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The continent itself is depressed more than half-a-mile to near sea level under the tremendous load of the ice sheet, with some regions well below sea level. The highest mountains rise to elevations of over 14,000 ft. about the height of the U.S. Rocky Mountains.

The continent itself is depressed more than half-a-mile to near sea level under the tremendous load of the ice sheet, with some regions well below sea level. The highest mountains rise to elevations of over 14,000 ft. about the height of the U.S. Rocky Mountains.

The present Antarctic ice sheet accounts for 90 percent of Earth's total ice volume and 70 percent of its fresh water. The ice sheet at the Pole, nearly two miles thick, is constantly shifting, carrying the Amundsen/Scott Research Facility at the Pole along with it at the rate of about 30 feet a year. Nearly 90 percent of the ice flowing across West Antarctica converges into ice streams that are the most dynamic, and perhaps unstable, components of the ice sheet. Recent glaciological observations have yielded evidence that some of these West Antarctic ice streams may be responding to climatic and sea level changes of the recent past, changes that could lead to more rapid retreat and global sea-level rise in the future. A few active volcanoes may also affect the ice sheet's behavior.

The present Antarctic ice sheet accounts for 90 percent of Earth's total ice volume and 70 percent of its fresh water. It houses enough water to raise global sea level by 200 feet if completely melted. The ice sheet at the Pole, nearly two miles thick, is constantly shifting, carrying the Amundsen/Scott Research Facility at the Pole along with it at the rate of about 30 feet a year. Nearly 90 percent of the ice flowing across West Antarctica converges into ice streams that are the most dynamic, and perhaps unstable, components of the ice sheet. Recent glaciological observations have yielded evidence that some of these West Antarctic ice streams may be responding to climatic and sea level changes of the recent past, changes that could lead to more rapid retreat and global sea-level rise in the future. A few active volcanoes may also affect the ice sheet's behavior.

The Antarctic climate offers a formidable challenge to those who venture there in quest of scientific knowledge. It is the coldest, driest, highest (on average) and windiest continent on Earth. Absolute humidity is lower than on the Sahara. Annual snowfall in much of the interior is less than two inches. Winds that flow down the surface of the ice sheet toward the coast (katabatic winds) commonly reach speeds of 80 miles per hour, and maximum measured wind speeds have exceeded 180 miles per hour. Changes in the weather are dramatic: winds shift from calm to full-gale in a brief period of time. A drop of 65°F was once recorded in 12 minutes. Earth's lowest surface temperature (-126.9°F) was recorded at Russia's Vostok Station in the interior of Antarctica. Coastal locations in summer occasionally rise above the freezing point.

The Antarctic climate offers a formidable challenge to those who venture there in quest of scientific knowledge. It is the coldest, driest, highest (on average) and windiest continent on Earth. Absolute humidity is lower than on the Sahara. Annual snowfall in much of the interior is less than two inches. Winds that flow down the surface of the ice sheet toward the coast (katabatic winds) commonly reach speeds of 80 miles per hour, and maximum measured wind speeds have exceeded 180 miles per hour. Changes in the weather are dramatic: winds shift from calm to full-gale in a brief period of time. A drop of 65°F was once recorded in 12 minutes. Earth's lowest surface temperature (-126.9°F) was recorded at Russia's Vostok Station in the interior of Antarctica. Coastal locations in summer occasionally rise above the freezing point.

Offshore cyclones occur with little warning. Winds typically reach hurricane strength within an hour and persist for several days. A concentration of storm formation and/or intensification occurs at approximately 50°S latitude and is associated with some of the most violent seas in the world ("the roaring forties"). The stretch of ocean between Antarctica and the tip of South America is considered the most hostile in the world and has claimed numerous ships over the centuries.

Offshore cyclones occur with little warning. Winds typically reach hurricane strength within an hour and persist for several days. A concentration of storm formation and/or intensification occurs at approximately 50°S latitude and is associated with some of the most violent seas in the world ("the roaring forties"). The stretch of ocean between Antarctica and the tip of South America is considered the most hostile in the world and has claimed numerous ships over the centuries.

Meteorological observations have been recorded only in recent decades, and then only in scattered localities, so long-term temperature trends remain uncertain. The longest instrumental temperature records come from the relatively warm Antarctic Peninsula region, referred to by the "Frozen Chosen" as the "Banana Belt" of Antarctica. The glacial systems that occur in the Peninsular region are the most delicate in Antarctica and the most vulnerable to climatic warming. In historical time the fronts of the Larsen and George VI ice shelves, the two largest ice shelves in the region, have retreated at rates of nearly one-half mile per year. Another smaller ice shelf, the Wordie Ice Shelf, has completely vanished during the past several decades. Whether these changes are due to induced global warming or to natural (perhaps regional) climatic cycles remains uncertain.

Meteorological observations have been recorded only in recent decades, and then only in scattered localities, so long-term temperature trends remain uncertain. The longest instrumental temperature records come from the relatively warm Antarctic Peninsula region, referred to by the "Frozen Chosen" as the "Banana Belt" of Antarctica. The glacial systems that occur in the Peninsular region are the most delicate in Antarctica and the most vulnerable to climatic warming. In historical time the fronts of the Larsen and George VI ice shelves, the two largest ice shelves in the region, have retreated at rates of nearly one-half mile per year. Another smaller ice shelf, the Wordie Ice Shelf, has completely vanished during the past several decades. Whether these changes are due to induced global warming or to natural (perhaps regional) climatic cycles remains uncertain.

Other than the claimant states, most nations do not recognize Antarctic claims. U.S. non-recognition, a cornerstone of the nation's Antarctic policy, dates to 1924, when Secretary of State Charles Evans Hughes wrote that discovery of lands unknown to civilization "does not support a valid claim of sovereignty unless the discovery is followed by an actual settlement of the discovered country." In 1934 the Assistant Secretary of State added: "I reserve all rights which the U.S. or its citizens may have with respect to this matter." President Franklin D. Roosevelt reaffirmed the U.S. stance in 1939: "The U.S. has never recognized any claims of sovereignty over territory in the Antarctic regions asserted by any foreign state." In 1947 Dean Acheson, then Under Secretary of State, wrote that the U.S. "has not recognized any claims of any other nations in the area and has reserved all rights which it may have in the area."

Other than the claimant states, most nations do not recognize Antarctic claims. U.S. non-recognition, a cornerstone of the nation's Antarctic policy, dates to 1924, when Secretary of State Charles Evans Hughes wrote that discovery of lands unknown to civilization "does not support a valid claim of sovereignty unless the discovery is followed by an actual settlement of the discovered country." In 1934 the Assistant Secretary of State added: "I reserve all rights which the U.S. or its citizens may have with respect to this matter." President Franklin D. Roosevelt reaffirmed the U.S. stance in 1939: "The U.S. has never recognized any claims of sovereignty over territory in the Antarctic regions asserted by any foreign state." In 1947 Dean Acheson, then Under Secretary of State, wrote that the U.S. "has not recognized any claims of any other nations in the area and has reserved all rights which it may have in the area."

Despite the Antarctic Treaty provision that "no acts or activities taking place while the present Treaty is in force shall constitute a basis for asserting, supporting, or denying a claim to territorial sovereignty in Antarctica," some signatories have taken what appear to be assertive steps. For example, both Argentina and Chile publish their claimed Antarctic sectors on their official national maps, and both have established hotels and post offices. Chile has placed whole families in residence at its Antarctic stations, with schools, banks, and other evidence of "effective occupation," including the birth of a child. An Argentinian child was born at Argentina's Esperanza Station in the late 1970s.

Despite the Antarctic Treaty provision that "no acts or activities taking place while the present Treaty is in force shall constitute a basis for asserting, supporting, or denying a claim to territorial sovereignty in Antarctica," some signatories have taken what appear to be assertive steps. For example, both Argentina and Chile publish their claimed Antarctic sectors on their official national maps, and both have established hotels and post offices. Chile has placed whole families in residence at its Antarctic stations, with schools, banks, and other evidence of "effective occupation," including the birth of a child. An Argentinian child was born at Argentina's Esperanza Station in the late 1970s, the first child to be born on that continent..

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