Australia's Antarctic researchers have taken a rare look at the luminous world under the polar sea ice, and brought it home.
A remotely operated underwater vehicle was sent into the frozen depths of the Southern Ocean about 3400 kilometres south-west of Hobart to find vibrant light under the jumbled pack ice. It came back with an abstract artist's palette of blues and greens.
"The ROV's icy dives transported us into a different world," the voyage's science leader, Klaus Meiners, of the Australian Antarctic Division, said in Hobart on Friday.
On the late-winter voyage the icebreaker Aurora Australis punched into the ice and stayed fixed while researchers fanned out to gather data.
They drilled a hole in the ice beside the ship to lower the ROV through, then operated it by a joystick as its cameras took them on an under-ice ride.
"The subsurface of the ice was like a badly eroded mountain range, with Antarctic krill and patchy areas of algae,” Dr Meiners said.
Satellite observation by the British Antarctic Survey and NASA recently showed the Antarctic sea ice was expanding slightly, in contrast to the Arctic's dramatic loss.
More powerful winds accompanying climate change appear to be blowing the ice away from Antarctica's coastline in some areas.
But Dr Meiners said climate models predicted sea ice in Antarctica could decline by 35 per cent in volume by the end of the century.
"So understanding the distribution of sea ice algae will enable us to assess the impacts of climate change on the Antarctic marine ecosystems into the future,” he said.
The researchers also used a high-volume water pump to capture live krill for the division's aquarium in Hobart.
“Most krill research has been conducted on adult krill during the Antarctic summer and only a few studies have focused on the larval stages during winter,” AAD krill aquarium manager, Rob King, said.
This time the ice pack also caught the Aurora Australis, holding it for 10 days before the ship was able to punch itself free and return to Hobart.