Provenance of Asian Dust Delivered to the Philippine Sea and Its Transport Pathways: Isotopic and Mineralogical Evidences

Abstract:

Most dust studies using deep-sea sediment archives from the North Pacific have focused on understanding the mass flux variation of Asian dust in terms of long-term climate variability, but have not considered specific transport pathways or dust source regions (e.g., central/East Asian deserts versus northern Chinese deserts). To characterize the provenance and transport pathways of eolian dust deposited in the western tropical/subtropical Pacific, and to investigate changes over the late Quaternary, we used the clay mineral assemblage, together with the ¹⁴³Nd/¹⁴⁴Nd and ⁸⁷Sr/⁸⁶Sr composition of the inorganic silicate fractions of a deep-sea sediment core retrieved from the Palau-Kyushu Ridge in the Philippine Sea. The analyzed attributes of the core resemble those of dust from the central Asian deserts (CADs; e.g., the Taklimakan Desert) as in the North Central Pacific, but published aerosol data collected near the study site during winter/spring has the mineralogical signature of dust originating from the East Asian deserts (EADs; e.g., the Chinese Loess Plateau and nearby deserts). These data indicate that the relative contribution of EAD dust increases with the northeasterly surface winds associated with the East Asian Winter Monsoon (EAWM) during winter/spring, but the Prevailing Westerlies and Trade Winds that carry dust from the CADs have been the dominant transport agent for the last 600 kyr. The results of this study contradict the prevailing view that direct dust transport by the EAWM winds in spring dominates the annual flux of eolian dust in the northwest Pacific.