What is the densest ocean water mass, formed primarily in Antarctica's Weddell Sea during Southern Hemisphere winters?

• A. Antarctic Bottom Water
• B. North Atlantic Deep Water
• C. Pacific Surface Water
• D. Indian Ocean Water

Answer: (A)

Density increases when seawater becomes very cold and salty, so it sinks. In the Weddell Sea during Antarctic winter, sea-ice formation rejects salt into the surrounding water while the temperature drops, making the water extremely dense. This dense water plunges to the deep ocean and spreads along the sea floor as Antarctic Bottom Water, the deepest and most dense water mass in the world. Other options describe waters formed in different regions or at the surface, which are not the ultra-dense bottom water that forms in the Weddell Sea.