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| Titel |
Inter-annual variability in Alaskan net ecosystem CO2 exchange |
| VerfasserIn |
Kristina Luus, Jakob Lindaas, Roisin Commane, Eugenie Euskirchen, Walter Oechel, Donatella Zona, Rachel Chang, Richard Kelly, Charles Miller, Steven Wofsy, John Lin |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250107326
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| Publikation (Nr.) |
 EGU/EGU2015-7023.pdf |
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| Zusammenfassung |
| The high-latitude biospheric carbon cycle’s responses to climate change are predicted to have
an important role in determining future atmospheric concentrations of CO2. In response to
warming soil and air temperatures, Arctic wetlands have been observed to increase rates of
both soil C efflux and vegetation C uptake through photosynthesis. However, insights into the
regional-scale consequences of these processes for net C uptake have been limited by the
large uncertainties existing in process-based model estimates of Arctic net ecosystem CO2
exchange (NEE).
The Polar Vegetation Photosynthesis and Respiration Model (PolarVPRM) instead
provides data-driven, satellite-based estimates of high-latitude NEE, using a framework
which specifically accounts for polar influences on NEE. PolarVPRM calculates NEE
as the sum of respiration (R) and gross ecosystem exchange (GEE), where GEE
refers to the light-dependent portion of NEE: NEE= -GEE + R. Meteorological
inputs for PolarVPRM are provided by the North American Regional Reanalysis
(NARR), and land surface inputs are acquired from the Moderate Resolution Imaging
Spectroradiometer (MODIS). Growing season R is calculated from air temperature,
and subnivean R is calculated according to soil temperature. GEE is calculated
according to shortwave radiation, air temperature, and MODIS-derived estimates of soil
moisture and vegetation biomass. Previously, model validation has indicated that
PolarVPRM showed reasonably good agreement with eddy covariance observations at nine
North American Arctic sites, of which three were used for calibration purposes.
For this project, PolarVPRM NEE was calculated year-round across Alaska at a
three-hourly temporal resolution and a spatial resolution of 1
6°x1
4° (latitude x
longitude).
The objective of this work was to gain insight into inter-annual variability in Alaskan
NEE, R and GEE, and an understanding of which meteorological and land surface drivers
account for these observed patterns. This was accomplished by first examining
regional-scale PolarVPRM output in conjunction with airborne observations of
atmospheric CO2 concentrations from NASA’s Carbon in Arctic Reservoirs Vulnerability
Experiment (CARVE). These regional-scale findings were then examined carefully in
relation to eddy covariance observations from sites along Alaska’s North Slope.
This was completed in order to validate PolarVPRM estimates of NEE, as well as
to examine the extent to which the model structure and inputs were capable of
capturing inter-annual variability in NEE observed at Alaskan eddy covariance
sites.
Statistical analyses were then applied to elucidate regional-scale inter-annual variability
in PolarVPRM NEE, R and GEE, as well as their associations with NARR meteorological
drivers and MODIS land surface inputs. These analyses were conducted with a
specific focus on inter-annual variability across wetland regions of Alaska’s North
Slope. Analyses indicated that inter-annual variability in growing season length, soil
moisture, vegetation biomass, air/soil temperatures, and shortwave radiation induced
inter-annual variability in observed and modeled Alaskan net ecosystem CO2 exchange. |
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