A slab ocean is the term used to refer to a simple model of ocean processes that describes the ocean as a motionless layer of water of fixed depth, typically between 50 and 100 m.
Modelling the exchange of heat and energy between the ocean surface and the atmosphere, and the physical processes in the ocean that control ocean circulation, is one part of a fully coupled Atmospheric-Ocean general circulation model (AOGCM). There are a range of different models of the Earth's ocean to choose from, ranging from the simple but computationally efficient 'swamp' models, to the complex but computationally demanding fully dynamic 3-D models. One step in the process of generating probabilistic projections in UKCP09, is to sample uncertainty in the atmosphere model parameters. Because the variation in these parameters is likely to be the largest source of uncertainty in climate projections through the 21st Century, variation in these parameters was sampled more densely than the ocean, sulphur, and carbon cycle components. To expedite this denser sampling of the parameter space, and the larger number of model simulations that would be required to provide a reasonable first order estimate of how the model behaviour varies when atmosphere parameters are varied, a less computationally demanding configuration of the Hadley Centre model was used, which uses a slab ocean model - HadSM3. The slab ocean model in HadSM3 is a simple thermodynamic model of the near-surface ocean (of fixed depth), which warms or cools in response to surface heat exchanges with the atmosphere, and in which horizontal and vertical transport within the ocean is prescribed.
- More details about the climate models used in UKCP09 are given in Box 2.1 in the UKCP09 Climate change projections report.
Find out more
- IPCC Fourth Assessment Report, Working Group 1 report The Physical Science Basis , Chapter 8