Synchronous change of temperature and moisture over the past 50 ka in subtropical southwest China as indicated by biomarker records in a crater lake

Over the past few decades, studies on the Indian Summer Monsoon (ISM) have been mainly based on paleo-marine records whilst the sparsity of land records limits our understanding of the ISM evolutionary process over continental landscapes. Here, we provide paleoclimate reconstructions based on n-alkanes and branched glycerol dialkyl glycerol tetraethers (brGDGTs) from a 50-ka lacustrine sediment core collected from Lake Tengchong Qinghai in southwestern subtropical China. Our results reveal that the botanical sources of sedimentary n-alkanes in this lake are mainly from aquatic macrophytes and terrestrial plants. The lake level evolution from the MIS 3 to the Holocene can be divided into four stages: high in the MIS 3, low in the LGM, high in last deglacial and low in mid and late Holocene. Our brGDGTs-based climate reconstructions indicate that the mean air temperature differences between the present-day and the LGM were up to about 3–4 °C. From MIS 3 to Holocene, there was a broadly and consistently synchronous trend between precipitation and air temperature in this ISM region. This is different from the asynchronous temperature and precipitation variations in the East Asian Summer Monsoon (EASM) regions in the period of last glacial termination. Our study shows that the climate in ISM regions was primarily driven by changes in June summer solar insolation at 30°N, and those glacial boundary conditions such as ice volume and sea surface temperature might also have affected the ISM.