Paleotemperature variability in central China during the last 13 ka recorded by a novel microbial lipid proxy in the Dajiuhu peat deposit

The Asian summer monsoon is a very important climatic component affecting the land ecosystem on the eastern Asian continent. Here we assess microbe-derived lipid biomarker evidence from a well-dated peat core from Dajiuhu to reconstruct paleotemperature changes in central China through the last 13 ka. The branched fatty alcohol ratio BNA 15 , which is defined as the relative contribution of branched C15 fatty alcohols over their straight-chain homolog, shows a positive correlation with air temperature ( R= 0.83, n=11, p<0.001) in an altitude transect at Shennongjia Mountain, central China. This correspondence suggests that the microbial activities associated with branched fatty alcohol synthesis are sensitive to differences in temperature. The BNA 15 sequence in the Dajiuhu peat deposit shows a trend similar to the paleotemperature record derived from pollen results over the last 13 ka, further supporting that BNA 15 is a sensitive proxy of paleotemperature. Absolute temperatures estimated from BNA 15 values of modern surface peats are about 3–4°C lower than the modern annual mean air temperature in the peatland, which may result from the influences of factors other than temperature or from the different microbial communities in the mountain soils used to calibrate the BNA 15 acidic peats. Fluctuations in the continuous 13 ka BNA 15 -derived record of relative temperature change from the Dajiuhu peat core imply that solar activity is the dominant cause for most cold events at multicentennial to submillennial timescales.