Temps de lecture :4 minutes
Antarctica is made up of two major regions – East and West Antarctica – naturally separated by the 3,000 km-long Transarctic Mountains. East Antarctica is comprised of a 10 million square-kilometre ice dome. West Antarctica is lower and smaller representing a fifth of the continent’s land area with the Antarctic Peninsula accounting for a further 2%. The ice sheet flows down to the ocean to form ice shelves, floating platforms of ice with a cumulated surface area of 1.5 million km2. These ice shelves in turn flow and break up, calving tabular icebergs.
Monitoring climate change
Global warming is causing higher melting speeds and increasing snow falls in Antarctica. Findings from studies differ regarding the scope of the phenomenon, but suggest that the ice in Antarctica is retreating. In January 2008, NASA announced that 190 billion tons of ice were lost in 2006, mainly in West Antarctica, a region which appears more vulnerable to heavier losses through melting, whereas the East Antarctica ice sheet appears to be thickening. Out of 244 glaciers studied, 87% retreated by an average of 600 metres since the 1950s, at a pace which has been accelerating by 50 metres per year for the past five years. The Antarctic Peninsula has experienced one of Earth’s fastest warming trends, with temperatures increasing 3°C in the past fifty years. This increase in temperature is behind the disintegration of the Larsen B ice shelf. Increased melting may cause sea levels to rise higher than forecast. The geophysics and oceanography research centre (LEGOS) in Toulouse, France, estimates that Antarctic melting accounts for the rising sea level by 0.54mm/year, of a total 3.3mm/year recorded since 1993. This would confirm that the losses are not offset by the gains.
Because of the cold, dry conditions, flora of the Antarctica consist principally of lichens, mosses and algae. Only two endemic flower species are known. At sea, teeming phytoplankton are the base of the food chain, feeding krill, which in turn support fish, whales, seals, penguins and other birds. Some 300 fish species feed on krill, such as the ice fish which has no hemoglobin in its blood, and the Notothenia, which secretes anti-freeze proteins. With holes in the ozone layer near the poles, this balance is threatened because the phytoplankton is overexposed to UV rays. Its numbers may have already decreased by 6 to 12% due to disruption of photosynthesis. The krill population has plummeted by 80% since the 1970s, also due to intensive fishing which is now strictly regulated.
Although the Antarctic is not home to any endemic land vertebrates, it is a breeding ground for many species, including some forty sea birds. Penguins, which constitute 85% of Antarctica’s sea birds, gather by the thousands on the fast ice and coastlines. Half of the world’s pinniped population (seals and sea lions) breed in Antarctica, including Weddell seals, leopard seals, and 15 million crabeater seals. Most cetaceans also come here to feed and reproduce, the most remarkable being the Blue Whale.
The number of tourist vessels went up 344% in 13 years; the number of visitors disembarking increased 917% in 9 years. Forty years ago, the White Continent was visited by smaller vessels carrying some fifty passengers, but in 2000 cruise ships carrying 3,500 passengers started to appear. The number of tourists went from 13,600 in 2001/2 to 32,000 in 2005/6. Over 1,000 of those participated in land activities, such as skiing, climbing, or camping, and 1,165 flew over Antarctica. When tourism operators are factored in, the annual number of visitors reaches 50,000. Stops at natural sites are more and more frequent, and 98% of excursions take place on the Antarctic Peninsula where the flora and fauna are most abundant. The main tourism-related risks are deterioration of areas of vegetation which are vulnerable to treading under foot, introduction of foreign species and pollution arising from boating accidents.