Sources, transport and reaction pathways of iron from terrestrial areas and coastal sediments of South Georgia into the adjacent Southern Ocean

The Southern Ocean is a high nutrient low chlorophyll region, where primary productivity is limited by the availability of iron (Fe). Iron is an essential nutrient for phytoplankton growth. Large phytoplankton blooms during austral summer fueled by Fe have been observed around ocean islands such as South Georgia in the sub-Antarctic. South Georgia is located in the Atlantic Sector at the northeastern boundary of the Scotia Sea. The eastward-flowing Antarctic Circumpolar Current loops around the island, generating the distinctive hydrographic conditions that drive large phytoplankton blooms in the northwestern Georgia Basin. These blooms make the region a major sink for atmospheric carbon dioxide. The effects on the biological carbon pump remain difficult to assess, partly because Fe fluxes to the Southern Ocean are still poorly constrained. Varying Fe fluxes into the Southern Ocean are expected due to glacier retreat and enhanced freshwater run-off in polar regions and may change under global warming. The various potential Fe sources, including bedrock weathering, dust deposition, meltwater, and benthic fluxes, are unlikely to contribute uniformly or respond equally to environmental change. A clearer understanding of the dominant Fe transport and reaction pathways in (sub)polar coastal regions is therefore needed to constrain these fluxes.