Temperature variability revealed by lacustrine brGDGTs in northeastern China since the Last Glacial Maximum

Reconstructing temperature and monsoon variability are important for comprehensive understanding of past climate changes in the Asian summer monsoon (ASM) region. Although changes in monsoon intensity and monsoon rainfall since the Last Glacial Maximum (LGM) have been extensively studied from various archives and proxies, the variability of terrestrial temperature changes in the ASM region is still poorly constrained, largely due to the lack of quantitative paleotemperature reconstructions in the northern ASM region. Here, we report a quantitative mean growing-season temperature (May–September, Tgrow) record for the northmost ASM region over the past ∼28.1 ka, based on the distribution of branched glycerol dialkyl glycerol tetraethers (brGDGTs) in sediments from a small alpine lake in northeastern China. Our record shows an overall 7 °C deglacial warming from the termination of LGM to early Holocene, probably driven by the rising local growing-season insolation, the increasing atmospheric greenhouse gases, and the retreating ice-sheets. During the Holocene, our data display a gradual cooling trend of 1 °C, strongly influenced by the decreasing local growing-season insolation, but offset by the gradual increasing atmospheric greenhouse gases and the retreating ice-sheets to some extent. Within the Heinrich Stadial 1 (H1) interval, our record reveals a detailed feature with a large initial cooling and then a gradual warming in the northern ASM region, which differs to the persistent warming trend driven by atmospheric greenhouse gases in the southern ASM region, likely suggesting a stronger influence of Atlantic Meridional Overturning Circulation (AMOC) on temperature changes in the northern ASM region. Our results demonstrate a spatially heterogeneous in temperature variability between the northern and southern ASM region, in particular over the pronounced H1 cold interval during the last deglaciation.