to the observed thicker fast ice in the colder April 2013. This resulted in different physical and chemical properties of the sea ice and under-ice water. Data from stable oxygen isotopic ratios and salinity showed that the sea ice at the glacier front in April 2012 contained on average 54% of frozen-in glacial meltwater. This was five times higher than in April 2013, where the ice was frozen seawater. In April 2012, the largest excess of sea-ice total alkalinity (AT), carbonate ion ([CO32−]) and bicarbonate ion concentrations ([HCO3−]) relative to salinity was mainly related to dissolved dolomite and calcite incorporated during freezing of mineral-enriched glacial water. In April 2013, the excess of these variables was mainly due to ikaite dissolution as a result of sea-ice processes. Dolomite dissolution increased sea-ice AT twice as much as ikaite and calcite dissolution, implying different buffering capacity and potential for ocean CO2 uptake in a changing climate.

We introduce a method to construct an ice thickness chart using two satellite datasets and a one-dimensional high-resolution thermodynamic snow and sea-ice model (HIGHTSI). Thin-ice thickness up to 40 cm is retrieved using MODIS ice surface temperature data. For thicker ice, thickness is retrieved from a combination of SAR image and background level ice thickness chart Hi provided by HIGHTSI. Because Hi is inherently static, we utilize passive microwave data based sea-ice concentration charts to introduce mesoscale ice dynamics into Hi. In order to create the thickness chart, the value of modified Hi is scaled by a factor which depends on the magnitude of backscattering coefficient σ0. The proposed method is effective in cold winter conditions. We calculated a series of ice thickness charts covering the Kara Sea, Arctic Russia, during winter 2008/09. The ice thickness charts were validated against Russian ice charts. Our method gave realistic results in the thickness range 30–120 cm and was uncertain for the detection of thinner-ice areas. Due to the limitations in our reference dataset, more validation work is needed to establish the accuracy in more detail. Our thickness charts can be used for operational purposes and in climate studies.

Suspended-sediment concentration (SSC) and discharge time series have been obtained for a proglacial stream draining from Scott Turnerbreen, a non-temperate glacier at 78° N in the Svalbard archipelago. These time series exhibit seasonal trends in diurnal hysteresis between SSC and discharge, which changes progressively from clockwise (SSC lead) to anticlockwise (SSC lag), and in the availability of sediment for fluvial transport, which increases during the season. These results contrast with those for streams draining temperate glaciers, in which a seasonal trend in diurnal hysteresis is typically not observed, and sediment supply is usually exhausted during the melt season. This contrast indicates differences in the processes of sediment acquisition and in temporal patterns of sediment transport between temperate and non-temperate glaciers, which reflect different drainage-system structures. The principal mechanism of suspended-sediment acquisition by meltwater is subaerial sediment supply to ice-marginal channels at non-temperate glaciers, whereas at temperate glaciers it is subglacial supply to basal channels. The hysteresis trend probably arises from a delaying effect, because of sediment circulation in pools and slack water adjoining the ice-marginal channels, which varies with discharge. Continuing subaerial sediment supply from heavily debris-covered ice-cored moraines during the melt season precludes sediment-supply exhaustion at Arctic glaciers but means that measurements of sediment flux give a misleading indication of the contemporary rate of glacial erosion.