The response of the separated western boundary current to a seasonally varying wind stress is studied in a 2.5-layer model where the second layer outcrops. The model is eddy permitting with a resolution of one-sixth of a degree, and the geometry of the basin is idealized. The response is studied for two mean states: the first one is only wind driven, whereas the second one takes into account the existence of a meridional overturning circulation. The separation latitude and the mean path followed by the separated western boundary current are shifted northward of approximately 2° when the overturning circulation is added. Though the mean states are significantly different, the variability of the current shows quite similar characteristics. The seasonal lateral shifts of the outcrop line always remain small, scarcely exceeding 0.2°. On the contrary, interannual shifts that can peak up to approximately 1° to 2° are observed. This variability is associated with the development of nonlinear waves along the outcrop line. The corresponding timescales extend on a broad range of periods (longer than approximately 4 years), with an energy maximum depending on the set up. A simple analytical model derived from the 2.5-layer model allows us to explain which mechanism drives the propagation of these waves.
Sirven, Jérôme, Sabine Férvrier, and Christophe Herbaut. 2015. "Low-frequency variability of the separated western boundary current in response to a seasonal wind stress in a 2.5-layer model with outcropping." Journal of Marine Research 73, (5). https://elischolar.library.yale.edu/journal_of_marine_research/409