HR: 09:12h
AN: A51F-06    [Abstracts]
TI: Response of eastern boundary current upwelling to regional-scale atmosphere-land cover feedbacks induced by elevated atmospheric carbon dioxide concentrations
AU: * Diffenbaugh, N S
EM: diffenbaugh@purdue.edu
AF: Department of Earth and Atmospheric Sciences, Purdue University, 550 Stadium Mall Drive, West Lafayette, IN 47907-2051 United States
AU: Snyder, M A
EM: msnyder@es.ucsc.edu
AF: Department of Earth Sciences, University of California - Santa Cruz, 1156 High Street, Santa Cruz, CA 95064 United States
AU: Sloan, L C
EM: lcsloan@es.ucsc.edu
AF: Department of Earth Sciences, University of California - Santa Cruz, 1156 High Street, Santa Cruz, CA 95064 United States
AB: The response of marine and terrestrial environments to global changes in atmospheric carbon dioxide concentrations will likely be governed both by responses to direct environmental forcing and by responses to Earth system feedbacks induced by that forcing. It has been proposed that anthropogenic greenhouse forcing will intensify coastal upwelling in eastern boundary current regions. To test the potential response of eastern boundary current upwelling to regional-scale atmosphere-land cover feedbacks, we have employed a regional climate model (RegCM2.5) asynchronously coupled to an equilibrium vegetation model (BIOME4), focusing on the California Current as a case study. Biophysical atmosphere-land cover feedbacks enhanced the radiative effects of carbon dioxide on land-sea thermal contrast, resulting in changes in total-seasonal upwelling and upwelling seasonality. Specifically, relative to greenhouse forcing, land cover-atmosphere feedbacks led to a stronger increase in peak- and late-season upwelling in the northern limb of the California Current and a stronger decrease in peak- and late-season upwelling in the southern limb. The response of coastal upwelling to atmosphere-land cover feedbacks was driven by changes in surface temperature over land. Of the total seasonal temperature response to elevated atmospheric carbon dioxide levels, up to 60 % was due to land cover change. In many areas, such as the Great Basin, albedo acted as the primary control on these changes in surface temperature. Along the central coast of California, soil moisture effects magnified the temperature response in JJA and SON, with negative surface soil moisture anomalies accompanied by negative evaporation anomalies, decreasing latent heating and further increasing surface temperature. Additionally, negative temperature anomalies were calculated at high elevation in California and Oregon in DJF, MAM and SON, indicating that future warming of these sensitive areas could be mitigated by changes in vegetation distribution and an associated muting of winter snow-temperature feedbacks. However, the mean regional temperature sensitivity to regional-scale land cover feedbacks did not exceed the large-scale sensitivity calculated elsewhere, indicating that spatial heterogeneity does not introduce non-linearities in the response of regional temperature to carbon dioxide-induced atmosphere-land cover feedbacks.
DE: 4279 Upwelling and convergences
DE: 4516 Eastern boundary currents
DE: 1620 Climate dynamics (3309)
DE: 0315 Biosphere/atmosphere interactions
DE: 0400 Biogeosciences
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting