Orbital Controls on North Pacific Dust Flux During the Late Quaternary

Airborne mineral dust is sensitive to climatic changes, but its response to orbital forcing is still not fully understood. Here, we present a reconstruction of dust input to the Subarctic Pacific Ocean covering the past 190 kyr. The dust composition record is indicative of source moisture conditions, which were dominated by precessional variations. In contrast, the dust flux record is dominated by obliquity variations and displays an out-of-phase relationship with a dust record from the mid-latitude North Pacific Ocean. Climate model simulations suggest precession likely drove changes in the aridity and extent of dust source regions. Additionally, the obliquity variations in dust flux can be explained by meridional shifts in the North Pacific westerly jet, driven by changes in the meridional atmospheric temperature gradient. Overall, our findings suggest that North Pacific dust input was primarily modulated by orbital-controlled source aridity and the strength and position of the westerly winds. Glacial-interglacial climate variations can affect dust transport to the ocean, but the controls on past dust fluxes to the North Pacific Ocean remain poorly constrained. This region is important because fertilization of phytoplankton growth by dust-borne iron may have contributed to lower glacial atmospheric CO2, and dust records could also constrain the past dynamics of the North Pacific westerly winds. Here, we highlight the dominance of obliquity cycles in modulating latitudinal shifts of the westerly winds and, in turn, dust inputs. In contrast, precession regulates the aridity of the dust source regions, which determines both dust emission rates and composition. Such orbital-scale fluctuations in the dust flux could influence ocean-atmosphere interactions in the middle and high northern latitudes, with implications for global atmospheric circulation and ocean carbon storage. Moisture availability in Asian dust source regions to the North Pacific Ocean were controlled by precession North Pacific dust flux reveals dominant obliquity variations, but is out-of-phase at different latitudes The westerlies in the Northern Hemisphere were primarily modulated by obliquity cycles in the late Pleistocene