Temporal
and spatial distributions of the δ18O value of atmospheric CO2
(dCa) can be used to constrain regional
ecosystem carbon exchanges and linkages between carbon and water cycling.
However, our understanding of the substantial observed temporal and spatial
variability in dCa is limited. Among many contributing
factors, seasonal and inter-annual variations in climate are likely to be
important. In this study we investigate the impact of dry climatic conditions
on the ecosystem-atmosphere C18OO isoflux.
We conducted this study in the
U.S. Southern Great Plains using five-year monthly-averaged precipitation δ18O
values (δp) from the
National Atmospheric Deposition Program (NADP) network, Mesonet meteorological
forcing, and MODIS-derived NDVI and land-cover characterization. These data are
used to force the isotope ecosystem model ISOLSM [Riley et al., 2002; Riley et al., 2003] at 10 km resolution across the region for relatively
drier (2003) and wetter (2004) years. The model has been calibrated and tested
in the dominant herbaceous vegetation types in the region [Biraud et
al., this issue].
Author: W.J. Riley, C.J. Still, R. Vachon, J. Welker, et al (wjriley at lbl dot gov)
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