Long-term winter/summer warming trends during the Holocene revealed by α-cellulose δ18O/δ13C records from an alpine peat core from central Asia

Abstract

Based on previously reported monitoring results from the alpine Sahara sand peatland (SSP) in the southern Altai Mountains, and modern observational δ18Op data from the Altai area, the new SSP peat α-cellulose δ18O (δ18Ocell) record spanning the last ∼11,000 years is determined to be an indicator of winter temperature. The record shows a long-term winter warming trend during the Holocene. Therefore, possibly for the first time, the SSP δ18Ocell record, combined with the reported SSP α-cellulose δ13C (δ13Ccell) record from the same peat core and supported by an independent modern-process study, provides records of Holocene winter and summer temperature. These signals demonstrate robust long-term winter/summer warming trends during the Holocene that are supported by independent records from nearby sites. Comparison of the SSP Holocene temperature records with those of winter/summer insolation and GHG (atmospheric greenhouse gas) forcing demonstrates a close link between temperature and insolation (a natural factor) prior to ∼5 cal kyr BP (1 kyr = 1000 years; BP = before present, where “present” is defined as AD 1950). However, there may be a close link between increased GHG forcing (a possible anthropogenic factor) and increased temperature after ∼5 cal kyr BP. We emphasize that, given the scarcity of high-quality, well-dated Holocene temperature records, the possible link between GHG forcing and temperature since the mid-Holocene needs to be further investigated. Thus we conclude that an increased number of reliable Holocene temperature records from other regions are urgently needed in order to determine the spatial extent (regional or global) of the Holocene warming trend.