An Integrated Study of the Middle Miocene Climate Transition.

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The East Antarctic ice sheet became fully established in the middle Miocene, about 14 million years ago. It is not known why the ice sheet grew at this time, although it is believed that the ice sheet expansion happened in 'fits and starts', over 2 to 3 million years. This time interval is known as the middle Miocene climate transition. Geochemical records show that levels of atmospheric carbon dioxide were not noticeably lower after the climate transition than before. However, this does not necessarily imply that this important greenhouse gas did not influence the climate at this crucial time in Earth's history. Indeed, large changes in the isotopic composition of carbon in the ocean suggest that there were large changes in the global carbon cycle associated with the intervals of rapid ice sheet growth within the climate transition. This proposal aims to determine whether levels of atmospheric carbon dioxide changed within the climate transition, in association with the bursts of ice sheet growth and decay. We will construct records of carbon dioxide trends (i.e., increasing/decreasing carbon dioxide) and sea surface temperatures. We will also generate detailed stratigraphies from different sites, which will enable us to link these records with other records of ice volume, deep sea temperatures and weathering. This will provide the first truly integrated record of the middle Miocene climate transition. This will provide valuable information on the causes and effects of the establishment of the Antarctic ice sheet. The records should shed light on the erratic nature of the climate transition. The long term climate transition appears to have punctuated by intervals of climatic amelioration and deglaciation. The processes operating during such intervals have direct relevance to our understanding of the modern day Antarctic ice sheet and its behaviour under future global warming scenarios.