Antarctic Circumpolar Current (ACC) 

• Antarctic Circumpolar Current (ACC) is the strongest and the largest wind-driven current on Earth and moves clockwise around Antarctica, driven by strong westerly winds.
• It is the only current that goes all the way around the planet and connects the Atlantic, Pacific, and Indian Oceans.
• Significance: 
  • It’s a type of cold current that acts as a barrier and prevents warmer waters from reaching Antarctica.
  • Significantly influences uptake of heat and carbon dioxide in the ocean.
  • Blocks invasive species (e.g., bull kelp, shrimp, mollusks) from other continents reaching Antarctica.

Reasons for the weakening of ACC

• Changes in Ocean Salinity: Due to accelerated melting of ice shelves (from global warming) around Antarctica has resulted in weakening of Antarctic Bottom Water (AABW).
  • AABW is a sinking process and a critical component of global ocean circulation tied to circulation of ACC.
• Changes in Wind Patterns: Climate change can alter pattern of westerly winds in Southern Hemisphere.
• Positive Feedback Loop: Reduced sea ice can exacerbate warming & freshwater input, creating a feedback loop that further weakens ACC.

Functions of ACC

• Climate regulation: The ACC helps distribute heat around the planet by moving warm water from the equator towards the poles and cold water towards the equator.
• Carbon sequestration: The ACC absorbs significant amounts of carbon dioxide from the atmosphere, transporting it deep into the ocean where it can be stored for centuries.
• Nutrient distribution: By stirring up water from different depths (upwelling), the ACC brings nutrients from the deep to the surface, supporting marine ecosystems around Antarctica and beyond.
• Isolates Antarctica continent: It minimizes the flux of surface subtropical heat into the polar oceans, thus thermally isolating Antarctica.
• It serves as the northern boundary to the polar seas, containing the fresh, cold, stable surface waters necessary for sea ice formation and limiting the northern extent of the seasonal sea ice fields.