State of the Environment 2011 (SoE 2011)
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.
7 Antarctic environment
3 Pressures affecting the Antarctic environment
At a glance
Antarctica is changing at an increasing rate due to global warming. The most rapidly changing region is West Antarctica, particularly around the Antarctic Peninsula, where temperatures have risen by 5 °C over the past five decades. Until recently, the environmental variables were thought to be more stable in East Antarctica where Australia operates. However, there is compelling evidence that change is occurring here as well, and while it is currently at a slower rate than in West Antarctica, the rate of change is expected to increase over the coming decades. The changes will affect the marine and terrestrial ecosystems of the region, probably profoundly, in the coming decades.
Human activities are still increasing; new stations are being constructed, often in rare ice-free areas. Tourism is still a major activity around the Antarctic Peninsula. Disturbance of habitat and wildlife, the introduction of invasive plants and pollution are all risks linked to human presence on the continent.
Extreme weather events are likely to increase in frequency and perhaps in intensity as the planet warms. Antarctica is known for its high winds and intense storms. However, in certain regions, rain is now occasionally falling where it only ever used to snow. These events too are changing the Antarctic environment and biodiversity.
As detailed in Chapter 2: Drivers, the key drivers on the environment are population and economic growth, and climate change. Antarctica, as the only continent without a native human population, has been subjected to less pressure from human activities than other continents. However, the southern continent and its surrounding seas and islands have not escaped the effects of these activities. For example, the atmosphere above Antarctica experienced a major change due to the release of chlorofluorocarbons in the 20th century, which resulted in the development of the ozone hole. The establishment of permanent stations impacts on the local environment, and pollution elsewhere on our planet finds its way even to Antarctica: traces of DDT and its derivatives were discovered in the shells of Adélie penguin eggs in the mid-1960s.189 A number of vertebrate populations were hunted to near extinction, and economic activities such as fishing and tourism have all had an impact.
What is most likely to have the most lasting impact is the increasing amount of carbon dioxide produced by human activities. The Southern Ocean is absorbing vast quantities of carbon dioxide, leading to a change in the ocean's chemistry that has the potential to affect organisms and their lifecycles in a variety of ways. Increased atmospheric carbon dioxide is also producing climate change. We have seen a warming of surface temperatures initially restricted to the Antarctic Peninsula, where surface temperatures increased by 0.56 °C per decade over the past 50 years,190 while the global temperature increase averaged 0.13 °C per decade.6 This warming has led to the collapse of most of the ice shelves in the peninsula region,58 retreating glaciers191 and a decrease in the extent of sea ice in the Bellingshausen Sea.192
Until recently, East and West Antarctica appear to have responded differently to the influences of climate change (see Section 2.1.2). While only West Antarctica experienced warming conditions for several decades, changes in near-surface temperatures across the entire continent have now been estimated at 0.12 ± 0.10 °C per decade.38 Increasing air and ocean temperatures cause changes in snow-fall patterns, which in turn affect the quality of sea ice, as well as its extent and durability. For example, near Davis Station, a long-term monitoring study of sea ice detected a delay in the time when the maximum thickness is reached by the fast ice, and attributed this trend to the warmer winters in recent years.193
Assessing the overall impact that climate change will have on Antarctic systems is difficult, however, because there is a lack of data for large parts of the continent; timeseries tend to be too short or available only for a small number of locations. The processes driving weather patterns and underlying climate change are complex, because they can operate on different time and spatial scales, and may lead to positive or negative feedback loops as they either increase or counteract each other. Connections between, for example, atmospheric and oceanographic phenomena are also still poorly understood.
Similarly, while it is highly likely that climate change will alter ecosystems, the processes involved are complex and not fully understood. Currently available biological models are even less sophisticated than physical ones; models of the Southern Ocean's food webs fall short in linking dynamics at the base of the food web to physical models of the oceans.194 Predicting how organisms will respond individually or collectively to climate change and other human-induced pressures is a major challenge of research today. We do not know which species may be able to adapt to the evolving environment through genetic responses. Some organisms may benefit from the effects of climate change-at least in the short term. For example, more ice-free areas offer a potential habitat for plants and animals. However, the long-term consequences are hard to predict.
The restoration of ozone levels will also have a profound effect on the region. The ozone hole is expected to vanish in the next three decades. This will reduce ultraviolet levels to the advantage of many species (see Section 2.3.1). Ultraviolet radiation was 55-85% higher at the South Pole during 1991-2006 compared with 1963-80.40 However, the ozone hole has largely protected East Antarctica from global warming. The loss of stratospheric ozone cooled and changed the atmospheric circulation. A recovery of the ozone hole will reverse these processes and significantly increase the warming trend in East Antarctica.
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