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gfdl's home page > gfdl on-line bibliography > 1995: Natural Climate Variability on Decade-to-Century Time Scales, 355-362; Discussion: 363-364
A stochastic model of North Atlantic climate variability on decade-to-century time scales
| Bryan, K., and F. C. Hansen, 1995: A stochastic model of North Atlantic climate variability on decade-to-century time scales. In Natural Climate Variability on Decade-to-Century Time Scales, Washington, DC: National Academy Press, 355-362; Discussion: 363-364. |
| Abstract: A conceptual model of North Atlantic climate variability is based on a simple two-box representation of the thermohaline circulation of the ocean. The model is linearized about a basic state, which corresponds approximately to the present ocean climate of the North Atlantic. Stochastic forcing, which represents the random effects of atmospheric cyclones and anticyclones passing over the ocean surface, drives the model away from its equilibrium state. The model transforms this stochastic forcing with equal power at all frequencies into a red-noise response in ocean temperature and salinity. At frequencies less than the thermohaline circulation's time scale, the solution is an equilibrium response and the amplitude of model ocean climate becomes independent of frequency. |
| Damping of salinity variations in the model is due to the thermohaline circulation. Ocean temperature variations are damped by both the thermohaline circulation and interaction with the atmosphere at the ocean surface. |
| The model illustrates how air-sea interaction involving the thermohaline circulation could produce a continuous spectrum without peaks. Stochastic forcing amplitudes corresponding to the climate of the last few thousand years produce a nearly linear response of the model. Large perturbations of the hydrological cycle typical of the close of the last ice age produce a chaotic response. |