An array of underwater microphones catalogues the sounds of marine mammals, such as bowhead whales and bearded seals, near the Bering Strait

NSF's Weather or Not!

An array of underwater microphones catalogues the sounds of marine mammals, such as bowhead whales and bearded seals, near the Bering Strait

National Science Foundation


What lies beneath...the sounds of the deep dark ocean

Interviewer: Charlie Heck

Interviewee: Kate Stafford

[Beluga whale sounds]

Charlie: No, don’t adjust your radio channel, it’s not static, nope this is not an alien invasion either. These my friends, if you listen carefully, are beluga whales, singing just for you!

Charlie: Okay, well maybe not just for you, but close enough. When researchers drop a fancy microphone deep down, you’ll hear a whole other world, it’s pretty busy down there, and thanks to research funded by the National Science Foundation, we can listen in too.

Kate: You know these are animals who have evolved to do everything under water and it’s got to be almost everything by sound and so they are incredible signal processors. It—it really fascinates me they use their sounds to look at their migratory patterns and their population differences and to be able to essentially have a window on to this underwater world that is otherwise completely opaque to us.

Charlie: That’s Kate Stafford, a Principal Oceanographer at the Applied Physics Lab at the University of Washington. She studies arctic marine mammals using a hydrophone, an instrument with an underwater microphone that records and archives data on a hard drive, it sits underwater for about a year, collecting the sounds of the ocean.

Kate: If you look out on the landscape, all you see is ice and some open water and you might think that there are no animals out there whatsoever but once you put a hydrophone or an underwater microphone into the water, you hear the trills of bearded seals, you hear the songs of bowhead whales and you hear beluga whales. So you can hear all these species out there and know that even though you can’t see them, they’re out under water somewhere and that’s the real value of using passive acoustic monitoring, so eavesdropping, for animals under water is you can hear them over much greater distances than you can see them. You can listen for them even if you have 100 percent ice cover or 24 hours of darkness or a really rotten storm, things that would preclude a traditional survey which might be a visual survey such as looking for animals from a plane or from a large ship.

Charlie: So, I know what you’re thinking, wow super cool, but besides hearing these amazing sounds, what’s the benefit to listening in on these animals?

Kate: You can hear them whenever they make sounds and you can listen to them year-round. For instance, we can monitor the timing of the migration of beluga whales and bowhead whales as they move north from the Bering Sea into the Arctic for the summer and again as they move south. But what I’ve really been focusing on recently is the movement of subarctic or summer whales, say, into the Arctic. We can listen for fin whales and humpback whales and killer whales on our data and what I’ve heard is that these animals are now occurring much later in the season than we think they’ve ever occurred. So we get humpback whales singing north of Bering Strait and killer whales sometimes well into November when in the past the seasonal sea ice would have pushed them south much sooner. During October and November, there are very few opportunities to get out and do a sighting survey or an aerial survey of this region so, really, acoustic monitoring is the only way to understand that these animals are occurring – where they’re occurring and when they’re occurring.

Charlie: Kate’s trips can last anywhere from 7 days to well over a month at sea. So I asked her to delve into the great and not-so-great aspects of ocean research.

Kate: My favorite parts about going to sea, even on these really long cruises, is you never know what you’re going to see. There’s always something new and surprising. It might take days to see something but suddenly you’ll come across, say, a polar bear on an ice flow or a bunch of walrus, I realize that I’m incredibly fortunate to go to these places, these parts of the world, whether it’s the Arctic or the Antarctic where I’ve also worked, you know, these remote distant places that are so vibrant in people’s imagination and I get to experience being there and that’s really exciting. Even when the weather is rotten there is something invigorating about being out at sea. On the other hand, sometimes being at sea can be incredibly tedious. The weather might be bad for long stretches of time; the ship might be really crowded with people. It’s amazing how the quality of the food on the ship can impact everybody’s mood. (Charlie giggles) So, that can be a little bit difficult and just being away for so long, particularly on the very long cruises, it can be a little bit isolating, I think.

Charlie: Kate and her research team are interested in the Bering Strait -- the ocean gateway linking the Pacific and Arctic oceans, that’s where she does her research. As sea ice is melting, the strait is getting more and more traffic, and I’m not talking about whale traffic, I’m talking about manmade traffic…

[Ambient noise sound]

Kate: the Bering Strait was the end point for both the northern sea route and the Northwest Passage so people are hoping to send a lot of commercial ships up through this passage in order to reduce the time it takes to get goods and services from Europe to the Pacific.

Kate: In addition to monitoring animals, one of the main reasons we put hydrophones out is to monitor what we call ambient noise levels and we can detect ships and we can detect air guns and so I have a post doc who is looking at can we hear increases in noise levels due to shipping through the passages, through the Bering Strait. And why that’s important is, you know, certainly compared to a major port such as, say, Boston or Los Angeles, there are relatively few ships going through Bering Strait but that’s due to increase and we do know from work on the East Coast that increases in ship noise tend to decrease the communication range of large whales. Think about, if suddenly a truck came through my office, I would have to practically yell to hear you or it would really be hard for you to hear my responses because that truck in my office would be masking my voice. The same thing happens under water with large whales. We think that this increase in low frequency noise, so ships make very low frequency noise, think a bass drum versus a tenor. But that’s the same frequencies that whales use so by increasing this low frequency noise, we might be reducing the communication space of these animals. Mostly marine mammals, they use sound to navigate, to find food, to communicate, to keep in contact with each other so for them, sound is the most important sense and anything we do to make it more difficult for them to use that sense may have impact on their behavior. One of the things we’re studying is looking at what are sort of baseline ambient noise levels now and what will they be in the future if, in fact, the northern sea route really opens up and we start getting a lot of commercial vessel traffic through Bering Strait.

Charlie: Alright, let’s recap, Kate is listening in on “what lies beneath” the ocean, and it’s pretty loud down there. There are all sorts of marine life, using sound to communicate with each other, find food and migrate, so I had to ask her, has there been any wow, really moment in her research?

Kate: There’s been a couple. In the Bering Strait region, we do have humpback whales migrating north of the strait, probably to feed. The Pacific population of humpback whales seems to be increasing. It’s very healthy. But what I wasn’t expecting was to have them stay so late in the season that they start to sing. You know, we traditionally think about humpback whales as migrating to Mexico or Hawaii or islands off of far southern Japan where they reproduce and they breed and the males produce this elaborate song in the winter. But now we’re getting song north of the Arctic Circle even in the winter so these animals are staying later and they’re also singing. But the other really, really cool thing that I’ve been working on and that just still kind of takes my breath away is bowhead whales also sing. Their songs are different from humpback whales and they’re incredibly variable and they produce many, many different songs every year and then they produce completely different songs the next year. With humpback whales all the males in a population will sing the same song in a season. That song might change but everybody changes their song as the song changes so everybody is singing the same song. Bowhead whales, on the other hand, are incredibly variable. I sort of think of humpback whales as being the set classical musicians whereas bowhead whales, they’re jazz musicians. You never know what they’re going to do and they seem to improvise and it’s just fascinating.

Charlie: Let me hit ya with the classics first, [humpback whale sound] and now how about some smooth jazz [bowhead whale sound]. Well, I’m going to defer to Kate’s music review on this one.

Charlie: And in case you forgot, Kate Stafford is an NSF-funded oceanographer at the University of Washington, studying the underwater world passing through the Bering Strait, and how creatures in that world communicate through the sounds they make.

Charlie: I’m Charlie Heck, co-editor of NSF Science360 News Service and co-host of the Super Science Show, at the National Science Foundation.

Charlie: If you have any questions about this story or suggestions for interviews about super cool NSF-funded science write a letter, put it in a bottle and drop it in the ocean, I’ll get it eventually, I’ve got friends in the deepest depths after this one or you could just email me at