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CURRENT SCIENCE, VOL. 92, NO. 1, 10 JANUARY 2007 69

http://www.ias.ac.in/currsci/jan102007/69.pdf

*For correspondence. (e-mail: anilkul@sac.isro.gov.in)

 

 

Glacial retreat in Himalaya using Indian

Remote Sensing satellite data

 

 

Anil V. Kulkarni1, I. M. Bahuguna1, B. P. Rathore1, S. K. Singh1,

S. S. Randhawa2, R. K. Sood2 and Sunil Dhar3

 

 

1Marine and Water Resources Group, Space Applications Centre, Indian Space Research Organization, Ahmedabad 380 015, India

 

 

2Himachal Pradesh Remote Sensing Cell, Shimla 171 009, India

 

 

3Department of Geology, Government College, Dharamsala 176 215, India

 

 

The Himalayas possess one of the largest resources of

snow and ice, which act as a huge freshwater reservoir.

Monitoring the glaciers is important to assess the

overall reservoir health. In this investigation, glacial

retreat was estimated for 466 glaciers in Chenab, Parbati

and Baspa basins from 1962. Expeditions to Chhota

Shigri, Patsio and Samudra Tapu glaciers in Chenab

basin, Parbati glacier in Parbati basin and Shaune

Garang glacier in Baspa basin were organized to identify

and map the glacial terminus. The investigation has

shown an overall reduction in glacier area from

2077 sq. km in 1962 to 1628 sq. km at present, an

overall deglaciation of 21%. However, the number of

glaciers has increased due to fragmentation. Mean

area of glacial extent has reduced from 1.4 to 0.32 sq.

km between the 1962 and 2001. In addition, the number

of glaciers with higher areal extent has reduced

and lower areal extent has increased during the period.

Small glaciarates and ice fields have shown extensive

deglaciation. For example, 127 glaciarates and

ice fields less than 1 sq. km have shown retreat of 38%

from 1962, possibly due to small response time. This indicates

that a combination of glacial fragmentation,

higher retreat of small glaciers and climate change are

influencing the sustainability of Himalayan glaciers.

Keywords: Glaciers, glaciarates, Himalayas, ice fields,

retreat.

OVER the past three million years, the earth’s surface has

experienced repeated large periods of glaciation, separated

by short warm interglacial periods. During the peak of

glaciation approximately 47 million sq. km area was covered

by glaciers, three times more than the present ice

cover over the earth1. A number of ideas were proposed

to explain repeated cycle of glaciations on the earth. One of

the explanations is related to natural variation in the earth’s

orbit around the sun. These orbital cycles (100,000, 41,000

and 22,000 years) can cause 10% variation of incoming

solar radiation in various parts of the globe2. These regular

changes in the amount of sunlight reaching the surface of

the earth might have produced repeated cycles of glaciation.

This can also produce asynchronous behaviour in

the development of glacial extent in the northern and

southern hemisphere. This aspect was extensively studied in

tropical Andes; maximum extent of last glaciation was

estimated3 around 34,000 yrs BP before present and retreated

by 21,000 yrs BP. This cycle of glaciation is different

from that reported in the northern hemisphere, where

the peak of the last glaciation was estimated approximately

about 17,000 to 21,000 years ago4.

Natural variations in the earth’s orbit are well synchronized

with atmospheric variations in methane and carbon

dioxide, leading to repeated cycle of glaciations. However,

this natural cycle might have altered due to the greenhouse

effect caused by man-made changes in the earth’s environment.

Some of the hypotheses suggest this alteration might

have started long before the beginning of the Industrial

Revolution2. Invention of agriculture about 11,000 years

ago might have led to large-scale deforestation and rice

cultivation. However, this pace of change might have accelerated

from the beginning of the Industrial Revolution.

This has led to an increase5 in global temperature by 0.6 ±

 

 

0.2°C from 1900. In addition, recent development in climate

modelling suggests that the existing greenhouse gases

and aerosols in the atmosphere have led to the absorption

of 0.85 ± 0.15 W/sq.m more energy by the earth than that

emitted to space. This means additional global warming

of about 0.6°C has occurred without further change in

atmospheric composition6. Mass balance is one of the

important parameters which can be influenced by global

warming. Mass balance is usually referred to as a total

loss or gain in glacier mass at the end of the hydrological

year7. Geographical parameters which can influence mass

balance are area–altitude distribution and orientation, since

higher altitude has lower atmospheric temperature. In addition,

orientation and amount of slope can influence amount

of solar radiation received on the slope8. Influence of these

parameters on glacial mass balance is studied in the

Baspa basin9,10.

Global warming has remitted in large-scale retreat of

glaciers throughout the world11. This has led to most glaciers

in the mountainous regions such as the Himalayas to

recede substantially during the last century12–14 and influence

stream run-off of Himalayan rivers15. However,

 

 

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CURRENT SCIENCE, VOL. 92, NO. 1, 10 JANUARY 70 2007

 

 

Figure 1. Location map of Chenab, Parbati and Baspa basins, Himachal Pradesh (HP).

 

 

Table 1. Satellite data used in the analysis

Basin Sensor Spatial resolution (m) Date of acquisition

Parbati LISS-IV 5.8 16 July 2004

Baspa LISS-III 23 25 August 2001

11 September 2000

Chenab LISS-III 23 27 August 2001

30 August 2001

 

 

Table 2. Salient specifications of LISS-IV sensor of IRS-P6

(from Roy17)

Specification LISS-IV

Spectral bands (mm) 0.52–0.59

0.62–0.68

0.77–0.86

Spatial solution 5.8 m at nadir

Swath 23.9 km

Quantization 7 bits

Saturation radiance B2: 55

(mw/cm2/sr/mm) B3: 47; B4: 31.5

 

 

monitoring of Himalayan glaciers is normally difficult

using conventional methods due to the rugged and inaccessible

terrain. Therefore, field-based records have been

made at selected Himalayan glaciers. This may not provide

a complete and representative scenario of glacial retreat.

In this investigation, changes in glacial extent are

reported for 466 glaciers in Himachal Pradesh, covering

three highly glacerized basins of Chenab, Parbati and

Baspa (Figure 1). These are important river basins for Indian

economy, as numerous power projects are under operation

and construction here16. Therefore, changes in glacial extent

and their influence on river run-off are important to plan

future strategies of power generation.

 

 

Methodology

 

 

This investigation was carried out using data from a number

of Indian Remote Sensing satellites. In Parbati basin

LISS-IV data of IRS-P6, and in Baspa and Chenab basins

LISS-III data of IRS-1D were used (Table 1). IRS-P6 satellite

was launched on 17 October 2003 and satellite images

of Parbati basin were collected in the summer of 2004.

Spatial resolution of this sensor is 5.8 m and data are

available in three bands. Therefore, this sensor can be

used to monitor small glaciers and ice fields. Specifications

of LISS-IV sensor of IRS-P6 satellite17 are given in

Table 2. The oldest information about glacial extent is

available on Survey of India topographic maps, surveyed

in 1962, using vertical air photographs and limited field

investigations. Mapping of glacial extent in 2004 was carried

out using LISS-IV images and in 2001 using LISS-III

images. Images covering July–September period were selected,

because during this period snow cover is at its minimum

and glaciers are fully exposed. Glacier boundary

was delineated using topographic maps and digitized using

Geographic Information System. On satellite images

glacial boundary was mapped using standard combinations

of bands. Image enhancement technique was used to

enhance the difference between glacial and non-glacial areas.

Field investigations were carried out at five glaciers

to assess position of the snouts. These include Shanue

Garang glacier in Baspa basin, Parbati glacier in Parbati

basin and Chhota Shigri, Samudra Tapu and Patsio glaciers

in Chenab basin. Snout positions of selected glaciers were

marked using Global Positioning System (GPS) and by

comparing the relative position of snouts with geomorphologic

features such as moraines, origin of streams

from snouts and moraine-dammed lakes. Glacier retreat

was measured along the centreline. Since GPS instrument

cannot be easily mounted on the terminus, due to safety

consideration, relative position of the terminus was estiRESEARCH

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CURRENT SCIENCE, VOL. 92, NO. 1, 10 JANUARY 2007 71

 

 

mated using geomorphological features. This means glacial

retreat can be estimated by combining field and satellite

observations. This procedure is now being improved

using a combination of laser range finder and GPS, where

the distance between a fixed point on stable land and glacial

terminus will be estimated. Repeated observations

will provide the amount of glacier retreat. This will be an

important step forward, as it will provide independent validation

of remote sensing-based methodology.

Glacial depth is normally estimated using radio-echo

sounding method18–20. In the Indian Himalayas, such measurements

are few; however volume of glacier-stored water

can be estimated using various approximate methods. One

of the earliest methods to estimate glacier depth was based

upon worldwide observations (including Nepal Himalayas)

of a large number of glaciers and an approximate relationship

between glacier type, areal extent and depth was developed.

Glacier depth can be inferred using geomorphological

classification and areal extent21. Both of these parameters

can be obtained using remote-sensing technique. In geomorphological

classification, glaciers are identified either as

 

 

Figure 2. Spectral reflectance of snow, ice, contaminated snow, vegetation,

and soil. Observations taken using spectral radiometer near Manali,

HP. Note changes in reflectance as snow changes into ice and as

snow and ice are covered by rock debris.

 

 

Figure 3. Satellite imagery of glacier number 52H12003 and

52H12004 of LISS-IV sensor showing glacial boundary of 1962 and

2004. These are small mountain glaciers showing negligible accumulation

area. Maximum altitude of these glaciers is around 5200 m. This is

close to the snow line at the end of ablation season and such glaciers

are expected to experience terminal retreat.

 

 

compound or simple glaciers. In a compound glacier, two

or more tributaries merge together to form a valley glacier.

The simple glacier has a single, well-defined accumulation

area21. Separate tables are used to obtain depth depending

upon the areal extent. This method was further improved

by a large number of field observations in the Himalaya.

A specific relationship between glacier area and depth has

been developed for the Himalayan glaciers22:

 

 

H = –11.32 + 53.21 F 0.3,

where H is the mean glacier depth (m) and F is the glacier

area (sq. km).

Since this method has been developed using depth information

of Himalayan glaciers, it was used to estimate volume

of glaciers and loss in their volume between 1962 and

2001. The error was estimated22 as 10–20%. The volume

of mountain glaciers23 is proportional to their area raised to

 

 

Figure 4. Field photograph showing moraine-dammed lake near

Samudra Tapu glacier, Chenab basin, HP.

 

 

Figure 5. Satellite imagery showing moraine-dammed lake and terminus

of Samudra Tapu glacier, Chenab basin, HP.

 

 

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CURRENT SCIENCE, VOL. 92, NO. 1, 10 JANUARY 72 2007

 

 

Figure 6. Field photograph of terminus region of Chhota Shigri glacier, Lahaul and Spiti district, of HP taken in

1988 and 2003. In 1988, glacial ice is exposed on the surface and small portion of the terminus is covered by debris.

By year 2003, the entire terminus zone is covered by debris.

 

 

Table 3. Basin-wise loss in glacier area in Chenab, Parbati and Baspa basins

Glacier area (sq. km) Volume (cubic km)

Basin Glacier number 1962 2001–04 Loss (%) 1962 2001–04 Loss (%)

Chenab 359 1414 1110 21 157.6 105.03 33.3

Parbati 88 488 379 22 58.5 43.0 26.5

Baspa 19 173 140 19 19.1 14.7 23.0

Total 466 2077 1628 21 235.2 162.73 30.8

 

 

Figure 7. Field photograph of terminus region of Patsio glacier,

Bhaga river basin, Lahaul and Spiti district, HP. Shape of glacial terminus

is concave, suggesting retreating glacier. Glacier ice can be seen

clearly and debris cover is relatively less on this glacier.

 

 

a power of about 1.36. A small difference between geographic

regions (North America, Arctic, Europe and Central Asia)

was observed. In Central Asia, the volume of mountain

glaciers was observed proportional to their area raised to

a power of about 1.24.

 

 

Estimation changes in glacial extent

 

 

Identification and mapping of glacier boundary and terminus

is one of the important aspects of estimation of retreat.

If glaciers are not covered by debris, identification

of snow, ice and rock on satellite images is possible due

to substantial difference in spectral reflectance. Spectral

reflectance curves of fresh snow, ice, dirty snow and rock

are given in Figure 2. These reflectance curves were obtained

around Manali, Himachal Pradesh. These results indicate

substantial difference between snow and rock. In addition,

reflectance of ice is also substantially different compared

to that of rock in the spectral region between visible and

SWIR (Figure 2). A satellite imagery of LISS-IV sensor

showing glacial boundary of 1962 and 2004 is given in

Figure 3. Identification and mapping of glacial terminus

in a satellite imagery is normally difficult if glaciers are

 

 

Figure 8. Field photograph of dead ice mound at Patsio glacier. A

rock formation between present terminus and dead ice mound can be

clearly seen in Figure 7.

 

 

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CURRENT SCIENCE, VOL. 92, NO. 1, 10 JANUARY 2007 73

 

 

covered by debris. Numerous geomorphologic features

can be used to identify the terminus. Many a times morainedammed

lakes are formed downstream of the glacial terminus

(Figure 4). These lakes can be easily identified on

satellite images (Figure 5). Sometimes a glacial terminus

is characterized by a steep ice wall. Depending upon relative

positions of the sun and the wall, it can form shadow

in downstream, which can be used as a marker for terminus

delineation.

Field investigations at the Chhota Shigri glacier were

carried out in 1988 and 2003. These suggest a retreat of

800 m between 1988 and 2003. Field photographs of glacier

terminus region indicate changes in glacial morphology

(Figure 6). In the photograph of 1988 (Figure 6), the glacial

terminus can be seen clearly; by the year 2003, the entire

region is covered by debris, suggesting glacial retreat and

reduction in debris-carrying capacity of the glacier24. If

this process continues, this glacier will convert into a rock

glacier. Field investigation at Patsio glacier has shown

concave shape of terminus, indicating a retreating glacier

(Figure 7). This was further confirmed, as isolated dead

ice mounds were observed downstream the present terminus

(Figure 8), suggesting rapid glacial retreat.

Areal extent of 466 glaciers was estimated. It was

2077 sq. km in 1962 and 1628 km2 in 2001–04, an overall

21% deglaciation. Basin-wise loss in glacier area is given

in Table 3. Amount of retreat varies from glacier to glacier

and from basin to basin, depending on parameters such as

maximum thickness, mass balance and rate of melting at

the terminus14. Loss in glaciated area depends on areal extent

of the glaciers (Table 4). This is possibly because glacier

 

 

Table 4. Changes in areal extent of glaciers in Chenab basin

Glacier area Number of glaciers Glacier area Change

(sq. km2) in 1962 (sq. km) (%)

< 1 127 68 42 38

1–5 159 382 269 29

5–10 48 329 240 27

> 10 25 635 559 12

Total 359 1414 1110 21

 

 

Figure 9. Number of glaciers as a function of area for Chenab basin.

Areal extent in bin is increasing by a power of 2.

 

 

response time is directly proportional to thickness25. Thickness

is directly proportional to its areal extent22. Response

time is defined as the amount of time taken by the glacier

to adjust to a change in its mass balance. If maximum

thickness of glaciers varies between 150 and 300 m, then

the response time for temperate glaciers will be between

15 to 60 years26. In the Himalayas, if glaciers are not

heavily covered by debris, areal extent of glaciers is less

than 1 sq. km and rate of melting around the snout is around

6 ma–1; then response time is estimated to be between 4 and

11 years. Therefore, if other parameters are constant, then

small glaciers are expected to adjust to climate change

faster. This phenomenon is now being observed in the

Himalayan region, as glaciers smaller than 1 sq. km have

deglaciated by almost 38% between 1962 and 2001–04

(Table 3). On the other hand, larger glaciers have shown

only 12% loss in their area. Even though total glacial extent

is reduced, the number of glaciers has increased. The

number of glaciers as a function of area for Chenab basin

is plotted in Figure 9. Mean of glacial extent was reduced

from 1.4 to 0.32 sq. km between 1962 and 2001. In addition,

the number of glaciers with higher areal extent has

reduced and the number of glaciers with lower areal extent

has increased between 1962 and 2001. This glacial fragmentation

can be clearly seen on satellite images (Figure 10).

 

 

Conclusion

 

 

This investigation was carried out for 466 glaciers in the

highly glaciered Himalayan basins, namely Baspa, Parbati

and Chenab. Normally in the Himalayas, retreat is measured

at well-developed and easily accessible valley glaciers.

This study is now extended to small mountain glaciers

 

 

Figure 10. Resourcesat imagery of LISS-IV sensor dated 12 September

2004 of glacier number 52E09027. This glacier split into four glaciers

between 1962 and 2004. However, areal extent is reduced from

7.0 to 5.3 sq. km.

 

 

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CURRENT SCIENCE, VOL. 92, NO. 1, 10 JANUARY 74 2007

 

 

and ice fields. The investigation has shown overall 21%

reduction in glacial area from the middle of the last century.

Mean area of glacial extent was reduced from 1.4 to 0.32 sq.

km between 1962 and 2001. In addition, the number of

glaciers has increased between 1962 and 2001; however,

total areal extent has reduced. The number of glaciers has

increased due to fragmentation. Numerous investigations

in the past have suggested that glaciers are retreating as a

response to global warming. As the glaciers are retreating,

it was expected that tributary glaciers will detach from

the main glacial body and glaciologically they will form

independent glaciers. Systematic and meticulous glacial

inventory of 1962 and 2001 have now clearly demonstrated

that extent of fragmentation is much higher than realized

earlier. This is likely to have a profound influence on sustainability

of Himalayan glaciers.

This can be clearly seen, as a large difference in deglaciation

was observed between large and small glaciers.

Loss in glaciated area for large glaciers was 12% compared

to 38% for small glaciers. This can be explained by

considering three fundamental glacial parameters, namely

depth, mass balance and rate of melting at the terminus.

Glacial depth is normally related to its areal extent and

small glaciers have relatively lesser depth. Since glacier

response time is directly proportional to its depth, it could

vary between 4 and 60 years, depending upon glacial size.

This could be the fundamental reason for large retreat of

small glaciers. Therefore, small glaciers are considered as

more sensitive to global warming. This process could have

been further accelerated as small glaciers and ice fields

are situated on small mountain plateaus or on gentle mountain

slopes. On the other hand valley glaciers are usually located

in mountain valleys, surrounded by steep mountain cliffs.

This can cause further accumulation of debris and less solar

radiation will be received on the glacial surface, affecting

glacial retreat. The observations made in this investigation

suggest that small glaciers and ice fields are significantly

affected due to global warming from the middle of

the last century. In addition, larger glaciers are being

fragmented into smaller glaciers. In future, if additional

global warming takes place, the processes of glacial

fragmentation and retreat will increase, which will have a

profound effect on availability of water resources in the

Himalayan region.

 

 

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ACKNOWLEDGEMENT. We thank Drs Shailesh R. Nayak and T. J.

Majumdar for suggestions and comments to improve the manuscript.

Received 11 March 2006; revised accepted 23 August 2006