The atmospheric flux of trace elements and isotopes (TEIs) to the oceans can be extremely important in marine biogeochemical cycles, especially for bioactive trace elements including V, Mn, Fe, Co, Ni, Cu, and Zn. However, there are large uncertainties associated with converting rainfall and aerosol TEI concentrations into estimates of atmospheric deposition. By measuring ratios of TEIs to Be-7 in rainfall and aerosol samples, the atmospheric flux of TEIs can be calculated: Flux(TEI) = Flux(Be-7) * (TEI/Be-7), where the Flux(Be-7) is calculated from the uper ocean inventory of Be-7. Where the fractional solubility of aerosol TEIs in rainwater or surface seawater has been measured, the same ratio approach can be used to calculate the atmospheric flux of soluble TEIs. Soluble TEIs are expected to be intrinsically bioavailable to phytoplankton, and therefore can play an important role in biogeochemical cycling in the upper ocean.
We will present results from field campaigns in the Sargasso Sea (Bermuda) and the Arctic Ocean to test this approach.