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Recent scientific studies have revealed that the Antarctic Circumpolar Current (ACC)—the strongest and most powerful ocean current on Earth—is slowing down due to accelerated melting of Antarctic ice sheets caused by global warming.

What is ACC?

• The ACC flows clockwise around Antarctica and is the only ocean current that connects the Atlantic, Pacific, and Indian Oceans.
• It is five times stronger than the Gulf Stream and over 100 times more powerful than the Amazon River.
• Driven by strong westerly winds, it is the largest wind-driven ocean current and plays a vital role in regulating the Earth’s climate.

Key Functions and Significance

• Climate Regulation: Distributes heat, nutrients, and water across ocean basins.
• Carbon Sink: Aids in oceanic absorption of atmospheric carbon dioxide, mitigating global warming.
• Marine Barrier: Acts as a natural wall preventing invasive species (e.g., bull kelp, mollusks, shrimp) from reaching Antarctica.
• Prevents Warm Water Intrusion: Helps keep warm ocean currents away from the fragile Antarctic ice shelves.

Findings from Recent Research

• A study by the University of Melbourne and NORCE Norwegian Research Centre, published in Environmental Research Letters, warns that the ACC could slow down by 20% by 2050 under high emissions scenarios.
• Researchers used high-resolution ocean and sea ice simulations on Australia’s GADI supercomputer to project these changes.
• The weakening is largely attributed to the freshwater input from melting ice, which alters ocean salinity and disrupts the formation of Antarctic Bottom Water (AABW)—a crucial component of global ocean circulation.

Reasons for ACC Weakening

• Freshwater Dilution: Melting ice reduces salinity, weakening the density-driven AABW circulation.
• Altered Wind Patterns: Climate change may shift westerly wind patterns that drive the ACC.
• Positive Feedback Loop: Reduced sea ice further warms oceans, accelerating ice melt and weakening the current further.

Potential Global Impacts

• Climate Extremes: Disruption in global heat distribution may lead to increased climate variability and extreme weather events.
• Accelerated Global Warming: Slower circulation reduces the ocean’s carbon sequestration capacity.
• Biodiversity Threats: Invasive species could reach Antarctica, disrupting native ecosystems and food chains (e.g., penguins and krill).
• Global Ocean Circulation Impact: AABW weakening may disrupt the thermohaline circulation affecting global ocean systems.