ncts

Ice sheets (with their attached ice shelves), ice caps and glaciers are active, dynamic components of the climate system of Earth. They feature gravity-driven creep flow ("glacial flow"), sustained by the underlying land. This leads to thinning and horizontal spreading, which is essentially compensated by snow accumulation in the higher (interior) areas and melting and calving in the lower (marginal) areas. Any imbalance of this dynamic equilibrium leads to either growing or shrinking ice masses. Here, we will review the underlying field theories of continuum mechanics and thermodynamics, as well as the material (rheological) properties of polycrystalline ice. Combining the balance and material equations leads to the field equations for the flow of ice sheets, ice shelves, ice caps and glaciers, which must be complemented by suitable boundary conditions. We will treat a hierarchy of simplifications of the field equations, from the most sophisticated full Stokes formulation to the most simplified shallow-ice and shallow-shelf approximations. We will present some examples of numerically computed solutions for selected problems of ice sheet and glacier flow.