Antarctica's Loose Tooth

Antarctica has a "loose tooth" and scientists are gathering loads of data to determine when, how, and why it will fall off.

The loose tooth is actually a partial rift in the ice. Eventually this rift will cut through the entire ice shelf, dropping an iceberg into the ocean - a process called "calving." The last time a significant chunk of ice broke off was in 1964.

Scientists from Scripps Institution of Oceanography at the University of San Diego have recently been studying both the long term and the short term behavior of these loose teeth.

With the help of NASA satellites and terrestrial GPS equipment, Helen Amanda Fricker of Scripps monitored the lengths of two rifts on the Amery Ice Shelf from 1996 to 2004. She found that while the rifts have widened steadily over the last five years, they widen much faster during Antarctica's summer months - December to March.

"There's a lot we don't know about how rifts propagate on ice shelves, but our conclusions give us some hints, including the finding that iceberg calving may be temperature dependent," Fricker said.

In the second study, Jeremy Bassis used GPS measurements and seismometers to monitor movements and vibrations of the tooth. He and his team found that the iceberg separated in bursts - sometimes as much as 600 feet over four hours - and would then normal, slow widening would occur for a period of 10 to 24 days.

Data from each study will help fill the rifts in scientists' understanding of iceberg calving.

"People have understood that rift propagation is an important phenomenon and now we have new data that can really take us places," said Jean-Bernard Minster, also of Scripps and a co-author on both studies.

--Bjorn Carey

Credit: Scripps Institution of Oceanography