HR: 0830h
AN: B31E-0345    [PDF]
TI: Isotope Signals on Multiple Timescales Simulated Using a Simple Earth System Model Incorporating Variable Ecosystem Features
AU: Koury, J
EM: jessica.koury@colorado.edu
AF: CIRES, University of Colorado, Boulder, CO 80303 United States
AU: * Nordstrom, K
EM: nordstrom@comcast.net
AF: CIRES, University of Colorado, Boulder, CO 80303 United States
AU: Henderson-Sellers, A
EM: ahssec@ansto.gov.au
AF: ANSTO Environment, PMB 1, Menai, NSW 2234 Australia
AU: McGuffie, K
EM: kendal.mcguffie@uts.edu.au
AF: Applied Physics, University of Technology, Broadway, NSW 2007 Australia
AU: Chase, T
EM: tchase@cires.colorado.edu
AF: CIRES, University of Colorado, Boulder, CO 80303 United States
AB: Stable isotopes of water and stable and radioactive isotopes of carbon, are employed widely in Earth system modelling. Carbon isotopes differentiate and monitor biological and abiological sources and sinks of CO$_2$ and CH$_4$ (e.g. Ciais {\it et al.}, 1995) while the stable isotopes of water have been used to interpret long-term temperature trends since Dansgaard (e.g. Petit {\it et al.}, 1999). While early Global Climate Models (GCMs) were used to attempt to verify and interpret isotopic measurements (e.g. Joussaume {\it et al.}, 1984), more recent GCMs have challenged the simple correlations upon which ecosystem-based isotopic flux interpretation is founded (e.g. Noone and Simmonds, 2002). These contradictions present an opportunity for an isotopically capable EMIC (Earth-system Model of Intermediate Complexity) with which to investigate isotopes as indicators of ecosystem flux changes. We have added isotopic representation of $^{18}$O and D in water to a DAFM (Dynamic Area Fraction Model) and hence assessed $\delta$D and $\delta^{18}$O in precipitation as a function of local and global temperatures. In many situations, local relationships are developed between the isotopic composition of precipitation and the local mean temperature. Such relationships are then applied to palaeo-isotopic ratios derived from ice cores to develop palaeo-temperature datasets and are sensitive to other aspects of the climate system. In addition to the evaluation of this simple model for isotopic studies, this paper evaluates the dependency of $\delta$D and $\delta^{18}$O enrichment/depletion on temperatures and the sensitivity to (i) local temperatures; (ii) moisture sources and transported distance; (iii) surface cover dynamics (i.e. ice, water, plants); (iv) the sensitivity of carbon pools; (v) biological and abiological sources over time; and (vi) modification of carbon sources and sinks as a function of climate.
DE: 0315 Biosphere/atmosphere interactions
DE: 0322 Constituent sources and sinks
SC: Biogeosciences [B]
MN: 2003 Fall Meeting