Deep Waters Spiral Around Antarctica

SCIENCE

Teachers, scroll down for a quick list of key resources in our Teachers Toolkit.

Discussion Ideas

New research examines the geography of the “large, deep currents in the Pacific, Atlantic, and Indian oceans” as they flow southward and converge around Antarctica. What is the name of these currents? Read through our short reference resource on the “ocean conveyor belt” for some help.
- Collectively, the currents are known as the mighty Antarctic Circumpolar Current (ACC), the world’s most powerful surface ocean current, which rotates clockwise around the continent of Antarctica. The ACC is not only the world’s strongest current, but also the only major current that circles the globe unimpeded by continents.
- The ACC moves a lot of water very quickly—about 140 million cubic meters (4.9 billion cubic feet) of water per second.

Why is the ACC important to life on Earth? Use our video study guide on ocean currents and climate for some help.
- The twin processes of overturning and upwelling bring cold, nutrient-rich water toward the surface (a region known as the “mixed layer”). The mixed layer is “fundamentally important for oceanic uptake of carbon and heat, nutrient resupply for sustaining oceanic biological production, and the melt rate of ice shelves.” In other words, the ACC helps regulate climate and food webs around the world. Ho hum.

In the newest study, researchers were able to model and track millions of particles as they circled around Antarctica. What did modeling the ACC help them learn?
- The current corkscrews. “[D]eep, relatively-warm water from the three ocean basins enters the Southern Ocean and spirals southeastwards and upwards around Antarctica before reaching the ocean’s mixed layer, where it interacts with the atmosphere.”
- Eddies contribute to the patterns of the current. The topography of five locations (the Southwest Indian Ridge, the Kerguelen Plateau, the Macquarie Ridge, the Pacific-Antarctic Ridge, and the Drake Passage) create regions with turbulence and high kinetic energy, which help to overturn and upwell the majority of the water.
- The Atlantic supplies half the water to the ACC. Researchers were able to map the contributions of each ocean basin to the current. The Atlantic basin contributed about half the water that reached the mixed layer. The Pacific and Indian ocean basins each contributed about a quarter.
- The current is fast. The ACC exhibited much, much faster vertical circulation than previously thought. Cold, nutrient-rich waters reached the mixed level after about 29-81 years. Previous, non-eddying models had estimated the time to be between 150-250 years.