An idealized planetary flat-bottom geostrophic ice–ocean model is constructed with boundaries at latitudes 5° and 65° N and longitudes 50° W and 10° E in order to approximate the North Atlantic. The model is driven by fixed zonally averaged wind, surface air temperatures and surface ocean salinity. A dynamic thermodynamic sea-ice model is coupled to the ocean model. Only the thermodynamic insulating effects of the sea ice are considered, and no salt fluxes due to melting and freezing are included. Four equilibrium simulations of about 5000 years each are performed: two with interactive sea ice with and without ice dynamics, and two control simulations with either a fixed or no ice cover.

In the two simulations including interactive sea ice, characteristic oscillations in the ice thickness and ocean temperature are found to occur. The oscillations are smaller when sea-ice dynamics are included. The dominant oscillation occurs at about a 5 year period, with the key feature being that the presence of sea ice tends to insulate the ocean and hence allows an oceanic warming. This warming in turn eventually causes a melt-back of the ice and a subsequent cool-down of the ocean. Oscillations at longer periods of about 20 years in the thermohaline circulation are also observed. These longer-period oscillations are particularly pronounced in the northward surface water transport.

Fluxes of heat and moisture over heterogeneous snow cover are studied using a boundary-layer model. The performance of a “tile” model, suitable for calculating gridbox-average surface fluxes in a GCM, is assessed in comparison with the boundary-layer model. The impact of using a tile representation for heterogeneous snow cover in a single-column version of the Hadley Centre GCM is discussed.

In this paper we present a new methodology for the study of drifting-snow phenomena at an Alpine site This method emphasizes the accurate determination of local wind directions and the distribution of snow denudation and accumulation zones through the observation, measurement and mapping of aeolian “snowforms” and drifts. The aim is to find out whether the local wind directions on extensive surfaces in mountain areas (of about a few km2) are independent of the main wind intensity and direction, and whether valid erosion and accumulation zones are spatially stable and can be established for dominant winds. The methodology proposed to study the spatial distribution of snow by the wind has been used in the redesign of an old ski slope at La Molina, a resort in the eastern Spanish Pyrenees. Results have been very useful for deciding the design of the slopes. Therefore, we believe that the prediction of spatial snow distribution by wind in mountain areas, without the need for expensive instruments, has a valuable part to play in the management of mountain and ski resorts and roads, and in avalanche forecasting.

Data from twice-daily radiosonde flights are used to estimate spatial and temporal variations of air temperature, atmospheric transmissivity, wind speed and humidity at Blue Glacier, western Washington. U. S.A. Results indicate that the free-air conditions (interpolated in altitude and in time from radiosondes) provide a much better estimate of conditions on the glacier than do measurements from low-altitude stations. Data from the radiosondes are used to model the hourly exchange of mass and energy at the surface of Blue Glacier. In the absence of explicit information about clouds, temperature and humidity profiles from the radiosonde are used to estimate the atmospheric transmissivity needed for the calculation of short-wave radiation. Topographical influences (altitude, shading, slope angle and orientation) and surface albedo are parameterized explicitly to model the absorbed solar flux at specific sites on the glacier, Other energy fluxes (long-wave radiation, sensible-heat and latent-heat exchange) are estimated using established physical models. Hourly estimates of ablation are integrated to obtain the seasonal ablation. Modeled ablation and stake measurements made over 30 a at two sites on Blue Glacier agree within 16%, which is within the error associated with stake measurements of ablation.

To study crystal shapes, and formation and growth mechanisms of snow crystals formed below -20 °C, a new type of diffusion chamber was constructed. Using this chamber, different kinds of “peculiar shaped” crystals previously observed in nature have been produced, together with normal types of snow crystals. Gohei twins, one of the most typical polycrystalline shapes in nature, have been produced artificially. The vapor pressure was at or near water saturation at the time of nucleation. Analysis of photomicrographs and replicas of Gohei twins that were replicated in the polar regions show that the number frequency of the tip angle has a maximum frequency at about 77° and a minor one at about 54°.

On the basis of these results, a formation mechanism for some Gohei twins is proposed in this paper.

This paper investigales the climate change in two atmosphere ice-ocean coupled climate models — the UKMO and the CSIRO— in the Antarctic region over the next century. The objectives were to sec if an enhanced level of greenhouse-gas forcing results in a surface temperature signal above background variability, and to see if this pattern of change resembles the change seen to date in Antarctica, especially the warming around the Peninsula. The models show that although reduced sea-ice compactness is responsible for regions of enhanced air-temperature anomalies, these ice-compactness anomalies are determined by different mechanisms in the respective models. The pattern of warming in both models does not match the differential rates of warming seen in the observations of temperature change over the Antarctic continent in the lait few decades. Also the level of background ocean variability in the Drake Passage and Weddell Sea region hampers the clear definition of a signal over the Antarctic Peninsula in the coupled models. Although no winter enhancement in warming over the Peninsula region IS found, an autumn anomaly is seen in one of the models. The mechanism for this feature IS documented, and an explanation of why it does not persist throughout the winter season is presented.

In this paper a fundamental model is proposed to describe the time-dependent behaviour of uniform snow glide on an infinite slope. This model is composed both of a mechanical balance equation relating a driving force and a resistant force, and of a rate equation for a real contact area at the boundary. In the model, a steady motion of glide is described as a stable equilibrium of glide motion, and a non-steady motion is considered as a transient one not in equilibrium. Finally, the model is applied to a full-depth avalanche release caused by acceleration of snow glide. By comparing the model predictions with glide-velocity field data, a proper model of acceleration prior to full-depth avalanche release is determined. As a result, we can obtain the safety standards to be applied in the event of full-depth avalanches in terms of a glide velocity.

Heat balance studies were carried out during summer ablation periods 1960-1983 by the glacial investigation team of the Chinese Academy of Sciences. The effect of energy exchange on development of mountain glaciers was determined, based on the observation of heat exchange over the glacial surface of various mountainous regions. Relationships between energy transfer and climatic parameters under different climatic regimes and landform conditions are analyzed in detail. It was found that the most important heat source for snow-ice melting is radiation, a contribution amounting to between 59.0% and 92.1% of the total. Sensible heat contributed 8 - 36%. The sensible heat flux depends on the bulk transfer coefficient and the glacier cooling effect. The mean value is about 16.3 Ly/day.K.. With the decrease of sea influence, altitude of the snow-line is elevated, aridity of glacier climate increases, evaporation increases gradually and melting decreases, providing conditions for glacial nourishment. When the glacier is covered with a debris layer, the glacier heat balance in continental regions is altered. Finally, the authors’ investigation on the glacier No 1, at the headwater of Urumqi river, shows that differences in structure of glacier heat balance are mainly the result of the influence of the topography and albedo on net radiation. Finally, diagrams of distribution of net radiation in space and time are presented.

Ice-penetrating radar sounding is a powerful geophysical tool for studying terrestrial and planetary ice with a rich glaciological heritage reaching back over half a century. Recent years have also seen rapid growth in both the radioglaciological community itself and in the scope and sophistication of its analysis of ice-penetrating radar data. This has been spurred by a combination of growing datasets and improvements in computational resources as well as advances in radar sounding instrumentation and platforms. Together, these developments are transforming the field and highlight exciting paths forward for future innovation and investigation.

Observations were made on thermal modification due to cooling when air flows from a grass-covered area onto a melting snow surface. To clarify the relation between such modification of air and snowmelt, the downwind variation of temperature, humidity and wind speed, together with net radiation and spatial variation of snowmelt were observed at a small snow patch measuring 70 m long and 30 m wide. When air temperature was between 10 and 20°C, with nearly neutral stratification over the upwind grass-covered area, air temperature at 0.1 m level decreased by 4 to 9°C over the downwind distance of 48 m above the snow patch, and so the sensible heat flux decreased in the downwind direction. As a result of such cooling, snowmelt in the central part of the snow patch was found to be about 25% smaller than near its edge. This value can be explained by the decrease of the total heat flux toward the snow surface due to the air modification.

As an inhomogeneous mixture of pure ice, brine, air and solid salts the physical properties of sea ice depend on its highly temperature-dependent microstructure. Understanding the microstructure and the way it responds to variations in temperature and salinity is crucial in developing an improved understanding of the interaction between sea ice and the environment. However, measurements monitoring the internal structure of sea ice are difficult to obtain without disturbing its natural state. We have recently developed an application of cross-borehole d.c. resistivity tomography to make in situ measurements that resolve the anisotropic resistivity structure of first-year sea ice. We present results from measurements made in 2008 off Barrow, Alaska, and in 2009 off Ross Island, Antarctica. the sea ice in these two regions forms in different environments: at Barrow, relatively quiescent conditions typically lead to a predominance of columnar ice, while more turbulent conditions and underwater ice formation in McMurdo Sound tend to produce a larger component of frazil or platelet ice. Interpretation of the resistivity measurements carried out in association with temperature and salinity data collected simultaneously allows both observation of the temporal evolution of the ice structure and, in the case of the Antarctic measurements, the identification of different ice types.

The amount of acidity in precipitation has been measured in heavy-snowfall regions facing the Sea of Japan. The average pH value of precipitation measured throughout the year at Nagaoka was 4.80 during 4.5 years, 1987–92. During winter the pH value is lower and electric conductivity higher. The spatial distribution of chemical components in new-fallen snow was studied along a 55 km-long sampling route. Results from four surveys showed that acidic snows have average pH values of 4.63–4.90. From the distribution of anion and cation concentration in new-fallen snow, it is concluded that strong northwest monsoons during winter bring an abundance of snow with salt components and many non-salt components from the Sea of Japan and also, possibly, from the Asian continent.

We have reduced the time taken for measurement of snow water equivalent using cosmic radiation by two to four hours with an accuracy of 1 cm of water equivalent. When BF3 counters were used by Kodama in 1975, it took three days. For comparison we sometimes still have to make measurements manually or automatically in flat areas. These measurements can then be compared with measurements from avalanche starting zones where conditions can be quite different because of wind or ablation.

For avalanche forecasting, or in similar situations, when an accuracy of 1 cm is needed within a few hours, we suggest the use of scintillation counters with a doped plastic material. The greatest accuracy is obtained by using a separate site where values are recorded without snow. In this case 200 000 pulses per hour are obtained (absorption length of 400 cm) which after measurements of 2 h duration gives the desired error of 1 cm of water. After 8 h the error is 0.5 cm of water, and after 24 h it is 0.3 cm of water. At an altitude of 2 000 m at which most avalanches are released, the count rate is doubled and the measuring error is 0.7 of that at sea-level. At an altitude of 3 000 m the count rate is four times that at sea-level. In other regions at other latitudes and elevations other values would be found.

The necessary equipment can be built into the ground in autumn so that the surface is level with the ground. A slot antenna of frequency around 400 MHz is used for transmission of the data.

The precision of radar altimetry above an ice sheet can improve glaciological studies such as mass balance surveys or ice-sheet flow models, the first by comparing altimetric data at different times (see this issue), the second by testing or constraining models with data. This paper is a first step towards the latter. From a precise topography deduced by inversion of altimetric data (Remy and others, 1989), we calculate ice-flow direction, balance velocity and basal shear stress. The rheological parameters involved in the relation linking velocity, stress and temperature are then derived by least-squares regression. Ice flow is well represented by setting the Glen parameter, n to 1 ± 0.25 and the activation energy as 70 ± 10 kJ mol−1.

As part of the Winter Weddell Sea Project 1986 (WWSP 86), a buoy, transmitting via TIROS-N satellites to Service Argos, was inserted into an ice floe in the southern Weddell Sea. Operational U.K. Meteorological Office numerical surface-pressure analyses, which utilized the buoy’s measured values of air pressure and temperature, are used to assess the impact of weather systems on pack-ice movement. The motion of the buoy is shown to be related closely to the position of the circumpolar trough and to the tracks of depressions crossing the area. The tracks of this and other buoys deployed during WWSP 86 are analysed, together with the known drifts of some ice-bound vessels, to establish the overall movement of sea ice in the central and western Weddell Sea. Using these data, the area of ice transported northward out of the Weddell Sea is determined. Roughly 60% of the winter sea-ice cover is discharged out of the area, and is replaced by new ice formation in coastal polynyas and by influx of new ice from the east. In summer, a further 30% is discharged northward out of the region, leaving 40% cover and by implication a 30% loss by melting.

Movement of the sea-ice edge on short time-scales (<1 d) is due to a balance of forces between several mechanisms (wind stress, sea-surface tilt, internal ice stress, and Coriolis force) which are often comparable in magnitude. Other factors such as the force induced by partial reflection of short seas, internal gravity waves in the pycnocline, etc., may also contribute. Through the momentum equation, these mechanisms affect the dynamics of the ice edge. In this paper we suggest another mechanism which may have importance, namely, a radiation-stress contribution which derives from obliquely incident waves which are totally reflected from the ice edge by a process analogous to total internal reflection in optics. Such reflection generates both normal and shear forces at the ice edge, the former tending to compact the pack ice and the latter to shear the absolute edge. The effect is studied using some recent data collected during the Winter Weddell Sea Project 1986 in Antarctica, where it is found that the contribution to the force balance is significant. For thicker sea ice and icebergs acted upon by oblique seas, the radiation stress-induced force may outweigh more conventional terms in the momentum equation.

Numerous studies have shown that climate has varied between ice-free and glaciated states, with transitions often marked by abrupt steps. We summarize some modeling studies that have attempted to explain elements of the long-term trend and discuss a particular model for abrupt transitions that involves instabilities due to albedo discontinuities at the snow/ice edge.

A compilation of mean values of the oxygen-isotope ratio relative to standard mean ocean water (δ18O, in ‰) for 22 siIes representative of conditions in northeastern Canada is complemented with data on mean annual surface temperature, latitude, surface elevation, and mean annual shortest distance to open ocean denoted by the 10% sea-ice concentration boundary. Stepwise regression analysis is used to develop a multivariate model suitable to inter the distribution of δ18O in an area of complex topography and possibly mixed sourcing of advected water vapor. The best model is produced by a run in the backward mode at the 95% confidence level in which only temperature, latitude and distance to the open ocean remain in the model (the correlation coefficient is 0.915, the adjusted coefficient of determination is 0.809, the root mean square residual is 1.62). This model is similar to the best δ18O predictive model derived elsewhere for Greenland, suggesting a common principal source of advected moisture.

Sea level rise contributions from the Pine Island Glacier (PIG) are strongly modulated by the backstress that its floating extension – Pine Island Ice Shelf (PIIS) – exerts on the adjoining grounded ice. The front of PIIS has recently retreated significantly via calving, and satellite and theoretical analyses have suggested further retreat is inevitable. As well as inducing an instantaneous increase in ice flow, retreat of the PIIS front may result in increased ocean melting, by relaxing the topographic barrier to warm ocean water that is currently provided by a prominent seabed ridge. Recently published research (Bradley and others, 2022a) has shown that PIIS may exhibit a strong melting response to calving, with melting close to the PIG grounding line always increasing with ice front retreat. Here, we summarise this research and, additionally, place the results in a glaciological context by comparing the impact of melt-induced and ice-dynamical changes in the ice shelf thinning rate. We find that while PIG is expected to experience rapid acceleration in response to further ice front retreat, the mean instantaneous thinning response is set primarily by changes in melting, rather than ice dynamics. Overall, further ice front retreat is expected to lead to enhanced ice-shelf thinning, with potentially detrimental consequences for ice shelf stability.