Intertropical Convergence Zone modulates Asian dust input to the low-latitude western Pacific during the late Neogene

Abstract

Asian dust is one of the primary components of detrital sediment in the tropical western Pacific. Whether low-latitude process influenced the Asian dust input to the low-latitude western Pacific during the late Neogene is still an open question. In this study, we analyzed the grain size composition of the detrital sediments and the radiogenic Sr and Nd isotopes of <4 um components in the International Ocean Discovery Program Site U1490 in the western Pacific warm pool. By using Weibull function fitting, we quantitatively separated fine-grained endmember components (EM2) from the detritus. The results indicate that EM2 primarily originated from dust of the northern Chinese deserts and western and central Chinese deserts, and is transported by the East Asian winter monsoon and westerlies during the late Neogene. The mode grain size of EM2 became significantly coarser at 7.2–4.8 Ma and 3.9–2.6 Ma, most likely due to the enhancement of the atmospheric circulation. The significant increase in EM2 content at 7.2–4.8 Ma and 3.9–2.6 Ma is temporally consistent with the records of Asian aridity and the southward shifts of the Intertropical Convergence Zone (ITCZ). We argue that the deposition of Asian dust in the low-latitude Pacific was influenced not only by the climate (e.g. atmospheric circulation and aridity) of Asian continent, but also was modulated by the paleolocation of the ITCZ. As the major rainfall zone in the low-latitude Pacific, ITCZ influenced the diffusion and deposition of Asian dust. During the late Neogene, the southward shift of the ITCZ forced Asian dust to spread southward and resulted in more Asian dust deposition in the low-latitude western Pacific. Our study demonstrates the important role of low-latitude process on the deposition of Asian dust in the western Pacific during the late Neogene.