A glacier is a mass of ice consisting of compacted and recrystallized ice on land that flows down under its own weight due to gravity. Glaciers are lying largely or wholly on land and showing evidence of past or present movement. Snowfields that persist through the summer melt season are not glaciers because they lack motion.
Presently, glaciers cover nearly 15 million km2 or about 10 % of land surface and contain 2.15 % of all water on Earth. 96 % of all glacial ice on this planet is in Antarctica (84.5%) and Greenland (12%), both of which are nearly covered by glaciers. Australia is the only continent lacking glaciers.
Glaciers in Bhaga basin, Lahaul & Spiti district, H.P.
Erosional landforms (GSI)
Erosional landforms (GSI)
Glaciers are one of the most important processes modifying Earth's surface through erosion, transport and deposition. These processes result in carving out the earth’s surface and formation of easily recognizable landforms, both erosional and depositional. Majority of the present day glacial landforms are developed during the Pleistocene epoch, commonly called as Ice Age (1.6 million to 10,000 years ago).
Temperate glacier in Himalaya (Hamtah-GSI)
Types of Glacier:
Ahlmann (1948) introduced a three-fold glacier classification, viz, thermal, dynamic and morphological.
Thermal Classification
The temperature of a glacier plays an important role in its dynamic activity. Its sub categories are recognized as:
a. Temperate glaciers: Glacier ice is at or near its pressure melting temperature.
b. Polar or cold based glaciers: Glacier ice is below the pressure melting temperature most of the time.
c. Sub polar glaciers: Intermediate type glaciers.
Polar glacier in Arctic (Vestre Broggerbreen-GSI)
Dynamic Classification
The dynamic classification of glaciers is based on the nature of their mass balance, which determines whether they are advancing, stationary or retreating.
Morphological Classification
The morphology of the glaciers is controlled largely by the relationship between glacier ice and topography. It can be categorized as Alpine, Piedmont, Ice sheet and Ice cap. Ice sheets and ice caps are common in Polar Regions.
When a valley glacier flows from a mountain valley on to a wider plain and spreads out, or where two or more valley glaciers coalesce at the base of a mountain range, they form much more extensive ice cover known as Piedmont glaciers.
Continental glaciers are also called as ice sheets, cover vast areas (at least 50,000 sq km) and are unconfined by topography. In contrast to valley glaciers, which flow downhill within the confines of a valley, continental glaciers flow out in all directions from a central area of accumulation.
In practice, however, glaciers are classified as valley, mountain and glacierets. A valley glacier is confined to a mountain valley or an interconnected system of mountain valleys. These are invariably small in comparison to continental glaciers, even though some are more than 100 km long, several km wide and several hundred meters thick. For example Gangotri glacier is more than 30 km long and covers an area of about 148 sq km. Mountain glaciers are small glaciers on the mountain slopes without well-defined valleys. Glacierets are very small glaciers usually perched on mountain slopes.
Valley glacier in Himalaya (GSI)
Mountain glacier in Himalaya (GSI)
Erosion of mountains by valley glaciers produces U-shaped glacial troughs and hanging valleys. Sharp angular landforms including cirques, aretes and horns, etc. are also products of glaciers. When a large valley glacier directly calves in to a sea, it is known as fjiord.
U shaped valley profile, Uttarakhand (GSI)
Kansgvegan glacier Fijord, Arctic (GSI)
How/what do we study?
Glaciology Division, Geological Survey of India, Northern Region, Lucknow is mainly engaged in following glaciological studies:
Glacier inventory
Glacier regimen
Secular movement studies
Glacier Inventory
GSI has prepared a detailed inventory of glaciers based on Survey of India toposheets, aerial photographs and satellite imageries with limited field checks. As per the latest available data, Indian Himalaya contains 9,575 glaciers distributed in the States of Jammu & Kashmir, Himachal Pradesh, Uttarakhand, Sikkim and Arunachal Pradesh. Highest concentration of glaciers is in Jammu & Kashmir while least concentration is in Arunachal Pradesh.
Significance of Glaciers:
Glaciers are one of the most important sources of fresh water. The ice locked up in the glacier melts during summer ablation season and augment water in the rivers. In winters, glaciers melt only due to pressure melting and base flow is maintained. In India, perennial Himalayan rivers owe their existence to the glaciers. Another important economic aspect of glaciers is the huge volume of sand and gravel generated due to glacial erosion and transportation. These sediments are used as building material.
The wide distribution in space and time make glaciers as one of the most important proxy record for the study of climate change. The retreat of glaciers suggests climate change. Moreover, as glaciers are directly linked to climate, their deposits and landforms provide evidence for interpretation of climatic changes that have taken place during the past.
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Glacier Regimen
Glacier regimen studies encompass study of all the aspects of glaciers including mass balance, dynamics, hydrology, microclimate, suspended sediment transport, etc. The behavior of a glacier depends on its mass balance or budget, which is the relationship between net accumulation and ablation. If a glacier possesses a balanced budget, its terminus remains stationary, whereas a positive or negative budget results in advance or retreat of the terminus, respectively. Fixing a specific network of stakes carries out mass balance and glacier dynamic studies. The monitoring and coordination stakes at a regular interval provide data on mass balance and glacier dynamics. Glaciers move at varying rates depending on slope, supply of snow and season. Hydrological observations are useful in estimating the variations in glacier melt in space and time, besides computing water balance. Data on microclimate studies are analysed for understanding their role in glacier melting.
Glacier inventory map of Uttarakhand
Location of Glaciers studied by GSI
GSI has carried out detailed glaciological studies on Neh Nar and Rulung, J&K, Gara, Gor Garang, Shaune Garang, and Hamtah, H.P., Tipra Bank and Dunagiri, Uttarakhand and Zemu and Changme Khangpu glaciers, Sikkim.
Secular Movement Studies
The secular movement studies are carried out by marking the terminus/snout of the glacier with reference to a known fixed point on the ground at a certain time interval. The data on secular movement is used to assess whether a glacier is receding or advancing. GSI has undertaken secular movement studies on selected glaciers since the beginning of twentieth century. Majority of glaciers have shown recession in their frontal part, besides vertical shrinkage.
Cumulative specific balance of Himalayan glaciers
Mass balance map of Hamtah glacier
Recession of Himalayan glaciers studied by GSI
Glacier Recession and its Survival:
The studies carried out by the Geological Survey of India since the beginning of twentieth century, have revealed that majority of glaciers of the Himalayan region are passing through a phase of recession as has been the case with the glaciers located in other parts of the world. The retreat of the glaciers is continuing but there has not been any alarming change in the rate of retreat of the glaciers during couple of decades. Few long-term data, however, do suggest higher rate of recession after 1950 or so.
Even in the Himalayan region, the rate of recession in different climatic zones is found to be variable in different years. This variable rate of recession can be attributed to several factors like micro as well as macroclimate, orography, size of the glacier, nature of nourishment, etc.
The recession of glaciers could be attributed to the phenomenon of global warming, a subject which is still debatable. The recession may result due to subnormal snowfall, higher temperature during summer, less severe winter or a combination of all of them. Thus, overall climate change may be considered as the driving force behind the recession of glaciers.
We are aware that the recession of glacier is a natural cyclic process. Presently, we are in an interglacial phase during which the recession of the glaciers is a natural phenomenon. Throughout the history of the earth there have been a number of glacial and inter-glacial periods. The last period of glaciation ceased at about 10,000 years B.P. Since then, a period of deglaciation has set in with little fluctuations in between. During the interglacial phase (Holocene period), pulses of minor glacial advancements commonly referred to as ‘Little Ice Age’ (LIA) has been reported by various workers in different parts of the World including the Indian Himalaya. During the last 1000 years, a little ice age appeared between 1450 and 1850 AD, when mountain glaciers all over the World advanced.
GSI is continuing its emphasis on monitoring of the Himalayan glaciers in different basins. During the last ten years GSI has monitored twenty five glaciers, viz. Hamtah, Jobri, Beas Kund, Gl. No. 30, Sara Umga, Mantalai (Gl. No. 115), Tal, Manimahesh, Yoche Lungpa, Mulkila, Panchi nala – I, Panchi nala –II, Gangstang, Tingal Goh in Himachal Pradesh and Bandarpunch, Jaundar Bamak, Jhajju Bamak, Tilku, Meola, Jhulang, Chipa, Pindari, Bhagirathi Kharak, Adikailash, Nikarchu and Ramganga in Uttarakhand.
GSI has undertaken a few pilot studies on artificial retardation and augmentation of glacier melt. The studies do indicate that the recession of glaciers can be checked to a very limited extent (site specific only) through artificial measures. However, such projects cannot be undertaken on large scale in view of the nature of Indian Himalayan glaciers (debris covered), economic feasibility, scale of operation and likely pollution. Since the recession of glaciers is a natural process and we cannot single out any one meteorological parameter responsible for the present situation, the possible mitigation strategy should include (a) monitoring of the glaciers, (b) expansion and diversification of the meteorological observation network, (c) construction of dams in the Himalayan region for better utilisation of the water resources, (e) reduction in deforestation activities, new afforestation programmes and preservation of ecology, particularly in high altitude regions.
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