Millennial-scale hydrographic changes in the northwestern Pacific during marine isotope stage 19: Teleconnections with ice melt in the North Atlantic

Abstract

Marine isotope stage (MIS) 19 has been suggested as the best orbital analogue of the present interglacial period. Thus, its paleoenvironmental reconstruction will provide valuable information on future climate change, excluding anthropogenic impacts. The Kuroshio Current, the largest western boundary current in the northwestern Pacific, transports large amounts of heat and water poleward and strongly influences both East Asian and global climates. However, the responses of the Kuroshio Current to the variable intensity of the Atlantic meridional overturning circulation (AMOC) under this orbital configuration remain unknown. Here, we provide new centennial-scale resolution oxygen isotope (δ18O) records throughout MIS 19 using benthic, as well as subsurface and surface planktonic foraminifera from the Chiba composite section, a marine succession sequence in central Japan, to reconstruct detailed paleoceanographic variations in the northwestern Pacific and reveal the response of the Kuroshio Current to climate variability in the North Atlantic under this orbital configuration. The vertical water temperature structure and its gradient (ΔT) based on δ18O profiles elucidates the latitudinal oscillations of the Kuroshio Extension Front (KEF) on a millennial scale during the late MIS 19 and MIS 20–19 transition in association with AMOC disruption/reactivation due to freshwater discharges into the North Atlantic. The power spectra of the surface δ18O and ΔT show half-precession periodicity throughout MIS 19, which probably originated from equatorial insolation at equinoxes co-occurring with the orbital perihelion. This periodicity was especially strong during MIS 19c, during which paleoceanographic records from the North Atlantic show minor variations in the AMOC and freshwater discharge. Our results suggest that millennial-scale oceanographic variation and stability along the KEF under this orbital configuration are influenced by both North Atlantic climate variability and tropical insolation forcing.