The Vialov profile describes the shape of a sample of this substance subject only to internal deformation and a constant rate of surface accumulation. The US Naval Research Laboratory's PIPS project is a numerical model for the distribution of this substance, while SHEBA was a yearlong program in 1997 that studied it. The strain rate in this substance is given by a temperature-dependent proportionality constant times the 
The Vialov profile describes the shape of a sample of this substance subject only to internal deformation and a constant rate of surface accumulation. The US Naval Research Laboratory's PIPS project is a numerical model for the distribution of this substance, while SHEBA was a yearlong program in 1997 that studied it. The strain rate in this substance is given by a temperature-dependent proportionality constant times the cube of the basal shear stress according to Glen's flow law. Leads and (*) polynyas are gaps in this substance, whose thin "grease" variety is formed by the accumulation of frazil. The removal of this substance leads to earthquakes when isostatic rebound occurs. This substance's high albedo causes positive thermal feedback in situations where the total amount of it changes, which also leads to changes in sea levels. For 10 points, name this stuff found in glaciers.
The Vialov profile describes the shape of a sample of this substance subject only to internal deformation and a constant rate of surface accumulation.
ice [or sea ice; prompt on glaciers before mention]