Zonal Variation of the Westly Jet and Asian Dust Transport Path to the Sea of Japan in Response to the Glacial-Interglacial Cycle.
Supervisors: Paul Wilson, Chuang Xuan (NOCS)
The Westerly Jet (WJ) and the East Asian Winter Monsoon (EAWM) are crucial components of Earth’s climate system, substantially affecting billions of people in East Asia. Marine sediments preserve constant and well-dated aeolian dust records, sensitive to changes in the wind regime in East Asia. Using radiogenic isotopes (87Sr/86Sr and εNd(0)), together with grain size analysis, dust transport from northern and western China to the Sea of Japan over the past 190 kyr was investigated in our study to reconstruct aeolian dust history from a sediment core U1424 in the southern part of Sea of Japan (12°30 °N, 134°60 °E).

Our results show that the median grain size correlates well with the glacial-interglacial cycle, implying the dominance of aeolian dust during the glacial period and the dominance of riverine sediments during the interglacial period. Our Sr-Nd isotope results revealed a mixture of finer riverine sediments (i.e., Japanese rivers and Yangtze River) and coarser wind-blown aeolian dust (i.e., Taklamakan Desert and Northern Chinese deserts, namely Gobi Desert, Orqin Sandy Land, and Horqin Sandy Land). During the glacial period (especially the glacial maximum), the intensified WJ, with its main axis located at the southern boundary of the Tibet Plateau, transported more dust from Taklamakan Desert all year around. While the WJ did not move northward or move very late after spring, the dust from Northern Chinese deserts activated by the EAWM during spring did not get lifted to the WJ in high altitudes. During the interglacial-glacial transition, The WJ moved northward with the zonal wind domain covering Northern Chinese deserts. The simultaneous occurrence of the EAWM and the WJ jointly brought more dust from Northern Chinese deserts during spring. During the interglacial period (especially the interglacial maximum), the WJ moved further northward and mainly transported dust from Northern Chinese deserts during spring and summer.

Our results clearly show the zonal shift of the WJ in response to the glacial-interglacial cycles. However, it remains unclear if the zonal movement of the WJ is also affected by the stadial-interstadial cycle due to limited data for Sr-Nd isotope signatures and grain sizes. Also, Other radiogenic isotope analysis (e.g., Pb) should be utilized in the future to differentiate the dust from Northern China deserts and the terrigenous materials from Japanese rivers.