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Asian Journal of Water, Environment and Pollution, Vol. 1, No. 1 & 2, pp. 109-118.
Morpho-metric Characteristics of Glaciers
in the Indian Himalayas
Sarfaraz Ahmad, Syed I. Hasnain1 and M. Tamil Selvan1
High Altitude Environment Group
Department of Geology
Aligarh Muslim University, Aligarh (UP) India
* [email protected] Research Group
School of Environmental Sciences
Jawaharlal Nehru University, New Delhi
Received January 24, 2004; revised and accepted May 15, 2004
Abstract: Statistical analyses of the glacio-morpho metric parameters show a spatial variation across Himalaya.Glacier density varies across Himalaya: it is maximum in the Sutlej and Tista basin and moderate in the Jhelum andBhagirathi basin, while least density area is in Arunachal Pradesh basin. Most of the glaciers are simple type whilesome glaciers are big in size and composite in nature. The single biggest glacier contributes about 30% of the totalglacier cover in the respective basins. Length and width change from west to east and consequently the elongation,relief ratio and relief area gradient. These indices suggest that the west glaciers are stream type, while easternglaciers are patch type and occupied in high relief region.
Health of glaciers can be inferred using Accumulation Area Ratio (AAR) and the average AAR value of theIndian glaciers is 0.48; a state of negative mass balance. A comparative analysis of glaciers� AAR shows that theglaciers having zero AAR constitute about 34% of total glaciers, while glaciers having near 100 AAR constituteabout 9% of total number of the glaciers. Correlation matrix between various glacio-morpho metric parameterssuggests that the AAR is closely related to accumulation area, length, mean elevation and area.
The accumulation zone is gentler slope area of the glaciers and a slight shift in zero isotherms on the accumulationsurface will result in quick shrinkage in accumulation area. It will further contribute to more negative mass balanceand development of supraglacial and moraine dammed lake in glaciated region. Present study clearly indicates thehigh susceptibility of the glacier shrinking in Indian Himalaya in the present climatic change regime.
Key words: Spatial variation, Himalayan glacier, morphometry and climate change.
Introduction
Himalayan glaciers are situated in the Tropical climatebelt and they are spread between 36° N and 27° N. Thismountain belt is near Tropic of Cancer and receives moreheat than by Arctic and temperate climatic mountain belts.Therefore, Himalayan glaciers are more sensitive toclimate change than other mountain glaciers in the world(Hastenrath, 1984, 1995; Thompson et al., 1995; Kaser,1996, 1999; Wagnon, 1999; Hasnain et al., 1999).Glaciers� existence in these Himalayan Mountain is due
to high altitude and local/regional climatic conditions.Large variation in Himalayan terrain and climatic regimeresulted into variable glacier responses under climatechange. It is due to its large expanse�covering widelatitude and longitude�and operation of the twoindependent regional climate regimes, Indian Monsoonand Westerly, which control the hydro-meteorology ofthe region (Mani, 1981). These two climatic regimescontribute the precipitation to glaciations in HimalayanMountain. Benn and Owen (1998) emphasized to testthe relative importance of the Indian Monsoon and
110 Sarfaraz Ahmad et al.
features across Himalaya. Morpho-metric studies ofglaciers were initiated long back and Doornkamp andKing (1971) introduced some morpho-metric parametersfor the glacial landforms. Naithani et al. (2001) andPrasad and Naithani (2003) proposed some morpho-metric parameters related to Gangotri glacier recession.Statistics of these parameters and their spatial changeacross Himalaya can give understanding of the impactof change in regional climate scale and its impact onglaciations. In present paper, morpho-metric charactersof the Himalayan glaciers and susceptibility of de-glaciations processes under present climate changescenario are discussed.
Present Glacier Cover in Indian Himalaya
Glaciations in Himalaya is developed all across lengthand controlled by mountain height which exceeds thenecessary height for generations of glacier. Therefore,glaciations occur around the various peaks and massif:Nanaga Parbat, Nun Kun-BaraShigri (western Himalaya),Gangotri-Chaukhamba peaks, Kamet group, Nanda devi(central Himalaya), Kanchanjunaga, Everest Makalugroup, Kulu Kangri range, and Namche Barwa (easternHimalaya). Arial distribution of these permanent ice andsnow covers in these peaks and massifs of Himalaya iscompiled from various maps (Fujii & Watanabe, 1983)in Table 1. However, the accuracy of estimated area is
Table 1: Perennial ice cover in the Himalaya
Major River Mountain Glacier %
River System Area (km2) Area (km2) Glaciation
Indus System Indus 268842 7890 3.3
Jhelum 33670 170 5
Chenab 27195 2944 10
Ravi 8092 206 2.5
Sutlej 47915 1295 2.7
Beas 12504 638 4.4
Ganga System Jamuna 11655 125 1.1
Ganga 23051 2312 10
Ramganga 6734 3 0.04
Kali 16317 997 6.01
Karnali 53354 1543 2.9
Gandak 37814 1845 4.9
Kosi 61901 1281 2.1
Brahmaputra System Tista 12432 495 4
Raikad 26418 195 0.7
Manas 31080 528 1.7
Subansiri 81130 725 4
Brahmaputra 256928 108 0.4
Dibang 12950 90 0.7
Luhit 20720 425 2
midland westerly in providing moisture and controllingglaciations and hydrology in the region. This diversityresulted in varied deglaciation susceptibility under givenclimate perturbations. Therefore, proposed relativeglacio-chronologies are much uncertain concerningthe timing and extent of glaciations history in theHimalaya (Owen et al., 1998). The analysis of recentglacial advances periods from the different places alongHimalaya suggests the change in the southwest monsoonsystem which combined with cooling associate resultsin glacier advance broadly at same time (Owen et al.,2003). Therefore, elucidating the relative importance ofregional climate is essential for predicting the futureresponse of glaciations in Himalaya under present climatechange.
Present day glaciations in Himalaya bear a strongregional climate control and any change in global climateregime will impact on large scale. Therefore, it isimportant to understand the coupling between regionalclimate events and global circulation model, because itcan yield information on how the climate system worksat regional scale. In addition, the effects of climate changeon human population are related to regional climateevents, not the average global climate change. Thevariation in glaciations characteristic across the Himalayais a result of terrain, regional climate, and latitudinal andlongitudinal variation. It resulted into development ofparticular characteristics for glaciers morpho-metric
Morpho-metric Characteristics of Glaciers in the Indian Himalayas 111
limited, since only a few regions were covered in exactmapping. The detailed information of glaciers in Indusand Ganga/Brahamputra river basins are now availablein the report published by Geological Survey of India(Kaul, 1995). In the Indus basin, total number of glaciersis 3755 covering an area of 33,896 km2, distributed inJhelum, Sutlej and others. Total number of glaciers inGanga and Brahamputra basins is 1488 covering 4062km2 distributed in Bhagirathi, Alaknanda, Tista andArunachal Pradesh (a part of Brahmaputra basin).
Methodology
A basic quantitative measurement of the glaciers used inthis paper is made from the Himalayan glacier inventorypublished by Geological Survey of India in 1995. Theseglaciers are distributed in various basins across Himalaya.In this inventory, morpho-metric parameters are givenfor 1105 glaciers in Indian Himalaya and represent 12%of the total glaciers in Indian Himalaya. Among theseglaciers, 357 belong to Indus basin and 748 glaciers inthe Ganga/Brahamputra basins. They are distributed inJhelum basin (western Himalaya), Sutlej and Bhagirathibasin (central Himalaya), Tista and Arunachal Pradesh(eastern Himalaya) (Figure 1). The various quantitativeparameters are derived using the UNESCO Manual(1970): �Perennial ice and snow masses, Technical papersin Hydrology, No. 1�. The compilation was refined
through the instruction issued by the TemporaryTechnical Secretariats (TTS) for world Glacier Inventoryand contained in Muller et al. (1977) and its supplements(Muller, 1978).
Result and Discussion
Present day Himalayan glaciers cover approximately30,000 sq. km, which is about 17% of the Himalayanmountain area. In comparison to Himalaya, Alps has only2.2% of the glacier cover. Himalaya has about 32 timesmore area under glacier coverage (Weismen, 1959) andglacier density vary from western to eastern Himalaya.Glacier density is a measure of the glaciations intensityplotted in Figure 2. The result indicates the maximumdensity in central Himalaya (Sutlej, Bhagirathi and Tistabasin). It is perhaps as a result of the heavy precipitationin monsoon and low atmospheric temperature duringwinter precipitation. Glacier density and average glacierarea do not coincide and average maximum glacier areais in the Bhagirathi, while density is maximum in theSutlej basin. However, glacier area situated in the Jhelumis smallest, which coincide with moderate glacier density.In comparison to average glacier size the glacier densityhas more importance as large area is under glacier activityand provides a higher potential for utilization of glaciermeltwater, the greater the influence on local climate, thegreater is the problem caused by glacier floods and debris
Figure 1: Distribution of permanent snow cover across Himalayan axis.
112 Sarfaraz Ahmad et al.
flows. With increasing glacier density, the importanceof glacier human activities increase in significance(Zongtai & Huian, 1992). Average sizes of IndianHimalayan glaciers are 0.71, 2.6, 1.6 and 1.5 km2 withstandard deviation of 1.23, 8.54, 3.66 and 1.5 in theJhelum, Sutlej�Bhagirathi basins, Tista and ArunachalPradesh basins in Himalaya respectively.
Higher standard deviation values for the glaciers� sizein various regions indicate an asymmetrical distribution.The frequency distribution and skewness analysis suggestthat the glacier distribution is similar in the Jhelum,Tista and Arunachal basins. However the skewnessof the glacier distribution in the Bhagirathi and Sutlejbasins is quite different. It may be related with terrain
Figure 2: Glacier density in various basins across
the Indian Himalayan territory.
characteristics as shown in elevation profile in variousbasins in Himalaya (Figure 3). Across the Himalayanmountain belt the cross section profiles in the Jhelum,Tista and Arunachal Pradesh region show a similarity,while the cross section in Bhagirathi basin is different. Itresulted in development of different type of glacierdistribution in the region. The variable terrain andregional climatic characteristics in Himalaya lead todevelopment of various types of glaciers. In the Jhelumbasin all types of glaciers are well distributed, while inthe Sutlej basin compound glaciers are common and smallglaciers and snowfields are less important. In theBhagirathi basin, big valley glaciers are few andnumerous small and simple glaciers are common.However, compound glaciers and snowfields are commonin eastern Himalaya, while simple glaciers are lesscommon (Figure 4).
Largest glacier in the glaciated region is an importantcharacteristic of the Himalayan glacier basin. Itconstitutes about 40% of the total glacier cover in theirrespective basins (Figure 5). Minimum cover is beingrepresented by single biggest glacier in the Jhelum basinand maximum cover is represented by biggest glaciersin Bhagirathi and Bhilganga basins. Even, the biggestglacier in eastern Himalaya also constitutes about 22%of the total glacier cover in Tista and Arunachal Pradeshbasin. Biggest glaciers are composite type glacier, andnumber of the tributaries contribute to the main trunk
Figure 3: Elevational cross-section profiles across various basins in the Himalaya.
Morpho-metric Characteristics of Glaciers in the Indian Himalayas 113
recession data compiled by GSI show that 24 % of theglaciers are in state of marked recession, while 34%glaciers show recession and only 3% show minor relativeadvances. Glaciers showing relative advances are situatedmainly in the high precipitation zone and Northern slopeof Himalayan axis (Hewitt, 1998; Ageta, 1997). Theretreats of snout of the glaciers are related to mass balanceof the glacier in last few decades (Meir, 1965). Collectingthe mass balance data over such remote glaciers isdifficult (Osterm & Brugman, 1991). In absence ofground measured mass balance data, the easier obtaineddata such as AAR, glacier retreat/advance rate can beused as a proxy for mass balance data of the glacier.Therefore, health of glaciers can also be evaluated onproxy basis from the AAR value of the glacier. AverageAAR of the Indian glacier is 0.48, which indicates glaciersare under negative mass balance. AAR value for the zeromass balance represented by Himalayan glacier is about0.65 (Ageta, 1996; Dhobal, per.). Data analysis showsthat the AAR of 34% glaciers are near zero. It indicatesthat the whole area of these glaciers is contributing toablation and glaciers are reeling under intense meltingstage. While, some glaciers and snow/ice patches haveAAR values about 100 suggesting no ablation at surfaceof these glaciers. These glaciers contribute only 2% ofthe glaciers in the present database. A comparativeanalysis shows that 400 sq km area of snow and ice bodieshaving AAR near zero melts throughout summer season.However, the snow/ice having AAR near hundredcontributes about 97 sq km area.
The spatial distribution of glaciers having AAR zeroand 100 shows that the Jhelum basin holds few glaciershaving AAR near zero, and not a single glacier has AARnear 100 (Figure 6). Moreover, the glaciers in Sutlej andBhagirathi basins possess maximum number of glaciershaving AAR near zero, while some glaciers have AAR
near 100. Glaciers in the Tista and Arunachal Pradesh
Figure 4: Distribution patterns of various type
of glaciers in different basins.
Figure 5: Glacier cover contributed by the single biggest glacier in the basin distributed
in different parts of the Himalaya.
glaciers. Monitoring of big glaciers show cumulativeimpact of its tributary glaciers. Hence, response of thesebig glaciers towards climate change is complex andcumulative. The snout retreats/advances of these bigglaciers show cumulative response of various glaciers inthe basin under change in climatic conditions.
Studies conducted by Prasad and Naithani (2003) andAhmad and Rais (1999) showed that the various tributaryglaciers of main single big glacier behave according toglacier slope, sun zenith, and local wind pattern, whichbrought snow on glacier surface. Available glacier
114 Sarfaraz Ahmad et al.
basins having AAR near hundred are in good numberthan near zero. Minimum and maximum altitudecharacteristics of the glaciers cirque having AAR nearzero and hundred were analyzed. The results show thatthe average lowest and highest altitude of the glacierscirques having AAR near zero is 4666 and 5187 amsl,while these altitude for the glaciers cirque having AARnear hundred is 5180 and 5817 amsl. It suggests that thesmall glacier bodies within lower altitude mountain rangeare under intense melting stages, while the glacier patchesin the higher altitude range are least sensitive to melting.AAR of the glaciers in Himalaya clearly indicates themeltdown state of glaciers. It is reflected in terms ofshrinkage of the glacier area and recession of the glaciersnout elevation. Studies conducted by Hasnain et al.(2003) showed that the area of main Gangotri glacierand Chhota Shigri glacier in Garhwal and HimachalHimalaya have shrinked about 11-12 % in last 15 years.The study conducted by Kulkarni et al. (2003) also hasshowed that the glaciers cover in the Baspa basin inHimachal Himalaya has been lost about 20% in last 40years.
Impact of glacier ice mass loss due to high rate of icemelting is chiefly marked in the snout and lateral partof the glacier. These lowest positions of glaciers aregood indicators for assessing the impact of regionalclimatology, longitude and latitude on glaciations. Ingeneral, the elevation of glaciers� snout is minimum inwestern Himalaya and altitude increases from westernto central and further increases in eastern India Himalaya(Figure 6). In the Jhelum basin in western Himalaya, thesnouts terminate at lowest elevation, because theseglaciers receive moisture from winter air masses. Thejump of termination level to higher level in Sutlej andBhagirathi valley glaciers is related to monsoon regime,because zero isotherms in monsoon are possible only athigher altitudes. However, there is not much variationfrom central Himalaya in Sutlej and Bhagirathi basinsand Tista and Arunachal basins in eastern Himalayas.
Figure 6: Spatial distribution of the glacier having AAR
near zero and hundred across Indian Himalaya.
However, in some places snouts of the glaciers aresignificantly elevated. It is related to some regionalclimatic characteristics i.e., rain-shadow region, particularwind direction, and moisture laden stream.
Terminus altitudes of the glaciers are determined bythe lower limit of regional firn line where the averagetemperature is near 0° C or melting point. At this altitudeand location, repeated melting and thawing processes actall the time (Flint, 1957; Cotton, 1942) and form the smallglacier cirque while further coalescing processes lead tocomposite glacier basins. The lowest and highest altitudesof cirques are characteristics of nivation processes limit.In any mountain range, the cirque is fixed within range.However, the height of cirque backwall depends on heightof the range. On the slope of higher ranges, the backwallrises to higher level than on lower ranges. In most ofglaciated region of the world, generally the cirquebackwall rise upto 600-700 m above cirque floor. InHimalaya these backwall very often rises to 2460 amsl.It can be argued that because Himalayan peaks are higherthan many peaks of the world, cirque also have higherbackwall (Ahmad & Rais, 1999). The spatial distribu-tion for relief of the cirque shows an increasing trendfrom the western to eastern Himalaya (Figure 7).
Figure 7: Spatial variations of relief of the various
glaciers across the Himalaya.
However, standard deviation for the terminus altitudeincreases from western to central part and again decreasesin the eastern Himalaya. This is related to climatic controlover the terminus altitude in the eastern Himalaya.
Terminus altitude of the glacier basin is also influencedby relief of the glacier body. Higher the relief subse-quently more accumulation of snow and ice which resultin to force down the terminus at lower height. Scatterplots between relief of the glacier body and terminusaltitude of the glaciers in different parts of the Himalayaare analyzed. The results show a negative relationshipbetween relief and terminus altitude with varying degreeof correlation coefficient in different parts of the
Morpho-metric Characteristics of Glaciers in the Indian Himalayas 115
Himalaya. This relationship shows a lesser degree ofcorrelation coefficient with lesser slope in westernHimalaya, while higher negative slope with high degreeof correlation coefficient in the central Himalaya.However, in the eastern Himalaya, this relationship againshows lower degree of correlation coefficient along withlesser negative slope (Figure 8). It suggests that the relief
highest concentration of moraine and ice dammedlakes in eastern Nepal and Bhutan (ICIMOD, 2001).Accumulation/ablation slope is minimum in theBhagirathi basin which also indicates a higher slope inablation region and possibly at Gangotri glacier it hasaccelerated the glacier recession (Prasad & Naithani,2003).
Mountain glaciers are thin ice streams flowing fromhigher to lower altitude. 94% of the Himalayan glacierlength varies between 1 km and 2 km. Average length ofthe Indian Himalayan glacier is about 2.6 km anddecreases from western to eastern Himalaya. Glacierwidth increases from western and eastern Himalaya. Theaccumulation/ablation length ratio for the various glaciersacross the Himalaya are plotted (Figure 10). It shows the
Figure 8: Scatter plots between relief and the terminus
altitude in various parts of the Himalaya.
of the cirque does not affect the terminus in easternHimalaya. Hence, in this part of Himalaya, the terminusesaltitudes are probably controlled by climatic regime ratherthan mass of the glacier. Moreover, the relief plays animportant role in determining the terminus altitude incentral Himalaya.
Slopes of the ablation and accumulation areas play animportant role to determine snout retreat rate. The slopeanalyses of the ablation and accumulation area suggestthat the average accumulation surfaces are gentler slopesthan the ablation slopes. These slopes are important inassessing the change of climate; a slight increase in airtemperature will result in shifting of the zero isothermtowards the higher altitude and will impact on large areaof the accumulative area. It will further contribute to themore negative mass balance. A ratio between accumula-tion slope/ablation surface slopes shows a distinct patternacross Himalaya (Figure 9). It is moderate in the westernHimalaya and highest in eastern Himalaya, while ratio isequal in Tista basin. Lesser slopes of ablation region ofglaciers in the eastern Himalaya provide opportunity fordevelopment of supra glacier lakes. It is witnessed by
Figure 9: Accumulation and ablation of slope ratio
of the various glaciers in different
basins across Himalaya.
Figure 10: Accumulation and ablation length
ratio across Himalaya.
same pattern as that observed for accumulation andablation slope ratio. Perhaps the proportion of accumula-tion and ablation length is related to proportioning ofsummer, winter temperature, and monsoon, westerlyprecipitation in the region. In the western Himalaya,lower summer temperature subsequently lower snow/icemelting and snow deposition by westerly in wintercontribute to net mass balance. Therefore only smallaccumulation length of glacier is enough for zero mass
116 Sarfaraz Ahmad et al.
balance. However, in Arunachal Himalaya, high summertemperature and consequently higher ice/snow meltingand snow inputs by monsoonal trajectories contribute toglacier mass balance. Higher snow and ice melting andsnow input in the monsoon months require largeaccumulation area for zero mass balance. This hypothesisis tested on field-based glaciological observations carriedby various workers. The studies carried out by Kulkarni(1992) in the Kashmir Himalaya showed that AARfor the zero mass balance is 0.44. Moreover AARvalue is calculated (0.55-0.55) for Himachal Himalaya(Mukherjee & Sangewar, 1995; Dhobal, 1992). Furtherin east of Himachal, the AAR is calculated about 0.66-0.68 for zero mass balance for the Dokriani glacier inGarhwal Himalaya. Dokriani glacier is in typicalmonsoon environment and average monsoon rainfall inthe region is about 800 mm (Hasnain, 1999).
Shapes of glaciers across the Himalaya are analyzedusing the L/W (elongation) and L/H (relief ratio) andH/A (relief area gradient) indexes. In general, L/Wdecreases from western to eastern Himalaya, while L/Hincreases from western to eastern Himalaya (Figure 11).These indexes depict that the glacier shape in westernand eastern Himalaya is quite different. In the western
Himalaya, the glaciers are long stream type, while theglaciers in eastern Himalaya are short and situated in highrelief basin. Reliefs of the glaciers across the Himalayashow an increase from western to eastern Himalaya. Thehigher relief in eastern Himalaya is due to higher regionalsnowline which contributes to nivation processes anddetermine the relief. Higher relief in eastern Himalayaresults higher snow avalanches activity which providesa large part of snow accumulation to glacier mass balance(Inoue, 1977). It provides the sufficient snow and iceaccumulation for surviving the glaciers in easternHimalaya.
Moreover, H/A is an ariel distribution of the glaciersurface in different altitude band. It is an importantmorpho-metric feature of the glacier to assess the impactof climate change on glacier mass balance. Higher reliefarea gradient indicates lesser aerial coverage in particularaltitude elevation band. Therefore, a slight shift in thezero isotherms will impact on small incremental in arielcoverage under warming conditions. The relief areagradients of various glaciers across Himalaya are shownin Figure 11. It shows an increase from western to easternHimalaya. The favourable morpho-metric condition forsurviving the glaciations for a glacier is higher relief areagradient and low elongation. The elongation index of theglaciers give some understanding about energy interac-tion in glaciated basin. Elongated body is more influencedby surrounding reflected diffuse energy and vice versa.Based on this assumption the survival index is computedby formula (Relief area gradient/elongation). Spatialdistributions of this index show increasing trend towardseastern Himalaya. Higher value of survival index in theeastern region shows the higher chances for survival ofglaciers and even the less winter snow precipitation inthe region (Figure 12).
Figure 11: Elongation index (L/W), relief ratio (L/H)
and relief area gradient H/A of the various glaciers
in different parts of the Himalaya.
Figure 12: Survival index of various glaciers
across Himalaya.
Morpho-metric Characteristics of Glaciers in the Indian Himalayas 117
Spatial variation in relief area gradient for the various
glaciers across Himalaya suggests that the glaciers
situated in 79° and 30° have highest values corresponding
to Gangotri region in Bhagirathi basin. The surviving
index in various glaciated basins across Himalaya also
indicates the highest survival index values for glaciers
in Ganga headwater. It is perhaps related to terrain
characteristics as in other basins. The relief of the higher
altitude is flat top in Jhelum, Tista and Arunachal.
However in the Ganga headwater, sharp increase in relief
at high altitude results in development of huge debris
cover on glacier ablation region which further protect
the glacier from high melting. Therefore, these glaciers
in Ganga headwater area probably show the slowest
response of climate change.
Conclusions
The glacio-morphometric parameters of the 1200 glaciers
across the Himalaya are analyzed and following salient
features are observed. The glacier density across
Himalaya is maximum in the Sutlej and Bhagirathi basins
and moderate in Jhelum basin. The distribution of glaciers
type is quite different in Bhagirathi basin probably related
to terrain characteristics. The elongation and relief ratio
index indicate that the glaciers in western Himalaya are
long stream type and glaciers in eastern region are small
patches in high relief basin. A ratio of the accumulation/
ablation surface slopes and length show a distinct pattern
across Himalaya. It is moderate in the western and highest
in eastern Himalaya and determine the impact of climate
change on glacier.
The average AAR of glacier is 0.48, which indicates
glaciers are under negative mass balance, 34% of glaciers
in dataset have AAR near zero, while only 2% of glaciers
and snow/ice patches have AAR near 100. Spatial
distributions of survival index computed based on relief
area gradient and elongation index suggest the least
climate sensitivity of the glaciers situated in the
Bhagirathi basin in Ganga headwater.
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