The name the Southern Ocean is a somewhat controversial name that is not universally recognized for the body of water that encircles Antarctica. Unlike the other oceans, the boundary of the Southern Ocean is defined by currents rather than land masses.
Its northern boundary fluctuates with the position of the Antarctic Convergence, an ocean zone where the northward moving waters of the Antarctic mix with sub-Antarctic waters. The Antarctic Convergence prevents the waters of the Southern Ocean from flowing further northward, and as a result, they move as the Antarctic Circumpolar Current from west to east around the continent. The Antarctic Convergence is approximately located at 60 degrees south latitude. Therefore, the Southern Ocean is located between the Antarctic continent and 60 degrees south latitude, through 360 degrees of longitude.
The water temperature ranges from 10 degrees Celsius to -2 degrees Celsius. The surface freezes seasonally to between 55 and 65 degrees south latitude. The icepack fluctuates seasonally between 2.6 million square kilometers to 18.8 million kilometers. Icebergs are common year round and can be quite large. High winds and waves make portions of the ocean very dangerous for ships; however, they also keep some areas ice-free year round.
The Southern Ocean does not have a large continental shelf as other oceans do. It is primarily deep water, between 4,000 and 5,000 meters deep. The deepest point is 7,235 meters below sea level and is located at the southern end of the South Sandwich Trench. The continental shelf that does exist is narrow and 400 to 800 meters deep. In contrast, the continental shelf averages 133 meters.
Natural resources found in the Southern Ocean include oil and gas, manganese nodules, sand and gravel. Icebergs are a source of fresh water. Fish, whales, squid and seals have been economically important biological resources. International whaling, fishing and seal harvest treaties have limited or eliminated the economic importance of some species.
The Southern Ocean is an ecosystem unto itself. It contains some of the most biologically productive water on the planet. The waters of the Southern Ocean are nutrient dense. They are able to support a large plankton population, which in turn is the base of a large ecosystem that supports animals, including krill, fish, squid, whales, seals.
The phytoplankton that are at the base of the ecosystem drive a carbon biological pump. They take up nutrients and carbon at the ocean surface. As they die, billions of tons of carbon sink into the deep ocean. The biological matter rots and the carbon gets turned into carbon dioxide and gets sequestered at the bottom of the ocean. Thus, the Southern Ocean plays a large role in controlling the carbon dioxide levels of the earth’s atmosphere.
References:
United States Central Intelligence Agency, The World Factbook, Southern Ocean, www.cia.gov/library/publications/the-world-factbook/geos/oo.html
NOAA, Geophysical Fluid Dynamics Laboraty – The Southern Ocean Biogeochemical Divide, www.gfdl.noaa.gov/southern-ocean-biogeochemical-divide
NOAA News Online (Story 2653), NOAA Scientists Demonstrate Southern Ocean Divide, www.noaanews.noaa.gov/sotries2006/s2653.htm
Wikipedia, the free encyclopedia, Southern Ocean, http://en.wikipedia.org/wiki/Southern_Ocean
