East Asia northeastern monsoon variability over the past two millennia

East Asia northeastern monsoon (EANM) is the downstream component of East Asia winter monsoon (EAWM) that influences the socio-economic activity of billions of people. Most detailed variations of past East Asia summer monsoon (EASM) have been reconstructed based on rain-bearing signatures retrieved by highly resolved speleothems, yet EAWM has proved difficult to reconstruct because of no such hydrological feature. Here we present a 2,000-year, annually resolved multi-proxy record of EANM from the southern Okinawa Trough. The record shows pronounced multi-centennial shifts in northeastern monsoon strength that were coupled with high northern temperature and tropical Walker Circulation. These couplings are best explained by the synchronization of cooling/warming northern temperature and enhancing/weakening Walker Circulation. Our findings, together with EASM records, highlight the likelihood that multi-centennial East Asia monsoon variations were not only forced by high northern latitude climate via meridional migration of tropical Indian Ocean westerlies and Pacific easterlies, but modulated by low tropical Walker Circulation through zonal migration of tropical Pacific easterlies as well.

Inter-annual precipitation variations in northeastern Taiwan are tightly linked to the El Niño-Southern Oscillation (ENSO), with more flooding during La Niña and droughts in El Niño years. Here we report evidence from an annually resolved marine sediment record for multi-centennial modulation of ENSO-related precipitation variability by global temperature.