IODP Site U1430 Asian Dust Size Records in the East (Japan) Sea Since the Early Pleistocene: The Role of Northwesterly Surface Winds and Upper Westerlies

The 2.3-million-year grain-size records of detrital components from IODP Site U1430 in the East (Japan) Sea illustrate the influence of East Asian Winter Monsoon variations on Asian dust transport and deposition. Dust transport was driven by two distinct wind systems: low-level northwesterly winter monsoon winds and upper-level westerlies. Using end-member (EM) modeling of grain-size distributions, five EMs were identified: fine-mode dust transported by upper-level westerlies (EM1), coarse-mode dust carried by northwesterly surface winds (EM2), and marine tephra components (EM3, EM4, EM5). After excluding marine tephra contributions, a refined dust-size distribution model was developed, focusing on EM1 and EM2. The cyclic patterns and amplitudes of dust-size variations at Site U1430 closely align with size records from the Chinese Loess Plateau (CLP), where sedimentation is predominantly influenced by northwesterly surface winds. This agreement suggests that dust deposition at Site U1430 was similarly controlled by the intensity of these winds, rather than upper-level westerlies. Additionally, variations in loess size across the CLP and modern dust observations indicate that vertical and lateral sorting processes during atmospheric transport contributed to the finer dust sizes recorded at Site U1430. These findings highlight the critical role of surface wind intensity and atmospheric sorting in shaping long-term dust deposition patterns in the East (Japan) Sea.