New ice core records from West Antarctica and their spatial context: from 1000 to 100,000 years

The West Antarctic Ice Sheet (WAIS) is vulnerable to warming as a result of anthropogenic climate change, with the potential to contribute several metres to global sea level rise over the coming centuries. The Thwaites and Pine Island glaciers are already undergoing acceleration due to climate change, threatening the stability of the WAIS. There is a need to understand the stability of the WAIS during warm periods, such as the Last Interglacial (LIG) when the WAIS is proposed to have retreated, and the Holocene prior to anthropogenic warming. Ice core records can be used to reconstruct climatic changes and infer past ice sheet configurations. However, existing long-term ice records are sparse. Two drilling campaigns were carried out under the WACSWAIN project, aiming to contribute two new ice records to refine the uncertainties of WAIS stability in warm periods. One drilled an ice core to bedrock (651m) on Skytrain Ice Rise, adjacent to the Ronne Ice Shelf; a second used a novel drilling technology (Rapid Access Isotope Drill, RAID), on Sherman Island (SI), obtaining ice chippings to a depth of 323 m. The RAID was previously deployed at Little Dome C in the East Antarctic, obtaining samples to 460 m depth. The records from RAID ice chippings and their continental spatial context are the focus of this thesis. Chemical and water isotope data from RAID-drilled ice samples are presented for the first time and are comparable to those of conventionally-drilled ice cores. The dataset from SI extends to over 1000 years before present, more than doubling the length of existing records from the coastal WAIS. SI shows little overall change in stable water isotope values over the last millennium, and does not demonstrate the increased accumulation rate in recent decades apparent in comparative cores. The RAID record of stable water isotopes from Little Dome C is compared with nearby EPICA Dome C to investigate the limits of common centennial scale variability. An Antarctic-wide array of water isotope records extending through the last glacial period is synchronised. Continental stacks of water isotope records for the Holocene and Last Glacial periods are presented using all available data for the first time, including the new RAID records, placing them into their continental scale spatial context on timescales from 1000 to 20,000 years. This compilation enables an investigation into the spatial variability of the timing and amplitude of major events throughout the last glacial cycle, focusing on the glacial to Holocene transition and an Antarctic Isotopic Maximum (AIM12) event. The timing of onset of events varies by up to 2000 years, with no obvious regional consistency. Results from this thesis highlight the ongoing need for accurate dating and synchronisation of ice cores and the benefit of greater numbers of records. The RAID is a valuable new tool that can rapidly obtain several hundreds of metres of ice samples, producing quality data, comparable to conventional ice cores, to meet this need. The new SI dataset provides a wealth of new data for the coastal Amundsen-Bellingshausen Sea sectors over the last millennium. Comparing the multi-centennial scale variability of a large number of deep water isotope records reveals important spatial differences in Antarctic climate variability.

European Research Council: Horizon 2020 research and innovation programme (grant agreement No. 742224, WACSWAIN)