Dipolar hydroclimate pattern changes in southwest China during the last deglaciation

Deciphering the driving forces behind spatial heterogeneity of regional hydroclimate changes is significant for developing strategies for water management. This study presents speleothem δ¹⁸O, δ¹³C and Mg/Ca records spanning the last deglaciation from Yingpan Cave, northeastern Yunnan in southwestern China. Speleothem δ¹³C and Mg/Ca indicate a gradual drying trend in northeastern Yunnan, aligning well with the variations in central China but contrasting with those of central-southern Yunnan. We propose that a decreased zonal sea surface temperature (SST) gradient in tropical Pacific (El Niño-like) shifted the West Pacific Subtropical High (WPSH) southwestward, leading to wetter conditions in northeastern Yunnan. Meanwhile, decreased precipitation in central-southern Yunnan was driven by weakened Indian summer monsoon rainfall associated with El Niño-like conditions, creating a dipolar hydrological pattern in Southwest China. Our results indicate that the spatial heterogeneity of hydroclimate can be modulated by the same triggers but have different processes and mechanisms and hence responses.