(AFP) – Aug 9, 2011
PARIS — The tsunami that struck Japan on March 11 propagated waves that hit an ice shelf in Antarctica 13,000 kilometres (8,100 miles) away, smashing parts of it into huge icebergs, the European Space Agency (ESA) said on Tuesday.
On March 12, ESA's Envisat Earth-monitoring satellite spotted icebergs that had broken from the Sulzberger ice shelf, and on March 16, the pieces were seen floating into the Ross Sea, it said.
The largest berg measured about 9.5 kms (5.9 miles) by 6.5 kms (four miles), making it slightly bigger in surface area than Manhattan, and had a likely depth of about 80 metres (260 feet).
The tsunami was at least 23 metres (76 feet) high after it had been generated by an underwater quake of 9.0 magnitude, according to Japanese estimates published a week after the event.
Analysis of Envisat's radar pictures by experts in the United States suggests that the waves were probably only about 30 centimetres (18 inches) high by the time they had crossed 13,000 kilometres (8,100 miles) of ocean.
Even so, the rhythmic up-and-down movement was enough to stress the ice shelf's rigid structure, causing chunks to break off at its edge, ESA said in a press release.
Research that linked the tsunami to the iceberg calving was carried out by a team led by Kelly Brunt, an ice specialist at NASA's Goddard Space Flight Center in Maryland. Their study appears in an online publication, the Journal of Glaciology.
Ice shelves are thick floating beds of ice that are attached to the coastline. They are created by glaciers whose ice is discharged into the sea.
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