The Drake Passage is the roughly 500 mile gap between Cape Horn and Antarctica’s South Shetland Islands, including Livingston and Snow Islands, linking the southwest Atlantic through the Scotia Sea to the southeast Pacific. Spanish sources call it the Mar de Hoces after Francisco de Hoces, who was blown south from the Strait of Magellan around 1525 before he and his crew vanished. In 1578 a tempest scattered Francis Drake’s fleet as it entered the Pacific: the Marigold was lost, another ship fled home, and the Golden Hind was driven south into open water. Willem Schouten sailed through on purpose in 1616, yet for centuries many sailors preferred the narrow Strait of Magellan or the Beagle Channel.

Somewhere between 49 and 17 million years ago Antarctica tore away from South America, opening a path for the Antarctic Circumpolar Current, which cut the continent off from warm water and likely drove ice sheet growth and Eocene cooling. Pushed by the Roaring Forties and Furious Fifties, the current moves 100 to 150 sverdrups, and tracking shows about 23 sverdrups carried north to the equator, against about 33 for the Gulf Stream. Models that close the passage shut down the North Atlantic deep water cell. Over the Shackleton Fracture Zone, lee waves break and mix deep water about 20 times more strongly than in the Pacific sector, dissipating around 20 percent of the wind energy put into the Southern Ocean.

• One sverdrup is one million cubic meters of water moving per second.
• Mixing in most of the open ocean is about ten times too weak to sustain the global circulation.
• The current pinches off cold-core cyclonic rings that wander away from the main flow.
• Upwelled nutrients feed wandering, black-browed, and light-mantled albatrosses, giant petrels, and hourglass dolphins.
• Cuvier’s and Arnoux’s beaked whales hunt in the turbulent water above the fracture zone.