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Abstract |
Processes of cobalt (Co) entrainment from shelf sediments over the Kerguelen Plateau were studied during the KEOPS (Kerguelen Ocean Plateau compared Study) cruise data to assess the potential use of dissolved Co as a tracer for estimating natural iron fertilization over the plateau. Lateral advection and dissolution of Co contained in basalt sediments around Heard Island, a main source of lithogenic Co in the study area, were shown to imprint the process of surface enrichment over the plateau. Sedimentary Co inputs were estimated to be much higher than biological Co uptake in phytoplankton blooms, resulting in strong inputs of dissolved Co to surface waters, which allows the use of Co as an efficient tracer of sedimentary inputs. Based on a simple, steady state balance equation of the external input of dissolved iron over the plateau, the fertilization of iron inferred by using Co as a tracer of basalt sources is estimated to be 28 x102 ± 21 x102 ton y-1 in surface waters of the Kerguelen Plateau. This estimate is consistent with the advective iron supply matching with phytoplankton demand, strengthening our idea of using Co as a new tracer for the natural fertilization over the plateau. |
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