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Variability of the Indian Monsoon in the Andaman Sea Across the Miocene‐Pliocene Transition
Author(s) -
Jöhnck Janika,
Kuhnt Wolfgang,
Holbourn Ann,
Andersen Nils
Publication year - 2020
Publication title -
paleoceanography and paleoclimatology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.927
H-Index - 127
eISSN - 2572-4525
pISSN - 2572-4517
DOI - 10.1029/2020pa003923
Subject(s) - monsoon , geology , stadial , oceanography , benthic zone , glacial period , climatology , precipitation , east asian monsoon , pleistocene , seawater , monsoon of south asia , deglaciation , mixed layer , circumpolar deep water , thermohaline circulation , paleontology , north atlantic deep water , geography , meteorology
We reconstructed the variability of the Earth's strongest hydrological system, the Indian monsoon, over the interval 6.24 to 4.91 Ma at International Ocean Discovery Program (IODP) Expedition 353 Site U1448 in the Andaman Sea. We integrated high‐resolution benthic and planktic foraminiferal carbon and oxygen isotopes with Mg/Ca measurements of the mixed layer foraminifer Trilobatus sacculifer to reconstruct the isotopic composition of seawater (δ 18 O sw ) and the gradient between planktic and benthic foraminiferal δ 13 C. A prominent increase in mixed layer temperatures of ~4°C occurred between 5.55 and 5.28 Ma, accompanied by a change from precession‐ to obliquity‐driven variability in planktic δ 18 O and δ 18 O sw . We suggest that an intensified cross‐equatorial transport of heat and moisture, paced by obliquity, led to increased summer monsoon precipitation during warm stages after 5.55 Ma. Transient cold stages were characterized by reduced mixed layer temperatures and summer monsoon failure, thus resembling late Pleistocene stadials. In contrast, an overall cooler background climate state with a strengthened biological pump prevailed prior to 5.55 Ma. These findings highlight the importance of internal feedback processes for the long‐term evolution of the Indian monsoon.