The variability of ocean circulation, productivity, and sea ice in the Adélie region, East Antarctica, over the last two glacial cycles
Present-day observations near Antarctica’s ice sheets suggest anthropogenic warming is affecting ocean circulation, with implications for further ice sheet melt, and changes to global thermohaline circulation. The mechanisms for ocean-ice sheet-sea ice changes are uncertain, and it is unclear how th...
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| Format: | Thesis |
| Language: | English |
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2022
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| Online Access: | https://eprints.utas.edu.au/47523/ https://eprints.utas.edu.au/47523/1/Pesjak_whole_thesis.pdf |
| Summary: | Present-day observations near Antarctica’s ice sheets suggest anthropogenic warming is affecting ocean circulation, with implications for further ice sheet melt, and changes to global thermohaline circulation. The mechanisms for ocean-ice sheet-sea ice changes are uncertain, and it is unclear how they will respond to warmer than present climates. Sediment records on the Antarctic continental margin provide evidence of significant changes with respect to productivity, ice sheet size and ocean circulation, on glacial to interglacial timescales. In this thesis, I describe the integrated response of the Adélie region of East Antarctica to past orbital forcing driven climate, including during the warmer than present Last Interglacial (Marine Isotope Stage 5e) to provide clues to its future response. I have studied five marine sediment cores from the continental shelf and slope of the Antarctic margin to understand the changes in regional oceanography, regional ice sheet size, seasonal sea ice and primary productivity to deduce the relationships between these components, during glacial cycles over the past >240 k yrs. I use an integrated approach employing sedimentological (grain size, structure, Ice Rafted Debris/ IRD), micropaleontological (diatom data) and geochemical (biogenic silica and X-ray fluorescence/ XRF data) proxies. First, in Chapter 3, I describe the last deglacial retreat of the ice sheet, from the outer continental shelf of the Mertz Trough in the Adélie region. Three facies are identified in core TAN1302-68 based on sedimentological, geochemical, and biogenic changes. Facies III comprises a pebble structure, with high coarse sand to granule count and a geochemically and texturally homogenous matrix, suggesting an ice sheet covered this site. Overlying is Facies IIa, a massive interval with IRD (~1mm sized dispersed grains) and slight changes in Fe and Fe/Ti. Above it is Facies IIb, a laminated interval with IRD, and significant sedimentological (comprising decrease in coarse sand to granule counts ... |
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