Combined high-and low-latitude forcing of orbital East Asian hydroclimate

Speleothem oxygen isotope records from China have provided the most detailed insights into the past Asian summer monsoon variability of any paleoclimate archive (“proxy”) to date in the past 640 ka, showing the dominance of the orbital precession rhythm. However, fundamental disagreement exists on what the oxygen isotope records represent in terms of the hydroclimate changes, in particular on the orbital scale. Based on the oxygen isotope records and other hydroclimate proxies from 15 speleothems at Haozhu Cave in central-eastern China, as well as the model simulations for the periods of Marine Isotope Stages 6 and 11, we show the orbital-scale ‘dipole’ hydroclimate in monsoonal eastern China, with wetter (drier) conditions in the central but drier (wet) conditions in the north when summer insolation was low (high) and East Asian summer monsoon was weak (strong). Of significance is the finding that the hydroclimate contrast in East China was greatly enhanced during glacial-interglacial transitions, with the wettest hydroclimate in the north but widespread drought in the central, when the heat content of both the global ocean and the Indo-Pacific Warm Pool upper ocean reached the maximum. We propose that the orbital-scale westerly jet transition affects the East Asian summer rainband position and thus the orbital hydroclimate pattern in eastern China, and the low latitude tropical Indo-Pacific ocean moisture transport amplifies the hydroclimate contrast during glacial-interglacial transitions