HR: 14:55h
AN: B33G-06    [Abstracts]
TI: Terrestrial carbon-nitrogen cycle coupling and interactions with the climate system
AU: * Thornton, P E
EM: thornton@ucar.edu
AF: National Center for Atmospheric Research, P.O. Box 3000, Boulder, CO 80307-3000 United States
AU: Vertenstein, M
EM: mvertens@ucar.edu
AF: National Center for Atmospheric Research, P.O. Box 3000, Boulder, CO 80307-3000 United States
AU: Lee, J
EM: jeff@ucar.edu
AF: National Center for Atmospheric Research, P.O. Box 3000, Boulder, CO 80307-3000 United States
AU: Lamarque, J
EM: lamar@ucar.edu
AF: National Center for Atmospheric Research, P.O. Box 3000, Boulder, CO 80307-3000 United States
AB: We show results from coupled climate system model simulations using the NCAR CCSM3 with modifications to introduce fully prognostic terrestrial carbon and nitrogen cycle dynamics. Simulations were run with active atmosphere and land components, using data sea surface temperature and sea ice distribution for the historical period 1850-2000, following as closely as possible the C4MIP Phase 1 protocol. Four simulations were performed to assess the independent and interacting effects of increasing atmospheric CO2 concentration and increasing mineral nitrogen deposition on the coupled climate system. A control experiment was performed with historical SST and sea ice drivers, but constant CO2 and nitrogen deposition. Three experiments were then conducted, with increasing CO2, increasing nitrogen deposition, and both CO2 and nitrogen deposition increasing together. Differences between the simulations are used to assess the influence of climate variation, CO2 and nitrogen fertilization of the terrestrial biosphere, and combined effects on the global carbon cycle. CO2 fluxes from land are transported in the atmosphere, together with data ocean and data fossil fuel fluxes, and the resulting CO2 concentrations are compared to historical observations. The effect of observed SST variation on climate is a net warming of the climate with an increase in precipitation, which produces a net land carbon uptake. The effect of increasing CO2 is an additional warming of the climate, and additional land carbon uptake due to both warming, increased precipitation, and direct fertilization. Under increasing CO2 the predicted nitrogen limitation increases, limiting the predicted land uptake. The additional effect of increasing nitrogen deposition is to further strengthen the land uptake, with a large degree of spatial variability in the interaction effect between the CO2 response and the nitrogen deposition response.
DE: 0426 Biosphere/atmosphere interactions (0315)
DE: 0428 Carbon cycling (4806)
DE: 0429 Climate dynamics (1620)
DE: 0466 Modeling
DE: 0469 Nitrogen cycling
SC: Biogeosciences [B]
MN: Fall Meeting 2005