Carbon storage and dynamics in cryosphere: Progress and challenges

Climatic warming threatens to occurrence of cryosphere across the cold regions, which include glacier, permafrost, snow cover, and sea ice et al. Permafrost thaw has occurred during the last decades not only in Arctic regions, but also in the alpine regions. The potentially releasing large amount of organic carbon would further accelerate the global warming. Here we summarize the recent progress in the storage, source, composition, stabilization, emission of permafrost carbon in the Arctic and third pole regions. By combining the previous data syntheses and model estimation, we conclude that the SOC storage for the 0-300 cm in the Northern Circumpolar permafrost regions approximates to 985.8 ± 98.7 Pg and 23.5 ± 11.1 Pg C in the Qinghai-Tibet permafrost region.  The projection of ecosystem model shows that the carbon emission from the permafrost by warming is expected to reach up to 240 Pg C by 2100, with an average of 92 ± 17 Pg C. Finally, we also present some priorities on the permafrost carbon research including long-term and continuous observation to the carbon dynamics, improvement of the ecosystem model to reduce uncertainty of projection, and the application of advanced techniques such as machine-learning or deep learning, in order to present more accurate assessment to the carbon dynamics responding to forthcoming climatic warming in the future.