Iron in land-fast sea ice of McMurdo Sound derived from sediment resuspension and wind-blown dust attributes to primary productivity in the Ross Sea, Antarctica
2013
de Jong, Jeroen | Schoemann, Véronique | Maricq, Nathalie | Mattielli, Nadine | Langhorne, Patricia | Haskell, Timothy | Tison, Jean-Louis
We present high-accuracy isotope dilution mass spectrometry data on dissolved Fe (DFe), total dissolvable Fe (TD-Fe) and refractory particulate Fe (REF-Fe) concentrations in snow, land-fast ice and under-ice seawater, sampled at six sites from 14 to 22 January 2003 in Erebus Bay, McMurdo Sound. We also report refractory particulate Fe/Al ratios to help identify Fe sources. Iron concentrations in land-fast ice and snow were two to three orders of magnitude higher than the underlying seawater. Seawater Fe increased in all fractions over the sampling period (8days), likely caused by sediment resuspension induced by spring tides, which occur twice a month. We propose that entrainment of wind-blown material and sediment-derived Fe is the most important pathway for high Fe concentrations in land-fast ice in McMurdo Sound. Iron fluxes from the sediment were estimated and could fully account for the Fe inventory of the land-fast ice. Wind-blown lithogenic material in the snow on the land-fast ice makes up for 14–68% of the total Fe inventory of the sea ice. It does not appear to penetrate into the sea ice proper as snow-ice forming conditions were not present. The sources of these wind-blown particles are, in decreasing order of strength, the McMurdo Ice Shelf, the Dry Valleys, Ross Island and Erebus volcanic emissions. The data suggest that the usual spring breakup of sediment-laden land-fast ice to the Ross Sea may have a significant potential fertilizing effect on the waters of the Ross Sea Polynya. This is illustrated by the strong diminution of primary production in the Ross Sea Polynya due to the blockade of the annual sea ice breakout by the giant icebergs B-15 and C-19 during the austral summer of 2003.
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