**Linda Hinnov, ***Dept. of Atmospheric, Oceanic, and Earth Sciences George Mason UniversityFairfax, Virginia, USA,*

*Web Lecture on November 10,Â 2022 at 3:00 PM (Paris Time)*

The physical basis of the modern theory of the glacial isostatic adjustment process is embodied in a Fredholm integral equation of the second kind. The kernel of this integral equation consists of the difference between Green functions for the impulse response of the approximately spherical viscoelastic planet for radial displacement (Peltier, 1974) and for the perturbation to the gravitational potential field (Peltier and Andrews, 1976). The inversion of this integral equation for a given history of surface mass loading is a prediction of the space and time dependence of the level of the sea with respect to the continuously deforming surface of the solid Earth. The theory is gravitationally selfâ€“consistent in the sense that sea level is constrained to evolve such that the surface of the global ocean remains a surface of constant gravitational potential on which the potential is a slowly varying function of time. When its height is measured with respect to the centre of mass of the Earth, this surface is the (time dependent) geoid of classical geodesy. Because the rotational state of the planet is significantly influenced by the exchange of mass between the oceans an land-based ice sheets during the glacial cycle the integral equation must be modified to include the feedback of this changing rotation state upon sea level itself resulting in a theoretical structure that must be applied iteratively in order to ensure that this feedback is accurately represented (eg see the reviews by Peltier, 1998 and 2015 for detailed discussion).

.