The President's Adventures in Knowledge-Land Vol. 4 "Acoustics reveals secrets of glaciers and mammals in Greenland" video
The President's Adventures in Knowledge-Land is a series in which Hokkaido University president Kiyohiro Houkin, a neurosurgeon, visits fascinating researchers at Hokkaido University. The fourth installment, titled "Acoustics reveals secrets of glaciers and mammals in Greenland," features a discussion with Associate Professor Evgeny A. Podolskiy of the Arctic Research Center. They spoke about his contributions to cryosphere research, discussing how acoustics helps unveil the secrets of glaciers and the behavior of narwhals.
Entering cryosphere research
Houkin: First of all, could you tell me a little about your background and how you came to join Hokkaido University?
Podolskiy: I was born in Crimea, in Yalta, and I studied in an information technology special high school before graduating from Moscow State University in geography.
When I was a kid, I spent many years living on the coast of the Sea of Japan. So, I was always interested in what is behind the horizon and what life in Japan is like. Later, I came as an exchange student to Japan, and eventually, I got a degree from Nagoya University in geophysical research. So, I studied cryosphere, or the science of snow and ice. Then I worked for several years in Europe, again doing geophysics of snow. And, in 2015, I came here [to Hokkaido University].
Houkin: You have been studying geophysics and glaciology for a long time. Could you tell me more about your research?
Podolskiy: What I do is not traditional glaciology. Glaciologists usually look at very long timescales of years and hundreds of years and how things change with climate. In English, there is even a saying like "moving at a glacial speed," which means very slow.
Houkin: Glaciers are unbelievably slow, indeed. How can they measure that slow movement?
Podolskiy: Glaciers can actually move quite fast, and that is why my instruments are useful for detecting seismic signals or vibrations they produce. We can record the vibrations from very far away. The glacier I once worked on moved a meter or three meters in a day. This is a huge glacier, like kilometers long and kilometers wide, and there is so much going on inside of it. I'm interested in these quick processes which produce so-called "ice quakes." By listening to these vibrations, we can learn many things about glaciers.
Iceberg at Bowdoin Fjord, Greenland (Credit: Evgeny Podolskiy)
Listening to "Ice quakes" to understand glacier dynamics
Houkin: Could you tell me what you have learned so far from your research?
Podolskiy: I've been using seismometers for studying glaciers. We set seismometers on ice to listen to the inner life of a glacier, because there are many things we cannot see. Let me show you how it sounds if we transform these vibrations into sound. You will feel how it is on the glacier and then I will explain what's going on there.
Sound of glaciers recorded by sensors in the field in Greenland
Podolskiy: This was just a typical day on the glacier. The glacier is moving into ocean so fast at one to three meters a day, stretching itself a lot. For example, if the area is about the same length as Hokkaido University, the south end of Hokkaido University is moving away from the north end for five meters in two weeks, or two centimeters per hour. You can imagine what will happen to our university if it stretches for two centimeters every hour while we have this conversation. This will cause a lot of crevasses - big cracks in glacier ice - eventually breaking it down and producing huge icebergs. We can observe this with seismometers and count how many ice quakes happen every hour.
Houkin: What can you tell by counting ice quakes?
Large crevasse at Bowdoin Glacier, Greenland (Evgeny Podolskiy）
Podolskiy: For example, we count like 500 to 600 ice quakes an hour, which is very busy and noisy, and we see that the glacier is very sensitive to the ocean tide. When the tide falls for about two meters, the glacier speeds up and causes more stretching, more crevassing, and more ice quakes. It's like an explosion of sound. And when the tide is rising, the glacier slows down, and it becomes slightly quiet. We can study these damage dynamics by using sensors, which gives us ideas about, for example, the likelihood of iceberg collapse. That is impossible to understand without seismology.
Houkin: That might be something you can analyze using Fourier Transformation or some other sound transformation, right?
Podolskiy: Exactly! There is a perfect 12-hour cycle which we can detect with Fourier Transformation. Because the ocean tide has this cycle, when the tide is falling and rising, the glacier responds, and the cracks happen at a particular time. Actually, we know when it is possible to expect cracking, if we know the tide.
Houkin: I assume you work with many researchers in other fields. Do you have some mentors or teachers for your research?
Podolskiy: Sure. I came here as a postdoc of Sugiyama-sensei from the Institute of Low Temperature Science. He is a real glaciologist, not like me. I started to work with him by bringing different type of observations into the field campaigns we were doing together. So, he was one of my mentors on this journey.
No conveniences, no creature comforts
Houkin: I'm a doctor who used to work in a hospital, which is a very safe place. We have an earthquake sometimes, but it's a totally safe place. But your field is vast and dangerous, and the climate is very tough. Could you tell me how difficult it is to conduct field studies in Arctic areas?
Podolskiy: The world of fieldwork is difficult. If you didn't prepare something right or don't have some particular screwdriver or some little O-ring for your equipment, and because you're in the middle of nowhere, all your effort is screwed up. You cannot solve this problem in the field because all you have is with you. So, you have to prepare very carefully because you wouldn't have some shop nearby usually.
Houkin: No 7-Eleven at all.
Podolskiy: Yes. And no Seicomart. So, we have to prepare very carefully, and we also have to take care of our daily lives. We need to put up a tent, put a mobile toilet, and carry a gun to make sure that we can protect ourselves from polar bears. It can be not very comfortable not to have a shower for two to three weeks. So, it's a difficult environment, but I love it. It's much better than a comfortable office sometimes. It's challenging, but it's also very beautiful.
Applying acoustics to study Arctic animals
Houkin: You are also an expert in animal studies. What makes you interested in Arctic animals?
Podolskiy: Well, it was very simple, actually. It was "love at first sight." We go to glaciers in summer when the sea ice disappears and there are many cracks. This is exactly when whales can come, too. One day, when we were flying to a glacier by helicopter, I noticed that whales were also coming.
Whales are like mythological creatures. The one I study is called "Narwhal" in English. They are unique for having a tooth, and they're called "Arctic unicorns." Because they're very shy, you cannot approach them easily. When I saw them under our helicopter, I started to wonder, "Oh, what are they doing here?" and, "Oh, actually, the instruments I'm using for studying ice vibrations can also be used for studying whales."
So, we just leave our sensors in the area they live. When they pass by, they communicate and chat with each other. We can listen to the sounds and learn which species they are, when they are there, what they do there, and probably we can understand why. It's a passive observation without touching them.
Narwhals live in an extremely noisy environment
Houkin: From those observations, what have you learned so far about the animal?
Podolskiy: Well, let me show you some examples of the sound, and then I'll answer the question. I hope you can hear it because a lot of energy is in ultrasound. Let's test your ears.
Sound of Narwhals recorded in the waters off Greenland
Houkin: A high frequency? I doubt I can hear… Wait, I can hear the sound of narwhal. Wow!
Podolskiy: This was a sound that we could classify as narwhal. We know where it is, and we can also tell other things if we analyze the sounds more precisely. One of the findings is that, to my surprise, narwhals live in such a catastrophic, noisy place. The iceberg noise is one of the noisiest things in the Arctic Ocean, which can be heard with instruments 100km away. But, if I look into the high frequency of my signal, I hear the whales. It's their home, and it's alright for them. This doesn't stop surprising me. Animals don't like noise in general, but the natural ice noise is apparently not a big problem for them. They've adapted to it by somehow avoiding low-frequency bands and using high-frequency bands that are open for their communication in life.
Houkin: That's amazing. The relationship between noise and animal must be an interesting field to explore. Most people might think Arctic seas are very quiet, with no sound at all. But you just told me it's a very noisy world for the animals.
Podolskiy: Yes. In winter, when there is sea ice and all the motion of icebergs stops and glaciers slow down, it becomes very quiet. But in summer, it's a very noisy place.
Pod of six Narwhals (CC BY-SA 4.0 PJSC Gazprom Neft)
Life and lifestyle in Greenland
Houkin: Another interest is your life in Greenland. You told me that you have no Seicomart nor 7-Eleven, but you have to survive there. Could you tell me about your real life in the field?
Podolskiy: Sometimes we have a big group of researchers coming from Japan, sometimes, up to 15 - 20 people. It's very exciting because we have very different specialists. There are social scientists, biologists, oceanographers, glaciologists, and geologists. We usually stay in a small village, Qaanaaq, populated with about 600 people. What is unusual for me is that, because of polar day, it's always bright. Kids are playing outside at 3 a.m., which is very unusual in Japan. In summer, people have the opportunity to do things outside because it's bright and they really don't care about time. If the weather is good, they can do something like hunting, working, and constructing, and they keep doing it. It's quite amazing that it's their only chance to do many things before a severe winter season.
Besides narwhals, Podolskiy has used acoustics to better understand the ecology of little auks in Siorapaluk, Greenland. (Monica Ogawa)
Future direction
Houkin: I enjoyed learning about your research very much today. Could you tell me your plan for the future? What is your next goal?
Podolskiy: Well, my current goal is to have long term observations. Because the changes are taking time. For example, we wouldn't know if a new whale species comes or disappears, if we don't have long-term observations. I'm very curious about doing long term observations in the Arctic to document the changes.
Houkin: Before we conclude, could you tell us about the advantages for you to work at Hokkaido University?
Podolskiy: There are three things. First, Hokkaido University has the best and most beautiful campus in Japan. It's so green and I love it. Second, it has the Arctic Research Center which allows me to do incredible things and employs me. And third, I have such great partners here from very different disciplines where I don't know things they know. In collaboration, we can do very unique things in the Arctic. These reasons make my work and stay here quite pleasant.
Houkin: Finally, could you give some message to young students and researchers?
Podolskiy: The first thing is to believe in yourself and be confident. Your young mind has so many unique ideas, which may be quite original. And don't be afraid of learning new things because you can open new fields by doing that.
Houkin: Thank you very much. It's a wonderful message.
