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ITGC Publications

Alley, R. B., K. A. Emanuel, and F. Zhang. 2019. Advances in weather prediction. Science 363: 342-344.

Alley, R., K. Cuffey, and L. Zoet. 2019. Glacial erosion: Status and outlook. Annals of Glaciology 60(80): 1-13.

Bart, P. and S. Tulaczyk. 2020. A significant acceleration of ice volume discharge preceded a major retreat of a West Antarctic paleo–ice stream. Geology 48 (4): 313-317.

Bassis, J. N. and L. Ultee. 2019. A Thin Film Viscoplastic Theory for Calving Glaciers: Toward a Bound on the Calving Rate of Glaciers. Journal of Geophysical Research 124, 2036– 2055.

Bassis, J. N., B. Berg, A.J. Crawford and D. Benn. 2021. Transition to marine ice cliff instability controlled by ice thickness gradients and velocity. Science 372: 1342-1344.

Bushuk, M., Holland, D., Stanton, T., Stern, A., and Gray, C. 2019. Ice scallops: a laboratory investigation of the ice–water interface. Journal of Fluid Mechanics 873, 942-976.

Clyne, E. R., S. Anandakrishnan, A. Muto, R. B. Alley, and D. E. Voigt. 2020. Interpretation of topography and bed properties beneath Thwaites Glacier, West Antarctica using seismic reflection methods. Earth and Planetary Science Letters 550, 116543.

Crawford, A.J., D.I. Benn, J. Todd, et al. 2021. Marine ice-cliff instability modeling shows mixed-mode ice-cliff failure and yields calving rate parameterization. Nat Commun 12, 2701. 

De Rydt, J., Reese, R., Paolo, F. S., and Gudmundsson, G. H. 2021. Drivers of Pine Island Glacier speed-up between 1996 and 2016. The Cryosphere 15, 113–132.

dos Santos, T. D., M. Morlighem, and H. Seroussi. 2021. Assessment of numerical schemes for transient, finite-element ice flow models using ISSM v4.18. Geosci. Model Dev., 14: 2545–2573.

Gudmundsson, G.H., F.S. Paolo, S. Adusumilli, and H.A. Fricker. 2019. Instantaneous Antarctic ice‐sheet mass loss driven by thinning ice shelves. Geophysical Research Letters 46, 13,903–13,909.

Hoffman, A. O., K. Christianson, D. Shapero, B. E. Smith, and I. Joughin. 2020. Brief communication: Heterogenous thinning and subglacial lake activity on Thwaites Glacier, West Antarctica. The Cryosphere 14, 4603–4609.

Hogan, K. A., R. D. Larter, A. G. C. Graham, R. Arthern, J. D. Kirkham, R. Totten Minzoni, T. A. Jordan, R. Clark, V. Fitzgerald, A. K. Wåhlin, J. B. Anderson, C.-D. Hillenbrand, F. O. Nitsche, L. Simkins, J. A. Smith, K. Gohl, J. E. Arndt, J. Hong, and J. Wellner. 2020. Revealing the former bed of Thwaites Glacier using sea-floor bathymetry: implications for warm-water routing and bed controls on ice flow and buttressing. The Cryosphere 14, 2883–2908.

Holland, D. M., K. W. Nicholls, and A. Basinski. 2020. The Southern Ocean and its interaction with the Antarctic Ice Sheet. Science 367.6484, 1326-1330.  

Holschuh, N., K. Christianson, J. Paden, R.B. Alley, and S. Anandakrishnan. 2020. Linking postglacial landscapes to glacier dynamics using swath radar at Thwaites Glacier, Antarctica. Geology 48 (3): 268–272.

Jordan, T. A., D. Porter, K. Tinto, R. Millan, A. Muto, K. Hogan, R. D. Larter, A. G. C. Graham, and J. D. Pade. 2020. New gravity-derived bathymetry for the Thwaites, Crosson, and Dotson ice shelves revealing two ice shelf populations. The Cryosphere 14, 2869–2882.

Koellner, S., B. R. Parizek, R. B. Alley, A. Muto, and N. Holschuh. 2019. The impact of spatially-variable basal properties on outlet glacier flow. Earth and Planetary Science Letters 515: 200-208.

Malczyk, G., N. Gourmelen, D. Goldberg, J. Wuite, and T. Nagler. 2020. Repeat Subglacial Lake Drainage and Filling Beneath Thwaites Glacier. Geophysical Research Letters, 47:23, e2020GL089658.

Morlighem, M., Rignot, E., Binder, T. et al. 2020. Deep glacial troughs and stabilizing ridges unveiled beneath the margins of the Antarctic ice sheet. Nat. Geosci. 13, 132–137.

Muto, A., R. Alley, Parizek, B. and Anandakrishnan, S. 2019. Bed-type variability and till (dis)continuity beneath Thwaites Glacier, West Antarctica. Annals of Glaciology 1-9.

Muto, A., S. Anandakrishnan, R. Alley, H. Horgan, B. Parizek, S. Koellner, K. Christianson, and N. Holschuh. 2019. Relating bed character and subglacial morphology using seismic data from Thwaites Glacier, West Antarctica. Earth and Planetary Science Letters 507, 199-206.

Post, E., R. B. Alley, T. R. Christensen, M. Macias-Fauria, B. C. Forbes, M. N. Gooseff, A Iler, J. T. Kerby, K. L. Laidre, M. E. Mann, J. Olofsson, J. C. Stroeve, F. Ulmer, R. A. Virginia, and M. Wang. 2019. The polar regions in a 2°C warmer world. Science Advances 5:12.

Räss, L., Licul, A., Herman, F., Podladchikov, Y. Y., and Suckale, J. 2020. Modelling thermomechanical ice deformation using an implicit pseudo-transient method (FastICE v1.0) based on graphical processing units (GPUs). Geosci. Model Dev., 13, 955–976.

Riverman, K., S. Anandakrishnan, R. Alley, N. Holschuh, C. Dow, A. Muto, B. Parizek, K. Christianson, and L. Peters. 2019. Wet subglacial bedforms of the NE Greenland Ice Stream shear margins. Annals of Glaciology 60(80), 91-99.

Young, T. J., D. M. Schroeder, T. M. Jordan, P. Christoffersen, S. M. Tulaczyk, R. Culberg, and N. L. Bienert. 2021. Inferring ice fabric from birefringence loss in airborne radargrams: Application to the eastern shear margin of Thwaites Glacier, West Antarctica. JGR Earth Surface. 

Zoet, L. K., M. J. Ikari, R. B. Alley, C. Marone, S. Anandakrishnan, B. M. Carpenter, et al. 2020. Application of constitutive friction laws to glacier seismicity. Geophysical Research Letters, 47, e2020GL088964.

Related Publications

Alley, R.B., and I.M. Whillans. 1991. Changes in the West Antarctic ice sheet. Science 254: 959-963.

Alley, R.B., S. Anandakrishnan, K. Christianson, H.J. Horgan, A. Muto, B.R. Parizek, D. Pollard, and R.T. Walker. 2015. Oceanic forcing of ice-sheet retreat: West Antarctica and more. Annual Reviews of Earth and Planetary Sciences 43: 207-231.

Alley, R.B., W. Li, B.R. Parizek, and F. Zhang. 2019. Evaluation of ice-stream model sensitivities for parameter estimation. Earth and Planetary Science Letters 516: 49-55.

Bassis, J.N., and C.C. Walker. 2012. Upper and lower limits on the stability of calving glaciers from the yield strength envelope of ice. Proceedings of the Royal Society of London, Series A 468: 913-931.

 

Christianson, K., M. Bushuk, P. Dutrieux, B.R. Parizek, I.R. Joughin, R.B. Alley, D.E. Shean, E.P. Abrahamsen, S. Anandakrishnan, K.J. Heywood, T.‐W. Kim, S.H. Lee, K. Nicholls, T. Stanton, M. Truffer, B.G.M. Webber, A. Jenkins, S. Jacobs, R. Bindschadler, and D.M. Holland. 2016. Sensitivity of Pine Island Glacier to observed ocean forcing. Geophysical Research Letters 43(2): 10817-10825.

Christianson, K., R.W. Jacobel, H.J. Horgan, R.B. Alley, S. Anandakrishnan, D.M. Holland, and K.J. DallaSanta. 2016. Basal conditions at the grounding zone of Whillans Ice Stream, West Antarctica, from ice-penetrating radar. Journal of Geophysical Research Earth Surface 121(11): 1954-1983.

Christianson, K., R.W. Jacobel, H.J. Horgan, S. Anandakrishnan, and R.B. Alley. 2012. Subglacial Lake Whillans – Ice-penetrating radar and GPS observations of a shallow active reservoir beneath a West Antarctic ice stream. Earth and Planetary Science Letters 331-332: 237-245.

De Rydt, J., and G.H. Gudmundsson. 2016. Coupled ice shelf‐ocean modeling and complex grounding line retreat from a seabed ridge. Journal of Geophysical Research: Earth Surface 121(5): 865-880.

DeConto, R.M., and D. Pollard. 2016. Contribution of Antarctica to past and future sea-level rise. Nature 531: 591-597.

Favier, L., G. Durand, S.L. Cornford, G.H. Gudmundsson, O. Gagliardini, F. Gillet-Chaulet, T. Zwinger, A.J. Payne, and A.M. Le Brocq. 2014. Retreat of Pine Island Glacier controlled by marine ice-sheet instability. Nature Climate Change 4(2): 117-121.

Gohl, K., G. Uenzelmann-Neben, R.D. Larter, C.-D. Hillenbrand, K. Hochmuth, T. Kalberg, E. Weigelt, B. Davy, G. Kuhn, and F.O. Nitsche. 2013. Seismic stratigraphic record of the Amundsen Sea Embayment shelf from pre-glacial to recent times: Evidence for a dynamic West Antarctic ice sheet. Marine Geology 344: 115-131.

Goldberg, D.N., K. Snow, P. Holland, J.R. Jordan, J.M. Campin, P. Heimbach, R. Arthern, and A. Jenkins. 2018. Representing grounding line migration in synchronous coupling between a marine ice sheet model and a z-coordinate ocean model. Ocean Modelling 125: 45-60.

Goldberg, D.N., P. Heimbach, I. Joughin, and B. Smith. 2015. Committed retreat of Smith, Pope, and Kohler Glaciers over the next 30 years inferred by transient model calibration. The Cryosphere 9: 2429-2446.

Graham, A.G.C., F.O. Nitsche, R.D. Larter, and K. Gohl. 2016. Submarine landform assemblage produced beneath the Dotson-Getz palaeo-ice stream, West Antarctica. Geological Society, London, Memoirs 46: 345-348.

Graham, A.G.C., M. Jakobsson, F.O. Nitsche, R.D. Larter, J.B. Anderson, C.-D. Hillenbrand, K. Gohl, J.P. Klages, J.A. Smith, and A. Jenkins. 2016. Submarine glacial-landform distribution across the West Antarctic margin, from grounding line to slope: The Pine Island-Thwaites ice-stream system. Geological Society, London, Memoirs 46: 493-500.

Graham, A.G.C., P. Dutrieux, D.G. Vaughan, F.O. Nitsche, R. Gyllencreutz, S.L. Greenwood, R.D. Larter, and A. Jenkins. 2013. Seabed corrugations beneath an Antarctic ice shelf revealed by autonomous underwater vehicle survey: Origin and implications for the history of Pine Island Glacier. Journal of Geophysical Research 118(3): 1356-1366.

Graham, A.G.C., R.D. Larter, K. Gohl, C.-D. Hillenbrand, J.A. Smith, and G. Kuhn. 2009. Bedform signature of a West Antarctic palaeo-ice stream reveals a multi-temporal record of flow and substrate control. Quaternary Science Reviews 28: 2774-2793.

Graham, A.G.C., R.D. Larter, K. Gohl, J.A. Dowdeswell, C.‐D. Hillenbrand, J.A. Smith, J. Evans, G. Kuhn, and T. Deen. 2010. Flow and retreat of the Late Quaternary Pine Island‐Thwaites palaeo‐ice stream, West Antarctica. Journal of Geophysical Research 115: F03025.

Heywood, K.J., L.C. Biddle, L. Boehme, P. Dutrieux, M. Fedak, A. Jenkins, R.W. Jones, J. Kaiser, H. Mallett, A.C. Naveira Garabato, I.A. Renfrew, D.P. Stevens, and B.G.M. Webber. 2016. Between the devil and the deep blue sea: The role of the Amundsen Sea continental shelf in exchanges between ocean and ice shelves. Oceanography 29(4): 118-129.

Hillenbrand, C.-D., G. Kuhn, J.A. Smith, K. Gohl, A.G.C. Graham, R.D. Larter, J.P. Klages, R. Downey, S.G. Moreton, M. Forwick, and D.G. Vaughan. 2013. Grounding-line retreat of the West Antarctic Ice Sheet from inner Pine Island Bay. Geology 41(1): 35-38.

Hillenbrand, C.-D., J.A. Smith, D.A. Hodell, M. Greaves, C.R. Poole, S. Kender, M. Williams, T.J. Andersen, P.E. Jernas, H. Elderfield, J.P. Klages, S.J. Roberts, K. Gohl, R.D. Larter, and G. Kuhn. 2017. West Antarctic Ice Sheet retreat driven by Holocene warm water incursions. Nature 547: 43-48.

Holschuh, N., B.R. Parizek, R.B. Alley, and S. Anandakrishnan. 2017. Decoding ice sheet behavior using englacial layer slopes. Geophysical Research Letters 44(11): 5561-5570.

Jacobs, S., C. Giulivi, P. Dutrieux, E. Rignot, F. Nitsche, and J. Mouginot. 2013. Getz ice shelf melting response to changes in ocean forcing. Journal of Geophysical Research: Oceans 118(9): 1-17.

Jenkins, A., P. Dutrieux, S. Jacobs, E.J. Steig, G.H. Gudmundsson, J. Smith, and K.J. Heywood. 2016. Decadal ocean forcing and Antarctic Ice Sheet response: lessons from the Amundsen Sea. Oceanography 29(4): 106-117.

Johnson, J.S., J.A. Smith, J.M. Schaefer, N.E. Young, B.M. Goehring, C.-D. Hillenbrand, J.L. Lamp, R.C. Finkel, and K. Gohl. 2017. The last glaciation of Bear Peninsula, central Amundsen Sea Embayment of Antarctica: Constraints on timing and duration revealed by in situ cosmogenic 14C and 10Be dating. Quaternary Science Reviews 178: 77-88.

Johnson, J.S., J.P. O'Donnell, and E.R. Thomas. 2018. In situ measurements of snow accumulation in the Amundsen Sea Embayment during 2016. Antarctic Science 30(3): 197-203.

Johnson, J.S., M.J. Bentley, J.A. Smith, R.C. Finkel, D.H. Rood, K. Gohl, G. Balco, R.D. Larter, and J.M. Schaefer. 2014. Rapid thinning of Pine Island Glacier in the early Holocene. Science 343(6174): 999-1001.

Joughin, I., B.E. Smith, and B. Medley. 2014. Marine ice sheet collapse potentially under way for the Thwaites Glacier Basin, West Antarctica. Science 344: 735-738.

Joughin, I., D.E. Shean, B.E. Smith, and P. Dutrieux. 2016. Grounding line variability and subglacial lake drainage on Pine Island Glacier, Antarctica. Geophysical Research Letters 43(17): 9093-9102.

Khazendar, A., E. Rignot, D.M. Schroeder, H. Seroussi, M.P. Schodlok, B. Scheuchl, J. Mouginot, T.C. Sutterley, and I. Velicogna. 2016. Rapid submarine ice melting in the grounding zones of ice shelves in West Antarctica. Nature Communications 7: 13243.

Kimura, S., A. Jenkins, P. Dutrieux, A. Forryan, A.C. Naveira Garabato, and Y. Firing. 2016. Ocean mixing beneath Pine Island Glacier Ice Shelf. Journal of Geophysical Research: Oceans 121(12): 8496-8510.

Kirkham, J.D., K.A. Hogan, R.D. Larter, N.S. Arnold, F.O. Nitsche, N.R. Golledge, and J.A. Dowdeswell. 2019. Past water flow beneath Pine Island and Thwaites glaciers, West Antarctica. The Cryosphere 13: 1959–1981. 

Klages, J.P., G. Kuhn, A.G.C. Graham, C.-D. Hillenbrand, J.A. Smith, F.O. Nitsche, R.D. Larter, and K. Gohl. 2015. Palaeo-ice stream pathways and retreat style in the easternmost Amundsen Sea Embayment, West Antarctica, revealed by combined multibeam bathymetric and seismic data. Geomorphology 245: 207-222.

Koellner, S., B.R. Parizek, R.B. Alley, A. Muto and N. Holschuh. 2019. The impact of spatially-variable basal properties on outlet glacier flow. Earth and Planetary Science Letters 515: 200-208.

Larter, R.D., A.G.C. Graham, K. Gohl, G. Kuhn, C.-D. Hillenbrand, J.A. Smith, T.J. Deen, R.A. Livermore, and H.-W. Schenke. 2009. Subglacial bedforms reveal complex basal regime in a zone of paleo–ice stream convergence, Amundsen Sea embayment, West Antarctica. Geology 37(5): 411-414.

Larter, R.D., J.B. Anderson, A.G.C. Graham, K. Gohl, C.-D. Hillenbrand, M. Jakobsson, J.S. Johnson, G. Kuhn, F.O. Nitsche, J.A. Smith, A.E. Witus, M.J. Bentley, J.A. Dowdeswell, W. Ehrmann, J.P. Klages, J. Lindow, C.Ó. Cofaigh, and C. Spiegel. 2014. Reconstruction of changes in the Amundsen Sea and Bellingshausen Sea sector of the West Antarctic Ice Sheet since the Last Glacial Maximum.Quaternary Science Reviews 100: 55-86.

Lhermitte, S., S. Sun, C. Shuman, B. Wouters, F. Pattyn, J. Wuite, E. Berthier, and T. Nagler. 2020. Damage accelerates ice shelf instability and mass loss in Amundsen Sea Embayment. Proceedings of the National Academy of Sciences, 201912890.

Millan R., E. Rignot, V. Bernier, M. Morlighem, and P. Dutrieux. 2017. Bathymetry of the Amundsen Sea Embayment sector of West Antarctica from Operation IceBridge gravity and other data. Geophysical Research Letters 44(3): 1360-1368.

Mouginot, J., E. Rignot, and B. Scheuchl. 2014. Sustained increase in ice discharge from the Amundsen Sea Embayment, West Antarctica, from 1973 to 2013. Geophysical Research Letters 41: 1576-1584.

Muto, A., S. Anandakrishnan, R.B. Alley, H.J. Horgan, B.R. Parizek, S. Koellner, K. Christianson, and N. Holschuh. 2019. Relating bed character and subglacial morphology using seismic data from Thwaites Glacier, West Antarctica. Earth and Planetary Science Letters 507: 199-206.

Naveira Garabato, A.C., A. Forryan, P. Dutrieux, L. Brannigan, L.C. Biddle, K.J. Heywood, A. Jenkins, Y.L. Firing, and S. Kimura. 2017. Vigorous lateral export of the meltwater outflow from beneath an Antarctic ice shelf. Nature 542(7640): 219-22.

Nitsche, F.O., K. Gohl, R.D. Larter, C.-D. Hillenbrand, G. Kuhn, J.A. Smith, S. Jacob, J.B. Anderson, and M. Jakobsson. 2013. Paleo ice flow and subglacial meltwater dynamics in Pine Island Bay, West Antarctica. The Cryosphere 7: 249-262.

Nitsche, F.O., R.D. Larter, K. Gohl, A.G.C. Graham, and G. Kuhn. 2016. Bedrock channels in Pine Island Bay, West Antarctica.Geological Society, London, Memoirs 46: 217-218.

Parizek, B.R., K. Christianson, R.B. Alley, D. Voytenko, I. Vaňková, T.H. Dixon, R.T. Walker, and D.M. Holland. 2019. Ice-cliff failure via retrogressive slumping. Geology 47(5): 449-452.

Parizek, B.R., K. Christianson, S. Anandakrishnan, R.B. Alley, R.T. Walker, R.A. Edwards, D.S. Wolfe, G.T. Bertini, S.K. Rinehart, R.A. Bindschadler, and S.M.J. Nowicki. 2013. Dynamic (in)stability of Thwaites Glacier, West Antarctica. Journal of Geophysical Research-Earth Surface 118(2): 638-655.

Rignot, E., J. Mouginot, M. Morlighem, H. Seroussi, and B. Scheuchl. 2014. Widespread, rapid grounding line retreat of Pine Island, Thwaites, Smith, and Kohler glaciers, West Antarctica, from 1992 to 2011. Geophysical Research Letters 41: 3502-3509.

Scambos, T.A., R.E. Bell, R.B. Alley, S. Anandakrishnan, D.H. Bromwich, K. Brunt, K. Christianson, T. Creyts, S.B. Das, R. DeConto, P. Dutrieux, H.A. Fricker, D. Holland, J. MacGregor, B. Medley, J.P. Nicolas, D. Pollard, M.R. Siegfried, A.M., Smith, E.J. Steig, L.D. Trusel, D.G. Vaughan, and P.L. Yager. 2017. How much, how fast?: A science review and outlook for research on the instability of Antarctica's Thwaites Glacier in the 21st century. Global and Planetary Change 153: 16-34.

Seroussi, H., M. Morlighem, E. Rignot, J. Mouginot, E. Larour, M. Schodlok, and A. Khazendar. 2014. Sensitivity of the dynamics of Pine Island Glacier, West Antarctica, to climate forcing for the next 50 years. The Cryosphere 8: 1699-1710.

Seroussi, H., Y. Nakayama, E. Larour, D. Menemenlis, M. Morlighem, E. Rignot, and A. Khazendar. 2017. Continued retreat of Thwaites Glacier, West Antarctica, controlled by bed topography and ocean circulation. Geophysical Research Letters 44(12): 6191-6199.

Smith, J.A., C.-D. Hillenbrand, G. Kuhn, J.P. Klages, A.G.C. Graham, R.D. Larter, W. Ehrmann, S.G. Moreton, S. Wiers, and T. Frederichs. 2014. New constraints on the timing of West Antarctic Ice Sheet retreat in the eastern Amundsen Sea since the Last Glacial Maximum. Global and Planetary Change 122: 224-237.

Smith, J.A., C.-D. Hillenbrand, G. Kuhn, R.D. Larter, A.G.C. Graham, W. Ehrmann, S.G. Moreton, and M. Forwick. 2011. Deglacial history of the West Antarctic Ice Sheet in the western Amundsen Sea Embayment. Quaternary Science Reviews 30: 488-505.

Smith, J.A., T.J. Andersen, M. Shortt, A.M. Gaffney, M. Truffer, T.P. Stanton, R. Bindschadler, P. Dutrieux, A. Jenkins, C.-D. Hillenbrand, W. Ehrmann, H.F.J. Corr, N. Farley, S. Crowhurst, and D.G. Vaughan. 2016. Sub-ice-shelf sediments record 20th-century retreat of Pine Island Glacier. Nature 541(7635): 77-80.

Thurnherr, A.M., S.S. Jacobs, P. Dutrieux, and C.F. Giulivi. 2014. Export and circulation of ice cavity water in Pine Island Bay, West Antarctica. Journal of Geophysical Research: Oceans 119(3): 1754-1764.

Turner, J., A. Orr, G.H. Gudmundsson, A. Jenkins, R.G. Bingham, C.‐D. Hillenbrand, and T.J. Bracegirdle. 2017. Atmosphere‐ocean‐ice interactions in the Amundsen Sea Embayment, West Antarctica. Reviews of Geophysics 55(1): 235-276.

Vaughan, D.G., H.F.J. Corr, R.A. Bindschadler, P. Dutrieux, G.H. Gudmundsson, A. Jenkins, T. Newman, P. Vornberger, and D.J. Wingham. 2012. Subglacial melt channels and fracture in the floating part of Pine Island Glacier, Antarctica. Journal of Geophysical Research 117(F3), 1110.

Webber, B.G.M., K.J. Heywood, D.P. Stevens, P. Dutrieux, E.P. Abrahamsen, A. Jenkins, S.S. Jacobs, H.K. Ha, S.H. Lee, and T.W. Kim. 2017. Mechanisms driving variability in the ocean forcing of Pine Island Glacier. Nature Communications 8:14507.

Welch, B.C., and R.W. Jacobel. 2003. Analysis of deep-penetrating radar surveys of West Antartica, USITASE 2001. Geophysical Research Letters 30(8): 1444.

Welch, B.C., R.W. Jacobel and S.A. Arcone. 2009. First results from radar profiles collected along the US-ITASE traverse from Taylor Dome to South Pole (2006-2008). Annals of Glaciology 50(51): 35-41.

Wise, M.G., J.A. Dowdeswell, M. Jakobsson, and R.D. Larter. 2017. Evidence of marine ice-cliff instability in Pine Island Bay from iceberg-keel plough marks. Nature 550: 506-510.