NSIDC Cryosphere Seminar
Climate warming Impact to Permafrost of Alaska and Western Arctic of Canada by Dr. Thian Yew Gan, University of Alberta
The Arctic, dominated by continuous and discontinuous permafrost, which occupies about 22 million km2 of exposed NH land areas, has been warming much faster than the rest of the world, commonly known as Arctic amplification. The active layer above the permafrost is a seasonally frozen ground above the permafrost table that is frozen in winter and thaws in summer. In the 2017 Arctic Boreal Vulnerability Experiment (ABoVE) airborne campaign, airborne L- and P- band SAR was used to acquire a dataset that provides estimates of seasonal active layer thickness, ALT and the vertical soil moisture profile for 51 sites across the ABoVE domain, including 39 sites in Alaska and 12 sites in Northwest Canada. We modeled the ALT of ABoVE dataset using thawing degree day (TDD) taken from the 2-m air temperature of ERA5 dataset, using ALT = K√TDD modified from the Stefan’s Equation, where K is calibrated for the 51 swaths with an excellent fit, R2 = 0.9783. We also obtained an excellent fit between ALT and the surface ground temperature of ERA5 at 3 levels, with R2 = 0.9719. Therefore, ALT can be reasonably estimated using either TDD based on 2-m air temperature, or near surface soil temperature. Arctic structures are vulnerable to the settlement of frozen ground caused by thawing of permafrost. The SSP (Shared-Social Economic Pathway) climate change scenarios, SSP 1-2.6, SSP 2-4.5 and SSP 5-8.5 of 7 global climate models (GCMs) statistically downscaled to about 25-km resolutions are used to project climate change impact to the ALT of the 51 swatches of the ABoVE dataset. Assuming ALT= K√TDD, the projected warming of UKESM1-0-LL GCM resulted in the largest projected ALT for the study site, up to about 0.7 m in 2080s under SSP5-8.5 climate scenarios. Given the mean observed ALT of the study site is about 0.48 m, it means that ALT of the 51 study sites is projected to increase by 0.074m to 0.217m, or between 15 and 45% by 2080s, which is expected to impact the Arctic infrastructure.
Short Bio: Thian Yew Gan is a professor of the University of Alberta, Edmonton, Canada since 1993, research ambassador of German Academic Exchange Service, a fellow of the American Society of Civil Engineers (ASCE), and a lead & contributing authors of the AR6-WGI of Intergovernmental Panel of Climate Change (IPCC). He has many innovative, multidisciplinary contributions to our understanding in hydrology, hydroclimatology, cryosphere, remote sensing of environment, and water resources management. He is a pioneer in research regarding climate change impact to water resources, and has developed many practical engineering tools/models for hydrologic forecasting, and innovative algorithms to retrieve large-scale spatial information from remotely sensed data, all essential for effective management of water resources. Dr. Gan has supervised 10 postdoctoral fellows, graduated 18 PhDs and over 30 master studentsDr Gan has published two books, “Global Cryosphere – Past, Present and Future”, 1st & 2nd Edition, Cambridge University Press, and over 160 refereed papers in various reputable, peer reviewed international journals