Spatial heterogeneity of hydroclimate variability across the mid-latitude Asia region during a Mid-Holocene event

The spatial pattern of hydroclimate variability across the arid/semiarid Asia, consisting of sub-regions dominated by mid-latitude westerlies and the Asian monsoon, remains elusive. Here we investigate potential hydroclimate heterogeneity during a mid-Holocene climate event by synthesizing 18 high-quality proxy records. The response ratios of proxy excursions show peak values at 5.08 and 4.92 ka, defining a possible centennial-scale event around 5.1-4.9 ka (the 5 ka event). Our analysis reveals a pronounced tripole pattern of hydroclimate anomalies during this event: dry conditions in West Asia (WA) and northern-central East Asia (NCEA), contrasting with wet conditions in arid central Asia (ACA). This ‘dry-wet-dry’ latitudinal pattern is supported by TraCE-21ka climate model simulations. We propose that this pattern was driven by internal climate variability. A negative phase of the North Atlantic Oscillation around 5 ka likely increased westerly jet stream waviness, causing a northward shift and drying in WA, and a southward shift with enhanced moisture in ACA. Concurrently, a southward-shifted Intertropical Convergence Zone and increased El Niño activity weakened the Asian summer monsoon, reducing precipitation in NCEA. These findings enhance our understanding of past hydroclimate variability and its drivers, offering insights into potential future spatial heterogeneity under warming scenarios.