Lingle and fatland 2003 (7) Flashcards
What is needed for a surge type glacier?
A surge-type glacier must have sufficient storage capacity for continued downward movement of englacially stored water during winter to finally overwhelm the constricted basal drainage system, thereby forcing pervasive failure of the subglacial till or, alternatively, widespread and rapid basal sliding thus initiating a surge.
The average length of the surge cycle in a given region appears to be a function of…
the mass balances, which, after each surge, determine the time required to restore glaciers to their pre-surge geometries.
Stenborg (1970) found what…?
The runoff excess during mid-summer was greater than the runoff deficit during early summer by about a factor of two.
He concluded that the glacier had stored water during early summer and subsequently released this stored water during mid-summer.
What did Tangborn and others (1975) conclude happens during long periods with little or no ablation (late fall to early spring)?
The glacier’s internal and subglacial drainage system becomes constricted.
The water resulting from the relatively small amounts of ablation and rain occurring during these periods is thus forced into storage.
When ablation increases in the spring, the rapidly increasing hydraulic head forces additional water into storage while the summer drainage system is gradually melting open.
Much of the runoff observed during summer was thus stored during the preced- ing spring and fall.
Fountain and Walder (1998) suggest that the likely storage capacity of subglacial cavities beneath small, temperate alpine glaciers (e.g. South Cascade Glacier) is…
insufficient to account for the estimated volumes of stored water. This implies that most water storage may be englacial.
A surge hypothesis is presented that builds on the work of Stenborg (1970), Bjornsson (1972), Tangborn and others (1975), and more recent studies (e.g. Collins, 1982; Willis and others, 1993; Murray and others, 2000) which have shown…
that temperate glaciers seasonally store water englacially.
What does this paper propose is the cause of temperate-glacier surges?
Englacial storage of a sufficiently large volume of water, after surge-type glaciers have thickened sufficiently to store this water.
The average time required to return a given glacier to its pre-surge geometry appears to be a function of…
its mass balance, i.e. the regional climate, with glaciers in high-precipitation regimes surging more frequently, on average, than glaciers in low-precipitation regimes.
What is the process that results in surge initiation, consisting of pervasive failure of the subglacial till or, alternatively, the onset of widespread and rapid basal sliding?
Downward movement of stored water to the bed during winter, at a rate sufficient to finally overwhelm the constricted subglacial drainage system.
Why is it that long’’ glaciers are more likely to be surge-type thanshort’’ glaciers?
Long glaciers are likely to be thicker and hence capable of storing more water than short glaciers.
