Twelve-year cyclic surging episode at Donjek Glacier in Yukon, Canada
Abstract:Surge-type glaciers exhibit several-fold to orders-of-magnitude speed-up during the short active phase, resulting in km-scale terminus advance. Although there are many surge-type glaciers near the border of Alaska and the Yukon, the generation mechanisms remain uncertain because of limited and few continuous observations. To better understand the surge dynamics and predict the next event, it is essential to examine the entire surge cycles. Here we use Landsat optical imageries to reveal the long-term evolutions, and report three surging episodes at Donjek Glacier in Yukon, Canada.
Using the Landsat images, we found three surging events in 1989, 2001, and 2013. In the 2001 event, the surface speed significantly increased by up to 4.5 m/d; during the quiescent phases it was ~0.5 m/d at the terminus. While the duration of active phase is about 4~5 and 2~3 year in the 2001 and 2013 events, the period in the 1989 event is unclear because of the lack of high temporal resolution data. Remarkably, the surging area is limited to the ~20-km section from the terminus instead of the entire glacier. Moreover, we examined the terminus area changes from 1975 to 2014. Although the area has been secularly decreasing probably due to the tread of global warming, it has also revealed four significant fluctuations during the nearly forty years. Comparing the speed and the area changes, the three speed-up events correspond to the terminus area fluctuations with a few time lags.
It turns out that the surge event has been quite regularly repeating every twelve years. Although the behavior is rather similar to that in Svalbard glaciers in terms of maximum speed and unclear initiation season, the recurrence interval is much shorter than other nearby surges. Considering that the surge events seem to have initiated around significantly narrower area than upstream, the strong valley constriction may control the regularity as well as the twelve-year recurrence time.