Glacial Retreat in Arunachal Pradesh

Glacial Retreat in Arunachal Pradesh

Sub : Geo

Sec: Climatology

Why in News

• A recent study has revealed that Arunachal Pradesh lost 110 glaciers between 1988 and 2020, with a retreat rate of 16.94 sq. km per year. This alarming trend raises concerns about glacial lake outburst floods (GLOFs) and the long-term impact of climate change on the Himalayan ecosystem.

Key Findings of the Study:

• The study observed the disappearance of 110 glaciers over 32 years.
• Glacial cover reduced by 309.85 sq. km, which accounts for a 47% loss from the original 585.23 sq. km.
• The number of glaciers declined from 756 to 646 within the study period.
• The research focused on glaciers in Tawang, Lohit, West Kameng, Kurung Kumey, Upper Siang, and Upper Dibang Valley districts.
• Most glaciers were situated at an elevation of 4,500-4,800 metres above sea level.
• They were predominantly north-facing and confined between a slope of 15° to 35°.
• Remote sensing and Geographic Information System (GIS) tools were employed to track glacier boundaries.
• The study referenced data from the Randolph Glacier Inventory of Global Land Ice Measurements from Space.

About Glacier Retreat:

• Glacial retreat refers to the process where glaciers diminish in size due to melting and sublimation exceeding the accumulation of new snow and ice.
• This phenomenon is a significant indicator of climate change and has far-reaching environmental, economic, and social implications.
• Causes of Glacial Retreat:
  • Climate Change: Rising global temperatures lead to increased melting of glacier ice. Since the late 1970s, glaciers have been in a declining state primarily due to human-induced climate change.
  • Reduced Snowfall: Decreased precipitation in the form of snow limits the replenishment of glaciers, contributing to their shrinkage.
• Global Impact:
  • Melting glaciers contribute significantly to sea-level rise. Since 1961, glacial melting has raised sea levels by approximately 2.7 centimetres.
  • The retreat of glaciers can fundamentally change landscapes, leading to the formation of glacial lakes and increasing the risk of glacial lake outburst floods (GLOFs).
• Consequences:
  • The retreat of glaciers will affect freshwater availability, distribution, and ecosystem health.
  • Smaller glaciers (below 5 sq. km) are shrinking at the fastest rate.
  • While precipitation trends remain statistically insignificant, erratic rainfall patterns indicate unpredictable climate shifts.
  • Increased risk of glacial lake outburst floods (GLOFs) poses a major hazard to downstream communities and infrastructure.
  • The rapid loss of ice is expected to disrupt regional hydrological balance and contribute to global sea-level rise.
• The Himalayan region, known as the ‘Third Pole’, is home to the largest collection of glaciers outside the polar areas.
• Temperature in the Himalayas has increased by 1.6°C over the last century.
• The northwestern Himalayas have experienced a temperature rise higher than the global average.
• The eastern Himalayan region is warming at a higher rate than the global average, with temperature increases ranging between 0.1° and 0.8°C per decade.
• By the end of the century, temperatures in the region are expected to rise by 5-6°C, while precipitation is projected to increase by 20-30%.

What Are Glaciers?

• Glaciers are massive, dense ice formations found on mountains, moving due to gravity and their own weight.
• As glaciers move, they erode the underlying land, breaking rocks into a material known as moraine. This moraine includes particles of various sizes, from large boulders to fine “rock flour.”
• When snow falls and accumulates new layers over time, it gets compressed into large, thick masses of ice, forming glaciers.
• The upper part of the glacier — called the accumulation zone — receives precipitation in the form of snow, which accumulates over time.
• But in the lower part of the glacier — called the ablation zone — there is more melting of the snow and ice than accumulation.
• The balance between the accumulated and melted snow is known as the glacier mass balance, which determines the health of the glacier.
• Glaciers also regulate river flow and counter global warming.

What are GLOFs?

• GLOFs are disaster events caused by the abrupt discharge of water from glacial lakes — large bodies of water that sit in front of, on top of, or beneath a melting glacier.
• As a glacier withdraws, it leaves behind a depression that gets filled with meltwater, thereby forming a lake.
• The more the glacier recedes, the bigger and more dangerous the lake becomes.
• Such lakes are mostly dammed by unstable ice or sediment composed of loose rock and debris.
• In case the boundary around them breaks, huge amounts of water rush down the side of the mountains, which could cause flooding in the downstream areas, which is referred to as a GLOF event.

Reasons for GLOFs:

• GLOFs can be triggered by various reasons, including glacial calving, where sizable ice chunks detach from the glacier into the lake, inducing sudden water displacement.
• Incidents such as avalanches or landslides can also impact the stability of the boundary around a glacial lake, leading to its failure, and the rapid discharge of water.
• Rising surface temperatures across the globe, including India, have increased the risk of GLOFs.
• The floodwaters can submerge valleys, obliterate infrastructure such as roads, bridges, and buildings, and result in significant loss of life and livelihoods.
• South Lhonak: The South Lhonak Lake appeared in satellite imagery in 1962. It expanded from 17 hectares in 1977 to 167 hectares by 2023. In 2023, heavy rains caused the lake’s moraine dam to breach, raising the Teesta River’s water level by six meters, resulting in the collapse of the Teesta III dam and widespread damage.