Publication Date:
2023-08-08
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 (SAM) is not well understood and mainly derived from proxy records of wind strength. Proxy records 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 SAM region during the middle Miocene. The Ba/Ca and local seawater d18O (d18Osw) 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.
Keywords:
adjusted; AGE; Calculated from Mg/Ca ratios (Anand et al., 2003); CDRILL; Core drilling; DEPTH, sediment/rock; Foraminifera, benthic; Foraminifera, benthic δ18O; Fragmentation index, planktic foraminifera; ICP-MS (Thermo X7); Mass spectrometer, Finnigan, MAT253; connected with Automatic carbonate preparation line, Finnigan, Kiel III; NGHP-01-01A; Sea surface temperature; Trilobatus sacculifer, Barium/Calcium ratio; Trilobatus sacculifer, Manganese/Calcium ratio; Trilobatus sacculifer, δ18O; δ18O, seawater, reconstructed
Type:
Dataset
Format:
text/tab-separated-values, 1310 data points
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