Simple analytical models of glacier-climate interactions - by Prof. J ...

Fig. 1.3 shows that the model is able to reproduce the balance profile of Nigardsbreen
(model parameter values: A 1 = 110 W m -2 , β E = 0.115 W m -2 , P sl = 2 m, γ P = 0.0012,
h ref = 1325 m). With this choice of parameter values the model not only simulates the
balance profile accurately, but it also reproduces realistic features such as a significant
amount of melt in the highest mass balance interval (1900-2000 m) and little snow
accumulation on the lowest part of the glacier.
The simple mass balance model can be used for climate sensitivity tests. The precipitation
rate can be changed and the new resulting balance profile can easily be calculated. For a
temperature change the situation is more complicated, because now the change in A 0 and
A 1 has to be known. Detailed energy balance studies suggest that the first-order effect of
a 1 K temperature rise is to increase A 0 by typically 10 W/m 2 . The implications for the
mass balance of Nigardsbreen, calculated with the model described above, are shown in
Fig. 1.4.
Fig. 1.4
2000
Nigardsbreen
1600
Altitude (m)
1200
800
400
reference
+2 K
+2 K ; +20 %
-12 -8 -4 0 4
Specific balance (mwe)
Problems
• What are the most important processes that contribute to the altitudinal gradient in the
surface energy flux β E ?
• Estimate from Fig. 1.1 how much ice can be melted on a hot summer day on the snout
of the Morteratschgletscher.
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