The dynamics of ice-sheet outlets

摘要: A comparison of data from aircraft altimetry, Landsat imagery, and radia echo-sounding has shown characteristic surface topographies associated with sheet stream flow. The transition between the two is abrupt occurs at a step in subglacial topography. This marks onset basal sliding high velocities caused by water; it results crevassed amphitheatre-like basins round head outlet glaciers. It also zone maximum driving stress beyond which values decline rapidly as increase. appears to be topographically controlled since temperatures are pressure-melting point well inland change regime. Marie Byrd Land ice streams exhibit qualitative differences other ice-sheet outlets, however; lower stresses much more gradual several hundred kilometres inland. Such have particularly low slopes appear form flow regime resemble confined shelves rather than grounded ice. repeated association rapid distinct feature implies stabilizing effect on discharge through Acceleration pinned propagation this seems improbable. Rapid trenches may ensure relatively permanent trough accentuation erosion. concentrated towards heads glaciers up-stream region where significant decoupling occurs. mechanism for overdeepening fjords their ends development very steep fjord headwalls.