Seasonal axis migration of the upstream Kuroshio Extension associated withstanding oscillations

The TOPEX/Poseidon altimeter data from October 1992 to October 1998 are ana lyzed to investigate the seasonal cycle of the sea surface height (SSH) in the upstream region of the Kuroshio Extension. After removing steric height changes caused by surface buoyancy fluxes, two maxima of the seasonal SSH amplitude are found around the crest and trough of the quasi-stationary mea nders as standing waves, accompanied with nodes of amplitude minima. Season al variations are identified in the subsurface temperature at 400 to depth similar to those of SSH in amplitude and phase. Associated with the standin g waves, the current follows a straight path in fall and then changes to a meandering path in spring. From a composite map of the seasonal Kuroshio Ex tension axes, nodes of minimum displacement are found. One node is located over the Izu Ridge, while the others are located in the areas where meridio nal acceleration is large. The seasonal axis migration of the upstream Kuro shio Extension is regulated by these nodes.