FACTBOX: Antarctica under the microscope

(Reuters) - Scientists are stepping up their study of Antarctica and its wildlife for possible early warnings about how climate change may disrupt life around the planet in coming decades.

Here are some details about the vast ice sheet known as Antarctica:

GEOGRAPHY: Antarctica, the fifth biggest continent, is for the most part a vast, icy emptiness, some 14.2 million square km (5.5 million square miles) almost completely covered by an ice sheet more than 2,000 meters thick on average.

-- About 2,200 meters (7,200 feet) above sea level, Antarctica is the world's highest continent.

-- The United States has a large base and airstrip at the South Pole, named the Amundsen-Scott Base after two of the most important early 20th-century explorers who helped bring world attention to the continent.

-- It was first sighted in 1820.

* ICE EVERYWHERE:

-- Only about two percent of the land mass is ice-free.

-- The largest single ice-free area is in South Victoria Land, about 100 km from New Zealand's scientific research station, Scott Base on Ross Island, and also close to ?another U.S. base, McMurdo.

-- The permanent ice shelves floating on the sea around Antarctica are made up of ice and snow between 100 and 300 meters thick. Several in the north have collapsed in recent years, which many scientists link to global warming.

* DANGERS OF GLOBAL WARMING:

-- Antarctica is of particular significance to the international community because of its impact on global climate and sea conditions. If Antarctica all ever melted, world sea levels would rise by about 57 meters.

-- The Antarctic Peninsula, the most northerly part below South America, has warmed by about 3 Celsius (5.4 Fahrenheit) in the past 50 years. Most of the continent shows no sign of warming.

* LIFE ON ICE:

-- The cold and windy weather and dry conditions mean terrestrial life is very limited, with vegetation sparse and primitive, comprising mainly lichens, algae and mosses with only two species of flowering plants.

-- Marine life is diverse and rich with microscopic plankton at the base of the food chain. Antarctic fish are especially vulnerable to overfishing because most species take a long time to mature sexually and are long-lived.

-- Bird species from this region, mostly penguins, are highly adapted to a marine existence, but come ashore onto land or ice to breed and raise their young.

-- There are five species of seals in the region. The Crabeater, which accounts for over half the world's population of seals, the Leopard, the Weddell (after Sir James Weddell, commander of British sealing expeditions in Antarctica), Ross, the rarest of the species, and Elephant seals. Weddell seals are thought to number about 500,000, the Crabeater about 5,000,000 to 6,000,000, and the Ross seals about 50,000.

* ANTARCTIC TREATY:

-- A cornerstone treaty, signed in 1959 and enacted two years later, forms the basis of international governance.

-- The Antarctic Treaty is open to all members of the United Nations and others by agreement. Starting with 12 original signatory nations, members now number 47.

-- Covering all areas south of 60 degrees South latitude, it aims to set aside disputes over territorial sovereignty; secure freedom of and promote scientific investigation; and assure demilitarization of the continent.

-- Chile, New Zealand, Australia, France, Norway, Argentina, and the United Kingdom have territorial claims over parts of Antarctica. All claims are on hold under the Antarctic Treaty.

* OTHER KEY AGREEMENTS:

-- The Agreed Measures for the Conservation of Antarctic Fauna and Flora (1964)

-- Convention for the Conservation of Antarctic Seals (1972)

-- Convention on the Conservation of Antarctic Marine Living Resources (1982)

-- Protocol on Environmental Protection to the Antarctic Treaty (1991): this marked the first time countries agreed on detailed rules to protect the environment of an entire continent. It came into effect on January 14, 1998 and has detailed rules on topics such as waste disposal and marine pollution. It also includes a ban on mineral resource mining other than for scientific research, with a mechanism for reviewing the ban after 50 years, or earlier on agreement.

Sources: Reuters/www.britannica.com