Westerly jet waviness modulates mid-latitude hydroclimate variability

The mid-latitude ecological environment is highly vulnerable, and increasing hydroclimate variability poses a significant threat to it. However, the mechanisms driving this variability remain unclear due to short observational records and climate model biases. Here, we present a sub-millennial resolution precipitation record spanning the past ~5.7 million years (Myr), derived from a 300.8-meter fluvio-lacustrine sediment core in mid-latitude East Asia (northern China). Our results reveal a persistent influence of the westerly jet on mid-latitude precipitation since the Pliocene, as well as a marked reduction in mid-latitude precipitation variability alongside amplified low-latitude variability after ~3 million years ago (Ma). Based on idealized sensitivity simulations, we attribute the amplified mid-latitude precipitation variability before ~3 Ma to enhanced westerly jet waviness driven by Arctic warming. Given projected increases in jet waviness under future global warming, we predict more frequent hydroclimate extremes in mid-latitude regions. This study provides robust evidence that Arctic warming affects precipitation variability in the mid-latitudes by modulating westerly waviness. Under global warming, extreme precipitation events in midlatitude regions will become more frequent.