The southern ocean Antarctica’s northern boundary

Abstract

The Southern Ocean totally surrounds Antarctica and, with its cold waters and partial covering of sea ice, it is the maritime component of greater Antarctica. The range of water temperatures in the Southern Ocean is large. Near Antarctica, water can be colder than −2 °C, while at the ocean’s northern limits temperatures can reach 10 °C or more. In contrast, there is a small change in salinity across the ocean, but the slight changes in temperature and salinity are enough to set up density gradients that, along with the wind, drive the Southern Ocean currents. The dominant current is the eastward flowing Antarctic Circumpolar Current, the world’s largest current, but smaller westward flowing currents fringe the Antarctic continental shelf. Density gradients also drive vertical circulation where cold, salty, dense waters sink around the margins of Antarctica. This dense water then slowly flows north and is found globally at the bottom of the world’s oceans. This process helps to establish the global ocean circulation that transports heat, moisture and dissolved compounds such as carbon dioxide and oxygen over thousands of kilometres. This chapter explores the significance of the Southern Ocean and its role in global ocean transport and circulation, as they contribute to the global climate system.