Instability of Northeast Siberian ice sheet during glacials

Abstract. It has been widely believed that Northeast (NE) Siberia remained ice-free during most Pleistocene Northern Hemisphere (NH) glaciations, while ice sheets extended gradually across North America and Northwest (NW) Eurasia. However, recent fieldwork has provided robust evidence of ice sheets occupying the shallow continental shelf of the East Siberian Sea during several Pleistocene glaciations. The debate surrounding the existence and history of this enigmatic NE Siberian ice sheet highlights fundamental gaps in our current understanding of the mechanisms of glacial climate evolution. Here, we combine climate and ice sheet simulations to demonstrate how ice-vegetation-atmosphere-ocean dynamics can lead to two ice sheet configurations: the well-known Laurentide-Eurasian configuration with large ice sheets over North America and NW Eurasia, and a circum-Arctic configuration with large ice sheets over NE Siberia and the Canadian Rockies. Compared to the Laurentide-Eurasian configuration, formation of the circum-Arctic configuration can occur with an atmospheric stationary wave pattern similar to today's. Once the circum-Arctic configuration is established, it amplifies atmospheric stationary waves, leading to surface warming in the North Pacific, ablation of the NE Siberian ice sheet, and ultimately a swing to the Laurentide-Eurasian configuration. Our simulations highlight the complexity of glacial climates, and may hint towards potential mechanisms for interglacial-glacial transitions.