EGU21-7222
https://doi.org/10.5194/egusphere-egu21-7222
EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Shrubs covered by snow in the high Arctic cool down permafrost in winter by thermal bridging through frozen branches

Florent Dominé1, Kevin Fourteau2, and Ghislain Picard3
Florent Dominé et al.
  • 1Université Laval and CNRS, Takuvik Joint International Laboratory, Quebec, Canada (florent.domine@takuvik.ulaval.ca)
  • 2Météo-France, CNRS, CNRM, Centre d’Études de la Neige, Grenoble, France
  • 3Université Grenoble Alpes, CNRS, IGE, Grenoble, France

Warming-induced shrub expansion on Arctic tundra is generally thought to warm up permafrost, as shrubs trap blowing snow and increase the thermal insulation effect of snow, limiting permafrost winter cooling. We have monitored the thermal regime of permafrost on Bylot Island, 73°N in the Canadian high Arctic at nearby herb tundra and shrub tundra sites. Once adjusted for differences in air temperature, we find that shrubs actually cool permafrost by 0.6°C over November-March 2019, despite a snowpack twice as insulating in shrubs. By simulating the rate of propagation of thermal perturbations and using finite element calculations, we show that heat conduction through frozen shrub branches have a winter cooling effect of 1.5°C which compensates the warming effect induced by the more insulating snow in shrubs. In spring shrub branches under snow absorb solar radiation and accelerate permafrost warming. Over the whole snow season, simulations indicate that heat and radiation transfer through shrub branches result in a 0.3°C cooling effect. This is contrary to many previous studies, which concluded to a warming effect, sometimes based on environmental manipulations that may perturb the natural environment. The impact of shrubs on the permafrost thermal regime may need to be re-evaluated.

How to cite: Dominé, F., Fourteau, K., and Picard, G.: Shrubs covered by snow in the high Arctic cool down permafrost in winter by thermal bridging through frozen branches, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7222, https://doi.org/10.5194/egusphere-egu21-7222, 2021.

Display materials

Display file

Comments on the display material

to access the discussion