Annual patterns and budget of CO₂ flux in an Arctic tussock tundra ecosystem

Authors

Walter C. Oechel, San Diego State University
Cheryl A. Laskowski, San Diego State University
George Burba, LI-COR Biosciences, Lincoln, NebraskaFollow
Beniamino Gioli, IBIMET CNR, Florence, Italy
Aram A. M. Kalhori, San Diego State University

Document Type

Article

Date of this Version

2014

Citation

Oechel, W. C., C. A. Laskowski, G. Burba, B. Gioli, and A. A. M. Kalhori (2014), Annual patterns and budget of CO₂ flux in an Arctic tussock tundra ecosystem, J. Geophys. Res. Biogeosci., 119, 323–339, doi:10.1002/2013JG002431.

Comments

Copyright 2014 The Authors. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License

Abstract

The functioning of Arctic ecosystems is not only critically affected by climate change, but it also has the potential for major positive feedback on climate. There is, however, relatively little information on the role, patterns, and vulnerabilities of CO₂ fluxes during the nonsummer seasons in Arctic ecosystems. Presented here is a year-round study of CO₂ fluxes in an Alaskan Arctic tussock tundra ecosystem, and key environmental controls on these fluxes. Important controls on fluxes vary by season. This paper also presents a new empirical quantification of seasons in the Arctic based on net radiation. The fluxes were computed using standard FluxNet methodology and corrected using standard Webb-Pearman-Leuning density terms adjusted for influences of open-path instrument surface heating. The results showed that the nonsummer season comprises a significant source of carbon to the atmosphere. The summer period was a net sink of 24.3 g Cm^-2, while the nonsummer seasons released 37.9 g Cm^-2. This release is 1.6 times the summer uptake, resulting in a net annual source of +13.6 g Cm^-2 to the atmosphere. These findings support early observations of a change in this particular region of the Arctic from a long-term annual sink of CO₂ to an annual source from the terrestrial ecosystem and soils to the atmosphere. The results presented here demonstrate that nearly continuous observations may be required in order to accurately calculate the annual net ecosystem CO₂ exchange of Arctic ecosystems and to build predictive understanding that can be used to estimate, with confidence, Arctic fluxes under future conditions.