Kiefer Forsch, Lisa Hahn-Woernle, Robert Sherrell, Joe Roccanova, Kaixan Bu, David Burdige, Maria Vernet, Katherine Barbeau

Glacial meltwater from the western Antarctic Ice Sheet is hypothesized to be an important source of cryospheric iron, fertilizing the Southern Ocean, yet its trace metal composition and factors which control its dispersal remain poorly constrained. Here we characterize meltwater iron sources in a heavily glaciated western Antarctic Peninsula (WAP) fjord. Using dissolved and particulate ratios of manganese-to-iron of meltwaters, porewaters, and seawater, we show glacial melt and subglacial plumes contribute to the seasonal cycle of bioavailable iron within a relatively undisturbed fjord. Ligand sources associated with the phytoplankton bloom and glaciers bind to iron, facilitating the solubilization of particulate iron downstream. Using a numerical model, we show subsurface subglacial plumes, enriched in labile particulate trace metals, derived from a chemically-modified crustal source, can supply the surface, and that prolonged katabatic wind events enhance export of meltwater out of the fjord. Thus, we identify an important atmosphere-ice-ocean coupling intimately tied to coastal iron biogeochemistry and primary productivity along the WAP.