5 December 2012

Tsunamis in the sky

Posted by kramsayer

A tsunami warning sign in Thailand alerts people to move to high ground after an earthquake but monitoring of the atmosphere may provide an early alert for these dangerous natural disasters. (Credit: Gossipguy/Wikimedia commons)

High in the sky seems like an unusual place to look for a tsunami, a natural disaster created deep beneath the ocean’s surface. But an international team of researchers is scanning the atmosphere for signs of these hazards. Looking at the sky, they say, could help scientists and emergency response agencies improve warning systems before they see any problems on land.

The researchers picked up high-altitude tsunami signals when they used both satellite-mounted GPS systems and special land-based cameras. This technology may shrink warning times for these disasters, which can pummel coasts and lead to tens of thousands of deaths.

Earthquakes on the seafloor send a sudden wave of energy shooting upward to the water surface. The jolt creates a ripple on the water surface, which might be very tiny at its epicenter, but can snowbll into waves that are tens of meters high when they reach nearby coasts.

That swell of energy doesn’t stop at the water’s surface, says Giovanni Occhipinti, assistant professor at the Institut de Physique du Globe de Paris, who presented a poster Monday morning at the American Geophysical Union’s 2012 Fall Meeting in San Francisco. Energy from deep in the ocean thrusts itself upward into the atmosphere as sound waves or gravity waves, which are similar to waves in water but travel through the air.

“The energy is propagating everywhere, you can’t stop it,” says Occhipinti.

This big pulse of energy can briefly change the chemistry of the ionosphere – part of the Earth’s atmosphere that’s more than 80 kilometers (50 miles) above the earth – leaving a signal of the disaster.

Scientists have only been searching for signs of tsunamis in the ionosphere for about 15 years, says Occhipinti. The research he presented was part of a larger goal to test different technologies that might pick up these changes in the atmosphere.

His team looked at a number of tsunamis from 2004 and 2012. They found that GPS mounted on satellites and special land-based “Airglow” cameras pointed at the sky were able to pick up the signal of these atmospheric shifts. His team also created the first ionosphere map of the 2011 tsunami that struck Japan.

There are advantages to looking to the atmosphere.

With tsunamis continuously releasing gravity waves into the atmosphere as they whiz across the ocean, Occhipinti transformed the GPS or camera data into maps showing the path of a moving tsunami at 250 kilometers (155 miles) above the ocean.

Right now, tsunamis are commonly monitored using ocean buoys that are sparsely placed throughout the ocean. Using the buoys, tsunamis can take hours to confirm, Occhipinti says.

Gathering information from the atmosphere can reduce wait time to under an hour, he says. A small ripple in the water’s surface may go undetected by a buoy but that same signal becomes magnified in the atmosphere, says Occhipinti. Occhipinti wants more GPS satellites with their eyes on the ionosphere and hopes to attach more “Airglow” cameras to boats and aircraft to better capture the ocean’s movements in the skies above.

-Ryder Diaz is a science communication graduate student at UC Santa Cruz