Millennial variability in intermediate ocean circulation and Indian monsoonal weathering inputs during the last deglaciation and Holocene

• Published in: Geophysical Research Letters
• Main Authors: Yu, Zhaojie, Colin, Christophe, Wilson, David J., Bayon, Germain, Song, Zehua, Sepulcre, Sophie, Dapoigny, Arnaud, Li, Yuanlong, Wan, Shiming
• Format: Article in Journal/Newspaper
• Language: English
• Published: American Geophysical Union (AGU) 2022
• Subjects: neodymium (Nd) isotope; Indian Summer Monsoon; Antarctic Intermediate Water; Antarctic; Southern Ocean; Indian; Antarc*
• Online Access: https://archimer.ifremer.fr/doc/00800/91222/96970.pdf; https://archimer.ifremer.fr/doc/00800/91222/96971.pdf; https://doi.org/10.1029/2022GL100003; https://archimer.ifremer.fr/doc/00800/91222/

The relationship between ocean circulation and monsoon systems over orbital to sub-millennial timescales is a crucial but poorly-constrained component of the climate system. Here, using foraminiferal and detrital neodymium (Nd) isotope records from the intermediate-depth northern Indian Ocean, we provide new evidence revealing that both monsoon-driven weathering inputs and water mass advection from the Southern Ocean influenced past seawater Nd isotope changes in this region. Our results suggest that Indian Summer Monsoon weakening coincided with enhanced northward Antarctic Intermediate Water (AAIW) advection during the last deglaciation, reflecting a strong interhemispheric coupling. In contrast, the Early Holocene was characterised by enhanced monsoon strength but persistently strong AAIW inflow, indicating a relationship in the opposite sense. These differing interhemispheric relationships indicate asynchronous changes in the global atmosphere – ocean – climate system, and may represent a previously unrecognised component of the ocean-atmosphere reorganization during the deglacial to Holocene transition. Key Points We present a 17 kyr record of foraminiferal Nd isotopes from the intermediate-depth northern Indian Ocean with a resolution of ∼200 years Both regional Himalayan weathering inputs and intermediate water advection from the Southern Ocean influenced the record Different interhemispheric relationships are revealed between AAIW and the ISM during the last deglaciation compared to the Early Holocene Plain Language Summary Deciphering the interactions between processes in the Northern and Southern hemispheres is crucial for understanding the mechanisms of paleoclimate change, and therefore for predicting future climate evolution. Resolving the nature of such interactions requires high-resolution datasets from key components of the system. To this end, we present a new intermediate-depth foraminiferal neodymium (Nd) isotope record from the Indian Ocean covering the last 17,000 years at an unprecedented ...