Deglacial and Holocene precipitation seasonality on the central Tibetan Plateau

Abstract

Variations in precipitation seasonality have a profound impact on aspects of the climatic component, social activities and ecological processes. Reconstructing the precipitation seasonality during the deglaciation and Holocene, can improve our understanding of how and why precipitation seasonality changes under different climate scenarios. Here we develop an indicator of seasonal precipitation weight (growing season precipitation to annual precipitation) based on a modern pollen dataset for the central and western Tibetan Plateau (TP), which is further applied to a fossil pollen record spanning the last deglaciation and Holocene from the central TP to reconstruct long-term variations in seasonal precipitation weight. Our reconstruction result, combined with modelled data from a transient simulation, shows that changes in the precipitation seasonality associated with shifts in the atmospheric circulation systems are distinct from those in annual precipitation amount. Our results suggest that changes in the westerlies driven by the Atlantic meridional overturning circulation (AMOC) dominate the precipitation seasonality during the last deglaciation and the Indian summer monsoon (ISM) dominates mainly in the Holocene, and confirm the important moisture contributions of the westerlies to the early Holocene humid conditions.