雅思听力材料：南大洋(BBC纪录片)

　　Southern Ocean

　　The Southern Ocean comprises the southernmost waters of the World Ocean, generally taken to be south of 60S latitude and encircling Antarctica. As such, it is regarded as the fourth-largest of the five principal oceanic divisions . This ocean zone is where cold, northward flowing waters from the Antarctic mix with warmer subantarctic waters.

　　Geographers disagree on the Southern Oceans northern boundary or even its existence, with many considering the waters part of the Pacific, Atlantic, and Indian Oceans instead. Others regard the Antarctic Convergence, an ocean zone which fluctuates seasonally, as separating the Southern Ocean from other oceans, rather than the 60th parallel. Australian authorities regard the Southern Ocean as lying immediately south of Australia.

　　The International Hydrographic Organization has not yet ratified its 2000 definition of the ocean as being south of 60S. Its latest published definition of oceans dates from 1953; this does not include the Southern Ocean. However, the more recent definition is used by the IHO and others.