Dissolved iron concentration in the recent snow of the Lambert Glacial Basin, Antarctica

Abstract

Iron (Fe) is a limiting nutrient in the Southern Ocean (SO), and the input of atmospheric iron may fertilize the SO. Therefore, it is important to estimate the deposition and solubility of atmospheric iron in the Antarctica. For this purpose, we measured iron in a 3 m snow pit from the Lambert Glacial Basin (LGB), covering the period 2012–2017. We estimated an average annual dissolved iron (DFe) flux of 1.29 × 10−3 mg m−2 a−1 and an average total dissolvable iron (TDFe) flux of 0.14 mg m−2 a−1 for this site. The atmospheric fractional iron solubility (FFS) ranges from 0.01% to 21.47% (mean value 1.20%) and shows an inverse hyperbolic relationship with the TDFe concentration. This relationship suggests that atmospheric iron in the LGB comes from a mixture of mineral dust with low FFS and aerosol with high FFS (e.g. combustion aerosols and volcanic ash). Based on the mean value of the atmospheric iron deposit fluxes from both this and previous studies, we estimated that ∼0.013 Gg of dissolved atmospheric iron could be deposited in the seasonal sea ice zone (SSIZ) every year, potentially supporting an annual algal production of ∼2.52 × 1012 g C in the Antarctic coastal water. This is less than 1% of the annual primary production in the SSIZ of the SO estimated from satellite data. The result shows that, compared with other sources of iron such as iceberg and glacier meltwater, the dissolved atmospheric iron has very small effect on the annual primary production in the SSIZ.