Antarctica’s ice sheets are nearly 2.5km thick on average – five times the height of the Taipei 101 tower, the world’s tallest building. But scientists say they are already showing signs of climate change.
Satellite images show the West Antarctic ice sheet is thinning and may even collapse in the future, causing sea levels to rise.
Amid occasional flurries of snow, Ban flew over melting ice fields in a light plane, where vast chunks of ice the size of six-storey buildings could be seen floating off the coast after breaking away from ice shelves.
"All we’ve seen has been very impressive and beautiful, extraordinarily beautiful," he told reporters.
"But at the same time it’s disturbing. We’ve seen … the melting of glaciers."
It was the first visit by a UN chief to Antarctica.
Ban is preparing for a UN climate change conference in Bali, Indonesia, in December, which is expected to kick off talks on a new accord to curb carbon emissions after the Kyoto Protocol expires in 2012.
Ban has focused strongly on the environment and held a climate change summit at the United Nations on the eve of the annual General Assembly gathering of world leaders.
He is expected to continue his South American tour at Chilean national park Torres del Paine, where Andean glaciers are also being affected by global warming.
He will then visit Brazil, a leading force in developing biofuels from crops as an alternative to fossil fuels. Fears about climate change have fuelled a boom in biofuels.
Despite the controversy of diverting food crops into fuel production, Ban has said alternative energy sources are vital to addressing climate change.
Antarctica – a continent with only about 80,000 temporary residents – is 25 per cent bigger than Europe and its ice sheets hold some 90 per cent of the fresh water on the Earth’s surface.