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| Titel |
Analysis of CO2 mole fraction data: first evidence of large-scale changes in CO2 uptake at high northern latitudes |
| VerfasserIn |
J. M. Barlow, P. I. Palmer, L. M. Bruhwiler, P. Tans |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 15, no. 23 ; Nr. 15, no. 23 (2015-12-14), S.13739-13758 |
| Datensatznummer |
250120222
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| Publikation (Nr.) |
 copernicus.org/acp-15-13739-2015.pdf |
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| Zusammenfassung |
| Atmospheric variations of carbon dioxide (CO2) mole fraction
reflect changes in atmospheric transport and regional patterns of
surface emission and uptake. Here we present a study of changes in the
observed high northern latitude CO2 seasonal cycle. We report new estimates for changes in
the phase and amplitude of the seasonal variations, indicative of biospheric changes,
by spectrally decomposing multi-decadal records of surface
CO2 mole fraction using a wavelet transform to isolate the
changes in the observed seasonal cycle. We also perform similar
analysis of the first derivative of CO2 mole fraction,
ΔtCO2, that is a crude proxy for changes in
CO2 flux. Using numerical experiments, we quantify the
aliasing error associated with independently identifying trends in
phase and peak uptake and release to be 10–25 %, with the
smallest biases in phase associated with the analysis of
ΔtCO2. We report our analysis from Barrow, Alaska
(BRW), during 1973–2013, which is representative of the broader
Arctic region. We determine an amplitude trend of 0.09 ±
0.02 ppm yr-1, which is consistent with previous work.
Using ΔtCO2 we determine estimates for the timing of
the onset of net uptake and release of CO2 of −0.14 ±
0.14 and −0.25 ± 0.08 days yr-1 respectively and
a corresponding net uptake period of −0.11 ±
0.16 days yr-1, which are significantly different to
previously reported estimates. We find that the wavelet transform
method has significant skill in characterizing changes in the peak
uptake and release. We find a trend of 0.65 ± 0.34 % yr-1 (p <
0.01) and 0.42 ± 0.34 % yr-1 (p < 0.05) for rates of peak
uptake and release respectively. Our analysis does not provide
direct evidence about the balance between uptake and release of
carbon when integrated throughout the year, but the increase in the seasonal
amplitude of CO2 together with an invariant net carbon uptake period
provides evidence that high northern latitude ecosystems are progressively taking up more
carbon during spring and early summer. |
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