[DLS] Luke Zoet (UW-Madison)

“How Debris Laden Basal Ice Alters Glacier Slip”

The basal ice of glaciers often contains abundant volumes of sediment (debris) that affect how glaciers interact with their underlying beds. Despite empirical evidence suggesting debris may contribute as much as 50% of the overall resistance to glacier motion, the effects of debris are neglected in treatments of glacier motion. In part, this omission is due to a lack of understanding of how the debris changes the frictional properties of the bed, stemming in part from the difficulty of measuring such effects in the field. Here, we use a combination of numerical modeling and laboratory experimentation to isolate the role debris plays in affecting the slip response of ice over both “hard” beds (comprised of crystalline rocks) and “soft” beds (comprised of unlithified sediment). We first use experiments in a novel large-diameter cryosphere ring shear device to constrain the dominant physical processes and then integrate those physical processes into full Stokes numerical models capable of expanding the results to realistic subglacial terranes. We find that debris has contrasting effects on glacier slip for hard vs soft beds. For slip over hard beds, debris generates a rate strengthening behavior, whereas for soft beds, debris drives the system closer to a Coulomb behavior.

EAPS Department Lecture Series —

Weekly talks aimed to bring together the entire EAPS community, given by leading thinkers in the areas of geology, geophysics, geobiology, geochemistry, atmospheric science, oceanography, climatology, and planetary science. Runs concurrently with class 12.S501.

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