Glaciers of the Karakoram Himalaya

Fig. 1The Karakoram mountain range has the greatest concentration of glaciers on mainland Asia, comprising about 18,000 km2. The glaciers are large stores of fresh water in an otherwise extremely dry region of the continental interior. They are of critical importance to the flows of the Indus and Yarkand Rivers. Most of the ice drapes the main crest of the Greater Karakoram. There are hundreds (see image 1) of small and intermediate ice masses, but twelve large glaciers make up almost half of the total cover.

 

 


 


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They include a majority of the biggest valley glaciers outside high latitudes. Siachen is the largest in area (1,200 km2) and length (75 km). Baltoro is the second largest in area (760 km2) and has the greatest elevation range – 5,240 m from the terminus up to the summit of K2 (8,611 m). The watersheds of all these glaciers are at exceptional elevations. This partly explains why they also have elevation ranges equaled by few other glaciers, even in the rest of the Himalaya (see figure 1 ????). As a result, climate and other conditions in the upper glacier areas differ greatly from their lower parts; one of several reasons why the Karakoram glaciers appear unusual.

Their climatic environment is influenced by westerly winds and storms in the winter half of the year, and by monsoonal storms in summer. The limited measurements available show that around 2/3rds of snow falls in winter and about 1/3rd in summer – the reverse of the Greater Himalayan glaciers where summer monsoonal snowfall is dominant. High pressure systems that develop over Inner Asia, especially the Tibetan Plateau, affect the strength and intensity of the other two weather systems, and the duration of clear weather in the mountains. The latter is important for mountaineers and photographers, but critical for the amount of melting of the glaciers in summer. As in all great mountains, rugged topography and high elevations strongly modify and complicate the climate (see image 2).

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Studies on Biafo Glacier in the 1980s proved, for the first time, that the heaviest precipitation in the Karakoram is snowfall on the higher zones of the glaciers. The maximum precipitation amounts occur between 4,800 and 6,000 m above sea level (asl), much higher than has been measured anywhere else in the world. The water equivalent of the snowfall varies between one and two metres– which means 5 metres or more of snow per year (see image 3 ????). The amounts are ten times greater than in valley weather stations below about 3,000m. However, it is also important to be aware that, over most of the high Karakoram, snow never gets to build up in this way. It falls where there are steep slopes or high winds and descends as avalanches to the glacier surfaces.

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The importance of snow and ice avalanches in the glacier environment cannot be over-emphasised. They are a well-known hazard for mountaineers, and create spectacular sights. However, their greatest role is as the main inputs of snow and ice for the glaciers. The higher parts of glacier basins generally feature high rock walls and steep icefalls (see image 4 ????). As much as 50-80% of areas above about 4500 m asl consist of walls steeper than 40 deg., The snow that falls there tends to slide off or blow away immediately or, if it does build up, to be quite unstable. Another important process is wind action that blows the snow across and up slopes to deposit it as snow cornices at the head of more sheltered or lee slopes. Cornice collapses are another source or trigger of large avalanches. Countless small ice masses or ‘glacieretes’ do form at breaks of slope, in narrow canyons, niches and chutes, but are also quite unstable. They too produce ice avalanches that descend to the main glaciers (see image 5).

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In fact, the avalanche-nourished or “Turkestan”- type glacier has been seen as typical of the Karakoram for almost a century. The larger glaciers like Baltoro, with high elevation ice streams hemmed in by rock walls, have been called ‘firn-kettle’ glaciers. Avalanches are again the main source of nourishment in the ‘kettles’, although direct and wind-drifted snow can be quite important too. A few glaciers, including Siachen, Biafo, Rimo and Chiantar, are unusual for the Karakoram in having extensive high elevation snow basins. In these cases direct snowfall is the main source of the ice (see image 6). While not so typical of the region, they do offer relatively safe opportunities to measure high altitude snowfall amounts.

Another well-known feature reflects the importance of avalanches: the extraordinary quantities of debris covering the lower parts of the glaciers (see image 7). They were originally brought down with the avalanches, or by rock falls from the same high rock walls. The heavy debris covers protect the ice from the sun’s rays, reducing or preventing ablation over the lower parts of the glaciers. It is one factor in the great length and low altitude penetration of many glaciers. However, another aspect of the relations of debris and glacier ablation may be even more significant. The dry lower valleys, windiness and high rates of erosion help create a very dusty environment. Snow and ice tend to be relatively dirty. In a couple of sunny days after a storm, veneers of dust and dirt are observed to build up quickly on ice or snow surfaces. And whereas thick debris protects the ice, thin layers of dirt, scattered rock fragments, and dust particles increase ablation.

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Measurements in the Karakoram show that veneers of dirt on the ice, up to a thickness of about 3 cm, can increase ablation rates by 50% or more compared to clean ice (see figure 2 ????). This is because, being darker, the dirt and dust particles absorb much more solar energy; being thinner the heat passes more readily to the ice and helps to melt it. Thus, if the heavy debris covers on lower glacier areas and medial moraines protect the ice, the thin and scattered debris of mid-elevation areas has the opposite effect, increasing ablation rates.

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In this regard it is notable that something like 80% of the melt water from Karakoram glaciers derives from elevations between 3,800 and 4,800 m asl. Again the vertical aspect of climate, as it controls seasonal conditions, is a vital factor. Most snowmelt is confined to a few months of summer, and 90% of glacier melting occurs in less than two months. This is usually in July and August, when conditions warm up in a critical zone between 3,800 and 4,800 m asl and seasonal snow has been melted to expose the ice. Higher than this, warm temperatures are rare. Above 5,000 m or so is the zone of perennial sub-zero temperatures. Ice ablation also declines sharply below 3,800 m where protection by heavy debris serves to offset not only higher temperatures and longer sunshine hours, but seasonal temperatures above zero that last much longer than in the higher areas.

Where there is relatively clean ice or that thinly veneered with dust or dirt, some5-7 m of ice is ablated annually at elevations of about 4,000 m asl, declining to zero at about 5,000 m (see image 8). Where ice reaches as low as 2,500 m ablation can reach 18 m per year on bare and dirty ice and some melting occurs even in mid-winter. However, debris covers at these elevations mean average ablation is less than 3-4 cm.

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A final point about debris-covered ice is that there is still a lot of localized melting and redistribution of debris, and it produces distinctive features too. Rapid ablation will occur wherever ice is exposed, especially because it usually has a thin veneer of dirt. The well-known ‘ice-ships’ in otherwise debris blanketed areas and the widely-present ice facets, often surrounding small on-ice ponds, melt at the highest rates. However, they form only a small part of the whole surface. Immediately around them the thicker debris slows or stops ablation. As a result, the bare ice surfaces, which mostly have quite steep slopes, continually retreat causing the debris above and beside them to slide down. Time-lapse photography of these areas shows, over a few weeks, days even, a complete inversion of the topography on the glacier. The prominent debris-covered mounds become areas of debris-filled pits, and vice versa. A common mistake is to assume that the many debris-covered cones or hummocky surface of these glaciers are permanent and consist mainly of the debris when, in fact, the relief is largely in the underlying ice. The many sculptural forms that result from these interactions of ice, debris and sunshine, have fascinated observers from the earliest visits to the Baltoro and other Karakoram glaciers.

Two hazardous glacier phenomena have exceptional development in the Karakoram; surging glaciers, and catastrophic glacier lake outburst floods (GLOFs). Surges are relatively short lived events in which there are sudden, large transfers of ice from the upper to the lower part of the glacier. Ice movement generally increases by an order of magnitude, sometimes two (see image 10 ????). Some 34 surges are documented in the Karakoram over the past 150 years, involving 22 glaciers. Many other glaciers have features associated with surge behaviour. If a surge reaches populated areas it can engulf occupied land, disrupt local communications, and destroy irrigation channels. Surge can also give rise to sudden floods that spread the destruction far down the valleys (see image 11).

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Over the past 200 years some 62 glaciers are known to have formed partial or complete cross-valley barriers on the Upper Indus streams, and there have been more than 60 destructive glacier lake outburst floods. Some were large enough to reach and cause damages as far as the Indus plains. It is important to note, however, that all the large GLOFs in this region have been due to glaciers advancing across river valleys. The risks are quite different from the dangerous lakes reported recently and due to glacier retreat, for example in Nepal and Bhutan in the Eastern Himalaya.

In sum, the glaciers of the Karakoram are unique in character, important factors in regional water supply and a source of some of the more destructive glacier hazards.

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Kenneth Hewitt

Professor Emeritus, Geography and Environmental Studies
Founder Member and Research Associate, Cold Regions Research Centre
William Laurier University, Ontario, Canada

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FOR FURTHER READING

  • Batura Investigations Group. 1979. The Batura Glacier in the Karakoram Mountains and its variations. Scientia Sinica 22(8): 958-74.
  • Belo, M. et al 2008 The recent evolution of Liligo Glacier, Karakoram, Pakistan and its present quiescent phases, Annals of Glaciology, 48, 171-176.
  • Dainelli, G. 1922-28 Relazione Scientifiche della Spedizione Italiana de Filippi, nell’Himalaia, Caracorum e Turchestan Cinese (1913 14). Serei II. Resultati geologici e geografici. Zanichelli, Bologna.
  • Finsterwalder, R. 1937 Die Gletscher des Nanga Parbat, Zeitschrift fur Gletscherkunde 25, 57-108
  • Hewitt K. 1982 Natural dams and outburst floods of the Karakoram Himalaya in ed. Glen. J. Hydrological Aspects of Alpine and High Mountain Areas. Internat. Hydrol. Assoc. (I.A.H.S.) Publ. no.138 259 269
  • Hewitt K. 2005 The Karakoram Anomaly? Glacier expansion and the ‘elevation effect’, Karakoram Himalaya, Inner Asia Mountain Research and Development: Special Issue – Climate change in mountains, v. 25, no.4
  • Hewitt K. 2007 Tributary glacier surges: an exceptional concentration at Panmah Glacier, Karakoram Himalaya, Journal of Glaciology¸ 53, No. 181, 181-188
  • Hewitt K, et al. 1989. Hydrological investigations at Biafo Glacier, Karakoram Himalaya, an important source of water for the Indus River. Annals of Glaciology: 13: 103-108.
  • Mattson LE, and Gardner JS. 1989. Energy exchanges and ablation rates on the debris-covered Rakhiot Glacier, Pakistan. Zeitschrift fur Gletscherkunde und Glazialgeologie 25(1): 17-32.
  • Mihalcea, C. et al, 2006 Ice ablation and meteorological conditions in the derbis-covered area of Baltoro glacier, Karakoram, Pakistan. Annals of Glaciology, 43, 292-299
  • Shipton, E.E. 1938 Blank of the Map Hodder and Stoughton, London
  • Shroder, J.F. Jr. (ed.) 1993 Himalaya to the Sea : geology, geomorphology and the Quaternary. Routledge, New York, 132 158
  • von Klebelsberg, R. 1925 26 Der Turkestanische Gletschertypus. Zeitschrift fur Gletscherkunde 14, 193 209.
  • Wake CP. 1989. Glaciochemical investigations as a tool to determine the spatial variation of snow accumulation in the Central Karakoram, Northern Pakistan. Annals of Glaciology 13: 279-284.

4 Comments


  1. derekpm
    Jul 13, 2009

    Rather interesting. Has few times re-read for this purpose to remember. Thanks for interesting article. Waiting for trackback.


  2. SADHANA YADAV
    Jun 19, 2010

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    SADHANA YADAV(INDIA)


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    Aug 26, 2010

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