Trench Waves

Abstract

The cross sections of four trenches peripheral to the Pacific Ocean are fitted by a double exponential depth profile. Nondivergent trapped wave propagation is shown to be possible in two directions along such a profile. In addition to the familiar shelf waves, only slightly modified by the presence of a trench, ?trench waves? propagating in the direction opposite to that of shelf waves and at speeds lower by an order of magnitude are also possible. Dispersion curves and eigenfunctions are presented for the Peru-Chile and Japan-Kuril trenches. Coastal sea level records are used to demonstrate phase propagation at ?trench wave? phase speeds off both Japan and Peru. The fundamental mode speeds predominate in the phase spectra off both Japan and Peru.