Investigation of the Dynamic Estuarine and Marine cycling of Nickel

ended

Nickel (Ni) is closely associated with export of carbon (C) from the surface ocean to the deep marine environment, as it acts as a micro-nutrient. This makes Ni a big part of the ocean-atmosphere C cycle. There is currently a major gap in our understanding of the marine cycling of Ni, with key input and output fluxes unaccounted for. The work proposed for this Individual Fellowship will (A) bridge this gap, and (B) utilise the resulting knowledge to reconstruct glacial-interglacial variations in Ni isotopes of seawater. To answer these objectives the project is divided into four sections: (1) estuarine production of desorbed Ni as key input of Ni to the ocean, (2) sediment-pore water redox conditions as major sink of Ni in marine sediments, (3) detailed analysis of sediment-pore water interaction in euxinic and ferruginous salt-marsh cores, and (4) changes in the sources and sinks of Ni on glacial-interglacial time scales. Ni has a short residence time in the ocean and is therefore useful for tracking rapid shifts in surface ocean productivity and export of C to the deep sedimentary archive. A record of temporal evolution of Ni stable isotopes from marine sedimentary archives therefore has the potential to elucidate the forces controlling the Earth’s climate on glacial-interglacial timescales. This will be achieved by a multifaceted approach including archived sample analysis, sample collection during internationally collaborative fieldwork campaigns, cutting-edge high-precision isotope analysis and numerical and analytical modelling. The knowledge gained during the fellowship will be instrumental for the exploitation of Ni isotopes as a tool to trace the feedbacks between past climatic variability, primary production and OC burial and preservation.