Research Programs

Dust Cycle
FY2006 activities

TIIMES Theme:
BGS

Natalie Mahowald - CGD - TIIMES

Dust Cycle

Mineral aerosol or desert dust is thought to impact climate and biogeochemistry through several different mechanisms: direct radiative forcing, indirect radiative forcing, ocean biogeochemistry, terrestrial biogeochemistry and atmospheric chemistry. Mahowald's group is trying to understand both the causes of variability in mineral aerosols on short and long time scales, as well as the impacts of this variability on climate and biogeochemistry.

Over the past year, a paper documenting the dust cycle in the Community Atmosphere Model - Community Land Model [CAM-CLM] had been published and papers showing how dust responds to climate in the Community Climate System Model version 3.0 (CCSM3) have been published.  With collaborators within CGD, we included the ability of dust to feedback onto the climate, publishing one paper showing that dust could be important for enhancing the drought in the Sahel, and another paper showing for the first time, the response of climate to dust under different climates (last glacial maximum, preindustrial and future).

A paper is ready to be submitted on observational evidence for changes in dust sources from visibility data. In addition, the documentation of the prognostic sea salt in the CAM-CLM and the response to climate has been published.  We have also been working on document transport in the CAM due to changes in climate and dynamical cores with others in CGD, and the impact of meteorological variability on chemistry with collaborators in ACD.

Biogeochemistry

Desert dust deposition (g/m2/year) estimated from an average of three reanalysis based models simulated for 10+ years [Luo et al., 2003; Ginoux et al., 2004; Tegen et al., 2004], and representing our best estimate of dust deposition. Models compare well to available in situ and satellite observations and are shown here compared against sediment trap data [Kohfeld and Harrison, 2001].

In the area of biogeochemistry, we have published one review of atmospheric deposition of dust and the impacts on biogeochemistry (lead authored by Mahowald). 

In addition, we have published one paper on the fraction of bioavailable iron for ocean biota, and estimates using models based on atmospheric processing of iron, as well as a paper under preparation on the possibility that there are important combustion sources of iron as well, which might be more soluble and thus bioavailable than dust sources. 

We also have published a paper on the impact of biomass burning on atmospheric phosphorus deposition.