Printed in Great Britain. On internal tide

Abstract-This paper discusses linear generation models for intemal tides over large topographic features such as continental slopes, with the objects of making the procedures simpler and more adaptable to oceanic situations than heretofore, providing a unified summary of the mechanics involved, and estimating the global internal tide energy generation at all continental shelf-slope junctions for M, and 52 frequencies. A 'composite model'involving wave generation on a shallow thermocline as well as on the continuously stratified fluid below is developed, together with a discussion of the approximations required. The simple case of a linear slope is discussed in detail; one conclusion is that linear internal tides generated on a shallow thermocline will be small unless T: hiln 5 2, where h " is the total depth on the continental shelf, 2nL is a representative wavelength (typically 20 to 30 km) and a is the slope of the continental slope. Such waves propagating seawards are expected to 'leak ' into the deeper stratified water in one or two wavelengths, whilst those propagating shorewards on the shelfmay steepen to form undular bores. The composite model has been applied to all relevant regions ofcoastline, and the five areas with the largest internal tidal energy production are the European northwest shell the East and South China seas, the Guiana Basin region, the Australian northwest shelf, and the Gulf of Maine-Grand Banks region. The summed global barotropic to baroclinic tidal energy conversionsty this process in the coistal regions are estimated to be 1.45 x 1010 J s-l for M, and 2.73 x 10e J s-l for Sr, on an annual mean basis.