The age–depth relationship of the Vostok (Antarctica) ice core has been reconstructed in the depth interval 3300–3347 m, by comparing three gas properties in ice (CO2, CH4 and δ18Oatm) with those in the EPICA Dome C (Antarctica) core. Fourteen Vostok depths were examined in this interval, and it was found that nine samples are uniquely dated if candidate ages are restricted to the interval between 400 and 650 kyr. One of these samples is uniquely dated without restriction. The analysis supports previous reports that this section contains ice from Termination V, but that the stratigraphic order of ice is reversed. The top of the overturned layer lies between 3316 and 3319 m. At least one other stratigraphic disturbance was found between 3340 and 3343 m, as indicated by another reversal of the age–depth relationship. Finally, the oldest ice in this section is dated at ≥440 kyr, confirming the existence of ice from the cold marine isotope stage (MIS) 12 interval.

We have analyzed the flow of polythermal McCall Glacier in Arctic Alaska. Using measurements of surface velocity from the 1970s and 1990s, together with measurements of ice thickness and surface slope, we have investigated both the present flow and seasonal and long-term flow variations. Our analysis of the present flow reveals that (i) longitudinal stress coupling is important along the entire length of the glacier, and (ii) there is significant basal sliding beneath a 2 km long section of the lower glacier. This sliding exists year-round and it accounts for more than 70% of the total motion there. We have developed a numerical model which shows that such a sliding anomaly causes an asymmetric decrease in ice thickness. Accompanying this decrease in thickness is a decrease in surface slope at the center of the anomaly and an increase in slope up-glacier from it. Both effects are reflected in the observed surface profile of McCall Glacier.The longitudinal stress-coupling length of McCall Glacier is three times the ice thickness, almost twice that typical of temperate glaciers. This is a direct effect of lower strain rates, which themselves are associated with the smaller mass-balance gradients of Arctic and continental glaciers. Long-term variations in surface velocity between the 1970s and 1990s are explained solely by the effects of changes in glacier geometry on the deformational flow contribution. This means that long-term variations in the spatial patterns of longitudinal stresses and basal sliding must have been small. Seasonally, Velocities reach their annual minimum in spring and increase during the short summer nick season by up to 75% above mean winter values. However, the extra motion associated with the period of elevated velocities is only about 5% of the total annual motion. The speed-up is due to an increase in basal sliding. This implies that most of the glacier bed is at the melting point. The zone a affected by the melt-season speed-up extends well up-glacier of any moulins or other obvious sources for melt water at the bed.

The three-dimensional ice-sheet model SICOPOLIS is used to simulate the dynamic/thermody namic behaviour of the entire Greenland ice sheet from 250 000 a BP until today. External forcing consists of a surface-temperature history constructed from δ18O data of the GRIP core, a snowfall history coupled linearly to that of the surface temperature, a piecewise linear sea-level scenario and a constant geothermal heat flux. The simulated Greenland ice sheet is investigated in the vicinity of Summit, the position where the maximum elevation is taken, and where the two drill sites GRIP and GISP2 are situated 28km apart from each other. In this region, the agreement between modelled and observed topography and ice temperature turns out to be very good. Computed age-depth profiles for GRIP and GISP2 are presented, which can he used to complete the dating of these cores in the deeper regions where annual-layer counting is not possible. However, artificial diffusion influences the computed ages in a near-basal boundary layer of approximately 15% of the ice thickness, so that the age at the bottom of the cores cannot be predicted yet.

During the summer of 1957 a party visited the Salmon Glacier in British Columbia. A meteorological station was established in the accumulation area at an altitude of 1700 m. From 12 June to 16 August pressure, temperature and humidity were recorded continuously and the daily totals of precipitation, ablation and percolation were obtained. Periodic measurements of snow density were made; on the first occasion to a depth of 4.7 m. and later near the surface only. Occasional observations of snow temperatures to a depth of 12 m. were also made. Towards the end of the season the heat balance of the snow surface was examined in detail. The various contributions to the melting are evaluated for several short periods and their relative magnitudes compared.

Radio echo-sounding studies were used to detect water-filled cavities on Variegated Glacier, Alaska, during its surge in 1983. Cavity locations were determined by spatial surveys, and changes in cavity size and water content over a 5 week period were inferred from phase and amplitude changes in the echo wave form. Data were taken at both 4 and 8 MHz central frequencies of the impulse transmitter. These bi-frequency results, together with spectral analysis of the digitized wave forms, were used to provide additional information about the cavity dimensions. Cavity response is interpreted in terms of a simplified model of a thin layer of strong dielectric contrast. Computer simulations of radar pulses encountering such layers reproduce the main features of the data.

Snow fences built up-wind of natural snowdrifts at four alpine sites in the Colorado Rocky Mountains changed snow accumulation appreciably. The 3 m tall fences increased the amount of snow at three sites but decreased it at the fourth. At two of the three sites where snow was increased, there was no change in melt rate, so the additional snow prolonged the melt period 1–3 weeks. Fences most successfully augmented natural snow accumulation at sites with level or gently sloping terrain down-wind from the accumulation site. Between 15 and 30 m of fence was needed to produce an extra 1000 m3 of water equivalent in the snowfields at the beginning of the melt season. Fences of the type described here, if properly located, are a means of increasing summer stream flow from alpine areas.

c-axis fabrics of the GISP2 ice core from central Greenland have been measured rapidly and accurately in the field, using both compressional and shear waves generated by an inexpensive, commercially available, “idiot-proof” device. Compressional-wave data were collected at 10 m intervals for the upper 2250 m of the ice sheet and show progressive clustering of c axes toward the vertical with increasing depth but no large steps at climatic boundaries in the core. The degree of clustering measured by ultrasound agrees closely with that measured using traditional optical techniques but the ultrasound technique is easier and faster than optical methods. A slight asymmetry in the c-axis clustering is revealed by the shear-wave data and increases with increasing depth, indicating that deformation is not symmetric about the vertical at the site.

Future mass loss projections of the Greenland ice sheet require understanding of the processes at a glacier terminus, especially of iceberg calving. We present detailed and high-rate terrestrial radar interferometer observations of Eqip Sermia and Bowdoin Glacier, two outlet glaciers in Greenland with comparable dimensions and investigate iceberg calving, surface elevation, velocity, strain rates and their links to air temperature, tides and topography. The results reveal that the two glaciers exhibit very different flow and calving behaviour on different timescales. Ice flow driven by a steep surface slope with several topographic steps leads to high velocities, areas of extension and intense crevassing, which triggers frequent but small calving events independent of local velocity gradients. In contrast, ice flow under smooth surface slopes leaves the ice relatively intact, such that sporadic large-scale calving events dominate, which initiate in areas with high shearing. Flow acceleration caused by enhanced meltwater input and tidal velocity variations were observed for terminus sections close to floatation. Firmly grounded terminus sections showed no tidal signal and a weak short-term reaction to air temperature. These results demonstrate reaction timescales to external forcings from hours to months, which are, however, strongly dependent on local terminus geometry.

Work on the Fröya Gletscher, N.E. Greenland, appears to substantiate the evidence already brought forward for the irregular flow of glaciers over short periods. It appears possible to correlate the daily temperature regime with the flow of some “polar glaciers.” The distribution of thrust planes seems to have no noticeable effect on the flow. It is suggested that Block-Schollen movement may underlie the jerky motion of some of even the slower moving glaciers. A subglacial stream bed on the Skille Gletscher was explored from the snout for a distance of 500 m. It is estimated that at the farthest point the ice was 76 m. thick. There appears to be good observational evidence for de Martonne’s theory of medial moraines extending to the bed of the glacier.

Deep, partly snow-filled gullies cutting the sea cliffs of part of the Vestspitsbergen strandflat are noted. They do not appear to have been cut by streams, and it is suggested that a process of frost action and snowpatch erosion has been largely responsible for their formation.

A short note on glacial recession in part of Vestspitsbergen is added.

The flow of a glacier along a channel of constant longitudinal curvature is analyzed using analytical and finite-element methods. Channels of various cross–sectional shape are investigated, ranging from a simple rectangular form with zero shear traction along the bed to realistic profiles taken from Blue Glacier, Washington. Terms in the equilibrium and rate-of-deformation equations which are inversely dependent on radius and a body force which varies transversely across the glacier introduce several characteristic features into the stress and velocity fields of the curving glacier. The stress center line is shifted toward the inside of the bend, causing an asymmetric crevasse pattern and non‒zero stress magnitude at the surface on the geometric center line of the channel. The stress field is dependent on the stress exponent in the flow law and is non-linear across the surface. The surface–velocity pattern shows a “tilting” of the usual high‒order parabolic form, being skewed toward the inside of the bend. There is a shift in the velocity maximum from the deepest part of the channel. All of these curvature‒induced features are dependent on the radius of curvature, actual channel geometry, and stress exponent in the flow law. Model results show excellent agreement with the velocity and crevasse patterns on the curving Blue Glacier.

These notes are based on observations made in 1958 while the writers were members of the Birmingham and Exeter Universities Spitsbergen Expedition. The position of the ice front in 1958 is compared with that recorded on five previous occasions between 1882 and 1936. A rapid 6 km. advance at the end of the nineteenth century has been followed by a slower but equally extensive retreat. A revision of the limit of maximum advance is based on geomorphological evidence. Reasons are suggested for the relatively small changes in the outline of the ice front since 1927, and the effects of spells of moderately high atmospheric pressure are noted.

The Columbia Icefield rests upon limestones containing natural caves that drain waters from the glacier sole. The principal cave is sealed at one end by an extrusion of glacier ice 300 m below the icefield surface. The hydrologic regime of the cave indicates that the modern icefield is temperate in character and that water is present at the glacier sole throughout the year. An interpretation of the air temperature pattern in the cave suggests that the geothermal flux to the glacier is only 10-40% of the expected value because heat is abstracted by melt water circulating through the rock. U, Th and O isotopic analyses of calcite speleothems further indicate that the base of the icefield has probably been temperate throughout the past 150000 years. The cave was inundated when glaciers expanded during the classical Wisconsinan main Würm period. The inundation implies maintenance of a permanent water table at some hundreds of meters above the base in a valley glacier 750—800 m in depth.

An interpretation is proposed of the phenomenon of splitting of ice dendrites growing from supercooled water and of their orientation at an angle α to the basal plane. Both phenomena are related to the instabilities which develop on the dendritic cap when the ratio Vc/Va of the growth velocities in the direction of the c- and a-axes exceeds a certain limit. The different interface supercoolings, (δTi)a and (δTi)c at the tip and at the sides of the dendrite cap are considered. Although Vc/Va increases with the bath supercooling ΔT it is found that Vc ≪ Va for (δTi)c = (δTi)a through the whole range investigated (o < ΔT ≤ 18 deg). The increase of α with the concentration of solutes is also qualitatively explained. Considering the kinetic theory of the molecular growth mechanism, the results obtained for Vc as a function of (δTi)c would indicate that most of the studied interval must correspond to the transitional regime of growth.

Two 0.5 m cores from "Byrd" station, Antarctica have been studied in the laboratory, one from a shallow depth (155 m) and the other from the zone where recrystallization has given a vertical c-axis fabric, and the air in situ is thought to be in clathrate form (1 424 m). The dielectric response has been studied in the frequency range 60 Hz to 10 kHz, and in the temperature range — 6° C to —6o° C. The behaviour observed is markedly different from that of "pure" polycrystalline ice such as may be made by slowly freezing distilled de-ionized water and is thus at variance with the conclusions of Rogers (unpublished) who deduced, from measurements of the admittance of a dipole probe lowered through the fluid-filled drill hole at "Byrd", that the ice surrounding the hole had a dielectric response similar to that of "pure" ice. The Antarctic ice is shown to have properties similar to those of the ice from "Camp Century" and "Site 2" in Greenland studied by Paren (1973). In an attempt to discover what factors determine the difference in electrical behaviour between polar ice and pure ice, some samples were melted and subsequently refrozen slowly. Their dielectric response was similar to that of pure polycrystalline ice. These results are discussed in connection with the impurity content and growth conditions of the ices.

Satellite images recorded in 1973, 1974, and 1985 of the Brunt Ice Shelf are compared. There are sufficient identifiable features moving with the ice shelf to show flow patterns over an area of ~10 000 km2. Velocities vary from 500 m a−1 in the west, near the Dawson-Lambton Ice Stream, to 1300 m a−1 in the east, within the Stancomb-Wills Ice Stream.