What Owing to its geographical position, Iceland’s marine realm is influenced by heat and salt from the Atlantic Ocean, the strength and position of the Subpolar Gyre and fresh cool water flowing southward from the Arctic. This unique array of currents provides the conditions for the economically viable marine ecosystems on which Icelanders rely. This project aims to decipher the history of oceanic changes in the Iceland Basin and the impact they had on the marine ecosystem. Why The oceanic configuration around Iceland varies on timescales from decades to millennia and while it sustains Iceland’s marine ecosystem, it also exposes it to risks that unprecedented perturbations in these configurations may pose. Information from abrupt climatic transitions, particularly past warm periods, is key to achieve an evidence-based approach for future predictions on how the ecosystem may respond to these perturbations. This project will aim to answer the questions a) what characterises the Icelandic oceanic and ecosystem impacts of global change? and b) do changes in the Icelandic marine realm predate or lag wider shifts in oceanic regime? Additionally, in the context of rising CO2 levels, the impacts of previous periods of ocean acidification and will be explored. How Newly recovered marine sediment cores provide a window into the past; these archives accumulate over time and contain tephra ejected from volcanoes and fossils such as foraminifera, organisms that dwell in sub-surface or bottom waters. Species have known environmental preferences and their calcium carbonate shells contain the geochemical fingerprint of the water in which they lived, making both qualitative (e.g. the water masses present) and quantitative (e.g. temperature and salinity) reconstructions possible. Foraminifera can be dated and will be used in conjunction with tephra layers of known age to provide a precise timeline of change in Iceland’s oceanic conditions and ecosystem, essential for assessing the impact of wider oceanic and atmospheric regimes back through time. SSR The project contributes to the Marine and Freshwater Research Institute research priority of climate variations and effects on the ecosystems and will provide paleo-data to inform efforts toward achieving the UN 2030 SDG 14: Life Below Water.