Ocean Warming

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Why in news?

The average global sea surface temperature (SST) for February 2024 stood at 21.06 degree Celsius. This is the highest recorded temperature in a dataset that goes back to 1979. The previous record of 20.98 degree Celsius was set in August 2023.

What’s in today’s article?

  • Why in news?
  • Why are the oceans getting warmer?
  • Why are rising sea surface temperatures a cause of worry?
  • Conclusion

Why are the oceans getting warmer?

  • Greenhouse Gas(GHG) Emissions
    • Since the Industrial Revolution, human activities such as burning fossil fuels have released high levels of GHGs in the atmosphere.
    • Carbon dioxide, methane, ozone, and nitrous oxide are some of the notable GHGs, which essentially trap heat in the atmosphere and contribute to global warming.
    • As a result, the average global temperature has risen at least 1.2 degree Celsius above pre-industrial times.
  • Heat Absorption
    • Almost 90 per cent of the extra heat trapped by GHGs has been absorbed by the oceans, making them steadily warmer over the decades.
  • Deforestation
    • Deforestation reduces the number of trees available to absorb CO2 from the atmosphere. This leads to higher concentrations of GHGs, contributing to global warming and consequently, ocean warming.
  • Melting Ice
    • As global temperatures rise, polar ice caps and glaciers melt, adding freshwater to the oceans.
    • This influx of freshwater can disrupt ocean currents and contribute to changes in temperature and salinity, further affecting ocean warming.
  • Impact of El Niño
    • El Niño is a weather pattern that refers to an abnormal warming of surface waters in the equatorial Pacific Ocean.
    • It has contributed to both ocean warming and rising global surface temperatures.
  • Less dust blowing off the Sahara Desert recently due to weaker-than-average winds.
    • Typically, the dust forms a giant umbrella that shades the Atlantic water and reduces ocean temperatures.
    • But now, the umbrella has partially folded and more of the Sun is beating down on the ocean.
  • Natural Variability
    • While human activities are the primary driver of recent ocean warming, natural factors such as volcanic eruptions, changes in solar radiation, and ocean currents also play a role in short-term variations in ocean temperature.

Why are rising sea surface temperatures a cause of worry?

  • Irreversible consequences for marine ecosystems
    • Warmer oceans lead to increased ocean stratification, where water separates into layers based on density.
    • Warmer, lighter, less salty, and nutrient-poor water sits atop colder, saltier, and nutrient-rich water.
    • Normally, ocean processes like currents, wind, and tides mix these layers, but stratification disrupts this.
  • Threat to marine life
    • The rise in temperatures, however, has made it harder for water layers to mix with each other.
    • Due to this, oxygen absorbed isn’t able to mix properly with cooler ocean waters below, threatening the survival of marine life.
  • Impact on Phytoplankton
    • Nutrients are also not able to travel up to the surface of the oceans from below. This could threaten the population of phytoplankton.
      • Phytoplanktons are single-celled plants that thrive on the ocean surface and are the base of several marine food webs.
      • Phytoplanktons are eaten by zooplankton, which are consumed by other marine animals such as crabs, fish, and sea stars.
    • Therefore, if the phytoplankton population plummets, there could be a collapse of marine ecosystems.
  • Coral Bleaching
    • Corals are highly sensitive to changes in SSTs. When waters become too warm, corals expel the algae living in their tissues, causing them to turn white or bleach.
    • Bleached corals are stressed and more susceptible to disease and death.
  • Ocean Acidification
    • Warmer SSTs can exacerbate ocean acidification, a process driven by the absorption of CO2 from the atmosphere.
    • Increased CO2 levels lower the pH of seawater, making it more acidic.
    • This acidification can harm marine organisms with calcium carbonate shells or skeletons, such as shellfish, corals, and some planktonic species, impacting entire marine food webs.
  • Extreme Weather Events
    • Warm ocean waters provide the energy needed to fuel tropical storms and hurricanes.
    • Rising SSTs can lead to more intense storms, with higher wind speeds & heavier rainfall posing risks to coastal communities, infrastructure, and economies.
  • Sea Level Rise
    • Warm water expands, contributing to thermal expansion of the oceans, which is a significant driver of global sea level rise.
    • Threatening coastal communities with more frequent and severe flooding, erosion, and saltwater intrusion into freshwater sources.
  • Impacts on Climate Patterns
    • Changes in SSTs can influence atmospheric circulation patterns, such as the formation of weather systems like El Niño and La Niña.
    • These climate phenomena can have widespread effects on weather patterns, precipitation, and temperature extremes around the globe, affecting agriculture, water resources, and ecosystems.

Conclusion

Addressing the root causes of rising SSTs, primarily anthropogenic greenhouse gas emissions, is crucial to mitigating these impacts and protecting both marine and human well-being.


Q1) What are Phytoplankton?

Phytoplankton are microscopic, single-celled organisms that live in water and perform photosynthesis. They are a key part of ocean and freshwater ecosystems.

Q2) What is Sahara Desert?

The Sahara Desert is the world's largest hot desert, covering 9,200,000 square kilometers across North Africa. It's the third-largest desert overall, after Antarctica and the Arctic.