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About glaciers

A glacier is an area with permanent ice and snow, which is in motion. The ice is built up in the upper parts by large snow surpluses in the winter, and then slowly slides down to lower levels, where the ice melts, primarily during the summer. The snow is transformed to ice partly by being compacted by the weight of higher snow strata, and partly through refreezing (snow melts, the meltwater trickles down deeper in the snow and freezes once more).

Storglaciären (Kebnekaise) Storglaciären (Kebnekaise), August 9, 1990. (43 kB)

When the ice has become roughly 20 m thick it starts to deform under its own weight and slowly starts to flow downslope. Ice being hard and brittle nonwithstanding, it also can flow plastically under forces of long duration. Because the friction is greatest along the sides and bottom the ice moves as most rapidly at the surface and along the centerline, in the same manner as a river. Most glaciers in Scandinavia move both through internal deformation and by sliding over their beds, even though there are a few, which are frozen to their beds.

Moulin on 
Salajekna (Sulitelma) Moulin on Salajekna (Sulitelma), August 8, 1991. (58 kB)

Glaciers in Sweden moves up to a few tens of metres each year, while some Norwegian outlet glaciers can move more than 100 m a year. The largest measured ice depth in Sweden is about 250 m in Storglaciären in Kebnekaise, but it is likely that greater depths exist in other glaciers. In Norway 650 m has been measured on Jostedalsbreen. In Sweden there are slightly less than 300 km2 of glaciers; Norway has roughly ten times as much.

The upper part of Salajekna (Sulitjelma) The upper part of Salajekna (Sulitjelma), August 1, 1996. (44 kB)

There are a number of morphological types of glaciers. Cirque glaciers are usually fairly small with large width compared to length, and lies in more or less deep niches in the mountain side. Valley glaciers are generally larger and more elongate; they fill up an entire valley. Ice caps in a strict sense are ice domes lying atop a mountain plateau; here this term is also used for glaciers lying on a mountain side, or in a shallow depression. Glacier complexes is my term for systems of several continuos ice streams.

Crevasse 
zone on Helagsglaciären (Härjedalen) Crevasse zone on Helagsglaciären (Härjedalen), August 4, 1997. (97 kB)

The greatest danger on a glacier is posed by crevasses. All glaciers have crevasses; some only a few while others have lots. Generally a glacier becomes more heavily crevassed the faster it moves, but the amount of crevasses is influenced by the steepness of the glacier and the irregularity of its bed as well. On bare ice the crevasses are not too dangerous, because you can see and avoid them there. The true danger lies in crevasses covered by a layer of snow that wonīt support the bodyweight. Because of the crevasse danger you should always be a party of at least 3 people, tied together with a rope, when travelling on glaciers. Crevasses rarely exceed 20-30 m in depth, since the plasticity of the ice closes them below this depth. Places where crevasse systems in different directions intersect so that all that remain of the ice surface is a chaotic jumble of ice towers are called icefalls.

Icefall on Svenonius glaciär (Sarek) Icefall on Svenonius glaciär (Sarek), August 19, 1994. (66 kB)

The glaciers have been more extensive earlier, even after the ice age. Before the so-called Little Ice age, which lasted roughly from 1500 to 1900, the glaciers probably were about as extensive as today, or slightly smaller. Then it however became substantially colder, and the glaciers started growing rapidly, first during a period in the early 16th century, and then even more in the early 18th century. After 1750 the glaciers slowly began to thin and retreat, but the great decline didnīt start until right after the last turn of the century. Around 1960 the retreat began to slow down and the glaciers stabilize, but during the very latest decade some glaciers have actually began to advance again.

The ice 
cliff of Salajekna (Sulitelma) The ice cliff of Salajekna (Sulitelma), August 8, 1991. (91 kB)

This might seem strange considering the so-called greenhouse effect, but it is actually not impossible that just that is one of the reasons behind this. If the Earth as a whole becomes warmer more water is evaporated, which must come down again. Consequently more rain, or more snow, if the temperature is below zero (Celsius). The increase in precipitation will not be even however; certain areas will get much more precipitation, while others might get less.

The advancing front of Engabreen (Svarisen, Norway) The advancing front of Engabreen (Svartisen, Norway), July 28, 1997. (77 kB)

This is exactly what seems to have happened in Scandinavia: The summer temperature continues to be high, but the winter precipitation has increased so much (some 50 %) that it actually offsets the temperature rise, indeed more than that. All glaciers in Scandinavia are not affected equally; primarily it is the far western ones which are advancing. Some Norwegian glaciers, in particular short, steep outlets from the great ice caps, have advanced rapidly - some up to 1 km in only some ten years. Some Swedish glaciers have also displayed signs of smaller advances. Only time will tell whether this pattern will continue in the future.


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Last updated: March 17, 2001 Unless otherwise specified; text, tables, photographs, maps and other
graphics © 1999-2001 Gunnar Ljungstrand