Step-wise shifted rainbelt throughout the early last deglaciation

Abstract

Millennial climate change since the last deglaciation have drawn much attention. Even though the role of northern hemisphere is much focused on, how the tropic performed remains disputed. Here based on Mg/Ca and δ18Osw local from planktonic foraminifera Globigerinoides ruber, sub-millennial scale hydroclimate record throughout the early last deglaciation is presented from the northern South China Sea, near the northern boundary of Intertropical Convergence Zone (ITCZ). Coupled with previous research, we speculate that rainbelt/ITCZ was located northerly from 19 to 18 ka, and migrated southward within two-steps during Heinrich 1 event. Northerly ITCZ during 19–18 ka was rendered by tropical warming since 19 ka through the Gill-Matsuno response, which strengthened Atlantic meridional overturning circulation, contributing to intense monsoon precipitation over east Asia, and dry conditions around the western Pacific. The subsequent two-steps ITCZ southward shift during Heinrich 1 was driven by weakened Atlantic meridional overturning circulation, which was produced by the lowering northern hemisphere ice-sheet at ∼16.2 ka. Step-wise shifted rainbelt/ITCZ documented from our record indicates multiple factors dominated sub-millennial scale climate change during the whole last deglaciation. We highlight the important roles of tropical warming and ocean circulation in initiating the last deglaciation and the subsequent climate change, respectively.