Dissolved and Particulate Metals Distribution in Antarctic Sea Ice and their Role in Tracing Iron Sources

Samples were collected during the IPY-GEOTRACES Sea Ice Physics and Ecosystem Experiment (SIPEX) voyage to assess the spatial and seasonal distributions of molybdenum (Mo), cadmium (Cd), barium (Ba), aluminium (Al), chromium (Cr), manganese (Mn), copper (Cu) and zinc (Zn) in late winter/early spring 2007 in the australian sector of East Antarctica. Total dissolved (< 0.2 µm) and particulate (> 0.2 µm) concentrations were measured by MS-ICP-MS in sea ice, snow and seawater samples. Results show that the concentrations of particulate metals were higher in sea ice than in snow and seawater, except for Mo and Cr. Vertical profiles were mostly C-shaped for both the particulate and dissolved metals fractions. Higher particulate Fe, Mn and Al concentrations in land-fast ice suggest a signal from Antarctica’s shelf sediments. Particulate Fe to Al molar ratios = 0.33 mol:mol in land-fast ice would corroborate the terrigenous origin. On another hand, no enrichment in dissolved metals was observed in land-fast as compared to pack ice. This would suggest that (i) spatial variability does not seem to strongly control the distribution of dissolved metals in East Antarctic sea ice and (ii) sediment re-suspension would mainly contribute to incorporate metals (Al, Mn and Fe) in sea ice under the particulate form, whilst being a weak source of dissolved metals. Our results would also confirm that the main flux of trace metals to Antarctic sea ice comes from below (i.e., water column), not from above (i.e., continental dusts). This study finally investigates the potential limitation and/or toxicity status for algal development in East Antarctic sea ice as well as estimates trace metal fluxes during spring melt. This innovative research highlights the significance of the sea ice reservoir in triggering algal bloom and the urgent need to integrate sea ice related processes in global ocean models.