Oceans Great Dying 2.0


    In News

    • Recently, a study revealed that the marine heat wave that hit the western Indian Ocean and the northern Bay of Bengal the most will be a permanent feature by the end of the century.

    Major outcomes of the recent study

    • From 1901 to 2012: the western Indian Ocean warmed up by 1.28°C against an increase of 0.78°C recorded in other parts of the Indian Ocean.
      • The surface waters of the Bay of Bengal stay largely above 28°C.
    • The pattern emerging from the Arabian Sea is also concerning
      • It used to be cooler than 28°C, which means that it was not always fertile to support the formation of cyclones.
      • However, during the last few decades, the Arabian Sea has warmed up rapidly, with temperature trends crossing 1.2-1.4°C in parts of Arabian Sea since the 1950s, which is quite large.
      • Now the Arabian Sea temperatures are often above 28°C, and it favours cyclones.
    • The duration and frequency of marine heatwaves also showed an upward trend
      • They increased by roughly 20 days per decade and 1.5-2 events per decade between 1982 and 2019.

    Marine heatwaves

    • Meaning
      • The term marine heatwaves were coined for the first time only in 2011.
      • This was after certain pockets of Western Australia experienced abnormally high sea surface temperatures, exceeding 3°C above average.
    • Factors associated
      • These events often accompany El Niño events in the Pacific Ocean.
      • Other factors such as increased warming and weak winds also contribute to its formation. 
    •  El Nino
      • This is a name given to the periodic development of a warm ocean current along the coast of Peru as a temporary replacement of the cold Peruvian current.
      • ‘El Nino’ is a Spanish word meaning ‘the child’, and refers to the baby Christ, as this current starts flowing during Christmas.
      •  The presence of the El Nino leads to an increase in sea-surface temperatures and weakening of the trade winds in the region
      • In a normal monsoon year (without El Nino), the pressure distribution along the coast of Peru in South America has a higher pressure than the region near northern Australia and South East Asia.

    Issues cited by the study

    • Warming up of the oceans: As the globe warms up to unprecedented levels, it boils the oceans as well. Being a climate moderator for the planet, the warming up of the oceans fundamentally disrupts the climate cycle.
    • Changing ocean currents: High ocean temperatures are changing ocean currents. They seem to have picked up the pace by 15 per cent per decade from 1990 to 2013 due to human-driven activities.
    • Tropical oceans: The impacts are more pronounced in the tropical oceans due to surface winds that have intensified since the 1900s. Stronger tropical currents could carry more warm water to higher latitudes.
    • Storage of heat: by reaching deep into the ocean, the acceleration could boost the storage of heat in the depths, helping slow the warming on land.
    • Indian Ocean: The Indian Ocean in particular has emerged as the biggest victim of climate change. The sea surface temperature (SST) of the tropical Indian Ocean has risen by an average of 1 degree Celsius from 1951 to 2015 against the global average of about 0.7°C.
    • Effect on corals: corals struggle to survive in such high temperatures.

    Impact of warming seas for species and ecosystems

    Way Forward

    • Scientists could only track the upper 2,000 metres of the ocean: intensive observations that monitor the deep global ocean circulation are urgently needed not only for understanding past conditions but also for reducing uncertainty in future projections of the global ocean circulation.  
    • Establishment of Early Warning System and Inter-Agency Coordination for prediction of heat waves and issuance of alert. 
    • Public Awareness and community outreach to increase public awareness on how to protect against extreme heat through different mediums. 
    • Capacity building and training programme for health care professionals at different levels to recognize and respond to heat wave related illnesses. 
    • Collaboration with non-government organisations (NGOs) and civil society to provide support in distress situations.


    • Maerl beds are accumulations of unattached live and dead coralline algae heavily calcified red seaweeds which form over thousands of years.
    • They occur from the tropics to the poles and from the low intertidal down to 100m depth in the clear water of the Mediterranean.

    The Argo revolution

    • Argo robots have revolutionised human knowledge of the ocean from natural variability to sea level rise.
    • Until the first deployment of Argo floats in 2000, less than 1 percent of the ocean was being monitored routinely.
    • Today, more than 3,000 of these aquatic robots dive and drift through the upper mile of the ocean.

    Source: DTE