Divergent response of eastern China precipitation to the Pacific decadal oscillation during the last Interglacial

Abstract

Understanding the role of the Pacific Decadal Oscillation (PDO) during the Last Interglacial (LIG, ∼127 ka) may advance our knowledge on decadal climate variability in a warmer world. In this study, we investigate the PDO–precipitation relationship over eastern China during the LIG based on the NorESM2-LM, which shows the best performance in capturing the observed PDO pattern and the PDO–precipitation relationship among 12 models from the Paleoclimate Modelling Intercomparison Project Phase 4. Composite analysis shows that summer precipitation during the LIG is generally increased over eastern China in the positive PDO phases relative to the negative phases, which is different from the “drier-wetter-drier” triple pattern in the present day. The discrepant precipitation patterns between the LIG and preindustrial are caused by different responses of composite atmospheric circulations. Moreover, moisture budget analysis indicates that variations of vertical velocity over eastern China largely explain the PDO-linked precipitation patterns during both LIG and preindustrial, although the main causes for vertical motion changes are different across regions and periods based on the quasi-geostrophic ω equation. Additionally, these discrepancies in composite atmospheric circulations are largely linked to differences in PDO patterns and mean climate states between the LIG and preindustrial. Our results suggest a varying relationship between the PDO and precipitation over eastern China in a warmer-than-present world induced by Earth's orbit, which have important implications for PDO reconstructions during the LIG via the PDO-precipitation relationship reported here and shed light on decadal variability of precipitation as well as the associated decadal predictions in a future warmer world.