A map of recent terrigenous fluxes to Southern Ocean sediments: Application of 230Thxs-normalized 232Th as a dust flux tracer

Dust fluxes to the ocean have been identified as one of the controlling factors of marine bioproductivity. Therefore, both palaeoceanographical studies as well as numerical models of ocean biogeochemistry aim at quantifying the effect of dust onto iron-limited marine ecosystems, especially the Southern Ocean. However, recent dust fluxes to the open ocean are still not well constrained. This applies in particular to the Southern Ocean, where few observational data are available. The limited information about absolute dust fluxes and their effect on productivity means a serious obstacle for linking the sedimentary record to our understanding of ocean biogeochemistry as reflected in models. Therefore, a better knowledge about recent dust fluxes to marine sediments can provide a link between models and palaeoceanographic data. Here, we present a map of recent terrigenous fluxes to the sediments of the Southern Ocean. We use 230Thxs- normalized fluxes of 232Th to calculate lithogenic fluxes from a comprehensive sample set of sediment surfaces.
In addition to a map of dust fluxes in the Atlantic and Pacific sector of the Southern Ocean, our presentation will include an
example for the generation of the 232Th-signal in the ocean,
studied by means of water column measurements in the dustaffected subtropical Atlantic. We also present evidence for the
close correlation between dust-transported biomarkers (n-alkanes) and inorganic proxies like 232Th.