Although the impact of climate change and the Arctic are discussed often in the media, climate change in the Antarctic is comparatively neglected, or reported misleadingly.The science, however, is clear: climate change is already negatively impacting Antarctica.
The West Antarctic Peninsula is one of the fastest warming areas on Earth, with only some areas of the Arctic Circle experiencing faster rising temperatures. However, since Antarctica is a big place, climate change is not having a uniform impact, with some areas experiencing increases in sea ice extent. Yet in others, sea ice is decreasing, with measurable impacts on wildlife. ASOC believes that understanding climate change impacts on Antarctica is a matter of critical importance for the world and for the continent itself.
Local Antarctic effects of climate change are only part of the problem. Antarctica comprises two geologically distinct regions, East Antarctica and West Antarctica, separated by the great Trans-Antarctic Mountains but joined together by the all-encompassing ice sheet. The presence of the high ice sheet and the polar location make Antarctica a powerful heat sink that strongly affects the climate of the whole Earth. Furthermore, the annual sea ice cover around the continent, which seasonally reaches an area greater than that of the continent itself, modulates exchanges of heat, moisture, and gases between the atmosphere and ocean and, through salt rejection when it freezes, forces the formation of cold oceanic bottom waters that spread out under the world’s oceans. Alterations to this system will affect climate all over the planet.
Both the ice sheet and the sea ice are potentially subject to change in a changing climate; the ice sheet, in fact, may be changing now in response to past climate change. The greatest threat to the inhabited world comes from the West Antarctic ice sheet (WAIS), which rests on a bed far below sea level and so may have the potential for rapid shrinkage. The Antarctic is so vast, remote, and difficult to monitor, however, and the physical behavior of the ice sheet so complex, that there is as yet no definitive demonstration (or disproof) of such change, even though a pronounced climatic warming is ongoing in one northerly portion of the continent. The Antarctic ice sheet contains sufficient ice to raise world-wide sea level by more than 60 meters if melted completely. The amount of snow deposited annually on the ice sheet is equivalent to about 5 mm of global sea level, as is the mean annual discharge of ice back into the ocean. Thus, a modest imbalance between the input and output of ice might be a major contributor to the present-day rise in sea level (1.5–2 mm per year), but the uncertainty is large.
Antarctic species are dramatically impacted by climate as well. Krill often feed on algae underneath sea ice and populations have been declining around the West Antarctic Peninsula as sea ice has decreased. Adélie penguin populations have been declining in recent years due to reductions in krill populations and changing weather conditions in their traditional nesting areas. Emperor penguins are highly vulnerable as well and are predicted to suffer when the world’s average temperature increases by 2 degrees Celsius. Furthermore, a 2008 study has additionally identified Antarctic toothfish as highly vulnerable to climate change. Climate change in Antarctica will thus have dramatic effects both globally and locally – and perhaps harm some of the world’s most beloved species.