286 
Fig. 2: Melting curve from Aletsch Glacier for 1985 (after LAAGER, 1987) 
msl 
directly visible and determinable boundarie 
and features on the surface of a glacier and the 
equilibrium line. 0STREM (1974, p. 66) 
states that "there is a definite correlation 
between the height of the equilibrium line and 
the highest position of the transient snow line", 
whilst for NILSSON (1983, p. 27) the 
equilibrium line "nearly (but not exactly) 
coincides with the so-called firn-line". It has to 
be clearly underlined that this relationship is 
valid for temperate glaciers only. PATERSON 
(1981, p. 53) indicates that "on arctic glaciers, 
the equilibrium line is usually at a lower 
elevation than the snow line at the end of the 
summer". This leads us to the basic hypothesis 
that for the Alps the fimline - if manifested and 
determinable - or otherwise the annual 
snowline are taken as direct indicators for the 
location of the equilibrium line (Tab. 1). Based 
on this approach, the ELA and, if the total 
melting process has been monitored, the 
melting curve can be established. To calculate 
the AAR the total area of the surface of the 
glacier has to be continuously surveyed, too. 
Hereto specific methods have to be developed. 
Since the ELA and the net balance are highly 
correlated, variations in the ELA from year to 
year indicate variations in the net balance. In a 
last step then, a correlation between mass 
balance and climate may be deduced. 
Determination of the ELA 
Digital as well as analog techniques are used 
for the determination of the various 
boundaries. Of particular importance are 
carefully executed geometric corrections