Tidal Energy Dissipation over long Geological Time Scales

Houraa Daher1, Alistair Adcroft2, Joseph K Ansong1, Brian K Arbic1, Jacqueline Austermann3, Jerry X Mitrovica4 and Adam C Maloof5, (1)University of Michigan Ann Arbor, Ann Arbor, MI, United States, (2)Princeton University, Atmospheric and Oceanic Sciences, Princeton, NJ, United States, (3)Harvard University, Cambridge, MA, United States, (4)Harvard University, Department of Earth and Planetary Sciences, Cambridge, MA, United States, (5)Princeton University, Department of Geosciences, Princeton, NJ, United States
Abstract:
Over most of the history of the Earth-Moon system, tidal dissipation has been

substantially lower than it is today. This is somewhat perplexing because in the past the

moon was closer to the Earth and therefore tidal forces were larger. Previous work on

this problem, done with highly idealized models, has shown that tidal dissipation is

sensitive to Earth’s rotation rate and the configuration of continents, which together set

the time scale of the ocean’s normal modes and hence their degree of resonance with

the tidal forcing. Here, we employ a state-of-the-art global high-resolution ocean

model, forced by the M2 tidal constituent, to explore the history of tidal resonance in a

model with realistic bathymetries and continental geometries. Increasing Earth’s

rotation rate, while keeping geometries and bathymetries fixed to present-day values,

yields substantially lower dissipation rates, consistent with the results of idealized

models. We also show results from simulations with different continental configurations,

increased tidal forcings, and smoother coastlines that mimic hundreds of millions of years

without glacioeustasy in the Archaean and Proterozoic, to help unravel the puzzle of tidal

dissipation over long geological time scales.

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