The Southern Ocean and global climate
Glossary
chlorofluorocarbons (CFCs). Organic compounds made up of atoms of chlorine, fluorine and carbon. They were commonly used as refrigerants in refrigerators and air conditioners, as blowing agents in foam plastics, and as cleaners for computer circuit boards. CFCs do not occur naturally – their increase in the atmosphere is entirely the result of human activity. Beginning in the 1940s there was a rapid increase in the rate of manufacture, and hence the escape, of CFCs.
Antarctic Bottom Water and Antarctic Intermediate Water. Water does not have the same composition throughout the ocean. The different masses of water can be described by their chemical and physical properties – temperature and salinity are used most frequently. These two properties affect the density of water.
Antarctic Bottom Water forms close to Antarctica and is the most dense of the water masses. (Its high density is a result of its coldness and high levels of salinity.) It flows northwards from Antarctica under other water masses, hugging the sea floor.
Antarctic Intermediate Water also forms in the Antarctic region then sinks and spreads northwards. Antarctic Intermediate Water is less saline than Antarctic Bottom Water because it receives fresh water from melting ice shelves and glaciers.
More information about Antarctic water masses can be found at Antarctic circumpolar current (Tasmanian Parks and Wildlife Service).
micronutrient. A chemical element that is essential for plants to grow and reproduce but is only needed in very small amounts. There are seven micronutrients: iron, chlorine, copper, manganese, zinc, molybdenum, and boron.
sea-ice. The sea around Antarctica begins to freeze in March and the area covered by floating sea-ice increases until September or October when it reaches a maximum of about 19 million square kilometres. This sea-ice 'blanket' affects sea temperatures and sea currents by shielding the ocean surface from the strong winds that blow in the high latitudes. Sea-ice is also important because it is white and reflects back to space most of the sun's radiation that falls on it. The presence of more sea-ice cools the earth. For more information see Sea ice (National Snow and Ice Data Center, USA).
transect. An imaginary line drawn through an area in order to help scientists sample and monitor organisms or conditions along the line. The results obtained from samples along the line give an indication of the organisms or conditions in the entire area.
Posted February 1998.