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Analysis of a Precambrian resonance-stabilized day length
During the Precambrian era, Earth's decelerating rotation would have passed a
21-hour period that would have been resonant with the semidiurnal atmospheric
thermal tide. Near this point, the atmospheric torque would have been
maximized, being comparable in magnitude but opposite in direction to the lunar
torque, halting Earth's rotational deceleration, maintaining a constant day
length, as detailed by Zahnle and Walker (1987). We develop a computational
model to determine necessary conditions for formation and breakage of this
resonant effect. Our simulations show the resonance to be resilient to
atmospheric thermal noise but suggest a sudden atmospheric temperature increase
like the deglaciation period following a possible "snowball Earth" near the end
of the Precambrian would break this resonance; the Marinoan and Sturtian
glaciations seem the most likely candidates for this event. Our model provides
a simulated day length over time that resembles existing paleorotational data,
though further data is needed to verify this hypothesis.Comment: 7 pages, 5 figures. Accepted for publication in Geophysical Research
Letters on 10 May 201
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