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Sci Adv. 2017 May 10;3(5):e1602567. doi: 10.1126/sciadv.1602567. eCollection 2017 May.

Australian shelf sediments reveal shifts in Miocene Southern Hemisphere westerlies.

Author information

1
MARUM-Center for Marine and Environmental Sciences, Department of Geosciences, University of Bremen, 28359 Bremen, Germany.
2
Department of Earth Sciences, Uppsala University, Villavägen 16, 75236 Uppsala, Sweden.
3
Naturalis Biodiversity Center, PO Box 9517, 2300 RA Leiden, Netherlands.
4
School of Earth and Environmental Sciences, Queens College (City University of New York), 65-30 Kissena Boulevard, Flushing, NY 11367, USA.
5
Environmental Studies, Adelphi University, 1 South Avenue SCB 201, Garden City, NY 11530, USA.
6
Institute for Geophysics, University of Texas at Austin, 10100 Burnet Road (R2200), Austin, TX 78758-4445, USA.
7
Energy and Mineral Resources Group (EMR), Geological Institute Rheinisch-Westfälische Technische Hochschule (RWTH), Aachen University, Wuellnerstrasse, Aachen 52056, Germany.
8
School of Earth Sciences, University of Melbourne, Melbourne, Victoria 3010, Australia.
9
International Ocean Discovery Program, Texas A&M University, 1000 Discovery Drive, College Station, TX 77845-9547, USA.
10
Institute of Earth Sciences, University of Graz, Heinrichstrasse 26, Graz 8010, Austria.
11
Atmosphere and Ocean Research Institute, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa-shi, Chiba 277-8564, Japan.

Abstract

Global climate underwent a major reorganization when the Antarctic ice sheet expanded ~14 million years ago (Ma) (1). This event affected global atmospheric circulation, including the strength and position of the westerlies and the Intertropical Convergence Zone (ITCZ), and, therefore, precipitation patterns (2-5). We present new shallow-marine sediment records from the continental shelf of Australia (International Ocean Discovery Program Sites U1459 and U1464) providing the first empirical evidence linking high-latitude cooling around Antarctica to climate change in the (sub)tropics during the Miocene. We show that Western Australia was arid during most of the Middle Miocene. Southwest Australia became wetter during the Late Miocene, creating a climate gradient with the arid interior, whereas 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 or intensification of the westerlies possibly due to increased sea ice in the Southern Ocean (5). Abrupt aridification indicates that the westerlies shifted back to a position south of Australia after 8 Ma. Our midlatitude Southern Hemisphere data are consistent with the inference that expansion of sea ice around Antarctica resulted in a northward movement of the westerlies. In turn, this may have pushed tropical atmospheric circulation and the ITCZ northward, shifting the main precipitation belt over large parts of Southeast Asia (4).

KEYWORDS:

Australia; Hadley Cell; Miocene; Precipitation; Southern Hemisphere; Westerlies

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