A tsunami's icy reach

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Aug. 14 2011 7:09 AM

A tsunami's icy reach

The March 2011 earthquake and subsequent tsunami off the coast of Japan did unimaginable damage. The tsunami was several meters high, marching a long way inland, and wiped out entire towns.

It also swept out to sea, expanding across the planet. By the time it hit the Antarctic ice shelf -- 13,000 km away, taking less than a day -- it was well under a meter high. But water is dense (a cubic meter weighs a ton!) and that much of it hitting the ice can cause it to flex and break.

Phil Plait Phil Plait

Phil Plait writes Slate’s Bad Astronomy blog and is an astronomer, public speaker, science evangelizer, and author of Death from the Skies!  

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[Click to antarcticenate.]

That's the Sulzberger ice shelf on the coast of Antarctica and the Ross Sea. A few days before this image was taken those gigantic blocks of ice were still part of the shelf (though cracks were already present), and in fact the big one had been part of the shelf for over four decades at least. The pounding wave of the tsunami broke up the shelf, sending those blocks into the sea.

Mind you, that big rectangular block of ice is about 11 km (6.6 miles) across -- about the size of Manhattan! The total ice broken off probably doubles that amount. It was about 80 meters (260 feet) thick from top to bottom, too, so we're talking a lot of ice -- about 100 billion tons worth all told!

This image, but the way, is not an optical photo. It's actually a radar map from Europe's Envisat Earth-observing satellite. Radar bounces off of water differently than it does off ice, distinguishing the two in images. Maps like this are critical in understanding how the ice changes in the south polar regions, and that of course is critical in understanding the changing environment of our planet.

[Note: after I drafted this post, I found that NASA made a video explaining it:

Nice, and really shows how massive this event was.]



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