Annual sea-ice thermodynamic equilibrium ($h(t+\mathcal{T})=h(t)$)

For annually repeated forcing, a thermodynamic equilibrium is a periodic temperature field and thickness cycle. The yearly integral of net ice growth is zero, although substantial winter growth and summer ablation can each occur. Equilibrium thickness must specify an annual mean or a phase of the cycle. A change in forcing can remove a perennial-ice solution without making every transient thickness decrease at the same rate.