Quantifying the contribution of modern Asian dust to the southern Yap trench and its southeastern region

Abstract

Dust plays a vital role in the Earth system, yet its contribution to the tropical West Pacific is still under-quantified. This gap limits the ability to assess the impacts of dust on the biogeochemical cycles in this region. In this study, we analyzed grain size distribution, the contents of major and trace elements in lithogenic components isolated by sequential leaching and in three grain-size fractions of surface sediments from the southern Yap Trench and its southeastern region in the tropical West Pacific, along with the characteristics of the climatological surface and subsurface current fields. Our results initially identified that the provenances of lithogenic components comprise not only Asian dust and volcanic material but also continental material from northern New Guinea rivers. Furthermore, the Rare Earth Elements-based dust fractions within the lithogenic components, derived from a binary mixing model and correction formula, range from 0.08 to 0.70, with an average of 0.39. This is highly consistent with the ⁸⁷Sr/⁸⁶Sr-based results and ratios of illite to smectite. In bulk sediment samples, the dust contents vary from 0.82% to 49.42%, with an average of 18.82%. Spatially, dust is enriched in the southern Yap Trench, West Caroline Basin, and Sorol Trough, while it was depleted on the West Caroline Ridge. This pattern may result from the potential redistribution induced by bottom current and/or dilution effect of authigenic smectite and carbonate on the West Caroline Ridge. Ultimately, although traditional geochemical methods and diagrams comparing illite/kaolinite and kaolinite/chlorite ratios, corrected for fluvial input, proved insufficient in distinguishing dust source regions and relevant transport media, dust aerosol analysis based on the MERRA-2 database suggests contributions from both Central Asian and East Asian deserts, with the former potentially playing a more prominent role. However, further studies are required to validate the aerosol-based method and these implications, as they are essential for reconstructing paleoatmospheric circulation from paleodust records. Hopefully, this study would contribute to a more comprehensive understanding of the global dust cycle and its interplay with biogeochemical cycles in abyssal trenches and basins.