Biogeochemistry Group	Sunset in Alaska: tower ecosystem exchanges with the atmosphere

BGC Lab group meeting schedule spring 2003
You can still see the older schedule: winter 2003

Projects

Global modelling 18O in CO2 Observations of 18O in atmospheric CO2 from the global flask networks show pronounced seasonal cycles at temperate and high latitudes in the Northern Hemisphere. These cycles are dominated by interactions between leaf and soil water pools during terrestrial CO2 exchange. Because leaf water is typically enriched in 18O relative to soil water, photosynthetic and respiratory fluxes contribute opposing influences on atmospheric CO18O. Thus, given the 18O content of the water pools, atmospheric CO18O measurements provide a constraint on the timing and magnitude of the associated terrestrial CO2 fluxes. These processes can readily be incorperates in state-of-the-art global climate models. By experimentation the isotopic signal of changes in the terrestrial biosphere can be deduced. (David Noone, Jim Randerson)

The importance of Arctic ice and snow for the global carbon cycle Oxygen-18 in atmospheric CO2 is a powerful tracer of biospheric production as it reflects changes in both leaf photosynthesis and soil respiration. Although the mean seasonal cycle of atmospheric CO18O is well understood in a climatological sense, there is large interannual variability (e.g., the seasonal amplitude changed by a factor of two during the 1990s), which is presently without explanation. One possible reason is that variability in boreal snow cover and sea ice conditions changes the character and efficiency of carbon cycling in terrestrial ecosystems. The changes in CO18O are related to both the direct effects of variations in isotopic state of the water cycle, and the indirect effects of changes to the biosphere function in response to change in atmospheric parameters. As such, the CO18O can change even though the total CO2 exchange is constant. The O18 tracer is therefore evoked to explore the importance of the high latitude mechanisms contributing to carbon cycle variability. The behavior of these mechanisms is elucidated using and atmospheric general circulation model and a process-based terrestrial biosphere model, both capable of accounting for the isotopic exchanges. (David Noone, Jim Randerson)

Response of boreal biosphere volcanic driven climate events

Data Sets

Global 1x1 degree NPP and NEP data from CASA (Randerson et al., Bio. Geochem. Cyc., 11, 535-560, 1997)

See also the BGC public FTP site

Links: BGC on the Web

• Global Emissions Inventory Activity (GEIA)
  
• International Global Atmospheric Chemistry (IGAC)
  

BGC People at Caltech

People of BGC present... Jim Randerson <jimr@gps.caltech.edu> David Noone <dcn@gps.caltech.edu> Seth Olsen <olsen@gps.caltech.edu> Lisa Welp <jimr@gps.caltech.edu> Nicole Smith <nicolev@gps.caltech.edu> Heping Liu <heping@gps.caltech.edu> Zhonghua Yang <yangzh@gps.caltech.edu>

People of BGC past... Julianna Fessenden< <julianna@lanl.gov> (Los Almos National Laboratory)

Group Publications

Krakauer, N. Y., and J T. Randerson, 2003: Do volcanic eruptions enhance or diminish net primary production? Evidence from tree rings.Biogeochem. Cycles, submitted, April 2003. (manuscript Word document)

Noone, D., C. Still and W. Riley, 2002: A global biophysical model of ¹⁸O in terrestrial water and CO₂ fluxes. Research Activities in Atmospheric and Oceanic Modelling, Report No. 32, World Meteorological Organization, 4.19-4.20 HTML | PDF

Noone, D. C., Still, C. J. and W. J. Riley, 2001: Influence of Land Use Change on the ¹⁸O in Atmospheric CO₂: Comparison of Preindustrial, Modern and Future Scenarios Eos Trans. AGU, 82 Fall Meet. Suppl., Abstract B11A-07

Noone, D., C. Still and W. Riley, 2001: (POSTER) Diagnosing impacts of changes in the biosphere by modelling ¹⁸O of atmospheric CO₂ with a general circulation model, Sixth International CO₂ Conference, Sendei, Japan.

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David Noone <dcn@caltech.edu> Last updated:

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