The rate of mass loss from the Greenland ice sheet has increased over the past decade due, in large part, to changes in marine-terminating outlet glacier dynamics. These changes are attributed to increased submarine melt rates of floating ice tongues and submerged calving faces resulting from increased coastal ocean heat transport. We use remotely sensed data to calculate submarine melt rates for 13 marine-terminating outlet glaciers in Greenland on a semi-annual basis between 2000 and 2010. We assess temporal and spatial variability in the calculated submarine melt rates and compare those variabilities to concurrent glacier change and offshore ocean temperatures. Over the period of study, average melt rates ranged from 0.03 to 2.98 m d−1 and account for 5–85% of the total volume loss from the floating ice tongue, with no clear spatial pattern. Only four glaciers show substantial interannual variability in melt rate during the decade. Melt rates were uncorrelated with front retreat, speed and changes in ocean temperature. Although the small sample size limits our analysis of the relationship between oceanographic forcing and glacier response, these data suggest that the calving rate may vary with discharge but that submarine melt rates are independent of grounding line discharge.

Ice-core data are the only source of ice response on timescales of hundreds to thousands of years, which is necessary to describe polar ice-sheet flows and their interaction with changing climatic conditions. Ice properties, such as a grain growth relation, require knowledge of each ice particle’s history since first deposited at the surface, and not simply the present core state. This study is an analysis of 11 ‘present’ ice cores, using their age/depth data and present accumulation, to infer their past accumulation and mean strain rate and, in turn, the strain at each level of the core. These are the ingredients necessary to determine the particle paths and associated evolution of properties. The conventional assumptions of a purely vertical velocity distribution with a uniform compressive strain rate in the core are made, but unlike an earlier analysis which allowed independent surface accumulation and strain-rate histories, it is now assumed that the strain rate is proportional to the accumulation. Determination of the past accumulation and proportionality factor is accomplished by correlation with the present age/depth data, and while good correlations are obtained – a consistent solution – other close correlations can yield quite different accumulation histories and corresponding proportional strain-rate histories.

Climate variables that control the annual cycle of the surface energy and mass balance on Zhadang glacier in the central Tibetan Plateau were examined over a 2 year period using a physically based energy-balance model forced by routine meteorological data. The modelled results agree with measured values of albedo, incoming longwave radiation, surface temperature and surface level of the glacier. For the whole observation period, the radiation component dominated (82%) the total surface energy heat fluxes. This was followed by turbulent sensible (10%) and latent heat (6%) fluxes. Subsurface heat flux represented a very minor proportion (2%) of the total heat flux. The sensitivity of specific mass balance was examined by perturbations of temperature (±1 K), relative humidity (±20%) and precipitation (±20%). The results indicate that the specific mass balance is more sensitive to changes in precipitation than to other variables. The main seasonal variations in the energy balance were in the two radiation components (net shortwave radiation and net longwave radiation) and these controlled whether surface melting occurred. A dramatic difference in summer mass balance between 2010 and 2011 indicates that the glacier surface mass balance was closely related to precipitation seasonality and form (proportion of snowfall and rainfall).

Subglacial lakes beneath ice streams of Antarctica and supraglacial lakes observed on the flanks of the Greenland ice sheet may seem to be unrelated. The former derive their water from energy dissipation associated with basal friction, the latter from atmospherically driven surface melting. However, using numerical models of ice and water flow, it is shown here that they share a common relationship to basal conditions that implies that surface lakes (or depressions that could host lakes under warmer atmospheric conditions) and basal lakes might exist in tandem.

Both lake-calving Yakutat Glacier (337 km2), Alaska, USA, and its parent icefield (810 km2) are experiencing strong thinning, and under current climate conditions will eventually disappear. Comparison of digital elevation models shows that Yakutat Glacier thinned at area-averaged rates of 4.76 ± 0.06 m w.e.a−1 (2000–07) and 3.66 ± 0.03 m w.e.a−1 (2007–10). Simultaneously, adjacent Yakutat Icefield land-terminating glaciers thinned at lower but still substantial rates (3.79 and 2.94 m w.e.a−1 respectively for the same time periods), indicating lake-calving dynamics helps drive increased mass loss. Yakutat Glacier terminates into Harlequin Lake and for over a decade sustained a ∼3 km long floating tongue, which started to disintegrate into large tabular icebergs in 2010. Such floating tongues are rarely seen on temperate tidewater glaciers. We hypothesize that this difference is likely due to the lack of submarine melting in the case of lake-calving glaciers. Floating-tongue ice losses were evaluated in terms of overall mass balance and contribution to sea-level rise. The post-Little Ice Age collapse of Yakutat Icefield was driven in part by tidewater calving retreats of adjacent glaciers, the lake-calving retreat of Yakutat Glacier, a warming climate and by the positive feedback mechanisms through surface lowering.

Three spontaneous avalanches were observed in Lia, Longyearbyen, Svalbard, each occurring naturally under similar temperature conditions. Automatic measurements of temperature inside the snowpack led to examination of the triggering of avalanches in cold conditions following a rapid drop in temperature. The mechanical properties of ice depend on the slab temperature and I ask: could a rapid temperature change affect the mechanical properties differently considering a slab consisting of (1) rounded grains or (2) faceted grains? Snow is considered as a foam of ice crystals, and triaxial deformation tests are performed at constant strain rate to examine the influence of temperature and grain type on the mechanical properties. Although the snow densities in the two sample sets were almost identical, some differences due to grain type were observed. In particular, the set with faceted grain snow started to flow at higher stresses than the set with rounded grains.

The physical properties of snow are tied to its microstructure. Especially for the slow, plastic deformation of snow and firn, the crystal orientation is an important factor in addition to the geometry of the ice matrix. While micro-computed tomography measures the snow microstructure precisely, it gives no information about the orientation of the ice crystals. In this study, we applied a temperature gradient of 50 K m−1 to large blocks of undisturbed decomposed snow and sieved snow during 3 months. The mean temperature of the snow samples during the temperature gradient experiment was −20°C. Two closely spaced snow samples were taken before the experiment, then every week during the first month and afterwards every month. From each sampling, one sample was analyzed by micro-computed tomography and the other was used for thin sections. The orientation of the c-axis was measured in the thin sections using an automatic ice texture analyzer. Initial density was 30% higher in the sieved snow sample. Density and specific surface area evolved alike, while the fabric showed a different evolution between the two samples. The undisturbed snow evolved from a weak single-maximum fabric towards a weak girdle fabric, while the sieved sample showed no evolution. The undisturbed snow sample converged toward the sieved sample fabric after 6 weeks, but continued its evolution thereafter. We suggest that the main factor causing this different behavior is the difference in density and in pore size.

We present a comprehensive approach (including field data, remote sensing and an anisotropic ice-flow model) to characterize Halvfarryggen ice dome in coastal Dronning Maud Land, Antarctica. This is a potential drill site for the International Partnerships in Ice Core Sciences, which has identified the need for ice cores covering atmospheric conditions during the last few millennia. We derive the surface topography, the ice stratigraphy from radar data, and accumulation rates which vary from 400 to 1670 kg m−2 a−1 due to preferred wind directions and changing surface slope. The stratigraphy shows anticlines and synclines beneath the divides. We transfer Dansgaard–Johnsen age–depth scales from the flanks along isochrones to the divide in the upper 20–50% of the ice thickness and show that they compare well with the results of a full-Stokes, anisotropic ice-flow model which predicts (1) 11 ka BP ice at 90% of the ice thickness, (2) a temporally stable divide for at least 2700–4500 years, (3) basal temperatures below the melting point (−12°C to −5°C) and (4) a highly developed crystal orientation fabric (COF). We suggest drilling into the apices of the deep anticlines, providing a good compromise between record length and temporal resolution and also facilitating studies of the interplay of anisotropic COF and ice flow.

Historically, there has been considerable interest in establishing the relationship between wind-blown snow flux (Q) and wind speed. By monitoring the drift growth at snow fences in Arctic Alaska during three winters, we computed Q for 36 distinct transport events. Each fence was instrumented with depth sounders to measure deposition rates. The majority of events (31) occurred between November and February, despite winter extending from October to June. On average, five substantial snow deposition events (SDEs) occurred at each fence per winter. The mean flux during SDEs was 0.16, 0.19 and 0.29 kg s−1 m−1 at Barrow, Imnavait Creek and Franklin Bluffs, respectively, the differences in Q explained by the different wind regimes at the three sites. To place these flux measurements in perspective, we reviewed all previous experimental values of Q, with special attention to height and time over which the fluxes were measured. The new data help fill a range of wind speeds (12–18 m s−1) where prior results have been sparse. Combined, the full data define a diffuse cloud best represented by upper and lower bounding equations QU = 1.3 × 10−3w2.5 and QL = 3.3 × 10−9w6.5, where w is wind speed (>5 m s−1). We suggest that these bounds, rather than a single equation, provide the best way to estimate snow fluxes.

Ice shelves and ice tongues are dynamically coupled to their cavities. Here we compute normal modes (eigenfrequencies and eigenfunctions) of this coupled system using a thin-plate approximation for the ice shelf and potential water flow in the ice-shelf cavity. Our results show that normal modes depend not only on the ice-shelf parameters (length, thickness, Young’s modulus, etc.) but also on the cavity depth. The dominant eigenmodes are higher for ice shelves floating over deeper cavities; they are also higher for shorter ice shelves and ice tongues (<50 km long). The higheigenfrequency eigenmodes are primarily controlled by the ice flexure and have similar periods to sea swell. These results suggest that both long ocean waves with periods of 100–400 s and shorter sea swell with periods of 10–20 s can have strong impacts on relatively short ice shelves and ice tongues by exciting oscillations with their eigenfrequencies, which can lead to iceberg calving and, in some circumstances, ice-shelf disintegration.

Stable isotopes are a primary tool for inferring past temperature changes and atmospheric moisture variability from ice cores. A 33 m ice core representing the period 1850–2004 was retrieved from the Tanggula Mountains, central Tibetan Plateau (5743 m a.s.l.), in August 2005. Annual average stable isotope (δ18O, δD) values generally increase during the period, while the second-order parameter of deuterium excess (d-excess) generally decreases. High annual average d-excess values (18.2‰) throughout the ice core suggest a significant contribution of continental recycled moisture. d-excess values shift from relatively higher values during 1850–1940 to lower values since the 1940s. Annual isotope values and reconstructed accumulation are compared with climate indices, local station temperature records and northern India monsoon precipitation. Significant correlation is observed between δ18O and the Southern Oscillation, NINO3.4 and Dipole Mode indices. Annual average d-excess values revealed a significant negative correlation with the Dipole Mode index. Results suggest a relatively greater contribution of westerly-dominated continental moisture prior to the 1940s and an increase in the contribution of moisture evaporated under more humid conditions since the 1940s.

We present a new method for extracting the direction of surface flow for ice sheets, based on the detection of flow-induced features that are visible in satellite imagery. The orientation of linear features is determined using a Radon transform and only requires a single image. The technique is demonstrated by applying it to the RADARSAT mosaic of Antarctica, over the Lambert Glacier–Amery Ice Shelf region of East Antarctica. Comparisons with both existing flow-direction fields and traced streamlines over the same area provide an evaluation of the method. We also illustrate its application to Landsat 7 imagery.

A new 10 year surface mass balance (SMB) record of Hurd and Johnsons Glaciers, Livingston Island, Antarctica, is presented and compared with earlier estimates on the basis of local and regional meteorological conditions and trends. Since Johnsons is a tidewater glacier, we also include a calving flux calculation to estimate its total mass balance. The average annual SMB over the 10 year observation period 2002–11 is −0.15 ± 0.10 m w.e. for Hurd Glacier and 0.05 ± 0.10 m w.e. for Johnsons Glacier. Adding the calving losses to the latter results in a total mass balance of −0.09 ± 0.10 m w.e. There has been a deceleration of the mass losses of these glaciers from 1957–2000 to 2002–11, which have nearly halved for both glaciers. We attribute this decrease in the mass losses to a combination of increased accumulation in the region and decreased melt. The increased accumulation is attributed to larger precipitation associated with the recent deepening of the circumpolar pressure trough, while the melt decrease is associated with lower summer surface temperatures during the past decade.

We present an analysis of temporal trends in ∼55 000 avalanches recorded between 1946 and 2010 in the French Alps and two north/south subregions. First, Bayesian hierarchical modelling is used to isolate low-, intermediate- and high-frequency trends in the mean avalanche occurrence and runout altitude per year/winter. Variables are then combined to investigate their correlation and the recent evolution of large avalanches. Comparisons are also made to climatic and flow regime covariates. The results are important for risk assessment, and the development of new high-altitude climate proxies. At the entire French Alps scale, a major change-point exists in ∼1978 at the heart of a 10 year period of high occurrences and low runout altitudes corresponding to colder and snowier winters. The differences between this change-point and the beginning/end of the study period are 0.1 avalanche occurrences per winter and per path and 55 m in runout altitude. Trends before/after are well correlated, leading to enhanced minimal altitudes for large avalanches at this time. A marked upslope retreat (80 m for the 10 year return period runout altitude) accompanied by a 12% decrease in the proportion of powder snow avalanches has occurred since then, interrupted from about 2000. The snow-depth and temperature control on these patterns seems significant (R = 0.4–0.6), but is stronger at high frequencies for occurrences, and at lower frequencies for runout altitudes. Occurrences between the northern and southern French Alps are partially coupled (R∼0.4, higher at low frequencies). In the north, the main change-point was an earlier shift in ∼1977, and winter snow depth seems to be the main control parameter. In the south, the main change-point occurred later, ∼1979–84, was more gradual, and trends are more strongly correlated with winter temperature.

An attempt is made to obtain and quantify the mechanical properties of two common types of seasonal snow on the ground. Different samples of natural snow whose metamorphism had stabilized (such as would remain on a road throughout winter in a cold, snowy area) were gathered and tested using mesoscale indentation tests (metrics on the order of mm to cm). Results from the stress vs displacement curves from indentation indicated that (1) first peak strength decreased, according to a power law, with increasing indenter size and was not affected by snow average grain size, (2) plateau strength decreased with increasing indenter size, and snow compaction strength might be calculated from these data, and (3) mean energy absorption density during indentation was independent of indenter size in some size ranges, and decreased with increasing indenter size in other size ranges.

With mass loss from the Greenland ice sheet accelerating and spreading to higher latitudes, the quantification of mass discharge in the form of icebergs has recently received much scientific attention. Here we make use of very low-frequency (0.001–0.01 Hz) seismic data from three permanent broadband stations installed in the summers of 2009–10 in northwest Greenland in order to monitor local calving activity. At these frequencies, calving seismograms are dominated by a tilt signal produced by local ground flexure in response to fjord seiching generated by major iceberg calving events. A simple triggering algorithm is proposed to detect calving events from large calving fronts with potentially no user interaction. Our calving catalogue identifies spatial and temporal differences in calving activity between Jakobshavn Isbræ and glaciers in the Uummannaq district ∼200 km to the north. The Uummannaq glaciers show clear seasonal fluctuations in seiche-based calving detections as well as seiche amplitudes. In contrast, the detections at Jakobshavn Isbræ show little seasonal variation, which may be evidence for an ongoing transition to winter calving activity. The results offer further evidence that seismometers can provide efficient and inexpensive monitoring of calving fronts.

Ice cores from cold Alpine glaciers may provide unique paleoclimate information from non-polar latitudes. We explore the three-dimensional internal age distribution of the small cold glacier saddle (Colle Gnifetti, Monte Rosa, Italy/Switzerland) to compare the age/depth relations from four local deep ice cores. Tracking isochronous reflection horizons detected by ground-penetrating radar (GPR) among the core locations reveals consistent dating up to 80 years BP. This approach is confined to recent ages, due to the lack of clear reflections below the firn/ice transition. We attempt to overcome this limitation by including a two-dimensional flow model adapted to the GPR-derived surface accumulation and ice thickness distribution. Modeled and GPR isochrones are compared, indicating agreement in shape but featuring a potential offset of 0–3.5 m. The modeled isochrones are interpolated to the core array with ages assigned according to the ice-core datings. The resulting age distribution is consistent up to 110 years BP, with age uncertainties increasing from 7 to >80 years in the lower half of the ice. This combination of methods is novel for Alpine sites and may be adapted for spatial extrapolation of ice properties other than age.