September 22, 2008

Researchers Deploy Rubber Ducks To Track Melting Glacier

A U.S. rocket scientist sent 90 rubber ducks into the ice of the fastest-moving Greenland glacier, hoping someone finds them if they emerge in Baffin Bay.

Alberto Behar of NASA's Jet Propulsion Laboratory in California, said the common yellow plastic bath toys are one part of a sophisticated experiment to determine why glaciers speed up in the summer in their march to the sea.

Researchers say the Jakobshavn Glacier is very likely the source of the iceberg that sank the Titanic in 1912 because it discharges nearly 7 percent of all the ice coming off Greenland. As the planet warms, its melting ice sheet could make oceans rise this century.

"It's a beautiful place to visit. You can watch these icebergs continuously march across and fall into the ocean," Behar said.

However, you can't see how melting water moves through the ice.

Behar said right now it's not understood what causes the glaciers themselves to surge in the summer. One theory is that the summer sun melts ice on the top glacial surface, creating pools that flow into tubular holes in the glacier called moulins.

The moulins can carry some water all the way to the underside of the glacier, where it acts as a lubricant to speed the movement of ice toward the coast. But because it cannot be seen, no one really knows what occurs.

Therefore, the rubber ducks containing a probe about the size of a football loaded with a GPS transmitter and instruments can tell much about the glacier's innards.

Behar flew by helicopter in August to a place on the glacier where rivers of melted ice flow into moulins. Researchers lowered the probe into one moulin by rope and released it into the water flowing beneath the ice.

They also released the flotilla of rubber ducks, each labeled with the words "science experiment" and "reward" in three languages, along with an e-mail address.

If the ducks are found and somebody e-mails the discovery, it would tell scientists where the water ends up.

But the probe could tell much more.

It would first signal its position via GPS. Its pressure and temperature sensors would supply information. And an accelerometer -- which records how much things speed up or slow down -- could point to waterfalls or cascades, features that would make the probe, and the water, go faster.

Behar hopes a fisherman or hunter might find a duck or the probe but so far nothing has turned up.

He said they haven't yet heard back "but it may take some time until somebody actually finds it and decides to send us an e-mail that they have found it."

"These are places that are quite remote so there aren't people walking around."

Behar is a creator of robotic rovers for NASA and often tests vehicles meant for space in hostile places on Earth. He worked with Konrad Steffen of the University of Colorado, an expert on Arctic ice and the Greenland ice sheet.

According to Steffen's website, Greenland dominates the land-based ice in the Arctic. If all land-based Arctic ice melted -- which is not expected -- it would correspond to a sea-level rise of about eight yards (meters).

This is different from the melting of Arctic sea ice, which dropped to its second-lowest level ever this year. Sea ice has little impact on sea level rise.


Image 2: Retreat of the calving front of the Jakobshavn Isbræ 2001-2004, West Greenland. Source: Nasa Earth Observatory


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