Dust deposition fluxes at the gateway to the Southern Ocean: investigating the use of lithogenic tracer measurements in aerosols collected in Tasmania, Australia

Abstract. Australia contributes a significant amount of dust-borne nutrients (including iron) to the Southern Ocean, which can stimulate marine primary productivity. A quantitative assessment of the variability of dust fluxes from Australia to the surrounding ocean is therefore important for investigating the impact of atmospheric deposition on the Southern Ocean’s carbon cycle. In this study, lithogenic trace metals (aluminium, iron, thorium and titanium) contained in aerosols collected between 2016 and 2021 from kunanyi/Mount Wellington in lutruwita/Tasmania (Australia) were used to estimate dust deposition fluxes. Lithogenic fluxes were calculated using each tracer individually, as well as an average using all four tracers. This latter approach enabled an assessment of the uncertainty associated with flux calculations using only individual tracers. Elemental ratios confirmed the lithogenic nature of each tracer in aerosols when compared with both Australian soil samples and the average Earth’s upper continental crust. Determined lithogenic flux estimates were consistent with a regular dust deposition peak during the austral summer, in line with the dust storm season in the southeast of Australian, and a low atmospheric deposition in winter. This study provides an insight into the seasonal and interannual variability of dust deposition fluxes from the southeast of Australia based on aerosol sample measurements. This information will enhance our understanding of nutrient-bearing dust deposition to the Australian sector of the Southern Ocean and may prove useful in refining modelling estimates of southern hemisphere atmospheric deposition fluxes and their subsequent impact on global biogeochemical cycles.