The Southern Ocean is a crucial part of global ocean circulation, affecting Earth's climate. By analyzing data from GLODAP and CARINA databases, researchers identified the most important water masses in the Southern Ocean. They found that Circumpolar Deep Water is the largest, followed by Antarctic Bottom Water and North Atlantic Deep Water. Antarctic Bottom Water is made up of three types, with Weddell Sea Bottom Water being the most common. Circumpolar Deep Water is mostly composed of Antarctic Bottom Water and North Atlantic Deep Water. In the Atlantic sector of the Southern Ocean, Antarctic Bottom Water makes up the majority of the water volume and takes about 250 years to ventilate.