North Atlantic forcing of Indian Winter Monsoon intensification: Evidence from Holocene sediments from the tropical Indian Ocean Island of Sri Lanka

Abstract

The teleconnection between the Asian monsoon system and North Atlantic forcing is an enduring prospect of the Earth’s climate. During the Holocene interstadial, the Indian summer monsoon showed asynchronous weakening links to ice rafting events documented in the North Atlantic region. However, the sensitivity of the Indian Winter Monsoon in response to North Atlantic cold spells is unclear due to a lack of compelling evidence. This study aims to extract the deglacial Indian Winter Monsoon signals using lithogenic tracers in coastal sediments and explore its association with the North Atlantic cooling episodes. A 5.1 m sediment core was retrieved from Pottuvil Lagoon in the southeastern coast of Sri Lanka, and the concentrations of K, Rb, Mg, Al, and Ti in 101 sub-sections were analysed using ICP-MS. The core- chronology was established by Bacon 2.2 age-depth modelling based on calibrated AMS ¹⁴C dates. The monsoon signal was reconstructed using element proxies and compared with the drift ice indices from the North Atlantic deep-sea sediments. Results revealed distinct phases of intense monsoon activity at 2553–2984 years BP, 3899–5021 years BP, and 5244–5507 years BP intervals with intermittent weak phases during 2253–2553, 2984–3899, and 5021–5244 years BP. The episodes of the intensified Indian Winter Monsoon coincided with Bond Events 2, 3, and 4, showing a strong coherence with the North Atlantic’s deglacial climate. Thus, on a millennial scale, North-Atlantic cooling has triggered intense winter monsoon conditions over the tropical Indian Ocean region from the mid to late Holocene. In comparison with regional monsoon archives, the Pottuvil winter monsoon record exhibits an anti-phase association with the Indian Summer Monsoon during Holocene ice-rafted debris events. The geochemical approach executed in this study could provide new insight into the millennial-scale pacing of the winter counterpart of the Indian monsoon links to climate extremes of high northern latitudes.