Experimental investigation of channelised subglacial flow and till dynamics (LEAD)

For till-​bedded glaciers, subglacial flow and till dynamics are intrinsically connected. While subglacial flow is a feature of glacier drainage, till dynamics can be understood as the temporal evolution of the underlying sediment due to water flow. Subglacial water flow has major impacts on the hydrographs of proglacial streams, on basal sliding and glacier motion, as well as on the dynamics of glacial lake outbursts. Together with till dynamics, the processes affect sediment uptake and evacuation from glacierised environments. Directly accessing the subglacial environment is very difficult and thus, corresponding observations remain scarce. As a consequence, numerical models that aim at representing subglacial processes are poorly tested, and often rely on decades-​old parameterisations.

The goal of this project is to overcome these shortcomings by investigating the hydrological and mechanical conditions beneath a till-​bedded glacier with physical experiments. For this end, a new laboratory flume will be constructed, in which pressure is applied to the till simulating the weight of a glacier. At the same time, water is allowed to flow along the till-​ice boundary. In the early stages of the experiment, we use an ice substitute in order to avoid the otherwise necessary cooling of the entire setup. The new flume will allow for current theories related to till dynamics and the subglacial drainage under till-​bedded glaciers to be tested in a controlled environment, and to precisely constrain some key parameters of the related processes. The goal of this project is to overcome these shortcomings by investigating the hydrological and mechanical conditions beneath a till-​bedded glacier with physical experiments.