Winter air temperature during the Holocene optimum in the north-eastern part of the east European plain based on ice wedge stable isotope records

Early Holocene winter air temperatures have been reconstructed for the northeastern part of the East European Plain using stable isotope (δ18O and δ2H) records of syngenetic ice wedges. We show that ice wedges here actively grew synchronously with accumulation of peatlands in bogged and forested depressions between 10 and 8 cal ka BP, corresponding to the early Holocene Thermal Maximum. The slope of the δ2H-δ18O regression line is close to the global meteoric water line. This suggests the preservation of winter precipitation signal in the ice wedge with minor isotope transformation. The low range of stable isotope values in the ice wedge indicates quite stable winter climate conditions, favorable to ice wedge growth. Reconstructed mean winter air temperature was close to modern, but it is assumed that air temperature of the coldest winter month was lower and more stable than at present