Warming of Indian Ocean 

GS-1 Mains : Geography 

Revision Notes 

Question : Analyze the projected changes in Indian Ocean Dipole (IOD) patterns due to warming trends in the Indian Ocean and their implications for monsoon rainfall in India and South Asia

Source: Indian Institute of Tropical Meteorology (IITM)

Key Findings:

  • Temperature Increase: The Indian Ocean has warmed by 1.2°C from 1950-2020 and is projected to heat up further by 1.7°C-3.8°C by 2100.
  • Marine Heatwaves: Frequency expected to increase tenfold (220-250 days/year) from the current average (20 days/year). This can cause:
    • Habitat destruction through coral bleaching, seagrass loss, and kelp forest degradation.
    • Negative impacts on fisheries.
  • Heat Content: Increasing rapidly (4.5 zetta-joules per decade), projected to reach 16-22 zetta-joules per decade in the future. (1 zetta-joule = 1 billion-trillion joules)
  • Thermal Expansion: Rising heat content leads to water volume increase, contributing to more than half of the Indian Ocean’s sea-level rise (more than glacier/ice melt).
  • Extreme Dipole Events: Frequency of extreme events predicted to increase by 66%, while moderate events decrease by 52% by the 21st century.

What are Marine Heat Waves?

  • Extreme weather events where sea surface temperatures rise 3-4°C above average for at least five days (can last weeks, months, or years).

Consequences of Extreme Heating:

  • Monsoons: Significant repercussions for the southwest monsoon, which provides 70% of India’s annual rainfall.
  • Extreme Weather: Warming could lead to more frequent and intense cyclones, floods, and sea-level rise.
  • Indian Ocean Dipole (IOD): Warming is expected to alter IOD patterns:
    • Positive IOD (warmer west Indian Ocean) – generally increases monsoon rainfall in India and South Asia.
    • Negative IOD (cooler west Indian Ocean) – less than normal rainfall observed during the post-monsoon period in northwestern India.
  • Ocean Acidification: Ocean pH levels projected to decrease from 8.1 to 7.7 by the end of the century, potentially harming marine organisms sensitive to acidity changes.

Way Forward:

  • Mitigate Impacts: Reduce greenhouse gas emissions and build climate-resilient infrastructure.
  • Strengthen Resilience: Conserve marine ecosystems through sustainable practices and improve forecasting capabilities for extreme weather events.


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