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Undersea Earthquakes Reveal Sound Warming Info

by Scientific American
November 30th 2020
Travel time differences for sound waves produced by undersea earthquakes in the same place at different times can provide details about ocean warming.
it wouldn't be the holiday season if there wasn't candy right. Celebrate the holiday season with the holiday crush. They've sprinkled candy with the holiday theme and fun packed challenges every week for five whole weeks, finishing on January 4th. The more challenges you complete, the better your chances of unwrapping delicious rewards. So are you ready to crush the holidays? Play the holiday crush now downloaded from the APP Store, Google Play or Windows Store. For free terms and conditions, apply Thistles. Scientific American, 62nd Science. I'm Julia Rosen, Tow us humans. Climate change feels like something that's happening to the atmosphere, but most of the action is actually at sea. About 90% of the heat that gets trapped by greenhouse gasses is absorbed by the ocean. So it's it's really important to track that energy in the climate system and track the warming off the ocean. You're in Kelly's, an

oceanographer at Caltech. Of course, the ocean is really big, and taking its temperature is hard. Satellites give information about the surface, and scientists have launched drifting devices that measure conditions in the upper mile of water. But researchers still struggle to collect data from the deep ocean and to detect the long term trends underlying day to day variations in temperature. Now, however, scientists have developed a new technique that allows them to measure temperature changes across entire ocean basins. The idea dates back to the 19 seventies, when researchers first proposed using sound waves to study ocean warming because the speed of sound through water depends on the physical properties of that water, which are related to temperature. And roughly, if we warm up the ocean temperature by one degree, the son of speed change, it would be 4 m past account. And this is that This is a very sensitive change when Bo Wu, a seismologist also at Caltech, who led the study

that one degree he mentioned is a Celsius degree. Researchers originally proposed using artificial sound sources, but that notion got next because of concerns about the impacts on marine animals and the new study. However, Woo, Kallis and their colleagues show that they can use the sounds produced by earthquakes instead, in an earthquake, some vibrations bounce off the sea floor and turn into sound waves that get picked up by seismometers and underwater microphones. The researchers looked at the travel times of these sound waves for 2000 pairs of earthquakes that occurred in the East Indian Ocean between 2005 and 2016, each earthquake pair happened in the same place but at different times, allowing the researchers to measure how much the sound waves sped up. The analysis revealed that the waves traveled a few 10th of a second faster in more recent quakes than older ones, a difference that translates to a warming trend of 0.4 degrees Celsius per decade. 4 1/100 of a degree may not sound like a lot, but it represents a huge amount of heat, considering

it's the change in a body of water almost 2000 miles wide and several miles deep. The warming is also substantially higher than the rate reported in previous studies, although Kelly says not to put too much stock in those discrepancies. We don't know whether that is the general finding. Whether that only occurs here in this in this region, a too this time, or whether that is, you know something. We'll find another regions as well. Way just don't have the data yet. The study is in the Journal science. Kallis and Woo say this approach may even enable scientists to gauge historical temperature changes by studying data from much older earthquakes. In other words, you could say that the method is sound. Thanks for listening for Scientific American 62nd Science, I'm Julia Rosen.

Undersea Earthquakes Reveal Sound Warming Info
Undersea Earthquakes Reveal Sound Warming Info
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