|
E. Linacre |
12/'98 |
The average height of the snowline on mountains varies not only with latitude, but also with orientation of the mountain slope and with annual mean precipitation (1). The elevations are greater where the slope is exposed towards the equator (towards the north in the southern hemisphere). The snowline is also higher in dry climates than in moist, since snow will tend to sublime away into dry air, and be melted under less cloudy skies (Fig 3.6, Table 1). This may result in snow-free conditions in places where the average daytime maximum screen temperature remains below 0° C. At any given latitude, the snowline tends to be lower in the southern hemisphere, where summers are cooler than in the north because of a larger area of ocean, and because of the coldness of Antarctica. The altitude of the summer snowline usually is slightly above that of the timberline.
Table 1. Effects of hemisphere, latitude and climatic dryness on the average snowline’s elevation, in metres (1). SH = southern hemisphere; NH = northern hemisphere. The figures for South America are from (2).
|
Latitude (° ) |
SH, dry |
SH, moist |
NH, dry |
NH, moist |
South America |
|
80 |
0 |
0 |
400 |
100 |
- |
|
60 |
700 |
200 |
2,500 |
600 |
300 |
|
50 |
1,000 |
||||
|
40 |
3,300 |
1,200 |
5,100 |
2,400 |
2,800 |
|
30 |
6,000 |
||||
|
20 |
6,200 |
4,900 |
5,500 |
4,800 |
6,000 |
|
10 |
4,700 |
||||
|
equator |
5,200 |
4,500 |
5,200 |
4,500 |
4,800 |
For instance, there are extensive snowfields at 5,800 m on the Aconquija mountain at 27ºS, but only occasional snow at 6,720 m on Llullaillaco mountain at 25ºS, where there are many remains of Inca altars, stables and dwellings (2).
References
(2) Schwerdtfeger , W. (ed.) 1976. Introduction. Climates of Central & South America. World Survey of Climatology (Elsevier) 12, 1-12.
(3) Prohaska, F. 1976. The climates of Argentina, Paraguay & Uruguay. Climates of Central and South America. World Survey of Climatology (Elsevier) 12, 13-112.