Rotational Eustasy as Understood in Physics

Abstract

Global sea level has today become widely understood merely in terms of glacial eustasy and thermal expansion. Although this is good in theory, it is not enough to explain observational facts in nature. We know that the 17th century was characterized by cold climate, Little Ice Age conditions, and low solar activity during the Maunder Grand Solar Minimum. In contrast, the 18th century was characterized by warm climate conditions and a Grand Solar Maximum (with the Polar front located north of Svalbard). In terms of glacial eustasy, one would expect to find a low sea level in the 17th century and a high sea level in the 18th century. This is not the case in the equatorial regions, however. In the Indian Ocean and the Pacific, there was a 60 - 70 cm higher sea level in the 17th century, and a sea level well below the present one in the 18th century. This can only be understood in terms of “rotational eustasy”. This is a novel concept, here for the first time addressed with respect to physical interpretation. It is shown that planetary beat affects Earth’s rate of rotation and that this leads to oscillations of the equatorial water bulge with amplitudes of up to ±70 cm.