USAP-DC

This project contributes to the joint initiative launched by the U.S. National Science Foundation (NSF) and the U.K. Natural Environment Research Council (NERC) to substantially improve decadal and longer-term projections of ice loss and sea-level rise originating from Thwaites Glacier in West Antarctica. Satellite observations extending over the last 25 years show that Thwaites Glacier is rapidly thinning and accelerating. Over this same period, the Thwaites grounding line, the point at which the glacier transitions from sitting on the seabed to floating, has retreated. Oceanographic studies demonstrate that the main driver of these changes is incursion of warm water from the deep ocean that flows beneath the floating ice shelf and causes basal melting. The period of satellite observation is not long enough to determine how a large glacier, such as Thwaites, responds to long-term and near-term changes in the ocean or the atmosphere. As a result, records of glacier change from the pre-satellite era are required to build a holistic understanding of glacier behavior. Ocean-floor sediments deposited at the retreating grounding line and further offshore contain these longer-term records of changes in the glacier and the adjacent ocean. An additional large unknown is the topography of the seafloor and how it influences interactions of landward-flowing warm water with Thwaites Glacier and affects its stability. Consequently, this project focuses on the seafloor offshore from Thwaites Glacier and the records of past glacial and ocean change contained in the sediments deposited by the glacier and surrounding ocean.

Uncertainty in model projections of the future of Thwaites Glacier will be significantly reduced by cross-disciplinary investigations seaward of the current grounding line, including extracting the record of decadal to millennial variations in warm water incursion, determining the pre-satellite era history of grounding-line migration, and constraining the bathymetric pathways that control flow of warm water to the grounding line. Sedimentary records and glacial landforms preserved on the seafloor will allow reconstruction of changes in drivers and the glacial response to them over a range of timescales, thus providing reference data that can be used to initiate and evaluate the reliability of models. Such data will further provide insights on the influence of poorly understood processes on marine ice sheet dynamics. This project will include an integrated suite of marine and sub-ice shelf research activities aimed at establishing boundary conditions seaward of the Thwaites Glacier grounding line, obtaining records of the external drivers of change, improving knowledge of processes leading to collapse of Thwaites Glacier, and determining the history of past change in grounding line migration and conditions at the glacier base. These objectives will be achieved through high-resolution geophysical surveys of the seafloor and analysis of sediments collected in cores from the inner shelf seaward of the Thwaites Glacier grounding line using ship-based equipment, and from beneath the ice shelf using a corer deployed through the ice shelf via hot water drill holes.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

Person	Role
Wellner, Julia	Investigator and contact
Larter, Robert	Investigator and contact
Minzoni, Rebecca	Co-Investigator
Hogan, Kelly	Co-Investigator
Anderson, John	Co-Investigator
Graham, Alastair	Co-Investigator
Hillenbrand, Claus-Dieter	Co-Investigator
Nitsche, Frank O.	Co-Investigator
Simkins, Lauren	Co-Investigator
Smith, James A.	Co-Investigator

Antarctic Earth Sciences	Award # 1738942
Antarctic Glaciology	Award # 1738942

USAP-1738942_1

Deployment	Type
NBP1902	ship expedition
NBP2002	ship expedition

THOR_data_managment_plan.pdf

Repository	Title (link)	Format(s)	Status
R2R	NBP1902 Expedition data	Not Provided	exists
UK PDC	A multibeam-bathymetric compilation for the southern Amundsen Sea shelf, 1999-2019	NetCDF; ESRI asc	exists
R2R	Expedition Data of NBP2002	Not Provided	exists
USAP-DC	Physical and geochemical data from sediment cores collected offshore Thwaites Glacier	Excel	exists

1. Hogan, K. A., Larter, R. D., Graham, A. G. C., Arthern, R., Kirkham, J. D., Totten Minzoni, R., … Wellner, J. (2020). Revealing the former bed of Thwaites Glacier using sea-floor bathymetry. (doi:10.5194/tc-2020-25)
2. Hogan, K. A., Larter, R. D., Graham, A. G. C., Arthern, R., Kirkham, J. D., Totten Minzoni, R., … Wellner, J. (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(9), 2883–2908. (doi:10.5194/tc-14-2883-2020)
3. Wåhlin, A. K., Graham, A. G. C., Hogan, K. A., Queste, B. Y., Boehme, L., Larter, R. D., … Heywood, K. J. (2021). Pathways and modification of warm water flowing beneath Thwaites Ice Shelf, West Antarctica. Science Advances, 7(15), eabd7254. (doi:10.1126/sciadv.abd7254)
4. Lepp, A. P., Simkins, L. M., Anderson, J. B., Clark, R. W., Wellner, J. S., Hillenbrand, C.-D., Smith, J. A., Lehrmann, A. A., Totten, R., Larter, R. D., Hogan, K. A., Nitsche, F. O., Graham, A. G. C., & Wacker, L. (2022). Sedimentary Signatures of Persistent Subglacial Meltwater Drainage From Thwaites Glacier, Antarctica. Frontiers in Earth Science, 10. https://doi.org/10.3389/feart.2022.863200 (doi:10.3389/feart.2022.863200)
5. Lepp, A. P., Miller, L. E., Anderson, J. B., O’Regan, M., Winsborrow, M. C. M., Smith, J. A., Hillenbrand, C.-D., Wellner, J. S., Prothro, L. O., & Podolskiy, E. A. (2023). Insights into glacial processes from micromorphology of silt-sized sediment. (doi:10.5194/tc-2023-70)
6. Karplus, M. S., Young, T. J., Anandakrishnan, S., Bassis, J. N., Case, E. H., Crawford, A. J., Gold, A., Henry, L., Kingslake, J., Lehrmann, A. A., Montaño, P. A., Pettit, E. C., Scambos, T. A., Sheffield, E. M., Smith, E. C., Turrin, M., & Wellner, J. S. (2023). Strategies to build a positive and inclusive Antarctic field work environment. Annals of Glaciology, 1–7. (doi:10.1017/aog.2023.32)
7. Marschalek, J. W., Thomson, S. N., Hillenbrand, C.-D., Vermeesch, P., Siddoway, C., Carter, A., Nichols, K., Rood, D. H., Venturelli, R. A., Hammond, S. J., Wellner, J., & van de Flierdt, T. (2024). Geological insights from the newly discovered granite of Sif Island between Thwaites and Pine Island glaciers. Antarctic Science, 1–24. (doi:10.1017/s0954102023000287)
8. Clark, R. W., Wellner, J. S., Hillenbrand, C.-D., Totten, R. L., Smith, J. A., Miller, L. E., Larter, R. D., Hogan, K. A., Graham, A. G. C., Nitsche, F. O., Lehrmann, A. A., Lepp, A. P., Kirkham, J. D., Fitzgerald, V. T., Garcia-Barrera, G., Ehrmann, W., & Wacker, L. (2024). Synchronous retreat of Thwaites and Pine Island glaciers in response to external forcings in the presatellite era. Proceedings of the National Academy of Sciences, 121(11). (doi:10.1073/pnas.2211711120)