Basal Sliding at the Margin of the Glacier Austre Okstindbre, Nordland, Norway

Andreasen, Jørn-Ole

doi:10.2307/1550829

Cited by 10 publications

(6 citation statements)

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“…Basal ice may be isotopically heavier than both “unaltered” englacial ice and snow at the glacier surface (Hubbard and Sharp, 1995; Iizuka and others, 2001). A variety of basal ice formations is present at the bottom of Austre Okstindbreen (Theakstone, 1988a), and some basal ice does form as water freezes within cavities beneath the glacier (Andreasen, 1983). However, basal ice does not outcrop at the glacier margins, and no evidence has been found of a thick layer of metamorphosed ice caused by widespread, large-scale refreezing at the glacier.…”

Section: Discussionmentioning

confidence: 99%

Oxygen isotopes in glacier-river water, Austre Okstindbreen, Okstindan, Norway

Theakstone

2003

J. Glaciol.

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There is no discernible river discharge from Austre Okstindbreen, Norway, in winter; any water formed by basal melting is likely to be stored in isolated cavities or sediments at the bed. In summer, a baseflow component of discharge, relatively depleted of 18 O, is diluted by water more enriched in 18 O. Glacier ice meltwater with a high d 18 O value passes rapidly through channelized systems, and emerges in the glacier river within a few hours. Headward extension of the systems in late summer may tap water stored within the glacier since the previous summer's close-down. Stored water also is released during early melt-season events, when the low-capacity drainage systems cannot accommodate inputs. The high d 18 O value indicates that the probable source of the released water is glacier ice or low-altitude snowfall. Stratigraphic variations of d 18 O values, resulting from changing weather conditions, characterize the accumulating winter snowpack. During the melt season, the mean d 18 O value of the residual pack rises. The water leaving it, depleted of 18 O, passes slowly through the glacier, smoothing out variations of supply. d 18 O values of rain vary between and within events, and their effect on glacier-river d 18 O values is unpredictable. OXYGEN ISOTOPES AND INTERNAL DRAINAGE SYSTEMS AT AVALLEY GLACIER Water sourcesThe water issuing from a glacier in summer is a mixture. Its sources include snow meltwater, glacier ice meltwater and rainfall (Fig. 2). Smaller contributions may come from melting firn, superimposed ice, regelation ice and ground-water. These sources differ in isotopic composition, and their relative contributions to total discharge are reflected in the composition of the river water emerging at a particular time. The contributions of each source vary on time-scales ranging from a few minutes, during discrete``outburst events'' , to decades, within which major changes of glacier mass balance, driven by climatic variations, may be experienced.Both temporal and spatial variations of d 18 O values characterize the snow which accumulates at a glacier in winter.

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Section: Discussionmentioning

confidence: 99%

Oxygen isotopes in glacier-river water, Austre Okstindbreen, Okstindan, Norway

Theakstone

2003

J. Glaciol.

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“…Rainfall events have been found to significantly increase ablation as latent heat is released from the freezing of raindrops on contact with ice (Ishikawa et al, 1992;Marcus et al, 1985;Takeuchi et al, 1999). Such events have been related to short-term variations in surface velocity (Andreasen, 1983;Goodsell, 2005).…”

Section: Introductionmentioning

confidence: 99%

Seasonal Variation in Ablation and Surface Velocity on a Temperate Maritime Glacier: Fox Glacier, New Zealand

Purdie

Brook

Fuller

2008

Arctic, Antarctic, and Alpine Research

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Seasonal variations in ablation and surface velocity were investigated on the lower part of Fox Glacier, South Westland, New Zealand. A large variation between summer and winter ablation was recorded, with daily averages of 129 mm d 21 and 22 mm d 21 , respectively. Variations in measured climatic variables were found to account for ,90% of variation in ablation during both summer and winter seasons, with significant increases in ablation occurring in conjunction with heavy rainfall events. Surface velocity also showed seasonality, averaging 0.87 m d 21 during summer and 0.64 m d 21 in winter, a reduction of ,26%. It is thought that the general reduction in velocity during winter can be attributed to a decrease in the supply of surface meltwater to the subglacial zone. Short-term velocity peaks appeared to coincide with heavy rainfall events, with surface velocity responses typically occurring within 24 hours of each rainfall event. During winter, moderate rainfall events (#100 mm over 24 hours) created a surface velocity response up to 44% greater than the prevailing velocity. Though difficult to deconvolve, magnitudes of surface velocity response to rainfall inputs appear linked to time lags between rainfall events and subglacial drainage efficiency and water storage. The longer-term dynamics of Fox Glacier appear linked to fluctuations in the Southern Oscillation Index (SOI), with positive mass balances of Southern Alps' glaciers appearing to mirror negative SOI (El Niñ o) conditions. Given the calculated response time of ,9.1 years for Fox Glacier, the current terminus advance may be linked to mass gains reported in the mid-1990s, with current mass balance gains perhaps leading to terminus advances ,9 years hence.

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“…The observations are summarized in Table II and Until 24 July, glacier-river discharge and conductivity displayed a regular daily pattern, with a single maximum and minimum. The decline of conductivity from 17 July undoubtedly reflected an increase in the contribution made to total discharge by melt water derived from the glacier'S upper surface, a usual development through the ablation period (Collins and Young, 1981;Andreasen, 1985). A declining trend of 6 18 0 values, which ended on 17 July, reflected the decreasing contribution made to river discharge by the melting of snow which had accumulated in the lower part of the catchment during the previous winter.…”

Section: The 1984 Drainage Of the Ice-dammed Lakementioning

confidence: 99%

Drainage of the Austre Okstindbreen Ice-dammed Lake, Okstindan, Norway

Knudsen¹,

Theakstone

1988

J. Glaciol.

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Observations of the discharge, electrical conductivity, cationic content, and isotopic composition of glacier-river water indicate that drainage of the lake dammed at the margin of the glacier Austre Okstindbreen, Okstindan, Norway, is preceded by disruption of the glacier’s drainage system(s). Annual studies over a period of 12 years have demonstrated that intense storm precipitation, changes of ablation conditions, and the stage of development of drainage systems all may play a role in triggering drainage of the ice-dammed lake. Water temperature may influence the course of the outburst. The lake has drained on at least ten occasions in the last 12 years. Three of the events (1979, 1985, and 1986) occurred early in the summer, whilst melting of the winter’s snow cover was contributing substantially to glacier-river discharge: high basal water pressure and rapid sliding may have facilitated disruption of drainage conditions within the glacier. In 1982, the lake drained during a severe storm, in 1977 and 1984 shortly after a period of heavy rainfall. During the 1977 and 1984 events, water under pressure burst up through the glacier surface. The lake basin remained partly filled throughout one summer (1980): in-flow of water was balanced by out-flow into the glacier.

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Basal Sliding at the Margin of the Glacier Austre Okstindbre, Nordland, Norway

Cited by 10 publications

References 0 publications

Oxygen isotopes in glacier-river water, Austre Okstindbreen, Okstindan, Norway

Oxygen isotopes in glacier-river water, Austre Okstindbreen, Okstindan, Norway

Seasonal Variation in Ablation and Surface Velocity on a Temperate Maritime Glacier: Fox Glacier, New Zealand

Drainage of the Austre Okstindbreen Ice-dammed Lake, Okstindan, Norway

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