HR: 10:20h
AN: PP52A-01    [Abstracts]
TI: Carbon Dioxide and the Early Eocene Climate of Western North America
AU: * Thrasher, B
EM: thrasher@pmc.ucsc.edu
AF: Department of Earth and Planetary Sciences, University of California Santa Cruz, 1156 High Street, Santa Cruz, CA 95064, United States
AU: Sloan, L
EM: lcsloan@pmc.ucsc.edu
AF: Department of Earth and Planetary Sciences, University of California Santa Cruz, 1156 High Street, Santa Cruz, CA 95064, United States
AB: Concentrations of atmospheric greenhouse gases play an important role in determining the climate by way of emitting longwave radiation towards the Earth, thereby increasing the temperature of the surface and lower atmosphere above that which would be measured in the absence of these constituents. Carbon dioxide (CO₂), a well-mixed greenhouse gas, is naturally added to the atmosphere through aerobic biological respiration and decay, volcanic eruptions, and dissociation from ocean water. Meanwhile, it is removed from the atmosphere through photosynthesis, chemical weathering, and diffusion into the oceans. All of these factors make it difficult to pinpoint the concentration of atmospheric CO₂ in the distant past. Indeed, estimates of CO₂ concentration during the early Eocene (~ 55 million years ago) vary widely, from 300 ppm to upwards of 2000 ppm. This study employs a regional climate model to examine the effects of different CO₂ levels on temperature and precipitation under early Eocene conditions. The region of interest, western North America, contains fossil evidence from the early Eocene that suggests regional rainfall was substantial enough and temperatures were warm enough to support subtropical vegetation, whereas today the region is primarily characterized by desert and steppe.
DE: 3305 Climate change and variability (1616, 1635, 3309, 4215, 4513)
DE: 3344 Paleoclimatology (0473, 4900)
DE: 3355 Regional modeling
DE: 9350 North America
DE: 9606 Paleogene
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting