Antarctic Circumpolar Current (ACC) is Slowing Down Rapidly

Syllabus: GS1/Geography

Context

• Scientists warn that the Antarctic Circumpolar Current (ACC) could slow by about 20% by 2050 under a high carbon emissions scenario.

About

• ACC is the world’s strongest ocean current. 
  • It’s five times stronger than the Gulf Stream and more than 100 times stronger than the Amazon River.
  • It forms part of the global ocean “conveyor belt” connecting the Pacific, Atlantic and Indian oceans. 
• ACC’s Role: ACC moves clockwise around Antarctica and regulates global climate by influencing the ocean’s ability to absorb heat and CO2 and preventing warm waters from reaching Antarctica.
  • The system regulates Earth’s climate and pumps water, heat and nutrients around the globe.

Impacts of Slowing down of ACC

• Impact on Climate and Carbon Absorption: If the ACC breaks down, it could lead to more climate variability, extreme weather in certain regions, and accelerated global warming due to reduced carbon absorption by the ocean.
• Threat to Antarctic Ecosystem: Slowing of the ACC could allow invasive species (e.g., southern bull kelp, shrimp, mollusks) to reach Antarctica, disrupting the local food web and affecting native species like penguins.
• Impact of Melting Ice Sheets: Melting ice shelves add fresh water to the ocean, altering its salinity, weakening the Antarctic Bottom Water formation, and reducing the strength of the ocean jet around Antarctica.

Ocean Currents

• Ocean currents are the continuous, predictable, directional movement of seawater driven by gravity, wind (Coriolis Effect), and water density. 
• Ocean water moves in two directions: horizontally and vertically.
  • Horizontal movements are referred to as currents, while vertical changes are called upwellings or downwellings.
• The system is responsible for the transfer of heat, variations in biodiversity, and Earth’s climate system.

Ocean Conveyor Belt

• The ocean conveyor belt, also known as the global thermohaline circulation (THC), is a large-scale ocean current system that moves water throughout the world’s oceans.
  • The path starts in the North Atlantic, where cold water sinks, creating a flow of deep water that moves southward.
  • It travels through the Southern Ocean, moves into the Indian and Pacific Oceans, and finally upwells in the Pacific and Indian Oceans, where the surface water returns toward the equator.

• This system plays a crucial role in regulating Earth’s climate by redistributing heat, nutrients, and gases like carbon dioxide.

Role of Ocean Currents

• Climate Regulation: Transport heat from the equator to the poles and vice versa, helping to stabilize global temperatures.
• Supporting Marine Life: Distribute nutrients that support the growth of phytoplankton, forming the base of the ocean’s food chain.
• Influencing Weather Patterns: Affect weather systems and phenomena like El Niño and La Niña, influencing rainfall and storm activity.
• Carbon Sequestration: Help absorb and store carbon dioxide from the atmosphere, acting as a carbon sink.
• Fisheries and Economy: Influence fish distribution, affecting global fisheries, and provide efficient shipping routes.
• Ocean Mixing: Aid in mixing surface and deep ocean waters, regulating temperature, salinity, and oxygen levels.
• Sea Level and Coastal Erosion: Impact sea levels and contribute to coastal erosion through water movement.

Conclusion

• While our findings present a bleak prognosis for the Antarctic Circumpolar Current, the future is not predetermined. 
• Concerted efforts to reduce greenhouse gas emissions could still limit melting around Antarctica.
• Establishing long-term studies in the Southern Ocean will be crucial for monitoring these changes accurately.

Source: ET