Did atmospheric thermal tides cause a daylength locking in the Precambrian? A review on recent results

TL;DR

This review critically examines recent claims that atmospheric thermal tides caused Earth's daylength locking in the Precambrian, concluding that the evidence and models do not support this hypothesis.

Contribution

It clarifies the uncertainties in geological data and evaluates models, showing that atmospheric tides likely did not induce daylength locking in Earth's early history.

Findings

Geological estimates of past daylength are highly uncertain.

Robust data do not support the atmospheric tidal locking hypothesis.

Models suggest atmospheric tides were insufficient to cause LOD locking.

Abstract

After the initial suggestion by Zahnle and Walker (1987) that the torque accelerating the spin rate of the Earth and produced by the heating of the atmosphere by the Sun could counteract the braking lunir-solar gravitational torque in the Precambrian, several authors have recently revisited this hypothesis. In these studies, it is argued that the geological evidences of the past spin state of the Earth play in favor of this atmospheric tidal locking of the length of the day (LOD). In the present review of the recent literature, we show that the drawn conclusions depend crucially on the consideration of the stromatolite geological LOD estimates obtained by Pannella at 1.88 and 2.0 Ga, which are subject to large uncertainties. When only the most robust cyclostatigraphic estimates of the LOD are retained, the LOD locking hypothesis is not supported. Moreover, the consideration of the published General Circulation Model numerical simulations and of new analytical models for the thermal atmospheric tides suggest that the atmospheric tidal resonance, which is the crucial ingredient for the LOD locking in the Precambrian, was never of sufficiently large amplitude to allow for this tidal LOD lock.