7 Antarctic environment | Key findings
State of the Environment 2011 Committee. Australia state of the environment 2011.
Independent report to the Australian Government Minister for Sustainability, Environment, Water, Population and Communities.
Canberra: DSEWPaC, 2011.
The ozone hole has largely protected East Antarctica from global warming.
Over the past half-century, western Antarctic surface temperatures have shown general warming trends with significant regional patterns. The Antarctic Peninsula is warming faster than anywhere else on Earth. In East Antarctica, the lower stratosphere has cooled and changed the atmospheric circulation through the loss of stratospheric ozone. A recovery of the ozone hole will reverse these processes and significantly increase the warming trend in East Antarctica.
The East Antarctic Ice Sheet is losing ice at its coastal fringes.
Although the mass of the whole Antarctic ice sheet has remained roughly the same over recent decades, the coastal fringes of the East Antarctic Ice Sheet have lost about 60 billion tonnes of ice each year since 2006. The annual loss is occurring at an increasing rate and may contribute significantly to sea level rise in the future.
Major regional changes are occurring in Antarctic sea ice coverage.
Over the past 30 years, there has been a small increase in the areal extent of sea ice around Antarctica, but with strong regional differences. Most notable are contrasting regional changes in sea ice seasonality (i.e. timing of annual ice advance and retreat and resultant coverage duration) attributed to changing patterns of large-scale atmospheric circulation. In the Western Antarctic Peninsula region, there is mounting evidence that a shortening of the ice season has affected multiple levels of the marine food web, whereas there is a trend towards lengthening of the annual sea ice season in the Western Ross Sea sector. The signal in the East Antarctic sea ice zone is mixed and complex, and is currently under investigation.
The Southern Ocean is getting warmer.
In the region from 35°S to 65°S, the upper Southern Ocean has warmed by 0.2°C since the 1950s. This rate of warming is faster than elsewhere in the global ocean. Warmer waters enable alien species to extend their range southwards. These immigrating species are less specialised for the cold environment than Antarctic species, and are likely to outcompete, and perhaps replace, the native species. This could have a significant impact particularly on benthic (ocean floor) communities and ecosystem functioning.
Increased acidification of the Southern Ocean can affect the base of Antarctic food webs.
Dissolved carbon dioxide acidifies the ocean and reduces the availability of carbonate ions that calcium carbonate shell-making organisms require for calcification, diminishing the ability of these organisms to form shells. Change in acidity of the ocean is already affecting calcifying organisms - the shells of planktonic organisms known as foraminifera, which are food for many other organisms, are now about one-third lighter compared with pre-industrial times. These types of changes, which affect the base of the food web, can potentially change the dynamics of the Southern Ocean ecosystem significantly.
Antarctic vertebrates are highly specialised to survive in the Antarctic. Whether they can adapt to new conditions due to climate change is currently unknown.
Antarctic vertebrates encompass a variety of flying seabirds and penguins, several seal and whale species, and numerous fish. In the Antarctic Peninsula region, an apparent decrease in the abundance of Antarctic krill has been attributed to the observed reduction in winter sea ice coverage. This in turn has caused a decrease in Adélie and chinstrap penguin populations. Environmental changes cascade through ecosystems. As the rate of environmental change increases, it may exceed the rate at which vertebrates can adapt. Hence, it is likely that some species will not survive the coming decades.
The pressure of human activities on Antarctica and the Southern Ocean is increasing.
The Protocol on Environmental Protection to the Antarctic Treaty commits signatories to comprehensive protection of the Antarctic environment. Australia has ratified the protocol by establishing legislation to enforce procedures for reducing the impacts of Australians visiting Antarctica and has taken practical steps to reduce the impacts of past activities, such as the clean-up of abandoned waste disposal sites. However, the human footprint in the region is gradually increasing. New stations are still built; tourism to the continent continues to grow, particularly to the Antarctic Peninsula near South America; and, with a growing world population, commercial fishing activities are likely to increase. Adequate resources are needed to monitor the intensity and frequency of all human activities.
The terrestrial ecosystems are changing, especially where snow fall is replaced by rain.
Retreating glaciers, particularly in the subantarctic, higher ambient temperatures and precipitation as rain rather than snow make the terrestrial environment more accessible to plant and microbial communities. A warmer climate and increased availability of liquid water enables their populations to expand and non-native species to become established.
The natural heritage of Macquarie Island has suffered under the impact of introduced species, but a large-scale eradication program is under way.
Introduced vertebrates, such as rats, mice and rabbits, have caused a major deterioration of the natural heritage values of Macquarie Island. Overgrazing by these species in particular has increased landslides, many of which have damaged seabird colonies. A large-scale eradication program is currently under way to rid the island of these alien species.