Bengaluru: It was not a torrential downpour which triggered the catastrophe in Kedarnath valley, claiming the lives of hundreds of pilgrims on June 16 and 17.
For, images beamed by satellites of National Ocean and Atmospheric Administration, USA, and Cartosat satellite of Indian Space Research Organisation have revealed a new dimension to the disaster in Uttarakhand.
Though the skies opened up on June 16 as forecast by the Indian Meteorological Department and satellite images confirm a dense cloud cover over the valley, the trigger was a couple of kilometres up-stream of the river Mandakini.
A lake formed by landslides over the years came apart, opening a new canal of the river and flooding the valley. Satellite images bear out the formation of the lake as well as its disintegration because of melting of glaciers. In scientific jargon, the devastation was wrought by a glacial lake outburst flood.
“It occurs when a lake is created behind an obstruction created by a landslide. When this dam built by moraine (soil and rock left behind by glaciers) breaks, water behind the dam gushes out,” said Prof. Jayaraman Srinivasan, chairperson, Divecha Centre for Climate Change at Indian Institute of Science.
He said the valley had earlier endured rains of the magnitude witnessed on June 16, but was not flooded or claimed lives of people. Though such downpours cannot be attributed to global warming, their frequency had risen by 50 per cent over the past 50 years.
Reason: the atmosphere was turning unstable because of an increase in water vapour due to global warming.
