DUST-BIOSPHERE-ATMOSPHERE COUPLING ON GLACIAL-INTERGLACIAL TIME SCALES

Mineral dust plays multiple roles in mediating physical and biogeochemical exchanges among the atmosphere, land and ocean: Besides its effects on the radiative balance of the atmosphere, mineral dust provides a key micronutrient source for both terrestrial and marine ecosystems. In addition, the radiative forcing of other aerosols, like sulphate, might be significantly altered by the presence of dust particles.

Here, we present first results of a new model approach to improve our understandings of dust-biosphere-atmosphere interactions within the Earth system. A recently developed dust emission model (including a prognostic vegetation-phenology scheme) was incorporated into a new aerosol scheme of the latest version of the Hamburg AGCM, ECHAM5. Compared to previous model studies, this new model set-up allows studying both vegetation-dust feedbacks and changes of the atmospheric circulation by an altered radiative forcing of mineral aerosol on a global scale, simultaneously.

Performing several LGM simulations prescribing appropriate glacial boundary conditions enables us to separate the impact of the various Earth's climate components (atmosphere, ocean, vegetation) on glacial dust emissions. We test whether the model correctly simulates dust deposition concentrations as seen in the various terrigeneous, oceanic and ice core records. In addition, our simulations enable us to estimate the possible impact of a changed atmospheric radiative balance by an increased glacial dust cycle on ocean and land surface temperatures during the LGM.