What is mass balance? Crucial to the survival of a glacier is its mass balance, the
difference between accumulation and ablation (melting and
sublimation). Climate change may cause variations in both
temperature and snowfall, causing changes in mass balance.
Changes in mass balance control a glacier's long term behavior.
It is the most sensitive climate indicator on a glacier. A
glacier with a sustained negative balance is out of equilibrium
and will retreat. A glacier with a sustained positive balance is
out of equilibrium and will advance. A glacier that cannot
retreat to a new point of equilibrium due to negative balances
will disappear.
Figure 1 Annual global glacier mass balance change
1945-2006. Data from WGMS and
Dyugerov et al.,
2005. Seventeen consecutive years of negative
balances.
Figure 2 The cumulative global glacier mass
balance record of glaciers reporting to WGMS. The increasingly negative trend is evident.
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