<p>Polar ice sheets are important components of any Earth System model. As the domains of land, ocean, and ice sheet change, they must be consistently defined within the lexicon of geodesy. Understanding the interplay between the processes such as ice sheet dynamics, solid Earth deformation, and sea level adjustment requires both consistent and mass conserving descriptions of evolving land and ocean domains, grounded and floating ice masks, coastlines and grounding lines, and bedrock and geoid height as viewed from space. Here we present a geometric description of an evolving ice sheet margin and its relations to sea level change, the position and loading of the solid Earth and include the ice shelves and adjacent ocean mass. We generalize the formulation so that it is applied to arbitrarily distributed ice, bedrock and adjacent ocean, and their interactive evolution. The formalism simplifies computational strategies that seek to conserve mass in Earth System models.</p>