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Thursday, August 11, 2011
Japan tsunami calved Antarctic ice shelf, Manhattan-sized iceberg broke off
An Antarctic ice shelf that had remained unshuffled for 46 years was broken by the Japanese tsunami in March, scientists have discovered. The Sulzberger Ice Shelf in the Antarctic registered the impact of the Japanese tsunami in 18 hours, when a huge iceberg began disintegrating and floating off to the Ross Sea.
A cryosphere specialist at NASA’s Goddard Space Flight Center and team have found that an iceberg the size of Manhattan island, 8,000 miles away from where the tsunami took its origin, was broken off in the impact, establishing for the first time the direct impact of devastating tsunamis on ice shelves.
According to the findings published in the Journal of Glaciology, the phenomenon marked the ""first direct observation of such a connection between tsunamis and icebergs.""
Using the European Space Agency Envisat data, the scientists observed for the first time that a Northern Hemisphere tsunami could trigger the calving of an Antarctic ice-shelf. While it was predicted that massive tsunamis can trigger calving of ice shelves, it was the first time that the phenomenon was proved. This will shed light into some unexplained phenomena in the past, scientists say.
""In September 1868, Chilean naval officers reported an unseasonal presence of large icebergs in the southernmost Pacific Ocean, and it was later speculated that they may have calved during the great Arica earthquake and tsunami a month earlier … we know now that this is a most probable scenario,"" NASA quoted a scientist as saying.
The Tohoku earthquake and tsunami that occurred on March 11, 2011 rumbled across the Pacific and Southern Oceans and reached Antarctica in less than eighteen hours. On reaching the region, it impinged on the Sulzberger Ice Shelf causing the calving of an iceberg almost the size of Manhattan.
""In the past we've had calving events where we've looked for the source. It's a reverse scenario - we see a calving and we go looking for a source,"" Kelly Brunt, a cryosphere specialist at Goddard Space Flight Center, said. ""We knew right away this was one of the biggest events in recent history - we knew there would be enough swell. And this time we had a source.""
The scientists say when the Japan tsunami interacted with the bathymetry of the Pacific Ocean basin, it reflected and refracted, adding to the complexity of wave arrivals along the coast of Antarctica that persisted for days.
(Source: International Business Times)