Equilibrium line

The line that separates the accumulation and ablation areas is called the equilibrium line. The elevation of the equilibrium line depends on temperature, precipitation and the surrounding landscape. If the climate conditions remained constant, neither the equilibrium line nor the glacier margin would change.

At present, the equilibrium line altitude on southern Vatnajökull is generally in the range of 1000–1200 m above sea level, but it varies from place to place. At the end of the Little Ice Age, the equilibrium line on southeastern Vatnajökull was probably some 300 m lower than today. The accumulation areas of the south flowing outlet glaciers were thus much larger. Due to lower temperatures and a shorter melt season, there was less ablation and outlet glaciers advanced down valleys and far out onto the lowlands.

 

 The equilibrium line is at the boundary of the accumulation area and the ablation area, however, the elevation varies from year to year. The ice flows downhill from the accumulation zone towards the ablation zonewhere higher temperatures intensify the melting. Crevasses form when the glacier flows over an uneven bed or is dragged along the mountain sides.

The equilibrium line is at the boundary of the accumulation area and the ablation area, however, the elevation varies from year to year. The ice flows downhill from the accumulation zone towards the ablation zonewhere higher temperatures intensify the melting. Crevasses form when the glacier flows over an uneven bed or is dragged along the mountain sides.

 

 Landsat satellite image from the fall of 1994. The snowline is visible and clearly marks the boundary between the white snow-covered surface of the accumulation areas vs the darker glacial ice in the ablation area. On temperate glaciers, the autumn snowline is often defined as the equilibrium line.

Landsat satellite image from the fall of 1994. The snowline is visible and clearly marks the boundary between the white snow-covered surface of the accumulation areas vs the darker glacial ice in the ablation area. On temperate glaciers, the autumn snowline is often defined as the equilibrium line.