Sea level variations during snowball Earth formation and evolution: 2. The influence of Earth's rotation

Abstract

[1] Preliminary analyses are described of the influence of snowball Earth formation on the rotational state of the Earth as well as its feedback onto relative sea level. We demonstrate that a sufficiently large excess ellipticity of the Earth as might be expected to arise due to the mantle convection process acts to stabilize the rotational axis significantly so that the associated relative sea level change would be negligible. If no such excess ellipticity were characteristic of Neoproterozoic time, then increasing the thickness of the elastic lithosphere significantly promotes true polar wander (TPW) and the associated relative sea level change. On the contrary, increasing the viscosity of the lower mantle has an equally significant but opposite effect. TPW due to ice sheets formation for the 720 Ma and 570 Ma continental configurations (approximate Marinoan) can reach more than 5° and 10° in 10 Myr for viscosity model VM5a, and the associated maximum relative sea level changes at this time reach 26 m and 49 m, respectively. However, if a 1°/Myr TPW due to the action of the mantle convection process is assumed to be superimposed, then these values increase to 70 m and 101 m respectively. Compared to the analyses in which rotational influence is entirely neglected, the probability density distribution of freeboard values obtained here is almost the same except that the tails of the distribution are broadened, making it more difficult to accurately infer continental ice volume during snowball Earth events from observed freeboard changes.