LUCKNOW: Global warming and climate change are serious issues that are drawing the attention of the world. However, the phenomenon of Himalayan glaciers melting is not a recent one. In fact, it has been happening for 400 years.

It was during the Little Ice Age, a period of cold conditions from 1645 CE-1715 CE, that Arctic and sub-Arctic glaciers were expanding but Himalayan glaciers were melting.

Melting of glaciers is not only caused due to industrialization and global warming but natural factors like oceanic currents and total solar irradiance (TSI), which means total sun energy coming to earth, are equally responsible. Oceanic currents affect monsoon and since glaciers are dependent on monsoon precipitation in the form of snow, any change in it affects glaciers. TSI affects temperature and other climatic factors which affect glaciers.

A study by a team of nine scientists from Birbal Sahni Institute of Palaeosciences has unfolded the health status and behaviour of Himalayan glaciers over a period of four centuries.

The scientists used tree ring data of around 400 years from Himalayan conifers in the glaciated valleys of Uttarakhand, Himachal Pradesh and Kashmir for research.

The study has been published in the prestigious international journal ‘Scientific Reports’ of Nature group.

“Glacier melting has been an area of great concern, as glaciers are huge water reservoirs and a source of fresh water. Our study highlights the loss in volume of the Himalayan glaciers and shows that even when European glaciers were expanding, Himalayan glaciers were shrinking,” said senior scientist Parminder S Ranhotra.

Ranhotra added that there is no instrument to measure glacier health over such a long period of time and the team used tree rings, a reliable technique to study expansion and melting of Himalayan glaciers centuries ago. The team is the first in the country to use this technique to study loss in volume of glaciers, he added.

Lead author of the research Mayank Shekhar said the team conducted research on 13 glaciers. Three of these were in Jammu & Kashmir, six in Himachal Pradesh and four in Uttarakhand.

The research shows that every 10 years, Uttarakhand and Himachal Pradesh glaciers were melting at 6% and 5% respectively, while glaciers of J&K were stable. The reason is that Uttarakhand and Himachal glaciers are dependent on Indian summer monsoon system, governed by oceanic currents and changes in solar energy. On the other hand, glaciers of J&K are dependent on winter precipitation mainly in the form of snowfall, which has lesser impact on glacier volume.

“This is a complex subject but the study provides compelling evidence of global significance for understanding the dynamics of past glacier advances and retreats in the context of changing climatic conditions and their drivers in each of the three major sectors of Himalayas,” said BSIP director Sunil Bajpai.

What is tree tech?

BSIP is the first institute in the country to use tree ring technology to study glaciers. In this technology, the width of a tree ring is analysed to find climatic change. Without cutting the tree, scientists draw out a section of an old tree and conduct research on its rings. If the width of the ring is thick, it reflects favourable climatic conditions and if the ring is thin, it indicates the tree was in stress condition. Scientists said tree rings reflect the changing behaviour of glaciers due to common forcing factors like rainfall and temperature.

How TSI and ocean current affect glaciers

Total solar irradiance is when certain chemical changes in sunlight affect temperature and other climatic factors. High or low temperatures affect glaciers and very high temperature might lead to loss in volume of glaciers. Oceanic currents affect monsoon, since glaciers are dependent on monsoon precipitation in the form of snow.

