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Biodiversity & Environment

Climate Change Alters Ocean Colour

  • 17 Jul 2023
  • 6 min read

For Prelims: Climate Change, Marine Ecosystem, Global Warming

For Mains: India's climate change mitigation initiatives, climate change impact on oceans

Source: DTE

Why in News?

Recently, a new study reveals that 56% of the world's oceans have experienced a change in colour due to climate change.

  • Tropical waters, particularly the southern Indian Ocean, have turned green, indicating an increase in phytoplankton and marine life.

What are the Key Highlights of the Study?

  • Long-Term Trends and Data Analysis:
    • Aqua Satellite Data:
      • Researchers analyzed data from the Moderate Resolution Imaging Spectroradiometer (MODIS) on the Aqua satellite (NASA’s Earth Science satellite mission), monitoring ocean colour for two decades (2002-2022).
      • MODIS takes measurements in seven visible wavelengths (Light of different wavelengths produces different perceptions of colour).
    • Subtle Colour Changes:
      • Human eyes cannot detect subtle colour changes in the oceans, which may contain a mix of wavelengths ranging from blue to green and even red.
    • Green Waters and Phytoplankton:
      • The study finds that green-coloured water indicates the presence of phytoplankton, essential microscopic plant-like organisms.
        • Phytoplankton serve as the base of the marine food web, similar to plants on land, and play a crucial role in supporting marine life.
      • The colour of the ocean affects the amount of carbon dioxide absorbed by the oceans, with current estimates indicating that oceans absorb 25% of global CO2 emissions.
    • Role of Climate Change:
      • By comparing annual variations in ocean colour over the two decades, the study identified climate change as the primary factor behind the observed changes.
      • Using a model, researchers simulated two scenarios—one considering greenhouse gas emissions and the other without them.
      • The scenario accounting for greenhouse gas emissions predicted that colour changes could occur in approximately 50% of the world's surface oceans, aligning with satellite observations indicating a 56% shift to green or blue waters.
    • Implications for Marine Life and Conservation:
      • Impact on Organisms:
        • The green hue comes from chlorophyll, a pigment that helps phytoplankton make food. A change in colour due to an increase or decline in the population will impact organisms that feed on plankton.
      • Carbon Sequestration:
        • Different types of plankton have varying abilities to absorb carbon, potentially influencing the ocean's capacity for carbon uptake.
    • Regional Variability and the Need for Further Study:
      • The southern Indian Ocean exhibits significant changes in colour, while waters near India do not follow the same trend, potentially due to natural variability.
  • Recommendations:
    • Researchers emphasize the need for individuals and policymakers to recognize the significance of these changes and take appropriate action to protect marine ecosystems.
    • Ongoing monitoring and further research are crucial to understanding regional variations and the full extent of climate change's impact on ocean colour.

What are India's Climate Change Mitigation Initiatives?

UPSC Civil Services Examination, Previous Year Questions (PYQs)

Q. What are the consequences of spreading ‘Dead Zones’ on marine ecosystems? (2018)

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