9725882 Raymond This award is for support for a program of surface-based radio echo sounding to examine the geometry of the internal layering and the presence or absence of thawed zones outside the margins of active Ice Streams B and E and across the flow band feeding Ice Stream D. Melting in the marginal shear zone and/or on the bed outside an ice stream relates to the amount of support of the ice stream from the sides compared to the bed and the conditions that limit expansion of its width. Radar observations will be extended over the crest of adjacent inter-ice-stream ridges (B/C and D/E) and areas next to the flow band in the onset of D. The purpose is to examine internal layering indicative of the histories of these areas adjacent to ice streams and to determine whether ice streams have expanded into these presently stable areas in the past. These goals concerning the physical controls and history of ice stream width relate to how the discharge of ice streams has changed in the past and could change in the future to affect sea level.
