Tidal signals in basin-scale acoustic transmissions

Abstract

Travel times of acoustic signals were measured between a bottom-mounted source near Oahu and five bottom-mounted receivers located near Washington, Oregon, and California in 1988 and 1989. At three out of five receivers, observed travel times at M2 and S2 periods agree with predictions from a barotropic tide model to within 30 deg in phase and a factor of 1.6-in. amplitude. The discrepancies at the fourth and fifth receivers can be removed, to first order, by including predicted effects of phase-locked baroclinic tides generated by guyots in the Moonless mountains. A simple model is used to estimate the conversion of energy from barotropic to baroclinic tides by the world’s seamounts. At M2, the conversion amounts to about 4% of the total dissipation at M2. Although this estimate is very approximate, it is similar to other published values.