Publication Date:
2022-10-26
Description:
Author Posting. © American Geophysical Union, 2020. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Paleoceanography and Paleoclimatology 35(12), (2020): e2020PA003853, https://doi.org/10.1029/2020PA003853.
Description:
During the middle Miocene, Earth's climate changed from a global warm period (Miocene Climatic Optimum) into a colder one with the expansion of the Antarctic ice sheet. This prominent climate transition was also a period of drastic changes in global atmospheric circulation. The development of the South Asian monsoon is not well understood and mainly derived from proxy records of wind strength. Data for middle Miocene changes in rainfall are virtually non‐existent for India and the Arabian Sea prior to 11 Ma. This study presents planktic foraminiferal trace element (Mg/Ca and Ba/Ca) and stable oxygen isotope records from NGHP‐01 Site 01A off the coast of West India in the Eastern Arabian Sea (EAS) to reconstruct the regional surface hydrography and hydroclimate in the South Asian monsoon (SAM) region during the middle Miocene. The Ba/Ca and local seawater δ18O (δ18Osw) changes reveal a notable gradual increase in SAM rainfall intensity during the middle Miocene. Additionally to this long‐term increase in precipitation, the seawater δ18O is punctuated by a prominent decrease, i.e. freshening, at ~14 Ma contemporary with Antarctic glaciation. This suggests that Southern Ocean Intermediate Waters (SOIW) transmitted Antarctic salinity changes into the Arabian Sea via an “oceanic tunnel” mechanism. The middle Miocene increase in SAM rainfall is consistent with climate model simulations of an overall strengthening Asian monsoon from the Eocene to the middle/late Miocene with a further acceleration after the middle Miocene climate transition.
Description:
This study has been funded by the National Natural Science Foundation of China through a grant to S. Steinke (NSFC grant No. 41776055) and Z. Jian and S. Steinke (NSFC grant No. 919582080). We express our gratitude to H. Kuhnert (MARUM, University of Bremen) and his team for stable isotope analyses. We thank P. Qiao (Tongji University Shanghai) for technical and analytical support with the ICP‐MS analyses, A. Dolman (Alfred‐Wegener‐Institute, Helmholtz Centre for Polar and Marine Research, Potsdam, Germany) for statistical analyses, and B. Wang (State Key Laboratory of Marine Environmental Science, Xiamen University) and his team for the SEM‐EDAX Energy Dispersive X‐ray Spectroscopy (EDS) analyses. L. Giosan acknowledges funding from USSP and WHOI and thanks colleagues and crew from the NGHP‐01 expedition for intellectual interactions leading to long‐standing interests in the fluvial‐continental margin systems of Peninsular India. J. Groeneveld thanks the State Key Laboratory of Marine Environmental Science (Xiamen University) for a MEL Senior Visiting Fellowship (Project No. MELRS1915).
Description:
2021-05-27
Keywords:
Middle Miocene
;
South Asian monsoon
;
Arabian Sea
;
Stable isotopes
;
Trace elements
Repository Name:
Woods Hole Open Access Server
Type:
Article
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