Reconstructing the East Antarctic ice sheet during the Plio-Pleistocene using geochemical provenance analysis

• Main Author: Bertram, Rachel
• Format: Text
• Language: unknown
• Published: Imperial College London 2018
• Subjects: Antarctic; East Antarctic Ice Sheet; Ross Sea; Wilkes Subglacial Basin; Antarc*; Ice Sheet; Sea ice
• Online Access: https://dx.doi.org/10.25560/83552; http://spiral.imperial.ac.uk/handle/10044/1/83552

Approximately five million years ago, during the early Pliocene, global temperatures were 2 – 4 ⁰C warmer-than-present and the cryosphere was reduced. During the subsequent Plio-Pleistocene, global temperatures gradually cooled and atmospheric carbon dioxide (CO2) concentrations decreased, accompanied by an expansion in the cryosphere, culminating in modern bipolar glaciation. Variations in the extent of the East Antarctic Ice Sheet (EAIS) played a fundamental role in these climate transitions with implications for global sea level, interhemispheric teleconnections and oceanic circulation patterns. Recent geological evidence and ice sheet modelling results, especially from marine-based areas of the EAIS, call for a dynamic East Antarctic ice margin during the early Pliocene warmth, but proximal, geological records for the Plio-Pleistocene are scarce. This thesis aims to improve our understanding of East Antarctic ice dynamics during the Plio-Pleistocene by providing two new records from proximal marine sediment cores. Geochemical variability in these cores is used to determine variations in the provenance of detrital sediments and hence to infer continental erosion patterns and ice margin extent. Primarily the work focuses on radiogenic strontium and neodymium isotopic results complemented by elemental concentrations, detrital K-Ar ages, and Sm-Nd model ages. The two cores, located in the western Ross Sea and offshore the Wilkes Subglacial Basin, show evidence of an early Pliocene dynamic ice margin responding to atmospheric warmth, with deglaciations occurring on millennial timescales. Loss of continental ice and changes in sea ice conditions during the cooling of the mid to late Pliocene, as inferred from the composition of the sediments, was diachronous, highlighting the spatial variability of ice sheet behaviour around the continent. The marine-based Wilkes Subglacial Basin continued to show a waxing and waning ice margin during the Pleistocene emphasising this region’s vulnerability to environmental change, and the potential for ice margin retreat under near future temperatures.