Explicitly Modelled Deep-Time Tidal Dissipation and its Implications for Lunar History

Dissipation of tidal energy causes the moon to recede away from the Earth. The currently measured rate of recession implies that the moon is about 1,500Ma, but the moon is known to be ~4,500Ma old. Consequently, it has been proposed that tidal energy dissipation was weaker in the Earth's past, but explicit numerical calculations are missing for such long time intervals. Here, for the first time, numerical tidal model simulations linked to climate model output are conducted for a range of paleogeographic configurations over the last 252Ma. We find that the present is a poor guide to the past in terms of tidal dissipation: the total dissipation rates for most of the past 252Ma were far below present levels. This confirms the old-age moon theory, and the lower dissipation allow refinement of orbitally-derived age models by shifting ages by an entire precession cycle.