Measurements of surface dynamics on polythermal John Evans Glacier, Nunavut, Canada over two winter periods and every 7-10 days throughout two melt-seasons (June-July 2000, 2001) provide new insight into spatio-temporal patterns of High Arctic glacier dynamics. In the lower ablation zone mean annual surface velocities range from 10-21 m a-1 but peak velocities up to 50 % higher are attained during late-June/early-July. In the upper ablation zone and lower accumulation zone mean annual surface velocities typically range from 10-18 m a-1 and peak velocities up to 40 % higher occur during late July. In the upper accumulation zone, mean annual surface velocities range from 2-9 m a-1 , and motion in mid-late July exceeds this by up to 10 %. Rapid drainage of ponded supraglacial water in the upper ablation zone to an initially distributed subglacial drainage system in mid-June may force excess surface motion in the warm-based lower glacier. The data indicate that the duration of the velocity response may be related to the rate of channelisation of the basal drainage, and the velocity response may be transmitted upglacier by longitudinal coupling. An increase in surface velocities in the middle glacier in late July occurs in conjunction with the opening of two further moulins in the accumulation zone.
|Translated title of the contribution||Intra-annual and intra-seasonal flow dynamics of a High Arctic polythermal valley glacier|
|Title of host publication||Symposium on Physical and Mechanical Processes in Ice in Relation to Glacier and Ice-Sheet Modelling, Chamonix-Mont-Blanc, France|
|Publication status||Published - 2002|