USAP-DC

This award supports a project to develop a better understanding of the relation between ice microstructure, impurities, and ice flow and their connection to climate history for the West Antarctic Ice Sheet (WAIS) ice core site. This work builds on several ongoing studies at Siple Dome in West Antarctica and Dome C in East Antarctica. It is well known that the microstructure of ice evolves with depth and time in an ice sheet. This evolution of microstructure depends on the ice flow field, temperature, and impurity content. The ice flow field, in turn, depends on microstructure, leading to feedbacks that create layered variation in microstructure that relates to climate and flow history. The research proposed here focuses on developing a better understanding of: 1) how ice microstructure evolves with time and stress in an ice sheet and how that relates to impurity content, temperature, and strain rate; 2) how variations in ice microstructure and impurity content affect ice flow patterns near ice divides (on both small (1cm to 1m) and large (1m to 100km) scales); and 3) in what ways is the spatial variability of ice microstructure and its effect on ice flow important for interpretation of climate history in the WAIS Divide ice core. The study will integrate existing ice core and borehole data with a detailed study of ice microstructure using Electron Backscatter Diffraction (EBSD) techniques and measurements of borehole deformation through time using Acoustic Televiewers. This will be the first study to combine these two novel techniques for studying the relation between microstructure and deformation and it will build on other data being collected as part of other WAIS Divide borehole logging projects (e.g. sonic velocity, optical dust logging, temperature and other measurements on the ice core including fabric measurements from thin section analyses as well as studies of ice chemistry and stable isotopes. The intellectual merit of the work is that it will improve interpretation of ice core data (especially information on past accumulation) and overall understanding of ice flow. The broader impacts are that the work will ultimately contribute to a better interpretation of ice core records for both paleoclimate studies and for ice flow history, both of which connect to the broader questions of the role of ice in the climate system. The work will also advance the careers of two early-career female scientists, including one with a hearing impairment disability. This project will support a PhD student at the UAF and provide research and field experience for two or three undergraduates at Dartmouth. The PIs plan to include a teacher on their field team and collaborate with UAF's "From STEM to STEAM" toward enhancing the connection between art and science.

Person	Role
Pettit, Erin	Investigator and contact
Obbard, Rachel	Co-Investigator

Antarctic Glaciology	Award # 1142167
Antarctic Glaciology	Award # 1142035

USAP-1142167_1

None in the Database

Repository	Title (link)	Format(s)	Status
UNAVCO	GPS Horizontal Strain Network	None	no link
USAP-DC	WAIS Divide Borehole Deformation	None	exists
USAP-DC	South Pole (SPICEcore) Borehole Deformation	None	exists
USAP-DC	ApRES Firn Density Study	None	exists
USAP-DC	ApRES Vertical Strain Study	None	exists

1. Obbard, R. W., Sarrazin, P., Vo, N. T., Palmowski, J., Ngo, P., Zacny, K., & Begland, Z. (2021). Micro computed tomography for in situ analysis of subsurface structure. 2021 IEEE Aerospace Conference (50100). (doi:10.1109/aero50100.2021.9438421)