Dr. Ryan T. Walker

Dr. Ryan T. Walker

  • RESEARCH SCIENTIST
  • 301.614.6933
  • NASA/GSFC
  • Mail Code: 615
  • Greenbelt , MD 20771
  • Employer: UNIVERSITY OF MARYLAND
  • Brief Bio

    Ryan joined the Cryospheric Sciences Laboratory in August 2012, following four years as a researcher with Penn State's Ice and Climate group. While at Penn State, he participated in the NASA-led SeaRISE community modeling effort to determine upper bounds for ice sheet contribution to sea level in a warming climate.

    Research Interests

    Ice sheet modeling; flow of ice streams and ice shelves; interaction between ice shelves and ocean; ice sheet contribution to sea level.


    Current Projects

    ISMIP6

    The Ice Sheet Model Intercomparison Project for CMIP6 (the Coupled Model Intercomparison Project), a targeted activity of the Climate and Cryosphere project of World Climate Research Programme. (http://www.climate-cryosphere.org/activities/targeted/ismip6)

    Observations of Nansen Ice Shelf, Antarctica

    Installation of GPS and tiltmeters to investigate the response of the ice shelf to ocean tides during austral summer 2015-2016, in collaboration with the Korea Polar Research Institute.

    Modeling the Amundsen Sea Embayment, Antarctica

    Collaborative NSF-sponsored project to simulate the range of probably outcomes as this vulnerable sector of the West Antarctic Ice Sheet retreats due to ocean-driven melting and other climate forcing.

    Education


    Ph.D., Atmosphere Ocean Science, New York University (2006)
    • Thesis: A two-dimensional coupled model for ice shelf-ocean interaction
    • Advisor: David M. Holland
    M.S., Mathematics, New York University (2002)
    B.S., Mathematics, Haverford College (1998)

    Selected Publications

    Refereed

    Walker, R. T., M. A. Werder, C. F. Dow, and S. M. Nowicki. 2017. "Determining Ice-Sheet Uplift Surrounding Subglacial Lakes with a Viscous Plate Model." Frontiers in Earth Science, 5: [10.3389/feart.2017.00103]

    Walker, R. T., B. R. Parizek, R. B. Alley, and S. M. Nowicki. 2016. "A Viscoelastic Model of Ice Stream Flow with Application to Stick-Slip Motion." Front. Earth Sci., 4: [10.3389/feart.2016.00002]

    Bartholomaus, T. C., L. A. Stearns, D. A. Sutherland, et al. E. L. Shroyer, J. D. Nash, R. T. Walker, G. Catania, D. Felikson, D. Carroll, M. J. Fried, B. P. Noël, and M. R. Van Den Broeke. 2016. "Contrasts in the response of adjacent fjords and glaciers to ice-sheet surface melt in West Greenland." Ann. Glaciol., 57 (73): 25-38 [10.1017/aog.2016.19]

    Dow, C. F., M. A. Werder, S. Nowicki, and R. T. Walker. 2016. "Modeling Antarctic subglacial lake filling and drainage cycles." The Cryosphere, 10 (4): 1381-1393 [10.5194/tc-10-1381-2016]

    Alley, R. B., S. Anandakrishnan, K. Christianson, et al. 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 Review of Earth and Planetary Sciences, 43: 207 -231 [10.1146/annurev-earth-060614-105344]

    Voytenko, D., A. Stern, D. M. Holland, et al. T. H. Dixon, K. Christianson, and R. T. Walker. 2015. "Tidally driven ice speed variation at Helheim Glacier, Greenland, observed with terrestrial radar interferometry." Journal of Glaciology, 61 (226): 301-308 [10.3189/2015jog14j173]

    Walker, R. T., B. R. Parizek, R. B. Alley, K. M. Brunt, and S. Anandakrishnan. 2014. "Ice-shelf flexure and tidal forcing of Bindschadler Ice Stream, West Antarctica." Earth and Planetary Science Letters, 395: 184-193 [10.1016/j.epsl.2014.03.049]

    Walker, R., D. M. Holland, B. R. Parizek, et al. R. B. Alley, S. Nowicki, and A. Jenkins. 2013. "Efficient Flowline Simulations of Ice Shelf–Ocean Interactions: Sensitivity Studies with a Fully Coupled Model." Journal of Physical Oceanography, 43 (10): 2200–2210 [10.1175/JPO-D-13-037.1]

    Bindschadler, R., S. Nowicki, A. Abe-Ouchi, et al. A. Ashwanden, H. Choi, J. Fastook, G. Granzow, R. Greve, G. Gutowski, U. Herzfeld, C. Jackson, J. Johnson, C. Khroulev, A. Levermann, W. H. Lipscomb, M. A. Martin, M. Morlighem, B. R. Parizek, D. Pollard, S. F. Price, D. Ren, F. Saito, T. Sato, H. Seddik, H. Seroussi, K. Takahashi, R. Walker, and W. L. Wang. 2013. "Ice-sheet model sensitivities to environmental forcing and their use in projecting future sea level (the SeaRISE project)." Journal of Glaciology, 59 (214): 195-224 [10.3189/2013JoG12J125]

    Parizek, B., K. Christianson, S. Anandakrishnan, et al. R. Alley, R. Walker, R. Edwards, D. Wolfe, G. Bertini, S. Rinehart, R. Bindschadler, and S. Nowicki. 2013. "Dynamic (in)stability of Thwaites Glacier, West Antarctica." J. Geophys. Res. Earth Surf., 118 (2): 638-655 [10.1002/jgrf.20044]

    Nowicki, S., A. Abe-Ouchi, A. Aschwanden, et al. E. Bueler, H. Choi, J. Fastook, G. Granzow, R. Greve, G. Gutowski, U. Herzfeld, C. Jackson, J. Johnson, C. Khroulev, E. Larour, A. Levermann, W. H. Lipscomb, M. A. Martin, M. Morlighem, B. R. Parizek, D. Pollard, S. F. Price, D. Ren, E. Rignot, F. Saito, T. Sato, H. Seddik, H. Seroussi, K. Takahashi, R. Walker, and W. Wang. 2013. "Insights into spatial sensitivities of ice mass response to environmental change from the SeaRISE ice sheet modeling project II: Greenland." J. Geophys. Res. Earth Surf., 118 (2): 1025-1044 [Full Text (Link)] [10.1002/jgrf.20076]

    Nowicki, S., R. A. Bindschadler, A. Abe-Ouchi, et al. A. Aschwanden, E. Bueler, H. Choi, J. Fastook, G. Granzow, R. Greve, G. Gutowski, U. Herzfeld, C. Jackson, J. Johnson, C. Khroulev, E. Larour, A. Levermann, W. H. Lipscomb, M. A. Martin, M. Morlighem, B. R. Parizek, D. Pollard, S. F. Price, D. Ren, E. Rignot, F. Saito, T. Sato, H. Seddik, H. Seroussi, K. Takahashi, R. Walker, and W. L. Wang. 2013. "Insights into spatial sensitivities of ice mass response to environmental change from the SeaRISE ice sheet modeling project I: Antarctica." Journal Of Geophysical Research: Earth Surface, 118 (2): 1002-1024 [10.1002/jgrf.20081]

    Walker, R. T., B. Parizek, R. Alley, et al. S. Anandakrishnan, K. Riverman, and K. Christianson. 2013. "Ice-shelf tidal flexure and subglacial pressure variations." Earth and Planetary Science Letters, 361: 422-428 [10.1016/j.epsl.2012.11.008]

    Brief Bio

    Ryan joined the Cryospheric Sciences Laboratory in August 2012, following four years as a researcher with Penn State's Ice and Climate group. While at Penn State, he participated in the NASA-led SeaRISE community modeling effort to determine upper bounds for ice sheet contribution to sea level in a warming climate.

    Selected Publications

    Refereed

    Walker, R. T., M. A. Werder, C. F. Dow, and S. M. Nowicki. 2017. "Determining Ice-Sheet Uplift Surrounding Subglacial Lakes with a Viscous Plate Model." Frontiers in Earth Science 5 [10.3389/feart.2017.00103]

    Walker, R. T., B. R. Parizek, R. B. Alley, and S. M. Nowicki. 2016. "A Viscoelastic Model of Ice Stream Flow with Application to Stick-Slip Motion." Front. Earth Sci. 4 [10.3389/feart.2016.00002]

    Bartholomaus, T. C., L. A. Stearns, D. A. Sutherland, et al. E. L. Shroyer, J. D. Nash, R. T. Walker, G. Catania, D. Felikson, D. Carroll, M. J. Fried, B. P. Noël, and M. R. Van Den Broeke. 2016. "Contrasts in the response of adjacent fjords and glaciers to ice-sheet surface melt in West Greenland." Ann. Glaciol. 57 (73): 25-38 [10.1017/aog.2016.19]

    Dow, C. F., M. A. Werder, S. Nowicki, and R. T. Walker. 2016. "Modeling Antarctic subglacial lake filling and drainage cycles." The Cryosphere 10 (4): 1381-1393 [10.5194/tc-10-1381-2016]

    Alley, R. B., S. Anandakrishnan, K. Christianson, et al. 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 Review of Earth and Planetary Sciences 43 207 -231 [10.1146/annurev-earth-060614-105344]

    Voytenko, D., A. Stern, D. M. Holland, et al. T. H. Dixon, K. Christianson, and R. T. Walker. 2015. "Tidally driven ice speed variation at Helheim Glacier, Greenland, observed with terrestrial radar interferometry." Journal of Glaciology 61 (226): 301-308 [10.3189/2015jog14j173]

    Walker, R. T., B. R. Parizek, R. B. Alley, K. M. Brunt, and S. Anandakrishnan. 2014. "Ice-shelf flexure and tidal forcing of Bindschadler Ice Stream, West Antarctica." Earth and Planetary Science Letters 395 184-193 [10.1016/j.epsl.2014.03.049]

    Walker, R., D. M. Holland, B. R. Parizek, et al. R. B. Alley, S. Nowicki, and A. Jenkins. 2013. "Efficient Flowline Simulations of Ice Shelf–Ocean Interactions: Sensitivity Studies with a Fully Coupled Model." Journal of Physical Oceanography 43 (10): 2200–2210 [10.1175/JPO-D-13-037.1]

    Bindschadler, R., S. Nowicki, A. Abe-Ouchi, et al. A. Ashwanden, H. Choi, J. Fastook, G. Granzow, R. Greve, G. Gutowski, U. Herzfeld, C. Jackson, J. Johnson, C. Khroulev, A. Levermann, W. H. Lipscomb, M. A. Martin, M. Morlighem, B. R. Parizek, D. Pollard, S. F. Price, D. Ren, F. Saito, T. Sato, H. Seddik, H. Seroussi, K. Takahashi, R. Walker, and W. L. Wang. 2013. "Ice-sheet model sensitivities to environmental forcing and their use in projecting future sea level (the SeaRISE project)." Journal of Glaciology 59 (214): 195-224 [10.3189/2013JoG12J125]

    Parizek, B., K. Christianson, S. Anandakrishnan, et al. R. Alley, R. Walker, R. Edwards, D. Wolfe, G. Bertini, S. Rinehart, R. Bindschadler, and S. Nowicki. 2013. "Dynamic (in)stability of Thwaites Glacier, West Antarctica." J. Geophys. Res. Earth Surf. 118 (2): 638-655 [10.1002/jgrf.20044]

    Nowicki, S., A. Abe-Ouchi, A. Aschwanden, et al. E. Bueler, H. Choi, J. Fastook, G. Granzow, R. Greve, G. Gutowski, U. Herzfeld, C. Jackson, J. Johnson, C. Khroulev, E. Larour, A. Levermann, W. H. Lipscomb, M. A. Martin, M. Morlighem, B. R. Parizek, D. Pollard, S. F. Price, D. Ren, E. Rignot, F. Saito, T. Sato, H. Seddik, H. Seroussi, K. Takahashi, R. Walker, and W. Wang. 2013. "Insights into spatial sensitivities of ice mass response to environmental change from the SeaRISE ice sheet modeling project II: Greenland." J. Geophys. Res. Earth Surf. 118 (2): 1025-1044 [Full Text (Link)] [10.1002/jgrf.20076]

    Nowicki, S., R. A. Bindschadler, A. Abe-Ouchi, et al. A. Aschwanden, E. Bueler, H. Choi, J. Fastook, G. Granzow, R. Greve, G. Gutowski, U. Herzfeld, C. Jackson, J. Johnson, C. Khroulev, E. Larour, A. Levermann, W. H. Lipscomb, M. A. Martin, M. Morlighem, B. R. Parizek, D. Pollard, S. F. Price, D. Ren, E. Rignot, F. Saito, T. Sato, H. Seddik, H. Seroussi, K. Takahashi, R. Walker, and W. L. Wang. 2013. "Insights into spatial sensitivities of ice mass response to environmental change from the SeaRISE ice sheet modeling project I: Antarctica." Journal Of Geophysical Research: Earth Surface 118 (2): 1002-1024 [10.1002/jgrf.20081]

    Walker, R. T., B. Parizek, R. Alley, et al. S. Anandakrishnan, K. Riverman, and K. Christianson. 2013. "Ice-shelf tidal flexure and subglacial pressure variations." Earth and Planetary Science Letters 361 422-428 [10.1016/j.epsl.2012.11.008]

                                                                                                                                                                                            
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