Holocene warming in western continental Eurasia driven by glacial retreat and greenhouse forcing

Abstract

The global temperature evolution during the Holocene is poorly known. Whereas proxy data suggest that warm conditions prevailed in the Early to mid-Holocene with subsequent cooling, model reconstructions show long-term warming associated with ice-sheet retreat and rising greenhouse gas concentrations. One reason for this contradiction could be the under-representation of indicators for winter climate in current global proxy reconstructions. Here we present records of carbon and oxygen isotopes from two U–Th-dated stalagmites from Kinderlinskaya Cave in the southern Ural Mountains that document warming during the winter season from 11,700 years ago to the present. Our data are in line with the global Holocene temperature evolution reconstructed from transient model simulations. We interpret Eurasian winter warming during the Holocene as a response to the retreat of Northern Hemisphere ice sheets until about 7,000 years ago, and to rising atmospheric greenhouse gas concentrations and winter insolation thereafter. We attribute negative δ18O anomalies 11,000 and 8,200 years ago to enhanced meltwater forcing of North Atlantic Ocean circulation, and a rapid decline of δ13C during the Early Holocene with stabilization after about 10,000 years ago to afforestation at our study site. We conclude that winter climate dynamics dominated Holocene temperature evolution in the continental interior of Eurasia, in contrast to regions more proximal to the ocean. Models and proxy data diverge on the global temperature evolution of the Holocene, perhaps due to representation of the seasons. Isotopic analyses of stalagmites from the Ural Mountains suggest that winter climate dominated in the Eurasian interior.