January 7, 2009
Researchers To Send Submarine Under Antarctic Glaciers
In an effort to seek clues to world ocean level rises in one of the most inaccessible places on earth, scientists are sending a yellow robot submarine to dive under an ice shelf in Antarctica.
A U.S. research vessel will launch the 22 ft submarine to 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.
Large icebergs have been breaking off Antarctica's ice shelves "” extensions of glaciers floating on the sea "” for years, but scientists have been unable to get beneath them to see how deep currents may be driving the melt from below.
Experts 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 defenses for coastal cities from Beijing to New York.
The rate of flow of the Pine Island glacier in west Antarctica has quickened to 2.3 miles a year from 1.5 miles in the mid-1990s.
Adrian Jenkins, leader of the "Autosub" mission at the British Antarctic Survey, said it has taken everyone by surprise. 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."
More than 90 percent of the world's fresh water is contained in Antarctica and would raise ocean levels by 190 ft if it were all to melt, which would take thousands of years.
World sea levels would rise between 7-24 inches by the year 2100, driven by global warming caused mainly by human emissions of greenhouse gases from burning fossil fuels, according to U.N. Climate Panel projections.
"Pine Island glacier and the glacier alongside, the Thwaites, are moving faster than any other glaciers in Antarctica," said Stan Jacobs of Columbia University.
"They are also accelerating," he said aboard the U.S. Nathaniel B. Palmer vessel in Punta Arenas at the southern tip of Chile just before the 54-day voyage.
Driven by 5,000 batteries of the kind used to power torches, the Autosub has a top speed of 3.4 knots, a range of 250 miles and can dive to 5000 feet.
The research vessel will also carry out other projects including tethering devices to the seabed to monitor ocean temperature, salinity and currents for two years.
The thinning of the shelf at Pine Island seems to be linked to a shift in deep ocean currents that are bringing warmer water from the depths and melting the ice. Scientists are still unsure as to why this is happening.
On the Antarctic Peninsula further north, several ice shelves have disintegrated in recent years apparently because of a 5.4-Fahrenheit warming of air temperatures in the past 50 years that may be linked to global warming. In much of Antarctica, temperatures are little changed.
Experts say 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. Shifts in winds might be causing currents to suck warmer water from deeper parts of the ocean.
The submarine takes sonar readings and measurements of the saltiness of the water under the ice and is the successor to one lost near the start of a similar mission in 2005 beneath an ice shelf in east Antarctica.
Steve McPhail of the British National Oceanography Center in Southampton who engineered the Autosub said people are surprised to hear that it's powered by 5,000 'D' sized alkaline torch batteries.
He said it is the most economical way of powering a submarine like the Autosub. The submarine is due to make at least six missions under the ice -- its route has to be programmed in advance but it can maneuver around hazards.
"The submarine is yellow because it makes it easy to spot when it surfaces, and its color has absolutely nothing to do with the Beatles song "ËYellow Submarine'," McPhail said.
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