Sea ice spread linked to ozone layer
SEA ice around Antarctica has been increasing at a rate of 100,000sq km a decade since the 1970s, according to a landmark study to be published today.
The study by the British Antarctic Survey, published in the journal Geophysical Research Letters, says rather than melting as a result of global warming, Antarctica continues to expand.
The fact that Antarctic ice is still growing does not in itself prove that global warming is not happening. But the BAS says increased ice formation can be explained by another environmental concern, the hole in the ozone layer, which is affecting local weather conditions.
But the absence of an ice melt overall does put a further question mark over extreme claims that the world faces precipitous rises in sea levels because of the melting polar ice caps.
Federal Environment Minister Peter Garrett has been under fire for suggesting sea levels could rise by 6m as a result of the melting of the Antarctic ice. Antarctica has 90 per cent of the Earth’s ice and extensive melting of its ice sheet would be required to raise sea levels substantially.
The Weekend Australian reported on Saturday that the results of ice-core drilling and sea ice monitoring indicated there was no large-scale melting of ice over most of Antarctica. Drilling in the fast ice, a type of sea ice, off Australia’s Davis Station last year showed the ice was 1.9m thick, its densest in 10 years.
The BAS, which discovered the ozone hole in the mid-1980s, has drawn on data from international agencies, including Australia’s three Antarctic bases.
BAS project leader John Turner told The Australian yesterday that cooling had been recorded at the Australian bases and elsewhere in east Antarctica. He said satellite images indicated the ozone layer had strengthened surface winds around Antarctica, deepening storms in the South Pacific area of the Southern Ocean. This had resulted in a greater flow of cold air over the Ross Sea, leading to more ice production.
While sea ice had been lost to the west of the Antarctic Peninsula, sea ice cover over the Ross Sea had increased.
Dr Turner said the research results indicated why the extensive melting of ice in the Arctic was not occurring in Antarctica.
“While there is increasing evidence that the loss of sea ice in the Arctic has occurred due to human activity, in the Antarctic, human influence through the ozone hole has had the reverse effect and resulted in more ice,” he said. As the ozone hole repaired itself as a result of measures in place to reduce chlorofluorocarbons in the stratosphere, the cooling in Antactica was expected to be reversed.
“We expect ozone levels to recover by the end of the century, and by then there is likely to be around one-third less Antarctic sea ice,” Dr Turner said.
He said that while the expansion of sea ice, the relatively thin ice in Antarctic coastal waters, had been established, debate continued about whether the main mass of the Antarctic ice sheet was growing or shrinking.