Impact of middle to late Miocene global cooling on Indo-Pacific climate evolution and ocean circulation
The Miocene Epoch (23 to 5.3 Ma) is an interval of major interest in Earth’s climate history, as it was marked by a fundamental transition from a warmer-than-modern climate phase to a much cooler mode with permanent ice sheets on Antarctica. The Miocene Climatic Optimum (MCO), which started at ~16.9 Ma, represents the warmest climate phase of the Neogene. This warmer phase characterized by high amplitude climate variability, ended with stepwise expansion of the Antarctic Ice sheet between ~14.7 and 13.8 Ma during the Middle Miocene Climate Transition (MMCT). Climate cooling continued during the late Miocene and was accompanied by reorganization of the ocean-atmosphere circulation and by major changes in terrestrial and marine ecosystems. Todate, the lack of continuous Miocene sedimentary archives in strategic ocean locations has, however, limited the understanding of middle to late Miocene climatic and oceanographic evolution. This thesis presents high-resolution multi-proxy records from newly drilled International Ocean Discovery Program (IODP) sites from the equatorial Indian Ocean (U1443) and the equatorial Western Pacific Ocean (U1490) and from Ocean Drilling Program (ODP) Site 1146 in the South China Sea. The principal objectives of this work are: (1) to tease out the relationships between climate, ocean circulation and carbonate accumulation during the middle to late Miocene, (2) to advance understanding of climate-carbon cycle dynamics on a warmer Miocene Earth, (3) to investigate the detailed evolution of the Southeast Asian Monsoon during the late Miocene and (4) to reconstruct the characteristics and orbital-scale variability of intermediate and deep water masses in the Indian and Pacific Oceans through the MCO, MMCT and late Miocene cooling.
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