2016-2017 Antarctic

This project will collect short bedrock cores beneath the ice sheet near the Pirrit Hills in West Antarctica. The cores collected in the study will be analyzed for cosmic-ray-produced isotopes of different elements. The presence or absence of these isotopes will provide a definitive test of whether bedrock surfaces were ice-free in the past and due to their different half-lives, ratios of the isotopes will place constraints on the age, frequency and duration of past exposure episodes. The aim is to tie evidence of deglaciation in the past to specific periods of warmer climate and thus to gauge the ice sheet's response to known climate conditions.

This project will collect short bedrock samples, approximately 20 cm in length, beneath the ice sheet near the Ohio Range and Scott Glacier in the Transantarctic Mountains. The sub-ice bedrock samples collected in the study will be analyzed for cosmogenic nuclide concentrations to constrain past variability in the ice volume and height of the West Antarctic Ice Sheet (WAIS). Data obtained from the research will provide targets for data-ice sheet model comparisons to accurately characterize Plio-Pleistocene and future WAIS behavior.

This project will measure the modern spatial gradients in accumulation rate, surface temperature, and water stable isotopes from shallow ice cores in the upstream catchment area of the South Pole 1500-m Ice Core (SPICE Core) to separate spatial (advection) variations from temporal (climate) variations recorded in the SPICE Core record. The project will also improve the SPICE Core ice and gas chronologies by making measurements of ice-flow and snow compaction in the upstream catchment in order to constrain age models of the SPICE Core ice. The new ice-flow measurements will make it possible to define the path of ice from upstream to the SPICE Core drill site to assess spatial gradients in snowfall and to infer histories of snowfall from internal layers within the ice sheet. Results from the project will directly enhance interpretation of the SPICE Core records, and also advance understanding of firn densification and drive next-generation firn models.

The Velvet Ice project will conduct repeat borehole logging of the WAIS Divide deep borehole to study three primary questions: (1) How does the evolution of ice microstructure with time and stress in an ice sheet relate to impurity content, temperature history, and strain rate history? (2) How do variations in ice microstructure (and impurity content?) affect large-scale (1m to 1000m) ice flow patterns near ice sheet centers? (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 answers to these questions require integrating existing ice core and borehole data with a detailed study of ice microstructure using Electron Backscatter Diffraction (EBSD) techniques in combination with careful measurements of borehole deformation through time using Acoustic and Optical Televiewers.

This project will utilize the Intermediate Depth Drill's winch and cable to log the South Pole Ice Core borehole with an oriented laser dust logger. The data from the borehole probe will be used to investigate the depth-age relationship in the South Pole Ice Core, to identify ash layers, and to investigate ice flow and ice sheet physical properties.

This project will utilize the Intermediate Depth Logging Winch to log the Rapid Access Ice Drill (RAID) field trial borehole drilled in 2016-2017 near Minna Bluff in Antarctica. The age of the ice will be determined by optical borehole logging. This field trial will be critical in determining whether or not the RAID borehole wall roughness, and cleanliness, permits optical logging at the level of detail needed for accurate dating of the ice.