In July 2016, large chunk of ice of around 3-3.5 feet was washed from the Gangotri glacier into the Bhagirathi River. Scientists of Wadia Institute of Himalayan Geology, Dehradun said that continuous rainfall, decreased snowfall and changes in the other climatic pattern such as temperature were responsible for this.
The incident again raised the alarm bells. The global warming has been popularly blamed for the degenerating health of the glaciers worldwide. The condition of the Gangotri glacier is no different. The health of this glacier is of immense importance for India. The reason is that it is the source of river Ganges (also called Ganga). It is the most important river for the northern India.
At Gangotri region the river is known as ‘Bhagirathi’. It originates from the outermost extremity of the Gangotri glacier known as ‘Snout’ in scientific terms. The shape of the snout can be compared with an ice cave. The snout of the Gangotri Glacier from where the river originates is known as Gaumukh. The literal meaning of the term Gaumukh is Cow’s mouth. It is said to resemble the shape of cow’s mouth. It is at snout where the ice-melts & the steady flow start and the river begins.
The concerns regarding the retreating Gangotri glacier and its poor health are not new. It is known that the Gangotri Glacier is retreating 10-30 metres per year over the second half of this century. The snout of the glacier is monitored to know any advancement or recede of the glaciers.
Gangotri Glacier is situated in the Uttarkashi District of Garhwal Himalayas in Uttarakhad state of India. It is one of the largest glaciers in the Himalayas. Gangotri glacier is approximately 30.2 km long and between 0.5 and 2.5 km wide.
Is Gangotri Glacier really retreating unusually? What science says? How much retreat has been reported
At present the Gangotri Glacier is monitored by many agencies. NASA and ISRO are among them. A few documents of 19th century are also present and scientists try to come to a conclusion.
Although the exact rate of Gangotri Glacier melting can not be calculated, it is certain that the rate of retreat has speeded up post industrial era. This is a cause of concern over the health of the Gangotri glacier.
According to the information provided by Earth Observatory of NASA, Gangotri has been receding since 1780. The overall rate of retreat is 22 metres per year. But it is a matter of concern as the rate of melt has speeded up after 1971.
According to NASA’s observation, over the last 25 years, a retreat of more than 850 meters have been observed on Gangotri glacier. The rate of retreat was more than 76 meters between 1996 to 1999 alone.
According to Indian Space Research Organisation the Gangotri glacier has receded by 1.5 km in the past 30 years. The rate of retreat has not been uniform. In facts it varies a lot.
High rate of glacier retreat 38 m/y ~was observed in 1970s. The rate of retreat got reduced in 1980s. The rate of retreat was 10 m/y in 2015. In between September 2007 and June 2009 it was practically at a standstill.
Attempts were made to assess the retreat and advance of glaciers in Himalayas by using multi temporal synthetic aperture radar (SAR) data as well as optical data.
According to a study conducted by IIT Bombay, Gangotri glacier was monitored, along its central line using, Terra SAR-X (TS-X) data of 28th August, 2008 and 30th September, 2008. When the retreat of the glacier was calculated on per day basis Gangotri glacier turns out to be receding at the rate of 4 cm per day or 14.6 m per year.
What GSI says about retreating glaciers?
Geological Survey of India (GSI) says it is normal for glaciers to pass through normal glacial and recessionary periods. At present Gangotri glacier is passing through a normal recessionary trend and this phase will continue for a couple of hundred years now.”
According to a discussion paper from Ministry of Environment, Forests and climate Change, Government of India on the snout of the Gangotri glacier, was first time mapped in detail in 1935. Glacial advances and retreats are natural cyclical phenomena. Glacial period is always followed by an inter-glacial period. The world is now in an inter-glacial warm phase. The last glacial advancement occurred during the last phase of the last glacial period (15th-19th century). This period has been named. “The Little Ice Age”. Since then, as a result of the subsequent warming phase, all glaciers have been retreating.
The rate of retreat in recent times has, however, been much more rapid than the gradual retreat expected in an inter-glacial warming phase. This, glaciologists and climatologists believe, is due to global warming. This climatic change brought about by human or anthropogenic activity in the post-industrialisation period has already resulted in a global increase in the average surface temperature by 0.6 o C. A natural consequence of this is increased melt from ice caps and glaciers.