Interhemispheric Deep Water Exchange Revealed by Authigenic Neodymium Isotopes in the Southern Atlantic Ocean During the Last One Million Years
The deep Southern Ocean circulation is of major significance for our understanding of the ocean’s impact on Earth’s climate as uptake and release of CO2 strongly depend on the redistribution of well and poorly ventilated water masses. Authigenic neodymium isotopes (eNd) preserved in deep sea sedimen...
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| Format: | Doctoral or Postdoctoral Thesis |
| Language: | English |
| Published: |
2024
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| Online Access: | https://archiv.ub.uni-heidelberg.de/volltextserver/35228/ https://archiv.ub.uni-heidelberg.de/volltextserverhttps://archiv.ub.uni-heidelberg.de/volltextserver/35228/1/Dissertation-R%C3%BCckert.pdf https://doi.org/10.11588/heidok.00035228 https://nbn-resolving.org/urn:nbn:de:bsz:16-heidok-352282 |
| Summary: | The deep Southern Ocean circulation is of major significance for our understanding of the ocean’s impact on Earth’s climate as uptake and release of CO2 strongly depend on the redistribution of well and poorly ventilated water masses. Authigenic neodymium isotopes (eNd) preserved in deep sea sediment have proven useful to study the deep ocean circulation and water mass provenance and are of special interest over major climate changes such as the Mid Pleistocene Transition (MPT). In this thesis, the authigenic Nd isotopic composition of two Atlantic sediment sites south of the Polar Front were investigated. The record at site ODP 1093 spans the last 1 Ma in millennial resolution, while ODP 1094 covers terminations I, II, V and the MPT. The results yield the first 1 Ma eNd benchmark in the southern Atlantic Ocean, which shows a variable behavior synchronous with climate. Based on the strong correlation with climate in ODP 1093, an age model was developed. The observed "Nd point to an interplay of advective and diffusive processes influencing the eNd signatures preserved in the authigenic coating. The interhemispheric eNd gradient was discussed, to investigate circulation strength changes across the Atlantic Ocean in the past 1 Ma. The gradient observations indicate a potential bi-stability of the circulation starting during the MPT with the occurrence of the first strong decrease in circulation strength. |
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