Lagrangian statistics in the central North Pacific

Abstract

Lagrangian integral scales, diffusivities, dispersion and velocity spectra are calculated using surface drifter trajectories in the central North Pacific. The meridional integral time scale is relatively homogeneous throughout the region; a large increase in the zonal time and length scales south of Hawaii is attributed to meanders in the North Equatorial Current. Except in this current, the initial dispersion is consistent with Taylor's Theorem. For lags of 20–120 days, the meridional dispersion can be modeled by a constant eddy diffusivity. Shear in the mean zonal currents magnifies the zonal dispersion at long lags. In the Lagrangian spectra, the energetic eddy band is at 3–20 days west of Hawaii, 10–40 days east and north of Hawaii, and 20–60 days in the North Equatorial Current. In the wake of Hawaii, energetic lee vortices produce sharp peaks in the cyclonic and anticyclonic rotary spectra.