The impact of proglacial lakes on the retreat of mountain glaciers: Rhonegletscher, Switzerland

In a warming climate with many glaciers retreating, proglacial lakes may form if either a moraine dams the water or the terminus retreats across a basal depression. In the Alps, the number of such lakes is expected to increase considerably in the closer future. This introduces an ablation mechanism which formerly was of very little significance on alpine glaciers: Calving into proglacial lakes may enhance mass loss and considerably accelerate glacial retreat.

The mechanism finally causing icebergs to break off is not fully understood yet. Calving is strongly related to basal sliding, which in turn is related to the subglacial hydraulics. A better understanding of these process-interactions to better constrain the numerical models is required to enable better prediction of the response of glaciers to climatic warming.

Rhonegletscher, Swiss Alps, has recently retreated behind a rock riegel; a proglacial lake started to form for the first time in 2005. In the future an accelerated retreat through a basal depression involving the formation of a calving front is expected. The tongue of Rhonegletscher therefore offers a unique opportunity to study the retreat of an Alpine lake-terminating glacier, the involved fracturing processes and the calving mechanism.

The goal of the project is the development of a model of freshwater calving using a damage mechanics approach. Theoretical and modeling research will be combined with field measurements on Rhonegletscher, in order to constrain and validate the obtained models.

Collaboration:

Dr. Shin Sugiyama (Institute of Low Temperature Science, Hokkaido University)

Dr. Andreas Vieli (Durham University)