The main difference between the Southern Ocean and other oceans is that it has no fixed boundaries, while the boundaries of other oceans can be clearly delineated. From the south it is bordered by the coast of Antarctica, the northern border runs along the axis of the so-called Antarctic convergence, generally coinciding with the axis of the Antarctic circumpolar current, or the current of the Western winds, encircling Antarctica. This current is constantly changing its position - therefore, the northern border of the Southern Ocean is also shifting. Even within a year, this current often shifts north or south, and the difference in position can reach several hundred kilometers.

There are fewer ice accumulations in the Southern Ocean compared to the Arctic. The Arctic Ocean is surrounded by land, and large accumulations of impenetrable ice are formed in it. This is called increased concentration. Ice in the Southern Ocean - open - grows very well, but just as easily spreads in all directions. Therefore, it is difficult for a modern powerful ice-class vessel to get stuck in the ice of the Southern Ocean, although at times it looks impassable.

The Southern Ocean also has its own circulation features - that is, water movements since Antarctica is in the south. In this case, it works like an ice compressor: water comes to the Antarctic shelf, goes aground to the coast, is cooled by ice, and goes down, and a new one comes in its place. Thus, the water in the ocean is constantly circulating.

But this does not happen in all parts of the ocean - in West Antarctica, due to the features of the seabed topography, a powerful branch leaves the circumpolar current, and this is a very fast and warm stream. Water from it enters the shelf faster and in large quantities, does not have time to cool down and goes back to the ocean uncooled, thus causing the ice shelves to melt.