Investigation of creep instability as a mechanism for glacier surges Page: 5 of 40
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ABSTRACT
Creep instability, the runaway increase of internal tempera-
ture and deformation rate, has been suggested as a possible
cause of surges of cold glaciers. We investigate this by
considering a simple slab model which includes the effect of
ice advection normal to the surface. Whether a steady-state
solution of the heat transfer equation. exists depends on the
value of a "stability parameter" proportional to the ratio
of the rate of deformational heat production to the rate at
which this heat is conducted away. If the parameter exceeds
a certain critical value, instability occurs and basal ice
eventually reaches melting point. The ice mass can then start
to slide over its bed. If the stability parameter exceeds a
second higher critical value, a layer of basal ice at melting
point will form. The critical values depend on geothermal
heat flux and strongly on advection. Upward advection, as in
the ablation area, decreases stability whereas downward advec-
tion (accumulation) increases it. On the other hand, if un-
stable conditions exist, accumulation increases the growth
rate of the instability while ablation decreases it. Calcula-
tions suggest that certain natural ice masses may be unstable.
The time for the instability to develop, however, is of the:-
order of 100 to 10,000 yr., whereas the residence time of the
ice in many glaciers is less than 10,000 yr. Moreover, obser-
ved~periodicities of glacier surges are between 10 and 100 yr.
It thus appears that creep instability cannot explain glacier
surges. These arguments do not, however, eliminate the pos-
sibility of creep instability causing surges in the Antarctic
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Paterson, W. S. B.; Nitsan, U. & Clarke, G. K. C. Investigation of creep instability as a mechanism for glacier surges, article, January 1, 1976; New Mexico. (https://digital.library.unt.edu/ark:/67531/metadc1449092/m1/5/: accessed July 17, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.