Changes

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. 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.

Millions of square miles of sea ice surround Antarctica; the extent annually experiences a five-fold increase and decrease, with the winter maximum more than doubling the entire Antarctic region's area of ice coverage. Icebergs larger than the State of Connecticut have been observed. The temperature gradient associated with Antarctica's sea-ice zone is one of the strongest on Earth, and the seasonal variability in the extent of sea ice is an important regulator of the climate of the Southern Hemisphere. This is primarily because of the significant difference between sea ice and water in reflecting the sun's energy (albedo) and because the sea ice serves as a barrier to energy exchange between atmosphere and ocean. The extent of sea ice around Antarctica also regulates (and stimulates) primary productivity of microorganisms in surface waters, and the sea ice zone is one of the most dynamic biological systems on Earth. Global warming could cause a significant reduction in the extent of the sea ice; the potential climatic and biological impacts of a change remain problematic.

Millions of square miles of sea ice surround Antarctica; the extent annually experiences a five-fold increase and decrease, with the winter maximum more than doubling the entire Antarctic region's area of ice coverage. Icebergs larger than the State of Connecticut have been observed. The temperature gradient associated with Antarctica's sea-ice zone is one of the strongest on Earth, and the seasonal variability in the extent of sea ice is an important regulator of the climate of the Southern Hemisphere. This is primarily because of the significant difference between sea ice and water in reflecting the sun's energy (albedo) and because the sea ice serves as a barrier to energy exchange between atmosphere and ocean. The extent of sea ice around Antarctica also regulates (and stimulates) primary productivity of microorganisms in surface waters, and the sea ice zone is one of the most dynamic biological systems on Earth. Global warming could cause a significant reduction in the extent of the sea ice; the potential climatic and biological impacts of a change remain problematic.