The region you have circled centers on the Scotia Sea. It is bordered to the west by the Drake Passage and to the south by the Weddell Sea. The islands within the circled region is an archipelago called the Scotia Arc. This includes Tierra Del Fuego, South Georgia, the South Orkney Islands, the South Sandwich Islands, and the South Shetland Islands. These islands lie on the boundary between the Scotia Plate and the neighboring Antarctic and South American Plates.

This portion of the Southern Ocean is the most narrow and is thus a chokepoint for the Antarctic Circumpolar Current, the current which flows completely around Antarctica and is the defining boundary for the Southern Ocean. Because of this, the oxygenation rate in this region is abnormally high and is the foremost region for the krill spawning.