Hypersensitivity of glacial temperatures in Siberia

Abstract

Abstract. Climate change in Siberia is currently receiving a lot of attention as large permafrost-covered areas could provide a strong positive feedback to global warming through the release of carbon that has been sequestered there on glacial-interglacial time scales. Geological evidence and climate model experiments show that the Siberian region also played an exceptional role during glacial periods. The region that is currently known for its harsh cold climate did not experience major glaciations during the last ice age, including its severest stages around the Last Glacial Maximum (LGM). On the contrary, it is thought that glacial summer temperatures were comparable to present-day. We combine LGM experiments from the second and third phases of the Paleoclimate Modelling Intercomparison Project (PMIP2 and PMIP3) with sensitivity experiments with the Community Earth System Model (CESM). Together these climate model experiments reveal that the intermodel spread in LGM summer temperatures in Siberia is much larger than in any other region of the globe and suggest that temperatures in Siberia are highly susceptible to changes in the imposed glacial boundary conditions, the included feedbacks and processes, and to the model physics of the different components of the climate model. We find that changes in the large-scale atmospheric stationary wave pattern and associated northward heat transport drive strong local snow and vegetation feedbacks and that this combination explains the susceptibility of LGM summer temperatures in Siberia. This suggests that a small difference between two glacial periods in terms of climate, ice buildup or their respective evolution towards maximum glacial conditions, can lead to strongly divergent summer temperatures in Siberia, that are sufficiently strong to allow for the buildup of an ice sheet during some glacial periods, while during others, above-freezing summer temperatures will preclude a multi-year snow-pack from forming.

Rapid waxing and waning of Beringian ice sheet reconcile glacial climate records from around North Pacific

“…glaciogenic features mapped off the NE Siberian continental shelf (Niessen et al, 2013), a glacially scoured trough on the outer margin north of De Long Islands (O'Regan et al, 2017), and glacial deposits on the New Siberian Islands (Nikolskiy et al, 2017). Partly due to poor age controls, it remains highly controversial (Barr and Clark, 2012a) whether the glacial evidence points towards a pre-LGM ice sheet over NE Siberia- The concept of Laurentide-Eurasia-only ice sheets should be compatible with the full range of paleoclimate evidence if it is right, but a mounting number of paleoclimate reconstructions from around the North Pacific show conflicts to the concept (e.g., Meyer and Barr, 2017;Bakker et al, 2020). Therefore, in this study, we first review paleoclimate evidence from around the North Pacific, and then use climate and ice sheet modelling to investigate whether the conflicts can be solved with the Laurentide-Eurasia-only ice sheets, and whether an ice sheet over NE Siberia-Beringia is needed to reconcile the paleoclimate evidence.…”