◆ update()

void pism::stressbalance::WeertmanSliding::update	(	const Inputs &	inputs,
		bool	full_update
	)

virtual

Compute sliding velocity using a Weertman-style parameterization from [Tomkin2007], equation 5.

$u_s = \frac{2 A_s \beta_c (\rho g H)^{n}}{N - P} \cdot |\nabla h|^{n-1} \cdot \nabla h,$

where

$A_s$ is the sliding parameter,
$\beta_c$ is a parameter capturing the effect of the presence of valley walls (set to 1 in this implementation),
$\rho$ is the ice density,
$H$ is the ice thickness,
$h$ is the ice surface elevation ,
$n$ is the flow law exponent (usually 3),
$g$ is the acceleration due to gravity,
$N$ is the ice overburden pressure,
$P$ is the basal water pressure.

With these modifications and noting that $N = \rho g H$ , the formula above becomes

$u_s = \frac{2 A_s}{1 - k} \cdot (N |\nabla h|)^{n-1} \cdot \nabla h,$

where

$N = \rho g H$ ,
$P = k N$ (we assume that basal water pressure is a given fraction of overburden)

This parameterization is used for areas of grounded ice where the base of the ice is temperate.

Definition at line 74 of file WeertmanSliding.cc.