4:30 PM - 4:45 PM
[MIS14-09] Westerly Jet variability over East Asia in response to AMOC reductions during past interglacial periods
Keywords:Westerly Jet, Interglacial periods, AMOC
The Westerly Jet, positioned along the Hadley Circulation, plays a critical role in contributing mid-latitude climate by regulating heat and moisture transport through its meandering path. Proxy records and numerical simulations suggest that repeated reductions in the Atlantic Meridional Overturning Circulation (AMOC) during the Last Glacial period influenced the Jet’s path by altering the intensity and latitudinal extent of the Hadley Cell (e.g. Nagashima et al., 2011; Lee et al. 2011). Considering the possible future AMOC reduction following the global warming (Rahmstorf 2024), investigating the Jet's response to AMOC reductions during the warmer interglacial periods is essential for improving predictions of future mid-latitude climate variability.
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 through a provenance analysis of Asian dust in Japan Sea sediments, core MD01-2407. This reconstruction utilized the electron spin resonance intensity of quartz in the sediments, reflecting the relative contribution of Asian dust from the Taklimakan and Gobi deserts, that is sensitive to the westerly jet path over East Asia (e.g. Nagashima et al. 2011). Our findings, combined with previously published data showing the Westerly Jet variation during the MI 1 (Nagashima et al., 2013), revealed southward shifts of the Westerly Jet in response to AMOC reductions during the interglacial periods recorded in the North Atlantic. Considering 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 valuable insights into potential precipitation changes in monsoon regions in response to the forthcoming AMOC weakening. We will also explore the ‘tipping element-like behavior’ of the Westerly Jet over East Asia in response to AMOC reductions, emphasizing the role of the Himalaya-Tibetan Plateau in constraining the Jet’s path. This topographic influence may create a threshold effect on the Jet’s trajectory, inducing climate feedbacks through interactions between the Westerly Jet and the Himalaya-Tibetan Plateau.
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 through a provenance analysis of Asian dust in Japan Sea sediments, core MD01-2407. This reconstruction utilized the electron spin resonance intensity of quartz in the sediments, reflecting the relative contribution of Asian dust from the Taklimakan and Gobi deserts, that is sensitive to the westerly jet path over East Asia (e.g. Nagashima et al. 2011). Our findings, combined with previously published data showing the Westerly Jet variation during the MI 1 (Nagashima et al., 2013), revealed southward shifts of the Westerly Jet in response to AMOC reductions during the interglacial periods recorded in the North Atlantic. Considering 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 valuable insights into potential precipitation changes in monsoon regions in response to the forthcoming AMOC weakening. We will also explore the ‘tipping element-like behavior’ of the Westerly Jet over East Asia in response to AMOC reductions, emphasizing the role of the Himalaya-Tibetan Plateau in constraining the Jet’s path. This topographic influence may create a threshold effect on the Jet’s trajectory, inducing climate feedbacks through interactions between the Westerly Jet and the Himalaya-Tibetan Plateau.