USAP-DC

The West Antarctic Ice Sheet contains enough ice to raise global sea levels by 3-4 meters. Ice-sheet volume falls, and sea level increases, when more ice is lost to the ocean by glacier flow than is replaced by snowfall. Glacier speed is reduced when ice shelves, which are the floating extensions of the ice sheets, are present. Processes that affect ice shelf thickness and extent therefore influence the rates of grounded ice loss and sea-level rise. West Antarctica is currently losing ice, at an accelerating rate, with most loss occurring in the Amundsen Sea region via discharge from Pine Island and Thwaites glaciers. This loss was initiated by increased circulation of relatively warm ocean water beneath these glacier's ice shelves, causing them to thin by melting. However, this melting also depends on how the changing shape of the ice shelves affects the ocean circulation beneath them and the speeds of the grounded glaciers upstream. Limited understanding of these processes leads to uncertainties in estimates of future ice loss. This interdisciplinary project brings together glaciologists and oceanographers from three US institutions to study the interactions between changing glacier flow, ice shelf shape and extent, and ocean circulation. Data and numerical models will be used to identify the key processes that determine how rapidly this region can shed ice. The project team will train postdocs and graduate students in cutting-edge modeling techniques, and educate the public about Antarctic ice loss through talks, school science fairs, and Seattle Science Center's annual Polar Science Weekend. The project team will conduct simulations, using a combination of ice-sheet and ocean models, to reduce uncertainties in projected ice loss from Pine Island and Thwaites glaciers by: (i) assessing how ice-shelf melt rates will change as the ice-shelf cavities evolve through melting and grounding-line retreat, and (ii) improving understanding of the sensitivity of sub-shelf melt rates to changes in ocean state on the nearby continental shelf. These studies will reduce uncertainty on ice loss and sea-level rise estimates, and lay the groundwork for development of future fully-coupled ice-sheet/ocean models. The project will first develop high-resolution ice-shelf-cavity circulation models driven by modern observed regional ocean state and validated with estimates of melt derived from satellite observations. Next, an ice-flow model will be used to estimate the future grounding retreat. An iterative process with the ocean-circulation and ice-flow models will then simulate melt rates at each stage of retreat. These results will help assess the validity of the hypothesis that unstable collapse of the Amundsen Sea sector of West Antarctica is underway, which was based on simplified models of melt rate. These models will also provide a better understanding of the sensitivity of melt to regional forcing such as changes in Circumpolar Deep Water temperature and wind-driven changes in thermocline height. Finally, several semi-coupled ice-ocean simulations will help determine the influence of the ocean-circulation driven melt over the next several decades. These simulations will provide a much-improved understanding of the linkages between far-field ocean forcing, cavity circulation and melting, and ice-sheet response.

Person	Role
Joughin, Ian	Investigator and contact
Dutrieux, Pierre	Co-Investigator
Padman, Laurence	Investigator
Springer, Scott	Co-Investigator

Antarctic Glaciology	Award # 1643285
Antarctic Integrated System Science	Award # 1643285
Antarctic Ocean and Atmospheric Sciences	Award # 1643285
Antarctic Glaciology	Award # 1643174
Antarctic Integrated System Science	Award # 1643174
Antarctic Ocean and Atmospheric Sciences	Award # 1643174

USAP-1643285_1

None in the Database

Repository	Title (link)	Format(s)	Status
Uni. Washington ResearchWorks Archive	Data associated with Ice-Shelf Retreat Drives Recent Pine Island Glacier Speedup and Ocean-Induced Melt Volume Directly Paces Ice Loss from Pine Island Glacier	Excel	exists
GitHub	Beta Version of Plume Model	None	exists
GitHub	icepack	None	exists
GitHub	Pine Island Basin Scale Model	None	exists

1. Davis, P. E. D., Jenkins, A., Nicholls, K. W., Brennan, P. V., Abrahamsen, E. P., Heywood, K. J., Dutrieux, P., Cho, K., & Kim, T. (2018). Variability in Basal Melting Beneath Pine Island Ice Shelf on Weekly to Monthly Timescales. Journal of Geophysical Research: Oceans, 123(11), 8655–8669. Portico. (doi:10.1029/2018jc014464)
2. Shapero, D. R., Badgeley, J. A., Hoffman, A. O., & Joughin, I. R. (2021). icepack: a new glacier flow modeling package in Python, version 1.0. Geoscientific Model Development, 14(7), 4593–4616. (doi:10.5194/gmd-14-4593-2021)
3. Selley, H. L., Hogg, A. E., Cornford, S., Dutrieux, P., Shepherd, A., Wuite, J., Floricioiu, D., Kusk, A., Nagler, T., Gilbert, L., Slater, T., & Kim, T.-W. (2021). Widespread increase in dynamic imbalance in the Getz region of Antarctica from 1994 to 2018. Nature Communications, 12(1). (doi:10.1038/s41467-021-21321-1)
4. Springer, S., Mack, S., Dutrieux, P., Padman, L., Joughin, I., & Shean, D. (2020). Dependence of Pine Island Glacier Ice Shelf Basal Melt Rates on Subgrid-Scale Parameterizations of Mixing. (doi:10.1002/essoar.10503807.1)
5. Arnscheidt, C. W., Marshall, J., Dutrieux, P., Rye, C. D., & Ramadhan, A. (2021). On the Settling Depth of Meltwater Escaping from beneath Antarctic Ice Shelves. Journal of Physical Oceanography, 51(7), 2257-2270. (doi:10.1175/JPO-D-20-0286.1)
6. Jenkins, A., Shoosmith, D., Dutrieux, P. et al. West Antarctic Ice Sheet retreat in the Amundsen Sea driven by decadal oceanic variability. Nature Geosci 11, 733–738 (2018). (doi: 10.1038/s41561-018-0207-4 )
7. Ian Joughin et al., Ice-shelf retreat drives recent Pine Island Glacier speedup. Sci. Adv. 7, eabg3080 (2021). (doi:10.1126/sciadv.abg3080)
8. Ian Joughin et al., Ocean-induced melt volume directly paces ice loss from Pine Island Glacier. Sci. Adv. 7, eabi5738 (2021). (doi:10.1126/sciadv.abi5738)
9. Kim, Tae?Wan and Yang, Hee Won and Dutrieux, Pierre and Wåhlin, Anna K. and Jenkins, Adrian and Kim, Yeong Gi and Ha, Ho Kyung and Kim, Chang?Sin and Cho, Kyoung?Ho and Park, Taewook and Park, Jisoo and Lee, SangHoon and Cho, Yang?Ki. (2021). Interannual Variation of Modified Circumpolar Deep Water in the Dotson?Getz Trough, West Antarctica. Journal of Geophysical Research: Oceans. 126 (12). (doi:10.1029/2021JC017491 )
10. Holland, Paul R. and Bracegirdle, Thomas J. and Dutrieux, Pierre and Jenkins, Adrian and Steig, Eric J. (2019). West Antarctic ice loss influenced by internal climate variability and anthropogenic forcing. Nature Geoscience. 12 (9), 718 to 724. (doi:10.1038/s41561-019-0420-9)
11. Shean, David E. and Joughin, Ian R. and Dutrieux, Pierre and Smith, Benjamin E. and Berthier, Etienne. (2018). Ice shelf basal melt rates from a high-resolution DEM record for Pine Island Glacier, Antarctica. The Cryosphere Discussions. 1 to 39 (doi:10.5194/tc-2018-209)
12. Shapero, D., Badgeley, J., Hoffmann, A., & Joughin, I. (2021). icepack: a new glacier flow modeling package in Python, version 1.0. (doi:10.5194/gmd-2020-419)