Delivery and Recycling of Iron on the Eurasian Arctic Continental Shelf through the Last Deglaciation and Early Holocene

Ice sheets play major roles in ocean carbon and nutrient cycles; in particular, delivery of sediment and nutrients from melting ice sheets has been shown to have direct and indirect effects on biogeochemical cycling on the nearby seafloor. Changes to the delivery of bio-limiting nutrients such as Fe can affect ocean primary productivity. The Svalbard-Barents Ice Sheet (SBIS) existed on the Eurasian continental margin of the Arctic Ocean, building up and decaying multiple times, with its final collapse occurring between 20 and 10 ka. Sediment core records from this region were analyzed to determine the reactivity and bioavailability of Fe as the SBIS collapsed following the Last Glacial Maximum. Gravity cores were collected from the Barents Sea during the Nansen Legacy Paleo Cruise in November 2018. Here, we present results from sequential chemical extractions of sediment samples to isolate Fe phases based on their reactivity; the concentration of each phase in extracted solutions was measured using inductively coupled plasma optical emission spectroscopy. Targeted phases included poorly crystalline Fe oxyhydroxides, Fe associated with carbonate, crystalline Fe oxyhydroxides, and Fe in magnetite. Extraction results indicate that reactive Fe phases are dominated by Fe-carbonates and poorly crystalline oxyhydroxides, both of which show strong variation across the region and at different depths, while magnetite and crystalline Fe oxides are not dominant sources of Fe. These results will help elucidate how Fe is transported from ice sheets to shelf seas during deglaciation, and may provide insights into the effects of current ice sheet loss in Greenland and Antarctica on iron delivery.