Chilly warning from scientists on impact of Antarctica changes
DateJanuary 7, 2014
Peter Hannam
Environment Editor, The Sydney Morning Herald
Evidence of climate change in parts of Antarctica is as dramatic as anywhere in the world and has a potentially big impact for Australia, scientists say. While recent public attention has focused on the stranded ships
requiring rescue from sea ice, the wider picture is one of rapid change that reflects global warming and will also drive it, they say.
"Antarctica is one of the key drivers of the global climate system," said Tony Press, head of the Antarctic Climate & Ecosystems Co-operative Research Centre (ACE CRC) in Hobart. "Changes in Antarctica will affect not only the Antarctic region but Australia and the rest of the planet."
The change in sea-ice coverage is massive every year - roughly increasing from a minimum of about 3 million square kilometres at the end of summer to about 19 million square kilometres by late spring. However, regions of West Antarctic are recording a drop in sea-ice extent of about 7 per cent each decade, or more than the 4.15 per cent reduction in Arctic ice.
"It's a very marked regional response [to climate change], more so than for the Arctic," Phil Reid, an Antarctic scientist with the Bureau of Meteorology, said. Countering that reduction in the west, in part, is an increase in ice off east Antarctic, possibly because of extra snowfall. Overall, "it's not more sea ice, it's just differently distributed", said Jan Lieser, a marine glaciologist with the research centre.
Some of the additional sea ice in eastern regions may also be the result of melting of land-based sheets, resulting in cooler ocean conditions. Fresher water is more conducive to sea-ice formation. Recent work by Dutch researchers has identified such changes in the Ross Sea region south of New Zealand, Dr Reid said.
The sea-ice extent also seems to be affected by westerly winds, which have strengthened by 15 per cent to 20 per cent since observations began in the late 1970s. The low-pressure systems have also shifted about 1-2 degrees south over the period, with apparent impacts on Australian rainfall.
When there is heavy snowfall at Law Dome, directly south of Perth, the south-western part of Western Australia is very dry as rainfall systems slip south of the continent, Dr Press said. The use of proxy records such as ice cores indicates the same pattern may explain lower rainfall for the Murray-Darling Basin.
"There are very strong connections between those big weather patterns in Antarctica and rainfall and drought in Australia," Dr Press said.
Hobart will host a conference on sea ice from March 10-14, where this "sensitive indicator of climate change" will be discussed, the
symposium's website says. Future research will focus on issues such as the stability of the eastern Antarctic ice sheet, its potential to significantly lift global sea levels if it melts, and just how thick the sea ice is around the continent as it expands and retreats each year.
"We just don't know how thick it is," Dr Press said.
Tongue lashing
Meanwhile, the US Coast Guard's
heavy ice-breaker Polar Star is expected to reach the beset Russian expedition ship Akademik Shokalskiy, and its would-be rescuer, the Chinese ice-breaker Xue Long (Snow dragon), within a week.
The build-up of ice that stranded the two ships, and required Australia's Aurora Australis to divert from its planned mission to assist the rescue, is considered to be largely unrelated to shifting climate patterns in the far south.
In 2010, a massive iceberg B9B, measuring 97 kilometres broke off part of the Mertz Glacier tongue.
The splintered glacier itself had a surface area of 2,500 square kilometres, with the calving event
captured in these pictures.
Read more:
http://www.smh.com.au/environment/c...ica-changes-20140106-30dmr.html#ixzz2pgawOp3E
