Changes in ocean circulation and carbonate chemistry in the Australian sector of the Southern Ocean during the last 500,000 years
Stable oxygen and carbon isotope records and carbonate dissolution proxy records were used to reconstruct glacial/interglacial changes in ocean circulation, deep-water ventilation and carbonate chemistry in the Australian sector of the Southern Ocean for the last 500 kyr. Carbonate preservation reco...
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| Other Authors: | , |
| Format: | Doctoral or Postdoctoral Thesis |
| Language: | English |
| Published: |
2003
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| Online Access: | https://nbn-resolving.org/urn:nbn:de:gbv:8-diss-9923 https://macau.uni-kiel.de/receive/diss_mods_00000992 https://macau.uni-kiel.de/servlets/MCRFileNodeServlet/dissertation_derivate_00000992/d992.pdf |
| Summary: | Stable oxygen and carbon isotope records and carbonate dissolution proxy records were used to reconstruct glacial/interglacial changes in ocean circulation, deep-water ventilation and carbonate chemistry in the Australian sector of the Southern Ocean for the last 500 kyr. Carbonate preservation records indicated a longitudinal gradient in Southern Ocean deep-water alkalinity at 110°E that persisted through glacial/interglacial stages. In contrast to previous studies suggesting the “Atlantic-type” carbonate preservation pattern in the entire Southern Ocean with enhanced carbonate preservation during interglacials and increased carbonate dissolution during glacials, this study, however, revealed that the reversed “Pacific-type” pattern of glacial/interglacial carbonate preservation expanded from the Pacific into the Australian sector of the Southern Ocean up to 110°E. This result implies that deep-waters in the Australian sector flow westwards against the predominant eastward drift in the Southern Ocean. Epibenthic stable carbon isotope records depicted a detailed variability of Pleistocene deep-water circulation and ventilation with new implications for glacial deep-water circulation. The major problem in understanding the glacial deep-water circulation and isotope signatures below 2,500 m derives from the extremely low delta13C values in the Atlantic-Indian sector of the Southern Ocean contrasting relatively high delta13C values in the central Pacific. The glacial delta13C signatures of deep-waters in the Australian sector represent a mixture of both endmembers and thus link the isotope signatures of both regions. This suggests a westward deep-water flow to the south of Australia, which is consistent with the “Pacific-type” pattern of carbonate preservation in this area. These findings suggest the SW Pacific, in particular the Ross Sea, as a source region for nutrient-depleted Glacial Antarctic Bottom Water, which ventilated both, the Australian sector of the Southern Ocean and the deep Pacific. Considering the ... |
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