Deciphering local and regional hydroclimate resolves contradicting evidence on the Asian monsoon evolution

The winter and summer monsoons in Southeast Asia are important but highly variable sources of rainfall. Current understanding of the winter monsoon is limited by conflicting proxy observations, resulting from the decoupling of regional atmospheric circulation patterns and local rainfall dynamics. These signals are difficult to decipher in paleoclimate reconstructions. Here, we present a winter monsoon speleothem record from Southeast Asia covering the Holocene and find that winter and summer rainfall changed synchronously, forced by changes in the Pacific and Indian Oceans. In contrast, regional atmospheric circulation shows an inverse relation between winter and summer controlled by seasonal insolation over the Northern Hemisphere. We show that disentangling the local and regional signal in paleoclimate reconstructions is crucial in understanding and projecting winter and summer monsoon variability in Southeast Asia. Distinguishing local hydrological, cave internal, and regional monsoon signals in speleothem records resolves disagreements among proxy reconstructions and illuminates the Holocene evolution of summer and winter monsoon in Southeast Asia.

Automated summary

The winter and summer monsoons in Southeast Asia are important sources of rainfall, but their variability is not well understood. Conflicting proxy observations have limited our understanding of the winter monsoon. However, a speleothem record from Southeast Asia has revealed that winter and summer rainfall changed simultaneously, driven by changes in the Pacific and Indian Oceans.