Southern Ocean: Earth’s Climate Buffer

Why in News ?

Recent scientific studies have highlighted that the Southern Ocean absorbs a significant share of carbon dioxide released by human activities, thereby mitigating global surface warming and playing a crucial role in regulating Earth’s climate system.

Background & Context

Global warming driven by rising greenhouse gas emissions has intensified research on natural climate regulators, particularly oceans. While oceans collectively absorb over 90% of excess heat and about one-fourth of anthropogenic CO₂, the Southern Ocean’s contribution is disproportionately large compared to its surface area. Its unique circulation patterns, cold waters, and interaction with the atmosphere make it a critical carbon and heat sink, slowing the pace of global temperature rise.

Southern Ocean: Key Facts

Location and Extent

• Also known as the Antarctic Ocean
• Fourth-largest ocean by surface area
• Defined by the International Hydrographic Organization (IHO) as the southernmost part of the World Ocean
• Encircles Antarctica
• Connects the Pacific, Atlantic, and Indian Oceans

Physical Characteristics

• Characterised by:
  • Strong westerly winds
  • Intense storms
  • Extreme cold temperatures
  • Pronounced seasonal variations
• Dominated by the Antarctic Circumpolar Current (ACC):
  • Longest, strongest, and deepest-reaching ocean current on Earth
  • Flows uninterrupted around Antarctica

Geological Formation

• Formed when Antarctica and South America drifted apart
• Creation of the Drake Passage enabled the development of the ACC
• This isolation cooled Antarctica and influenced global ocean circulation

Biodiversity and Productivity

• Cold, oxygen-rich, and nutrient-dense waters
• Supports:
  • Krill
  • Whales
  • Seals
  • Penguins
• One of the most productive marine ecosystems globally, despite extreme conditions

Role of the Southern Ocean in the Global Climate System

Carbon Sink Function

• Absorbs a large proportion of anthropogenic CO₂
• Cold waters enhance gas solubility, increasing carbon uptake
• Helps slow atmospheric accumulation of greenhouse gases

Heat Regulation

• Takes up vast amounts of excess heat generated by global warming
• Delays surface warming, acting as a thermal buffer

Ocean Circulation

• Drives global thermohaline circulation
• Connects major ocean basins, redistributing heat, salt, and nutrients worldwide

Sea Ice Dynamics

• Seasonal formation and melting of sea ice:
  • Influences albedo (reflection of solar radiation)
  • Regulates ocean-atmosphere heat exchange
  • Impacts global weather and climate patterns

Emerging Concerns

• Warming may reduce the ocean’s carbon absorption capacity
• Changes in wind patterns could alter the Antarctic Circumpolar Current
• Ocean acidification threatens marine biodiversity
• Potential feedback loops could accelerate climate change

Significance for India and the World

• Slowing global warming benefits climate-vulnerable countries, including India
• Impacts:
  • Monsoon systems
  • Sea-level rise
  • Extreme weather events
• Reinforces the need for:
  • Global climate cooperation
  • Protection of polar and ocean ecosystems