Ice-sheet flotation
= Ice-sheet flotation
{title2=$\rho H=\rho_w b$}
At a <grounding line>, <hydrostatic pressures> balance when the weight of an <ice> column of thickness $H$ and <mass density> $\rho$ equals the weight of its displaced <water>, of depth $b$ and <mass density> $\rho_w$. Thus flotation gives $\rho H=\rho_w b$. Its time <derivative> along a moving <grounding line> relates local thickness changes to grounding-line speed; it supplies a different boundary condition from the <unbuttressed Newtonian grounding-line stress>.