Warming of Indian Ocean

General Studies Paper -3

Context: According to the Indian Institute of Tropical Meteorology (IITM), From 1950-2020, the Indian Ocean had become warmer by 1.2°C and climate models expect it to heat up a further 1.7°C–3.8°C from 2020–2100.

Key Highlights

• Marine heatwaves: Marine heatwaves are expected to increase tenfold from the current average of 20 days per year to 220–250 days per year. The tropical Indian Ocean will likely be in a “near-permanent heatwave state.
  • It causes habitat destruction through coral bleaching, seagrass loss and the degradation of kelp forests, adversely affecting the fisheries sector.
• The heat content of the Indian Ocean, when measured from surface to a depth of 2,000 meters, is currently increasing at the rate of 4.5 zetta-joules per decade, and is predicted to increase at a rate of 16–22 zetta-joules per decade in the future.
  • Joule is a unit of energy and one zetta-joule is equal to one billion-trillion joules (10^21).
• Thermal expansion: Rising heat content causes the volume of water to increase, called the thermal expansion of water.
  • It is responsible for more than half of the sea-level rise in the Indian Ocean -larger than the changes arising from glacier and sea-ice melting.
• The frequency of extreme dipole events is predicted to increase by 66% whereas the frequency of moderate events is to decrease by 52% by the end of the 21st century.

Consequences of extreme heating

• It has significant repercussions for the southwest monsoon season, which provides about 70 per cent of India’s annual rainfall.
• The warming could also lead to more frequent and intense extreme weather events, such as tropical cyclones and floods, as well as a rise in sea levels due to thermal expansion.
• The Indian Ocean Dipole (IOD), is also expected to change due to the warming of the Indian Ocean.
  • In the positive phase of the IOD, when the western parts of the Indian Ocean are warmer than the eastern parts, monsoon rainfall generally increases across many regions in India and the rest of South Asia.
  • In the negative phase, when the western parts of the ocean are cooler than the eastern parts, less than normal rainfall is observed during the post-monsoon period in northwestern India.
• The pH levels of the ocean’s waters are projected to decrease from about 8.1 currently to 7.7 by the end of the century.
  • Changes in pH may be detrimental since many marine organisms are sensitive to the change in ocean acidity.

Way Ahead

• Addressing the impending challenges in the Indian Ocean demands a multifaceted approach. Reducing GHG emissions and building climate-resilient infrastructure are the most effective strategies to mitigate the current and future impacts of warming.
• Conserving marine ecosystems through sustainable practices and improving forecasting capabilities can strengthen the region’s resilience to extreme weather events.