Middle Miocene Intensification of South Asian Monsoonal Rainfall
Journal
Paleoceanography and Paleoclimatology
Journal Volume
35
Journal Issue
12
Date Issued
2020
Author(s)
Abstract
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. ©2020. American Geophysical Union. All Rights Reserved.
Subjects
Arabian Sea; middle Miocene; South Asian monsoon; stable isotopes; trace elements
Other Subjects
atmospheric circulation; climate modeling; Eocene; global climate; hydrography; hydrometeorology; Miocene; oxygen isotope; precipitation intensity; rainfall; seawater; trace element; Antarctic Ice Sheet; Antarctica; Arabian Sea; India; Indian Ocean; South Asia; Southern Ocean
Type
journal article