Peat brGDGTs-based Holocene temperature history of the Altai Mountains in arid Central Asia

Abstract

Due to their effects on snow/ice melting in mountains and evaporation in basins, temperature variations are an important influence on the hydrological cycle and water resources in arid Central Asia (ACA). We present independently-dated peat brGDGTs-based MBT′/MBT′5ME records from an alpine Sahara sand peatland (SSP) in the southern Altai Mountains, in ACA. During the past ~11 kyr, the SSP MBT′ and MBT′5ME profiles exhibit consistently increasing trends and they are significantly positively correlated. Using a global peat-specific MBT′5ME-tempeature calibration, the long-term Holocene warming trend indicated by the quantitative SSP mean annual temperature (MATpeat) reconstruction is supported by the peat α-cellulose δ13C summer temperature record from the SSP, and by an independent peat α-cellulose δ18O winter temperature record from a nearby site (i.e. temporal validation). The increasing trends are also evident in Holocene peat MBT′ records from the Hongyuan (HY) peatland in the NE Tibetan Plateau, and in the Shuizhuyang (SZY) peatland in SE China. Notably, both the MBT′ data of the surface samples and the averaged MBT′ data of the Holocene peat cores are consistent with the modern spatial temperature gradient at the SSP, HY and SZY (i.e. spatial validation). This evidence demonstrates the temperature significance of peat MBT′/MBT′5ME records. The long-term Holocene warming trend indicated by the SSP MBT′/MBT′5ME records is supported by recently-acquired Holocene temperature records from the Eurasian continent. This trend is the opposite to the traditional viewpoint of a long-term Holocene cooling trend, and it indicates that more effort is needed to obtain a reliable Holocene temperature history.