Japan quake shifts Antarctic glacier

March 15, 2011 by Anil Ananthaswamy

The major earthquake that hit Japan on Friday caused a massive ice stream in Antarctica to momentarily speed up.

As the surface seismic waves generated by the quake travelled around the world, they appear to have given the Whillans ice stream in West Antarctica a nudge, causing it to shift by about half a metre.

The movement was picked up by Jake Walter of the University of California, Santa Cruz, and his colleagues, who monitor the glacier remotely from California. They say the event is an "interesting insight", but are not suggesting it will destabilise the West Antarctic Ice Sheet in any significant way.

The Whillans ice stream drains ice from the West Antarctic Ice Sheet into the Ross Ice Shelf. Since 2007, Walter and colleagues have been using GPS field stations on the ice sheet to monitor its movements. They have shown that the ice stream speeds up twice a day in slip events which last about 30 minutes.

The glacier normally creeps along at an average speed of about 1 metre per day. But during a slip event, it slides almost half a metre in one go. The sudden slips are related to the tides, and are strong enough to generate seismic waves that are recorded by stations at the South Pole and the Antarctic Dry Valleys (Journal of Geophysical Research, DOI: 10.1029/2010JF001754).

 

Slipping glacier

Now it looks like the magnitude 9.0 earthquake that shook Japan last Friday caused the glacier to slip in a similar way.

When Walter and his colleagues were analysing GPS data from the ice stream on Monday, they noticed that one slip event had happened earlier than expected. Further analysis revealed that it happened exactly when surface seismic waves generated by the Japanese earthquake would have hit Antarctica.

Large earthquakes are known to create seismic waves which can circle the planet several times before dying down.

"The Chile earthquake from last year also had a similar effect" on the Whillans ice stream, Walter told New Scientist. "It's an interesting insight into how large earthquakes might affect glacier motion."

Walter and colleagues now want to examine data from other large earthquakes to see if any others are linked to slip events of the Whillans ice stream.