WACSWAIN project: isotope and chemical ice core records from Skytrain Ice Rise, Antarctica

The aim of the WArm Climate Stability of the West Antarctic ice sheet in the last INterglacial (WACSWAIN) project is to investigate the possible collapse of the West Antarctic Ice Sheet (WAIS) and its surrounding ice shelves during the Last Interglacial (~120,000 years ago).  As part of this project, a 651-meter ice core was drilled to bedrock at Skytrain Ice Rise in Antarctica during the 2018/2019 field season.  Ions and elements originating from marine sources along with water isotope content in this ice core can be used to infer changes in ice sheet and ice shelf extent.  The stable water isotope signal has the potential to capture both regional climate change and changes in the elevation of the drilling site through time.  Marine chemical content in the ice core could indicate variability in the proximity of the site to a marine environment.  Water isotopes and chemical impurities in the ice core were analysed continuously using cavity ring down spectroscopy and inductively coupled plasma mass spectrometry, respectively. As expected, δ¹⁸O and δD increase from the last glacial maximum to the Holocene.  δ¹⁸O and δD increase and sodium and magnesium levels decline from deglaciation into the early Holocene. δ¹⁸O and δD show an abrupt increase in the early Holocene at about 8,000 years before present.  Sea salt similarly increases 2-fold and becomes more variable about 1,000 years later (7,000 years before present).  These increases could indicate a retreat of the ice shelf to its current position.