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Cambridge NERC Doctoral Training Partnerships

Graduate Research Opportunities

Lead Supervisor: John Taylor, Applied Mathematics and Theoretical Physics

Co-Supervisors: Sasha Turchyn, Earth Sciences and Oscar Branson, Earth Sciences

CASE Partner: Running Tide Technologies

Brief summary: 
Study the interaction between natural and artificial kelp forests and ocean physics and biogeochemistry and the potential for carbon drawdown and sequestration
Importance of the area of research concerned: 
The ocean is an enormous natural carbon reservoir, containing far more carbon than the atmosphere, vegetation, and soil combined. Through natural processes, the ocean has absorbed about 25% of the carbon emitted through the burning of fossil fuels and land-use changes. Waters in the deep ocean (>1000m depth) take hundreds to thousands of years to reach the ocean surface and therefore strategies to remove carbon from the atmosphere and store (or sequester) it in the deep ocean have the potential to mitigate the impacts of climate change on a global scale. Kelp (brown macroalgae) can grow very rapidly, up to 2 feet per day. As kelp grows it removes dissolved carbon from the surrounding seawater and uses the carbon to generate biomass. The resulting decrease in dissolved carbon in the ocean is partially replaced by atmospheric CO2. It has been suggested that macroalgae naturally sequester large quantities of carbon through export to the deep ocean and burial in sediments [1] and that macroalgae farms and marine reforestation could play a significant role in climate change mitigation and adaptation strategies [2].
Project summary : 
Kelp forests interact with ocean physics and biogeochemistry. For example, upwelling currents or flow through the kelp canopy can replenish essential nutrients that support kelp growth, kelp induces drag and generates turbulence that alters these currents, and kelp competes with phytoplankton (microalgae) for nutrients and light. Quantifying the growth and carbon sequestration potential associated with kelp forests requires an understanding of the interaction between fluid dynamics and biogeochemistry. The project will couple a new model for giant kelp (Macrocystis pyrifera) with an existing model for ocean fluid dynamics [3]. The combined model will then be used to study the flow through the kelp forest canopy, turbulence and mixing, nutrient and carbon transport, and ultimately quantify the carbon drawdown associated with kelp forests.
What will the student do?: 
The student will start by developing a mathematical model for giant kelp, guided by existing models and datasets. The model will input environmental conditions (e.g. temperature, nitrate concentration, light levels) and output the rate of change in kelp biomass and the associated carbon and nitrogen. The next step will involve coupling the kelp growth model with an existing ocean large-eddy simulation (LES) code [3]. The student will use the coupled models to simulate the flow within and around the kelp canopy and study the interaction between the kelp forest and currents driven by wind, waves, and tides. The combined model will also be used to design the layout of artificial kelp forests to maximize growth and restore ecosystems. Lastly, the student will couple a biogeochemical model with the kelp growth model and LES [3]. By simulating the response of the biogeochemical system, the three coupled models will allow us to quantify the change in primary production and carbon export associated with the kelp forest. This step will be critical in order to estimate the carbon drawdown and sequestration associated with kelp forests.
References - references should provide further reading about the project: 
[1] Krause-Jensen, D., Lavery, P., Serrano, O., Marbà, N., Masque, P. and Duarte, C.M., 2018. Sequestration of macroalgal carbon: the elephant in the Blue Carbon room. Biology Letters, 14(6), p.20180236.
[2] Duarte, C.M., Wu, J., Xiao, X., Bruhn, A. and Krause-Jensen, D., 2017. Can seaweed farming play a role in climate change mitigation and adaptation?. Frontiers in Marine Science, 4, p.100.
[3] Whitt, D.B., Lévy, M. and Taylor, J.R., 2019. Submesoscales enhance storm‐driven vertical mixing of nutrients: insights from a biogeochemical large eddy simulation. Journal of Geophysical Research: Oceans, 124(11), pp.8140-8165.
You can find out about applying for this project on the Department of Applied Mathematics and Theoretical Physics (DAMTP) page.
Dr Oscar Branson
Department of Applied Mathematics and Theoretical Physics PhD Admissions
Dr John Taylor