Skip to main content Accessibility help

Weak bed control of the eastern shear margin of Thwaites Glacier, West Antarctica

  • Joseph A. MacGregor (a1), Ginny A. Catania (a1) (a2), Howard Conway (a3), Dustin M. Schroeder (a1), Ian Joughin (a4), Duncan A. Young (a1), Scott D. Kempf (a1) and Donald D. Blankenship (a1)...


Recent acceleration and thinning of Thwaites Glacier, West Antarctica, motivates investigation of the controls upon, and stability of, its present ice-flow pattern. Its eastern shear margin separates Thwaites Glacier from slower-flowing ice and the southern tributaries of Pine Island Glacier. Troughs in Thwaites Glacier’s bed topography bound nearly all of its tributaries, except along this eastern shear margin, which has no clear relationship with regional bed topography along most of its length. Here we use airborne ice-penetrating radar data from the Airborne Geophysical Survey of the Amundsen Sea Embayment, Antarctica (AGASEA) to investigate the nature of the bed across this margin. Radar data reveal slightly higher and rougher bed topography on the slower-flowing side of the margin, along with lower bed reflectivity. However, the change in bed reflectivity across the margin is partially explained by a change in bed roughness. From these observations, we infer that the position of the eastern shear margin is not strongly controlled by local bed topography or other bed properties. Given the potential for future increases in ice flux farther downstream, the eastern shear margin may be vulnerable to migration. However, there is no evidence that this margin is migrating presently, despite ongoing changes farther downstream.

  • View HTML
    • Send article to Kindle

      To send this article to your Kindle, first ensure 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 or variations. ‘’ emails are free but can only be sent to your device when it is connected to wi-fi. ‘’ 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.

      Weak bed control of the eastern shear margin of Thwaites Glacier, 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.

      Weak bed control of the eastern shear margin of Thwaites Glacier, 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.

      Weak bed control of the eastern shear margin of Thwaites Glacier, West Antarctica
      Available formats



Hide All
Anandakrishnan, S, Blankenship, DD, Alley, RB and Stoffa, PL (1998) Influence of subglacial geology on the position of a West Antarctic ice stream from seismic observations. Nature, 394(6688), 6265 (doi: 10.1038/27889)
Bell, RE and 6 others (1998) Influence of subglacial geology on the onset of a West Antarctic ice stream from aerogeophysical observations. Nature, 394(6688), 5862 (doi: 10.1038/27883)
Bingham, RG and Siegert, MJ (2009) Quantifying subglacial bed roughness in Antarctica: implications for ice-sheet dynamics and history. Quat. Sci. Rev., 28(3–4), 223236 (doi:10.1016/j.quascirev.2008.10.014)
Blankenship, DD and 9 others (2001) Geologic controls on the initiation of rapid basal motion for West Antarctic ice streams: a geophysical perspective including new airborne radar sounding and laser altimetry results. In The West Antarctic ice sheet: behavior and environment. (Antarctic Research Series 77) American Geophysical Union, Washington, DC, 105121
Boithias, L (1987) Radiowave propagation. McGraw-Hill, New York
Carter, SP, Blankenship, DD, Young, DA, Peters, ME, Holt, JW and Siegert, MJ (2009) Dynamic distributed drainage implied by the flow evolution of the 1996–1998 Adventure Trench subglacial lake discharge. Earth Planet. Sci. Lett., 283(1–4), 2437 (doi: 10.1016/j.epsl.2009.03.019)
Catania, GA, Conway, H, Gades, AM, Raymond, CF and Engelhardt, H (2003) Bed reflectivity beneath inactive ice streams in West Antarctica. Ann. Glaciol., 36, 287291
Catania, GA, Scambos, TA, Conway, H and Raymond, CF (2006) Sequential stagnation of Kamb Ice Stream, West Antarctica. Geophys. Res. Lett., 33(14), L14502 (doi: 10.1029/2006GL026430)
Catania, G, Hulbe, C, Conway, H, Scambos, TA and Raymond, CF (2012) Variability in the mass flux of the Ross ice streams, West Antarctica, over the last millennium. J. Glaciol., 58(210), 741752 (doi: 10.3189/2012JoG11J219)
Cuffey, KM and Paterson, WSB (2010) The physics of glaciers, 4th edn. Butterworth-Heinemann, Oxford
Echelmeyer, KA, Harrison, WD, Larsen, C and Mitchell, JE (1994) The role of the margins in the dynamics of an active ice stream. J. Glaciol., 40(136), 527538
Fretwell, P and 55 others (2013) Bedmap2: improved ice bed, surface and thickness datasets for Antarctica. Cryosphere, 7(1), 375393 (doi: 10.5194/tc-7-375-2013)
Grima, C, Kofman, W, Herique, A, Orosei, R and Seu, R (2012) Quantitative analysis of Mars surface radar reflectivity at 20 MHz. Icarus, 220(1), 8499 (doi: 10.1016/j.icarus.2012.04.017)
Gudmundsson, GH, Krug, J, Durand, G, Favier, L and Gagliardini, O (2012) The stability of grounding lines on retrograde slopes. Cryosphere, 6(6), 14971505 (doi: 10.5194/tc-6-1497-2012)
Harrison, WD, Echelmeyer, KA and Larsen, CF (1998) Measurement of temperature in a margin of Ice Stream B, Antarctica: implications for margin migration and lateral drag. J. Glaciol., 44(148), 615624
Holt, JW and 8 others (2006) New boundary conditions for the West Antarctic ice sheet: subglacial topography of the Thwaites and Smith glacier catchments. Geophys. Res. Lett., 33(9), L09502 (doi: 10.1029/2005GL025561)
Hubbard, B, Siegert, MJ and McCarroll, D (2000) Spectral roughness of glaciated bedrock geomorphic surfaces: implications for glacier sliding. J. Geophys. Res., 105(B9), 21 29521 303 (doi: 10.1029/2000JB900162)
Hulbe, C and Fahnestock, M (2007) Century-scale discharge stagnation and reactivation of the Ross ice streams, West Antarctica. J. Geophys. Res. , 112(F3), F03S27 (doi: 10.1029/2006JF000603)
Jacobs, SS, Jenkins, A, Giulivi, CF and Dutrieux, P (2011) Stronger ocean circulation and increased melting under Pine Island Glacier ice shelf. Nature Geosci., 4(8), 519523 (doi: 10.1038/ngeo1188)
Jacobson, HP and Raymond, CF (1998) Thermal effects on the location of ice stream margins. J. Geophys. Res., 103(B6), 12 11112 122 (doi: 10.1029/98JB00574)
Johnson, JS, Bentley, MJ and Gohl, K (2008) First exposure ages from the Amundsen Sea Embayment, West Antarctica: the Late Quaternary context for recent thinning of Pine Island, Smith and Pope Glaciers. Geology, 36(3), 223226 (doi: 10.1130/G24207A.1)
Joughin, I and Alley, RB (2011) Stability of the West Antarctic ice sheet in a warming world. Nature Geosci., 4(8), 506513 (doi: 10.1038/ngeo1194)
Joughin, I and 7 others (1999) Tributaries of West Antarctic ice streams revealed by RADARSAT interferometry. Science, 286(5438), 283286 (doi: 10.1126/science.286.5438.283)
Joughin, I, Tulaczyk, S, Bindschadler, RA and Price, S (2002) Changes in West Antarctic ice stream velocities: observation and analysis. J. Geophys. Res., 107(B11), 2289 (doi: 10.1029/2001JB001029)
Joughin, I and 6 others (2009) Basal conditions for Pine Island and Thwaites Glaciers, West Antarctica, determined using satellite and airborne data. J. Glaciol., 55(190), 245257 (doi: 10.3189/002214309788608705)
Karlsson, NB, Rippin, DM, Vaughan, DG and Corr, HFJ (2009) The internal layering of Pine Island Glacier, West Antarctica, from airborne radar-sounding data. Ann. Glaciol., 50(51), 141146
Lang, O, Rabus, BT and Dech, SW (2004) Velocity map of the Thwaites Glacier catchment, West Antarctica. J. Glaciol., 50(168), 4656 (doi: 10.3189/172756504781830268)
Li, X and 7 others (2010) Characterization of subglacial landscapes by a two-parameter roughness index. J. Glaciol., 56(199), 831836 (doi: 10.3189/002214310794457326)
MacGregor, JA, Winebrenner, DP, Conway, H, Matsuoka, K, Mayewski, PA and Clow, GD (2007) Modeling englacial radar attenuation at Siple Dome, West Antarctica, using ice chemistry and temperature data. J. Geophys. Res., 112(F3), F03008 (doi: 10.1029/2006JF000717)
MacGregor, J, Catania, GA, Markowski, MS and Andrews, AG (2012a) Widespread rifting and retreat of ice-shelf margins in the eastern Amundsen Sea Embayment between 1972 and 2011. J. Glaciol., 58(209), 458466 (doi: 10.3189/2012JoG11J262)
MacGregor, JA, Matsuoka, K, Waddington, ED, Winebrenner, DP and Pattyn, F (2012b) Spatial variation of englacial radar attenuation: modeling approach and application to the Vostok flowline. J. Geophys. Res., 117(F3), F03022 (doi: 10.1029/2011JF002327)
Matsuoka, K (2011) Pitfalls in radar diagnosis of ice-sheet bed conditions: lessons from englacial attenuation models. Geophys. Res. Lett., 38(5), L05505 (doi: 10.1029/2010GL046205)
Nayar, SK, Ikeuchi, K and Kanade, T (1991) Surface reflection: physical and geometrical perspectives. IEEE Trans. Pattern Anal. Machine Intell., 13(7), 611634 (doi: 10.1109/34.85654)
Ogilvy, JA (1991) Theory of wave scattering from random rough surfaces. Institute of Physics Publishing, Bristol
Oswald, GKA and Gogineni, SP (2008) Recovery of subglacial water extent from Greenland radar survey data. J. Glaciol., 54(184), 94106 (doi: 10.3189/002214308784409107)
Parizek, BR and 10 others (2013) Dynamic (in)stability of Thwaites Glacier, West Antarctica. J. Geophys. Res., 118 (doi: 10.1002/jgrf.20044)
Peters, ME, Blankenship, DD and Morse, DL (2005) Analysis techniques for coherent airborne radar sounding: application to West Antarctic ice streams. J. Geophys. Res., 110(B6), B06303 (doi: 10.1029/2004JB003222)
Peters, ME, Blankenship, DD, Carter, SP, Kempf, SD, Young, DA and Holt, JW (2007) Along-track focusing of airborne radar sounding data from West Antarctica for improving basal reflection analysis and layer detection. IEEE Trans. Geosci. Remote Sens., 45(9), 27252736 (doi: 10.1109/TGRS.2007.897416)
Pollard, D and DeConto, RM (2009) Modelling West Antarctic ice sheet growth and collapse through the past five million years. Nature, 458(7236), 329332 (doi: 10.1038/nature07809)
Price, SF, Bindschadler, RA, Hulbe, CL and Blankenship, DD (2002) Force balance along an inland tributary and onset to Ice Stream D, West Antarctica. J. Glaciol., 48(160), 2030 (doi: 10.3189/172756502781831539)
Pritchard, HD, Arthern, RJ, Vaughan, DG and Edwards, LA (2009) Extensive dynamic thinning on the margins of the Greenland and Antarctic ice sheets. Nature, 461(7266), 971975 (doi: 10. 1038/nature08471)
Pritchard, HD, Ligtenberg, SRM, Fricker, HA, Vaughan, DG, Van den Broeke, MR and Padman, L (2012) Antarctic ice-sheet loss driven by basal melting of ice shelves. Nature, 484(7395), 502505 (doi: 10.1038/nature10968)
Raymond, C (1996) Shear margins in glaciers and ice sheets. J. Glaciol., 42(140), 90102
Raymond, CF, Echelmeyer, KA, Whillans, IM and Doake, CSM (2001) Ice stream shear margins. In Alley, RB and Bindschadler, RA eds. The West Antarctic ice sheet: behavior and environment. (Antarctic Research Series 77) American Geophysical Union, Washington, DC, 137155
Raymond, CF, Catania, GA, Nereson, N and Van der Veen, CJ (2006) Bed radar reflectivity across the north margin of Whillans Ice Stream, West Antarctica, and implications for margin processes. J. Glaciol., 52(176), 310 (doi: 10.3189/172756506781828890)
Rignot, E (2008) Changes in West Antarctic ice stream dynamics observed with ALOS PALSAR data. Geophys. Res. Lett., 35(12), L12505 (doi: 10.1029/2008GL033365)
Rignot, E and 11 others (2004) Improved estimation of the mass balance of the glaciers draining into the Amundsen Sea sector of West Antarctica from the CECS/NASA 2002 campaign. Ann. Glaciol., 39, 231237 (doi: 10.3189/172756404781813916)
Rignot, E, Mouginot, J and Scheuchl, B (2011a) Ice flow of the Antarctic Ice Sheet. Science, 333(6048), 14271430 (doi: 10.1126/science.1208336)
Rignot, E, Mouginot, J and Scheuchl, B (2011b) Antarctic grounding line mapping from differential satellite radar interferometry. Geophys. Res. Lett., 38(10), L10504 (doi: 10.1029/2011GL047109)
Rippin, DM, Bamber, JL, Siegert, MJ, Vaughan, DG and Corr, HFJ (2006) Basal conditions beneath enhanced-flow tributaries of Slessor Glacier, East Antarctica. J. Glaciol., 52(179), 481490 (doi: 10.3189/172756506781828467)
Rippin, D, Vaughan, DG and Corr, HFJ (2011) The basal roughness of Pine Island Glacier, West Antarctica. J. Glaciol., 57(201), 6776 (doi: 10.3189/002214311795306574)
Ross, N and 9 others (2012) Steep reverse bed slope at the grounding line of the Weddell Sea sector in West Antarctica. Nature Geosci., 5(6), 393396 (doi: 10.1038/ngeo1468)
Scambos, TA, Bohlander, JA, Shuman, CA and Skvarca, P (2004) Glacier acceleration and thinning after ice shelf collapse in the Larsen B embayment, Antarctica. Geophys. Res. Lett., 31(18), L18402 (doi: 10.1029/2004GL020670)
Schoof, C (2007) Ice sheet grounding line dynamics: steady states, stability, and hysteresis. J. Geophys. Res., 112(F3), F03S28 (doi: 10.1029/2006JF000664)
Schroeder, DM, Blankenship, DD and Young, DA (in press) Evidence for a water system transition beneath Thwaites Glacier, West Antarctica. Proc. Natl Acad. Sci. USA (PNAS) (doi: 10.1073/pnas.1302828110)
Scott, JBT, Gudmundsson, GH, Smith, AM, Bingham, RG, Pritchard, HD and Vaughan, DG (2009) Increased rate of acceleration on Pine Island Glacier strongly coupled to changes in gravitational driving stress. Cryosphere, 3(1), 125131 (doi: 10.5194/tc-3-125-2009)
Shepard, MK, Campbell, BA, Bulmer, MH, Farr, TG, Gaddis, LR and Plaut, JJ (2001) The roughness of natural terrain: a planetary and remote sensing perspective. J. Geophys. Res., 106(E12), 32 77732 796 (doi: 10.1029/2000JE001429)
Shepherd, A, Wingham, D and Mansley, JA (2002) Inland thinning of the Amundsen Sea sector, West Antarctica. Geophys. Res. Lett., 29(10), 1364 (doi: 10.1029/2001GL014183)
Shepherd, A and 46 others (2012) A reconciled estimate of ice-sheet mass balance. Science, 338(6111), 11831189 (doi: 10.1168/science. 1227268)
Smith, AM and 6 others (2007) Rapid erosion, drumlin formation and changing hydrology beneath an Antarctic ice stream. Geology, 35(2), 127130 (doi: 10.1130/G23036A.1)
Smith, AM, Bentley, CR, Bingham, RG and Jordan, TA (2012) Rapid subglacial erosion beneath Pine Island Glacier, West Antarctica. Geophys. Res. Lett., 39(12), L12501 (doi: 10.1029/2012GL051651)
Stearns, LA, Jezek, KC and Van der Veen, CJ (2005) Decadal-scale variations in ice flow along Whillans Ice Stream and its tributaries, West Antarctica. J. Glaciol., 51(172), 147157 (doi: 10.3189/172756505781829610)
Studinger, M and 6 others (2001) Subglacial sediments: a regional geological template for ice flow in West Antarctica. Geophys. Res. Lett., 28(18), 34933496 (doi: 10.1029/2000GL011788)
Ulaby, FT, Moore, RK and Fung, AK (1982) Microwave remote sensing, active and passive. Vol. 2. Radar remote sensing and surface scattering and emission theory. Addison-Wesley, Reading, MA
Van der Veen, CJ (1999) Fundamentals of glacier dynamics. AA Balkema, Rotterdam
Vaughan, DG and 9 others (2006) New boundary conditions for the West Antarctic ice sheet: subglacial topography beneath Pine Island Glacier. Geophys. Res. Lett., 33(9), L09501 (doi: 10.1029/ 2005GL025588)
Winsborrow, MCM, Clark, CD and Stokes, CR (2010) What controls the location of ice streams? Earth-Sci. Rev., 103(1–2), 4559 (doi: 10.1016/j.earscirev.2010.07.003)
Young, DA and 11 others (2011) A dynamic early East Antarctic Ice Sheet suggested by ice-covered fjord landscapes. Nature, 474(7349), 7275 (doi: 10.1038/nature10114)
Recommend this journal

Email your librarian or administrator to recommend adding this journal to your organisation's collection.

Journal of Glaciology
  • ISSN: 0022-1430
  • EISSN: 1727-5652
  • URL: /core/journals/journal-of-glaciology
Please enter your name
Please enter a valid email address
Who would you like to send this to? *


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