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Robot sub to probe melting glaciers
By Alister Doyle |
January 11, 2009, Sunday
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A YELLOW robot submarine currently docked at a port in Punta Arenas, Chile, will dive under an ice shelf in Antarctica to seek clues to world ocean level rises in one of the most inaccessible places on earth.
The seven-meter submarine, to be launched from a US research vessel, will probe the underside of the ice at the end of the Pine Island glacier, which is moving faster than any other in Antarctica and already brings more water to the oceans than Europe's Rhine River.
Scientists have long observed vast icebergs breaking off Antarctica's ice shelves - extensions of glaciers floating on the sea - but have been unable to get underneath to see how deep currents may be driving the melt from below.
They are now stepping up monitoring of Antarctica, aware that any slight quickening of a thaw could swamp low-lying Pacific islands or incur huge costs in building defences for coastal cities from Beijing to New York.
The rate of flow of the Pine Island glacier in west Antarctica has quickened to 3.7 kilometers a year from 2.4 kilometers in the mid-1990s.
"It's taken everyone by surprise," Adrian Jenkins, leader of the "Autosub" mission at the British Antarctic Survey, said just before leaving last week after preparations in Chile. The submarine cost several million dollars to develop.
"If you just make measurements at the ice front all you have is a black box," Jenkins said. "What we are doing is observing what is going on within the box."
Antarctica holds more than 90 percent of the world's fresh water and would raise ocean levels by 57 meters if it were all to melt, which would take thousands of years.
The UN Climate Panel projected last year that world sea levels would rise between 18 and 59 centimeters by the year 2100, driven by global warming caused mainly by human emissions of greenhouse gases from burning fossil fuels.
"Pine Island glacier and the glacier alongside, the Thwaites, are moving faster than any other glaciers in Antarctica," said the ice breaker's chief scientist, Stan Jacobs of Columbia University in the United States.
"They are also accelerating," he said aboard the US Nathaniel B. Palmer vessel in Punta Arenas at the southern tip of Chile just before the 54-day voyage.
Pine Island, Thwaites and the nearby Crosson glacier add 0.25 millimeters a year to global sea levels - 2.5 centimeters over a century even if unchanged.
The Autosub, driven by 5,000 batteries of the kind used to power torches, has a top speed of 3.4 knots, a range of 400 kilometers and can dive to 1,600 meters.
The Pine Island ice shelf is about 400 meters thick at its seaward edge on the Amundsen Sea.
Other projects the research vessel will carry out include tethering devices to the seabed to monitor ocean temperature, salinity and currents for two years.
At Pine Island, no one knows why the thinning of the shelf seems to be linked to a shift in deep ocean currents that are bringing warmer water from the depths and melting the ice.
On the Antarctic peninsula further north, several ice shelves have disintegrated in recent years apparently because of a 3 degrees Celsius warming of air temperatures in the past 50 years that may be linked to global warming. In much of Antarctica, temperatures are little changed.
Whatever the causes, glaciers may slide off the land more quickly if ice shelves vanish, adding water to the ocean and nudging up sea levels.
"You have to start worrying whether the system is speeding up, moving ice more rapidly into the ocean than it was even 50 years ago," Jacobs said.
The submarine, which takes sonar readings and measurements of the saltiness of water under ice, is the successor to one lost near the start of a similar mission in 2005 beneath an east Antarctica ice shelf. It is yellow to enhance its visibility.
The seven-meter submarine, to be launched from a US research vessel, will probe the underside of the ice at the end of the Pine Island glacier, which is moving faster than any other in Antarctica and already brings more water to the oceans than Europe's Rhine River.
Scientists have long observed vast icebergs breaking off Antarctica's ice shelves - extensions of glaciers floating on the sea - but have been unable to get underneath to see how deep currents may be driving the melt from below.
They are now stepping up monitoring of Antarctica, aware that any slight quickening of a thaw could swamp low-lying Pacific islands or incur huge costs in building defences for coastal cities from Beijing to New York.
The rate of flow of the Pine Island glacier in west Antarctica has quickened to 3.7 kilometers a year from 2.4 kilometers in the mid-1990s.
"It's taken everyone by surprise," Adrian Jenkins, leader of the "Autosub" mission at the British Antarctic Survey, said just before leaving last week after preparations in Chile. The submarine cost several million dollars to develop.
"If you just make measurements at the ice front all you have is a black box," Jenkins said. "What we are doing is observing what is going on within the box."
Antarctica holds more than 90 percent of the world's fresh water and would raise ocean levels by 57 meters if it were all to melt, which would take thousands of years.
The UN Climate Panel projected last year that world sea levels would rise between 18 and 59 centimeters by the year 2100, driven by global warming caused mainly by human emissions of greenhouse gases from burning fossil fuels.
"Pine Island glacier and the glacier alongside, the Thwaites, are moving faster than any other glaciers in Antarctica," said the ice breaker's chief scientist, Stan Jacobs of Columbia University in the United States.
"They are also accelerating," he said aboard the US Nathaniel B. Palmer vessel in Punta Arenas at the southern tip of Chile just before the 54-day voyage.
Pine Island, Thwaites and the nearby Crosson glacier add 0.25 millimeters a year to global sea levels - 2.5 centimeters over a century even if unchanged.
The Autosub, driven by 5,000 batteries of the kind used to power torches, has a top speed of 3.4 knots, a range of 400 kilometers and can dive to 1,600 meters.
The Pine Island ice shelf is about 400 meters thick at its seaward edge on the Amundsen Sea.
Other projects the research vessel will carry out include tethering devices to the seabed to monitor ocean temperature, salinity and currents for two years.
At Pine Island, no one knows why the thinning of the shelf seems to be linked to a shift in deep ocean currents that are bringing warmer water from the depths and melting the ice.
On the Antarctic peninsula further north, several ice shelves have disintegrated in recent years apparently because of a 3 degrees Celsius warming of air temperatures in the past 50 years that may be linked to global warming. In much of Antarctica, temperatures are little changed.
Whatever the causes, glaciers may slide off the land more quickly if ice shelves vanish, adding water to the ocean and nudging up sea levels.
"You have to start worrying whether the system is speeding up, moving ice more rapidly into the ocean than it was even 50 years ago," Jacobs said.
The submarine, which takes sonar readings and measurements of the saltiness of water under ice, is the successor to one lost near the start of a similar mission in 2005 beneath an east Antarctica ice shelf. It is yellow to enhance its visibility.
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