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Marine heat waves (MHWs) & Impacts on World’s Oceans Context:

  • Category
    Ecology and Environment
  • Published
    28th Jul, 2023


According to a recent forecast of Mercator Ocean International, Marine Heat Waves have gripped the oceans of north-east Pacific, the southern hemisphere in the southern Indian Ocean and the Pacific, the north-east Atlantic, tropical North Atlantic, and the Mediterranean sea.

About the forecast:

Researchers are making predictions that the occurrence of Marine Heat Waves will increase as much as 50-fold by 2100 as compared to the pre-industrial times.

What are marine heat waves?

  • A marine heat wave is an extreme weather event.
  • It occurs when the surface temperature of a particular region of the sea rises to 3 or 4 degree Celsius above the average temperature for at least five days.
  • MHWs can last for weeks, months or even years.

What are the impacts of marine heat waves on ocean life?

  • Catastrophic for marine life: Marine Heat waves may cause the deaths of several marine species, alter their migration patterns, and lead to coral bleaching and even impact weather patterns. Although an increase of 3 or 4 degrees Celsius in average temperatures may not be much for humans, it can be catastrophic for marine life.
  • Destroying kelp forest: MHWs destroy kelp forests and fundamentally altered the ecosystem of the coast.
  • Enhances Coral Bleaching: A 2010 study showed that more than 80 per cent of surveyed corals had bleached and over 40 per cent of the total surveyed had died.
    • Corals are very sensitive to the temperature of the water in which they live.
  • Disturbs food web: MHWs also fuel the growth of invasive alien species, which can be destructive to marine food webs.

    Factors contributing to Marine Heat Waves:

    • Global Warming: Rise in temperatures due to Anthropogenic events, has led to an increase in global temperatures which ultimately contributes to ocean warming.
    • El Nino: Winds can enhance or suppress the warming in a marine heatwaves, and climate models like El Niño can change the likelihood of events occurring in certain regions.
    • Ocean currents: The most common drivers of marine heatwaves include ocean currents which can build up areas of warm water and air-sea heat flux, or warming through the ocean surface from the atmosphere.

    How do marine heat waves affect humans?

    • Increasing the intensity of storms: Higher ocean temperatures, which are associated with MHWs, can make storms like hurricanes and tropical cyclones stronger.
    • Increased evaporation and heat: With warmer temperatures, the rate of evaporation escalates and so does the transfer of heat from the oceans to the air.
    • More devastating effects: When storms travel across hot oceans, they gather more water vapour and heat. This results in more powerful winds, heavier rainfall and more flooding when storms reach the land — meaning heightened devastation for humans.

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