During the last glacial maximum in West Antarctica separate ice caps developed on Alexander Island and on Palmer Land, became confluent in George VI Sound, and discharged northward from latitude 72° S. Radiocarbon (>32,000 yr) and amino acid (approximately 120,000 yr) age determinations on shell fragments (Hiatella solida) found in basal till suggest a Wisconsin age for the glaciation that incorporated them. The pattern of ice flow differed from that deduced for this area in the CLIMAP reconstruction. Following the maximum stage, there was a stadial event when outlet valley glaciers flowed from smaller ice caps into George VI Sound. More widespread recession permitted the George VI ice shelf to deposit Palmer Land erratics on eastern Alexander Island before isostatic recovery raised them to final elevations of about 82 m. The ice shelf may have been absent at about 6500 yr B.P., when large barnacles (Bathylasma corolliforme) were living in the sound. Small glaciers readvanced to form at least two terminal moraines before the ice shelf re-formed and incorporated the barnacle shells into its moraine on Alexander Island. The shells gave a 14C age (corrected for Antarctic conditions) of about 6500 yr B.P. and an amino acid ratio consistent with a Holocene age. Valley glaciers readvanced over the ice-shelf moraine before oscillations of both valley glaciers and the ice shelf led to the formation of the present sequence of contiguous ice-cored moraines, probably during the Little Ice Age. Such oscillations may represent a climatic control not yet observed in the dry valleys of Victoria Land, the only other part of Antarctica studied in detail for glacier fluctuations.

South Georgia provides a terrestrial record of postglacial environmental change from a largely oceanic zone of the Earth. The record is representative of the southern westerlies and provides a link between Antarctica and the temperate zones of southern South America. Evidence from glacial geomorphology, slope stratigraphy, and analyses of environmental indicators in peat and lake cores is used to interpret this record. Wastage of the full-glacial ice cap was interrupted by a late-glacial stade of the outlet and valley glaciers before ca. 10,000 yr B.P. Plant growth had begun at low altitude (<50 m) on the sheltered (lee side) northeast coast within the late-glacial moraine limits by 9700 yr B.P. Environmental conditions on slopes above 80 m probably were too rigorous for a stable vegetation cover until ca. 6400 yr B.P. This was followed by a period from 5600 to 4800 yr B.P. when conditions were warmer than at present by up to 0.6°C. Periods of climatic cooling occurred at ca. 4800-3800 yr B.P., ca. 3400-1800 yr B.P., and within the last 1400 yr. The most extensive Holocene advance of South Georgia glaciers culminated just before 2200 yr B.P. These Holocene temperature changes of between 0.5 and 1.0°C are comparable in scale and timing to those identified from recent analyses of Vostok ice cores from the Antarctic ice sheet.

Glacial landforms and drift stratigraphy in central Magellan Strait, southernmost Chile, document repeated fluctuations during the last glacial cycle of outlet lobes from an ice cap centered over the southern Andes. The lobes developed comparatively low-gradient profiles because of low basal shear stresses over soft deformable beds and this made them sensitive to even small-scale changes in the mass balance. Such low profiles and rapid calving in deep proglacial lakes during deglaciation may have made the Magellan ice lobe particularly responsive to climatic fluctuations during the last glacial cycle, and to advance and retreat over considerable distances. Study of the glacial landforms and drift stratigraphy has led to the identification of at least five glacier advances to limits at and south of the Segunda Angostura. Fragments of mollusc shells contained in basal till indicate marine incursions between some advances, thus documenting extensive deglaciation. A partial chronology based on amino acid studies and radiocarbon dating suggests that five of these advances occurred during the last glacial cycle. The most extensive advances may have culminated during substages of marine isotope stage 5 (substage 5b or 5d) and/or during stage 4. Slightly less extensive advances occurred between ca. 28,000 and 14,000 yr B.P.

In glacial environments particle-size analysis of moraines provides insights into clast origin, transport history, depositional mechanism and processes of reworking. Traditional methods for grain-size classification are labour-intensive, physically intrusive and are limited to patch-scale (1 m2) observation. We develop emerging, high-resolution ground- and unmanned aerial vehicle-based ‘Structure-from-Motion’ (UAV-SfM) photogrammetry to recover grain-size information across a moraine surface in the Heritage Range, Antarctica. SfM data products were benchmarked against equivalent datasets acquired using terrestrial laser scanning, and were found to be accurate to within 1.7 and 50 mm for patch- and site-scale modelling, respectively. Grain-size distributions were obtained through digital grain classification, or ‘photo-sieving’, of patch-scale SfM orthoimagery. Photo-sieved distributions were accurate to <2 mm compared to control distributions derived from dry-sieving. A relationship between patch-scale median grain size and the standard deviation of local surface elevations was applied to a site-scale UAV-SfM model to facilitate upscaling and the production of a spatially continuous map of the median grain size across a 0.3 km2 area of moraine. This highly automated workflow for site-scale sedimentological characterization eliminates much of the subjectivity associated with traditional methods and forms a sound basis for subsequent glaciological process interpretation and analysis.

The thrust of this paper is that James Croll should be more generously lauded for his remarkable contribution to the study of ice ages, glacier flow and the nature of the Antarctic ice sheet. Croll was the first to calculate the link between fluctuations of the Earth’s orbit and glacial/interglacial cycles, and to identify the crucial role of positive feedback processes necessary to transform minor insolation changes into major climatic changes. He studied the mechanisms of glacier flow and explained flow over horizontal land surfaces at a continental scale, including the excavation of rock basins. Croll relied on a quantitatively based deductive approach. One of his most remarkable achievements was his study of the thickness, thermal regime and dynamics of the Antarctic ice sheet (1879). This contains important insights, which are relevant today, and yet the paper was published before anyone had landed on the continent!

We use an empirically validated high-resolution three-dimensional ice-sheet model to investigate the mass-balance regime, flow mechanisms and subglacial characteristics of a simulated Younger Dryas Stadial ice cap in Scotland, and compare the resulting model forecasts with geological evidence. Input data for the model are basal topography, a temperature forcing derived from GRIP δ18O fluctuations and a precipitation distribution interpolated from modern data. The model employs a positive-degree-day scheme to calculate net mass balance within a domain of 112500 km2, which, under the imposed climate, gives rise to an elongate ice cap along the axis of the western Scottish Highlands. At its maximum, the ice cap is dynamically and thermally zoned, reflecting topographic and climatic controls, respectively. In order to link these palaeoglaciological conditions to geological interpretations, we calculate the relative balance between sliding and creep within the simulated ice cap, forecast areas of the ice cap with the greatest capacity for basal erosion and predict the likely pattern of subglacial drainage. We conclude that ice flow in central areas of the ice cap is largely due to internal deformation, and is associated with geological evidence of landscape preservation. Conversely, the distribution of streamlined landforms is linked to faster-flowing ice whose velocity is predominantly the result of basal sliding. The geometry of the main ice mass focuses subglacial erosion in the mid-sections of topographic troughs, and produces glaciohydraulic gradients that favour subglacial drainage through low-order arterial routes.

Understanding the response of present and former ice caps to climatic fluctuations depends on an effective means of modelling mass balance. Ablation can be reasonably well approximated from surface energy-balance calculations, but changes in snowfall, the primary mass-gain mechanism, are poorly understood. This is a particularly important limitation in those mid-latitude areas where the location of precipitation belts changes from glacial to interglacial conditions. This paper develops a method of modelling the spatial and temporal variability of snowfall in Patagonia. Snowfall is predicted from a vertically integrated moisture-balance equation representing winter, equinoctial and summer seasons. Inputs to the model are sea-surface temperatures and the geostrophic wind at 700 mbar. The dominant process affecting precipitation is the advection of moisture in an air column whose ability to hold moisture is dependent on temperature and altitude. Relative humidity controls evaporation and precipitation, both of which increase with higher wind speeds. Snowfall is calculated from seasonal precipitation and the annual temperature regime, while ablation is estimated from degree-day calculations. The model successfully simulates present-day precipitation and mass-balance patterns in Patagonia. We also run the model for full-glacial conditions with and without an ice cap, revealing the extreme variability of mass balance at different stages of a glacial cycle and the relative importance of altitude/mass-balance feed-back in ice-cap growth. Since the model is driven by wind and temperature fields it has the potential to use the results of GCMs as input.

Spatial variations in the debris-bearing basal ice layer exposed at the ice-sheet margin in West Greenland reflect the geography of basal melting and ice flow around large obstacles close to the margin. This paper demonstrates the character of the basal ice layer, which comprises fine material incorporated in an interior, subglacial environment and coarser material entrained in an ice-marginal environment. We develop an empirical model of ice flow close to a lobate margin of the ice sheet in which ice convergence and divergence, and limited subglacial melting affect the character and distribution of the basal ice at the margin. There is a tendency for the convergence and divergence to thicken the basal layer in lobate areas and to thin it in inter-lobate areas. Under certain circumstances, basal melting may remove much of the layer from beneath the snouts of larger lobes, thus causing the basal layer to be thickest in an intermediate location.

This paper combines a study of the rock debris and δD/δ18O isotopic characteristics of basal ice sequences in three representative glaciers in South Georgia and concludes that the debris and ice has been entrained mainly by basal freezing. The size distribution of the rock debris is typical of crushing and abrasion, and reflects transport at the ice–rock interface. The δD/δ18O relationships show that clear ice associated with the debris has accreted through freezing. The white bubbly glacier ice has δD/δ18O relationships typical of precipitation which demonstrates an altitudinal effect between glaciers.

On 19 and 20 August 1984, an ice-marginal lake drained through a subglacial tunnel beneath the ede of the Greenland ice sheet, discharging about 22.3 × 106 m3 of water in less than 19 h. The event, which may occur annually, modified ice-margin dynamics at the lake site and along a 3 km stretch of ice margin 11 km down-stream.