Volcanic ash mobilization
The MILLENNIUM project revealed that the dynamics of the carbon cycle and the feedback between the carbon cycle and the climate on the centennial time scale are not yet fully understood. Therefore, new model components for simulating the carbon cycle are currently being developed and tested, including a representation of the methane cycle and permafrost carbon release. This working group focusses on volcanic ash mobilization. Volcanic ash mobilization on land may represent a major post-eruption source of volcanic ash aerosols e.g. available for land and for ocean fertilization where it may stimulate the biological CO2 pump.
Preliminary results for a one-year simulation period look promising. The accumulated ocean deposition in September 1992 makes up about 2/3 of the total deposition with considerable ash deposition into the Atlantic sector of the Southern Ocean. Ash deposition nearby the Falkland Islands of about 1 g ash/m2/y is comparable to estimated mineral dust deposition fluxes over the Falkland Islands. Assuming an iron content of 200 nmol Fe/(g ash), the iron deposition fluxes associated with volcanic ash remobilisation into the Southern Ocean slightly exceed estimated iron deposition fluxes associated with mineral dust. However, the iron content of aged volcanic ash is rather uncertain, so that this statement should be taken as very preliminary . Currently, a mass-conserving remobilisation scheme including the mass of the deposit is being tested.