Tibetan Plateau Precipitation Modulated by the Periodically Coupled Westerlies and Asian Monsoon

Knowledge of decadal‐centennial‐scale precipitation cycles is important for predicting the status of water resources and thus food security in the region influenced by the “Asian Water Tower” (the Tibetan Plateau, TP). However, the drivers of these precipitation cycles in the TP remain unclear. Here we present a 1,656‐years (5‐years‐resolution) mean annual precipitation record reconstructed by fossil pollen assemblages from the annually laminated sediments of a lake in the TP interior. The record reveals three dominant cycles, with lengths of ∼200‐, ∼88‐, and ∼60‐years, associated with changes in the Westerlies and the Asian monsoon. These precipitation cycles suggest that the current high precipitation in the TP interior results from the superposition of cyclic highs in precipitation, and this trend may continue for the next several decades. Plain Language Summary Humidification resulting from increased precipitation over the Tibetan Plateau interior has attracted widespread because although it improves the ecological environment but it also threatens the security of the Qinghai‐Tibet Railway. Understanding the past behavior and mechanisms of precipitation variations over the Tibetan Plateau interior aids in the prediction of future water resource availability. We present a reconstruction of mean annual precipitation, derived from the pollen assemblages deposited in the annually laminated sediments of the Kusai Lake. The precipitation record exhibits three significant multidecadal‐centennial cycles; the ∼200‐years cycle is associated with the Westerlies and the ∼88‐years and ∼60‐years cycles are linked with the Asian monsoon. The superposition of high phases of cyclic precipitation results in the current wetting trend in the Tibetan Plateau interior. Key Points Precipitation reconstructed by lacustrine pollen assemblages from the Tibetan Plateau interior reveals three decadal‐centennial oscillations The decadal and centennial cycles are closely related to the Westerlies and the Asian Monsoon, respectively Superimposition of cyclic precipitation highs may have been factors in the current regional wetting trend