EGU2020-10837
https://doi.org/10.5194/egusphere-egu2020-10837
EGU General Assembly 2020
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Does shrubs growth in the high-Arctic lead to permafrost warming?

Florent Domine, Georg Lackner, Maria Belke-Brea, Denis Sarrrazin, and Daniel Nadeau
Florent Domine et al.
  • Université Laval and CNRS, Takuvik Joint International Laboratory, Quebec, Canada (florent.domine@gmail.com)

With climate warming shrubs can grow on high-Arctic tundra. This impacts many terms of the energy budget, resulting in a modification of the permafrost thermal regime. The summer surface albedo is decreased. The winter surface albedo is decreased because shrubs protrude above the snow. Winter conductive fluxes through the snow are reduced because shrubs trap snow, increasing snow depth. Shrubs also favor both snow melt in fall and spring and depth hoar formation in fall and winter, and both these factors affect snow thermal conductivity. Soil thermal properties may also be affected because of increased moisture.  We have measured many terms of the energy budget at Bylot Island, 73°N, Canada, at a herb tundra site and in a nearby large willow shrub patch. Monitored variables include radiation, snow and soil thermal conductivity and standard atmospheric variables. We observe that soil temperature at 15 cm depth is 1.5°C warmer under shrubs on a yearly average. The energetics of both sites are simulated using SurfexV8 including the detailed snow model Crocus. Combining observations and simulations indicates that the increased soil moisture under shrubs, by delaying  freezing by one month in fall, is an important factor in winter soil warming. Summer temperature is also markedly warmer under shrubs because of lower albedo and because the shrub understory is less insulating than on herb, which facilitates warming. These results show that investigating shrub impact using manipulations such as shrub removal is questionable because it does not restore pre-shrub understory and moisture.

How to cite: Domine, F., Lackner, G., Belke-Brea, M., Sarrrazin, D., and Nadeau, D.: Does shrubs growth in the high-Arctic lead to permafrost warming?, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10837, https://doi.org/10.5194/egusphere-egu2020-10837, 2020.

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