This paper presents the impact of model resolution on the simulated wind speed, drifting snow climate and surface mass balance (SMB) of Terre Adélie and its surroundings, East Antarctica. We compare regional climate model simulations at 27 and 5.5 km resolution for the year 2009. The wind speed maxima in Terre Adélie and the narrow glacial valleys of Victoria Land are better represented at 5.5 km resolution, because the topography is better resolved. Drifting snow sublimation is >100 mm a-1 in regions with high wind speeds. Our results indicate a strong feedback between topography, wind gradients and drifting snow erosion. As a result, SMB shows much more local spatial variability at 5.5 km resolution that is controlled by drifting snow erosion, whereas the large-scale SMB gradient is largely determined by precipitation. Drifting snow processes lead to ablation in the narrow glacial valleys of Victoria Land. The integrated SMB equals 86 Gt. Although wind climate, drifting snow processes and SMB variability are better represented at 5.5 km, the area-integrated SMB is not significantly different between the simulations at 27 and 5.5 km. A horizontal resolution of 27 km is sufficient to realistically simulate ice-sheet wide SMB.

Since 2002, the Envisat radar altimeter has measured the elevation of the Antarctic ice sheet with a repeat cycle of 35 days. This long and regular time series is processed using an along-track algorithm to depict in detail the spatial and temporal pattern of elevation change for the whole ice sheet. We use this dataset to examine the spatial and temporal pattern of Pine Island Glacier (PIG) thinning and compare it to the neighbouring glaciers. We also examine additional areas, especially in East Antarctica whose mass balance is poorly known. One advantage of the finer along-track spacing of measurements is that it reveals places of dynamic thinning in regions of rapid ice flow. We observe the acceleration of thinning on PIG. Over the entire basin, the volume loss increased from 7 km3 a-1 during 2002−06 to ~48 km3 a-1 during 2006-10. We also observe accelerated thinning on the lower tens of kilometres of Thwaites Glacier, with a mean thinning of 0.18 m a-1 over its entire basin during our observation period. We confirm the dynamic thinning of Totten Glacier but we do not detect significantly accelerated thinning on any glacier elsewhere than on the coast of the Amundsen Sea.

We present the design and first results from two experiments using a wireless subglacial sensor system (WiSe) that is able to transmit data through 2500 m thick ice. Energy consumption of the probes is minimized, enabling the transmission of data for at least 10 years. In July 2010 the first prototype of the system was used to measure subglacial pressure at the base and a temperature profile consisting of 23 probes in two 600 m deep holes at Russell Glacier, a land-terminating part of the West Greenland ice sheet near Kangerlussuaq. The time series of subglacial pressure show very good agreement between data from the WiSe system and the wired reference system. The wireless-measured temperature data were validated by comparison with the theoretical decrease of melting point with water pressure inside the water-filled hole directly after installation. To test the depth range of the WiSe system a second experiment using three different probe types and two different surface antennas was performed inside the 2537 m deep hole at NEEM. It is demonstrated that, with the proper combination of transmission power and surface antenna type, the WiSe system transmits data through 2500 m thick ice.

Moraine dams can be inherently unstable, but effective assessment strategies remain poorly identified. We integrate electrical resistivity tomography (ERT) with electrical self-potential (SP) and lake-level measurements to investigate the structure of, and hydrological processes within, a moraine-dam complex adjacent to Miage glacier, Italy. This complex separates two meltwater lakes characterized by an efficient subterranean hydraulic connection. Our ERT data reveal a continuous free surface within the complex, whose morphology reflects the topography of the moraine complex akin to unconfined groundwater aquifers. SP data were corrected for spatial changes in the thickness of the upper unsaturated layer using principles of electrography. The residual streaming-potential map is consistent with Darcian flow of lake waters through the moraine complex, characterized by a negative-to-positive potential change from <-30 mV to >+70 mV. These electrical signatures are consistent with those generated by water seepage through earth dams in various non-glacial settings. Integrated electrical geophysical methods thus provided an inexpensive and unobtrusive evaluation of the hydrological properties of and processes within the moraine complex. Since spatio-temporal patterns of subsurface water flow critically affect the strengths of moraine sediments, such methods promise to be powerful in assessing the long-term stability of moraine-dammed glacial lakes.

In order to apportion the dust sources of mountain glaciers in western China, the Sr-Nd isotopic compositions of insoluble particles were determined in snow samples collected from 13 sites. The combined plot of 87Sr/86Sr and εNd(0) demonstrates a distinctive geographic pattern over western China, which can be classified into three regions from north to south. Samples from the Altai mountains show the lowest 87Sr/86Sr ratio and the highest εNd(0) value, similar to the data of deserts in the north of China such as the Gurbantunggut desert. Samples from the southern Tibetan Plateau (TP) and Himalaya show the highest 87Sr/86Sr and lowest εNd(0) values, resembling the local and regional dust sources found in the southern TP and Himalaya-India region. Samples from the Tien Shan and northern Tibetan Plateau exhibit intermediate 87Sr/86Sr and εNd(0) values, similar to the data reported for the northern margin of the TP (NM_TP). However, three sampling sites, JMYZ (Jiemayangzong) located in the Himalaya and ZD (Zadang) and YL (Yulong) located in the southeast TP, presented distinctive Sr-Nd isotopic signatures typical of the NM_TP, suggesting potential long-range and high-altitude dust transport across the TP.

The processes that form intraglacial lakes are poorly understood because of the difficulty in detecting and assessing such hidden lakes. Extensive geophysical surveys were performed between 2007 and 2010 in order to reassess the risk of an outburst flood from Glacier de Tete Rousse, French Alps, where outburst flooding from an intraglacial lake caused 175 fatalities in 1892. Our geophysical survey combined ground-penetrating radar measurements and nuclear magnetic resonance imaging. We found a subglacial water-filled reservoir with a volume of 55 000 m3. Artesian outpourings occurred when the subglacial cavity was reached by two borehole drillings, indicating that the hydrostatic water pressure exceeded the ice pressure at the bottom of the cavity. On the basis of these geophysical and glaciological findings, we warned the public authorities in July 2010 of the risk facing the 3000 inhabitants downstream of the glacier. The subglacial reservoir was drained artificially. This example demonstrates how geophysical surveys can be used to detect this type of hazard when it is suspected, in particular when no hydraulic outlet from the snout exists. Numerous ice temperature measurements have shown that the tongue of this glacier is cold-based. This thermal regime could explain the accumulation of water in this glacier.

Global warming is causing widespread glacier retreat, with small glaciers disappearing. We investigate changes in glaciers over the western Lenglongling mountains, located in the northeastern margin of the Tibetan Plateau. Glacier extent over the western Lenglongling mountains is estimated by comparing digitized glacier outlines obtained from aerial photographs and satellite imagery. These results suggest that all 179 glaciers in the western Lenglongling mountains shrunk between 1972 and 2007. The total area loss was ~24.4 km2, accounting for ~28.3% (0.81% a-1) of the glacierized area in 1972. The average area retreat rates differ over different time intervals: they are approximately 0.68, 0.90, 0.77 and 0.56 km2 a-1 over the periods 1972-95,1995-99,1999-2002 and 2002-07, respectively. Based on analysis of meteorological data, glacier shrinkage in the study area can probably be attributed to the increase in air temperature. Furthermore, the smaller glaciers display a higher shrinkage rate than larger glaciers, and glaciers on southwest-facing slopes appear to retreat faster than those on northeast- facing slopes.

We propose an infinite-dimensional adjoint-based inexact Gauss-Newton method for the solution of inverse problems governed by Stokes models of ice sheet flow with nonlinear rheology and sliding law. The method is applied to infer the basal sliding coefficient and the rheological exponent parameter fields from surface velocities. The inverse problem is formulated as a nonlinear least-squares optimization problem whose cost functional is the misfit between surface velocity observations and model predictions. A Tikhonov regularization term is added to the cost functional to render the problem well-posed and account for observational error. Our findings show that the inexact Newton method is significantly more efficient than the nonlinear conjugate gradient method and that the number of Stokes solutions required to solve the inverse problem is insensitive to the number of inversion parameters. The results also show that the reconstructions of the basal sliding coefficient converge to the exact sliding coefficient as the observation error (here, the noise added to synthetic observations) decreases, and that a nonlinear rheology makes the reconstruction of the basal sliding coefficient more difficult. For the inversion of the rheology exponent field, we find that horizontally constant or smoothly varying parameter fields can be reconstructed satisfactorily from noisy observations.

This study calculates area, volume and elevation changes of two glaciers on James Ross Island, Antarctica, during the period 1979-2006. Davies Dome is a small ice cap. Whisky Glacier is a valley glacier. Ground-penetrating radar surveys indicate ice thickness, which was used for calculations of the bed topography and volume of both glaciers. Maximum measured ice thicknesses of Davies Dome and Whisky Glacier are 83 ± 2 and 157 ± 2 m, respectively. Between 1979 and 2006, the area of the ice cap decreased from 6.23 ± 0.05 km2 to 4.94 ± 0.01 km2 (-20.7%), while the area of the valley glacier reduced from 2.69 ± 0.02 km2 to 2.40 ± 0.01 km2 (-10.6%). Over the same period the volume of the ice cap and valley glacier reduced from 0.23 ± 0.03 km3 to 0.16 ± 0.02 km3 (-30.4%) and from 0.27 ± 0.02 km3 to 0.24 ± 0.01 km3 (-10.6%), respectively. The mean surface elevation decreased by 8.5±2.8 and 10.1 ±2.8m. The average areal (~0.048-0.011 km2a-1) and volumetric (~0.003−0.001 km3 a-1) changes are higher than the majority of other estimates from Antarctic Peninsula glaciers.

Dye-trace breakthrough curves (BTCs) that increase in velocity and decrease in dispersivity through a melt season have been interpreted as indicating a switch from a distributed to a conduit subglacial drainage system, but this interpretation has not been validated in glaciers where the drainage system configuration was independently known. To test if processes other than a change in the configuration of the subglacial drainage system could produce similar BTCs, we measured BTCs from a persistent, mapped subglacial conduit beneath Rieperbreen, Svalbard, which lacks a distributed system because it is frozen to its bed. This conduit produced slow and highly dispersed BTCs early in the melt season when meltwater delivery rates were low, and fast and sharply peaked BTCs after the snowpack had retreated past the injection moulin. At Rieperbreen, the seasonal evolution of BTCs was controlled by decreases in conduit roughness as increased rates of meltwater delivery increased the relative submergence depths of rocks on the conduit floor. Because seasonal changes in roughness can produce slow and highly dispersed BTCs, dye-tracing studies may not be capable of uniquely identifying subglacial drainage system configurations. As a result, conduits may form earlier in melt seasons than previously recognized.

Subglacial conduit systems are thought to consist of dendritic networks that exist at lower pressure than distributed systems and have locations that are determined by theoretical hydraulic potential. On glaciers with moulins, however, meltwater is delivered to glacier beds at discrete points, violating assumptions of uniform recharge needed to calculate potential. To understand how moulins affect subglacial conduit hydrology, we used speleological techniques to map 0.4 km of subglacial conduit at the base of a moulin in Hansbreen, Svalbard, and compared our observations with theoretical predictions. The conduit began in an area predicted to lack drainage, crossed equipotential contours at oblique rather than right angles and was locally anastomotic rather than dendritic. We propose moulin locations, which are determined by the locations of supraglacial streams and crevasses, control locations of subglacial recharge. Because conduits have no direct causal relationship with gradients in effective pressure, this recharge can form conduits in areas of glacier beds that may not be predicted by hydraulic potential theory to have conduits. Recharge by moulins allows hydraulic head to increase in conduits faster and to higher values than in adjacent distributed systems, resulting in an increase rather than a decrease in glacier sliding speeds above subglacial conduits.

Snow grain-size characterization, its vertical and temporal evolution is a key parameter for the improvement and validation of snow and radiative transfer models (optical and microwave) as well as for remote-sensing retrieval methods. We describe two optical methods, one active and one passive shortwave infrared, for field determination of the specific surface area (SSA) of snow grains. We present a new shortwave infrared (SWIR) camera approach. This new method is compared with a SWIR laser- based system measuring snow albedo with an integrating sphere (InfraRed Integrating Sphere (IRIS)). Good accuracy (10%) and reproducibility in SSA measurements are obtained using the IRIS system on snow samples having densities greater than 200 kg m-3, validated against X-ray microtomography measurements. The SWIRcam approach shows improved sensitivity to snow SSA when compared to a near-infrared camera, giving a better contrast of the snow stratigraphy in a snow pit.

Changes in area of 30 small glaciers (mostly <1 km2) in the northern Polar Urals (67.568.25° N) between 1953 and 2000 were assessed using historic aerial photography from 1953 and 1960, ASTER and panchromatic Landsat ETM+ imagery from 2000, and data from 1981 and 2008 terrestrial surveys. Changes in volume and geodetic mass balance of IGAN and Obruchev glaciers were calculated using data from terrestrial surveys in 1963 and 2008. In total, glacier area declined by 22.3 ± 3.9% in the 1953/60-2000 period. The areas of individual glaciers decreased by 4-46%. Surfaces of Obruchev and IGAN glaciers lowered by 22.5 ± 1.7 m and 14.9 ± 2.1 m. Over 45 years, geodetic mass balances of Obruchev and IGAN glaciers were -20.66 ± 2.91 and -13.54 ± 2.57 mw.e. respectively. Glacier shrinkage in the Polar Urals is related to a summer warming of 1°C between 1953-81 and 1981-2008 and its rates are consistent with other regions of northern Asia but are higher than in Scandinavia. While glacier shrinkage intensified in the 1981-2000 period relative to 1953-81, increasing winter precipitation and shading effects slowed glacier wastage in 2000-08.

Glacier mass-balance parameters such as the equilibrium-line altitude (ELA) play an important role when working with large glacier samples. While the number of observational mass-balance series to derive such parameters is limited, more and more modeled data are becoming available.Here we explore the possibilities of analyzing such 'synthetic' mass-balance data with respect to mass-balance parameters. A simplified energy-balance model is driven by bias-corrected regional climate model output to model mass-balance distributions for 94 glaciers in the Swiss Alps over 15 years. The modeling results in realistic interannual variability and mean cumulative mass balance. Subsequently model output is analyzed with respect to 18 topographic and mass-balance parameters and a correlation analysis is performed. Well-known correlations such as for ELA and median elevation are confirmed from the synthetic data. Furthermore, previously unreported parameter relationships are found such as a correlation of the balance rate at the tongue with the accumulation-area ratio (AAR) and of the glacier elevation range with the AAR. Analyzing modeled data complements in situ observations and highlights their importance: the small number of accurate mass-balance observations available for validation is a major challenge for the presented approach.

Snow avalanches often form levees and en-echelon shear planes in the run-out zone. We describe the formation of these depositional structures using a simple model that accounts for the role of granular fluctuations in avalanche motion. A mathematical feature of this model is the existence of a bifurcation saddle point, describing how granular fluctuations control the avalanche velocity in the runout zone. The saddle point discriminates between a flowing and stopping regime and defines the physical boundary between the flow and non-flow regions of the avalanche, i.e. the location of shear planes in the avalanche deposits. The formation of a shear plane depends on the interplay between terrain slope and avalanche mass flux, which varies from avalanche head to tail. Levees can form immediately at the avalanche front or, for steep slopes and low mass fluxes, at the avalanche tail. At ravine and gully shoulders the mass flux is restricted, thus initiating levee formation. We find that the levee lines are parallel to the flow direction when the mass flux is constant; en-echelon shear lines occur when the mass flux is decreasing. We test the model using several case studies where we have accurate laser scans of avalanche deposits. Our results suggest that avalanche flow parameters can be determined from simple levee measurements or, conversely, formation of levees and flow fingers can be predicted once the parameters governing the granular fluctuations are known.

A surface roughness measurement system for snow is presented. It is based on a background board with scales on the edges and a digital camera. Analysis software is developed for automatic processing of images to produce calibrated profiles. The image analysis and calibration was fully automatic in >99% of the studied cases. In the others, the intensity adjustment or board detection needed manual intervention. Profile detection, control point picking and calibration always worked autonomously. The accuracy of the system depends on the photographing configuration, and is typically of the order of 0.1 mm vertically and 0.04 mm horizontally. The method tolerates relatively well cases of snowfall, traces of wiping the black background dry, uneven shading, reflected sunlight, reflected flash light, litter on the snow surface and a tilted plate. The repeatability of the system is at least 1%.

When an ice-flow model is constrained by data that exist over only a section of an ice sheet, it is computationally advantageous to limit the model domain to only that section. For example, a limited domain near an ice-core site might cross an ice divide, and have no termini. Accurately calculating ice-sheet evolution in response to spatial and temporal variations in climate and ice flow depends on accurately calculating the transient ice flux crossing the limited-domain boundaries. In the absence of information from outside the limited domain, this is an ill-posed problem. Boundary conditions based only on information from inside the limited domain can produce ice-sheet evolution incompatible with the full ice sheet within which we suppose it to exist. We use impulse-response functions to provide boundary values that are informed by the external ice sheet, without conventionally 'nesting' the limited domain in a full ice-sheet model. Evolution within a limited domain can then be consistent with evolution of boundary conditions is designed for future use in affected the limited domain can be inferred from the full ice sheet. Our treatment of limited-domain an inverse problem in which external changes that data from within the limited domain.