Propagation of Kuroshio Extension Meanders between 143° and 149°E

Abstract

Abstract A two-dimensional array of current- and pressure-recording inverted echo sounders provided synoptic measurements of the upper and deep fluctuations in the Kuroshio Extension between 143° and 149°E with mesoscale resolution. Downstream-propagating meanders with periods of 3–60 days were always present between June 2004 and September 2005. Propagation speeds were estimated by two methods: spectral analysis of path displacements and complex empirical orthogonal functions (CEOF) analysis of along-path anomalies. The two methods produced similar results. Phase speeds increased smoothly from 10 km day−1 (0.12 m s−1) for meanders with wavelengths and periods [λ, T] = [420 km, 40 days] to 35 km day−1 (0.41 m s−1) for [λ, T] = [220 km, 6 days] meanders. This empirically derived dispersion relationship is indistinguishable from that obtained for Gulf Stream meanders downstream of Cape Hatteras. The deep ocean was populated with remotely generated, upstream-propagating eddies composed of a nearly depth-independent current structure. Upper meanders and deep eddies jointly spun up when they encountered each other with the deep eddy offset about a quarter wavelength ahead of the upper meander. Subsequently, as the upper and deep features moved past each other and the vertical offset changed, intensification ceased.