Geological evidence for past retreat of the ice sheet’s grounding line will be obtained by drilling through ice into the underlying bedrock to collect rock cores. This will take advantage of the US ‘Winkie’ drill, which has been successfully used in the past two Antarctic field seasons by NSF-funded researchers to collect subglacial bedrock samples. Surface exposure dating of the rock samples will be used to determine the timing and duration of past episodes of grounding line migration (both retreat and re-advance).

The project will also reconstruct relative sea-level changes in the region, over the past 10,000 years, by mapping raised beaches and dating organic material (e.g. penguin bones) from islands in Pine Island Bay. Comparing this record with the past ice sheet changes will create a more comprehensive understanding of the conditions under which the Thwaites Glacier grounding line has retreated and re-advanced in the past. This is important for validating models and establishing whether present retreat of the Thwaites glacier system is likely to be reversible.