The characteristics of ice in the Okhotsk coastal polynyas are examined. A map of AMSR-E thin-ice thickness in the northwest shelf region shows that most of the coastal polynya area is covered by thin ice with a thickness of 0.1 m. the thickness increases sharply at the edge of the polynya. From comparisons with QuikSCAT backscatter, the thin-ice area corresponds well with the low-backscatter area during almost all the coastal polynya period. A comparison with ice thickness measured by an ice-profiling sonar in the coastal polynya region of northeastern Sakhalin shows a similar relationship, with the backscatter tending to be low when the ice is thin. the averaged backscatter of thin (≤0.1 m) ice is –19.6±2.8 dB (horizontal polarization). the backscatter of thin ice is considered to be mainly determined by the surface roughness because volume scattering of thin ice is low due to the dielectric properties associated with the high salinity. the results of this study suggest that the coastal polynya is covered with grease ice/nilas whose surface is almost mirror smooth. This is confirmed by a comparison with photographs taken at the coastal polynya region near Magadan, Russia. At the outer edge of the coastal polynya, a region of relatively high backscatter (>–16 dB) exists, probably because it has a rougher ice surface than the polynya area. This suggests that ice motion in this area may be convergent.

A statistical method to determine surface velocities from theodolite measurements is described. The method assumes that the measuring points move according to a model and the model parameters are estimated directly from the directional observations. Observations from two fixed points need not be simultaneous, which is an advantage in the case of fast moving glaciers. The method is practised on data from the Daugaard-Jensen glacier, in East Greenland, where the motion of the measuring points is calculated to the accuracy of the directional observations.

Supercooled droplets of 38 μm mean volume diameter are accreted on a smooth aluni mum cylinder of 3.15 cm in diameter in order to study the effect of an electrostatic field upon ice formation on a power-line conductor. The results obtained show that ice grown in the presence of an applied negative field of 15 kV cm−1 exhibits a cusped-lobe structure characterized by surfacial outward knobs, convex rings of fine air bubbles and radial lines of large air bubbles; in the same conditions, a positive electric field of 15 kV cm−1 does not produce such lobe features. On the other hand, accretion tests performed in the absence of an electric field with a 33 μm droplet spectrum show that the well-developed cusped-lobe structure appears in ice at low ambient temperature and air velocity. In the present experimental conditions, the formation of cusped lobes observed in the presence of a negative electric field could be explained by a decrease in the temperature of the deposit due to a reduction of impact velocity of the charged droplets and/or an increase in the local heat-transfer coefficient at the surface of the ice accretion. Corona wind from ice points, always in the opposite direction to the impinging droplets, may also reduce their impact velocities. In addition, corona wind and roughness of the surface may contribute to a better evacuation of the latent heat and thus decrease the deposit temperature. The difference between the effects of a negative DC field and those of a DC positive field of the same strength comes from a stronger ionization intensity and/or a stronger deformation of water drops in the negative electric field.

An implicit, analytical model for momentum, heat and salt flux within a sea-ice/upper-ocean system is developed. The model comprises three parts: (a) an equation for turbulent stress in the oceanic boundary layer and upper pycnocline, from which turbulent scalar fluxes are derived; (b) a model for heat and mass transfer in a thin sub-layer near the ice/ocean interface; and (c) a model for momentum flux lost to the internal wave-field if the ice under-surface has large-scale (pressure-ridge keel) relief. Features of the model are demonstrated by simulating response of the ice drift and upper-ocean temperature and salinity structure to constant heating and variable surface stress.

The surface movement of part of a Nanga Parbat (Himalaya) glacier immediately below an ice fall has been investigated by terrestrial stereophotogrammetry. This method provides an opportunity of measuring many more points than by using other procedures. The shape of the transverse velocity profile indicated normal stream-like flow and not “blockschollen movement”, as might have been expected, because of its high velocity (45 cm/d). But, one feature of the ice fall above had been carried down-glacier to the location of the profile; namely, several discontinuities along the velocity diagram. The ice fall had transmitted a small part of its splitting into seracs to the flatter area below, but not its blockschollen movement.

There seems to be a contradiction in that on one side there are discontinuities, i.e. the glacier is torn up into blocks by shear planes, but on the other side the glacier moves en bloc. In fact, a short-term investigation over hours or just a few days discloses cracks but, after time periods of a week or more, these irregularities compensate for one another so that they merge into a single unit block motion.

A prognostic ice-ocean model of the Arctic, Greenland and Norwegian seas with daily wind and atmospheric forcing is integrated for 30 years to quasi-equilibrium. Three simulations are carried out to investigate the role played by ice deformation and transport in baroclinic adjustment of the Arctic Ocean: a standard run with precipitation and ice transport, a simulation without precipitation and a “thermodynamics only” simulation without ice transport but including precipitation. A diagnostic model is integrated for five years to serve as a comparative control run. Comparison of the vertically integrated stream-function of each of the model runs indicates that the vertical density stratification needed to maintain the circulation of the Arctic Ocean is reduced excessively when precipitation is neglected and artificially enhanced if ice transport out of the basin is ignored. This effect is even more noticeable in the surface currents and is also apparent in a comparison of simulated and observed drifting-buoy tracks. An analysis of the salt budget of the Arctic Ocean indicates that the three main components, salt transport by the ocean, salt flux from the annual cycle of ice, and a fresh-water flux from precipitation and river runoff are approximately of the same magnitude. The main circulation deficiency identified in the simulations is an inadequate flow of Atlantic water into the Arctic Basin through the Fram Strait.

In the framework of the Paleoclimate Modelling Intercomparison Project (PMIP), simulations of the Last Glacial Maximum (LGM) have- been performed. More than 10 different atmospheric general circulation models (AGCMs) have been used with the same boundary conditions: sea-surface temperatures prescribed by CLIMAP (1981), ice-sheet reconstruction provided by Peltier (1994), change in insolation, and reduced CO2 content. One of the major questions is to investigate whether the simulations of the LGM are in equilibrium with the prescribed ice-sheet reconstruction. To answer this question, we have used two different approaches. First, we analyze the results of a sel of LGM simulations performed with different versions of the Laboratoire de Meteorolo-gie Dynamique (LMD) AGCM and study the hydrologic and snow- budgets over the Laurcntide and Fennoscandian ice sheets. Second, we use the AGCM outputs to force an ice-sheet model in order to investigate its ability to maintain the ice sheets as reconstructed by CLIMAP (1981) or Peltier (1994).

The Comninou–Dundurs effect (C-D effect) has yet to be considered in slip processes at the base of ice sheets and glaciers. This effect exists whenever slip occurs between two solids of differing mechanical properties and at least one of the solids is compressible. It gives rise to an additional normal traction stress across a non-uniformly slipping interface, a stress which otherwise would not exist if the two solids had identical properties. the C-D effect should exist to some degree, therefore, wherever ice slips over glacial till. It will be enhanced where large slip gradients exist, such as at boundaries of subglacial lakes. In this paper it is shown that, because of the C-D effect, subglacial lakes that lie at a basal till/ice interface may migrate in the direction of increasing ice thickness.

Glacier meltwaters are an important component of surface water resources in western China. Based on glacier inventories, the total glacier area in China is 5.87 x 104km2, the second largest for an Asian country. The total storage of water in glaciers is about 5132 x 103 km3, and the mean annual amount of glacier melt runoff is about 5.64 x 1010m3, o r 2% of the total surface water resources of China. From the late 1950s to the present, measurements have been undertaken of about twenty mountain glaciers, and data on hydrology and meteorology obtained. The relationship between heat balance and glacier ablation has been investigated but for glacierized areas where there are no data, ice-melt runoff can be estimated from climatic data. Runoff of glacier meltwater decreases with increasing aridity of the climate. The impact of glacier meltwater on the regimes of mountain streams in different environments are described in this paper.

Most climate models treat surface and atmospheric properties as being horizontally homogeneous and compute surface radiative fluxes with average gridcell properties. In this study it is found that large biases can occur if sub-gridcell variability is ignored, where bias is defined as the difference between the average of fluxes computed at high resolution within a model cell and the flux computed with the average surface and cloud properties within the cell. Data from the Advanced Very High Resolution Radiometer for the year-long Surface Heat Budget of the Arctic Ocean (SHEBA) experiment are used to determine biases in aggregate-area fluxes. A simple regression approach to correct for biases that result from horizontal variability was found to reduce the average radiative flux bias to near zero. The correction can be easily implemented in numerical models.

A 2.7 m snow pit was sampled in the Lambert Glacier basin, about 650 km from the coast. Concentrations of methanesulfonic acid (MSA) and non-sea-salt SO42- (nssSO42-) show distinct variation with depth in the snow pit. The seasonal variation of MSA is used to date the snow-pit samples. MSA concentration is in the range 1.922.0 μgkg−1 with a mean of 7.0 μgkg-1. The mean nssSO42- concentration is 41.5 μgkg−1 with a range of 0-87 μgkg−1. The nssSO42- ∼ concentration was calculated by subtracting the sea-salt sulfate contribution using Nai as a conservative tracer. The nssSO42– contributes about 80% of the total sulfate in the snow pit. The mean mass ratio of MSA to nssSO42- 0.176, is much higher than that measured in the low to mid-latitudes, but is very close to the ratio in snow at the South Pole. El Chichon and Hudson volcanic eruptions do not significantly perturb the nssS042- concentrations at this site. MSA concentrations are anticorrelated with sea-ice area for the South Indian Ocean sector between 40° and 90° E, suggesting enhanced MSA production accompanying low sea-ice coverage.

The purpose of this study is to use the snowpack of the Saskatchewan portion of the Precambrian Shield as a passive collector of atmospheric total deposition. Although the focus is on the anions of sulphate and nitrate, the hydrogen ion and various metals are also considered.

Twenty-six small lakes on the Precambrian Shield area of northern Saskatchewan were used as sites. The lakes were all approximately 1 square km in area and serviced by aircraft. The study was conducted in late March 1982 and 1983 just before the major snowmelt period.

Concentrations of sulphate ranged from 0.26 to 7.3 mg 1−1. The concentrations were typical of large areas in northern Saskatchewan with sharp transitions in composition occurring as the treeline boundary was encountered. Typical sulphate deposition was approximately 30 mg m−2 in the Precambrian areas and 150 mg m−2 in the other areas. The distribution of conductivity in the snow cores ranged from 6 to 13 μS cm−1. Most of the snow on the Precambrian Shield areas can be described as acidic, with pH values of the meltwater being below 5.6.

Metals such as Ca, Mn, Mg, Zn and As were measured across the region. The metals Ca and Mg show a direct correlation with high sulphate levels south of the treeline. Metals such as Zn and As show anthropogenic influence particularly within 100 km of industrial sources. Large areas of the study region show uniform and low deposition to the snowpack. It is suggested that natural atmospheric processes are dominating deposition in this area of Canada.

The Special Sensor Microwave/Imager (SMM/I) instrument provides daily measures of microwave brightness temperatures Tb over the polar regions. Data are available from 1987 to the present and have a demonstrated utility for sea-ice studies. In this paper we investigate applications to polar ice sheets with a view towards correlating patterns of Tb with ice-sheet elevation. We go on to discuss the Tb signature of processes linked to temperature anomalies and accumulation zone boundaries.

Our approach consists of combining SSM/I Tb values provided on CD-ROM by the National Snow and Ice Data Center (NSIDC) with a digital elevation model (DEM) of Antarctica derived originally from the Scott Polar Research Institute Antarctic Map Folio. We focused on 37 GHz data which is mapped onto a 316 × 332 polar stereographic grid at 25 km resolution. The DEM consists of a 281 × 281 array of elevation values with a 20 km resolution. The DEM was resampled to be compatible with the SSM/I data by transforming the elevation data from the original projection place to geodetic coordinates. The elevation data were than transformed onto the SSM/I projection plane. Elevation data were interpolated to yield ice-sheet surface heights at 25 km intervals coinciding with SSM/I point Tb assignments.

By co-registering the two data sets, it is possible to “drape” the brightness temperature data over the elevation data. The resulting image highlights the relationship (and variations) between ice-sheet topography and brightness temperature.

Under the Office of Naval Research-sponsored Arctic Leads Accelerated Research Initiative (ARI), a data set of Advanced Very High Resolution Radiometer (AVHRR) imagery covering the years 1988 through 1992 is being constructed. Relatively cloud-free imagery is selected from image hardcopies. Each image examined is subjectively ranked on the percentage of each sea or seas it covers, and the cloudiness of the image within each sea. The images are then logged in a spreadsheet. From the spreadsheet, about 20 images per month (for the year 1989) are ordered from the National Oceanic and Atmospheric Administration for processing. The image data are calibrated and mapped to one of two grids, which together cover most of the Arctic at 1 km per pixel. Care has been taken to match the grid and the projection to that of Special Sensor Microwave Imager (SSM/I) data distributed by the National Snow and Ice Data Center (NSIDC). The 1989 data set is complete at this time. Presently, data are distributed to the Remote Sensing Working Group of the ARI. NSIDC will distribute the data set to a wider audience at a later date.

Four ice cores from the Ross Sea drainage, Antarctica, show patterns of δ18O variations on a time scale of decades to centuries over the last 1400 years without change in the long-term average δ18O. Century scale δ18O fluctuations in the two cores drilled in the Ross Ice Shelf at Station J-9 (82°23′S, 168°38′W, elevation 60 m) are highly correlated (P < 2 × 10−4). The long isotope record (>30 000 a) of the 1978 J-9 core thus represents local conditions over at least 102 m and on time scales of 100 years and longer.

Regional correlations between the J-9 δ18O records and those from Ridge BC (82°54′S, 136°40′W, elevation 509 m) and the Dominion Range (85°15′S, 166°10′E, elevation 2700 m) are barely significant (P ≈ 0.05 for J-9 '76 and Dominion Range, 580 to 1400 years ago) or absent. The failure to find clear regional isotope trends related to climate fluctuations may reflect the finding that between 1957 and 1982 the area was in the transition zone between areas with opposite temperature trends, and showed little or no temperature change. The fact that the records nevertheless show significant δ18O fluctuations highlights the need to base regional climate reconstructions on a regional suite of ice-core records.

An investigation was undertaken of the creep of columnar-grained ice under constant compressive stresses of 98 and 59 kPa in order to extend the observed relationship between strain-rate and stress further into the low-stress region. Stress was applied perpendicular to the long direction of the grains. Observations were made for temperatures between -5 and -40°C. The steady-state creep rate for secondary creep was not yet attained for strain of 1.4% and stress of 98 kPa. An initial yield was observed at that stress in the strain range of 0.2 to 0.3%, similar to that seen at higher stress. The observations showed that the strain-rate tended to a linear dependence on stress below 49 kPa and that more than one dislocation process with different values for the stress exponent may contribute to the strain at higher stresses. An activation energy of 63 kJ mol−1 was consistent with the observed temperature dependence of the strain-rate. Straining ice to a given strain under a stress of about 0.3 MPa and then reducing the load may be a convenient way to study the stress, strain and temperature dependence of the strain-rate at low stress.

Following international recommendations (UNESCO / IASH 1969), the decision was made to determine the surface profile of a number of glaciers in Palmer Land and Alexander Island. By comparison with the ice sheet elsewhere on the continent, the chosen glaciers were small and hence more sensitive to the effect of climate over the last few decades. Six profiles were established between 1972 and 1976 and they were re-levelled in the 1985-86 summer. The profiles are between 0.5 and 4.5 km long and are terminated, at one end at least, by a bench mark established on rock. The profiles were re-measured close to the calendar date of the original survey so that recent trends would not be masked by the annual cycle of accumulation, densification and ablation. Five of the six profiles show that the ice sheet has thickened in the last 10-15 years, albeit at a slow rate. Changes in four profiles on Alexander Island within 300 m of sea-level range from a thickening of 66 mm a−1 to a thinning of 83 mm a−1; on average the sites show a thickening of just 6 mm a year. This is similar to the thickening rate of 5 mm a−1 which was found for a cold site on the spine of the Antarctic Peninsula at 1600 m above sea-level. The greatest change was found at an intermediate elevation (500 m). In a snow-field between two parallel mountain groups in the Batterbee Mountains of Palmer Land, thickening averaged 165 mm a−1. To put these values into perspective, in the absence of glacier flow and summer melting, the glaciers would thicken by up to about 500 mm each year as a result of the accumulation of snow.

Except in the Batterbee Mountains, we find that glacier flow is in close balance with present climate, despite the general warming trend that has occurred in the Antarctic Peninsula region over the past 30 years.