Details of Award
NERC Reference : NE/N007824/1
Ocean Biogeochemical Optimisation in ESMs (OBOE)
Training Grant Award
- Lead Supervisor:
- Professor S Khatiwala, University of Oxford, Earth Sciences
- Grant held at:
- University of Oxford, Earth Sciences
- Science Area:
- Atmospheric
- Earth
- Freshwater
- Marine
- Terrestrial
- Overall Classification:
- Marine
- ENRIs:
- Biodiversity
- Environmental Risks and Hazards
- Global Change
- Natural Resource Management
- Pollution and Waste
- Science Topics:
- Climate & Climate Change
- Biogeochemical Cycles
- Ecosystem Scale Processes
- Ocean - Atmosphere Interact.
- Numerical Analysis
- Abstract:
- As one of the principal reservoirs of CO2, the ocean plays a crucial role in the carbon cycle and in regulating Earth's climate. Understanding and modelling the interconnections between the ocean carbon cycle and climate is therefore critical for robust estimates of future climate change. A principal challenge in this regard is the absence of well-established sets of equations governing the behavior of marine ecosystems, which play a key role in ocean carbon dynamics. Consequently, fundamental processes, such as the formation and sinking of organic matter from the surface mixed layer into the ocean interior (known as the "biological carbon pump" or BCP), are crudely parameterised. Improving the representation of these processes in global ocean biogeochemical models, embedded within Earth System Models (ESMs) used to project future climate change, is thus an important goal of current research and of this project in particular. Specifically, we seek to evaluate and improve the performance of MEDUSA (Model of Ecosystem Dynamics, nutrient Utilisation, Sequestration and Acidification), the ocean biogeochemical model in the next generation Met Office/NERC Earth system model (UKESM), currently under development. MEDUSA, developed by Dr. Andrew Yool and colleagues at NOC, models the interaction between macro- and micro-nutrients, phytoplankton and carbon. MEDUSA represents these processes via a range of parameterisations and associated parameters, which can have significant impact on key processes controlling marine uptake of atmospheric CO2. We seek to "tune" these parameters to better fit observations. To achieve this a number of challenges need to be addressed. First, because of the complex interaction between biogeochemistry and circulation, model sensitivities vary both globally as well as regionally (e.g., Atlantic v Pacific), and also with respect to the model field (e.g., nutrients v primary production). Second, evaluating the performance of global models is prohibitively expensive as every parameter change requires integrating the model for several thousand simulated years to equilibrium before the model can be compared with observations. As a result there have been very few attempts at systematically optimising the performance of models such as MEDUSA. To overcome this, the student will exploit a fast "offline" tracer simulation scheme and recently-developed mathematical optimisation techniques to optimise MEDUSA, a first for a global biogeochemical model of this complexity, especially one used in a state-of-the-art ESM. Key outcomes of this project include (1) an estimate of MEDUSA's sensitivity to various parameters and thus the relative importance of key processes that affect the strength of the BCP such as remineralization, sinking and settling of organic and inorganic matter, nutrient and light limitations, microbial degradation of dissolved organic carbon and uptake/growth rates of ocean biology; (2) an optimal set of parameters that minimizes the model-observation cost function built on several fields, such as air-sea CO2 flux, primary production, chlorophyll, nutrient and oxygen distributions, and carbon export; and (3) a quantitative assessment of the impact of parameter optimisation on projections of Earth system change made by UKESM1 (e.g., to ocean CO2 uptake and equilibrium climate sensitivity). Our project brings together ocean biogeochemists, a mathematician and an Earth system modeller and the student will benefit from working actively with scientists from several disciplines, including the UKESM model development core group. S/he will receive training in not only marine biogeochemical and Earth system modelling, but also in high performance computing, numerical analysis and mathematical optimisation techniques with broad applicability in science and engineering. The student will also benefit from courses offered through Oxford's NERC-funded Environmental Science DTP as well as the Mathematical Institute.
- NERC Reference:
- NE/N007824/1
- Grant Stage:
- Completed
- Scheme:
- DTG - directed
- Grant Status:
- Closed
- Programme:
- Industrial CASE
This training grant award has a total value of £86,776
FDAB - Financial Details (Award breakdown by headings)
| Total - Fees | Total - RTSG | Total - Student Stipend |
|---|---|---|
| £16,957 | £11,000 | £58,822 |
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