Scientists trying to map the Pacific Ocean floor got an unexpected assist from the world's second-largest mammal.
Fin whale songs are usually treated as noise by seismologists because they muddy up data gathered at the bottom of the ocean. But new research published this month in the journal Science found the loud chirps that fin whales make have a similar effect to the advanced instruments seismologists use to peer into the Earth's oceanic crust.
Václav Kuna, a postdoctoral fellow at the Institute of Geophysics in Prague, made the discovery by coincidence as part of his doctoral research at Oregon State University. Kuna was searching through data related to an earthquake from seismic stations at the bottom of the ocean when he realized it included fin whale songs in addition to the movement of water waves.
Fin whale songs are one of the loudest sounds in the ocean at about 189 decibels — comparable to engines on large ships, he says.
Kuna says using whale songs this way seemed obvious to him and he’s surprised no one thought of the idea before. Biologists study whale calls but seismologists approach the vocalizations from a different perspective.
Seismologists often try to show what’s underneath the ground, and determine the thickness and seismic velocity of the Earth’s crustal layers, he says. This information applies to the oil and gas industry as well as other scientific applications such as geology and climatology.
This work requires a signal that travels beneath the ground, bounces off the Earth’s layers and is recorded by a receiver. Scientists use the time it takes the signal to travel from its source to the receiver to calculate the thickness and velocity of the crust, he says.
“The source is usually something that is called an air gun, which is like a quite large pressurized chamber,” he says. “But those are also very expensive. And also they create a lot of noise in the ocean that is being debated to be harmful for ocean wildlife.”
Fin whale calls are quieter with a more narrow frequency range compared to air guns, he says. Air guns penetrate deeper and produce a higher resolution picture of the Earth’s subsurface — but fin whales can still help seismologists.
Air guns are expensive and regulated for ecological reasons, he says, and whale sounds could help scientists navigate these roadblocks.
“The fin whales are just out there already and we have recorded so many of them,” he says. “And also we just don't need to create artificially those signals that may bother the wildlife out there.”
And the aid goes both ways: Kuna says seismological tools can also help biologists and conservationists study the endangered fin whales through tracking and estimating population quantities.
This segment aired on February 17, 2021.