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DiatomPostDoc: Antarctic Ice, Nutrients and Diatoms in Tromsø

The Southern Ocean is an essential component of Earth´s carbon cycle, absorbing around 40% of the world ocean´s anthropogenic CO2 uptake. Atmospheric and ocean warming is enhancing meltwater discharge from some Antarctic Ice Sheet sectors and causing sea ice decline. These cryospheric changes are likely to amplify over the coming century, with the potential to influence important Southern Ocean marine ecosystems by altering nutrient and light availability. One of the main CO2 sinks of the Southern Ocean is the biological carbon pump, which is dominated by the activity of diatoms. Diatoms are large phytoplankton that produce silica shells and form extensive blooms, contributing to large carbon and silicon exports. Diatom production is limited by both iron and silicic acid in the Southern Ocean, which affect their potential to take up and export carbon to the deep ocean via complex coupling between biogeochemical cycles of carbon, silicon, and iron. Current estimates of the ice-sheet impact on Southern Ocean primary production vary widely. However, most of these models have a limited representation of the marine ecosystem of the Southern Ocean, in particular omitting the effect of iron availability on diatoms growth, life cycle and silicon-to-carbon elemental ratio. It is critical to improve understanding of the response of diatoms to changing cryospheric iron and silicon sources in Antarctica in order to predict the sensitivity of the Southern Ocean carbon cycle to past and future ice sheet change.

The postdoc fellow will employ the state-of-the-art ocean model NEMO coupled with the ocean biogeochemical model PISCES to study the effect of variable ice sheet and sea ice iron and silicon inputs on the marine plankton ecosystem, primary and export production in the Southern Ocean. The project will focus primarily on the impact of ice sheet-sourced nutrient inputs (e.g. subglacial meltwater, ice shelf melt and iceberg discharge) on diatom populations and how they influence their silicon-to-carbon ratio in relation to iron supply. Depending on the interests of the candidate, other aspects of Southern Ocean coupling with ice sheet meltwaters and associated nutrients or ecological trait modelling may be investigated. The postdoctoral fellow will be affiliated with Research Unit 5 within iC3, which aims to assess how the retreat of polar ice sheets will affect Earth’s future climate and marine ecosystems. The postdoctoral fellow is expected to be involved in all aspects of the research, including study design, planning, conducting research, data analyses, and publishing results.