The Southern Ocean has the earth’s cleanest air

News Excerpt:

The Southern Ocean is renowned for having the cleanest air on Earth. But the precise reasons why have remained a mystery, until now.

About Southern Ocean:

  • The Southern Ocean (also known as the Antarctic Ocean) is one of the five great ocean basins on Earth.
    •  It was formed around 34 million years ago when Antarctica and South America drifted apart, creating the Drake Passage.
    •  This makes it the youngest ocean basin on Earth
  • Today, it is the only ocean that flows around the globe uninterrupted by land, encircling Antarctica like a moat.
  • Around the northern limit of the Southern Ocean there is a natural, biological boundary called the Antarctic Convergence, or Polar Front. 
    • North of the convergence, the water temperature near the surface sits at around 42.1°F (5.6 °C), ideal for marine species adapted to the subantarctic climate.
    • South of the convergence, the water temperature drops dramatically to below 36 °F (2 °C), creating the perfect conditions for uniquely Antarctic wildlife to flourish.
  • As the primary mixing zone between the world’s major oceans, the Southern Ocean plays an important role in the circulation of water around the globe. 
    • It also plays a key role in regulating the earth’s climate through its currents, seasonal sea ice and by absorbing heat and carbon dioxide from the atmosphere.
  • The Southern Ocean is known for its strong winds, intense storms, dramatic seasonal changes and cold temperatures. 
    • Each of these factors plays a role in the many important processes that occur in this part of the ocean, and help regulate the global climate.
  • The Southern Ocean is dominated by the Antarctic Circumpolar Current (ACC): the longest, strongest, deepest-reaching current on earth. 
    • The ACC circulates clockwise around the continent, carrying more water around the globe than any other current.
  • Powerful currents, cold temperatures and nutrient and oxygen-rich waters make the Southern Ocean one of the most productive marine ecosystems on Earth
    • In summer billions of microscopic algae (phytoplankton) proliferate, spreading into blooms large enough to be seen from space.

What are the factors contributing to the clean air over the Southern Ocean?

  • The region experiences minimal human activity compared to other parts of the world, resulting in fewer industrial emissions and less burning of fossil fuels.
  • Aerosol levels are influenced by seasonal variations, such as the amount of salt spray and the growth of phytoplankton, which are a source of airborne sulfate particles. 
    • The Southern Ocean experiences fewer sulfates during winter, contributing to pristine air conditions.
  • Distinctive honeycomb-shaped cloud patterns(Open and closed Honeycomb cells) in the region influence the amount and distribution of rainfall. 
  • Clouds and rain play a crucial role in scrubbing the atmosphere clean. 
    • Research indicates that open honeycomb-shaped clouds, which are prevalent in the Southern Ocean
    • It generates intense rain showers that effectively wash aerosol particles out of the air. 
    • Rain scrubs the aerosols out of the sky in much the same way as a washing machine acts to clean clothes.
  • Moreover, the study revealed that these open honeycomb clouds are more prevalent during the winter months, coinciding with the period when the Southern Ocean's air is at its cleanest.
  • Large-scale weather systems, including storms, control the pattern of the cloud field over the Southern Ocean. 
    • These weather systems produce open and closed honeycomb cells, which further affect rainfall and aerosol levels.

About Honeycomb cloud:

  • Easily spotted by their honeycomb shape, open-cell clouds are one of the most common cloud formations.
  • It is found on the backside of low pressure systems skirting the edges of every continent. 
    • Yet for all their ubiquity, they are among the more mysterious cloud formations known,
  • Scientists call the honeycomb-patterned clouds "open-cell clouds"; they are low, flat clouds that, to someone peering down from an airplane, resemble a quilt. 
    • The quilt patches are spaces of open air framed by walls of clouds.
  • The honeycomb is created by a simple form of convection, air movement caused by warm air rising and cold air falling (the same phenomenon that happens in a pot of boiling water.


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