Climate changes revealed from the aeolian sediments in the Menyuan Basin, northeastern Qinghai-Tibet Plateau

Abstract

Aeolian sediments are a crucial component of Earth’s surface and serve as a significant terrestrial climate archive. The Menyuan Basin is a sensitive region for the interaction between the monsoons and Westerlies in the northeastern Qinghai-Tibet Plateau, where loess is extensively distributed, rendering it an ideal area for investigating climatic processes. In this study, climate changes in the Menyuan Basin since 40 ka are reconstructed using proxy records and luminescence dating obtained from the Yahecun profile. Our results show that the Menyuan Basin experienced a dry and cold climate from 40 to 16 ka, a continuous increase in moisture and temperature from 16 to 4.4 ka, and a relatively mild climate since 4.4 ka. The temperature variations in the Menyuan Basin are primarily driven by solar insolation; after 6 ka, the increase in the greenhouse gas concentrations contributed to higher temperatures. Precipitation in the region is governed by changes in the Westerlies and monsoons. During the glacial period, the summer monsoon weakened, and the transport of westerly water vapor decreased, resulting in reduced precipitation in the Menyuan Basin. Following the glacial period, an intensified summer monsoon and increased westerly water vapor transport collectively led to heightened precipitation. After 5 ka, the strengthening of the Westerlies likely sustained high precipitation in the Menyuan Basin. The intensity of winter monsoons in the Menyuan Basin is influenced by high-latitude insolation, with reduced high-latitude insolation after 6 ka leading to enhanced winter monsoons.