Response of the Ocean Biogeochemistry and Isotopes to Different Aerosol Iron Fluxes

Changes in the characteristics of the iron cycle during the Last Glacial Maximum (LGM) could partly explain the lower atmospheric CO2 and the change in isotope distributions observed during this period. Recent modeling works have produced a number of atmospheric dust deposition fluxes for both the pre-industrial (PI) and LGM periods, finding considerably higher fluxes in the LGM. The aim of this work is to quantify the effect on the ocean biogeochemistry of soluble iron deposition fields calculated from these fluxes. We calculate soluble iron deposition from the dust fluxes based on an empirical relationship and use them to force an isotope enabled ocean biogeochemistry model, coupled to a climate-ocean circulation model. We evaluate the different PI iron depositions by comparing PI simulations from our model to modern observations. Modeled dissolved iron concentrations are compared to observations from GEOTRACES. We then use the LGM depositions to study the effect of higher iron fluxes on the ocean biogeochemistry, and determine to what extent these changes are able to explain reconstructed atmospheric CO2 and carbon and nitrogen isotope distributions from this period.