Climate change and its impact on the Himalayan glaciers a case study on the Chorabari glacier, Garhwal Himalaya, India

Climate change and its impact on the Himalayan glaciers a case study on the Chorabari glacier, Garhwal Himalaya, India Ravinder Kumar Chaujar Wadia Institute of Himalayan Geology, Dehra Dun 248 001, India Glaciers and small ice caps in temperate environments are sensitive indicators of the change in climate. Mountain glaciers provide a valuable tool for reconstruction of Holocene climate changes. The present work, thus, deals mainly with climatic change and its impact on the Himalayan glaciers based on the dating of lichens, developed on loops of moraines formed due to various stages of advance and retreat of the glacier. Here it has been shown that the date of the largest lichen on the loop of moraine that indicates the position of maximum advance of the glacier is 258 years. It shows the period when the Chorabari glacier started receding from the point of its maximum advancement in this part of the Himalaya. Earlier work in the Dokriani Bamak (glacier) has shown that the period of retreat in the respective part of the Himalaya is around 314 years. Research on various glaciers of the northern and southern hemisphere has shown that most of them started their retreat in the mid-eighteenth century, thereby indicating the end of the Little Ice Age maximum. These results suggest that climatic changes in the world started during early to mid-eighteenth century, though this needs further work for confirmation. There is every possibility that its effect was sensed first in the zone close to the equator by the northfacing Himalayan glaciers such as the Dokriani Bamak. Keywords: Climate change, geomorphology, glaciers, lichenometry, Little Ice Age. IT is now a well-established fact that the glaciers are receding by and large worldwide. Warmer climate in the future may cause increased melting of glaciers, which will lead to a rise in sea level. Change in climatic trends is clearly reflected in mass and temperature changes of glaciers and permafrost. The present study deals mainly with climatic change and its impact on the Himalayan glaciers based on the study of landforms by the Chorabari glacier in the Kedarnath temple area, Garhwal Himalaya, and dating of various cycles of its advance and retreat by lichenometry. The area is located (Figure 1) between lat. 30 44 50 N and 30 45 30 N, and long. 79 1 16 E and 79 5 20 E. The basin area of the glacier is about 38 km 2, whereas the area covered by the glacier is 15 km 2. It is e-mail: rchaujar@gmail.com also fed by several hanging glaciers. The length of the glacier is about 6 km. Chorabari is a valley glacier which has two snouts, one in its left margin and other in the right margin (Figure 2). The right snout, which is presently the main supplier of water to the Mandakini River, is situated at an altitude of 3865 m asl and the left snout is at an altitude of 3835 m asl. In other words, the origin of the Mandakini is mainly from the right snout of the glacier. Melt-out water from the left snout also feeds the water of the Mandakini and merges with the main channel, which is about 100 m northwest of the Kedarnath temple. It appears that this is part of a single glacier has been divided into two and separated by its medial moraine before receding to the present position (Figure 2). Originally there was only one glacier when it was in its advancing stage. Receding in due course of time has melted the glacier to such an extent that it could not disturb its own medial moraine and has been divided into two parts, thus forming the two Chorabari snouts. The left snout is in a stage of thinning faster than the right one. In the active zone, the main medial moraine now plays a major role in the glacier activities. It acts as the left lateral moraine of the main glacier and right lateral moraine of the tributary glacier, though the tributary glacier has a common accumulation zone as that of the main glacier (Figure 2). This suggests that the glacier has undergone vast amount of receding due to which its own medial moraine has separated its tributary glacier from the main glacier. There was a re-advancement of the glacier before the final stage of retreat, which was indicated by the presence of a new lateral moraine (the present one) near the snout, within the earlier lateral moraine. This advancement was smaller in size compared to the earlier glacier before retreat. In order to study different cycles of advance and retreat of the Chorabari glacier, various loops of lateral and terminal moraines have been studied in its inactive zone (i.e. the zone which is no longer in contact with the glacier). A series of four well-defined lateral (Figure 3) and terminal moraine loops (L1 to L4) are noticed at a height of 3160, 3320, 3440 and 3640 m asl respectively, which have been used as the basis for reconstructing the glacier history in defining the sequence of glacier episodes before its complete deglaciation from the inactive zone. The moving ice body, which formed the stage II landforms, did not have the energy to destroy the existing larger landforms of stage I deposited in the enhanced activity during Little Ice Age, but it could only modify its lateral and ground moraines. This suggests that the glacier energy associated with the formation of smaller superimposed landforms of later stage is of lower order and is insufficient to significantly alter the pre-existing landforms. In the similar manner, stages III and IV performed action in the respective area. These loops suggest that after their development, no major movement/advance/ CURRENT SCIENCE, VOL. 96, NO. 5, 10 MARCH 2009 703

Figure 1. Location map of the study area. Figure 2. Panoramic view of the Chorabari glacier. A, Accumulation zone; RS, Right snout; LS, Left snout; M, Medial moraine, and T, Kedarnath temple. activity of the glacier took place in the region. Otherwise more loops would have been found in this zone. The four stages of advance and retreat have been dated with the help of lichenometric study. The moraines were dated by lichenometric studies following the method described in the literature 1 8. It depends on the assumption that if colonization delay (time taken by the lichen to grow on a surface after its exposure to the atmosphere) and growth rate of lichens are known in a particular area, then a minimum date can be obtained by measuring maximum diameter of the largest lichen at the site. This method is useful in regions of glacial environment which are mostly above and beyond the tree line, where lichens grow slowly and have great longevity. In such conditions, it is possible to date deposits up to thousand years; but in most of the cases, this method is useful for dating deposits just up to 500 years. 704 Figure 3. Area vacated by the Chorabari glacier after receding. L1 L4 are lateral moraines forming parts of loops of stages I IV of glacial advance and retreat at a height of 3160, 3320, 3440 and 3640 m asl respectively. T represents location of the Kedarnath temple. 1 4 are locations of largest lichens of the respective loops. The most common lichen growing on the slope boulders is Rhizocarpon geographicum. It belongs to the yellow green section Rhizocarpon most frequently used in lichenometry. The longest axes of all the lichens of this species growing on the upper faces of selected boulders were measured with a flexible tape and digital caliper, with measurements estimated to the nearest 1 mm. About 2000 lichens in the region were measured on different moraines and their frequency distribution was plotted (Figure 4) to display relative age structure of the population. Size increment of 4 mm was established, since an increment that is too small produces multiple low and irregular frequencies, while information is lost if incre- CURRENT SCIENCE, VOL. 96, NO. 5, 10 MARCH 2009

ments are too large. Seven prominent lichens on different moraines were well marked in the field for future reference. These lichens were measured again during the first week of November 2004 07 and a growth of 1 mm was found from their calibration curves (Figure 5). Thus, a growth rate of 1 mm per year was established in the area. Most historical monuments that have been dated do not have any lichen growth over them. In such cases, only an indirect method can be used to find the value of colonization delay. After enquiring with local people and authorities, a bridge close to the Kedarnath temple was found to be around 85 years old. The bridge and its surrounding walls do not have any lichen growth over them. If we take the age of the bridge as 85 yrs (approximate), then we can presume the colonization delay to be 85 yrs (minimum). Considering these values of colonization delay and growth rate, the dates of lichens on various glacial boulders of different loops have been calculated. Largest lichens on the boulders of moraines of loops in the four stages of advance and retreat of the glacier are 173, 155, 94 and 52 mm on moraines of stages I IV respectively. Using the above values of colonization delay and growth rate, the ages of these lichens are shown in Table 1. Figure 4. Frequency distribution of lichens in different zones of moraines. Size range is 4 mm, i.e. 0 4, 5 8, and so on. These dates further suggest that climatic changes in this part of the world started nearly 258 years ago, since the retreat of the glacier is associated with global warming. It contradicts the statement by Raina 9 that Glaciers have been retreating in the Himalaya since Last Glacial Maxima (LGM) at 18 to 20,000 years ago. History mentions that the Kedarnath temple of Lord Shiva was constructed by five brothers known as the Pandavas 10. The temple is strong, made up of thick granites and high-grade metamorphic gneissic rock slabs, pillars and bricks. The walls and pillars are about 1 m thick. Siddharth 11, in his studies on the basis of astronomical and literary references supported by archaeological evidences concluded, Events described in the great epic of Mahabharata could have occurred around 1350 BC in the region of latitude of 35 degrees stretching right across Turkey and western Iran through southern Turkmenistan, Afghanistan, and Kashmir to Indus valley. Marine excavations by Rao 12 confirmed the existence of the city of Dwarka dating back to around 1700 BC. Interestingly, these excavations revealed links with some of the above-mentioned places. Recently, Rao has mentioned about the possibility of a tsunami drowning the ancient city of Dwarka in 1500 BC after striking the coast of Gujarat. Kochhar 13 dated the war of Mahabharatha back to around 1000 BC. Vartak 14 has derived on the basis of scientific dating, the initiation of the Mahabharat War to be 16 October 5561 BC. The Hindu Timeline 15 dates the War back to 1424 BC. The exact date of the Kedarnath temple is not mentioned in the literature. If we look at above references, a minimum age of about 3000 years can be considered for the temple. The location of temple within the receded area of the glacier suggests three possibilities: (a) There was no glacier in the region at the time of construction of the temple minimum of 3000 years ago. (b) There was a glacier but beyond the present location of the temple. (c) There was a glacier and the temple was constructed after cutting through the ice of the glacier at that particular position. Table 1. Size of largest lichen with growth rate of 1 mm per year and a colonization delay of 85 years (1 4) are their locations marked in Figure 3 Age (size/growth Stage Largest rate + colonization delay) (location) lichen (mm) (years) Figure 5. Growth curve of lichens in different zones of moraines. I (1) 173 173/1 + 85 = 258 II (2) 155 155/1 + 85 = 240 III (3) 94 94/1 + 85 = 179 IV (4) 52 52/1 + 85 = 137 CURRENT SCIENCE, VOL. 96, NO. 5, 10 MARCH 2009 705

Two wall engravings of writings/poems dated AD 650 and 850, on the back boundary wall of the temple, discuss the beauty of the Kedarnath temple (Figure 6). There is no mention about snow/ice/glaciers in them. These findings suggest that there was no glacier during that period around the temple. This confirms that there was no glacier around the temple till AD 850. The earliest evidence of glacial activity recognized by Larocque and Smith 16 in the 7th century at Tiedemann glacier, Mt Waddington area, British Columbia Coast Mountains, Canada does not hold good at least for the Himalayas. At the same time, they have mentioned that most of the Little Ice Age evidences have recorded events in the 15th to 18th centuries. However, Figure 6. Engravings of poems dated AD 850 (a) and AD 650 (b) on the boundary wall of the Kedarnath temple. Figure 7. Schematic diagram of global temperature variations since the Pleistocene on three timescales: a, the last ten thousand years; b, the last thousand years 13. 706 glacier advances in the European Alps as early as the mid-14th century are considered as the beginning of the Little Ice Age (Figure 7), and major advances took place during this period 17. According to Grove 18, the Little Ice Age is a widely used term for the period AD 1300 1900 (which is notable for worldwide glacier expansion). We consider that glaciations in the region started during the mid-14th century, i.e. the beginning of the Little Ice Age and continued till around AD 1748 (as calculated by lichenometric dating). After the peak of the Little Ice Age, recession of the glacier was followed by its three major stages of advance and retreat as indicated by the four loops of terminal and lateral moraines of the glacier. This further suggests that the temple remained submerged in ice/glacier for a minimum of 400 years. Since the temple is made up of thick, strong, rock walls and pillars, it could withstand submergence in the glacier for such a long period. The submergence of the temple is further supported by the striations found on its walls (Figure 8). Even the inner walls of the temple have been polished and striated by the glacier. The orientation of these striations is in the direction flow of the glacier; or in other words, these striations confirm the direction of flow of the glacier. These striations were formed when the glacier, during its movement, picked up sediments on its travel, either by abrasion or by plucking of the boulders/base rocks that come in its way. These sediments, being under great pressure from above due to the weight of the glacier, scratched the walls (formed by big rock bricks) of the temple by abrasion during the glacier movement. These striations are mostly multiple, parallel lines which represent movement of sediments loaded over the base of the glacier. They range from 1 to 2 mm depth, with wide markings on the walls of the temple (Figure 8). Glaciers and small ice caps in the temperate environment are sensitive indicators and react even to the slightest change in temperature. They provide reliable information on historical temperature changes. Mountain glaciers provide a valuable tool for the reconstruction of Holocene climatic changes. They give valuable information about different reactions of the glaciers to fluctuations in the climate, as these can be expected during any future climate changes as well. At present, evidence of Little Ice Age glacier fluctuations comes from Europe, primarily due to the availability of historical documents and instrumented data that last over hundred years. In other places, like the Himalayas, New Zealand, etc., the absence of historical records older than AD 1850 has led to derivation of Little Ice Age chronology by dating moraines using tree-ring records, lichenometry and Schmidt hammer measurements 19 21. Mounting evidences now suggest that the period between AD 1750 and 1800, rather than the late 19th century represented the culmination of the Little Ice Age in Iceland 22. It has been concluded that Lambatungnajokull, an CURRENT SCIENCE, VOL. 96, NO. 5, 10 MARCH 2009

outlet glacier of Vatnajokull ice cap in Iceland has responded dynamically to Late Holocene climate change 22. Focusing on the past 400 years, the glaciers grew in size between AD 1600 and 1700, as recorded in medieval documents. It probably continued during much of the 18th century. The glaciers reached the greatest Little Ice Age extent in the 18th century, probably between AD 1780 and 1795. Since then, they have undergone an overall retreat punctuated by numerous advances and retreats. McKinzey et al. 23 stated that despite the range of possible dates for the Franz Josef Glacier, New Zealand, the most cited 24 29 Little Ice Age is AD 1750. Lichenometric dating studies at the Eugenie, Hooker, Mueller and Tasman glaciers in Mt Cook National Park, South Alps, New Zealand reveal that the Little Ice Age was maximum during the mid-18th century, around AD 1725 1740 (ref. 30). The Little Ice Age maximum during the 18th century was similar in northern Norway 31,32 and southern Norway 33 35. Mathews and McCarroll 36, in their study in Breheimen, southern Norway found peak avalanche activity between AD 1685 and 1750; the same time as the outlet glaciers were expanding to reach their Little Ice Age maximum limits. This suggests the possibility of a common trend in mountain areas of both hemispheres and the Himalayas. Differences of Little Ice Age maxima of four to five decades due to regional/local/orientation (whether facing north, south, east or west) variations are still to be considered as synchronous. North-facing Dokriani glacier in the Garhwal Himalaya indicates Little Ice Age maximum during AD 1692 (ref. 37), whereas south facing Chorabari glacier shows its maximum during AD 1748. Now since Figure 8. a, Striations on the wall of the Kedarnath temple; b, Its close up view. data on the retreat of Little Ice Age glaciers of the northern and southern hemispheres and the Himalayan regions are available, it may be mentioned that the climatic changes in the world started around early to mid- 18th century, though further studies are need to confirm this. There is every possibility that the effect of climate change was sensed first in the equatorial zone by the north-facing Himalayan glaciers such as the Dokriani Bamak (glacier). The Kedarnath temple and the engravings on its boundary wall confirm that there was no glacier around the temple till AD 850. Lichenometric evidences in the Chorabari glacier dated the Little Ice Age maximum to around AD 1748. After the peak of the Little Ice Age, the recession of the glacier started, followed by three major stages of its advance and retreat during AD 1766, 1827 and 1878 (retreat) respectively, as indicated by the largest lichen on the boulders of four loops of terminal and lateral moraines of the glacier. If we consider that glaciations in the region started during the mid-fourteenth century, i.e. the beginning of the Little Ice Age and continued till around AD 1748, then it can be assumed that the temple remained submerged in ice/glacier for a minimum of 400 years. This is further supported by the striations on the walls of the temple. 1. Chaujar, R. K., Lichenometry of yellow Rhizocarpon geographicum as database for the recent geological activities in Himachal Pradesh. Curr. Sci., 2006, 90, 1552 1555. 2. Winchester, V. and Chaujar, R. K., Lichenometric dating of slope movements, Nant Ffrancon, North Wales. Geomorphology, 2002, 47, 61 74. 3. Winchester, V. and Harrison, S., Dendrocronology and lichenometry: an investigation into colonization, growth rates and dating on the east side of the North Patagonian Ice field, Chile. Geomorphology, 2000, 34, 181 194. 4. Winchester, V. and Harrison, S., A development of the lichenometric method applied to dating of glaciological influenced debris flows in Southern Chile. Earth Surf. Process Landforms, 1994, 19, 137 151. 5. Locke, W. W., Andrews, J. T. and Webber, P. J., A manual for lichenometry. Br. Geomorphol. Res. Group, Tech. Bull., 1979, 26, 1 47. 6. Denton, G. H. and Karlen, W., Lichenometry, its application to Holocene moraine study in Southern Alaska and Swedish lappland. Arct. Alpine Res., 1973, 5, 347 372. 7. Innes, J., Lichenometry. Prog. Phys. Geogr., 1985, 9, 187 254. 8. Bull, W. B. and Brandon, M. T., Lichen dating of earthquake generated regional rock fall events, Southern Alps, New Zealand. Geol. Soc. Am., 1998, 110, 60 84. 9. Raina, V. K., Glaciers: The Rivers of Ice, Geological Society of India, Popular Science Series No. 2, 2006, p. 48. 10. Live India, Jyotirlinga Shiva Temples, 1998; http://www.liveindia. com/jyotirlinga/kedarnath.html 11. Siddharth, B. G., Hinduism Today, 1995; http://www.hinduism today.com/archives/1995/2/1995-2-17.shtml 12. Rao, S. R., The Lost City of Dvaraka, xxii, Aditya Prakashan, 1999, p. 309. 13. Kochhar, R., The Vedic People, Orient Longman, Hyderabad, 2000. CURRENT SCIENCE, VOL. 96, NO. 5, 10 MARCH 2009 707

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In Proceedings of the 5th European Congress on Regional Geoscientific Cartography and Information System, Barcelona, Spain, 2006, vol. 1, pp. 320 321. ACKNOWLEDGEMENTS. I thank Prof. B. R. Arora, Director, Wadia Institute of Himalayan Geology, Dehra Dun for providing the necessary facilities to carry out the work. I also thank my colleagues Drs D. P. Dobhal and P. S. Negi for help during field work. Received 4 June 2008; revised accepted 7 January 2009 Late Holocene changes in hypoxia off the west coast of India: Micropalaeontological evidences R. Nigam 1, V. Prasad 2, A. Mazumder 1, *, R. Garg 2, R. Saraswat 3 and P. J. Henriques 4 1 National Institute of Oceanography, Dona Paula, Goa 403 004, India 2 Birbal Sahni Institute of Palaeobotany, 57, University Road, Lucknow 226 007, India 3 Department of Geology, University of Delhi, Delhi 110 007, India 4 St Xavier College, University of Mumbai, Mumbai 400 032, India A study has been carried out to understand benthic foraminiferal and sedimentary organic matter characteristics under low dissolved oxygen conditions off the central west coast of India. Based on the strong correlation between the present-day abundance of rectilinear bi- and triserial benthic foraminifera (RBF) and low dissolved oxygen conditions in the northeastern Arabian Sea, the geologic extent of low oxygen zone off the central west coast of India, is inferred from a core collected from the shallow water region. Persistently high relative abundance of RBF, large proportion of amorphous organic matter and protoperidinioid dinocysts throughout the time-span covered by the core that goes well beyond the beginning of human intervention, indicate that the eutrophication of coastal water and subsequent development of low dissolved oxygen conditions is a natural phenomenon that has been in existence even before anthropogenic influence. Keywords: Benthic, dissolved oxygen, foraminifera, hypoxia, organic matter, rectilinear. OXYGEN is essential for life on both land as well as under water. While the atmospheric concentration of oxygen is *For correspondence. (e-mail: abhimazumder@gmail.com) CURRENT SCIENCE, VOL. 96, NO. 5, 10 MARCH 2009