Strengthened relationship between August Laptev Sea ice retreat and September precipitation in Central China since 2005

Abstract

Abstract The intensified interannual variability of September rainfall in Central China has led to increasingly frequent and devastating hydrological disasters over the past two decades. This study identifies the accelerated retreat of August Laptev Sea ice since 2005 as a critical, previously unrecognized precursor for September precipitation in Central China. Diagnostics show that post-2005 sea ice retreat and its heightened interannual variance substantially enhance local ice-ocean-atmosphere coupling compared with pre-2005. The resulting surface warming initiates a persistent “warm Siberia–cold North China” thermal dipole, which suppresses the meridional temperature gradient (MTG) over the Mongolian Plateau. This altered thermal gradient modulates transient eddy activity, driving an equatorward shift of the subtropical westerly jet through transient eddy–mean flow interaction, then strengthening the meridional secondary circulation. This configuration facilitates an anomalous anticyclone over the western North Pacific, with anomalous southwesterly flow on its western flank importing moisture across Central China’s southern boundary. Coupled with deep ascending motion, this process drives enhanced September rainfall. These findings underscore the evolving impact of Arctic cryospheric change on mid-latitude climate, providing valuable insights for seasonal forecasting and water resource management.