Antarctic Polar Front (Antarctic Convergence)

node · earth · Southern Ocean - circumpolar

The circumpolar boundary where cold Antarctic surface water flowing north meets and sinks beneath warmer sub-Antarctic water. It is a sharp front, often crossed in a matter of hours by ship, with a surface temperature step of several degrees. It functions as a biological wall as much as a physical one: the species assemblage on either side differs profoundly, and Antarctic krill is essentially confined to the cold side of it. Its position wanders with longitude and season, running roughly between 50 and 60 degrees south, and it is the reason the Southern Ocean can be defined biologically rather than by an arbitrary line of latitude. It is also a large part of the answer to why nothing walked back into Antarctica: the isolation is oceanographic before it is geographic.