Glaciers can be divided into two classes according to their flow behavior: normal (relatively steady annually averaged flow rate) and surge-type (pronounced cyclic flow variations having a typical periodicity of 10-100 years). We have examined the population statistics of 2356 glaciers in the St. Elias Mountains, Yukon Territory, Canada, and estimate that 151 (6.4%) of these glaciers are surge-type. To explore how various glacier attributes are associated with surging, we compare the probability of surging associated with various subsets of the complete population to appropriate reference values. In this way, potential influences on surge tendency can be examined. For the 55 drainage basins analyzed, there is a pronounced spatial variation in the concentration of surge-type glaciers, but no obvious environmental control can be evinced. Within the study area the greatest concentration lies in the northern St. Elias Mountains, a region of high topographic elevation that is experiencing rapid tectonic uplift. Analysis of the influence of length on surge tendency reveals that long glaciers have a significantly greater probability of being surge-type than short glaciers. The surge probability increases monotonically from 0.61% for very short glaciers (0-1 km) to 65.1% for long glaciers (10-75 km). This result suggests that ice sheets and ice caps, or at least portions of them, should have a high probability of surging. Tributary glaciers have a greater tendency to surge than trunk glaciers, presumably because they may themselves be surge-type and may additionally participate in surges of the trunk glacier. The nonrandom geographical distribution of surge-type glaciers is not simply a consequence of the variation from basin to basin of the glacier length distribution. Surge-type glaciers tend to have a higher overall elevation than normal glaciers: the elevation of the highest point of the accumulation zone, the elevation of the snow line, and the elevation of the lowest point of the ablation zone, on average, exceed the corresponding elevations for normal glaciers. There is no significant difference between the overall slopes of surge-type and normal glaciers, although there is a tendency for surge-type glaciers to have greater slope in the accumulation zone and lesser slope in the ablation zone than normal glaciers. Although the prevalent flow direction for glaciers in the Yukon data set is to the north, surge-type glaciers tend to flow to the east and southeast. This orientation influence is probably explained by the fact that many of the longest glaciers also flow to the east and southeast. Papernumber 5B5680. 0148-0227/86/005 B 5680505.00 fled 204 surge-type glaciers in western North America, and all are located in the mountain ranges of Alaska, Yukon Territory, and northwestern British Columbia, the majority being s•tuated in the St. Elias Mountains near the Alaska Yukon border. No surging glaciers are found in ranges to the south such as the Coast Mountains, the Selkirk Mountains, and the Rocky Mountains. Other ...

Preliminary results from a multiple-traverse radar survey across an ice cap situated on top of Hoodoo Mountain, a Quaternary subglacial stratovolcano in northwestern British Columbia are presented. The project defined the shape of the ice sheet and mapped the subglacial summit region of the volcano. Four traverses, using low-frequency ice radar and higher frequency ground-penetrating radar units, provided traces of the ice base as well as shallow, finer scale, internal reflectors. GPS was used to locate survey lines and individual radar traces were time tagged to position. The ice cap has a relatively even thickness (120-150 m) across the summit region, with no evidence of a deep crater or caldera beneath. The minimum volume of ice is estimated at 3.2 km3. To more accurately gauge the potential for significant jökulhlaups at Hoodoo Mountain, additional work is necessary to define the nature and size of subglacial catchments basins.

One of the main aims of the Snow and Ice Hydrology Project, a joint Canada-Pakistan endeavour, is to estimate ice loss in the ablation areas of glaciers in order to predict with greater confidence stream flow in the headwaters of the Indus River. To this end, Miar Glacier, located in the central Karakoram Range, north of Gilgit, was intensively studied during the summers of 1986 and 1987. Measurements of glacier mass balance by the monitoring of accumulation and ablation at stake locations is very difficult in the Himalyan environment. It is usually almost impossible to reach elevations above the equilibrium line without major effort, and always very difficult once there to make meaningful measurements; the ablation areas are often heavily crevassed and/or debris-covered, and this poses difficult sampling problems. The method used in this study was to monitor annual surface movement on a cross-profile as near as possible to the equilibrium line. The measurements, obtained in conjunction with depth soundings made on the same profile, allow the annual ice flux through the cross-profile to be calculated. If an approximately steady-state glacier is assumed, it would be expected that this flux would be roughly equivalent to the rate of ice loss below the profile. The movements of wooden stakes drilled into the glacier were monitored throughout each of the summers and, since two of the stakes survived the intervening winter, this allowed calculation of annual movement. Distances between the crests of ogives were also surveyed, providing an independent assessment of glacier movement. Depth measurements by radio-echo sounder were successfully made in the summer of 1987, showing maximum ice depths of 550 m. The annual ice flux through the transverse profile was estimated as 5.67 × 107 m3, which corresponds to a mean annual ice loss from the glacier surface below the profile of 8.10 m of ice.

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