HR: 1340h
AN: C13B-1076    [Abstracts]
TI: Time variability of radar reflections from englacial and subglacial waters
AU: * Brown, J M
EM: joelmb9877@msn.com
AF: University of Montana Department of Geosciences, 32 Campus Dr #1296, Missoula, MT 59812 United States
AU: Harper, J T
EM: joel@mso.umt.edu
AF: University of Montana Department of Geosciences, 32 Campus Dr #1296, Missoula, MT 59812 United States
AU: Bradford, J H
EM: jbradfor@boisestate.edu
AF: Boise State University Department of Geosciences, 1910 University Dr., Bosie, ID 83725-1535 United States
AU: Humphrey, N F
EM: neil@uwyo.edu
AF: University of Wyoming Department of Geosciences, Dept. 3006, University of Wyoming, Laramie, WY 82071 United States
AB: We have conducted radar imaging at Bench Glacier, Alaska aimed at investigating englacial and subglacial waters. Repeat measurement intervals span years, seasons, days, and hours. Data are included from a logging system that continuously collects radar traces. We used four radar systems, a range of frequencies from 5-100 Mhz, and a variety of data collection techniques. The radar data were collected in conjunction with observations made in over 50 boreholes drilled through the ice. We found variations in englacial scattering events dependent on season and time of day. In radar images collected in June of different years, with two different radar systems and two different frequencies, layering based on scattering events was evident. Two distinct layers were present within the glacier: an upper layer defined by a notable lack of scatterers and high radar velocity, and a lower layer defined by numerous scatterers and relatively low radar velocity. The boundary between the two layers is abrupt, and ranges in depth from 20 to 50 m below the glacier surface. Many of the scatterers are large (i.e. meters in diameter). This is indicated by imaging of the top and bottom of some of these events in 25 and 100 MHz data, and by the fact that the long wavelength of the 5 MHz systems detected the features. Our repeated measurements elucidate changes in englacial and subglacial water processes over time scales of hours to seasons.
DE: 0720 Glaciers
DE: 0758 Remote sensing
DE: 0776 Glaciology (1621, 1827, 1863)
DE: 1621 Cryospheric change (0776)
DE: 1863 Snow and ice (0736, 0738, 0776, 1827)
SC: Cryosphere [C]
MN: Fall Meeting 2005