Abstract

Iron is an essential nutrient for marine primary producers yet is the primary (co-)limiting nutrient in much of the Southern Ocean. With continued regional warming, the West Antarctic Peninsula, home to 676 glaciers covering 95,000 km2, provides large fluxes of glacially sourced meltwater to the marine environment. Understanding glacier-water column interactions is important in evaluating the role of glaciers in Southern Ocean iron and macronutrient cycling, and how this may change as regional atmospheric and oceanic warming continues. Using short-lived radium isotopes, stable oxygen isotopes, and physical parameters such as temperature and salinity, we determine the influence of sediment inputs and meltwater contributions upon water column macro and micronutrient distributions within glacially-influenced bays¹.

For iron, we observe high dissolved (4 – 8 nM) and particulate (30 – 580 nM) concentrations proximal (0.5 – 12 km) from the glacier edge. Recent studies indicate that iron-rich particulates can be highly bioavailable, if rich in iron(II) (ferrous iron)[2] [3]. Using Scanning Transmission X-ray Microscopy (STXM) and X-ray Near Edge Spectroscopy (XANES), we investigate the iron speciation and co-location with carbon to infer the potential bioavailability of iron in glaciogenic particulates. We observe a high iron(II) component of iron-rich particles averaging 40%, coupled with apparent stabilisation of iron(II) through organic carbon complexation. Transport of particulate iron beyond the near-shore is also observed, and so we infer that the West Antarctic Peninsula is an important source of potentially bioavailable particulate iron across the wider shelf.

1. Jones, R.L., et al., Continued glacial retreat linked to changing macronutrient supply along the West Antarctic Peninsula. Marine Chemistry, 2023. 251: p. 104230. 2. Shoenfelt, E.M., et al., High particulate iron (II) content in glacially sourced dusts enhances productivity of a model diatom. Science advances, 2017. 3(6): p. e1700314. 3. Wyatt, N.J., et al., Phytoplankton responses to dust addition in the Fe–Mn co-limited eastern Pacific sub-Antarctic differ by source region. Proceedings of the National Academy of Sciences, 2023. 120(28): p. e2220111120.