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Modern and past processes of ocean-atmosphere-climate interactions in the low-latitude western Pacific and Indian Ocean
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Australian shelf sediments reveal shifts in Miocene Southern Hemisphere Westerlies Wednesday 9th @ 1430-1450, Conference Room 1 Jeroen Groeneveld* , Alfred Wegener Institute for Polar and Marine Research, Telegrafenberg A43, D-14473 Potsdam, Germany Jorijntje Henderiks, Department of Earth Sciences, Uppsala University, Villavägen 16, 75236 Uppsala, Sweden Willem Renema, Naturalis Biodiversity Center, PO Box 9517, 2300 RA Leiden, Netherlands Cecilia McHugh, School of Earth and Environmental Sciences, Queens College (City University of New York), 65-30 Kissena Boulevard, Flushing, NY 11367, USA David De Vleeschouwer, Center for Marine Environmental Sciences (MARUM), University of Bremen, Klagenfurter Strasse, D-28359 Bremen, Germany Beth Christensen, Environmental Studies, Adelphi University, 1 South Avenue SCB 201, Garden City, NY 11530, USA. Presenter Email: jgroeneveld@uni-bremen.de |
The expansion of the Antarctic ice sheet (AIS) ~14 million years ago (Ma) impacted global atmospheric circulation, including the strength and position of the Westerlies and the Intertropical Convergence Zone (ITCZ). We present new sediment records off western Australia (IODP Exp. 356, Sites U1459 and U1464) providing evidence linking high latitude cooling around Antarctica to climate change in the (sub)tropics during the Miocene (Groeneveld et al., Science Adv. 2017). We show that western Australia was arid during the middle Miocene. Southwest Australia became wetter during the late Miocene, while northwest Australia remained arid throughout. Precipitation and river runoff in southwest Australia gradually increased from 12 to 8 Ma, which we relate to a northward migration of the Westerlies possibly due to increased sea ice in the Southern Ocean. Abrupt aridification indicates that the Westerlies shifted back to a position south of Australia after 8 Ma. Our mid-latitude Southern Hemisphere data are consistent with the inference that expansion of sea ice around Antarctica resulted in a northward movement of the Westerlies. This in turn may have pushed tropical atmospheric circulation and the ITCZ northward, shifting the main precipitation belt over large parts of southeast Asia including the South China Sea.
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