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- Title
Spatial variability of CO<sub>2</sub> uptake in polygonal tundra - large overestimations by the conventional eddy covariance method.
- Authors
Pirk, Norbert; Sievers, Jakob; Mertes, Jordan; Parmentier, Frans-Jan W.; Mastepanov, Mikhail; Christensen, Torben R.
- Abstract
The large spatial variability in Arctic tundra complicates the representative assessment of CO2 budgets. Accurate measurements of these heterogeneous landscapes are, however, essential to understand their vulnerability to climate change. We surveyed a polygonal tundra lowland on Svalbard with a UAV, mapping ice-wedge morphology to complement eddy covariance (EC) flux measurements of CO2. The analysis of spectral distributions showed that conventional EC methods do not accurately capture the turbulent CO2 exchange with the spatially heterogeneous surface which typically features small flux magnitudes. Non-local (low frequency) flux contributions were especially pronounced during snowmelt and introduced a bias to the annual CO2 budget of -46 gC m-2 in conventional methods. Our improved flux calculations with the ogive optimization method indicated that the site was a sink for CO2 of -82 gC m-2 in 2015 and due to differences in light-use efficiency, wetter areas with low-centered polygons sequestered 47% more CO2 than drier areas with flat-centered polygons. While Svalbard has experienced a strong increase in mean annual air temperature of more than 2 °C in the last few decades, historical aerial photographs from the site indicated stable ice-wedge morphology over the last seven decades. Apparently, warming has thus far not been sufficient to initiate strong ice-wedge degradation, possibly due to the absence of extreme heat episodes in the maritime climate on Svalbard. However, in Arctic regions where ice-wedge degradation has already initiated the associated drying of landscapes, our results suggest a weakening of the CO2 sink of polygonal tundra.
- Subjects
TUNDRA ecology; CARBON monoxide; SPATIAL variation; TURBULENCE; POLYGONS
- Publication
Biogeosciences Discussions, 2016, p1
- ISSN
1810-6277
- Publication type
Article
- DOI
10.5194/bg-2016-537