Westerly Jet southward shifts in response to Atlantic Meridional Overturning Circulation reductions during past interglacial periods

The Westerly Jet, locating northern boundary of the Hadley Circulation, plays a critical role in contributing mid-latitude climate by facilitating heat and moisture transport through its meandering path. Previous proxy records and numerical simulations have shown that the Jet’s path was altered in response to the repeated reduction events of the Atlantic Meridional Overturning Circulation (AMOC) during the Last Glacial period, through the modulation of Hadley Cell intensity and latitudinal position (e.g. Nagashima et al., 2011; Lee et al. 2011). Considering the possible future AMOC reduction following the global warming (Rahmstorf 2004), it is critically important to investigate the Jet's response to AMOC reduction during the warmer interglacial periods to enhance our understanding of future mid-latitude climate dynamics.

Recently, increasing evidence revealed AMOC reductions occurred even during interglacial periods, including MIS 1, 5e, 7e, 9e, and 11c (e.g. Galaasen et al. 2020). In this study, we reconstructed the Westerly Jet path over East Asia during MIS 5e and 11c through a provenance analysis of Asian dust in Japan Sea sediments (MD01-2407, KR02–06 D-GC-6, and KR07-12 PC-5, PC-8). This reconstruction utilized the electron spin resonance intensity of quartz, following Nagashima et al. (2007, 2011, 2013). Our findings, combined with previously published data (Nagashima et al., 2013), revealed southward shifts of the Westerly Jet in response to AMOC reductions during the warmer interglacial periods recorded in the North Atlantic. Given the strong relationship between changes in the Westerly Jet's path over East Asia and variations in East Asian summer monsoon precipitation, particularly its northwest-southeast spatial distribution within China, the observed southward shifts in the Westerly Jet provide important insights into potential precipitation changes in monsoon regions due to the forthcoming AMOC weakening in the near future.