Frequent resuspension of glaciomarine coastal sediments as an important source of reactive iron to the West Antarctic Peninsula

Abstract. Southern Ocean primary productivity is often limited by the availability of the essential micronutrient iron (Fe), and sediment-derived fluxes of Fe from the Antarctic shelf have been linked with hotspots of productivity. Glacial meltwater along the West Antarctic Peninsula delivers significant volumes of Fe-rich glacially weathered material to shelf surface sediments. The mechanisms that supply a bioavailable flux of Fe from shelf sediments are not well understood. This study simulated the resuspension of oxic sediments in the nearshore glaciated West Antarctic Peninsula across King George Island, Anvers Island, and Adelaide Island. Glaciomarine surface sediments were rich in highly reactive Fe (2 – 9 mg Fe g^-1), and onboard mesocosm resuspensions produced a sustained bottom water enrichment in dissolved Fe of 4 – 12 nM over the 48 h experiment duration.

Additional acoustic doppler current profiler and acoustic backscatter turbidity data indicate ongoing resuspension of sediment in the region. Our observations support a flux of highly reactive Fe of 5–20 µmol cm^-2 per sediment by resuspension within the glaciated fjords studied, exceeding recent outer shelf estimates of 0.7 µmol cm^-2. Reactive oxic nearshore sediments therefore represent an important supply of colloidal and reactive particulate Fe to the Antarctic shelf water column, the export of which can potentially supply bioavailable Fe to Fe-limited Southern Ocean waters.