The mineral composition of desert dust affects global climate both radiatively and as a source of nutrients to the terrestrial and the marine ecosystems. Dust clouds strongly influence the earth’s radiative budget by absorption and scattering in both the near-UV, the visible and infrared spectral regions. In addition, in high nutrient low chlorophyll regions, deposited mineral dust changes the global carbon budget by providing soluble iron to surface water to phytoplankton limited by the availability of soluble iron. Up to now, very little information has been gathered to describe the complex mixture of various minerals aggregated into dust. This information is essential to better describe the processes that affect climate. In one hand, the optical properties vary widely from mineral to mineral both in the visible and in the infrared and in other hand the mineralogical composition provides information to improve the estimate of soluble iron flux into the ocean. Therefore, incorporation of regionally and temporally varying size-resolved dust mineralogical composition into global climate models can decrease the current large uncertainty in the assessment of mineral dust radiative effect. It would also help for a better quantification of dust contribution insoluble iron flux delivery to the ocean’s surface. There is a large set of data on the mineralogical and chemical nature of the Earth's soils, which demonstrates the complex spatial variability of soil composition. Existing global data sets of soil properties currently include soil texture and types but they do not provide information on size-resolved mineralogical composition of the soil. To fill in the clear need for a new data set to provide this missing information, we present here an update at a global level of the soils mineralogical database provided by Claquin et al. in 1999. To build upon such database, we collected first a Database of soil surface mineralogy for 12 major minerals (quartz, feldspar, calcite, gypsum, illite, kaolinite, chlorite, vermiculite, smectite, hematite and goethite). Based on this information, we assigned a mean mineralogical composition for most soil types given by the FAO in the Harmonized World Soil Database. The main features of this mineralogical database are discussed. We highlight the ranges and the global mean value for the relative abundances each of these mineral in dust over present dust sources and regions that could have been sources during the Holocene. This paves the way to introduce the mineralogical composition in a General Circulation Model with a chemistry-aerosol module (LMDz-INCA). We will discuss the changes in radiative perturbation and atmospheric soluble iron when information about the detailed mineralogy is accounted for compared to a simulation when the averaged mineralogy is used.
AGU Fall Meeting Abstracts
- Pub Date:
- December 2010
- 0305 ATMOSPHERIC COMPOSITION AND STRUCTURE / Aerosols and particles;
- 0330 ATMOSPHERIC COMPOSITION AND STRUCTURE / Geochemical cycles;
- 0360 ATMOSPHERIC COMPOSITION AND STRUCTURE / Radiation: transmission and scattering