Which border is the Southern Ocean?

The Southern Ocean doesn't have a traditional border like other oceans. It's defined by the Antarctic Convergence, which is a zone where cold, northward-flowing Antarctic waters meet warmer subantarctic waters.

This convergence isn't a fixed line but rather a dynamic boundary that fluctuates with the seasons. However, it generally circles Antarctica, roughly at 60° South latitude.

So, you could say that the Southern Ocean's border is the Antarctic Convergence zone, which runs around the entire continent.