USAP-DC

Accurate reconstructions and predictions of glacier movement on timescales of human interest require a better understanding of available observations and the ability to model the key processes that govern ice flow. The fact that many of these processes are interconnected, are loosely constrained by data, and involve not only the ice, but also the atmosphere, ocean, and solid Earth, makes this a challenging endeavor, but one that is essential for Earth-system modeling and the resulting climate and sea-level forecasts that are provided to policymakers worldwide. Based on the amount of ice present in the West Antarctic Ice Sheet and its ability to flow and/or melt into the ocean, its complete collapse would result in a global sea-level rise of 3.3 to 5 meters, making its stability and rate of change scientific questions of global societal significance. Whether or not a collapse eventually occurs, a better understanding of the potential West Antarctic contribution to sea level over the coming decades and centuries is necessary when considering the fate of coastal population centers. Recent observations of the Amundsen Sea Embayment of West Antarctica indicate that it is experiencing faster mass loss than any other region of the continent. At present, the long-term stability of this embayment is unknown, with both theory and observations suggesting that collapse is possible. This study is focused on this critical region as well as processes governing changes in outlet glacier flow. To this end, we will test an ice-sheet model against existing observations and improve treatment of key processes within ice sheet models. This is a four-year (one year of no-cost extension) modeling study using the open-source Ice Sheet System Model in coordination with other models to help improve projections of future sea-level change. Overall project goals, which are distributed across the collaborating institutions, are to: 1. hindcast the past two-to-three decades of evolution of the Amundsen Sea Embayment sector to determine controlling processes, incorporate and test parameterizations, and assess and improve model initialization, spinup, and performance; 2. utilize observations from glacial settings and efficient process-oriented models to develop a better understanding of key processes associated with outlet glacier dynamics and to create numerically efficient parameterizations for these often sub-grid-scale processes; 3. project a range of evolutions of the Amundsen Sea Embayment sector in the next several centuries given various forcings and inclusion or omission of physical processes in the model.

Person	Role
Pollard, David	Co-Investigator
Parizek, Byron R.	Investigator and contact

Antarctic Glaciology

Award # 1443190

USAP-1443190_1

DataManagementPlan_1443190.pdf

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2. Pollard, D., W. Chang, M. Haran, P. Applegate and R. DeConto. 2016. Large ensemble modeling of last deglacial retreat of the West Antarctic Ice Sheet: comparison of simple and advanced statistical techniques. Geosci. Model Devel., 9, 1697-1723.
3. Stevens, N.T. 2015. Ice-Age Cycling Enhancement of Volcanism and Geothermal Heat Flux: A Stress Modeling Study. pp. 49. A Master Thesis in Geosciences, Penn State Univ., Univ. Park, PA.
4. Walker R.T., B.R. Parizek, R.B. Alley, and S.M.J. Nowicki. 2016. A Viscoelastic Model of Ice Stream Flow with Application to Stick-Slip Motion. Front. Earth Sci. 4:2. doi: 10.3389/feart.2016.00002 (doi:10.3389/feart.2016.00002)
5. Stevens, N. T., B.R. Parizek, and R. B. Alley. Enhancement of volcanism and geothermal heat flux by ice-age cycling: A stress modeling study of Greenland, J. Geophys. Res. Earth Surf., 121, 1456–1471, doi:10.1002/2016JF003855, 2016. (doi:10.1002/2016JF003855)
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7. Holschuh, N. 2016. Methods and applications of radio frequency geophysics in glaciology. pp. 122. A Dissertation in Geosciences, Penn State Univ., Univ. Park, PA.
8. Holland, D.M., D. Voytenko, K. Christianson, T.H. Dixon, M.J. Mei, B.R. Parizek, I. Vaňková, R.T. Walker, J.I. Walter, K. Nicholls, and D. Holland. An intensive observation of calving at Helheim Glacier, East Greenland. Oceanography 29(4):46–61, https://doi.org/10.5670/oceanog.2016.98, 2016. (doi:10.5670/oceanog.2016.98)
9. Holschuh, N., B.R. Parizek, R.B. Alley, S.Anandakrishnan. Decoding ice sheet behavior using englacial layer slopes. Geophys. Res. Lett., 44, pp. 10, doi:10.1002/2017GL073417, 2017. (doi:10.1002/2017GL073417)
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11. Lampkin DJ, Parizek B, Larour EY, Seroussi H, Joseph C and Cavanagh JP (2018) Toward Improved Understanding of Changes in Greenland Outlet Glacier Shear Margin Dynamics in a Warming Climate. Front. Earth Sci. 6:156. doi: 10.3389/feart.2018.00156 (doi:10.3389/feart.2018.00156)
12. Vankova, I., Voytenko, D., Nicholls, K. W., Xie, S., Parizek, B. R., & Holland, D. M. (2018). Vertical structure of diurnal englacial hydrology cycle at Helheim Glacier, East Greenland. Geophysical Research Letters, 45, 11. 8352-8362. doi:10.1029/2018GL077869 (doi:10.1029/2018GL077869)
13. 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, p. 1–4, doi:10.1130/G45880.1 (doi:10.1130/G45880.1)
14. Atsuhiro MUTO, Richard B. ALLEY, Byron R. PARIZEK, Sridhar ANANDAKRISHNAN, Annals of Glaciology, Bed-type variability and till (dis)continuity beneath Thwaites Glacier, West Antarctica accepted, 2019
15. 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, doi:10.1016/j.epsl.2018.12.008 (doi:10.1016/j.epsl.2018.12.008)
16. 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, doi:10.1016/j.epsl.2019.03.026 (doi:10.1016/j.epsl.2019.03.026)
17. Alley, R. B., Pollard, D., Parizek, B. R., Anandakrishnan, S., Pourpoint, M., Stevens, N. T., et al. (2019). Possible role for tectonics in the evolving stability of the Greenland Ice Sheet. Journal of Geophysical Research: Earth Surface, 124. https://doi.org/10.1029/ 2018JF004714 (doi:10.1029/ 2018JF004714)
18. 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, doi:10.1016/j.epsl.2019.03.035 (doi:10.1016/j.epsl.2019.03.035)
19. Vankova, I. 2018. Ice and Ocean Dynamics in a Glacier Fjord. Ph.D. Thesis, New York University, New York, NY.
20. Li, W. 2018. ENSEMBLE SENSITIVITY ANALYSIS OF ICE FLOW SIMULATIONS WITH DIFFERENT PARAMETRIC MODEL UNCERTAINTIES. M.Sc. Thesis, The Pennsylvania State University, University Park, PA.
21. Alley, R. B., Pollard, D., Parizek, B. R., Anandakrishnan, S., Pourpoint, M., Stevens, N. T., … Holschuh, N. (2019). Possible Role for Tectonics in the Evolving Stability of the Greenland Ice Sheet. Journal of Geophysical Research: Earth Surface, 124(1), 97–115. (doi:10.1029/2018jf004714)
22. Christianson, K., Bushuk, M., Dutrieux, P., Parizek, B. R., Joughin, I. R., Alley, R. B., … Holland, D. M. (2016). Sensitivity of Pine Island Glacier to observed ocean forcing. Geophysical Research Letters, 43(20), 10,817–10,825. (doi:10.1002/2016gl070500)
23. Vaňková, I., Voytenko, D., Nicholls, K. W., Xie, S., Parizek, B. R., & Holland, D. M. (2018). Vertical Structure of Diurnal Englacial Hydrology Cycle at Helheim Glacier, East Greenland. Geophysical Research Letters, 45(16), 8352–8362. (doi:10.1029/2018gl077869)
24. Holschuh, N., Parizek, B. R., Alley, R. B., & Anandakrishnan, S. (2017). Decoding ice sheet behavior using englacial layer slopes. Geophysical Research Letters, 44(11), 5561–5570. (doi:10.1002/2017gl073417)
25. Stevens, N. T., Parizek, B. R., & Alley, R. B. (2016). Enhancement of volcanism and geothermal heat flux by ice‐age cycling: A stress modeling study of Greenland. Journal of Geophysical Research: Earth Surface, 121(8), 1456–1471. (doi:10.1002/2016jf003855)