Skip to main content Accessibility help
×
Home

Bed reflectivity beneath inactive ice streams in West Antarctica

  • Ginny A. Catania (a1), Howard B. Conway (a1), Anthony M. Gades (a1), Charles F. Raymond (a1) and Hermann Engelhardt (a2)...

Abstract

Radio-echo sounding (RES) techniques are used to examine spatial changes in bed reflectivity across relict ice streams inWest Antarctica. Measurements from adjacent interstream ridges are used to correct the measured power returned from the bed for attenuation and losses due to geometric spreading, scattering and absorption. RES measurements near boreholes drilled on Ice Stream C (ISC) indicate high coefficients of bed reflectivity (R > 0.1) in locations where the bed was thawed and boreholes connected to the basal water system, and low reflectivity coefficients (R < 0.02) at locations that were frozen and not connected. Intermediate values of bed reflectivity were measured at locations where the connection to the basal water system was weak. Measurements across four relict margins show that bed reflectivity usually jumps from low to high values several kilometers inside the outermost buried crevasses. We interpret this to be a transition from frozen to thawed basal conditions and discuss implications of these observations.

  • View HTML
    • Send article to Kindle

      To send this article to your Kindle, first ensure no-reply@cambridge.org is added to your Approved Personal Document E-mail List under your Personal Document Settings on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part of your Kindle email address below. Find out more about sending to your Kindle. Find out more about sending to your Kindle.

      Note you can select to send to either the @free.kindle.com or @kindle.com variations. ‘@free.kindle.com’ emails are free but can only be sent to your device when it is connected to wi-fi. ‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.

      Find out more about the Kindle Personal Document Service.

      Bed reflectivity beneath inactive ice streams in West Antarctica
      Available formats
      ×

      Send article to Dropbox

      To send this article to your Dropbox account, please select one or more formats and confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your <service> account. Find out more about sending content to Dropbox.

      Bed reflectivity beneath inactive ice streams in West Antarctica
      Available formats
      ×

      Send article to Google Drive

      To send this article to your Google Drive account, please select one or more formats and confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your <service> account. Find out more about sending content to Google Drive.

      Bed reflectivity beneath inactive ice streams in West Antarctica
      Available formats
      ×

Copyright

References

Hide All
Bentley, C. R., Lord, N. and Liu, C.. 1998. Radar reflections reveal a wet bed beneath stagnant Ice Stream C and a frozen bed beneath ridge BC, West Antarctica. J. Glaciol., 44(146),149156.
Conway, H., Catania, G., Raymond, C., Scambos, T., Engelhardt, H. and Gades, A.. 2002. Switch of flow direction in an Antarctic ice stream. Nature, 419(6906), 465467.
Copland, L. and Sharp, M.. 2001. Mapping thermal and hydrological conditions beneath a polythermal glacier with radio-echo sounding. J. Glaciol., 47(157), 232242.
Echelmeyer, K. A. and Harrison, W. D.. 1999. Ongoing margin migration of Ice Stream B, Antarctica. J. Glaciol., 45(150), 361369.
Echelmeyer, K. A., Harrison, W. D., Larsen, C. and Mitchell, J. E.. 1994 .The role of the margins in the dynamics of an active ice stream. J. Glaciol., 40(136), 527538.
Engelhardt, H. and Kamb, B.. 1997. Basal hydraulic system of aWest Antarctic ice stream: constraints from borehole observations. J. Glaciol., 43(144), 207230.
Engelhardt, H., Humphrey, N. and Kamb, B.. 1990a. Borehole geophysical observations on Ice Stream B, Antarctica. Antarct. J. U.S., 25(5),8082.
Engelhardt, H., Humphrey, N., Kamb, B. and Fahnestock, M.. 1990b. Physical conditions at the base of a fast moving Antarctic ice stream. Science, 248(4951), 5759.
Gades, A. M. 1998. Spatial and Temporal Variations of Basal Conditions Beneath Glaciers and Ice Sheets Inferred From Radio Echo Soundings. (Ph.D. thesis, University of Washington.)
Gades, A.M., Raymond, C.F., Conway, H. and Jacobel, R.W.. 2000 .Bed properties of Siple Dome and adjacent ice streams, West Antarctica, inferred from radio-echo sounding measurements. J. Glaciol., 46(152), 8894.
Jacobson, H.P. and Raymond, C. F.. 1998. Thermal effects on the locationof ice stream margins. J. Geophys. Res.,103(B6), 12,11112,122.
Kamb, B. 2001. Basal zone of the West Antarctic ice streams and its role in lubrication of their rapid motion. in Alley, R. B. and Bindschadler, R. A., eds. The West Antarctic Ice Sheet: Behavior and Environment. Washington, American Geophysical Union,157199. (Antarctic Research Series 77.)
Raymond, C. 1996. Shear margins in glaciers and ice sheets. J. Glaciol., 42(140),90102.
Raymond, C. F., Echelmeyer, K. A., Whillans, I. M. and Doake, C. S. M.. 2001. Ice stream shear margins. in Alley, R. B. and Bindschadler, R. A., eds. The West Antarctic Ice Sheet: Behavior and Environment. Washington, American Geophysical Union,137155. (Antarctic Research Series 77.)
Retzlaff, R. and Bentley, C. R.. 1993 .Timing of stagnation of Ice Stream C, West Antarctica, from short-pulse radar studies of buried surface crevasses. J. Glaciol., 39(133), 553561.
Smith, B. 2000. Radar Studies On Ice Stream C, West Antarctica. (M.Sc. thesis, University of Wisconsin–Madison.)
Tulaczyk, S.M., Kamb, B. and Engelhardt, H. F.. 2000a. Basal mechanics of Ice Stream B,West Antarctica. I.Till mechanics. J. Geophys. Res.,105(B1), 463481.
Tulaczyk, S.M., Kamb, B. and Engelhardt, H. F.. 2000b. Basal mechanicsof Ice Stream B, West Antarctica. II. Undrained-plastic-bed model. J. Geophys. Res.,105(B1), 483494.
Winebrenner, D. P., Smith, B., Catania, G., Conway, H. and Raymond, C.F.. In press. Radio-frequencyattenuationbeneath Siple Dome,West Antarctica, from wide-angle and profiling radar observations. Ann. Glaciol., 37.

Metrics

Full text views

Total number of HTML views: 0
Total number of PDF views: 0 *
Loading metrics...

Abstract views

Total abstract views: 0 *
Loading metrics...

* Views captured on Cambridge Core between <date>. This data will be updated every 24 hours.

Usage data cannot currently be displayed