Iron in East Antarctic snow: Implications for atmospheric iron deposition and algal production in Antarctic waters

Abstract

To evaluate the deposition and solubility of aerosol iron in the Antarctic seasonal sea ice zone (SSIZ), iron was measured in snow samples collected from three areas in the SSIZ (Prydz Bay, Dumont d'Urville Sea and Ross Sea) and one continental area (Princess Elizabeth Land) of East Antarctica. Concentrations of total‐dissolvable iron (that soluble at pH ∼2) ranged from 20–2950 pg g−1, with the lowest concentrations measured in snow from the Dumont d'Urville Sea. Using estimates of snow accumulation rates, we calculate atmospheric iron deposition fluxes of 0.017–0.11 mg m−2 yr−1 (0.30–2.0 µmol m−2 yr−1), which are generally lower than previously published estimates. Measurements of iron in filtered meltwaters of snow samples from Prydz Bay and Princess Elizabeth Land suggest that ∼10–90% of the total atmospheric iron is readily soluble. Assuming our results to be broadly representative of atmospheric deposition over seasonally ice‐covered, high‐nutrient Antarctic waters, we use our mean estimates of atmospheric iron deposition (1.1 µmol m−2 yr−1) and solubility (32%) to calculate that atmospheric iron potentially supports annual phytoplankton production of 1.1 × 1012 mole C in the Antarctic SSIZ, which is less than 5% of the estimated total annual primary production in this ocean region.