An age scale for new climate records from Sherman Island, West Antarctica

Few ice cores from the Amundsen and Bellingshausen Sea sectors of the West Antarctic Ice Sheet (WAIS) extend back in time further than a few hundred years. The WAIS is believed to be susceptible to collapse as a result of anthropogenic climate change and may have at least partially collapsed in the past. Understanding the stability of the WAIS during warm periods such as the LIG and Holocene is important. As part of the WACSWAIN project, the British Antarctic Survey's (BAS) Rapid Access Isotope Drill (RAID) was deployed in 2020 on Sherman Island in the Abbott Ice Shelf. We drilled a 323 m deep borehole, with discrete samples of ice chippings collected covering the entire depth range of the drilled ice. The samples were analysed for stable water isotope composition and major ion content at BAS from 2020–2022. Using annual layer counting of chemical records, volcanic horizon identification and modelling, an age scale for the record of 1724 discrete samples is presented. The Sherman Island ice record extends back to greater than 1150 years before present, providing the oldest, continuous, ice-derived palaeoclimate records for the coastal Amundsen-Bellingshausen Sea sectors to date. We demonstrate the potential for recovery of a complete Holocene climate record from Sherman Island in the future, and confidence in the ability of RAID samples to contain sufficiently resolved records for meaningful climatic interpretation.

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