Key findings

The Antarctic region is showing the effects of climate change

  • Antarctica, the Southern Ocean and subantarctic islands continue to show the effects of global climate change. The range and abundance of iconic species are changing; patterns in sea ice formation are increasingly unpredictable; and glaciers and ice sheets are melting. The Antarctic Peninsula and part of West Antarctica have experienced the greatest change. In East Antarctica, where Australia operates, the climate has remained comparatively stable over recent decades, although this conclusion is somewhat uncertain because detailed observations are lacking across much of this area.
  • The most important factors contributing to physical change in the Antarctic region are warming of the upper ocean and the lower atmosphere, caused by increasing emissions of greenhouse gases, and changes in atmospheric circulation, largely influenced by the cooling effect of ozone depletion during spring in the Antarctic stratosphere. The strengthening of near-surface winds over the Southern Ocean associated with ozone depletion has mitigated the influence of global climate change on the Antarctic region during summer.
  • Although the size of the Antarctic ozone hole varies from year to year, there is increasing evidence that stratospheric ozone concentrations are recovering. This is a direct result of the Montreal Protocol in successfully controlling the production and release of ozone-depleting gases. These controls are also helping to reduce the pace of global warming, because many of the human-made gases that cause ozone destruction are strong greenhouse gases.

Antarctica and the Southern Ocean affect the global climate and food webs

  • The Southern Ocean has continued to warm, and this has influenced the transport of heat and moisture in the margins of Antarctica. Major regional changes continue to occur in sea ice cover around the continent. The trend of increasing sea ice coverage from the 1980s appeared to be reversing in the 2010s. Changes in sea ice growth and retreat will change important oceanic circulation patterns that affect global climate and ecosystems. Overall, the contribution to global sea level rise from the melting of the Antarctic ice sheet and associated glaciers is becoming more important.
  • The Southern Ocean continues to absorb carbon dioxide (CO2) from the atmosphere and is becoming more acidic (less alkaline) as a direct result. Ocean acidification, changes in wind strength, variability in sea ice and changes in the circulation of the Southern Ocean are affecting Antarctic ecosystems. Ocean acidification, in particular, is likely to have a profound effect on the Antarctic environment because it affects organisms at the base of the food web. Effects are likely to cascade through the entire ecosystem. However, our understanding of the responses by many Southern Ocean biota is relatively poor, making predictions of longer-term impacts highly uncertain. Changes in sea ice conditions affect the ability of animals that depend on the sea ice, such as penguins and seals, to breed successfully. Changes in sea ice extent and duration also affect populations of prey of Antarctic predators.

Changes are outpacing the ability of species to adapt, and some species will become extinct

  • The rate at which the physical environment of the Antarctic region is changing appears to be faster than the rate at which organisms, especially those of a higher order (e.g. fish, birds), can adapt to the changes. Although a few species may see benefits from some changes (e.g. more breeding territory may become available as glaciers retreat), these and other species may lose their prey resources, may be outcompeted by species that can adapt to the changing ecosystems, or may be replaced by species whose range is now extending from warmer climes into the Antarctic region. The candidates most likely to become extinct are those that have adapted to live within very narrow environmental limits.
  • Subantarctic islands are particularly at risk of invasions by non-native flora and fauna. Increasing temperatures allow more plant species to establish and may potentially enhance plant growth. At Heard Island, retreating glaciers may generate new habitat for both fauna and flora. Non-native microorganisms and invertebrates may also become established. Change is difficult to assess as visits to the island occur infrequently.

Fishing and other human activities add to the pressures on the Antarctic environment, and international collaboration is needed to better protect and manage the region