The distribution of basal motion beneath a High Arctic polythermal glacier

The longitudinal pattern of surface velocity of a large, predominantly cold, polythermal glacier (John Evans Glacier, Ellesmere Island, Canada) was measured over summer and winter periods. In the accumulation and upper ablation areas, where ice is predominantly cold-based, summer velocities were slightly higher than overwinter velocities. Predicted velocities due to ice deformation alone in these areas closely matched these observations in the winter, with limited basal motion likely in the summer. In the lower ablation area, where ice is likely warm-based, measured summer velocities were up to double overwinter velocities. Predicted ice deformation could not account for all of these measured velocities in either summer or winter. This suggests that basal motion occurs throughout the year over at least part of the lower ablation area. This finding is supported by radio-echo sounding, subglacial drainage reconstructions and analyses of early-summer meltwater chemistry, which suggest that subglacial water is present throughout the year in this region. In summer, basal motion may account for up to 75% of the total surface velocity throughout the lower ablation area. The inferred rate of basal motion increases sharply directly below a set of moulins by which most surface meltwater reaches the glacier bed.

Spring Meltwater Mixing in Small Arctic Lakes

Meltwater mixing in small arctic lakes at Saqvaqjuac (63°68′N, 90°40′W) was studied in 1980 and 1981 to evaluate the applicability of theoretical lake water renewal times to the modeling of ice-covered lakes. Two 370-GBq tritium additions were made to 7.09-ha P&N Lake. One was mixed with the unfrozen water at the time of maximum lake-ice thickness (May 1980) and the other was mixed with the lake immediately after freezing (October 1980). Dye experiments were also performed at four lakes to define the spatial and temporal distribution of the inflow and icemelt layers. Results from the tritiated water and dye addition experiments, as well as conductance and temperature profiles, showed that during ice-on, the cold low-density meltwater floated in a thin layer 0–100 cm beneath the ice, extended over the entire subice-surface area, and left the lake without mixing with the heavier subice water. These results imply that (1) lake models incorporating a lake flushing rate term need to be reevaluated to accommodate the lack of meltwater mixing beneath spring ice and (2) more attention should be given to the early spring meltwater chemistry and its distribution within the upper lake strata.

Glacier meltwater chemistry at two sub-polar glaciers in West Greenland

As part of a glacier hydrological study electrical conductivity of meltwaters from two subpolar glaciers was investigated. The dissolved load of a melt stream reflects the mixing, in varying proportions through time, of waters with different chemical characteristics from different environments (Collins, 1977). Conductivity, a surrogate measure of the concentration af total dissolved solids, was used as an indicator af the nature af subglacial and englacial hydrochemical environments and of different meltwater routings through the glaciers. The investigation was carried out at Qamanârssup sermia, an outlet glacier from the Inland Ice, in 1981 and at Kitdlerssuaq, on an outlet glacier from a local ice cap, in 1982 and 1983 (fig. 45). All conductivity values are reported at the measuring temperature, i.e. 0-2°C for glacier meltwater.