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The Pamir Times twitted this image after the valley blocking incidents
Courtesy: The Pamir Times
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18th July ‘The Pamir Times’, leading English daily of Gilgit-Baltistan in Pakistan occupied Kashmir, reported that a significant valley blocking event occurred at Ishkoman valley, high up in the mountains of Gilgit in northern Pakistan. The same report was also delivered by the mainstream Pakistani newspaper ‘The Dawn’. It quoted that “A small glacier melt has swollen Barsuwat Nullah in the Ishkoman valley of Ghizer district, Gilgit-Baltistan, creating an artificial lake and blocking the flow of the Immit River. The water has submerged more than 30 houses, cultivated land, a link road and cattle farms and washed away over a dozen vehicles and hundreds of cattle head in the upstream areas.”
Further detail was received with the press release of Deputy Commissioner of Ghizer, Deputy Md. Shuja Alam. The Deputy Commissioner said that “the Barsuwat glacier started melting on Tuesday at about 7pm. Water from the melting glacier, containing mud and stones, fell into Barsuwat Nullah and caused flooding. The nullah ultimately falls into the Immit River whose flow has been blocked and the stagnant water has created an artificial lake similar to Attabad Hunza Lake, disconnecting upstream villages from other areas.”
I was unaware of this incident though I have great interest on Himalayan glaciers. I published a couple of research papers about the impact of global warming on glaciers, glacial lakes and cloudburst events in Garhwal Himalaya. I have another published paper on 2013 cloudburst event in Kedarnath and surrounding areas. This paper is popular in different academic sites. It was the highest search paper in Academiaedu for conjugative two weeks in December 2014. I was informed about the Ishkoman incidents by the director of Glacial Studies and a member of an associated blog. I was asked to give comments on the probable causes of frequent glacial melting and valley blocking incidents in Karakoram mountain region of Gilgit-Baltistan. They also produced me the Planet Lab satellite image (Planet Application Program Interface: In Space for Life on Earth, San Francisco) of the valley blocking site of Ishkoman valley.
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Planetscope image of the aftermath of the Ishkoman glacial debris flow
Modified by the author
Courtesy: Planet Lab
After receiving the email, I have gone through several reports, research papers and articles about the said matter. Majority of the researchers blamed global warming for the faster melting of small glaciers in the Karakoram which is very similar to other areas of Himalaya. But, I feel that it is a generalised statement without analyzing the local factors and phenomenon. I have tried to assessment the fact with the theory of Karakoram Anomaly and Thermodynamics of Glaciers. I have informed them about my findings in details with specific logic. However, here I am discussing the facts in a descriptive manner so that everybody could understand it. Before, discussing the valley blocking incidents of Ishkoman valley and others part of Karakoram, I would like to discuss the glacier melting and glacial lake outburst flood (GLOF) event of Himalaya. Majority of the researchers have applied this theory to explain the glacier melt and valley blocking incidents of Karakoram mountain region which is a different phenomenon.
Cause of Glacier Melt and Glacial Lake Outburst Flood (GLOF) Event of Himalaya:
The mean temperature of the Earth has been increased by 0.75° C during the last century due to global warming that causes the faster destruction of mountain or valley glacier. This phenomenon is already witnessed in several places of Himalaya where glacier and glacial lakes are changing alarmingly. Glacier retreating rate in Himalaya is 10 to 60 m per year. In most of the cases, the supraglacial ponds (A supraglacial pond is a small body of super cool still water on the top of a glacier) are growing quickly and merging with each other. So that glaciers are melting faster than the past and supraglacial ponds lasting over decades and have become lakes. In Gharwal Himalaya, such glacial lakes have been increased as high as 800 per cent over the last 40years. Thus, retreating glaciers produce vast and long lakes, many kilometres in diameter. These lakes are bounded by moraines and associated debris supplied by the glaciers. Rapid melting of a glacier or heavy downpour can stir up these lakes, creating glacial lake outburst flood (GLOF). In such a flood, the lake water rushes down the valley as the flash flood and often causes valley blocking incidents.
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Location of Ishkoman Valley:
This valley is located on the northern portion of Gilgit-Baltistan, south of Pamir in Ghizer district of Pakistan Occupied Kashmir. It shares the boundary with the Wakhan corridor of Afghanistan. The average elevation of this valley ranges between 2100 m to 3700 m. This valley is very close to the junction of Karakoram and Hindu Kush Mountains. It is a high mountain valley surrounding by snow-capped peaks and various small glaciers.
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| Location of Ishkoman Valley Source: Author |
Probable Cause Glacier Melt and Valley Blocking Incidents of Ishkoman, Gilgit-Baltistan :
I think the incident of Ishkoman of Gilgit-Baltistan is a different issue. There is a permanent 'vortex' of cold air over the Karakoram mountain region during summer, causing the increase of the glaciers in spite of global warming. Nathan Forsythe and his team from Newcastle University, UK, have identified a large scale vortex, centred over the Karakoram. In winter, the vortex affects the temperature over the Karakoram and entire Himalayan Range, spreading over 2000 km. But in summer the vortex has a limited effect only over the Karakoram and south Pamir. The vortex of trapped cold air in and around Karakoram Mountains makes this area cooler than other parts of Himalaya. This phenomenon is called the Karakoram Anomaly. Due to Karakoram Anomaly, there is a steady accumulation of snow and consequently the growth of glaciers even in summer. Where other parts of the Himalaya experience the opposite scenario.
Normal snowfall season of Gilgit-Baltistan is October to January and this snow converts into glaciers. But due to Karakoram Anomaly, the valleys are experiencing snowfall even in April. The summer snow, cannot convert into glaciers, they remain as firn and the glacier increases in weight. Due to the excess weight, the glacier begins to deform and flows downhill, the crevasses are formed in various sizes depending on the rate of abrasion and stress. This downward movement also creates thermodynamic instability within the glacier and they turn into polythermal in nature. In case of the polythermal glacier, the upper part of an ice column is cold, but the surface and the base are at melting temperature. So, the downward movement increases further due to the percolation of meltwater as the form of microscopic and macroscopic water system within the glacier (Fig:1). In this situation, a sudden influx of temperature (heat waves in summer or local contribution of temperature) melts the firn very fast and the latent heat transported within rest part of the glacier, causes a sudden collapse of the glacier along large crevasses. This collapse acts as a stimulator for melting rest of the glacier from the bottom very fast.
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| Fig: 1 Microscopic and macroscopic water system within a polythermal glacier |
The glacier meltwater moved faster along the sub-glacial channel (Barsuwat Nullah in Ishkoman valley) with forwarding of glacial moraines and associated debris. This debris was ultimately stored over the Immit River near the meeting point of Barsuwat Nullah and cratered the artificial lake. Geology of the Ishkoman valley and surrounding areas consist of dolomite, limestone, slate, conglomerate, gneiss etc. It indicates, there are plenty of cementing materials which helped the debris to be accumulated and formed the lake wall.
I think this event is not uncommon in the Karakoram and Pamir region because, this type of glaciers is typically smaller, less stable and susceptible to retreat due to thermodynamic instability. The formation of an artificial lake is also very common in the meeting point of a sub-glacial and fluvial channel due to the abundant supply of glacial debris. This type of small glaciers is also very sensible with the influx of local temperature rather global warming. The recent development activities of CPEC projects may have increased the soot and dust in this area which may have impacted on local small glaciers. So, there is a scope for further study on it.
