EGU2020-2027
https://doi.org/10.5194/egusphere-egu2020-2027
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Climate change impacts on CO2 and CH4 exchange in an Arctic polygonal tundra depend on changes in vegetation and drainage

Robert Grant
Robert Grant
  • Alberta, Renewable Resources, Edmonton, Canada (rgrant@ualberta.ca)

Model projections of CO2 and CH4 exchange in Arctic tundra during the next century diverge widely.  In this modelling study, we used ecosys to examine how climate change will affect CO2 and CH4 exchange through its effects on net primary productivity (NPP), heterotrophic respiration (Rh) and thereby on net ecosystem productivity (NEP) in landform features (troughs, rims, centers) of a coastal polygonal tundra landscape at Barrow AK. The model was shown to simulate diurnal and seasonal variation in CO2 and CH4 fluxes associated with those in air and soil temperatures (Ta and Ts) and soil water contents (q) under current climate in 2014 and 2015. During RCP 8.5 climate change from 2015 to 2085, rising Ta, atmospheric CO2 concentrations (Ca) and precipitation  (P) increased NPP from 50 – 150 g C m-2 y-1,  consistent with current biometric estimates, to 200 – 250 g C m-2 y-1, depending on feature elevation. Concurrent increases in Rh were slightly smaller, so that net CO2 exchange rose from values of -25 (net emission) to +50 (net uptake) g C m-2 y-1 to ones of -10 to +65 g C m-2 y-1, again depending on feature elevation. Large increases in Rh with thawing permafrost were not modelled. Increases in net CO2 uptake were largely offset by increases in CH4 emissions from 0 – 6 g C m-2 y-1 to 1 – 20 g C m-2 y-1, depending on feature elevation, reducing gains in NEP. Increases in CH4 emissions with climate change were mostly attributed to increases in Ta, but also to increases in Ca and P. These increases in net CO2 uptake and CH4 emissions were modelled with hydrological boundary conditions that were assumed not to change with climate.  Both these increases were smaller if boundary conditions were gradually altered to increase landscape drainage during model runs with climate change. The model was then applied to the entire permafrost zone of North America to project RCP 8.5 climate change effects on active layer depth and ecosystem productivity by 2100.  

How to cite: Grant, R.: Climate change impacts on CO2 and CH4 exchange in an Arctic polygonal tundra depend on changes in vegetation and drainage, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2027, https://doi.org/10.5194/egusphere-egu2020-2027, 2020

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