Legacy of Northern Hemisphere deglaciation on Tropical Rainbelt Migration during the Early Last Interglacial Period

During the penultimate deglaciation, which largely coincided with Heinrich Stadial 11 (HS-11, ~136-129 ka), meltwater pulses cooled the North Atlantic and weakened the Atlantic Meridional Overturning Circulation (AMOC), driving a southward shift of the Intertropical Convergence Zone (ITCZ) and arid conditions in northern South America. Although deglacial effects persisted for several millennia into the subsequent Last Interglacial period (LIG, ~129-115 ka), the response of the ITCZ to this transitional climate state remains poorly constrained. Here, we present paleoenvironmental records from a marine sediment core north of the Orinoco River delta, where runoff-sensitive proxies track northern South American rainfall and Atlantic ITCZ migration, and benthic δ¹³C records indicate AMOC strength. Our records show a gradual increase in precipitation during the early LIG, indicating a progressive northward migration of the ITCZ. Notably, the onset of peak wet conditions at 126.5±1 ka coincides with stabilized benthic δ¹³C values, consistent with the re-establishment of a fully developed interglacial AMOC. This temporal alignment suggests that the lingering effects of the penultimate deglaciation, such as gradual cessation of freshwater influence, subpolar North Atlantic SST warming and AMOC recovery, played an important role in shaping tropical hydroclimate during the first 4 millennia of the LIG, and should be incorporated in climate models.