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CGD Publications: Archived Abstracts

May 2006 Abstracts

Change in atmospheric mineral aerosols in response to climate: Last glacial period, preindustrial, modern, and doubled carbon dioxide climates

Abstract: Figure. Desert dust simulations generated by the National Center for Atmospheric Research's Community Climate System Model for the current climate are shown to be consistent with present day satellite and deposition data. The response of the dust cycle to last glacial maximum, preindustrial, modern, and doubled-carbon dioxide climates is analyzed. Only natural (non-land use related) dust sources are included in this simulation. Similar to some previous studies, dust production mainly responds to changes in the source areas from vegetation changes, not from winds or soil moisture changes alone. This model simulates a +92%, +33%, and −60% change in dust loading for the last glacial maximum, preindustrial, and doubled-carbon dioxide climate, respectively, when impacts of carbon dioxide fertilization on vegetation are included in the model. Terrestrial sediment records from the last glacial maximum compiled here indicate a large underestimate of deposition in continental regions, probably due to the lack of simulation of glaciogenic dust sources. In order to include the glaciogenic dust sources as a first approximation, we designate the location of these sources, and infer the size of the sources using an inversion method that best matches the available data. The inclusion of these inferred glaciogenic dust sources increases our dust flux in the last glacial maximum from 2.1 to 3.3 times current deposition.

Received 7 September 2005; accepted 17 February 2006; published 31 May 2006.

Citation: Mahowald, N. M., D. R. Muhs, S. Levis, P. J. Rasch, M. Yoshioka, C. S. Zender, and C. Luo (2006), Change in atmospheric mineral aerosols in response to climate: Last glacial period, preindustrial, modern, and doubled carbon dioxide climates, J. Geophys. Res., 111, D10202, doi:10.1029/2005JD006653.

Authored by:

Natalie M. Mahowald
National Center for Atmospheric Research, Boulder, Colorado, USA

Daniel R. Muhs
U.S. Geological Survey, Denver, Colorado, USA

Samuel Levis
National Center for Atmospheric Research, Boulder, Colorado, USA

Philip J. Rasch
National Center for Atmospheric Research, Boulder, Colorado, USA

Masaru Yoshioka
National Center for Atmospheric Research, Boulder, Colorado, USA
Institute for Computational Earth Systems Science, University of California, Santa Barbara, California, USA

Charles S. Zender
Department of Earth System Science, University of California, Irvine, California, USA

Chao Luo
Department of Earth System Science, University of California, Irvine, California, USA

Journal of Geophysical Research, Vol. 111, D10202, doi:10.1029/2005JD006653, 2006

North Pacific Decadal Variability in the Community Climate System Model Version 2

Figure. North Pacific decadal oceanic and atmospheric variability is examined from a 650-year control integration of Community Climate System Model version 2. The dominant pattern of winter sea surface temperature (SST) variability is similar to the observed "Pacific Decadal Oscillation", with maximum amplitude along the Kuroshio Current Extension. SST anomalies in this region exhibit significant spectral peaks at approximately 16 years and 40 years. Lateral geostrophic heat flux divergence, caused by a meridional shift of the Kuroshio Current Extension forced by basin scale wind stress curl anomalies 3-5 years earlier, is responsible for the decadal SST variability; local surface heat flux and Ekman heat flux divergence act as a damping and positive feedback, respectively. A simple linear Rossby wave model is invoked to explicitly demonstrate the link between the wind stress curl forcing and decadal variability in the Kuroshio Current Extension. The Rossby wave model not only successfully reproduces the two decadal spectral peaks, but also illustrates that only the low-frequency (> 10-year period) portion of the approximately white-noise wind stress curl forcing is relevant. This model also demonstrates that the weak and insignificant decadal spectral peaks in the wind stress curl forcing are necessary for producing the corresponding strong and significant oceanic peaks in the Kuroshio Current Extension. The wind stress curl response to decadal SST anomalies in the Kuroshio Current Extension is similar in structure but opposite in sign and somewhat weaker than the wind stress curl forcing pattern. These results suggest that the simulated North Pacific decadal variability owes its existence to two-way ocean-atmosphere coupling.