Although isolated from other continents, Antarctica is connected to the rest of world through oceanic and atmospheric circulations. Antarctica and the surrounding Southern Ocean are key drivers of Earth's oceanic and atmospheric systems. A critically important feature is that about 90% of Earth's ice (around 25.2 million gigatonnes)4-5 is found here, and 70% of all available fresh water is locked up in the Antarctic ice sheet - if melted, this would raise sea levels by nearly 60 metres.6
Equally important, between the coastline of the Antarctic continent and the Antarctic Polar Frontal Zone (the boundary between subtropical and subantarctic waters) lies the Southern Ocean, which extends over some 38 million km2 and encompasses about 20% of the world's ocean waters.7 The Southern Ocean connects the three main ocean basins (Atlantic, Pacific and Indian) and creates a global circulation system that is largely driven by the eastward flowing Antarctic Circumpolar Current - the world's largest current. The current generates an overturning circulation (movement of water masses of different densities caused by variations in salinity and temperature) that transports vast amounts of heat and also takes up a significant amount of carbon dioxide from the atmosphere.8 Atmospheric pressure, humidity, air temperatures and wind patterns for our entire planet are interconnected and greatly influenced by processes in the Southern Ocean.
As well as playing an important role in influencing weather patterns, the Antarctic environment provides a valuable benchmark for climate change. The Antarctic continental ice holds one of the oldest and most detailed climate records. Moreover, the Antarctic environment and biosphere comprise highly sensitive indicators of present-day environmental change. Predictions made in the 1980s and 1990s about climate change and its effects in the polar regions in the 21st century have largely been confirmed.9 The major difference between previous predictions and recent observations is that the forecast change appears to be occurring at a faster rate than originally expected; for example, changes in ice sheets and glaciers are accelerating.10-12 The western Antarctic Peninsula region has been warming two to three times faster than the global average and has become one of the fastest warming regions on Earth.13 Over this period, 3 of the 12 ice shelves in the peninsula region have retreated significantly and 4 have collapsed, amounting to a loss of about 18% of the floating ice.14 However, in East Antarctica, which has been shielded from the effects of global warming by the ozone hole,15 the warming is less than the global average.16 The regional differences in the responses to climate warming and variability highlight the complexity of the processes currently affecting Earth's environment.