Séminaire
The Kuroshio and the Gulf Stream, and their respective extension jets, are oceanic western boundary current systems known to play an important role in climate. The Kuroshio Extension jet (KE) in particular exhibits an impressive decadal variability of bimodal character well revealed by satellite altimeter data available from the early nineties. This has stimulated the development of several model studies of varying complexity aimed at clarifying the dynamical mechanisms producing such variability: the intrinsic origin of the latter was supported by relatively realistic model implementations, leading to significant model-data comparisons.
To analyze the KE intrinsic low-frequency variability, some low-order models were also developed. The underlying philosophy is that of investigating the dynamical problem on a more qualitative and fundamental level by using a much less realistic but extremely agile mathematical tool if compared with the original full problem. In this seminar a series of numerical model studies based on a spectral quasigeostrophic model with four degrees of freedom specifically developed for the KE are presented and discussed in the general context of dynamical systems theory. To study the intrinsic variability steady forcing is imposed, but stochastic and periodic components are also added to the forcing to investigate further relevant dynamical aspects.