A new study led by scientists at Bhopal’s IISER has identified a small region in the Karakoram ranges where there was no significant loss of glacial mass. The study attributed it to the possible constant feeding of fresh snow triggered by precipitation events caused by the passing western disturbances Some pockets of glaciated regions in the Karakoram ranges are bucking the global retreating trend driven by rising temperatures and global warming, a new study has found. The Karakoram ranges – extending from Tajikistan, Afghanistan, Pakistan and India up to China – are home to some of the world’s most active glacial regions. Global warming has accelerated the rate of global glacial retreats in the Himalayas and elsewhere. It has pushed the melting of sea ice along both the north and the south poles, resulting in rising sea levels world over. But the new study led by scientists at Indian Institute of Science Education and Research (IISER), Bhopal, has identified a small region in the Karakoram ranges where there was no significant loss of glacial mass. The Department of Science and Technology (DST)-supported study attributed healthy glaciers of the Karakoram ranges to the possible constant feeding of fresh snow triggered by precipitation events caused by the passing western disturbances (WDs) over the region during winter months. “The peculiar behaviour seems to be confined to a small region. But this anomaly in the Karakoram ranges provides a ray of hope of delaying the glacial retreat,” said Pankaj Kumar, associate professor at the Department and Earth and Environmental Sciences, IISER, Bhopal. Western disturbances are eastward propagating upper air troughs (rain bearing cloud bands) which cause solid precipitation (snowfall) over higher altitudes like the north-western Himalayas. They cause rainfall over India’s northern plains during December-February months. Due to its high elevation, the mighty Himalayas act as a barrier to the southwest monsoon winds – the major source of rainfall and hence water over India. As a result, it is the western disturbances-triggered rainfall which are more dominant over the Karakoram than the monsoon-triggered rainfall. That is why there are large-scale variations in the rainfall between the western and the eastern Himalayas. For example, the annual precipitation in Ladakh is 300 mm, it is 1,400 mm in Kathmandu and 4,000 mm at Pasighat in the Brahmaputra basin. The rainy season here can last anywhere from two to eight months along the west and eastward regions, respectively. Several earlier studies had noted a rising frequency and intensification of the western disturbances during the last two decades. This could be a boon for the Karakoram glaciers, the IISER-Bhopal study suggests. “WDs are the primary feeder of snowfall for the region during winters. Our study suggests they constitute about around 65 per cent of the total seasonal snowfall volume and about 53 per cent of the total seasonal precipitation, thus easily making them the most important source of moisture. The precipitation intensity of WDs impacting Karakoram has increased by around 10 per cent in last two decades, which only enhances their role in sustaining the regional anomaly,” said Aaquib Javed, a PhD student and lead author of the study that was submitted to the Journal of Climate of the American Meteorological Society on Tuesday. The snowfall volume contributed by WDs over the core glacier regions of Karakoram ranges has increased by about 27 per cent in recent decades, the researchers claimed. Whereas, precipitation received from non-WD sources had significantly decreased, by about 17 per cent, they observed.
