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dc.contributor.authorPirk, Norbert
dc.contributor.authorSievers, Jakob
dc.contributor.authorMertes, Jordan
dc.contributor.authorParmentier, Frans-Jan
dc.contributor.authorMastepanov, Mikhail
dc.contributor.authorChristensen, Torben R
dc.date.accessioned2017-11-24T08:54:40Z
dc.date.available2017-11-24T08:54:40Z
dc.date.issued2017-06-29
dc.description.abstractThe large spatial variability in Arctic tundra complicates the representative assessment of CO<sub>2</sub> budgets. Accurate measurements of these heterogeneous landscapes are, however, essential to understanding their vulnerability to climate change. We surveyed a polygonal tundra lowland on Svalbard with an unmanned aerial vehicle (UAV) that mapped ice-wedge morphology to complement eddy covariance (EC) flux measurements of CO<sub>2</sub>. The analysis of spectral distributions showed that conventional EC methods do not accurately capture the turbulent CO<sub>2</sub> exchange with a spatially heterogeneous surface that typically features small flux magnitudes. Nonlocal (low-frequency) flux contributions were especially pronounced during snowmelt and introduced a large bias of -46 gCm<sup>-2</sup> to the annual CO<sub>2</sub> budget in conventional methods (the minus sign indicates a higher uptake by the ecosystem). Our improved flux calculations with the ogive optimization method indicated that the site was a strong sink for CO<sub>2</sub> in 2015 (-82 gCm<sup>-2</sup>). Due to differences in light-use efficiency, wetter areas with lowcentered polygons sequestered 47% more CO<sub>2</sub> than drier areas with flat-centered polygons. While Svalbard has experienced a strong increase in mean annual air temperature of more than 2K in the last few decades, historical aerial photographs from the site indicated stable ice-wedge morphology over the last 7 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 CO<sub>2</sub> sink in polygonal tundra.en_US
dc.descriptionSource at <a href=https://doi.org/10.5194/bg-14-3157-2017> https://doi.org/10.5194/bg-14-3157-2017 </a>en_US
dc.identifier.citationPirk N, Sievers J, Mertes J, Parmentier FJW, Mastepanov M, Christensen TR. Spatial variability of CO2 uptake in polygonal tundra: Assessing low-frequency disturbances in eddy covariance flux estimates. Biogeosciences. 2017;14(12):3157-3169en_US
dc.identifier.cristinIDFRIDAID 1498444
dc.identifier.doi10.5194/bg-14-3157-2017
dc.identifier.issn1726-4170
dc.identifier.issn1726-4189
dc.identifier.urihttps://hdl.handle.net/10037/11773
dc.language.isoengen_US
dc.publisherCopernicus Publicationsen_US
dc.relation.journalBiogeosciences
dc.rights.accessRightsopenAccessen_US
dc.subjectVDP::Matematikk og Naturvitenskap: 400::Geofag: 450::Mineralogi, petrologi, geokjemi: 462en_US
dc.subjectVDP::Mathematics and natural science: 400::Geosciences: 450::Mineralogy, petrology, geochemistry: 462en_US
dc.titleSpatial variability of CO2 uptake in polygonal tundra: Assessing low-frequency disturbances in eddy covariance flux estimatesen_US
dc.typeJournal articleen_US
dc.typeTidsskriftartikkelen_US
dc.typePeer revieweden_US


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