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

Abstract:

The motivation for 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. In this part of the study, water isotope and marine ion signals from this ice core since the Last Glacial Maximum (~20,000 years ago) are presented. Ice core water isotope and marine ion signals are indicators of changes in ice sheet and ice shelf extent. Changes in ice sheet and ice shelf extent are linked to regional climate patterns. Water isotope ice core signals have the potential to show changes in these patterns. Variability in ice core levels of marine ions indicate changes in the proximity of Skytrain Ice Rise to open ocean or sea ice. Water isotopes and marine ions (sodium and magnesium) were analysed continuously using cavity ring down spectroscopy and inductively coupled plasma mass spectrometry, respectively. During the Holocene, mean δ¹⁸O was -28 ± 8‰ (± 1σ) and mean δD was -233 ± 46‰ in this ice core. Mean levels of sodium and magnesium were 55 ± 57 ppb and 7 ± 6 ppb, respectively. Sodium and magnesium levels decline from late in the deglaciation into the early Holocene. They then increase 2-fold and become more variable from the early to late Holocene. This increase could indicate a retreat of the ice shelf to its current position.