Subglacial drainage and slip modeling in Antarctica: relating lakes to ice discharge
This award supports a project to develop models of subglacial hydrology in order to understand dynamics of water movement, lake drainage, and how drainage affects ice slip over deformable till with the goal of understanding present and future behavior of fast flowing regions of Antarctica. Drainage of subglacial water falls into two broad categories: distributed and channelized. In distributed systems, water is forced out along the ice?bed interface. Conversely, in channelized systems water is drawn toward a few major arteries. Observations of lake filling and draining sup- port changes in subglacial water flow and suggest a switch from a low to high discharge state or vice versa. Filling or draining can move the subglacial system from one type of drainage morphology to the other. A switch of drainage type will affect slip along the ice-bed interface because distributed morphologies tend to cause enhanced sliding whereas channelized morphologies tend to cause enhanced coupling of the ice-bed interface. Conditions beneath fast flowing ice streams of West Antarctica are ideal for switching between subglacial drainage morphologies. Fast flowing ice in West Antarctica commonly rests on sub- glacial tills and is coincident, in some areas, with observed subglacial lake filling and draining. The goal of the work is to develop the next generation of spatially distributed hydraulic models that capture lake filling and draining phenomena and investigate the effects on subglacial till. Models will be theoretical, process-based descriptions of water drainage and till failure along fast flowing ice streams. Models will be based on balance of mass, momentum, and energy. Building on previous studies, we will incorporate two dimensional movement of water to investigate distributed basal hydrology, distributed basal hydrology coupled to channels, and couple these models with till deformation. These models will provide a framework for determining how lake draining and filling affects ice discharge by providing a constraints on ice?bed coupling. The intellectual merit of the work is that it will advance knowledge about drainage of water subglacially beneath Antarctica and how water affects ice motion. Our modeling provides a unique opportunity to understand the role subglacial hydrology plays in the dynamics of key outlet glaciers and ice streams. The broader impacts of the work include training for one postdoctoral scientist and training for a summer student in simple laboratory techniques for analog experiments. In addition, the proposal dovetails into an existing polar education and outreach plan by including a component of physical, numerical, and scale models in programs developed for high school and middle school classroom visits, teacher workshops and community events. Additionally, because knowledge of glacial hydrology is increasing rapidly, we will convene a workshop on observations and models of subglacial hydrology to facilitate transfer of knowledge and ideas.
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