Northward extent of East Asian monsoon covaries with intensity on orbital and millennial timescales

TLDR

Past and future East Asian monsoon rainfall fluctuations in magnitude, rate, and extent are not well constrained. The study reconstructs late Pleistocene–Holocene EAM rainfall intensity from a well‑dated closed‑basin lake area record in northeastern China at the monsoon’s northwestern fringe. The lake record shows that EAM intensity and northern extent fluctuated rapidly on centennial scales, with early/middle Holocene lake levels 60 m higher—implying a two‑fold rainfall increase and ~400 km northward monsoon expansion—corroborated by cave isotope data, and that intensity and extent covary on orbital and millennial timescales, with the 5.5 ka BP wet‑to‑dry shift coinciding with a major Early Neolithic cultural collapse.

Abstract

The magnitude, rate, and extent of past and future East Asian monsoon (EAM) rainfall fluctuations remain unresolved. Here, late Pleistocene-Holocene EAM rainfall intensity is reconstructed using a well-dated northeastern China closed-basin lake area record located at the modern northwestern fringe of the EAM. The EAM intensity and northern extent alternated rapidly between wet and dry periods on time scales of centuries. Lake levels were 60 m higher than present during the early and middle Holocene, requiring a twofold increase in annual rainfall, which, based on modern rainfall distribution, requires a ∼400 km northward expansion/migration of the EAM. The lake record is highly correlated with both northern and southern Chinese cave deposit isotope records, supporting rainfall "intensity based" interpretations of these deposits as opposed to an alternative "water vapor sourcing" interpretation. These results indicate that EAM intensity and the northward extent covary on orbital and millennial timescales. The termination of wet conditions at 5.5 ka BP (∼35 m lake drop) triggered a large cultural collapse of Early Neolithic cultures in north China, and possibly promoted the emergence of complex societies of the Late Neolithic.