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Making Waves: "Can a Tsunami Be Stopped in Its Tracks?" [ Show/Hide Article ]

Tsunamis happen all the time from undersea volcanoes, landslides, earthquakes—and even meteorites. Although warning systems can alert coastal residents about potential waves, just how destructive and dangerous they might be is hard to gauge. Until now, perhaps. A researcher from Cardiff University in Wales says the best way to understand a tsunami's potential impact is to "listen" to the wave itself.

In December 2004, a 9.3 magnitude earthquake struck off the coast of Indonesia, rupturing a trench in the Indian Ocean over 750 miles long. The tremor unleashed a tsunami with energy equal to several atomic bombs, and those waves raced toward coastlines at the speed of a jetliner. The wall of water eventually reached 11 countries and killed nearly 230,000 people—one of the worst natural disasters of all time. Unfortunately, there weren’t enough ways to warn coastal residents and tourists of the looming disaster, nor its gargantuan size.

050101-D-0000B-081 Right now the best predictor of tsunamis is something called "DART," for Deep-Ocean Assessment and Reporting of Tsunamis, which uses open-ocean buoys and coastal tide gauges. The network reliably detects tsunamis hours in advance and provides warning, but predicting their exact size and when they’ll occur is more challenging.

Until now perhaps. Dr. Usama Kadri, a lecturer of applied mathematics at Cardiff University, thinks the key to knowing the potential ferocity of a tsunami is to "listen," so to speak, to the wave itself.

He says when you have an event in the ocean such as a submarine earthquake, it releases a family of waves. That "family" includes the surface waves that we see, but also sound waves called "acoustic gravity waves."

According to Dr. Kadri, acoustic gravity waves travel at the speed of sound in the water, which means by the time a tsunami has traveled hundreds of kilometers, acoustic gravity waves already traveled more than a thousand. And being able to read those sound waves may give crucial extra time to evacuate areas because acoustic gravity waves carry valuable information about the properties of the earthquake and approaching tsunami, which can be employed in an early detection warning system.

Tsunamis happen all the time in the ocean and rarely result in a big monster wave as depicted in the movies. They’re actually a series of waves that can be caused by undersea volcanic eruptions, landslides, or even a meteorite plunging into the ocean. Most commonly though, tsunamis are caused by earthquakes.

And they vary greatly in size. Kadri suggests that by listening to the acoustic gravity waves with hydrophones, or underwater microphones, warning centers could read the data well in advance of the wave hitting the shoreline to know whether the tsunami will end up being a surfer’s dream—or a catastrophic nightmare.

Tsunami Warning Dr. Kadri says the technology exists and proposes a worldwide early detection system that could not only save lives, but millions of dollars in damage. But even with advance notice, once in motion, tsunamis can't be stopped. Or can they?

Kadri has done the math, and he thinks you could actually slow down or reduce an approaching tsunami by using its very own acoustic gravity waves—against it by taking the ones generated naturally by the very same earthquake, modulating them to the right resonant frequencies, amplifying them for an effective interaction, then redirecting them back to the tsunami.

Or, he says, we could "blast" the approaching tsunami with engineered acoustic gravity waves sent from the shore in order to slow them down. But Kadri is the first to say this would be an enormous engineering challenge because his calculations show the energy in the acoustic gravity wave would have to be the comparable to the tsunami, which is huge, impracticably huge.

Undeterred, his next step is to test his theory in the lab. But even if tsunami mitigation is still a dream, he’s got other potential uses for these waves. Remember we said a meteorite plunging into the ocean could generate acoustic gravity waves?

Kadri said they could be have been potentially useful in finding another object smashing into the sea—the missing Malaysia Airlines flight 370. When it hit the water, it likely created vibrations like a meteorite.

He’s not saying he can find that plane, but acoustic gravity wave theory could be a tool in future ocean impacts. Says Kadri, the ocean is a very noisy place. There are sound waves traveling all the time. And for that reason he will likely stay a very busy man. 💧

Published 15 March 2017 | © H2O Media, Ltd.




Making Waves: "Tea Time in the Wetlands"[ Show/Hide Article ]

What Can an Ordinary Tea Bag Tell Us About Climate Change? The Answer Could Be Steeped in Mud.

The kettle’s on the boil and we’re ready for some tea. But instead of dousing our favorite blend in hot water, a group of researchers in Australia would rather we take that tea bag and stick it in the ground—in the mud, to be precise. But don’t worry. They aren’t wanting the bags to go to waste. Burying them in places like wetlands and marshes is going to help the scientists understand how well those ecosystems store carbon. So, why tea bags?

According to Stacey Trevathan-Tackett at Deakin University in Melbourne, Australia, they're using tea because it’s in a little bag and they know how much is in there when they start, and they have standard decomposition rates. She says that if tea in the tea bag decays quickly it’s releasing more carbon dioxide into the atmosphere than if it breaks down slowly. If it decomposes more slowly, it’s storing more greenhouse gas in soils rather than letting it escape.

Blue Carbon Lab deploying tea bagsThe goal of the study is to identify wetlands around the world where decomposition rates are slower and then go and protect or restore those areas. To that end, they have people all over the planet burying tea bags in wet marshy areas and then they’ll map the data. Every few months they'll ask participants to collect some of their bags and they’ll analyze those to get an idea of what’s happening.

Most of us think of rainforests as places that absorb carbon from the atmosphere, but new research suggests that carbon stored in places like mangrove forests, tidal marshes, and wetlands—those places are twice as effective as forests in drawing carbon dioxide from the atmosphere—a process scientists call "sequestration." And the reason is because as trees and plants decay in a wetland, they generally sink underwater and eventually are covered by sediment, which limits the carbon from escaping. Although trees in a forest can harness a lot of carbon from the atmosphere to photosynthesize, when they die and decompose some of that carbon goes right back into the air.

But not every wetland is equal in its ability to sequester carbon and that’s the reason for the study. Wetlands vary according to latitude, climate, soil types, and whether they’re freshwater or saltwater.

Stacey says it’s a good opportunity to look at how all these things are affecting carbon cycling and carbon sequestration.

If we hurry. These valuable wetlands, which already provide much benefit like stabilizing shorelines and filtering water from pollutants are increasingly threatened by development. The bonus about their ability to slow climate change—it could be slipping through our fingers.

Stacey Trevathan-Tackett agrees that they're great no matter what. It’s just whether carbon sequestration can added to the list of the number of services they provide. So if you’re a professional—or citizen scientist, Stacey and her team would love your help in reading the tea leaves by putting tea bags in your local wetland. Visit their website at BlueCarbonLab.org for more information on how to sign up.  💧

Published 1 March 2017 | © H2O Media, Ltd.





Music Credits: 'Technology' by ANTARCTICBREEZE, Creative Commons  |  Masthead photo: Nick Maroulis, Creative Commons

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