Overview of state and trends of the Antarctic environment
What has changed since 2011?
- Antarctic sea ice has shown a general increase in overall extent, but some areas are showing rapid decline.
- The ozone layer is starting to recover as a direct consequence of international controls on the use of human-made ozone depleting substances.
- Climate change is affecting the entire Antarctic food web, and warmer temperatures on land have already led to the establishment of non-native plants.
- Macquarie Island is recovering following the eradication of invasive vertebrates from the island.
State and trends
The physical and chemical components of the Antarctic environment are changing in response to global pressures of human activity and climate change. These changes are occurring against a backdrop of climatic variability.
Annual average surface temperatures throughout Antarctica have generally increased in the past 6 decades, with periods of significant warming occurring in the Antarctic Peninsula region and West Antarctica (Turner et al. 2014). Compared with the late 20th century, recent temperature trends on the Antarctic Peninsula are less marked and show greater consistency with natural variability (Turner et al. 2016). Coastal East Antarctica is generally warming, although the trend is weaker than in West Antarctica, and some regions and seasons show evidence of cooling (Steig et al. 2009, Turner et al. 2014).
There are indications that stratospheric ozone levels above Antarctica in spring and summer have improved, although meteorological factors continue to significantly influence the year-to-year severity of the ozone hole. Although ozone improvement is good news, the Antarctic ozone hole has limited the warming of the Southern Hemisphere summer climate, primarily by causing a strengthening and southwards shift of westerly winds across the Southern Ocean. The repair of the ozone hole is likely to increase the impact of warming temperatures on Antarctica.
The Southern Ocean is changing in ways that are likely to affect regional and global climate and marine productivity (Rhein et al. 2013). Ocean temperatures around the Antarctic continent have increased more rapidly and to a greater depth than the global average in recent decades (Roemmich et al. 2015). This warming has been linked to glacier retreat and ice-shelf disintegration in West Antarctica (Miles et al. 2013), and indications of increased melting of the Antarctic ice sheet (Schodlok et al. 2016). The extent of sea ice around Antarctica has shown a small overall annual increase in recent decades, although there are significant regional decreases in the Ross and Weddell seas.
The complex Antarctic food web is based on vast numbers of marine microorganisms, including bacteria, phytoplankton and zooplankton. Changes to the marine environment, including ocean acidification, will have a significant impact on these organisms and, because they are at the base of the food web, these changes will have profound effects throughout Antarctic ecosystems.
Warmer temperatures on the Antarctic Peninsula have already led to the establishment of non-native plants (Volonterio et al. 2013). A notable step has been taken in the past few years to redress the damage caused by introduced species in the subantarctic through the successful eradication of cats, rabbits, rats and mice from Macquarie Island.
Jackson WJ, Argent RM, Bax NJ, Bui E, Clark GF, Coleman S, Cresswell ID, Emmerson KM, Evans K, Hibberd MF, Johnston EL, Keywood MD, Klekociuk A, Mackay R, Metcalfe D, Murphy H, Rankin A, Smith DC, Wienecke B (2016). Overview: Overview of state and trends of the Antarctic environment. In: Australia state of the environment 2016, Australian Government Department of the Environment and Energy, Canberra, https://soe.environment.gov.au/theme/overview/antarctic-environment/topic/overview-state-and-trends-antarctic-environment, DOI 10.4226/94/58b65510c633b