| Term: | Equilibrium line |
| Definition: |
The set of points on the surface of the glacier where the climatic mass balance is zero at a given moment. The equilibrium line separates the accumulation zone from the ablation zone. It coincides with the snowline only if all mass exchange occurs at the surface of the glacier and there is no superimposed ice. Unless qualified by a different adjective, references to the equilibrium line refer to the Annual equilibrium line. See also equilibrium-line altitude, firn line, snowline, transient equilibrium line, zone. IHPGlacierMassBalance
Equilibrium line is the boundary between the accumulation area and the ablation area. The spatially averaged boundary at a given moment, usually chosen as the seasonal mass budget minimum at the end of summer, between the region on a glacier where there is a net annual loss of ice mass (ablation area) and that where there is a net annual gain (accumulation area). The altitude of this boundary is referred to as equilibrium line altitude (ELA). IPCC2013 The boundary on a glacier between the ablation area and accumulation area. No net mass is gained or lost at this location. In the absence of superimposed ice, this line is equal to the snow line at the end of the mass balance year. AMSglossary The line or zone on a glacier where a year's ablation balances a year's accumulation. The equilibrium line is determined at the end of the ablation season (cf. Firn line and Snow line). SPRI Line or zone on a glacier along which the annual ablation balances the annual accumulation. WMOHydrology The line or zone on a glacier's surface where a year's ablation balances a year's accumulation (cf. Firn line). It is determined at the end of the ablation season, and commonly occurs at the boundary between superimposed ice (q.v.) and glacier ice. Swisseduc GCW |