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

7 Outlook for the Antarctic environment

At a glance

At the moment, Antarctica is still in a comparatively good condition. However, the pressures on the continent and the surrounding ocean are going to increase. For example, the extraction of marine resources will not only continue but will intensify in future. Most importantly, numerous climate change processes are now under way that are likely to alter the physical Antarctic environment in our lifetime. In turn, ecosystems and species populations will be affected. Organisms will either have to adapt or they will disappear. The most likely candidates to vanish are those that have adapted to narrow environmental limits, such as emperor penguins, and invertebrates that grow and develop slowly. New fisheries will open as species more adapted to warmer conditions than currently found in the Southern Ocean move south.

Climate change and the future of Antarctica remain topics of intense scientific research and debate as analysis of data is still hampered by uncertainties and in some areas data deficiencies. Climate change is unlikely to be linear and various regions will be impacted on different scales, as the dissimilar developments in East and West Antarctica already demonstrate. Despite all uncertainties, the risks associated with climate change are significant and deserve our full attention.

To assess the future of Antarctica and the Southern Ocean, a global perspective is required. Despite Antarctica's remoteness from centres of human population, the pressures generated in the rest of the world impact on Antarctic and Southern Ocean ecosystems through the linkages provided by atmospheric and oceanic circulations. Although the rate has slightly decelerated, the human population is still increasing and is expected to reach 9.3 billion in 2050.²³⁴ Increasing demands for raw materials and protein sources can only increase the possibility that, at some stage, people will look to Antarctica and the Southern Ocean, especially when resources reach their limits in other parts of the world.

The Scientific Committee on Antarctic Research has reviewed all available information on the impacts of climate change on Antarctica and the Southern Ocean, and provides a comprehensive synthesis of the future of the southern continent in its report, Antarctic climate change and the environment.³⁷ The report highlights that changes have been observed in the Antarctic environment and continued changes are expected in the climate and weather patterns of Antarctica, as well as in the physical and chemical properties of the Southern Ocean. While many of the underlying processes driving the changes are still not well understood, the processes that are changing the Antarctic environment appear to be well under way and are unlikely to be stopped in the immediate future.

While important regional differences of a number of indicators vary markedly in their expression and intensity, the overall trend away from the status quo in the Antarctic system is similar throughout the region. Change in East Antarctica is currently occurring at a slower rate than in West Antarctica, but the trends are similar. However, there are indications that this will change in the future. The fourth report of the Intergovernmental Panel on Climate Change predicts that changes expected in Antarctica will include a warming of the Southern Ocean, a freshening of at least its upper water masses, and a strengthening of the southern annular mode (SAM), which influences wind patterns.⁶ SAM is expected to strengthen and its storm tracks are likely to move south. The result is strengthening westerly winds and increasing insulation of Antarctica. This would limit the heat exchange between Antarctica and the tropics, and cool the southern continent. At the same time, the ozone hole (which currently has a relatively stable size and depth) may recover. Presently, the ozone hole buffers Antarctica from warming through a layer of clouds and may have led to an increase in sea ice extent over the past 30 years. Its recovery, which is expected in the middle of the 21st century, is likely to increase the warming of Antarctica, especially in the east. This makes it highly likely that the extent of sea ice will shrink: a reduction of 2.6 million square kilometres (or 33%) in the annual sea ice area is forecast (although models are currently unable to predict changes on a regional scale).

Over the next decades, ocean acidification will become more pronounced in the cold Southern Ocean than in warmer regions, particularly if the production of anthropogenic carbon dioxide continues at its present rate. There is a limit to how much carbon dioxide can be absorbed by the Southern Ocean and, if carbon dioxide production is not reduced, the Southern Ocean may no longer act as a carbon dioxide sink. A similar effect will be achieved as the ocean warms, because warmer waters have a reduced capacity to act as a carbon dioxide sink than cold waters. Over the past two centuries, the hydrogen ion concentration of surface water has increased by 30% in the world's oceans, lowering the pH by 0.1 units. This rate is about 100 times higher than it has been in the past.⁸³ Given the amount of carbon dioxide already in the atmosphere, a reversal of ocean acidification is unlikely in our lifetime.⁸³

In all likelihood, the distribution of species will change as those adapted to warmer climes expand their ranges south. Those organisms already existing in the high Antarctic will have to adapt or they will disappear. The most likely candidates to vanish in the long term are those that have adapted to live in very narrow environmental limits. Their extended life histories mean that, with the increasing rate of change in their environment, fewer and fewer generations will be able to acclimatise and adapt to the new conditions. Range expansions have already been reported from the Antarctic Peninsula region. Some animal, plant and microorganism populations are expected to expand in areas where more liquid water will become available and temperatures will increase.

We cannot yet predict the extent to which biodiversity will be impacted by the expected future changes. However, ocean acidification in particular is likely to have a profound effect on the Antarctic ecosystem because it affects organisms at the base of the food web. Whatever changes may occur in the biodiversity of Antarctica, the effects are expected to cascade through the entire ecosystem.

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