A diatom assessment of the extent and variation of the late Cenozoic Southern Hemisphere cryosphere, Pacific sector of the Southern Ocean

Gerhard.Kuhn [ at ] awi.de


Climate change represents the most significant challenge that humanity will face in the coming decades and centuries. Threats posed by excessive anthropogenic CO2 input include rising global temperatures, increasing frequency and severity of extreme weather events, and rising sea levels that threaten to engulf low-lying coastal regions and even entire island nations, not to mention key militarily strategic locations. The scale of these changes is expected to be unprecedented since the development of agriculture and the earliest sedentary human societies ~10,000 years ago. A more complete understanding of climate history and cryosphere evolution is therefore necessary to 1) augment our understanding of the scope and mechanisms of climate change and 2) to educate the public in order to encourage climate remediation responses from world governments. The research undertaken for this dissertation incorporates two primary ideas of interest in assessing the threat of climate change to human societies: 1) the use of the warm early Pliocene as an analog for conditions expected under future warming scenarios, and 2) ice sheet-ocean interactions along the unstable margin of West Antarctic Ice Sheet. To achieve these goals, two Southern Ocean sediment cores were used to generate high resolution records of microfossil assemblage change during discreet intervals of Plio- Pleistocene time (the last ~5.1 myr), which was correlated to changes recorded in δ18O records (a global proxy) to characterize response to Milankovitch orbital parameters. The Ross Sea sourced AND-1B core contains four separate early Pliocene intervals reflecting continuously open water conditions in a region presently covered by an 80 m-thick ice shelf. Diatom indices were developed to create a detailed age model, which was employed to document changes in sediment source areas and fossil fragmentation related to low amplitude obliquity-driven climate fluctuations. Core PS58/254 was collected from the Amundsen Sea, and records modern glacial/interglacial variability and the Mid-Pleistocene Transition (MPT), a period when obliquity dominance of cryosphere fluctuations was overridden by modern eccentricity paced variability. This core was used to document the effect the MPT had on Southern Ocean ecology. Finally, the two cores are used in conjunction to develop a simplified model of the interaction of multiple parameters on global ice volume.

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Thesis (PhD)
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Konfirst, M. (2011): A diatom assessment of the extent and variation of the late Cenozoic Southern Hemisphere cryosphere, Pacific sector of the Southern Ocean , PhD thesis, Department of Geology and Environmental Geoscience.

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ANT > XVIII > 5a

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