The Influence of Solid Earth Deformations on Semidiurnal and Diurnal Oceanic Tides

Abstract

Since the late nineteen sixties, tidal maps computed from various global models (Hendershott, 1973) have been added to earlier ideas of global ocean tides, which were based exclusively on observations. The use of such ocean tide models has yielded new estimates of the tidal friction in the oceans, which is supposed to be mainly responsible for secular accelerations of the Earth’s rotation (Munk and MacDonald, 1 960; Rochester, 1 973). Brosche and Sündermann (1972) showed how to compute the effects of the tides in the sea on the Earth’s rotation on the basis of tide models. It should be assumed that improved estimates of these effects depend upon the availability of ocean tide models yielding more realistic results. These models do have shortcomings, e.g., excluding stratification and interaction with the nontidal field of motion, which at present cannot be overcome. However, there are other shortcomings that can be done away with. The latter includes the neglecting of the effects of tidal loading and ocean self-attraction, which Hendershott (1972) claimed was possibly a serious shortcoming. Hendershott (1972) was the first to attempt to model the ocean tides by considering the solid Earth’s deformation completely; a further approach was used recently by Gordeev et al. (1977). The approach presented in this paper is based on the inclusion of the effects of the solid Earth’s deformation in the author’s former 4°- ocean-tide model (Zahel, 1970; 1973), which differs considerably from those models into which Hendershott (1972) and Gordeev et al, (1977) introduced the additional effects. Reference will be made to this fact and to the widely differing results in the next Section.