A seismic (地震的；重大的) shift in climate science might be heating up.
New research shows that sound waves, produced by earthquakes can be used to measure temperatures in the ocean which traps 90% of the heat Earth absorbs from the sun，making long-term changes in ocean warmth, a major factor in how the world might respond to global warming.
For years the main approach of measuring ocean temperature has been Argo, an array (阵列) of 4000 automatic floats, which drifts the globe, sampling ocean water and measuring its temperature. Yet Argo measurements stop at 2000 meters.
The new technique called "Seismic Ocean Thermometry", would be especially useful in detecting long-term changes in ocean temperatures deeper than Argo's reach.
"Ocean Acoustic Tomography", the basis for the current research, was first tested nearly 30 years ago. The initial studies created sound waves artificially, basically increasing the volume on giant underwater speakers. Scientists measured the sound's travel time from the speakers to receivers thousands of kilometers away. Because ocean temperatures affect the speed of the waves, the researchers could calculate average temperatures along their paths. But some believed the noise was a threat to ocean life and the technique never took off.
The new study instead uses a natural sound source for investigation: earthquakes making a low, continuous noise beneath the seafloor off the coast of Sumatra that drum up sound waves in the ocean. On the shores of the Chagos Islands in the East Indian Ocean, between 2005 and 2016 Seismic Station Diego Garcia recorded seismic waves produced by those earthquakes. Some of those waves created physical changes in land and sea as they traveled. Others were sound waves or T waves that moved through the deep ocean, delivering valuable data about ocean temperature.
12 years of data coupled with mathematical models pointed to a temperature change of roughly 0.044 degrees per decade, a trend larger than those predicted by Argo. The findings suggest that Seismic Ocean Thermometry is a feasible method to measure changes in ocean temperature. Further data from other regions of the globe and other timeframes would help improve the warning models and predictions.
And in future studies the researchers plan to listen directly for sound waves, using a network of hydrophones, microphones which detect sound waves under water. Sound waves set the tone for a deep dive into our warming oceans even if they fail to reach 60000 miles under the sea?
