A 2000-Year reconstruction of Indo-Pacific hydroclimate variability inferred from water isotope records

Abstract

In an effort to better understand Indo-Pacific hydroclimate variability over the past two millennia, which plays a central role in global climate dynamics, this study reconstructs regional hydroclimate patterns using a multi-proxy, ensemble-based framework combined with Standard, Kernel, and Wavelet Principal Component Analysis (PCA) methods. The reconstruction enables assessment of hydroclimate relationships with internal ocean-atmosphere dynamics and external forcings. Analyses reveal that pre-1550 CE hydroclimate variability was characterised by weak and inconsistent associations with major climate drivers, suggesting a dominant role for internal variability, compounded by chronological uncertainties and lower proxy coverage. In contrast, post-1550 CE variability exhibits stronger links to both internal and external forcings, with a major shift after 1850 CE highlighting increased sensitivity to internal ocean-atmosphere modes. The reconstruction also demonstrates that major volcanic eruptions induced short-lived but coherent hydroclimate anomalies. Collectively, these findings underscore a transition from predominantly internal variability driving Indo-Pacific hydroclimate during the early Common Era to increasing sensitivity to both external forcings and internal climate modes during the industrial era.