Big Antarctic ice break-out raises climate change concern
21 March 2002
The recent loss of an area of nearly 8800 square kilometres from the Antarctic ice sheet – more than three times the size of the Australian Capital Territory – is a disturbing reminder of the fact of global warming as a reality, the Parliamentary Secretary responsible for the Antarctic, Dr Sharman Stone, said today.
A 5500 square kilometre piece of the Thwaites Glacier Tongue in West Antarctica last week broke away and floated into the Amundsen Sea, southeast of Australia, producing an enormous iceberg code-named B-22.
Over several weeks in February and March, the disintegration of a large part of the Larsen B Ice Shelf in the Antarctic Peninsula south of South America resulted in a loss of 3250 square kilometres of ice.
"The dramatic and unprecedented disintegration on Larsen B shows the impact of large-scale climatic changes going on in the world today, and the loss of ice from the Thwaites Glacier has reduced that floating tongue to its shortest size ever", Dr Stone said.
"These events have a major effect in the Antarctic region. The loss of such large pieces of coastal ice can radically change conditions on the frozen continent". Dr Neal Young, a senior Australian Antarctic Division glaciologist with the Antarctic Cooperative Research Centre in Hobart, said today that the Larsen and Thwaites events would make no difference to sea levels because they occurred on the floating part of the ice cover.
"Ice shelves and glacier tongues usually exhibit a natural sequence of growth and reduction over time," he said.
However, Dr Young said that the presence of large areas of floating ice around the edge of the grounded ice sheet, such as in the Larsen B Ice Shelf and Thwaites Glacier Tongue, provided a protective barrier to the glaciers behind them from maritime conditions of the atmosphere and ocean.
Past events had indicated that this recent ice loss was likely to result in a significant increase in glacial flow into the area of Larsen B ice shelf, he said.
Another large segment of the Larsen Ice Shelf east of the Antarctic Peninsula, Larsen C (the next section south of Larsen B), is a likely future casualty, according to the University of Colorado's National Snow and Ice Data Centre.
"While the Larsen ice loss was predicted four years ago, the fact that we have had two simultaneous events in different places on such a scale as this makes it an important event for global climate research," Dr Young said.
"Measurable warming of both atmosphere and ocean in the region of West Antarctica where the losses occurred undoubtedly led to these events.
"Such warming is not universal across Antarctica - on average the coastal regions about Antarctica are warming - and that trend is very strong in the Peninsula region. However continued warming and the progression southwards of the break up of ice shelves, are events we cannot ignore as indicators of the future impact on the main Antarctic ice sheet," Dr Young said.