We present results from a comprehensive field study carried out near Barrow, Alaska, USA, designed to characterize local- to intermediate-scale sea-ice processes in the Arctic coastal zone of central importance to the annual cycle and evolution of the coastal sea ice. Included in this are the behavior of the snow cover of the ice and adjacent tundra and lake system; concurrent studies of mass balance of the sea ice and lake ice; interaction of shortwave radiation with the shore-fast ice and the adjacent land surfaces; evolution of the area coverage and distribution of the various surface types; and the resulting regional albedo values. Maximum snow depths decreased during 2000–02 from 0.38 m to 0.26 m. Ice-melt rates in 2001 were 0.05 and 0.028md–1 at the top and bottom of the sea ice respectively, two to three times larger than observations from the central Arctic. Detailed surface results combined with aircraft photography were used to calculate regional albedos for the late spring and early summer of 2001. Values ranged from 0.8 for all cold snow-covered surfaces to approximately 0.4 for melting sea ice and lake ice vs 0.18 for bare tundra. Regional and surface-based values of cumulative shortwave radiation entering the ice were consistent, indicating that albedo sampling on a scale of 200m can provide a useful representation for regional sea-ice albedo.

Two snow and ice cores from the Rennick Glacier area, Antarctica (study area center point lat 71°15ˈS, long 162°30ˈE) were analyzed for the chemical species: chloride, sodium, reactive silicate, sulfate and nitrate. Core E10 (6.35 m) was taken from Evans Névé, a large accumulation basin at the head of Rennick Glacier. Core M1 (4.35 m) was extracted from the accumulation zone on the central plateau of the Morozumi Range, a small mountain massif bordering Rennick Glacier. Cores E10 and M1 span the time periods from 1929 to 1981 and from 1971 to 1981, respectively, as dated using seasonal variations in chloride (E10) and sulfate (M1) concentrations. An estimated net balance of 50 kg m−2 a−1 was derived for site E10 and of 182 kg m−2 a−1 for site M1. The difference in net mass balance may be explained by elevational differences (M1 1400 m a.s.1., E10 2305 m a.s.1.). Recent (1973 to 1980) increases in sodium, silicate and sulfate at site E10 may be linked to decreases in Antarctic pack-ice extent (Kukla and Gavin 1981) for the same period.

The depth, density, load and isotopic (δ18O) composition of the snow cover on pack-ice floes were measured in late austral summer 1992 in the eastern Ross, Amundsen and western Bellingshausen Seas. Snow-density values commonly exceeded 350 kg m-3 and some were as high as 500 kg m-3. The densification of the snow occurs quickly and is attributed to a windy environment. The high density and sometimes considerable depth of the snow on the floes accounts for loads of as much as 700 kg m-2 and resultant sea-water flooding of the underlying sea ice. Lower mean δ18O values in the Ross/Amundsen Seas snow cover suggest that the region might have a cooler climate than the Bellingshausen Sea region. Snow depths on floes in the Bellingshausen Sea region were lower than those in the Ross/Amundsen Seas region, because the Bellingshausen Sea floes were first-year ice. Possible annual units in the isotope profiles of snow, as much as 2m deep, indicate that floes in the Ross/Amundsen Seas region were 2-3 years old.

In 1968 an ice core 2164 m long was recovered from Byrd station in West Antarctica. About 2000 tephra layers were observed in the core and have been differentiated into ash and dust bands according to the grain size and concentration of particles in the layers. Mount Takahe, a local volcano in Marie Byrd Land, Antarctica is the probable source.

Detailed examinations of the particle morphology, composition and ice chemistry associated with some of the tephra layers have led to the conclusion that the eruptions which produced the layers were probably hydrovolcanic. Melted glacier ice is considered the most likely source of the water involved in the eruptions.

Processes associated with hydrovolcanism such as particle aggregation (causing premature deposition of fine particles), rapid conversion of sulfur dioxide to sulfuric acid (in the presence of abundant moisture) and scavenging of acid droplets by the fine dust particles are inferred to have taken place. Such processes would greatly reduce the atmospheric residence time of the eruptive products and thus their atmospheric and climatic impact.

The deep ice-sheet coring (DISC) drill developed by Ice Coring and Drilling Services (ICDS) under contract with the US National Science Foundation requires a drill cable capable of transmitting high amounts of electrical power as well as high rates of data. The DISC cable was designed and manufactured by the Rochester Corporation to core ice to depths of 4000 m. In addition to the steel strength members to support the drill, the cable has copper wires for conducting electrical power for the drill sonde cutter, pump motors and the sonde electronics and an optical fiber core for data transmission. The outer steel layers are filled with a special compound to minimize fluid penetration of the cable.

Beneath Ürümqi Glacier Νo. 1, there is an ice-laden till layer which is more than 10 m thick near the terminus. The 0°C isotherm is generally at some depth below the glacier sole and lies within the bedrock below the ice-laden till layer near the terminus. Thus the glacier is entirely cold and impermeable, except for a thin snow-firn layer at its surface and some crevassed areas. Meltwater drains off mainly by surface channels, assisted by subglacial conduits. Four flow mechanisms have been identified in the glacier. They are ice deformation, bed deformation, shear faulting, and sliding over the bed. At the terminus and along the margins, bed deformation can provide a significant contribution to the overall surface motion. Bed deformation consists of creep and discontinuous slip. However, creep experiments on samples taken from the ice-laden till layer provide no positive indication that this layer deforms more easily than clean ice. Discontinuous slip thus may provide the major contribution to bed deformation.

Accounting for isostasy in glaciological models has always been a necessity but these models mostly use very simple parameterizations (Le Meur and Huybrechts, 1996). The need for more realistic isostatic parameterizations rapidly became apparent, especially in the treatment of bedrock-sensitive issues such as the grounding-line migration (Huybrechts, 1990a, b). To this end, a rather sophisticated Earth model, avoiding most of the common assumptions, has been developed and is presented here. The two key groups of parameters, to which the model is most sensitive, are the Earth properties and the rheological law used for the mantle. The aim of this paper is first to justify the use of Maxwell rheology for the mantle and then to tune the most sensitive Earth parameter, namely the mantle viscosity, in order to match the numerous present-day uplift data over Fennoscandia. So, in the first instance, a short review of the different available rheologies is presented and discussed. The visco-elastic theory, as well as the mathematical background used in the present model, is also briefly sketched. Secondly, a glacial scenario over Fennoscandia served as an input for the model in a calibration test on the mantle-viscosity values. The degree of agreement of the model outputs with the present-day measurements gives a reference set of Green functions, to which one can reasonably refer when modelling the isostatic response over areas where such a control is not possible (Le Meur and Huybrechts, 1996). Finally, a closer look to the time-dependent surface displacements will confirm the ability for the model to reproduce correctly the main postglacial rebound characteristic features.

A systematic programme of side-scan sonar and plumb- line soundings was carried out in the Weddell Sea area in 1985 to measure the under-water sides of ice shelves and icebergs. From these observations the following model is suggested for the evolution of the ice front:

• (1) Initial stage: fracturing of the ice shelves takes place along smooth, curvi-linear segments with vertical faces.

• (2) Formative stage: the freshly formed vertical face is eroded both by wave and swell action around the water line, by small calvings from the undercut, overhanging subaerial face, and by submarine melting. The melting has a minimum at 50–100 m depth, and increases with depth to a rate of around 10 m a−1 at 200 m, This is about twice the rate of erosion at the water line. The variation in melting with depth results from a combination of summer melting by near-surface water, and year-round melting by water masses that are increasingly warmer than the pressure melting-point with depth.

• (3) Mature stage: this stage is reached after a few years of exposure. The backward erosion of the face leads to a shape with a prominent under-water “nose” with a maximum projection to more than 50 m at 50–100 m depth. The ramp above this slopes upwards to meet the vertical wall about 5 m below the water line. The ice below the nose is melted back beyond the above-water face. There is no net buoyancy and ice shelves at this mature stage are generally not up-warped at the front.

Position data from an Argos-tracked buoy deployed in the southern Weddell Sea in the austral summer of 1986 are analysed to determine important time-scales of variation of sea-ice motion in the seasonal sea-ice zone. Quality control and pre-processing of raw buoy data are discussed. Processed position data are subjected to time- and frequency-domain analyses. These highlight the importance of diurnal and semi-diurnal periodicities in the buoy motion. These preferred periodicities are associated with tidal forcing rather than wind forcing or inertial oscillations. Periodograms of the longitudinal component of buoy motion indicate that the power of the 24 h tidal component drops dramatically around day 130 in 1986. The possible causes of this are discussed and it is concluded that internal resistance within the sea-ice field may have increased at that time.

Sub-grid variability of the snow cover is an important issue with regard to catchment runoff or mesoscale meteorological modeling. Here, an evaluation is presented of spatial snow measurements conducted on 5 days in winter 1998/99 and 2 days in winter 1999/2000 in a 0.7 km2 Swiss pre-Alpine catchment. Snow-depth data were analyzed with two different linear regression models, one including altitude, terrain slope, terrain aspect and canopy density, and one using altitude and simple land-use indicators. For the single measurement date/the first model was somewhat superior to the indicator model. The error term of the regression models showed only weak spatial dependence. Finally, a time-space linear regression model describing both the temporal development and the spatial distribution of the snow cover was fitted with the measurements of the first winter and tested with measurements of the second winter. The validation showed a satisfactory match between measurements and models in late December, but a slight overestimation of the measurements by the models in early April. In view of the models’ability to reproduce the snow-depth patterns satisfactorily at this rather detailed scale, it was concluded that such regression models might be a suitable tool to treat sub-grid variability of snow depth in larger-scale models.

Measurements and observations by others indicate that a potential slab avalanche consists of a relatively cohesive slab of snow overlying a thin weak layer that coniains flaws where locally the shear stress from the overburden is not fully supported. Under favorable conditions, snow will shear strain-soften, which provides the basis for applying a slip-weakening model to examine the size of flaw needed to initiate sub-critical crack propagation along the weak layer. Using typical values for snow properties, the model predicts sub-critical crack growth can initiate from a relatively small flaw well before the shear stress from the overburden approaches the peak shear strength at tin-bed. The occurrence of small flaws or imperfections in the basal layer would explain field measurements which usually indicate that avalanching occurs before the applied shear stress exceeds the shear strength at the basal layer.

Widespread slab-avalanche activity often increases significantly soon after the onset of rain on new snow. Measurements of temperature and mechanical properties show that only the upper 0.15 m or less of the slab has been altered at the time of avalanching; alterations at the sliding layer have not yet been detected. Results from the slip-weakening model indicate that the rain-induced alterations would reduce the size of flaw needed to initiate sub-critical crack growth by 10–20%. The observations and model results show clearly the importance of the slab properties; it is evident that both the slab and the weak layer act together to control slope stability. A further implication is that the stability of freshly deposited snow is often close to critical, because a relatively small surface perturbation is often sufficient to cause avalanching. This is not surprising, because it is well known from field observations that new snow on slopes should be treated with caution.

Antarctic subglacial lakes are of great interest to the science community. These systems are considered to be in pristine condition, potentially harbouring an environment containing undisturbed sedimentary sequences and ecosystems adapted to cold oligotrophic environments in the absence of sunlight. Gaining access to subglacial lakes presents major technological challenges. To comply with conventions covering the exploration of pristine Antarctic environments, access should be conducted so the lake is not contaminated in any way. Consequently, all equipment to enter the lake must be sterile and the entrance should isolate the lake from the external environment. Currently, clean access to these environments is achieved using a hot-water drilling system. Differences between the hydraulic pressure head of the lake and the glacial surface result in a section of the borehole being air-filled. It is imperative that this section is disinfected prior to introducing any sampling equipment. This paper describes the design process involved in rapid-prototyping an ultraviolet (UV) disinfection reactor for achieving this goal. Considerations such as UV output, physical constraints, temperature management, and deployment procedures are assessed. We present a design that addresses these considerations.

Agricultural irrigation is an important use of melt water in the Karakoram Range of Pakistan; indeed all crop cultivation relies on melt water from small glaciers and/or snow and ice patches in the zone above 3500 m. Inhabitants of Hopar settlement utilize run-off from a cirque-shaped basin covering about 11.5km2 between 3600 and 4900 m a.s.l. to irrigate 280 ha of cultivated terraces in the altitudes 2500–3000 m. The characteristics of discharge from this basin require specific adaptions to be made by irrigators. In particular, access, turbulent flow, water temperature and sediment load are problematic, although water allocation is not an important concern because supply exceeds demand for most of the local growing season. Supply characteristics are outlined in the paper and are related to features of the indigenous irrigation system.

A three-dimensional dynamic, thermodynamic ice-sheet model has been developed to simulate the past, present, and future behaviour of the Antarctic ice sheet. The present ice velocities depend on the deep ice temperatures which in turn depend on the past changes of the ice sheet, including surface temperature, accumulation rate, and ice thickness. The basal temperatures are also strongly dependent on the geothermal heat flux. The model has therefore been used to study the effect on the basal temperatures, of changes to the geothermal heat flux, as well as the past changes of surface temperature and accumulation rate based on results obtained from the Vostok deep ice core. The model is also used to compute the distribution of surface velocity required to balance the present accumulation rate and the dynamics velocity based on the stress, temperature, and flow properties of ice, for the internal deformation, plus a component due to ice sliding. These velocities are compared to observed surface velocities in East Antarctica to assess the state of balance and the performance of the dynamics formulation.

Clouds play an important role in the Arctic surface radiative budget, impacting the seasonal evolution of Arctic sea-ice cover. We explore the large-scale impacts of springtime and early summer (March through July) cloud and radiative fluxes on sea ice by comparing these fluxes to seasonal ice volume losses over the central Arctic basin, calculated for available observational years 2004–2007 (ICESat) and 2011–2017 (CryoSat-2). We also supplement observation data with sea-ice volume computed from the Pan-Arctic Ice–Ocean Modeling and Assimilation System (PIOMAS) during summer months. We find that the volume of sea ice lost over the melt season is most closely related to observed downwelling longwave radiation in March and early summer (June and July) longwave cloud radiative forcing, which together explain a large fraction of interannual variability in seasonal sea-ice volume loss (R2 = 0.71, p = 0.007). We show that downwelling longwave fluxes likely impact the timing of melt onset near the sea-ice edge, and can limit the magnitude of ice thickening from March to April. Radiative fluxes in June and July are likely critical to seasonal volume loss because modeled data show the greatest ice volume reductions occur during these months.

Summer profiles of sea-water temperature, salinity and flow were obtained on George VI Ice Shelf near its northern ice front. At each depth, temperature salinity and density show little variation between sites. Their respective variation to 250 m depth confirms a linear temperature-salinity dependence. This is the first place in the world where observations confirm precisely the form of the T-S diagram predicted for fresh ice melting in sea-water. Both tidal and residual flow are small, except at the western margin of the ice front, where a strong outflow is concentrated immediately beneath the ice shelf. The observations lead to a simple circulation model for the ice-shelf regime. Warm Deep Water flows southwards into George VI Sound, replacing the colder water that spreads northwards in the surface outflow. Thermohaline exchanges beneath the ice shelf determine the salinity profile, which itself provides evidence of upwelling. Estimates can be made of the basal melt rate of the ice shelf. The rates vary from around 10 m a−1 at the ice front to an average value for the ice shelf of order 1 m a−1. The average value is consistent with earlier estimates from surveys of ice-shelf strain.

A device capable of measuring the extinction coefficient of solar radiation within the snow cover was developed, using small silicone photocells as sensors. Extinction coefficient measured for natural snow covers in the field was 37-97 m-1 for dry snow of density 90-470 kg m-3. It decreased in the process of metamorphism from new snow to slightly compacted snow, and increased in the process of settlement from slightly compacted to compacted snow. It was 23-58 m-1 for wet snow of density 430-530 kg m-3 and in water content from 5-15%, being smaller than that for dry snow of the same density. The authors also determined local temperature increase of snow cover related to absorption of solar radiation. The temperature profile within the snow cover was calculated by solving the equation of heat conduction including the term of absorption of radiative energy. Measured and calculated snow temperatures agreed well, indicating the accuracy of the extinction measurements.

Ice velocity, surface elevation, and ice thickness were measured along oversnow traverse routes in the sector of Wilkes Land, East Antarctica, bounded by long. 93° and 131°E, and the coast and lat. 75°S. The velocity measurements show that the ice flow varies smoothly in both direction and magnitude over a distance scale of at least 20 times the ice thickness, and that it is in the direction of the surface slope averaged over a similar distance scale. A comparison of the mean horizontal shear strain-rate with the driving stress supports a power-law relation for the bulk rheology of the ice sheet with an exponent between 3 and 3.2

In this paper we explore simulated responses of electromagnetic (EM) signals relative to in situ field surveys and quantify the effects that different values of conductivity in sea ice have on the EM fields. We compute EM responses of ice types with a three-dimensional (3-D) finite-volume discretization of Maxwell’s equations and present 2-D sliced visualizations of their associated EM fields at discrete frequencies. Several interesting observations result: First, since the simulator computes the fields everywhere, each gridcell acts as a receiver within the model volume, and captures the complete, coupled interactions between air, snow, sea ice and sea water as a function of their conductivity; second, visualizations demonstrate how 1-D approximations near deformed ice features are violated. But the most important new finding is that changes in conductivity affect EM field response by modifying the magnitude and spatial patterns (i.e. footprint size and shape) of current density and magnetic fields. These effects are demonstrated through a visual feature we define as ‘null lines’. Null line shape is affected by changes in conductivity near material boundaries as well as transmitter location. Our results encourage the use of null lines as a planning tool for better ground-truth field measurements near deformed ice types.

Forced ice-shelf vibration modeling is performed using a full 3-D finite-difference elastic model, which also takes into account sub-ice seawater flow. The sea water flow is described by the wave equation. Ice-shelf flexure therefore results from hydrostatic pressure perturbations in the sub-ice seawater layer. Numerical experiments were undertaken for idealized rectangular ice-shelf geometry. The ice-plate vibrations were modeled for harmonic incoming pressure perturbations and for a wide range of incoming wave frequencies. The spectra showed distinct resonant peaks, which demonstrate the ability of the model to simulate a resonant-like motion. The spectra obtained by the full 3-D model are compared with exact solutions for the elastic thin plate with two fixed edges and two free edges. The spectra are also compared with the spectra modeled by the thin-plate Holdsworth and Glynn model (1978).