Dominant obliquity forcing of northern Hemisphere westerly winds during the late Quaternary

As a crucial component of the Earth system, mineral dust in the atmosphere is interactively affected by climatic changes, however, its response to orbital forcing is still not fully understood. Here, we present a new high-resolution reconstruction of dust record in the Subarctic Pacific Ocean covering the past 190 kyr. Reconstructed relative abundance of hematite and goethite ratio shows dominating precessional fluctuation, which is inversely correlated with the East Asian speleothem records. Moreover, integrated dust flux reveals distinct periodic obliquity variations, that are out-of-phase with another record situated further south. Climate model simulations suggest that the observed precessional fluctuation of hematite and geothite ratio most likely reflects changes in the ariditiy in the dust source region, which is affected by the variations of the Northern Hemisphere summer monsoon. The periodic obliquity variations in dust flux, on the other hand, are linked to the meridional shifts in the northern Pacific westerly jet, which is regulated by the changes in meridional temperature gradient. Our findings further domonstrate that the westerlies are primarily modulated by the obliquity cycle rather than by CO₂-driven radiative forcing.