Two sets of bubble-density foliation, one vertical and transverse to flow and one vertical and parallel to flow, developed in the ice of the terminus lobe of Variegated Glacier, Alaska, during the passage of the final stages of the 1982–83 surge in June and July 1983. The transverse foliation is ubiquitous in the lower part of the terminus lobe affected by the surge, but disappears abruptly over a 5 m wide zone at the boundary of the surge, as delineated by measurable strain rates during the surge. The ice at the outermost limit of the transverse foliation experienced compressive total strains no greater than −0.10 (logarithmic), but did briefly experience high strain rates, corresponding to compressive stresses in excess of 0.6 MPa. It is concluded that the transverse foliation was developed as a consequence of high compressive stress rather than high total strains. Experimental evidence of Kamb indicates that bubble migration occurs under similar tectonic conditions to those in the terminus lobe during the surge, and that bubble migration is related to stress rather than finite deformation or rotation of pre-existing structures. Bubble migration may be the mechanism by which the transverse foliation developed during the passage of the surge front.

Three glaciers in southern Norway, with very different mass-balance characteristics, are studied with an energy-balance model of the ice/snow surface. The model simulates the observed mass-balance profiles in a satisfactory way, and can thus be used with some confidence in a study of climate sensitivity. Calculated changes in equilibrium-line altitude for a 1 K temperature increase are 110, 108 and 135 m for Nigardsbreen, Hellstugubreen and Alfotbreen, respectively. The corresponding changes in mass balance, averaged over the entire glacier area, are −0.88, −0.715 and −1.11 m year−1 (water equivalent).

Runs with an ice-flow model for Nigardsbreen, to which calculated mass-balance profiles arc imposed, predict that the front will advance by 3 km for a 1 K cooling, and will retreat by as much as 6.5 km for a 1 K warming. The response to a 10% increase in precipitation would be a 2 km advance of the snout, whereas a 4 km retreat is predicted for a 10% decrease. This large sensitivity (as compared to many other glaciers) is to a large extent due to the geometry of Nigardsbreen.

In this study, an attempt is made to simulate the historical length variations of Hintereisferner (Austria). Key elements in the model are: (1) reconstruction of the local climate (Vent); (2) multiple linear regression analysis between measured climate and mass-balance variations; (3) reconstruction of the mass balance with (1) and (2); (4) a one-dimensional numerical ice-flow model forced by the mass-balance history. Progress relative to the previous, similar studies can be summarized as two points: (1) the mass balance is reconstructed more carefully, and (2) sensitivity experiments show that uncertainties and assumptions in the flow model hardly affect the response of the glacier to climate fluctuations with a time-scale of the order of (or larger than) the response time of the glacier (around 100 year).

In the regression equation, mass-balance fluctuations are determined by the temperature during the ablation season and the annual precipitation. Cloudiness has no effect. The local temperature can be reconstructed as far back as 1755 with the temperature series from Basel, but the reconstruction of precipitation is unreliable prior to 1900. Mainly due to this point, a simulation starting in 1755 failed completely. However, in a run starting in 1894, the total retreat since then (2.2 km) was reproduced within 10%.

Ice-flow modeling requires a flow law relating strain rates to stresses in situ, but a flow law cannot be measured directly in ice sheets. Microscopic processes such as dislocation glide and boundary diffusion control both the flow law for ice and the development of physical properties such as grain-size and c-axis fabric. These microscopic processes can be inferred from observations of the physical properties, and the flow law can then be estimated from the microscopic processes.

A review of available literature shows that this approach can be imperfectly successful. Interior regions of large ice sheets probably have depth-varying flow-law “constants”, with the stress exponent, n, for power-law creep less than 3 in upper regions and equal to 3 only in deep ice; n probably equals 3 through most of the thickness of ice shelves and ice streams.

Two practical problems in the use of time-lapse photography for the measurement of speed were encountered during the recent surge of West Fork Glacier in the central Alaska Range, Alaska, U.S.A. The first is severe rotational camera instability; we show how natural, unsurveyed features on the valley wall can be used to make the necessary corrections. The second problem is the computation of absolute speed when many different, unsurveyed glacier-surface features are used as targets. We give a method for connecting the data obtained from different targets, and for determining the scale using limited information obtained by surveying. Severe systematic errors can occur unless the angle between the axis of the lens and the direction of horizontal motion is determined.

Annual ice ablation has been measured at three locations at the margin of the Greenland ice sheet: Nordbogletscher (for 6 years: 1977–78 to 1982– 83), Qamanârssûp sermia (8 years: 1979–80 to 1986–87) and at Paakitsup Akuliarusersua (7 years: 1982–83 to the present). As the data sets cover different periods, it is difficult to compare ablation directly between the three sites. However, measured series at each site can be extended over the last 30 years (1961–90) by simulations using climatic data, and the extended data series can be compared. The pattern of calculated ablation variations at the three locations is remarkably similar with no sign of any trend towards increased ablation in recent years. There was generally low ablation from the mid-1970s to the mid-1980s that may explain the recent thickening of the ablation area which has been detected by satellite radar altimetry. Ablation varies substantially from year to year, e.g. with a standard deviation of the order of ±0.5 m water a−1, and any future monitoring programme must detect trends of increasing ablation against this background of natural variations.

The thermal effects of air flow forced through a snow sample are investigated numerically. A new method for calculating vapor transport in snow is presented which allows for the determination of the effects of sublimation. In this method, the snow is not assumed to be saturated with water vapor. Results of the model show very good agreement with analytical and experimental results. The effects of heat conduction, heat advected by the dry air and heat associated with sublimation are examined in a comprehensive theory, and then each effect is isolated to determine its overall contribution. It is demonstrated that the heat transfer associated with vapor transport is significant in the determination of the overall temperature profile of a ventilated snow sample but that the major effects are controlled by the heat carried by the dry air flow through the snow and heat conduction due to the temperatures imposed at the boundaries. The thermal effects of ventilation of snow are more likely to be observed when there is a smaller temperature gradient over the entire snowpack and a greater flow rate of air in the snow than would be observed when there is a greater overall temperature gradient and lesser air-flow rate.

Calving has been studied for glaciers ranging from slow polar glaciers that calve on dry land, such as on Deception Island (63.0° S, 60.6° W) in Antarctica, through temperate Alaskan tide-water glaciers, to fast outlet glaciers that float in fiords and calve in deep water, such as Jakobshavns Isbræ (69.2° N, 49.9° W) in Greenland. Calving from grounded ice walls and floating ice shelves is the main ablation mechanism for the Antarctic and Greenland ice sheets, as it was along marine and lacustrine margins of former Pleistocene ice sheets, and is for tide-water and polar glaciers. Yet, the theory of ice calving is underdeveloped because of inherent dangers in obtaining field data to test and constrain calving models. An attempt is made to develop a calving theory for ice walls grounded in water of variable depth, and to relate slab calving from ice walls to tabular calving from ice shelves. A calving law is derived in which calving rates from ice walls are controled by bending creep behind the ice wall, and depend on wall height h, forward bending angle θ crevasse distance c behind the ice wall and depth d of water in front of the ice wall. Reasonable agreement with calving rates reported by Brown and others (1982) for Alaskan tide-water glaciers is obtained when c depends on wall height, wall height above water and water depth. More data are needed to determine which of these dependencies is correct. A calving ratio c/h is introduced to understand the transition from slab calving to tabular calving as water deepens and the calving glacier becomes afloat.

A finite-difference computer model was used to reconstruct a steady-state ice sheet over the western Barents Sea and the Svalbard archipelago at the last glacial maximum 18 000 BP. Flowlines were reconstructed from the ice margin to the ice dome based on information about glacial geology, bedrock topography, basal thermal regime and the present precipitation pattern. The modelling result suggests a 1700 m high marine ice dome east of Spitsbergen and a 1350 m high terrestrial dome over northwest Spitsbergen. Over most of the terrestrial areas, the bed is frozen while in the marine areas the bed is thawed. This is in agreement with both the terrestrial and the marine glacial geology records. The height of the terrestrial dome implies that the ice sheet was thin and left several of the higher mountain peaks as nunataks. Three major ice streams were reconstructed in the most pronounced over-deepened marine channels. This modelling experiment did not allow any major ice streams in the fjords of Spitsbergen during steady-state conditions.

This paper presents a simple mathematical formula for correcting radio-echo-sounding data from an ice sheet or glacier for the effects of varying refractive index. The method requires some knowledge of the variation of refractive index with depth. In rare cases this may be known from direct measurement, but it can be estimated from the density profile. If even this is unknown, we show that the corrections can be estimated to an accuracy of about 3% of the depth to bubble close-off (i.e. to about ±12 m for dry-snow conditions), and that the size of the refraction correction for a glacier or ice sheet with a flat bed is typically 6–10 m under these conditions.

Valtellina, located in the Italian Alps of Lombardy, is extensively glaciated. Since 1925, terminal variations of the glaciers have been recorded. By analysing a significant sample of valley glaciers, we have recognized a rapid retreat of the termini which occurred between 1925 and the early 1970s. A period of advance followed, which stopped in the second half of the 1980s. The mean summer-temperature fluctuations at the meteorological station of Sondrio at the centre of Valtellina, show that the period 1925–52 was very warm, and then the temperatures dropped. The most intense winter precipitation occurred in the period 1925–37. The behaviour of these glaciers is similar to that of other Alpine glaciers, although time of response may be different.