Japan tsunami broke off icebergs in the Antarctic

Welle still worked 14, 000 kilometers south on Sulzberger Ice Shelf

The photo taken on 12th March 2011 shows the beginning of the iceberg's replacement by the tsunami. © European Space Agency / Envisat
Read out

The Tohoku tsunami of March 11, 2011 not only devastated the coast of Japan, it also affected the Antarctic. This has been determined by researchers of the US space agency NASA using satellite images. Nearly 14, 000 kilometers south of its place of origin, the tidal wave broke off icebergs of twice the size of Manhattan from the Sulzberger ice shelf in the West Antarctic. According to the scientists, this is the first time that a tsunami has been observed "in flagranti" as a trigger for iceberg crashes.

As early as the 1970s, researchers speculated that a particularly large number of icebergs could arise when an ice shelf is repeatedly stretched by waves. Using models and water level measurements, glaciologists have calculated in several studies the possible influence of the swell on the ice. However, the direct observation of such an event did not succeed.

When the earth trembled and set off a tsunami off Japan on March 11, 2011, this was the chance Brunt and her colleagues had been waiting for. "We knew immediately that this is one of the biggest events in recent history. We knew there would be enough swell, "says Kelly Brunt, a glaciologist at NASA's Goddard Space Flight Center. Their team used tsunami models from the US Marine Research Agency NOAA to determine the path of the waves across the Pacific and the Southern Ocean. The Sulzberger ice shelf proved to be the most likely target, the researchers say.

The picture taken on 16 March 2011 shows the icebergs already broken off by the tsunami waves in front of the Sulzberger ice shelf. © European Space Agency / Envisat

Radar instrument documents Iceberg Demolition

"In the past, we were always looking for the cause in such events - this time we had the cause, " says Brunt. At the calculated time of arrival of the tsunami in the Antarctic it was cloudy, reports the researcher. Therefore, only the radar instruments of the Envisat satellite of the European Space Agency (ESA) were able to clearly depict the demolition of the icebergs on the Sulzberger Ice Shelf. The tsunami broke off two icebergs about six by ten meters in size, along with numerous smaller chunks.

18 hours have needed the wave from Japan to there, the researchers report. When he reached the ice plate lying on the sea, the tsunami was only 30 centimeters high. However, the sustained exposure to the thickening was sufficient to break the 80-meter thick ice at this point. The comparison with historical satellite images showed that the ice shelf at this location had remained virtually unchanged for 46 years. display

According to the glaciologists, the sea ice normally lying in front of the shelf could have protected it. As a result, the tsunami in December 2004 probably had no major impact on the Antarctic ice. By contrast, in March 2011, there were hardly any sea ice in this region. The events are at the same time further proof of how closely the various components of the Earth system are interconnected. Their findings have been published in the journal "Journal of Glaciology".

(NASA, 10.08.2011 - NPO)