Some Himalayan Glaciers Have Been Melting For 400 Years, Scientists Discover

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.

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Himalayan glaciers experienced significant mass loss during later phases of little ice age

Mayank Shekhar et al. (2017) Scientific Reports, September 2017

Abstract

To date, there is a gap in the data about the state and mass balance of glaciers in the climate-sensitive subtropical regions during the Little Ice Age (LIA). Here, based on an unprecedented tree-ring sampling coverage, we present the longest reconstructed mass balance record for the Western Himalayan glaciers, dating to 1615. Our results confirm that the later phase of LIA was substantially briefer and weaker in the Himalaya than in the Arctic and subarctic regions. Furthermore, analysis of the time-series of the mass-balance against other time-series shows clear evidence of the existence of (i) a significant glacial decay and a significantly weaker magnitude of glaciation during the latter half of the LIA; (ii) a weak regional mass balance dependence on either the El Niño-Southern Oscillation (ENSO) or the Total Solar Irradiance (TSI) taken in isolation, but a considerable combined influence of both of them during the LIA; and (iii) in addition to anthropogenic climate change, the strong effect from the increased yearly concurrence of extremely high TSI with El Niño over the past five decades, resulting in severe glacial mass loss. The generated mass balance time-series can serve as a source of reliable reconstructed data to the scientific community.