Recovering spatially and temporally dynamic regional scale carbon flux estimates
Date
2009
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Abstract
This dissertation presents two review type chapters and three new research chapters that contribute to our theoretical and practical knowledge about terrestrial carbon fluxes on the regional scale. This research expands on previous carbon dioxide inversion work by providing estimates of ecosystem respiration and gross primary productivity, as opposed to only net ecosystem exchange, and provides estimates on scales in time and space not previously available. The first two chapters provide an introduction and review material. This is necessary to provide the reader with an understanding of the relatively complex geostatistical atmospheric inversion process which uses carbon dioxide concentration data to provide terrestrial carbon flux estimates. Issues of scale are discussed as well previous work which was fundamental to the research presented here. The third and fourth chapters use simulated data to present an analysis of the methodology to a case study of North America in 2004. In particular, simulated data is used to investigate the sensitivity of the inversion to theoretical components of the inversion process and it is concluded that reasonably robust estimates of ecosystem respiration and gross primary productivity can be achieved by using a limited network of eight carbon dioxide observing towers. Chapter 4 specifically looks at the issue of small scale variability in carbon fluxes and the impact it has on obtaining larger scale regional estimates. Chapter five contains an analysis of real collected CO2 observation data from 2004 at the aforementioned eight observing sites. Results show significant seasonal and annual corrections to the a priori carbon flux estimates, in particular to the individual components of net ecosystem exchange, ecosystem respiration and gross primary productivity. Furthermore, the annual net ecosystem exchange, when presented spatially, provides clues to annual sources and sinks in 2004. Sensitivity is investigated with respect to numerous components of the inversion. Although large confidence bounds on estimates indicate statistical uncertainty in the mean estimate of net ecosystem exchange, estimates match reasonably well with previously conducted research as well as observational data. The research provides the estimates within a spatial context (and resolution) that was not previously available, allowing for the construction, and support, of much more descriptive hypotheses about carbon fluxes than was previously possible. Chapter six contains a summary of the results of the dissertation.
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Subject
carbon
carbon flux
net ecosystem exchange
ecology
atmospheric sciences