Three months after NASA dropped 90 rubber ducks into holes in Greenland’s fastest-moving glacier to track the melting of Arctic ice, there’s no sign of the toys.

The duckies were deposited into moulins (tubular holes) in the Jakobshavn Glacier in mid-September by Alberto Behar, a robotics expert at NASA’s Jet Propulsion Laboratory in Pasadena, Calif. The idea was that the ducks would float along the same channels that melt waters do, and wherever they emerged would reveal the path of the disappearing ice. 

The ducks have Behar’s e-mail address stamped on them, along with the word "reward" in three languages, including Inuit. NASA is offering $100 to the first person who locates a duck, London's Guardian newspaper notes.

“We haven't heard anything from them yet," Behar tells the BBC. "If somebody does find one, it will be a great breakthrough for us." 

Also MIA is a GPS ice-tracking system that Behar deposited in the moulins along with the ducks. It hasn’t phoned home, either.

"We did not hear a signal back so it probably got stuck under the ice somewhere," Behar told the BBC. "It was a bit of a long shot, but we thought it was worth a try. We've got to go back and scratch our heads and think about what we do next."

The melting of Greenland’s ice sheet is considered a harbinger for climate change on Earth. The Jakobshavn Glacier discharges nearly 7 percent of all Greenland ice, and may be the source of the iceberg that sank the Titanic in 1912, Australia's Sydney Morning Herald reported in September. As global warming melts the Jakobshavn and other glaciers there, ocean waters may rise.

Image of rubber duck by iStockphoto © Thomas Vogel