Ocean tide size linked to supercontinent cycle

A new tweak to tidal theory is proposed. The research team hopes that ‘understanding continental configurations and tidal strengths will impact the development of climate models’.

Daily tides are driven primarily by Earth’s rotation and the gravitational force of the moon on oceans, says Earth magazine.

However, in a new study in Geophysical Research Letters, researchers suggest that tidal magnitudes are also influenced, on longer timescales, by the size and shape of the ocean basins, and are therefore driven by plate tectonics.

Plate tectonics gives rise to the formation of supercontinents — massive aggregations of continental lithosphere — which form and break apart in cycles that last about 400 million to 500 million years. With the breakup of the last supercontinent, Pangea, about 180 million years ago, and the projected formation of a new supercontinent, known as Aurica, in about 200 million years, Earth is currently in the middle of a supercontinent cycle.

Because the size and shape of ocean basins impact ocean circulation and tides, researchers led by Mattias Green, a physical oceanographer at Bangor University in England, hypothesized that tides may be linked to the supercontinent cycle in a so-called supertidal cycle.

Current tides, particularly those in the North Atlantic, are very large, Green’s team noted because of tidal resonance, which occurs when ocean basins and continental shelves reinforce and amplify the natural oscillation of tides as they sweep back and forth across oceans. “So the tides are larger at present because the continents are configured the way they are.”

To model Earth’s future oceanic tides, the researchers used predictions of continental configurations for the next 250 million years, through when Aurica is predicted to form. Ocean basin size was the main factor considered in the modeling, but the team also accounted for the moon’s gravitational pull on the oceans, Earth’s axial tilt, and simplified ocean bathymetries for future plate tectonic reconstructions.

Simplification of these fine details does affect the team’s modeling, notes David Waltham, a mathematical geologist at the Royal Holloway University of London, who was not involved in the study. But the simplifications used likely do not change the overall results, he adds.

Green and his colleagues reported that global tides are likely to increase over the next 50 million years “due to an enhanced tide in the North Atlantic and Pacific at 25 million years, followed by a very large Pacific tide at 50 million years.”

Continued here.