Forced Trench Waves

A general theory for forced barotropic long trench waves in the presence of linear bottom friction is presented. Two specific forcing mechanisms are considered: (i) transverse fluctuations in a western boundary current as it flows across a trench, and (ii) a traveling wind system that moves parallel to the trench. The mechanisms (i) and (ii) are applied to the Japan-Kuril trench and Aleutian trench, respectively. In the case of the Japan-Kuril trench it is found that 3-month period fluctuations in the Kuroshio are able to generate currents along the trench of 0 (10 cm s−1) and coastal sea level variations of O (7 cm). In the case of the Aleutian trench, traveling wind systems in the northeast Pacific may produce a near resonant response. Such a response consists of velocity fluctuations of 0 (10 cm s−1) along the trench and of 0 (4 cm s−1) across the trench, the coastal sea level fluctuations can be up to 12 cm. While these estimates should be regarded as tentative because of the uncertainty in the value of the bottom friction coefficient, they nevertheless suggest that trench wave motions could produce significant long-time scale velocity and sea level fluctuations in the North Pacific trenches.