Coursing at its centre is the powerful Antarctic Circumpolar Current, a gigantic aquatic conveyor belt 200 to 1,000 kilometres (125 to 625 miles) wide and 24,000 kilometres (15,000 miles) long, which flows from west to east around the icy continent.

During its journey around Antarctica, which takes three years to complete, the world's strongest ocean current serves as an interchange between the waters of the Pacific, Atlantic and Indian Ocean basins.

Covering 20.3 million square kilometres (8.12 million square miles) and bordered by nearly 18,000 kilometers (11,000 miles) of coastline, the Southern Ocean is slightly more than twice the size of the United States and is the fourth largest of the earth's five oceans. The Arctic Ocean, with the North Pole at its centre, is just 1.5 times the size of the US.

The relatively "young" body of water surrounding the world's southernmost continent was created when the landmasses of Antarctica and South America broke apart -- the final stage of the disintegration of the ancient southern super-continent Gondwana, from which Africa, Australia and the Indian subcontinent were also born.

Devoid of islands or anything else that could offer resistance to the wind, howling gales race across the ocean's surface at average speeds of 90 to 100 kilometres (55 to 60 miles) per hour. The fiercest gusts reach nearly double that speed.

"That explains the impressive sound effects these winds create and why sailors call them the Roaring Forties and Furious Fifties," French meteorologist Patrick Calois told AFP recently.

The absence of landmasses in the ocean also leads to gigantic waves more than 30 metres high. These "rogue waves" struck terror into the hearts of 19th-century navigators and ensure that sea voyages to Antarctica's isolated scientific research stations remain perilous to this day.

Equally perilous for the rare ships able to make the trip are the treacherous icebergs sliding silently through its waters.

Then there is the cold.

The ocean is bitterly frigid -- between 10 and minus two degrees Celsius (50 and 28 degrees Fahrenheit) -- and temperamental. At any moment the temperature may change abruptly because of collisions between currents that vary in iciness, salinity and concentration of nutrients.

The presence of nutrients means the Southern Ocean is a rich and diverse aquatic world of crustaceans and endemic fish, not to mention penguins, whales and seals.

It also explains why commercial fishing and whaling ships have been lured for centuries to its dangerous seas.

"Near the Antarctic continent, the waters are very rich," explained marine ecologist Philippe Koubbi, who is conducting research here at the French scientific base of Dumont d'Urville.

"At the bottom of the ocean, 90 percent of the fish are endemic," that is exclusive to this habitat, he said.

earlier related report
Collapse Of Two Iceshelves Exposes Seabed Beauty Off Antarctica
The collapse of two ice shelves in Antarctica has exposed an exquisite seabed ecosystem, including species of crustaceans and marine anemones that had never been identified, researchers said on Sunday. The insight into Antarctica's hidden marine world came from the breakup of the Larsen A and B ice shelves, 12 and five years ago respectively, that later formed huge icebergs. Their collapse laid bare a 10,000-square-kilometer (3,800-square-mile) portion of the sea bed -- an area almost the size of Jamaica -- that had been roofed by ice for millennia.

Part of the area was explored by an unmanned robot, lowered from a German research vessel, the Polarstern (North Star), in a 10-week international expedition that ended on January 30.

"The breakup of these ice shelves opened up huge, near pristine portions of the ocean floor, sealed off from above for at least 5,000 years, and possibly up to 12,000 years in the case of Larsen B," said Julian Gutt, the expedition's chief scientist.

"(...) Until now, scientists have glimpsed life under Antarctica's ice shelves only through drill holes. We were in the unique position to sample wherever we wanted in a marine ecosystem considered one of the least disturbed by humankind anywhere on the planet."

The team of 52 scientists from 14 countries collected around 1,000 species, some of which are believed to be new to science, and took what they describe as "brilliant" images of unfamiliar creatures.

The newcomers to the book of knowledge about Antarctica include 15 shrimp-like crustaceans called amphipods, including one beast that was nearly 10 centimetres (four inches) long, the researchers said in a press release.

Four presumed new species of cnidarians -- organisms related to coral, jellyfish and sea anemones -- were also found.

One of them lives on the back of a snail, showing a symbiotic relationship in which the snail provides locomotion for the cnidarian, and the cnidarian provides protection for the snail.

At present, international databases have recorded 5,957 forms of marine life, but as many as 11,000 more remain to be discovered.

The researchers discovered the ice shelf had covered a highly varied sea floor, ranging from bedrock to pure mud, with flora and fauna that were correspondingly diversified.

In shallower waters to depths of about 220 metres (715 feet), they came across rich patches of deep sea lilies, sea cucumbers and urchins -- an intriguing find, as these species usually lurk in deep water of around 2,000 metres (6,500 feet).

Ice shelves in Antarctica are caused by glaciers that reach the coast and then creep out to sea, floating on the water but still attached to land.

In 1992, the so-called Larsen A ice shelf disintegrated, and in 2002, the Larsen B followed suit, creating the most massive icebergs ever seen.

The loss of the shelves is giving Antarctica-watchers the chance to see how different species move in to colonise the freshly uncovered seabed, starting with opportunistic gelatinous creatures called sea squirts and glass sponges. Mammals, too, have moved in.

"It was surprising how fast such a new habitat was used and colonised by Minke whales in considerable densities," said German specialist Meike Scheidat.

"They indicate that the ecosystem in the water column changed considerably."

The newly-opened vista also provides a barometer for change, for parts of the Antarctic coast are being hit by global warming at a far greater rate than other parts of the world. Local temperatures at the Larsen shelves have risen by 2.5 C (4.5 F) since the 1940s.

"This is virgin geography," said Gauthier Chapelle, a biologist at the Brussels-based International Polar Foundation.

"If we don't find out what this area is like now following the collapse of the ice shelf, and what species are there, we won't have any basis to know in 20 years' time what has changed and how global warming has altered the marine ecosystem."

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