Ice Age Earth Rotation

Modern predictions of the rotational stability of an ice age Earth reflect a convergence of two classic problems in geophysical analysis the modeling of the glacial isostatic adjustment (GIA) process and the rotational stability of terrestrial planets. Recent theoretical advances in this area have been motivated not by conventional applications, such as the inference of Earth's deep-mantle viscosity, but rather by efforts to address vexing problems in global climate change research. These advances have demonstrated that traditional calculations of the ongoing motion of the rotation pole relative to the surface geography, or true polar wander (TPW), driven by ice age loading have systematically overestimated this motion by up to a factor of 4 by underestimating by similar to 1% the background flattening of Earth's oblate form. The physics of this sensitivity is related to concepts that appear in canonical, mid-twentieth century discussions of Earth rotation, and avoiding the associated inaccuracy resolves numerous perplexing sensitivities evident in previous predictions of ice age TPW. Moreover, these updated predictions provide both an important step in reconciling a recently defined enigma of modern global sea-level rise and a robust framework for analyzing a suite of space-geodetic constraints on Earth's climate system.