Towards multi-tracer data-assimilation: biomass burning and carbon isotope exchange in SiBCASA

I.R. van der Velde, J.B. Miller, K. Schaefer, G.R. van der Werf, M.C. Krol, W. Peters

Research output: Contribution to journalArticleAcademicpeer-review

Abstract

We present an enhanced version of the SiBCASA photosynthetic/biogeochemical model for a future integration with a multi-tracer data-assimilation system. We extended the model with (a) biomass burning emissions from the SiBCASA carbon pools using remotely sensed burned area from Global Fire Emissions Database (GFED) version 3.1, (b) a new set of 13C pools that cycle consistently through the biosphere, and (c), a modified isotopic discrimination scheme to estimate variations in 13C exchange as a~response to stomatal conductance. Previous studies suggest that the observed variations of atmospheric 13C/12C are driven by processes specifically in the terrestrial biosphere rather than in the oceans. Therefore, we quantify in this study the terrestrial exchange of CO2 and 13CO2 as a function of environmental changes in humidity and biomass burning. Based on an assessment of observed respiration signatures we conclude that SiBCASA does well in simulating global to regional plant discrimination. The global mean discrimination value is 15.2‰, and ranges between 4 and 20‰ depending on the regional plant phenology. The biomass burning emissions (annually and seasonally) compare favorably to other published values. However, the observed short-term changes in discrimination and the respiration 13C signature are more difficult to capture. We see a too weak drought response in SiBCASA and too slow return of anomalies in respiration. We demonstrate possible ways to improve this, and discuss the implications for our current capacity to interpret atmospheric 13C observations
Original languageEnglish
Pages (from-to)107-149
JournalBiogeosciences Discussions
Volume11
Issue number1
DOIs
Publication statusPublished - 2014

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