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Abstract:
Among other regions of the world, the Arctic is
strongly affected by climate change. Globally, it is
the region with the most pronounced warming, leading
to permafrost warming and thawing. Part of the
1,300 Pg soil organic carbon currently stored in the
frozen ground is already and might be further released
as carbon dioxide (CO2) and methane (CH4). CO2
is released through aerobic soil respiration and from
plant roots, but also sequestered through photosynthesis.
CH4 emission can be attributed to either recent
microbial activity or to past microbial or thermal decomposition
and is spatially heterogeneous. To our
knowledge, regional assessments of the total carbon
flux (CO2 and CH4) based on high frequency airborne
measurements do not exist.
Here we determine the regional pattern of CO2 and
total carbon emissions (CO2 + CH4) of the Mackenzie
Delta region, Canada, based on the Airborne Measurements
of Methane Fluxes Campaign (AIRMETH)
in July 2013 [Kohnert et al., 2014].
The Mackenzie Delta is the second largest arctic
delta (13,000 km2). Our measurements covered an
area extending 320 km from west to east (140°58’
W to 133°22’W) and of 240 km from north to south
(69°33’N to 67°26’N). The study area is heterogeneous
and comprises the delta itself, the adjacent Yukon
coastal plain, and Richards Island north east of the
delta. Part of the delta is located north of the treeline.
The area surrounding the delta is described as continuous
permafrost zone where the permafrost reaches
a thickness of 300 m along the coastal plain and 500
m on Richards Island. In the delta itself the discontinuous
permafrost reaches a maximum thickness of
100 m.
For the AIRMETH campaign we used the research
aircraft Polar 5. Equipped with a 5-hole probe, the
usual meteorological sensors, and a fast greenhouse
gas analyser (GGA 24EP, Los Gatos Research Inc.)
we flew at 30 - 60 m above ground at a true airspeed
of 60 m s−1.
CO2 and CH4 fluxes were calculated with a timefrequency
resolved version of the eddy-covariance technique
[Metzger et al., 2013]. We calculated flux topographies
[Mauder et al., 2008] to resolve the fluxes
along a linear flight track to the area within the footprint
of the measurements. The result is a 100 m resolved
gridded carbon flux map within the footprints
of the flight tracks. Based on the flux topographies
we produce a map of the regional pattern of peak
growing season carbon fluxes.
