What's the News: The tsunami that deluged Japan in March was so strong that it broke off several large icebergs in Antarctica, 8,000 miles away, researchers report in a new paper [pdf]. Using satellite images, the researchers saw the tsunami causing new icebergs to split off---or calve---from an ice shelf, the first time such an event has been observed. How the Heck:
Once the tsunami began, the researchers predicted what course it would likely take through the Pacific.
The tsunami swell reached Antarctica about 18 hours later, by then measuring only a foot high. To get a clear view of whether the tsunami would cause any calving, the researchers used images from NASA and European Space Agency satellites and watched the swell hit the Sulzburger Ice Shelf in close to real time.
The scientists saw several large pieces of ice---totaling nearly 50 square miles, or twice the size of Manhattan---calve from the ice shelf. The largest of these icebergs was 7 miles long and 4 miles across.
What's the Context:
Scientists have long suspected that tsunamis can snap off bits of Antarctic ice, but they'd never before watched it happen. Up until now, researchers have looked at icebergs and worked backward to deduce what events likely caused them to break away from an ice shelf.
This also illustrates, as one of the researchers points out, the vast scale on which Earth systems are connected: an earthquake triggered a tsunami which sent icebergs adrift, nearly a day later and a hemisphere away.
Reference: Kelly M. Brunt, Emile A. Okal, & Douglas R. MacAyeal. "Antarctic ice-shelf calving triggered by the Honshu (Japan) earthquake and tsunami, March 2011." Journal of Glaciology, published online August 8, 2011. [pdf]Image courtesy of European Space Agency/Envisat