Holocene seasonal temperature reconstruction based on branched glycerol dialkyl glycerol tetraethers (brGDGTs) records from different regions in China

The patterns of Holocene temperature change can provide important insight for understanding the recent global warming and assessing future global climate change. However, the mismatch in Holocene mean annual temperature between proxy records and climate models remains controversial, which is likely caused by potential seasonal bias from the geological records. Here, 64 surface sediment samples are analyzed to examine the seasonal bias of brGDGTs reconstruction. Subsequently, we compile 23 brGDGT-based seasonal and annual temperature records from different regions in China and compare them with the TraCE-21 ka simulation results in the same geographical location. The linearly analysis shows a higher correlation between MBT′ 5me and MAF (mean temperature of months above freezing) than that of MAT (mean annual air temperatures), suggesting the reconstructed temperature based on brGDGTs from aquatic sources may be biased toward MAF. The regionally stacked results indicate that MAF in the Qinghai-Tibet Plateau and Northern China warmed from ~12 to 7 ka BP and then cooled thereafter, while an overall warming trend occurred in Southern China. These patterns of MAF change can be well reproduced by the model simulations. The summer and autumn temperature patterns during the Holocene in the Northern China are primarily driven by local insolation and modulated by ice sheets and greenhouse gas concentrations. The retreat of ice sheets in the early and middle Holocene, coupled with the increase in greenhouse gases, is considered the main driving factor for the long-term warming trend of the Holocene in southern China, whereas orbital-induced summer temperature change might be the major driving factor of MAF change in the Qinghai-Tibet Plateau. Our results suggest that the patterns of seasonal temperature change are basically matched between proxy records and climate models during the Holocene.