To us humans, climate change feels like something that’s happening to the atmosphere, but actually about 90% of the heat that gets trapped by greenhouse gases is absorbed by the ocean. Of course, the ocean is really big, and taking its temperature is hard. Now, however, scientists have developed a technique that allows them to measure temperature changes across entire ocean basins.
The idea dates back to the 1970s, 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 Celsius, the sound speed change－it would be four meters per second. And this is a very sensitive change.” said Wenbo Wu, a seismologist at Caltech, who led the study.
Researchers originally proposed using artificial sound sources, but that proposal got prevented because of concerns about the impacts on marine(海洋的) animals. In the new study, however, Wu and his colleagues show they can use the sounds produced by earthquakes instead. In an earthquake, some vibrations(振动) bounce off the seafloor and turn into sound waves that get picked up by a special machine and underwater microphones. The researchers looked at the travel times of these sound waves for 2,000 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 tenths of a second faster in more recent quakes than in older ones—a difference that translates to a warming trend of 0.04 degrees Celsius per decade. “0.04 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 2,000 miles wide and several miles deep.” said Wu.
【小题1】What does “a technique” in paragraph 1 refer to?| A．Trapping greenhouse gases. | B．Using artificial sound waves. |
| C．Measuring the width and depth of the ocean. | D．Employing the sounds of quake vibrations. |
| A．The sea is vast enough. | B．The statistics are accurate. |
| C．The equipment is advanced. | D．Each earthquake pair is conditional. |
| A．The sound waves slowed down with time. |
| B．The ocean temperature went up in the decade. |
| C．The speed change of sound waves was considerable. |
| D．2,000 pairs of earthquakes occurred in the same place. |
| A．Ocean Warming: A Booster of Climate Change |
| B．Seaquake Soundwave: A Tracker of Ocean Warming |
| C．Sound Waves: An Initiative in Studying Ocean Animals |
| D．Ocean Basins: Where Earthquakes Frequently Happen |
