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Autonomous robot sub studying Antarctic ice shelf melting

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Autonomous robot sub studying Antarctic ice shelf melting

Postby U-5075 » Wed Mar 18, 2009 8:43 am

http://www.sciencedaily.com/releases/20 ... 113818.htm
One photo

Robot Sub Searches For Signs Of Melting 60 Km Into An Antarctic Ice Shelf Cavity

ScienceDaily (Mar. 18, 2009) — Autosub, a robot submarine built and developed by the UK's National Oceanography Centre, Southampton, has successfully completed a high-risk campaign of six missions travelling under an Antarctic glacier.

Autosub has been exploring Pine Island Glacier, a floating extension of the West Antarctic ice sheet, using sonar scanners to map the seabed and the underside of the ice as it juts into the sea. Scientists hope to learn why the glacier has been thinning and accelerating over recent decades. Pine Island Glacier is in the Amundsen Sea, part of the South Pacific bordering West Antarctica. Changes in its flow have been observed since the early 1970s, and together with neighbouring glaciers it is currently contributing about 0.25 mm a year to global sea level rise.

Steve McPhail led the Autosub team during the ten-day survey. He said: "Autosub is a completely autonomous robot: there are no connecting wires with the ship and no pilot. Autosub has to avoid collisions with the jagged ice overhead and the unknown seabed below, and return to a pre–defined rendezvous point, where we crane it back onboard the ship.

"Adding to the problems are the sub zero water temperatures and the crushing pressures at 1000 m depth. All systems on the vehicle must work perfectly while under the ice or it would be lost. There is no hope of rescue 60 km in, with 500 metres of ice overhead."

An international team of scientists led by Dr Adrian Jenkins of British Antarctic Survey and Stan Jacobs of the Lamont-Doherty Earth Observatory, Columbia University, New York on the American ship, the RVIB Nathaniel B Palmer, has been using the robot sub to investigate the underside of the ice and measure changes in salinity and temperature of the surrounding water.

After a test mission in unusually ice-free seas in front of the face of the glacier, they started with three 60km forays under the floating glacier and extended the length of missions to 110km round-trip. In all, a distance over 500km beneath the ice was studied.

Using its sonar, the Autosub picks its way through the water, while creating a three-dimensional map that the scientists will use to determine where and how the warmth of the ocean waters drives melting of the glacier base.

"There is still much work to be done on the processing of the data", said Adrian Jenkins, "but the picture we should get of the ocean beneath the glacier will be unprecedented in its extent and detail. It should help us answer critical questions about the role played by the ocean in driving the ongoing thinning of the glacier."

The lead US researcher on the project, Stan Jacobs, is studying the Pine Island Glacier with International Polar Year (IPY) funding from the National Science Foundation (NSF). One of the IPY research goals is to better understand the dynamics of the world's massive ice sheets, including the massive West Antarctic Ice Sheet. If this were to melt completely global sea levels would rise significantly. The most recent report of the Intergovernmental Panel on Climate Change (IPCC) noted that because so little is understood about ice-sheet behaviour it is difficult to predict how ice sheets will contribute to sea level rise in a warming world. The behaviour of ice sheets the IPCC report said is one of the major uncertainties in predicting exactly how the warming of the global will affect human populations.

Complementing the Autosub exploration, other work during the 53-day NB Palmer cruise included setting out 15 moored instrument arrays to record the variability in ocean properties and circulation over the next two years, extensive profiling of 'warm' and melt-laden seawater, sampling the perennial sea ice and swath-mapping deep, glacially-scoured troughs on the sea floor.

Autosub is an AUV – Automated Underwater Vehicle, designed, developed and built at the National Oceanography Centre, Southampton with funding from the Natural Environment Research Council. Autosub has a maximum range of 400km and is powered by 5,000 ordinary D-cell batteries. The batteries are packed in bundles in pressure-tested housings. Either end of the seven-metre sub there are free-flooding areas where the payload of instruments are installed. It carries a multibeam sonar system that builds up a 3D map of the ice above and the seabed below.. It also carries precision instruments for measuring the salinity, temperature, and oxygen concentrations in the sea water within the ice cavity, which are vital to understanding the flow of water within the ice cavity and the rate of melting. Autosub is 7m long and weighs 3.5 tonnes. Travelling at 6km hour it is capable of diving up to 1600 m deep, and can operate for 72 hours (400 km) between battery changes.
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Postby raalst » Wed Mar 18, 2009 1:06 pm

same story but with video
Seems the ' bot has damage on the nose...

http://www.theregister.co.uk/2009/03/18/autosub_back_from_beneath_ice/
Regards,

Ronald van Aalst

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Postby U-5075 » Wed Mar 18, 2009 3:57 pm

FOR WHAT HAPPENED TO NOSE OF SUB CHECK LAST SECTION, BELOW "LUCK ESCAPE"

http://planetearth.nerc.ac.uk/news/story.aspx?id=366
Robot sub explores deep beneath Antarctic ice shelf
18 March 2009

A UK-built robot submarine has successfully returned from a perilous 110-kilometre expedition under an Antarctic ice shelf - the Pine Island Glacier.

The ice shelf juts 60 kilometres into the ocean from the Antarctic mainland. The unmanned sub, known as Autosub, ventured as close to the grounding line - where the ice sheet hits the water - as the scientists who programmed it dared.

The high-risk expedition was necessary to find out why the glacier has been thinning and accelerating in recent decades.

The sub, designed by scientists and engineers at the National Oceanography Centre, Southampton, completed six missions under the ice over ten days.

Pine Island Glacier lies in the Amundsen Sea - part of the South Pacific bordering West Antarctica. The glacier is moving at a rate of four kilometres every year. Pine island and neighbouring glaciers are responsible for global sea level rises of about 0.25 mm a year.

Steve McPhail who led the Autosub team said, 'Autosub is a completely autonomous robot. There are no connecting wires with the ship and no pilot.'

The sub, which has a top speed of five kilometres an hour, uses sonar to pick its way under the ice. On the way it measures the salinity and temperature of the surrounding water and maps the jagged ice overhead and the unknown seafloor below. Scientists will use the sub's three-dimensional maps of the underside of the ice to determine where and how the warmth of the ocean waters melts the glacier base.

No hope of rescue
'All systems on the vehicle must work perfectly while under the ice. There is no hope of rescue 60 km in, with 500 metres of ice overhead,' added McPhail.

The international expedition was led by Dr Adrian Jenkins of British Antarctic Survey and Stan Jacobs of the Lamont-Doherty Earth Observatory, Columbia University, New York and used the American ice-strengthened research ship, the RVIB Nathaniel B Palmer.

After a test mission in unusually ice-free seas in front of the face of the glacier, they started with three 60 kilometre forays under the floating glacier before building up to 110-kilometre round-trips.

Jenkins said, 'The picture we should get of the ocean beneath the glacier will be unprecedented in its extent and detail.'

The ice shelf is 60 kilometres long and 35 kilometres wide. The shape of the seafloor and the ice shelf base are critical for working out how ocean circulations bring warm water under the ice causing it to melt.

'Autosub got as close to the grounding line as was possible,' said Jenkins. As the sub reached a bottle-neck, it was programmed to turn round once clearance above and below reduced to 100 metres.

'We cannot say precisely when the ice and seafloor would meet but we think we got within a few kilometres of the grounding line,' said Jenkins.

Lucky escape
Autosub had a lucky escape returning from the grounding line on one of its 30-hour missions. It is programmed to follow the base of the ice shelf out to the ship. But towards the back of the ice shelf just a few kilometres from the grounding line it seems Autosub ascended suddenly, probably into a crevasse. Realising something was wrong, Autosub switched to abort mode and rapidly descended before following a programmed emergency ice exit strategy.

'We didn't know anything was wrong until it surfaced and we saw its damaged nose,' said Jenkins.

The lead US researcher on the project, Stan Jacobs, is researching the Pine Island Glacier with International Polar Year (IPY) funding from the National Science Foundation (NSF).

How the ice sheets respond as global temperatures rise is one of the remaining major uncertainties in climate research.
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