Svalbard-barents ice sheet instability enhanced delivery of reactive iron to the ocean

Iron (Fe) plays a key role in marine environments as a bio-limiting nutrient and a control on sedimentary burial of carbon and other nutrients. Sensitive glacial systems provide an important delivery mechanism for Fe to the ocean, but it is unknown how these glacial sources will change as ice retreats. Sedimentary records from the Yermak Plateau, proximal to the Svalbard-Barents Ice Sheet provide an opportunity to investigate how past glacial instability may have affected bioavailable iron delivery. Here we find that over the past 135 ka, pulsed reactive Fe export to the Yermak Plateau occurred at least 5 times, during intervals of ice sheet retreat or advance. Fe-rich layers preserve high contents of reactive Fe phases, some of which were likely bioavailable at the time of deposition. Glacial Fe from Svalbard may have been delivered either directly by meltwater plumes or through remobilization of Fe deposited in fjord and shelf sediments. The delivery of reactive Fe hundreds of kilometers offshore during these events indicates that ice sheet instability in modern settings could perturb high latitude nutrient cycles.