Sinusoidal viscous rebound ($\tau =4\pi \eta /(\rho g\lambda )$)

A small sinusoidal relief on an incompressible Newtonian viscous half-space relaxes exponentially with the displayed timescale in the ideal free-surface model. Here $\lambda$ is wavelength, not automatically an ice-sheet radius or diameter. Ice-history, finite mantle layering, elastic lithosphere and self-gravity complicate real glacial isostatic adjustment.