Remote forcing of winter cooling in the Arabian Sea: Implications for the NE monsoon

The regional climate in the Asian subcontinent is highly influenced by the Southwest Monsoon (SWM) and Northeast Monsoon (NEM) during boreal summer and winter, respectively. Although the response of the SWM to the abrupt climatic changes recorded in the Greenland ice core records is well documented, the response of the NEM to the high latitude climate shifts is less well-understood due to the lack of winter monsoon records in the region. Here for the first time, we report the variability of winter cooling in the Arabian Sea and the associated NEM strength over the last similar to 37 kyr BP using seasonal sea surface temperatures (SST) derived by artificial neural network technique (ANN), based on planktonic foraminiferal species abundance data. Low winter SST anomalies in the northeastern Arabian Sea, a proxy for NEM strength, coincide with cold stadials (YD, H1, H2, H3) in the Greenland record and weakened SWM, implying that the cold conditions in Greenland strengthen the NEM and weaken the SWM on the Asian Subcontinent. Asynchrony between the NEM and SWM variability between similar to 37 and 9 kyr BP was driven by the southward shift of the Intertropical Convergence Zone (ITCZ) during colder phases of the Greenland stadials strengthening the NEM and weakening the SWM. This study implies that the migration of the ITCZ in the tropical Indian Ocean is controlled by the meridional atmospheric temperature gradient resulting from Atlantic Meridional Overturning Circulation (AMOC) changes.

Automated summary

This study reveals the variability of winter cooling in the Arabian Sea and the associated Northeast Monsoon strength over the past approximately 37 kyr BP. It demonstrates how cold conditions in Greenland strengthen the Northeast Monsoon and weaken the Southwest Monsoon in the Asian subcontinent, and suggests that the migration of the Intertropical Convergence Zone in the tropical Indian Ocean is controlled by the meridional atmospheric temperature gradient resulting from Atlantic Meridional Overturning Circulation changes.