pism/pism — Issue #15: add mass_held_in_surface_layer() to PISMSurfaceModel and use it in stress balances
Author: ckhroulev
Created: 2011-11-08 20:24:19+00:00
State: open
Labels: task

The idea is that a "good" PISMSurfaceModel might "hold" firn for centuries or millenia before "releasing it" as incompressible ice to the ice dynamics core of PISM (=IceModel).

The following is an excerpt from Ed's Jan 2011 visit to the Centre for Ice and Climate, and to Danish Climate Centre:

> Namely we need to add one capability ... PISMSurfaceModel::mass_held_in_surface_layer(t_years, dt_years,
IceModelVec2S &result). Frequently the "dt_years" is just ignored even by "good" firn models, and for the current couplers this would just return 0, I think. This method [would be] called from within SSAFD::compute_driving_stress() and other
places where the thickness and surface slope *related to computation of stresses in the ice are needed. Also for determining flotation and pressure melting temperature, I suppose. But we are not going to claim to compute the stress field in that layer, for example. That is, the surface model owns the mass of the (solid-or-liquid) water in its layer, e.g. for mass conservation purposes and the modeling of runoff and such, but we need the weight of that layer!