A Late Glacial and Holocene tephrostratigraphy for Antarctica

"This project will reconstruct the Late Glacial and Holocene volcanic history represented within the Fletcher ice core from the Fletcher Promontory to southwest of the Ronne Ice Shelf, western Antarctica. The 654.3 m-long ice core was drilled in 2011-2 by the British Antarctic Survey to investigate ice-sea dynamics at the Last Glacial-Interglacial transition (Mulvaney et al. 2014).

The small ice sheet is sensitive to climate variability, and the ice core promises to provide a high-resolution record of Holocene external forcing and ice sheet responses. Preservation of tephra from explosive volcanic eruptions within the ice presents opportunities to 1) date and inter-correlate regional ice cores, 2) refine the understanding of volcanic impacts on local to global spatial and temporal scales, and 3) explore the significance of atmospheric circulation patterns contributing to tephra deposition at the sampling site, including the effects of sediment remobilisation on the ice core geochemical record.

Previous tephra research in eastern Antarctica has illustrated that high-frequency local Antarctic eruptions have the potential to contribute to volcanic perturbations of the Earth's radiative balance as well as ice surface albedo (Narcisi et al. 2019).

This project aims to establish the contributions of local (i.e., Antarctic and Southern Ocean), mid- and high-latitude eruptions to the volcanic signal in Antarctic ice, and to examine variability in tephra provenances across climate transitions as a proxy for past environmental change. It will comprise the first extended assessment of volcanic sources in an Antarctic core, guided by a continuous microparticle record that will highlight short-lived peaks of elevated particulate representation.

By establishing the sources of tephra represented in the ice core through glass geochemical analysis, including the representation of secondary deposition, the study will investigate variability in tephra provenances and frequency with respect to Late Glacial and Holocene climate oscillations. Specific objectives are to:

1) Geochemically characterise all visible tephras to identify their sources

2) Evaluate the occurrence of cryptotephras using existing microparticle records, and geochemically characterise selected layers to identify their sources

3) Reconstruct continuous volcanic histories for selected time periods, chiefly during the Common Era and periods of climate regime shifts 4) Evaluate the occurrence of reworked tephra as a background tephra signal in western Antarctic ice

5) With the aid of volcanic ash dispersion modelling, investigate variability in atmospheric circulation dynamics through analysis of source regions and over multi-centennial timeframes

The candidate's training will encompass tephra geochemical analysis and interpretation, representing the primary methodology applied in the project, as well as ash cloud dispersion modelling. The supervisory team will ensure that the candidate obtains a solid understanding of ice sheet dynamics and atmospheric circulation pattens needed to interpret the broader significance of the tephra results.

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