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SUMMARY:Karol Bacik - Sand Dunes and Their Interactions Kasia Warburton - 
 Glacial Squeegee: Tidal Effects on Subglacial Hydrology - Karol Bacik\, DA
 MTP and Kasia Warburton\, DAMTP
DTSTART:20191024T103000Z
DTEND:20191024T113000Z
UID:TALK130684@talks.cam.ac.uk
CONTACT:Catherine Pearson
DESCRIPTION:Sand Dunes and Their Interactions\n\nDunes are coherent sedime
 ntary structures which arise spontaneously due to the dynamical interplay 
 between granular matter and the flow of the overlaying fluid. Natural dune
 s rarely occur in isolation\, but usually form vast dune fields. As of now
 \, the mechanisms which regulate the large scale organisation of such dune
  fields are poorly understood. In particular it is unclear if the dune con
 figurations we observe are stable or transient. In this talk I will discus
 s some recent experimental results on quasi-2D dune corridors. In our expe
 riments dune corridors are robust and their structure appears to be stabil
 ised by long-range dune-dune interactions. Indeed\, by altering the flow\,
  aqueous dunes strongly affect the shape and the migration rate of their d
 ownstream neighbours which leads to an effective dune-dune repulsion. In m
 y presentation I shall discuss the repulsion mechanism in detail and explo
 re its consequences for the system-level dynamics.\n\nGlacial Squeegee: Ti
 dal Effects on Subglacial Hydrology\n\nGlacier speed is sensitive to fluct
 uations in subglacial water pressure. For marine ice sheets\, the tidal cy
 cle is linked to the upstream pressure fluctuations as water enters and ex
 its the subglacial environment across the grounding line.\nI will discuss 
 a model of grounding line migration based on the propagation of fluids und
 er elastic sheets. Travelling wave solutions exist for the up- and downstr
 eam migration. Differences in the dynamical processes governing the fluid 
 flow at a small scale leads to an asymmetry in grounding line migration on
  a much larger scale. I will discuss the effects of this in relation to ob
 servations from the Rutford Ice Stream.
LOCATION:Open Plan Area\, BP Institute\, Madingley Rise CB3 0EZ
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