Iceberg in the Southern Ocean.
The most dramatic changes are happening around the Antarctic Peninsula which is one of the most rapidly warming regions on Earth. A recent review showed that over the last 61 years, 87 percent of glaciers on the Antarctic Peninsula have retreated. The retreat began at the northern tip of the Antarctic Peninsula and, over time has moved southwards as temperatures have risen.
While there has been an increase in sea ice in some parts of Antarctica, a change linked to increased offshore winds resulting from the ozone hole, there has also been a significant reduction in duration and extent of winter sea ice west of the Antarctic Peninsula. Just as sea ice is critical to the marine life of the Arctic so it is to the marine life of the Antarctic.
Krill, the basis of the Antarctic food web, use winter sea ice as a nursery and the loss of winter sea ice leads to a fall in krill numbers the following summer with consequences for the whales, seals and penguins that feed on them. In addition, Adélie and Emperor penguins rely on the sea ice in Antarctica for breeding and feeding, just like polar bears do in the Arctic.
Polar bears and emperor penguins may live at opposite ends of the Earth, but it turns out they may have more in common than we realized - and not in a good way.
Already it appears that in some places ice-dependent Adélie penguins are being replaced by open-water species. According to a recent Woods Hole study, a large emperor penguin colony in Terre Adelie, Antarctica, could face the loss of 95% of its population by the end of the century.
The most spectacular physical changes in the Antarctic environment relate to the ice shelves of the Antarctic Peninsula. These are floating extensions of a grounded ice-sheet and globally most of them are located in bays around the Antarctic continent. It has been estimated that 14,000 square kilometres of ice have been lost from ten floating ice shelves in Antarctica over the last 50 years. Although the ice shelves are floating and therefore their breaking off will not contribute to sea level rise directly their loss will accelerate in the speed at which the glaciers that feed into the ice shelves move toward and eventually dump ice into the sea. This will contribute to sea level rise.
The British Antarctic Survey lists seven ice shelves which have been seriously impacted by warming on the Antarctic Peninsula. In some cases dramatic collapses have occurred such as the loss of the Larsen A ice shelf in 1995 which collapsed in a matter of weeks. The Prince Gustav ice shelf also collapsed in 1995, having retreated progressively during the late 20th century. This was followed by collapse in 2002 of the Larsen B ice shelf.
The Wilkins ice shelf is likely to be next. Its collapse has been predicted since it lost around 1000 square kilometres in 1998. Ten years later, in March 2008, a further 400 square kilometres was lost. In late November 2008, new rifts developed on the Wilkins ice shelf. In April 2009, the 25 mile ice bridge connecting the Wilkins Ice Shelf to the Antarctic continent splintered putting the entire ice shelf at risk of further disintegration.