A cut-and-closure origin for englacial conduits in uncrevassed regions of polythermal glaciers

被引:73
作者
Gulley, J. D. [1 ,2 ]
Benn, D. I. [2 ,3 ]
Mueller, D. [2 ,4 ]
Luckman, A. [5 ]
机构
[1] Univ Florida, Dept Geol Sci, Gainesville, FL 32611 USA
[2] Univ Ctr Svalbard UNIS, Dept Geol, NO-9171 Longyearbyen, Norway
[3] Univ St Andrews, Sch Geog & Geosci, St Andrews KY16 9AL, Fife, Scotland
[4] Tech Univ Carolo Wilhelmina Braunschweig, D-38106 Braunschweig, Germany
[5] Univ Coll Swansea, Sch Environm & Soc, Glaciol Grp, Swansea SA2 8PP, W Glam, Wales
关键词
TERM VELOCITY VARIATIONS; GREENLAND ICE-SHEET; TEMPERATE GLACIERS; WATER-FLOW; SVALBARD; DRAINAGE; HYDROLOGY; EVOLUTION; RADAR;
D O I
10.3189/002214309788608930
中图分类号
P9 [自然地理学];
学科分类号
0705 ; 070501 ;
摘要
On uncrevassed regions of polythermal glaciers, englacial conduits can form by incision of supraglacial stream channels followed by roof closure. The origin and evolution of examples in Longyearbreen, Svalbard, and Khumbu Glacier, Nepal, were determined by speleological survey. The development of perennial incised channels requires that incision is significantly faster than glacier surface ablation, and thus will be favoured by high meltwater discharges in combination with cool climatic conditions or thick debris cover. Incised canyons can become blocked by drifted winter snow, refrozen meltwater, ice rafting from non-local sources (allochthonous breccias) and roof collapses (autochthonous breccias). Conduit closure can also occur in response to ice creep, particularly at depth. Following isolation from the surface, englacial conduits continue to evolve by vadose incision down to local base level. In the case of Longyearbreen, incision allowed the channel to reach the glacier bed, but on Khumbu Glacier deep incision is prevented because an effectively impermeable terminal moraine provides a high base level for the glacier drainage system. During our period of observations, deeper parts of the Longyearbreen conduit became blocked by a combination of ice accumulation and creep, causing the stream course to be re-routed to higher levels. On that glacier, incision, blockage and upward re-routing are cyclic. We conclude that 'cut and closure' is the dominant mechanism of englacial conduit formation on uncrevassed regions of polythermal glaciers.
引用
收藏
页码:66 / 80
页数:15
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