Antarctic climate change review finds ozone surprise

22 January 2010

The British Antarctic Survey has published the first comprehensive review of the state of Antarctica’s climate and its relationship to the global climate system. Antarctic Climate Change and the Environment, based on the latest findings of 100 scientists from 13 countries, focuses on the impact and consequences of rapid warming of the Antarctic Peninsula and the Southern Ocean; rapid ice loss in parts of Antarctica and the increase in sea ice around the continent; the impact of climate change on Antarctica’s plants and animals; the unprecedented increase in carbon dioxide levels; the connections between human-induced global change and natural variability; and the extraordinary finding that the ozone hole has shielded most of Antarctica from global warming, delaying the impact of greenhouse gas increases on the climate of the continent.

One effect of the ozone hole is that the polar vortex (south polar winds) has intensified and affected Antarctic weather patterns. Westerly winds over the Southern Ocean that surrounds Antarctica have increased by around 15%. The stronger winds have effectively isolated Antarctica from the warming elsewhere on the planet. As a result during the past 30 years there has been little change in surface temperature over much of the vast Antarctic continent, although West Antarctica has warmed slightly. An important exception is the eastern coast of the Antarctic Peninsula, which has seen rapid summer warming. This warming is caused by stronger westerly winds bringing warm, wet air into the region from the ocean.

Over this century the ozone hole is expected to heal, allowing the full effects of greenhouse gas increases to be felt across the Antarctic. Models suggest that the net effect will be continued slow strengthening of winds across the Southern Ocean, while sea ice will decrease by a third, resulting in increased phytoplankton productivity. The predicted warming of about 3°C across the continent is not enough to melt the main ice sheet and an increase in snowfall there should offset sea level rise by a few centimeters.
Lead author Professor John Turner of BAS says, “Understanding how polar sea ice responds to global change — whether human induced or as part of a natural process — is really important if we are to make accurate predictions about the Earth’s future climate. This new research helps us solve some of the puzzle of why sea-ice is shrinking is some areas and growing in others.”

From BAS press release 14/2009 –