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Frequent marine heatwaves in Indian Ocean disrupt India‘s monsoon patterns

  • February 3, 2022
  • Posted by: OptimizeIAS Team
  • Category: DPN Topics
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Frequent marine heatwaves in Indian Ocean disrupt India‘s monsoon patterns

TOPIC: Environment

Context- Marine heat waves (MHW) in the Indian Ocean region have increased significantly in the past few decades, according to a new study published in the journal JGR Oceans showed.

Concept-

Marine heat waves (MHW)

  • Marine heat waves (MHW) are periods of increased temperatures over seas and oceans.
  • Such heat waves are caused by an increase in the heat content of oceans, especially in the upper
  • Worldwide, they are one of the major results of human-induced global warming.
  • During an MHW, the average temperatures of the ocean surface (up to a depth of 300 feet) goes 5-7 degrees Celsius above normal.

Marine Heat Waves in Indian Ocean:

  • The number of MHWs in the West Indian ocean increased by around 1.5 events per decade between 1982 and 2018.
  • The occurrences went up by around 0.5 events per decade in North Bay of Bengal in the same period.
  • There were a total of 66 events in West Indian Ocean and 94 in North Bay of Bengal in the 36 years.

Link between marine heatwaves and atmospheric circulation and Monsoon rainfall

  • Around 90 per cent of the warming caused by greenhouse gas emissions is absorbed by the oceans.
  • The increase in marine heat waves was due to rapid warming in the Indian Ocean and strong El Nino events.
    • El Nino is one phase of the El Nino Southern Oscillation (ENSO) phenomenon which has a generally warming effect on the world’s ocean and land surfaces.
  • The marine heat waves in the Indian Ocean are also majorly impacting the southwest monsoon — the main rain-bearing system over the Indian subcontinent.
  • The MHWs in the two worst-hit regions reduce monsoon rainfall over central India, the study established.
  • The occurrence of MHW in North Bay of Bengal increases rainfall over the southern peninsular area.

Impacts of Marine Heat waves

  • Impacts on weather conditions around the world.
  • Habitat destruction due to coral bleaching,
  • Seagrass destruction and loss of kelp forests,
  • Affecting the fisheries sector adversely.

Case Study-

  • An underwater survey showed 85 per cent of corals in the Gulf of Mannar near the Tamil Nadu coast got bleached after the marine heatwave in May 2020.
Environment Frequent marine heatwaves in Indian Ocean disrupt India‘s monsoon patterns

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