Glaciers ending in lakes lose ice fastest: Study

Lake-ending glaciers: what did the study find?

An ice cube melts faster in a glass of water than on a plate. Glaciers behave the same way: those that end in water lose ice much faster than those that end on land.

• A new study looked at glaciers that end in lakes, oceans or ice shelves instead of on land.
• These glaciers are just over 3% of all glaciers.
• Yet they caused more than half of all glacier ice loss from 2000 to 2019, losing 134 billion tonnes of ice a year.
• Lake-ending glaciers flow 10% faster and ocean-ending glaciers 44% faster than land-ending ones.
• The reasons: big chunks break off as icebergs (calving), and lake or sea water melts ice below the waterline.
• As the climate warms, glacier lakes are becoming more common, so this effect may grow.

What are calving and glacial lake outburst floods?

A glacier is a large mass of ice that moves slowly downhill under its own weight. Where it ends is called its snout or terminus.

Calving is when large blocks of ice break off the front of a glacier into water. Water also melts the ice from below, so these glaciers shrink fast.

As glaciers melt and retreat, water collects behind loose rock and soil left by the glacier, called a moraine. This forms a glacial lake.

If the moraine wall breaks, for example after heavy rain, an avalanche or an earthquake, the lake empties suddenly. This is a glacial lake outburst flood (GLOF). In October 2023, a GLOF from South Lhonak Lake in Sikkim damaged the Teesta III dam at Chungthang.

Where a glacier ends changes how fast it shrinks

Which rules and plans apply?

• Disaster Management Act, 2005: sets up the NDMA and the system to prepare for disasters like GLOFs.
• NDMA guidelines on managing GLOFs (2020): mapping lakes, early warning and lowering risky lakes.
• National Mission for Sustaining the Himalayan Ecosystem: one of the missions under the National Action Plan on Climate Change.
• Sendai Framework for Disaster Risk Reduction (2015–2030): global plan India follows.

Why does lake-ending glaciers matter?

What are the problems with lake-ending glaciers?

• Many Himalayan glacier lakes are remote and poorly monitored.
• Dams and roads are being built in high-risk valleys.
• Early warning systems are few and often fail.
• Climate models may not fully count glaciers that end in water.

What should be done next on lake-ending glaciers?

• Map and watch all risky glacier lakes with satellites and sensors.
• Install early warning systems and train local communities.
• Lower water levels in dangerous lakes where possible.
• Check GLOF risk before approving dams in high valleys.

What can Prelims ask on lake-ending glaciers?

Prelims probability: Expect a statement question on glacier terms: calving is ice breaking off as icebergs, and a glacial lake outburst flood happens when a glacier lake’s wall breaks.

• Calving = ice breaking off a glacier’s front into water as icebergs.
• GLOF = sudden flood when a glacial lake’s moraine wall breaks.
• South Lhonak Lake (Sikkim) GLOF, October 2023: Teesta III dam damaged.
• Glacier–river pairs: Gangotri–Bhagirathi, Zemu–Teesta, Bara Shigri–Chenab, Milam–Gori Ganga, Bandarpunch–Yamuna.
• Water-ending glaciers: just over 3% of glaciers, over half of ice loss (2000–2019).

How to write about lake-ending glaciers in Mains

Practice question (15 marks, 250 words): Glacial lake outburst floods are an emerging threat in the Indian Himalaya. Discuss the causes and suggest measures to reduce the risk.

• Intro: study on lake-ending glaciers losing ice fastest.
• Causes: warming, retreat, moraine-dammed lakes, triggers like rain and quakes.
• Example: South Lhonak 2023, Kedarnath 2013.
• Measures: mapping, early warning, lake lowering, safer dam planning, NDMA guidelines.
• Conclusion: adapt now as glacier lakes grow.