Icequakes at or near the bed of a glacier have the potential to allow us to investigate the interaction of ice with the underlying till or bedrock. Understanding this interaction is important for studying basal sliding of glaciers and ice streams, a critical process in ice dynamics models used to constrain future sea-level rise projections. However, seismic observations on glaciers can be dominated by seismic energy from surface crevassing. We present a method of automatically detecting basal icequakes and discriminating them from surface crevassing, comparing this method to a commonly used spectrum-based method of detecting icequakes. We use data from Skeidararjökull, an outlet glacier of the Vatnajökull Ice Cap, South-East Iceland, to demonstrate that our method outperforms the commonly used spectrum-based method. Our method detects a higher number of basal icequakes, has a lower rate of incorrectly identifying crevassing as basal icequakes and detects an additional, spatially independent basal icequake cluster. We also show independently that the icequakes do not originate from near the glacier surface. We conclude that the method described here is more effective than currently implemented methods for detecting and discriminating basal icequakes from surface crevassing.

During the 1980 eruption of Mount St. Helens, the occurrence of floods and mudflows made apparent a need to assess mudflow hazards on other Cascade volcanoes. A basic requirement for such analysis is information about the volume and distribution of snow and ice on these volcanoes.

An analysis was made of the volume-estimation methods developed by previous authors and a volume- estimation method was developed for use in the Cascade Range. A radio echo-sounder, carried in a backpack, was used to make point measurements of ice thickness on major glaciers of four Cascade volcanoes (Mount Rainier, Washington; Mount Hood and the Three Sisters, Oregon; and Mount Shasta, California), These data were used to generate ice-thickness maps and bedrock topographic maps for developing and testing volume-estimation methods. Subsequently, the methods were applied to the unmeasured glaciers on those mountains and, as a test of the geographical extent of applicability, to glaciers beyond the Cascades having measured volumes.

Two empirical relationships were required in order to predict volumes for all the glaciers. Generally, for glaciers less than 2.6 km in length, volume was found to be estimated best by using glacier area, raised to a power. For longer glaciers, volume was found to be estimated best by using a power law relationship, including slope and shear stress. The necessary variables can be estimated from topographic maps and aerial photographs.

Investigations of Zelunglung and Midui Glaciers in southeast Tibet, China, indicate that they have some characteristics of surge-type glaciers. There have been two extraordinary movements of Zelunglung Glacier, one in 1950 and one in 1968. A collapse of the terminus area took place in 1984. Midui Glacier experienced extraordinary movements about 55 years ago and also in 1988. During these events, the glacier termini reached moraines formed during neoglaciation and the Little Ice Age. The advances of the two glaciers are not related to climate variation. The glaciers caused serious disasters with loss of life and property, and disruption of transportation corridors.

Triglav glacier is situated on the northeast side of the highest Slovenian mountain peak, Triglav; it is a glacier remnant of the Little Ice Age. Next to Triglav glacier is the Kredarica mountain hut with a meteorological station. At 2514 ma.s.l., it is the highSest meteorological station in Slovenia, and has been in continuous operation since 1954. In this paper, the acquisition of three-dimensional data from archived, non-metric, panoramic, Horizont images is presented. The annual variations of Triglav glacier’s area are given for the period 1976–2010, together with monthly snow variations for the years 1977 and 1998. Additionally, theoretical and empirical volumes and an empirical thickness reduction are computed. The changes to Triglav glacier are compared with the summarized meteorological data from the Kredarica meteorological station. In 1976 Triglav glacier covered an area of 15 ha; by 1992 this had shrunk to 4.3 ha, and it reached its minimum of 0.6 ha in 2003, as measured from Horizont images. Since then the glacier has been mainly conserved by the snow cover from previous winters.

Englacial horizons deeper than 100m are absent within 100MHz ground-penetrating radar (GPR) surface profiles we recorded on Clark and Commonwealth Glaciers in the Antarctic Dry Valleys region. Both glaciers show continuous bottom horizons to 280 m, with bottom signal-to-noise ratios near 30 dB. Density horizons should fade below 50 m depth because impermeable ice occurred by 36 m. Folding within Commonwealth Glacier could preclude radar strata beneath about 80 m depth, but there is no significant folding within Clark Glacier. Strong sulfate concentrations and contrasts exist in our shallow ice core. However, it appears that high background concentration levels, and possible decreased concentration contrasts with depth placed their corresponding reflection coefficients at the limit of, or below, our system sensitivity by about 77m depth. Further verification of this conclusion awaits processing of our deep-core chemistry profiles.

Traditional methods of measuring the propagation of waves originating from ocean swell and other sources have relied on wire strain gauges, accelerometers or tiltmeters. All methods required constant attention to keep in range, while data recovery has demanded that the instrument site be revisited. In this paper, we describe the use of ultra-sensitive tiltmeters and novel re-zeroing techniques to autonomously gather wave data from both polar regions. A key feature of our deployments has been the use of the Iridium satellite communications system as a way of ensuring continuous data recovery and remote control of the instrumentation. Currently four instruments have been successfully reporting from the Arctic Ocean for over 18 months, with two further units deployed in 2005, one in the Weddell Sea, Antarctica, and one additional unit in the Arctic.

IceCube, a cubic-kilometer neutrino detector, was built at the South Pole using a hot-water drill system. Deep holes were drilled into the Antarctic ice sheet and filled with highly sensitive optical instrumentation. For the hot-water drilling, a computer model was developed to predict the hole sizes and hole lifetimes during construction. The goal was to predict ultimate size and freezeback rates based on water flow rate and temperature, drill speed, ice temperature and ream parameters (for a secondary operation where hot water continues to flow as the drill is withdrawn). This model proved to be very successful. It increased confidence that the holes would remain open long enough after drilling to allow the deployment of the necessary instrumentation. It also allowed for a decrease, over the course of the project, in the amount of overdrilling that was used as a margin against a too-rapid freeze-in. This resulted in significant fuel savings.

The chemical (Na+, K+, Mg2+, Ca2+, CH3SO3− (MSA), Cl− , NO3− , SO42-) and isotopic (δl8O) composition of snow and firn samples from Campbell Glacier, northern Victoria Land, Antarctica, was studied to evaluate the accumulation rate of snow and to investigate the chemical contribution from some emission sources (marine biogenic activity, sea and crust). During the 1994-95 Italian Antarctic Expedition, snow and firn were collected from snow pits and from cores obtained from drilling at three sites (A: 74°41'S, 164°30' E; B: 74°15' S, 164° '04' E; C: 73°45' S, 163°20' E), located ai 50 m (on the floating glacier tongue), 800 m and 1580 m a.s.l., respectively.

The mean concentration of sea salt decreased with increasing distance from the coast and with altitude. Generally, the Na+/K+ and Na+/Ca2+ ratios were much lower than the bulk sea-water ratios at sites B and C. The MSA showed mean concentrations (0.27 and 0.17 ¿teq 1 at sites B and C, respectively) consistent with data obtained from other Antarctic sites. The mean concentrations of NO3 ranged from 2.1 μeq 1−1 (site A) to 0.97 μeq1 1 (site C).The mean nss (non-sea-salt) SO42-/SO42- ratio was -0.055,0.54 and 0.42 at sites A, B and C, respectively. Moreover, the relationship between a2+, nssCa2+, SO42- and nssSO4 was quite different at sites B and C. in order to expla in the relationships between the elements and compounds studied at these sites, chemical fractionation and/or reactions inside air masses and différent origin of the air masses at the two sites should be considered.

A comparison of the isotopic and chemical profiles was carried out in order to provide a more reliable chronological scale. The chemical and δ18O seasonal variations recorded along the firn cores from the upper site of Campbell Glacier seem to be fairly homogeneous. This made it possible to identify many annual cycles (14-18 years for the 7 m firn core). Using the measured density values, the accumulation rale was also calculated for lower and upper Campbell Glacier. It did not appear to differ between the two sites (150-170 kg m −2a−1 at site B and 140-180 kg m−2a−1at site C) and is in keeping with rates calculated previously for the same area.

Snow depth is a key parameter for assessing the sea-ice mass budget in the Arctic and for the surface energy balance at the atmosphere–snow–ice–ocean interfaces. However, scientific expeditions to the high Arctic Ocean are rare, and for large parts of the year no snow and ice data are collected in situ in most regions. Therefore any additional in situ observations of snow depth are of interest to the scientific community. Arctic adventurers and tourists are among the most frequent visitors to the Arctic Ocean and North Pole. If properly trained and carefully adhering to standard protocols, they could collect valuable snow-depth data from large regions. Here we analyse such data from four Arctic basin ski traverses carried out between 1994 and 2007. Individual datasets show characteristic regional differences of snow thickness, which provide invaluable information for the validation of models and satellite data. the observations were made applying a continuously upgraded observation guideline scheme. Earlier observations were based on a relatively broad view of easily observable snow and ice parameters. Improvements included requirements of more detailed snow-thickness surveys in order to observe the spatial variability over varying sea-ice surfaces in a better way. Possibilities for, and limitations of, ice-thickness estimates and measurements are also discussed. Often, assessment of ice thickness is more problematic since measurements are either time-consuming or biased, meaning that possibilities for collecting large datasets are limited.

Snow stratigraphy was analyzed in the Maudheimvidda area of western Dronning Maud Land, East Antarctica, during austral summer 1999/2000 as a part of the Finnish Antarctic Research Programme (FINNARP). Measurements were made in shallow (1–2m) snow pits along a 350 km transect from the coast to the polar plateau, covering at least one annual cycle and an elevation range from sea level to about 2500 m. The aim of the study is to document spatial and temporal variations in snow-cover properties, with the further aim of relating these variations to environmental factors and to patterns observable by remote sensing. The measurements suggest five principal snow zones: (i) sea ice, (ii) the seaward edge zone of the ice shelf, (iii) the inner parts of the ice shelf, (iv) the snow cover above the grounding line and (v) the local topographic highs. Local topographic highs such as ice domes and ice rises differ from other snow environments: the snow is less densely packed, possibly an indication of locally reduced speed of the katabatic outflow. Fewer and thinner crusts on the topographic highs are consistent with RADARSAT backscatter variations.

A knowledge of the dimensional characteristics of icebergs off the east coast of Canada is required for both scientific and engineering purposes. To fulfil this need, hydrocarbon exploration in the region has been supported by a program aimed at collecting morphometric data on icebergs, in addition to providing operational support for activities such as ice-berg towing, this program has yielded information which will be useful for the engineering design of offshore structures. Functional relationships between the dimensions of icebergs are presented and ratios between the linear dimensions are examined. These ratios are used to calculate preliminary values for draft and mass on the Grand Banks and are demonstrated to give reasonable values for draft of icebergs off Greenland.

A 15.2 m deep firn core and a 2.7 m snow pit were drilled in the western side of Lambert Glacier basin, East Antarctica, in January 1993. the sampling site LGB16 (72.8˚ S, 57.3˚ E) is located about 650 km from the coast, at approximately 2690ma.s.l. the concentration of methanesulfonate (MSA) was determined in the firn core and snow pit. the continuous MSA record from LGB16, spanning about 60 years from 1933 to 1992, displays a decreasing trend in general, and sharp differences between the upper 10.2 m (corresponding to AD 1952) and the bottom part from 10.2 to 15.2 m. the mean MSA concentration for the whole core is 11.3±14.5 ng g–1; for the upper 10.2 m it is 9.3 ±6.3 ng g–1, compared to 15.4±23.0 ng g–1 for the bottom part. the bottom part has a greater number of high MSA peaks, which is consistent with the Cl– and, to a lesser extent, Na+ records for this core. A negative correlation was observed between sea-ice area for the South Indian Ocean sector (40–90˚E) and MSA concentration in LGB16. No significant link was observed between the high MSA concentration and El Niño events at this location.

The evolution of melt ponds on Arctic sea ice in summer is one of the main factors that affect sea-ice albedo and hence the polar climate system. Due to the different spectral properties of open water, melt pond and sea ice, the melt pond fraction (MPF) can be retrieved using a fully constrained least-squares algorithm, which shows a high accuracy with root mean square error ~0.06 based on the validation experiment using WorldView-2 image. In this study, the evolution of ponds on first-year and multiyear ice in the Canadian Arctic Archipelago was compared based on Sentinel-2 and Landsat 8 images. The relationships of pond coverage with air temperature and albedo were analysed. The results show that the pond coverage on first-year ice changed dramatically with seasonal maximum of 54%, whereas that on multiyear ice changed relatively flat with only 30% during the entire melting period. During the stage of pond formation, the ponds expanded rapidly when the temperature increased to over 0°C for three consecutive days. Sea-ice albedo shows a significantly negative correlation (R = −1) with the MPF in melt season and increases gradually with the refreezing of ponds and sea ice.

We report the first results from a programme recently set up to directly measure the thermal conductivity of young sea ice.

An array of thermistors frozen into first-year Antarctic sea ice provides temperature vs depth data, which is fitted directly with a partial differential equation for heat conduction. Temperatures are recorded every hour at 20 vertical intervals of 100 mm over a period of 5 months, allowing accurate and direct estimation of the thermal conductivity. Preliminary results indicate that the thermal conductivity is in the expected range, with some evidence of non-linear effects deeper in the ice. A larger variance in data is evident at higher temperature gradients and at greater depths in the ice.

Preliminary modelling of the impact of brine migration on heat transport through first-year sea ice is presented. Diffusion-driven brine pocket migration is too slow to contribute significantly to heat flow, but the convective instability of inclined brine slots or tubes is a promising mechanism.

Daugaard Jensen Gletscher, Greenland, is a large tidewater glacier terminating in the northwest corner of the Scoresby Sund fjords. We present a time series of surface flow speeds spanning 1985–2010 based on feature tracking of satellite images. The time series confirms that flow speeds remained stable and reveals a persistent summer acceleration of up to 10% over the lower 10 km of the glacier. The front of the 6 km floating tongue fluctuates by little more than the average size of calved icebergs, ~1 km. While we are unable to detect any imbalance between ice discharge and surface mass balance within our error estimates, observations suggest that the region is losing mass and experiencing decreases in surface elevation. We conclude that as flow speeds and surface mass balance have remained steady since 1985, the shift from balance to imbalance, leading to elevation decrease, must have occurred prior to this date. As for other stable Greenland tidewater glaciers, the seasonal melt cycle is the dominant influence on flow velocity variation but, if the apparent current thinning rates continue, there is potential for the grounding line to retreat, for calving rates to increase and for the glacier to accelerate.

Two deep ice cores are being drilled in Antarctica in the frame of the European Project for Ice Coring in Antarctica (EPICA). The Dome C ice core will provide more information about mechanisms of global climatic changes over several climatic cycles. The DML core, drilled at Kohnen station, will provide a detailed record over the last climatic cycle, which can be compared with Greenland records. The drilling at Dome C reached 3200 m depth during field season 2002/03, and the age of the ice at the bottom of the hole could be 900 000 years according to preliminary estimates. The depth at Kohnen station is 1564.6 m at present, corresponding to an age of about 55 000 years. Analyses along the top parts of both ice cores have provided interesting first results. A few selected results from these parts, mostly published already, are summarized. Only a few measurements are available from the deeper parts of both cores. Dielectric profiling and electrical conductivity measurements, performed in the field, provide continuous and high-resolution records concerning the acidity and the salt concentration of the ice. Continuous flow analyses and Fast Ion Chromatography also provide high-resolution records of several chemical compounds. These records give some clues as to the age scale of the EPICA Dome C ice core, but they also leave us with many open questions.

Subglacial hydrology is an important component of the ice dynamic system in Antarctica but is challenging to investigate due to the large spatial scales of the catchment systems, the ice thickness, and remote location. Here I discuss key discoveries about Antarctic subglacial hydrology from the Glacier Drainage System (GlaDS) model, including the presence of long, often high-pressure, subglacial channels. These channels pump tens of cubic metres per second of freshwater into ice-shelf cavities and directly affect melt rates at the critical grounding zone regions. Future ice dynamics and ice-shelf cavity models should take subglacial hydrology into account if they are to accurately predict future behaviour of the Antarctic Ice Sheet.

This physics-based two-phase flow model of the mass balance of drifting snow calculates the transport of snow through saltation and suspension, and recognizes the important role of in-transit sublimation on surface-erosion rates. Measurements of the vertical gradient of drifting snow-mass flux and wind speed in the surface-boundary layer indicate the total flux of saltating snow increases linearly with wind speed and is sensitive to the transport threshold. The total flux of suspended snow requires saltation to become established, and increases with the cube of both the total flux of saltating snow and the wind speed. The total suspended flux quickly becomes the dominant transport mode as wind speeds increase beyond threshold levels, and comprises more than 90% of the total flux for wind speeds greater than 15 ms−1. Sublimation rates estimated from wind speed, temperature, and humidity are sufficiently balanced by snow-surface erosion rates to ablate completely snow-packs with depths of the order 200 mm, a typical value for steppe and prairie environments.

In this study, the three-dimensional (3-D) microstructure of polar firn is investigated by means of X-ray microfocus computer tomography (mCT). Basic topological properties including the Euler and coordination numbers are derived from the reconstructed 3-D volume images. It is shown that sample volumes of about 4 cm3 are representative for polar firn in terms of their connectivity. The connectivity function defined as the change of Euler number with structure size is calculated via image-processing routines. It is used to split the ice phase at small bridges into single crystallite agglomerates. The bond-size distributions and the mean size of the agglomerates are estimated. All μCT measurements were carried out on the uppermost 9 m of a shallow firn core (B35) drilled during the 2005/06 field campaign at Kohnen station, Dronning Maud Land (DML), Antarctica. The results are compared with estimates from classical two-dimensional (2-D) surface section observations. The 3-D approach confirms the linear relationship between coordination number and density which hitherto has only been derived from 2-D observations. Layers of buried snow dunes show a stronger connectivity than layers of moderate crystal size and density. The formation of agglomerates made of crystallites is a common feature of polar firn in DML. It is proposed that the growth of agglomerates leads to reduced critical densities for the transition between the densification regime of grain boundary sliding and plastic deformation.

We analyzed the ice flow of McCall Glacier, Alaska, USA, by numerical glacier modeling and radio-echo sounding (RES). Model experiments were carried out with a higher-order numerical ice-flow model, and results were validated with measurements of annual ice velocities and compared with previous estimates of ice-flow dynamics. During the 2003 summer campaign, detailed RES measurements were carried out along the central flowline of the ablation area with a 5 MHz (central frequency) ice-penetrating radar, where 10m ice temperatures are approximately –7.5˚C. The bed reflection power (BRP) beneath this central flowline abruptly increases at one location area, followed by a slow decrease down-glacier. The model experiments show that basal sliding (<50%) is necessary to match the observed annual mean surface velocities in the area that is characterized by high BRP values. However, when thermomechanical effects are taken into account, a temperate basal ice layer is apparent in the ablation area, which locally softens the ice and can explain to a certain extent the anomalous flow field. The model results confirm that the present temperature field is a remnant of a larger glacier geometry that was near steady state before the onset of enhanced surface thinning in the 1970s.