Millennial‐Scale Precipitation Variability in the Indo‐Pacific Region Over the Last 40 Kyr. Issue 2 (14th January 2023) - Yu, Zhaojie
Abstract: Deep atmospheric convection in the Indo‐Pacific Warm Pool (IPWP) represents a major source of heat and moisture, thereby affecting the global climate, but its past changes remain debated. Here, we present sub‐millennial clay mineralogy and elemental records spanning the last 40 Kyr from within the IPWP. From these data, we infer millennial‐scale fluctuations in precipitation, with generally lower precipitation during Heinrich Stadials 1–4, corresponding to El Niño‐like conditions. Higher precipitation coincided with the warm interstadials, accompanied by La Niña‐like conditions. Moreover, our record indicates the lowest precipitation occurred during the late Holocene, supporting the hypothesis of a stronger‐than‐modern Walker circulation during the Last Glacial Maximum. In combination with other proxy records and TraCE‐21 modeling results, we recognize a distinct spatial heterogeneity of precipitation within the IPWP, resulting from the dominant influences of the ENSO‐like system and migration of the Intertropical Convergence Zone in the eastern and western IPWP, respectively. Plain Language Summary: Tropical rainfall systems in the Indo‐Pacific Warm Pool (IPWP) play a significant role in transferring energy and moisture. However, their millennial‐scale variabilities in precipitation during the past remain poorly understood. Here, we provide sub‐millennial sediment mineralogy and elemental reconstructions spanning the last 40, 000 years from a sediment core in the IPWP. We infer that variability in precipitation induced by atmospheric convection in the IPWP is the main factor controlling the variability in our data through time. Hence, we interpret our records to reflect millennial‐scale fluctuations in precipitation, with lower precipitation during cool stadial periods and higher precipitation during warm interstadials. Such variability corresponds to the changing zonal state of the tropical Pacific atmosphere‐ocean system, in a pattern similar to the modern‐day. Additionally, our record indicates that precipitation was weaker during the late Holocene than during the Last Glacial Maximum (LGM), suggesting that the Pacific atmospheric zonal circulation was stronger during the LGM than today. Furthermore, a model‐data comparison reveals distinct spatial heterogeneity in the precipitation changes, with precipitation in the eastern IPWP (West Pacific) likely controlled mostly by the tropical Pacific atmosphere‐ocean system, whereas precipitation in the western IPWP (Indian Ocean) was driven by latitudinal movement of the Intertropical Convergence Zone. Key Points: We present sub‐millennial clay mineral and elemental records from the Indo‐Pacific Warm Pool spanning the last 40 Kyr Our records indicate higher precipitation during La Niña‐like conditions and lower precipitation during El Niño‐like conditions Different patterns and controls on precipitation variability between the eastern and western Indo‐Pacific regions are revealed