Cenozoic ice sheets and ocean variability controls on sedimentation in glaciated margins
The Antarctic Circumpolar Current (ACC) connects all major ocean basins, links the deep and shallow layers of the oceans and has a strong influence on global ocean circulation, biogeochemical cycles, the stability of the Antarctic ice sheet and thereby Earth´s climate system. However, the timing of...
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| Other Authors: | , |
| Format: | Doctoral or Postdoctoral Thesis |
| Language: | unknown |
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Universidad de Granada
2020
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| Online Access: | http://hdl.handle.net/10261/233785 https://doi.org/10.13039/501100004837 |
| Summary: | The Antarctic Circumpolar Current (ACC) connects all major ocean basins, links the deep and shallow layers of the oceans and has a strong influence on global ocean circulation, biogeochemical cycles, the stability of the Antarctic ice sheet and thereby Earth´s climate system. However, the timing of the onset of the ACC and the establishment of a vigorous, deep circumpolar flow, similar to presentday remain controversial. Moreover, the links between the ACC and the Antarctic ice sheet in past warmer than today climates are poorly known. This knowledge is essential for improving our understanding on ACC-Antarctic ice sheet interactions in the ongoing climate warming that can inform coupled ocean-ice sheet global climate models used to forecast future changes. In this context, this PhD thesis aims to advance our understanding on the evolution of the ACC since its initiation (proto-ACC) to the time when the modern deep ACC is established over the last 34 million years (Ma). In addition, we aim to relate proto-ACC dynamics offshore the eastern Wilkes Land margin to Antarctic ice sheet behaviour during the warm late Oligocene and the earliest Miocene (24-23 Ma), including the second major Antarctic glaciation (23.03 Ma). To achieve these objectives, we conducted sedimentological, geochemical, and isotopic analyses on sedimentary sequences recovered by the Deep Sea Drilling Project Leg 28 (Sites 269 and 274) and Leg 29 (Site 278) across both sides of the Tasmanian Gateway. In addition, we conducted a study in the glaciated margins of Lake Baikal (Russia). There the tectonic and sea level histories are well known allowing us to test, using bathymetric and seismic reflection data, the climate vs. sea-level changes and tectonic controls on deep-water deposition in glaciated margins. This PhD Thesis shows that between 34-30 Ma, deep waters from the South Atlantic and Indian Ocean did not flow into the Southwest Pacific via the Tasmanian Gateway. Instead, the Southwest Pacific deep water circulation was characterised by the ... |
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