The Cryosphere Discussions www.the-cryosphere-discuss.net 1994-0432 1994-0440 4 3 2010 10.5194/tcd-4-1225-2010 http://www.the-cryosphere-discuss.net/4/1225/2010/ http://www.the-cryosphere-discuss.net/4/1225/2010/tcd-4-1225-2010.html http://www.the-cryosphere-discuss.net/4/1225/2010/tcd-4-1225-2010.pdf 1225 1241 2010-08-11 A comparison of basal reflectivity and ice velocity in East Antarctica R. W. Jacobel jacobel@stolaf.edu K. E. Lapo J. R. Stamp B. W. Youngblood B. C. Welch J. L. Bamber Department of Physics, St. Olaf College, Northfield, MN, 55057, USA School of Geographical Sciences, University of Bristol, Bristol, BS8 1SS, UK Ground-based radio echo sounding data acquired along the 1700 km US-ITASE traverse have been used to determine ice attenuation and relative basal reflectivity across the major catchments funneling ice from East Antarctica to the Ross Ice Shelf. We find that basal reflectivity varies locally by up to 40 dB which we interpret as due to changes in the phase state at the bed. Some, though not all, areas of high local reflectivity are observed to have flat-lying bed reflections indicative of sub-glacial lakes. We compare basal reflectivity to ice balance velocity and find a general association of higher flow speeds with high radar reflection strength. This set of observations from two independent remotely sensed geophysical data sets extends the range of field observations to the interior of East Antarctica and confirms the importance of basal lubrication on modulating the ice dynamics of the largest ice sheet on the planet. Bamber, J. L., Gomez-Dans, J. L., and Griggs, J. A.: A~new 1 km digital elevation model of the Antarctic derived from combined satellite radar and laser data – Part~1: Data and methods, The Cryosphere, 3, 101–111, \doi10.5194/tc-3-101-2009, 2009. Bell,~R E.: The role of subglacial water in ice-sheet mass balance, Nat. Geosci., 1, 297–304, \doi10.1038/ngeo186, 2008. Bell,~R E., Studinger,~M., Shuman,~C A., Fahnestock,~M A., and Joughin,~I.: Large subglacial lakes in East Antarctica at the onset of fast-flowing ice streams, Nature, 445(7130), 904–907, \doi10.1038/nature05554, 2007. Blankenship,~D D., Morse,~D L., Finn,~C A., Bell,~R E., Peters,~M E., Kempf,~S E., Hodge,~S M., Studinger,~M., Behrendt,~J C., and Brozena,~J M.: Geological controls on the initiation of rapid basal motion for the West Antarctic Ice Streams: a~geophysical perspective including new airborne radar sounding and laser altimetry results, Antar. Res S., 77, 105–121, 2001. Budd,~W F. and Warner,~R C.: A~computer scheme for rapid calculations of balance-flux distributions, Ann. Glaciol., 23, 21–27, 1996. Carter,~S P., Blankenship,~E E., Young,~D A., Peters,~M E., Holt,~J W., and Siegert,~M.: Dynamic distributed drainage implied by the flow evolution of the 1996–1998 Adventure Trench subglacial lake discharge, Earth Planet. Sc. Lett., 283, 24–37, \doi10.1016/j.epsl.2009.03.019, 2009. Edwards,~L.: Antarctic ice velocities from satellite observations: generation, validation and application, PhD thesis, University of Bristol, 267~pp., 2009. Fahnestock,~M., Abdalati,~W., Joughin,~I., Brozena,~J., and Gogineni,~P.: High geothermal heat row, basal melt, and the origin of rapid ice how in Central Greenland, Science, 294(5550), 2338–2342, \doi10.1126/science.1065370, 2001. Fricker,~H A., Scambos,~T., Bindschadler,~R., and Padman,~L.: An active subglacial water system in West Antarctica mapped from space, Science, 315(5818), 1544–1548, \doi10.1126/science.1136897, 2007. Gades,~A M., Raymond,~C F., Conway,~H B., and Jacobel,~R W.: Bed properties of Siple Dome and adjacent ice streams, West Antarctica, inferred from radio echo-sounding measurements, J Glaciol., 46(152), 88–94, 2000. Jacobel,~R W., Welch,~B C., Osterhouse,~D., Pettersson,~R., and MacGregor,~J A.: Spatial variation of radar-derived basal conditions on Kamb Ice Stream, Ann. Glaciol., 50(51), 10–16, 2009. MacGregor,~J A., Anandakrishnan,~S., Winebrenner,~D P., Catania,~G A., and Joughin,~I.: Multiple bed echoes, englacial radar attenuation, and basal reflectivity across the Siple Coast grounding line, West Antarctica, J Geophys. Res., in review, 2010. MacGregor,~J A., Winebrenner,~D P., Conway,~H., Matsuoka,~K., Mayewski,~P A., and Clow,~G D.: Modeling englacial radar attenuation at Siple Dome, West Antarctica, using ice chemistry and temperature data, J Geophys. Res., 112, F03008, \doi10.1029 /2006 JF000717, 2007. Matsuoka,~K., Morse,~D., and Raymond,~C F.: Estimating englacial radar attenuation using depth profiles of the returned power, Central West Antarctica, J Geophys. Res., 115, F02012, \doi10.1029/2009JF001496, 2010. Mayewski,~P A.: Antarctic oversnow traverse-based Southern Hemisphere climate reconstruction, EOS T. Am. Geophys. Un., 84(12), 205, 2003. Peters,~L E., Anandakrishnan,~S., Holland,~C W., Horgan,~H J., Blankenship,~D D., and Voigt,~D E.: Seismic detection of a~subglacial lake near the South Pole, Antarctica, Geophys. Res. Lett., 35, L23501, \doi10.1029/2008GL035704, 2008. Price,~B., Nagornov,~O V., Bay,~R., Chirkin,~D., He,~Y., Miocinovic,~P., Richards,~A., Woschnagg,~K., Koci,~B., and Zagorodnov,~V.: Temperature profile for glacial ice at the South Pole: implications for life in a~nearby subglacial lake, PNAS USA, 99(12), 7844–7847, \doi10.1073pnas.082238999, 2002. Rippin,~D M., Bamber,~J L., Siegert,~M J., Vaughan,~D G., and Corr,~H F J.: The role of ice thickness and bed properties on the dynamics of the enhanced flow tributaries of Bailey Ice Stream and Slessor Glacier, East Antarctica, Ann. Glaciol., 39, 366–372, 2004. Rippin,~D M., Bamber,~J L., Siegert,~M J., Vaughan,~D G., and Corr,~H F J.: Basal topography and ice flow in the Bailey/Slessor region of East Antarctica, J Geophys. Res.-Earth, 108(F1), 6009–6019, doi:10.1029/2003JF000039, 2003. Siegert,~M J.: Antarctic subglacial lakes, Earth-Sci. Rev., 50(1–2), 29–50, 2000. Siegert,~M J. and Bamber,~J L.: Subglacial water at the heads of Antarctic ice-stream tributaries, J Glaciol., 46(155), 702–703, 2000. Smith, B. E., Fricker, H. A., Joughin, I. R., and Tulaczyk, S.: An inventory of active subglacial lakes in Antarctica detected by ICESat (2003-2008), J. Glaciol., 55(192), 573–594, 2009. Stearns,~L A., Smith,~B E., and Hamilton,~G S.: Increased flow speed on a~large East Antarctic outlet glacier caused by subglacial floods, Nat. Geosci., 1, 827–831, \doi10.1038/ngeo356, 2008. Welch,~B C., Jacobel,~R W., and Arcone,~S.: First results from radar profiles collected along the US-ITASE traverse from Taylor Dome to South Pole (2006–2008), Ann. Glaciol., 50(51), 35–41, 2009. Welch,~B C. and Jacobel,~R W.: Analysis of deep-penetrating radar surveys of West Antarctica, US-ITASE 2001, Geophys. Res. Lett., 30(8), 1444, \doi10.1029/2003GL017210, 2003. Wingham,~D J., Siegert,~M J., Shepard,~A., and Muir,~A S.: Rapid discharge connects Antarctic subglacial lakes, Nature, 440, 1033–1036, \doi10.1038/nature04660, 2006.