Snow line

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The Alps (in front of the Mont-Blanc group , behind it the Valais Alps ) in summer: the permanent or climatic snow line can be seen
The current snow line can be seen in the lower third of the photo. This is identical to the snow line of the last snowfall if it snowed recently or if the snow remains at temperatures below 0 ° C.

Snow line refers to two different height limits in the mountains , above which snow remains on the ground.

  • Mostly the climatic snow line is meant: This is the (largely) static dividing line between year - round snow-covered and temporarily snow-free areas. It is mainly climatic due to the geographical location . ie, the latitude and the strength of the solar radiation determined by exposure (sun or shadow slope) and the degree of cloudiness . In damp, cool, cloudy maritime climates , for example, it can still be at annual mean temperatures of +4 to 5 ° C, while it needs at least –8 to –10 ° C in a dry, cloudless continental climate . The Nivale altitude level is located above the climatic snow line .
  • The current (also temporary ) snow line is more rarely meant: This is the changing current dividing line between snow-covered and snow-free areas. In the thaw, it is below the snow line . The location of the current snow line is therefore weather-related .

The limit of snowfall is the weather-related height up to which precipitation occurs in the form of snow.

Climatic snow line

Snow limits depend on the climate and geographical latitude. While the climatic snow line in the tropical zone of the earth is over 6000 m, the snow in middle latitudes already lies at 3000 m. In the Arctic and Antarctic the snow line is insignificantly above sea ​​level .

A distinction can be made between two climatic snow limits:

  • The firn border (the actual climatic snow line ) represents the border to the closed snow cover. This means that the deposited snow no longer melts and becomes firn due to the thawing in the summer half-year .
  • The orographical snow line , on the other hand, indicates how far down the valley individual patches of snow can stay in sheltered or shady areas throughout the summer (remains of old wood, dead ice ).

The steeper the mountain range , the greater the difference between the orographical and firn borders , because the differences in local weather usually increase with the slope of the terrain.

Equilibrium line

The average altitude of the firn border on glaciers in the high mountains approximately coincides with the border between the nutrient and consumption area - the so-called equilibrium line . Above this limit, which is just below 3000 m in the Alps , almost every snowfall leads to firn - and as a result of the metamorphosis to ice formation , below the snowline the snow melts in summer. "Snow-free" ( aper ) does not mean " ice-free": Glaciers can also dry out - that is, the snow cover melts and the old ice is exposed.

Rise in the snow line as a result of global warming

As a result of global warming , the snow line has risen in recent years, and the glaciers below this limit have melted. Since the temperature in the lower atmosphere decreases with an average of 6 ° C per kilometer upwards, an average temperature increase of 2 ° C means an increase in the snow line by around 300 meters.

Some data on the climatic snow line

The firn or climatic snow line depends - as indicated above - not only on the geographical latitude, but also on the regional microclimate . It is determined, among other things, by the distance to the coast ( marine temperature compensation), the amount of precipitation , the course of warm ocean currents and the shape of the terrain .

The table below gives some average values ​​and the latitudes:

region B (°) H (m) climatological factors
Spitzbergen (archipelago) 78 0300- 0600
Scandinavia at 67 1000-1500 Gulf Stream
Iceland 65 0700-1100 Gulf Stream
Scandinavia at 62 1200-2200
Alps (north side) 48 2500-2800 North Atlantic traffic jam
Central Alps 47 2900-3200
Alps (south side) 46 2700-2800 more uniform climate ( Mediterranean climate )
Pyrenees 43 2600-2900 see. New Zealand at −43
Caucasus 43 2700-3800 Continental climate
Karakoram 36 5400-5800 Continental climate
Transhimalaya 30-33 6300-6500 Continental climate
Himalayas 30th 4800-6000 Shadowing
Kenya 0 4600-4700 Tropics
New Guinea −2 4600-4700 hardly any seasons
Andes in Ecuador −2 4800-5000 Tropics
Kilimanjaro −3 5500-5600 Tropics
Andes in Chile −27 5800-6500 mild winter temperatures
New Zealand −43 1600-2700 harsher southern climate, see Ecliptic
fire land −54 0800-1300
Antarctic Peninsula −70 0000- 0400

See also

Web links

Wiktionary: snow line  - explanations of meanings, word origins, synonyms, translations

Individual evidence

  1. ↑ Dieter Heinrich, Manfred Hergt: Atlas for ecology. Deutscher Taschenbuch Verlag, Munich 1990, ISBN 3-423-03228-6 . P. 97.
  2. ↑ averaged from Brockhaus -Multimedial 2007