10:45 AM - 11:00 AM
[PPS08-07] Possible evolution paths of the lunar orbit based on tidal response in the global ocean model of the early Earth
Keywords:Moon, Earth, ocean, tide, resonance, orbit
Energy dissipation mechanism of the ocean is one of the critical factors in the Moon’s orbital evolution (e.g. Webb, 1982, Lambeck, 1977). Recent studies have revealed that the internal gravity wave, so-called internal tide, is a main mechanism of tidal energy dissipation in the deep ocean (e.g. Taguchi et. al., 2014, Egbert & Ray, 2000). In this study, we considered its effect on the early evolution, assuming the early ocean is as deep as the present abyssal depth.
Our results show that the eigenmode resonance occurs once or more for the first 2 billion years. The Earth-Moon distance rapidly increases with a step-like change at the eigenmode resonance. In the case of the ocean depth decreasing linearly to the time, it is found that the torque due to the oceanic tidal bulge causes continuous increase in the Earth-Moon distance with an especial response of eigenmode oscillation. These acceleration effects could work in the coevolution of the early Earth-Moon system.