Generation mechanisms of mesoscale eddies in the ice-covered ocean are studied by using numerical ice–ocean models and discussed with reference to previous papers. The three possible mechanisms of eddy generation, with sea ice as a passive tracer, are current instability, current-eddy interaction and current–bottom topography interaction. The current instability, categorized into barotropic and baroclinic instabilities, may be responsible for eddies near the ice edge associated with a strong current. An eddy can interact with a current, producing additional eddies, where stability of the current is again an important factor for eddy formation. Eddies over bottom topography on the continental shelf are explained by current–topography interaction; i.e. anticyclones are produced over banks. The particular mechanism that includes ice as an active material is an ice–ocean interaction; i.e. a wind stress is larger over the ice than on open water and induces Ekman pumping and suction, which produce dipole eddy motions in the non-uniformly ice-covered ocean. The eddies are suggested to be important for cross-shelf exchanges of ice and heat as well as determining locations of deep convection.

A total of 400 soundings along 15 profiles were obtained on White Glacier, Axel Heiberg Island, N.W.T. with a monopulse radar equipment that was rebuilt according to a model of the US Geological Survey. The resulting data allowed maps to be compiled of the ice thickness for the glacier tongue, The radio echo-sounding data and englacial temperature measurements give some indication of the existence of stagnant ice in depressions of the glacier bed in the accumulation zone of White Glacier.

The largest ice island presently known to exist in the Arctic Ocean has a mass of about 700 × 106 tonnes, an area of about 26 km2, and a mean thickness of 42.5 m. Known as Hobson’s Ice Island, this large ice feature has been tracked almost continuously since August 1983 with a succession of Argos buoys. In this paper, two particular ice-island movement episodes near the north-west coast of Axel Heiberg Island are described: 6–16 May 1986 and 14–21 June 1986. Each movement episode is analyzed in terms of the forces acting on the ice island, including wind shear, water drag, water shear, Coriolis force, sea-surface tilt, and pack-ice force. Ice-island movement is generally preceded by an offshore surface wind, and a threshold wind speed of 6 m s°1 appears to be necessary to initiate ice-island motion. An angle of 50° between surface wind and ice-island movement direction is noted during one episode. The pack-ice force, which appears to be the dominant arresting factor of ice-island motion for these two episodes, varies from 100° to 180° to the left of the ice-island velocity direction, depending upon whether the ice island is accelerating or decelerating.

A time series of satellite passive microwave observations by the Special Sensor Microwave/Imager (SSM/I) instrument, of the Antarctic marginal ice shelves, reveals sharp transitions in the radiometric brightness temperatures at 19 and 37 GHz. These transitions, sometimes occurring over the period of a single day, indicate the onset of surface melting of the ice. Monitoring the day of the onset of melting and the permanent re-freezing will be a measure of rising air temperatures as a result of global warming. The response from a stable ice shelf, the Ronne, where no appreciable melting occurs, is compared with observations from the marginal ice shelves on Antarctic Peninsula. It is observed that the spectral gradient (Tb19 - Tb37) varies as a function of time on a clear annual cycle. It is shown that variations in the spectral gradient arise due both to the temperature profile within the snow and the dielectric effects of a wet surface layer.

We have investigated two 30 m cores at two different spots in the most heavy snow-accumulation regions on Mizuho Plateau, East Antarctica. Marked seasonal variations periodically appear in oxygen isotope records of the cores. We analyzed one core with no trace of snow melting and found it had a complete record showing a yearly change of annual net snow accumulations from 1920 through 1980. The analysis shows that a yearly variation of annual net accumulation (N.A.) has some relations with that of the annual maximum value (δmax) of δ18O and that of the annual amplitude (Δδ) of the δ18O-change in an annual snow layer. Power spectral analyses with respect to the variation of N.A., δmax and Δδ also indicate that there is commonly a predominant periodicity of about five years.

The equations of motion (continuity and momentum balance) for a dispersed, negatively buoyant particulate of snow entrained in a turbulent airflow contain apparent turbulent forces or turbulent particle buoyancies. These turbulent buoyancies arise from the constitutive assumption that the turbulent fluctuations of the snow phase velocity vector U’s, and the drift snow density ρ’s, are proportional to the deviatoric mean rate of deformation tensor for the airflow.

For an established, discretized airflow regime, the momentum balance equation for the snow phase can be solved by finite difference techniques for the snow particle velocity field. The snow phase continuity equation can then be solved for the drift snow density field.

The solutions for the snow phase equations of motion for a one dimensional airflow adjacent a solid surface show that the theory can reproduce an inertia! snow particle effect. The snow particle decelerates less rapidly than the airflow, resulting in the snow particle having a positive horizontal impact velocity at the solid surface, where air velocity goes to zero.

The solutions for the snow phase equations of motion for mixture flow and subsequent wind-aided snow accumulation on the immediate lee of a model mountain slope show that the theory can reproduce the geometries typical of wind-aided snow accumulation profiles, measured on the lee of mountain slopes.

The concentration and size distribution of water insoluble microparticles were measured in 2 332 snow and firn samples from (a) two sites on the Antarctic Peninsula, (b) the Byrd station strain network, West Antarctica, (c) the Q-13 and base camp sites on the Ross Ice Shelf, and (d) the South Pole and Dome C sites in East Antarctica. These near-surface microparticle studies indicate that, while the number of particles per unit volume of sample remains fairly uniform from site to site, the annual particle accumulation is greatest at locations nearest the coast and decreases rapidly with distance inland. The relationship between particle accumulation and distance from the coast is analogous to a relationship between snow accumulation and distance from the coast. Ten times more particles are deposited annually at stations within 50 km of the coast than at the South Pole and Dome C sites. The size distribution data reveal that, with the possible exception of the Q-13 site, the particulates deposited in Antarctica are well-sorted, indicating little contribution from local sources.

A combination of image-based velocity mapping techniques and finite-element modeling has been used to study a part of the southern shear margin of Ice Stream D, Antarctica. The study area is a region over which the margin shows considerable development morphologically, where a new southern margin is forming in response to an abrupt increase in ice-stream width just upstream of the study area. A series of ice-speed profiles perpendicular to the margin was determined by semiautomated displacement measurements of small ice features in sequential Landsat TM images. Transverse speed gradients ∂u/∂y of these profiles were determined by calculating the slope of a high-order polynomial fit to the speed profiles. Maximum ice speed and ∂u/∂y increase dramatically as the margin develops in the downstream direction, from 420 to 670 mal,and from 0.02 to 0.16 a, respectively. Finite-element modeling of the upstream and downstream profiles suggests that a considerable change occurs in the stiffness of the ice in the marginal zone between the two profiles, and in the stiHness or amount of sliding in the basal layer underlying the margin. Ice in the downstream profile appears to have marginal zones of softer ice in which shear strain is concentrated and uniformly low resistance to deformation in the bed. For the upstream profile, modeling suggests that the ice is not softened near the margin and that the bed is stiffer near the margin. Model-based calculations suggest that the bed shear is responsible for 69% of the resistance to flow in the upstream margin area;this value is 51 % in the downstream area.

Snowdrift formation has been monitored in the eastern Spanish Pyrenees since 1992 at an experimental study plot at the La Molina ski resort between 2000 and 2400 m. Several instruments were installed to characterize the wind, quantify snow-mass flux, detect snowdnfting episodes and measure the evolution of a natural snowdrift.

This plot is situated within a natural snowdrift and is equipped with measuring instruments such as snow poles, three columns of snow collectors (prismatic boxes) facing the dominant winds and an anemographic station.

During the 4 years of data acquisition, the thickness of the snowdrift has been measured and the snow collectors checked once each week. An active interest has been taken in the relationship between snowdrift development and drifting snow during a wind episode.

The relationship observed between wind, drifting snow and the development of the snowdrift is presented The results show: (1) the amount of snow collected in the snow collectors is related to wind intensity and to the availability and the quality of drifting snow, and (2) wind intensity principally affects the relative location of maximum snowdrift growth rather than controlling the thickness of the snowdrift.

By comparing the evolution of the snowdrift with Tabler’s (1975) model, we observed that it fits with the topographic features of our study area for the three seasons shown.

A digital ice-concentration database spanning 20 years (1960 to 1979) was established for the Great Lakes of North America. Data on ice concentration, i.e. the percentage of a unit surface area of the lake that is ice-covered, were abstracted from over 2 800 historic ice charts produced by United States and Canadian government agencies. The database consists of ice concentrations ranging from zero to 100% in 10% increments for individual grid cells of size 5 × 5 km constituting the surface area of each Great Lake. The data set for each of the Great Lakes was divided into half-month periods for statistical analysis. Maxinium, minimum, median, mode, and average ice-concentrations statistics were calculated for each grid cell and half-month period. A lakewide average value was then calculated for each of the half-month ice-concentration statistics for all grid cells for a given lake. Ice-cover variability and the normal extent and progression of the ice cover is discussed within the context of the lakewide averaged value of the minimum and maximum ice concentrations and the lakewide averaged value of the median ice concentrations, respectively. Differences in ice-cover variability among the five Great Lakes are related to mean lake depth and accumulated freezing degree-days. A Great Lakes ice atlas presenting a series of ice charts which depict the maximum, minimum, and median icecover concentrations for each of the Great Lakes for nine half-monthly periods, starting the last half of December and continuing through the last half of April will be published in 1983 by the National Oceanic and Atmospheric Administration (NOAA). The database will be archived at the National Snow and Ice Data Center of the National Environmental Satellite Data and Information Service (NESDIS) in Boulder, Colorado, USA, also in 1983.

Characteristic growth processes were investigated by measuring cross-sectional areas of ice crystals for four 30 m snow cores drilled in Mizuho Plateau, Antarctica. Considerable difference was found in the growth rate of crystals between a temperature-gradient layer above 6 m depth and an isothermal layer below 10 m depth: the growth rate in the temperature-gradient layer was much larger than that in the isothermal layer. In the isothermal layer, temperature dependence of the growth rate K was expressed by an equation K = K0 exp(−E/RT), where R and T are the gas constant and absolute temperature respectively. The apparent activation energy E is 44.7 kJ mol−1.

On the other hand, in the temperature-gradient layer, the apparent activation energy was as small as 12 kJ mol−1: the difference was explained as due to the temperature gradient. Using the temperature profiles in snow that have been estimated from the meteorological data from several stations, the growth rates in the temperature-gradient layer were calculated. The calculated temperature dependence of the growth rates, taking into consideration vertical flux of water vapor between ice particles caused by the temperature gradient, showed good agreement with measured results. It is concluded that the growth process in the layer above 6 m depth is mainly due to vapor transport under the vertical temperature gradient.

Calving of floating ice shelves is studied by a viscoelastic finite-element analysis. The fan-shaped breaking-up of glaciers due to forces that cause bending on creeping ice is assumed to be axisymmetric. Bending may be due to geometry of the bcdrock, action of tides and waves, and imbalance (at the ice front) between the stress in the ice and the sea-water pressure.

The bulk and shear moduli of the ice are represented by relaxation functions of the Prony series, which is a discrete relaxation spectrum composed of a constant and a summation of exponential terms. These properties are also functions of temperature, that varies over the thickness of the ice shelf. The temperature distribution across the thickness of the ice is obtained from calculations based on a linear dependence of thermal conductivity on the temperature. Numerical results are presented for various calving mechanisms. A computer code, VISIC1, is developed by modifying a finite-element viscoelastic code, VISICE, for floating ice islands. The buoyancy of the water is taken into account by a Winkler spring model, with the spring force determined from displaced volume. Locations of crack initiation obtained from the analysis are used to predict the iceberg size immediately after calving.

Recent satellite measurements of glacier mass balance show mountain glaciers all over the world had generally negative mass balances in the first decades of the 21st century. We analyse archived data for surface mass balance and summer temperature for 37 Northern Hemisphere glaciers with data for 1961–2020. We compare mean annual balances for 1961–90 and 1991–2020, and for 25 glaciers explain the changes in annual balance by changes in winter and summer balances. Mean balances 1961–90 were already substantially negative for 19 out of the 25 glaciers. Changes in winter balances from 1961–90 to 1991–2020 average close to zero but changes in summer balance are strongly negative. Mean balance 1991–2020 is strongly correlated with change in summer balance, weakly correlated with winter balance change, and strongly correlated with mean balance 1961–90. We estimate 1991–2020 summer temperature anomalies for the 37 glaciers and confirm that summer temperature anomalies for 1991–2020 were higher for the Alps, by nearly 1.5°C, than for other areas. Substantial variations in the temperature – sensitivity of summer balances for individual glaciers of −0.2 to −1.0 m w.e. a−1 °C−1 deserve further study.

Cryoconite holes are structures characteristic of the glacierised ablation areas, formed from dark sediment deposition which melt the glacier ice leading to their cylindrical structure formation. The present study focuses on an unstudied blue ice area of East Antarctica over the Hells Gate Ice Shelf in Northern Victoria Land. Taking advantage of neural network methodology applied on drone acquisitions, an automatic detection of cryoconite holes was carried out (88% of accuracy), mapping ~3500 m2 (0.4% fractional cover) of cryoconite holes over an area of 900 000 m2. The surveyed area showed heterogeneity in cryoconite hole distribution, with some regions showing an area fraction of holes (regions exhibiting frozen ponds and ice bands) as high as 8%. Thanks to this detection, the spatially integrated radiative forcing of cryoconite holes over blue ice surface was estimated to be almost 1 Wm−2. This estimation was based on the measured albedo difference between the two surfaces, which averages 0.31. However, the radiative forcing is strongly increased if calculated at a single cryoconite hole scale, showing an average of ~200 Wm−2. In conclusion, the present research represents a first attempt of analysing cryoconite holes as factors impacting the blue ice in Northern Victoria Land, deepening our understanding of their glaciological role at the margins of the East Antarctic Ice Sheet.

A relatively simple, three-parameter model is used to simulate the annual precipitation (accumulation) distribution for the Greenland ice sheet and surrounding regions. The three parameters are (1) the flux of relative vorticity at the 500 mbar level (a measure of cyclonic activity), (2) atmospheric moisture content, and (3) surface terrain. The climatological (1946–79) precipitation distribution predicted by the model displays major features of the observed distribution derived from pit studies. However, the model suggests that, due to changes in storm tracks during this period of 33 a, accumulation distribution maps based on pit studies for varying periods of record may not be representative of a true mean for a uniform period of record. The model is then applied to reconstructed ice-age conditions. Compared to present conditions, accumulation reductions of 60¾ or more are indicated for much of the southern half of Greenland; only slight reductions are noted for northern Greenland.

A fluid-dynamical model of powder-snow avalanches is developed which takes into account three-dimensional topography and can compute an avalanche’s running course. The model also predicts the variations of height, speed and concentration of snow particles in the avalanche, as well as the level of turbulence. Application of the model to the Maseguchi avalanche, which occurred in 1986 at Niigata, Japan, shows it can provide reasonable prediction of the running course, height and speed of an avalanche.

Liquid water at the ground–snow interface is thought to play a crucial role in the release of glide-snow avalanches, which can be massive and threaten infrastructure in alpine regions. Several mechanisms have been postulated to explain the formation of this interfacial water. However, these mechanisms remain poorly understood, in part because suitable measurement techniques are lacking. Here, we demonstrate the use of neutron radiography for imaging water transport in soil–snow systems. Columns of sand, gravel and snow were used to simulate the capillary forces of the soil–vegetation–snow layering found in nature. The columns were connected to a water reservoir to maintain a constant-pressure boundary condition and placed in a climatic chamber within the neutron beam. We show that neutron radiography is capable of measuring changes in the optical density distribution (related to liquid water content) within all three layers of the model system. Results suggest that a porous interface between the sand and snow may induce the formation of a water layer in the basal snowpack. Improved understanding of the water transport in soil–snow systems should lead to better prediction of glide-snow avalanche release and could also benefit other fields such as snow hydrology.

Arctic rain-on-snow (ROS) events can have significant impacts on Arctic wildlife and socio-economic systems. This study addresses the meteorology of two different Arctic ROS events. The first, occurring near Nuuk, Greenland, generated significant impacts, including slush avalanches. The second, less severe, event occurred within the community of Iqaluit, Nunavut, Canada. This research utilizes atmospheric reanalysis, automated surface observation station data and atmospheric soundings to determine the meteorological conditions driving these events and the differences between each case. In both cases, atmospheric blocking played a leading role in ROS initiation, with atmospheric rivers – narrow bands of high water vapor transport, typically originating from the tropics and subtropics – having both direct and indirect effects. Cyclone-induced low-level jets and resultant ‘warm noses’ of higher air temperatures and moisture transport were other key features in ROS generation. To our knowledge, our study is the first to visualize how the varying strength and manifestation of these coupled features contribute to differences in the severity of Arctic ROS events. The meteorological drivers identified here find support from other studies on Arctic ROS events and are similar to weather features associated with Arctic precipitation events of extreme magnitude.

An energy-balance climate model designed for coupling to ice-sheet models is presented. Its independent variables are longitude, latitude and time of the year. The model is based on the vertically integrated equations of conservation of energy and humidity. It can predict the vertically averaged temperature. Since it includes a hydrological cycle, it can also diagnose the net fresh-water flux and hence the annual snow budget at the atmosphere–ice-sheet interface. To this end, the model does not require observed precipitation rates. The computational cost is reduced by using an analytically computed Fourier–Legendre representation of daily insolation. For a highly idealized test-case configuration, two simple sensitivity experiments are carried out.