School of Geography - Theses
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ItemA northward shift of the Southern Westerlies during the Antarctic cold reversal: evidence from Tasmania, Australia( 2018)The Southern Hemisphere Westerlies are one of the most important components of the Earth’s climate system: they are the primary driver of Southern Hemisphere climate, they modulate global ocean circulation patterns, and they are a critical natural driver of atmospheric CO2 variation. Despite their clear importance, their dynamics in response to rapid changes in climate boundary conditions are poorly understood. Critical to this lack of understanding is (1) an absence of robust proxy-data from the Australian sector of the Southern Hemisphere, which hampers attempts at predictive modelling, and (2) a lack of consensus within the palaeoclimate literature as to how the Southern Westerlies have responded to past periods of rapid climate change. A case in point is the behaviour of the Southern Westerlies during the Antarctic Cold Reversal (ACR; 14,000 – 13,700 years ago), a millennial-scale climate event that punctuated the termination of the Last Ice Age in the Southern Hemisphere. A thorough understanding of how this critical climate component changed during the ACR is hampered by the only available proxy-dataset from the Australian sector of the Southern Hemisphere, which disagrees with records from other regions, and with the leading conceptual understanding of Southern Westerly dynamics. To address this discord, this thesis sought to reconstruct the dynamics of the Southern Westerlies in the Australian sector by developing two robust terrestrial proxy-datasets from Tasmania, Australia, covering the ACR. The results from this thesis demonstrate that the Southern Westerlies responded to the climatic changes of the ACR as predicted by the leading conceptual understanding of their dynamics, and also revealed that they responded symmetrically across the Southern Hemisphere, coincident with substantial changes in atmospheric CO2 variation. This thesis supports the hypotheses that the Southern Westerlies are the primary determinant of long-term Tasmanian climate variation and are a critical regulator of long-term global atmospheric CO2 variation.