海底地震声波可以揭示气候变暖

This is Scientific American's 60-second Science, I'm Julia Rosen.

这里是科学美国人——60秒科学系列，我是克里朱莉娅·罗森。

To us humans, climate change feels like something that’s happening to the atmosphere.

对我们人类来说，气候变化感觉就像大气层正在发生的事情。

But most of the action is actually at sea—about 90 percent of the heat that gets trapped by greenhouse gases is absorbed by the ocean.

但大部分活动实际上是在海洋中进行的-大约90%温室气体捕获的热量被海洋吸收。

“So it’s really important to track that energy in the climate system and track the warming of the ocean.”

“所以跟踪气候系统中的能量和海洋变暖是非常重要的。”

Jorn Callies, an oceanographer at Caltech.

加州理工学院的海洋学家约恩·卡利斯说。

Of course, the ocean is really big, and taking its temperature is hard.

当然，海洋真的很浩瀚，测量它的温度是很困难的。

Satellites give information about the surface, and scientists have launched drifting devices that measure conditions in the upper mile of water.

卫星提供了海面的信息，科学家们已经发射了漂浮装置，用来测量水面上一英里的情况。

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.

但研究人员仍在努力从深海收集数据，并检测气温逐日变化背后的长期趋势。

Now, however, scientists have developed a new technique that allows them to measure temperature changes across entire ocean basins.

然而，现在科学家们已经开发出一种新技术，可以测量整个海洋盆地的温度变化。

The idea dates back to the 1970s, when researchers first proposed using sound waves to study ocean warming

这个想法可以追溯到20世纪70年代，当时研究人员首次提出使用声波来研究海洋变暖

—because the speed of sound through water depends on the physical properties of that water, which are related to temperature.

-因为声音在水中的传播速度取决于水的物理性质，而水的物理性质与温度有关。

“And roughly, if we warm up the ocean temperature by one degree, the sound speed change—it would be four meters per second. And this is a very sensitive change.”

“粗略地说，如果我们把海洋温度升高1度，声速就会改变--那就是每秒4米。这是一个非常敏感的变化。”

Wenbo Wu, a seismologist also at Caltech, who led the study.

领导这项研究的，也是加州理工学院的地震学家吴文波表示。

That one degree he mentioned is a Celsius degree.

他提到的那个温度是摄氏度。

Researchers originally proposed using artificial sound sources, but that notion got nixed because of concerns about the impacts on marine animals.

研究人员最初提出使用人造声源，但由于担心对海洋动物的影响，这个想法被否决了。

In the new study, however, Wu, Callies and their colleagues show they can use the sounds produced by earthquakes instead.

然而，在这项新的研究中，吴文波、卡利斯和他们的同事表明，他们可以使用地震产生的声音来代替。

In an earthquake, some vibrations bounce off the seafloor and turn into sound waves that get picked up by seismometers and underwater microphones.

在地震中，一些振动从海底反射回来，转化为声波，被地震仪和水下麦克风接收。

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.

研究人员观察了2005年至2016年间发生在东印度洋的2000对地震的声波传播时间。

Each earthquake pair happened in the same place but at different times, allowing the researchers to measure how much the sound waves sped up.

每对地震都发生在相同的地方，但发生的时间不同，这使得研究人员能够测量声波加速了多少。

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.

分析显示，最近的地震比以前的地震传播速度快零点几秒——这一差异转化为每十年0.04升温摄氏度的变暖趋势。

Four one-hundredths 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 2,000 miles wide and several miles deep.

0.04度听起来可能不是很多，但它代表着巨大的热量-考虑到这是一个近2000英里宽、几英里深的水体的变化。

The warming is also substantially higher than the rate reported in previous studies, although Callies says not to put too much stock in those discrepancies.

变暖的速度也大大高于之前研究报告的速度，尽管卡利斯表示不要太看重这些差异。

“We don’t know whether that is the general finding—whether that only occurs here in this region at this time—or whether that is , you know, something we’ll find in other regions as well.

“我们不知道这是不是普遍的发现--目前是否只在这一地区这个时间出现--还是我们在其他地区也会发现。

We just don’t have the data yet.”

我们只是还没有数据。”

The study is in the journal Science.

这项研究发表在《科学杂志》上。

Callies and Wu say that this approach may even enable scientists to gauge historical temperature changes by studying data from much older earthquakes.

卡利斯和吴文波说，这种方法甚至可以让科学家通过研究更古老的地震数据来测量历史上的温度变化。

In other words, you could say that the method is sound.

换句话说，你可以说这个方法是合理的。

Thanks for listening for Scientific American's 60-second Science. I'm Julia Rosen.

谢谢大家收听科学美国人——60秒科学。我是朱莉娅·罗森。