Gletsjere

Gletsjere are large, persistent masses of ice formed from the accumulation, compaction, and recrystallization of snow over many years. They originate where snow accumulation exceeds ablation (melting and sublimation), causing the snow to transform into firn and eventually glacial ice. The ice gains mass mainly from snowfall and loses it through melting, calving, and sublimation.

Most gletsjere flow under gravity, moving slowly downslope or outward from high elevations. The flow creates crevasses, seracs, and other deformation features. The terminus, or end, of a gletsjere can advance or retreat depending on climate and conditions. As they move, gletsjere erode bedrock and sculpt landscapes, forming features such as U-shaped valleys, fjords, and moraines.

They occur in two main settings: mountain regions with valley glaciers and large continental ice sheets that cover vast areas, such as Greenland and Antarctica. Other types include tidewater glaciers that terminate in the sea, cirque or horn glaciers in alpine basins, and ice caps that cover plateaus.

Gletsjere are sensitive indicators of climate change. In many regions, warming temperatures have increased melt and retreat, contributing to global sea level rise and freshwater changes. Some areas show seasonal advances with heavy snowfall, but overall trends point to shrinking ice masses.

Scientists study gletsjere with field observations, remote sensing, and mass-balance measurements to track changes in terminus position, flow speed, thickness, and volume. Notable examples include Vatnajökull in Iceland, the Greenland Ice Sheet, and many glaciers in the Alps and in Norway.