HR: 0815h
AN: A11K-02
TI: Observed 20th Century Desert Dust Variability: Impact on Climate and Biogeochemistry (Invited)
AU: *Mahowald, N M
EM: nmm63@cornell.edu
AF: EAS, Cornell, Ithaca, NY, USA
AU: Kloster, S
EM: silvia.kloster@zmaw.de
AF: EAS, Cornell, Ithaca, NY, USA
AU: Engelstaedter, S
EM: se225@cornell.de
AF: EAS, Cornell, Ithaca, NY, USA
AU: Moore, J K
EM: jkmoore@uci.edu
AF: ESS, UCI, Irvine, CA, USA
AU: Mukhopadhyay, S
EM: sujoy@eps.harvard.edu
AF: EPS, Harvard, Cambridge, MA, USA
AU: McConnell, J R
EM: jmcconn@dri.edu
AF: Hydrology, DRI, Reno, NV, USA
AU: Albani, S
EM: samuel.albani@unimib.it
AF: EAS, Cornell, Ithaca, NY, USA
AU: Doney, S C
EM: sdoney@whoi.edu
AF: MCG, WHOI, Woods Hole, MA, USA
AU: Bhattacharya, A
EM: atreyee4u@gmail.com
AF: EPS, Harvard, Cambridge, MA, USA
AU: Curran, M A
EM: mark.curran@utas.edu.au
AF: AAD, Hobart, TAS, Australia
AU: Flanner, M G
EM: flanner@umich.edu
AF: DAOSS, UM, Ann Arbor, MI, USA
AU: Hoffman, F M
EM: forrest@climatemodeling.org
AF: CESG, ORNL, Oak Ridge, TN, USA
AU: Lawrence, D M
EM: dlawren@ucar.edu
AF: CGD, NCAR, Boulder, CO, USA
AU: Lindsay, K T
EM: klindsay@ucar.edu
AF: CGD, NCAR, Boulder, CO, USA
AU: Mayewski, P A
EM: paul.mayewski@maine.edu
AF: CCI, UM, Orono, ME, USA
AU: Neff, J C
EM: neffjc@colorado.edu
AF: Geosciences and Environmental Studies Program, CU, Boulder, CO, USA
AU: Rothenberg, D
EM: dar256@cornell.edu
AF: EAS, Cornell, Ithaca, NY, USA
AU: Thomas, E R
EM: lith@bas.ac.uk
AF: BAS, Cambridge, United Kingdom
AU: Thornton, P E
EM: thorntonpe@ornl.gov
AF: CESG, ORNL, Oak Ridge, TN, USA
AB: Desert dust perturbs climate by interacting with incoming solar and outgoing long wave radiation, thereby changing precipitation and temperature, in addition to modifying ocean and land biogeochemistry. While we know that desert dust is sensitive to perturbations in climate and human land use, previous studies have been unable to determine whether humans were in the net increasing or decreasing desert dust. Here we present observational estimates of desert dust based on paleodata proxies showing a doubling of desert dust during the 20th century over much, but not all the globe. Large uncertainties remain in estimates of desert dust variability over 20th century due to limited data. Using these observational estimates of desert dust change in combination with ocean, atmosphere and land models, we calculate the net radiative effect of these observed changes (top of atmosphere) over the 20th century to be -0.14 +/- 0.11 W/m2 (1990- 1999 vs. 1905-1914). The estimated radiative change due to aerosols is especially strong between the dusty 1980-1989 and the less dusty 1955-1964 time periods (-0.57 +/-0.46 W/m2), which model simulations suggest may have reduced the rate of temperature increase between these time periods by 0.11 C. Model simulations also indicate strong regional shifts in precipitation and temperature from the desert dust changes, causing 6 ppm (12 PgC) reduction in model carbon uptake by the terrestrial biosphere over the 20th century. Desert dust carries iron, an important micronutrient for ocean biogeochemistry that can modulate ocean carbon storage; here we show that dust deposition trends increase ocean productivity by an estimated 6% over the 20th century, drawing down an additional 4 ppm (8 PgC) of carbon dioxide into the oceans. Thus, perturbations to desert dust over the 20th century inferred from observations are potentially important for climate and biogeochemistry, and our understanding of these changes and their impacts should continue to be refined.
DE: [0305] ATMOSPHERIC COMPOSITION AND STRUCTURE / Aerosols and particles
DE: [0428] BIOGEOSCIENCES / Carbon cycling
DE: [1616] GLOBAL CHANGE / Climate variability
DE: [1622] GLOBAL CHANGE / Earth system modeling
SC: Atmospheric Sciences (A)
MN: 2010 Fall Meeting

Acknowledgements
Research partially sponsored by the Climate and Environmental Sciences Division (CESD) of the Office of Biological and Environmental Research (OBER), U.S. Department of Energy Office of Science (SC). This research used resources of the National Center for Computational Science (NCCS) at Oak Ridge National Laboratory (ORNL) which is managed by UT-Battelle, LLC, for the U.S. Department of Energy under Contract No. DE-AC05-00OR22725.