Weak Solutions for the Unregularised Hibler Momentum Equation with Degenerate Coefficients

RESUMO

We study the momentum equation of the decoupled unregularised Hibler sea-ice model with non-negative ice mass and ice strength, both of which may vanish. The ocean drag provides coercivity, while the stress law and mixed boundary conditions are encoded by a convex dissipation functional. We prove existence, uniqueness and stability for the time-discrete problem and reconstruct an admissible stress. A Rothe approximation yields global weak variational solutions for time-dependent coefficients under a one-sided growth condition on the mass. Weak solutions are unique when the ice strength is independent of time. For spatially Lipschitz ice strength, finite dissipation also yields a local measure structure of the weighted deformation and a global bound on the negative part of the weighted divergence.