Movement

The Kongsvegen is classified as a polythermal glacier, with large variations in the temperature of the ice below. The ice near the surface (between 50 and 160 metres down (160-520 feet)) is very cold, and overlies a much warmer base of ice. This leads to increased mass flow and velocity over the summer months, usually because of the build-up of meltwater at the base, which lubricates the glacier in basal sliding. The glacier is of a surge type, meaning that its length and characteristics can vary rapidly over time, making the ice field very unpredictable. It also means the glacier can undergo rapid periods of advancing and retreating movement. From 1948 to 1977 the glacier retreated very quickly at rates of up to 800 metres per year after a large surge in its movement downstream. Kongsvegen has also experienced periods, as now, of relative stasis. At the moment Kongsvegen is retreating at 3 metres (10 feet) per year and has been doing so since 1990. This has allowed the glacier to build up its ice mass further upstream, while shrinking in length downstream, where the ice is thin from rapid movement.^[1]