About the project
The depth in the ocean at which sinking organic carbon is remineralised back into CO2 is crucial to setting atmospheric CO2 concentration. In this project, you will explore the links between remineralisation depth, particle size and plankton size by building a simple mechanistic model on the basis of global datasets.
The size and shape of sinking particles is likely key to determining their remineralisation depth, as slower sinking particles are likely to be remineralised at a shallower depth. This leads to a “particle size-remineralisation feedback” hypothesis (Leung et al., 2021), such that under climate change-driven warming conditions plankton size structure shifts to smaller organisms, which leads to a shift to smaller sinking particles and so shallower remineralisation of organic carbon and nutrients. This latter would then increase nutrient availability in the upper ocean, which could drive increased primary production and carbon flux. The overall effect would be a dampening of the expected decline in the strength of the biological carbon pump as a result of climate change. If correct, then current IPCC projections, which omit this potential negative feedback, are overestimating reductions in future ocean carbon storage.
As part of this project we will:
- test this hypothesis by using existing public databases to explore the relationship between the size of phytoplankton and the size type and shape of sinking particles, and the links to remineralisation depth.
- build a simple mechanistic model incorporating (dis)aggregation, remineralisation and sinking to gain understanding of how different processes change the particle size spectrum.
- incorporate the effects of environmental factors such as temperature and oxygen concentration, so that we can make predictions about the impacts of climate change.
You will be embedded in a large international consortium project of carbon cycle scientists.