Using vertical aerial photographs taken manually with a 6 × 6 cm format camera in 1984, 1986 and 1999, the surface morphology of the ablation area of Glaciar Soler, Hielo Patagónico Norte (northern Patagonia icefield), Chile, was studied. Glaciar Soler has an area of 50.9 km2; the ablation area below the icefall is about 7 km long and 2 km wide. An uncontrolled aerial-photographic mosaic for the area below the icefall was assembled from 40–60 aerial photographs, on which the surface morphology was mapped from interpretation of stereo pairs of the enlarged photographs (scales of 1:4500 to 1: 8000). Themapped features include debris-free and debris-covered ices, ogive bands and waves, crevasses, supraglacial streams, moulins, medial moraines, troughs and grooves. A total of 32–34 pairs of ogive bands were recognized, from which an average flow velocity of about 160 m a–1 was deduced. The spacing of a pair of light and dark ogive bands indicates that the flow velocity ranges from about 350 ma–1 near the icefall to some 100 ma–1 near the snout. Comparison of the field-measured data with the ogive spacing indicates that the seasonal variation in flow velocity of Glaciar Soler is very large, probably because of variation in the amount of basal sliding.

To investigate short-term flow-pattern variations of a temperate glacier, longitudinal surface strain was measured with a wire strainmeter in the ablation area of Koryto glacier, Kamchatka, Russia. Strain-rate anomalies were observed in late summer 2000 that were triggered by a water overflow from a moulin near the measurement site followed by the drainage of accumulated water. The strain event started with (compressive) strain rates of >–10–3 d–1 lasting for 6 hours, which then became tensile. Similar strain-rate variations were observed again on the next day. During the event, basal sliding speed measured at the margin in the lower reach of the glacier fluctuated by about ±50% of the daily mean. Smaller and larger sliding speeds corresponded to the compressive and tensile surface strains, respectively. These measurements suggest that the storage and sudden drainage of water caused spatially non-uniform water-pressure fluctuations along the glacier, changing the sliding regime over short time periods.

To complement a technique to detect internal structures of seasonal snow covers and glacier firn with ground-penetrating radar (GPR), we carried out calibration experiments and an observation of winter snow cover (5.7m thick dry snow with numerous ice layers) with an 800 MHz GPR. In particular, we aimed to discriminate periodic noise, which is inherent in GPR, from radar echoes and to obtain a relationship between the observed reflection strength and the magnitude of density contrasts. Experiments were done in air to evaluate noise levels and receiver characteristics of this system. Based on these, we removed noise from radar echoes in the snow-cover observation. We recognized numerous marked echoes in a noise-free radargram. The depths of these echoes coincided roughly with those of large density contrasts observed in the snow pit. Thus, we argue that the echoes correspond to thin ice layers. Furthermore, the minimum density contrasts detected by this GPR are found to vary from about 100 to 250 kgm–3 at 1–6m depth in the seasonal snow cover.

Glacier and lake variations in the Yamzhog Yumco basin in southern Tibet were studied by integrating series of spatial data from topographic maps and Landsat images at three different times: 1980, 1988/90 and 2000. The results indicate that the total glacier area has decreased from 218 km2 in 1980 to 215 km2 in 2000, a total reduction of 3 km2 (i.e. a 1.5% decrease). Glacier recession rates were clearly larger in the 1990s than the 1980s due to the warmer climate. The total lake area decreased by about 67 km2 during 1980–90 and increased by 32 km2 during 1990–2000. It is suggested that change of lake area in the basin was rapid and most likely caused primarily by the change in precipitation and evaporation in the basin, and secondarily by the increased water supply from melting glaciers.

We have developed a novel ice-penetrating radar system that can be carried on a backpack. Including batteries for a 3 hour continuous measurement, the total weight is 13 kg. In addition, it operates reliably down to –25°C, has a low power consumption of 24 W, and is semi-waterproof. The system has a built-in-one controller with a high-brightness display for reading data quickly, a receiver with 12-bit digitizing, and a 1 kV pulse transmitter in which the pulse amplitude varies by <0.2%. Optical communications between components provides low-noise data acquisition and allows synchronizing of the pulse transmission with sampling. Measurements with the system revealed the 300 m deep bed topography of a temperate valley glacier in the late ablation season.

Debris-laden basal ice is exposed along an ice cliff near Hamna Glacier, Sôya Coast, East Antarctica. The basal ice is about 6.8 m thick and shows conspicuous stratigraphic features. The upper 5.5 m consists of alternating layers of bubble-free and bubbly ice. δ values of the bubble-free ice layers are enriched by 2.4 ±1.0‰ (standard deviation) for δ18O compared to values of neighboring bubbly ice layers above, and slopes of δ18O vs δD are close to 8. Such layers are suggested to have been formed by refreezing of meltwater in an open system. In contrast, part of the bubbly ice layers shows neutral profiles for stable isotopes, suggesting that these ice masses are undisturbed ice-sheet ice which was not affected by melting and freezing. The massive alternating layers are thus considered to have been formed by folding of refrozen and non-melted layers. The lower 1.3 m consists predominantly of bubble-free massive ice. The profile of co-isotopic values shows a change of about 3.0‰ for δ18O at the interface between bubble-free and bubbly ice. Since the isotopic change occurred over a wider thickness than the upper 5.5 m, the basal ice is suggested to have been formed by refreezing of meltwater on a larger scale than the upper 5.5 m.

The transition of inland to complex ice flow is investigated in the downstream area of Shirase Glacier catchment, East Antarctica. The 250 km long Mizuho Triangulation Chain (MTC; Naruse, 1978), 230 km upstream of the grounding line of Shirase Glacier, is re-analyzed by a force-balance analysis, in combination with balance-velocity estimates. Numerical model experiments were carried out with a two-dimensional thermomechanical higher-order ice-sheet model along a central flowline extending from the ice divide (Dome Fuji) to the grounding line of Shirase Glacier, passing through the MTC. Results show that complex flow originates near the MTC, where longitudinal normal stresses and normal drag in particular play a decisive role in the force balance. The fast-flow area, however, is geologically controlled and confined to the “bottleneck” or ice-flow convergence area, a few tens of kilometres upstream of the grounding line. In between the MTC and the grounding zone, longitudinal normal stress and basal sliding are dominant features of the ice-flow regime.

Based on the field data at Koryto glacier, Kamchatka Peninsula, Russia, we constructed a one-dimensional numerical glacier model which fits the behaviour of the glacier. The analysis of meteorological data from the nearby station suggests that the recent rapid retreat of the glacier since the mid-20th century is likely to be due to a decrease in winter precipitation. Using the geographical data of the glacier terminus variations from 1711 to 1930, we reconstructed the fluctuation in the equilibrium-line altitude by means of the glacier model. With summer temperatures inferred from tree-ring data, the model suggests that the winter precipitation from the mid-19th to the early 20th century was about 10% less than that at present. This trend is close to consistent with ice-core results from the nearby ice cap in the central Kamchatka Peninsula.

Ice-flow velocities were measured at Koryto glacier on Kamchatka Peninsula, Russia, during a 37 day period in the middle of the 2000 melt season. Six survey points from the upper to the lower reaches of the glacier exhibited daily fluctuations in surface horizontal speed with major peaks that appeared at all points.We argue that basal motion is the major cause of flow on Koryto glacier. Downward vertical velocities measured over most of the glacier during the survey period are likely due to shrinking of englacial and subglacial cavities. This result may imply that a large amount of water is deposited in the early summer. Since 1960, Koryto glacier has retreated by 450 m and this retreat has accelerated following a decrease in winter precipitation after the mid 1970s.The glacier has thinned by 10–50 m during the last 40 years.

Surveys of a triangulation chain 250 km in length were carried out in December 1969 and December 1973–January 1974 along the surface contour lines from 2250 m to 2600 m in Mizuho Plateau, East Antarctica. Horizontal velocities were obtained as small values near the Yamato Mountains, while they had maxima of more than 20 ± 0.7 m a –1 around long. 39° E., lat. 72° S. in the drainage of the Shirase Glacier. Submergence velocities showed large values, such as (0.7 to 1)± 0.25 m a–1, in the region along lat. 72° S. from long. 39° E. eastward to long. 43° E. The amount of snow accumulation there, of average thickness 0.2 m a–1, was not enough to compensate for the deficit of the ice mass caused by the submergence flow. It follows that the ice sheet was thinning there. It is suggested that the ice sheet of Mizuho Plateau is in an unstable condition as a whole.

A linear relation between total gas content in ice and the elevation of ice formation (i.e. pore close-off) was obtained from seven shallow ice cores in Mizuho Plateau, Antarctica. The derived relation was applied to the vertical profile of total gas content in a 700 m long ice core at Mizuho Station. A general trend of gradual increase in total gas content was observed from 600 to 200 m in depth, from which toward the upper layer it showed a steep increase. After eliminating the effect of down-slope flow of ice around Mizuho Station, it was estimated that the thickness of the ice sheet decreased by about 350 m at maximum during the last 2000 years. This tendency also appears in the δ18O profile of the same ice core.

Large retreats were revealed for most glaciers in Patagonia, South America, by analyzing satellite images and air photographs. For example, Glaciar O’Higgins retreated 13 km during 41 years from 1945 to 1986 and Glaciar Upsala retreated about 3 km between 1968 and 1990. During the 41 years former period, however, the southern tongue of Glaciar Pio XI advanced by up to 8.5 km and Glaciar Moreno remained almost in a steady state. Considerable ice-thinning rates, from 3.0 to 11 ma−1, were measured by surveying surface profiles in the ablation areas of Tyndall and Upsala glaciers, respectively, during the period from 1985 (or 1990) to 1993. The ice thickness of Glaciar Moreno, however, has changed very little.

Numerical experiments using a simple mass-balance model show that a 100 m rise in the equilibrium-line altitude due to climatic change would result in about a 200–350 m rise in the frontal altitude at Glaciar Upsala corresponding to a retreat of 5–8 km, while it would cause only about a 70–100 m rise at Glaciar Moreno. The large difference between these two neighbouring glaciers results from the difference in contributions of the calving amount to the total mass balance, as well as the difference in the altitudinal distributions of drainage areas.

Short-term variations in ice-flow velocity were obtained at intervals of a few hours and a few days in the ablation area of Glaciar Soler, Patagonia, Chile, in November 1985. A maximum flow rate was measured at about four times the minimum value. A good correlation, with a time lag of 7.5 h, was found between the ice-flow velocity in the lower reaches and the amount of water discharge from the glacier terminus. It was concluded, therefore, that the velocity variations should have resulted from the variations in basal sliding velocity which is strongly controlled by the subglacial water pressure.

Glaciar Upsala, a freshwater calving glacier in southern Patagonia, has been retreating since 1978, and after a drastic recession of about 700 m a−1 in 1994 the retreat seems to have stopped in 1995. A large ice-thinning rate of 11 m a−1 was obtained between 1990 and 1993, by surveying surface elevations near the terminus of Glaciar Upsala. In 1993–94, the thinning was estimated at about 20 m a−1 near the lateral margin. Some possible causes of the thinning behavior are considered.

In the ablation area of Glaciar Perito Moreno, 50 km south of Glaciar Upsala, ablation rates were measured during 110 d in summer 1993–94, and air temperature was continuously recorded throughout 1994. Using a degree-day method with temperature data at the nearest meteorological station, Calafate, annual ablation during the last 30 years was estimated to fluctuate from about 12 ± 2 to 16 ± 2 m a−1 in ice thickness, with a mean of 14 ± 2 m a−1. Thus, the temperature anomaly alone cannot elucidate the thinning of 11 m a−1 at Glaciar Upsala. As a possible mechanism of the ice-thinning, it is suggested that the considerable retreat due to calving may have resulted in reduction of longitudinal compressive stress exerted from bedrock rises and islands near the glacier front, causing a considerable decrease in the emergence flow. Thus, the ice may have thinned at a rate close to the annual ablation rate.

The horizontal divergence of drifting snow was estimated from the ice-sheet topography on Mizuho Plateau, East Antarctica. The calculation was made by using a relationship between the snow-drift transport rate and wind speed estimated from the surface slope. The divergence thus estimated for Mizuho Station (70°42′S, 44°20′E) was consistent with observations of surface net mass balance, precipitation and sublimation. Around the southern region of the Yamato Mountains, a large divergence was predicted and this is believed to be the principal cause of the bare ice field. Other factors in the formation and preservation of the bare-ice area are discussed.

The surface structure and morphpology of the Soler Glacier, an outlet glacier located on the eastern side of the Patagonia Northern Icefield, were mapped and analysed, using near-vertical, aerial photographs, taken with a hand-held, 6x6 cm-format camera, in January, 1984. The major findings, which could hardly be obtained in the field, included identification of the five ice bodies and four sets of ogive patterns. The pattern and distribution of crevasses were also analysed. From the number and spacings of the ogives, the mean, annual, surface-flow rate was deduced to be about 100 m and 350 m, at points 1.4 km and 6.6 km from the snout, respectively, with an average of 160 m for the middle reach.

Sorting effects of snow particles during deposition were studied in field observations of snow cornices and wind-tunnel experiment of snow drifts. Grain size, density and hardness were larger at the upper part (root) of a cornice than at the lower part (scarp). Experiments with the use of a horizontal step in a wind-tunnel revealed the importance of redistribution of snow particles on the formation of drifts: at wind speed of 5 m/s, about 40% of particles fallen onto the surface behind a 0.1-m high step were removed by erosion, rebound and creep. The surface mass balance controlling the growth and shape of a drift are briefly discussed.