Under surface loads, the Earth depresses in order to restore a state of isostatic equilibrium. Conversely, when these loads disappear, the surface rises again to recover its initial configuaration. In case of glacial loading, the size and the speed at which an ice sheet can evolve is responsible for a specific response of the Earth and especially for some transient associated behaviours. After introducing the idea of isostasy, we describe what can be the consequences on the isostatic response of both the size and the rate of evolution of the load. This will help in clarifying what we cali the " glacial context ". Then, the numerous impacts this response can have in retum on the ice sheet dynamics as weil as the different ways of accounting for them are presented. This first part will have shown the interest in developping an elaborated Earth model in which the physics are much more rigourous than for most of the classical parameterisations used up to now in ice sheets models. The characteristics and the equations for the model developped in this study are then sketched in detail and reveal its degree of sophistication. The numerous field measurements performed over postglacial rebound areas like Fennoscandia appear to be a good way of testing such a model validity. Indeed, by comparing the results of the simulated rebound with these data, it becomes possible to check whether the model seems realistic or not. Although these different kinds of data are not perfectly reproduced simultaneously, the model nevertheless exhibits a rather realistic behaviour which gives some confidence when combining it with an ice sheet model. The results of such a coupling are then compared with those from the classical parameterisations in the simulation of the Antarctic ice sheet during the last glacial cycle. This simulation confirms the relatively good behaviour of our Earth model compared to the others, which tends to show that some of these classical approaches should be avoided in ice sheet modeling.
