Changes in the relationship between temperature and precipitation during the Holocene recorded by the sediments of Yangying Co, eastern Tibetan Plateau

Abstract

The Indian summer monsoon (ISM) is an important component of the Asian monsoon system. It transports moisture and heat from the ocean to mid- and low-latitude regions, which influence their climate and ecology. Under the influence of the Asian summer monsoon, temperature and precipitation in East Asia vary synchronously on the seasonal scale; however, this relationship was decoupled on the decadal scale over the past century, and on millennial or even longer time scales. In the context of the “Holocene temperature conundrum” and seasonal temperature reconstructions, the relationship between temperature and precipitation variations in the ISM region during the Holocene has been found to be increasingly complex. This study focuses on Yangying Co on Haizi Mountain, on the southeastern Tibetan Plateau. We obtained a high-quality, 475-cm-long, continuous sediment core (Yangying Co 2022B) from the lake center, which was dated using analyses of ¹³⁷Cs, ²¹⁰Pb, and AMS ¹⁴C. After evaluating the carbon reservoir effect, a reliable chronology was established for this core since 15 ka (1 ka = 1000 years). Sedimentological proxies (grain size) and geochemical proxies (XRF elements, TOC, TN, organic matter content) were used to reconstruct the history of glacier activity during the last deglaciation, and temperature and precipitation changes during the Holocene. The changes in TOC, TN, organic matter content, and Br (reflecting biomass variations) reveal a gradual increase in biomass in the Yangying Co region during the early Holocene, which reached a maximum during the middle Holocene and then decreased. The biomass is primarily controlled by summer temperature changes, and our Holocene summer temperature record shows a warming–thermal maximum–cooling temporal pattern. The gradual decrease in PC1 of scanning XRF data and in mean grain size during the Holocene indicate a weakening of the ISM. Influenced by cloud cover, dust flux, volcanic activity, and snow/ice albedo, the precipitation and summer temperature in the ISM region of the Tibetan Plateau were decoupled during the early Holocene (11.6–6 cal kyr BP). However, after ∼6 cal kyr BP, both precipitation and summer temperature decreased, possibly influenced by the decreasing Northern Hemisphere summer insolation. Our findings contribute to an improved understanding of current and future regional and global climate changes.