Current knowledge concerning the impact of subglacial hydrology on the dynamics of polythermal glaciers is limited. Conventional wisdom suggests that subglacial hydrology has a negligible influence on surface patterns of ice dynamics in polar regions, due mainly to the presence of cold, impermeable surface ice layers which prevent large seasonal supraglacial meltwater inputs from reaching the bases of polythermal glaciers. However, recent research has suggested a) that subglacial hydrology exerts a major influence on ice dynamics throughout temperate glaciers, and b) that many Arctic glaciers may experience considerable subglacial water flow. During summer 2000, intensive field investigations were undertaken at John Evans Glacier, a polythermal valley glacier situated on Ellesmere Island in the Canadian High Arctic (79Â°40'N, 74Â°00'W) to i) characterise the subglacial hydrology of the glacier and determine the extent to which it evolved over the course of a melt season, and ii) establish whether variations in subglacial hydrology affected rates of glacier motion. Known quantities of fluorescent dye were periodically injected into the englacial system via moulins, and dye emergence was detected in a single stream emerging from the terminus 5 km downglacier. Early in the season (late June), dye returns were highly dispersed and dye velocities were low (~0.14 ms-1), implying that inefficient distributed drainage was taking place. Later in the season (late July), dye experienced little dispersion, and dye transit velocities reached 0.7 ms-1, suggesting that the subglacial drainage had evolved into an efficient, channelised system. Measurements of surface glacier motion across the lower glacier area were made on a two-daily basis throughout the field season and show highest horizontal velocities occurring in conjunction with vertical uplift of a number of motion stakes during late June. We hypothesise that the surface motion variations are directly related to the seasonal evolution of the subglacial drainage system. Given the sensitivity of Arctic regions to climate change and the resultant impetus to model such potential change, these conclusions suggest that the critical role of subglacial hydrology on ice dynamics in polar regions cannot be neglected.
|Translated title of the contribution||Seasonal evolution of the subglacial drainage system within a High Arctic polythermal valley glacier, as revealed by dye-tracing studies|
|Title of host publication||International Glaciological Society, British Branch Meeting, British Antarctic Survey, Cambridge|
|Publication status||Published - 2001|