Dr. Thian Gan, University of Alberta
When: 22nd March 2023, 11:00 am - 12:00pm
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.
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