Details of Award
NERC Reference : NE/L005166/1
Implementation and optimisation of geostrophic eddy parameterisations in ocean circulation models
Grant Award
- Principal Investigator:
- Dr JR Maddison, University of Edinburgh, Sch of Mathematics
- Co-Investigator:
- Professor DP Marshall, University of Oxford, Oxford Physics
- Grant held at:
- University of Edinburgh, Sch of Mathematics
- Science Area:
- Marine
- Overall Classification:
- Marine
- ENRIs:
- Environmental Risks and Hazards
- Global Change
- Science Topics:
- Climate & Climate Change
- Ocean Circulation
- Abstract:
- The global ocean is populated by a vigorous and dynamic eddy field. This eddy field has a significant impact on the wider structure of the ocean circulation, but it is computationally extremely expensive to resolve directly. While recent simulations have allowed for direct eddy resolving calculations to be performed, equilibrated eddy resolving calculations are unlikely to become routine at any point in the near future. There therefore remains an urgent need for eddy parameterisation schemes, which aim to capture the aggregated effects of the eddy field in coarse resolution numerical models. The development of ocean eddy closures remains a formidable challenge. However, one can apply fundamental principles in order to rule out eddy closures which lead to unphysical behaviour. For example, the eddies require energy in order to mix ocean properties, and must observe the principle of conservation of momentum. A somewhat more subtle property is that ocean eddies must, on average, mix out gradients in the fluid potential vorticity. Eddy parameterisations which fail to observe these constraints can be ruled out as a possible solution for the underlying eddy dynamics. A particularly important challenge for ocean eddy parameterisations is the accurate reproduction of ocean sensitivities to forcing changes. These responses have implications for the long term ocean response to climate change. Recent studies indicate that the Southern Ocean may exhibit reduced responses to wind forcing changes when the influence of the eddies is well sufficiently resolved. Coarse resolution models, which parameterise the eddies and do not resolve them directly, often give wildly incorrect predictions for the ocean responses. This study proposes the implementation of a suite of new and existing ocean eddy parameterisations. The parameterisations are to be implemented in a simplified context (in a "quasi-geostrophic" model), and then in a full ocean circulation model. This research has three key novel aspects. First, optimisation techniques will be employed in order to assess the performance of the closures in the simplified quasi-geostrophic case. These techniques can be used to identify the best possible configuration of a given eddy parameterisation scheme, enabling the best-case performance of the scheme to be rigorously identified. This will provide a robust comparison of a broad range of possible approaches for eddy parameterisation. Secondly, the research aims to impose the three physical principles, imposed by energetic constraints, momentum conservation, and the need to mix potential vorticity, simultaneously. Thirdly, the research will investigate the performance of a broad range of parameterisations in determining the ocean sensitivity to wind forcing changes. Particularly important questions to be addressed are: How important are the fundamental physical constraints in controlling the ocean eddy dynamics? Can the restoration of these constraints in ocean eddy parameterisation schemes lead to improved coarse resolution simulations?
- NERC Reference:
- NE/L005166/1
- Grant Stage:
- Completed
- Scheme:
- Standard Grant (FEC)
- Grant Status:
- Closed
- Programme:
- Standard Grant - NI
This grant award has a total value of £286,937
FDAB - Financial Details (Award breakdown by headings)
| DI - Other Costs | Indirect - Indirect Costs | DA - Investigators | DI - Staff | DA - Estate Costs | DA - Other Directly Allocated | DI - T&S |
|---|---|---|---|---|---|---|
| £4,338 | £84,218 | £30,191 | £120,902 | £35,168 | £88 | £12,033 |
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