UC Science Radio transcript: Episode 10

Dr Heather Purdie: Science on thin ice

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Molly Magid: Welcome to UC Science Radio, where we conduct interviews with a range of scientists to learn about the big issues facing our world and what science is doing to help. I'm Molly Magid, a Master’s student in the School of Biological Sciences.

Today I’m talking with Dr Heather Purdie. She’s a glaciologist in the School of Earth and Environment. Her research focuses on glacier mass balance, dynamics, and climate change. As a lecturer, she uses storytelling to engage with students and make her lessons come alive.

Kia ora Heather, welcome to UC Science Radio. I'm interested in what you do at UC, so what's your role and what's your research about?
Heather Purdie:
Tēnā koe, Molly. Lovely to be talking to you. I'm a Senior Lecturer in Te Kura Aronukurangi, the School of Earth and Environment, and I'm a glaciologist so my area of research expertise is studying glaciers and climate change. I'm also a general physical geographer, so I teach into a real broad range of undergraduate and graduate courses, teaching students about the environment around them.

What is a glacier and how do they form?
Glaciers are awesome! A glacier forms in places where each year, more snow accumulates than can melt away the following summer. This means you either need to be high in the mountains where it's cold, or down in the polar regions where it's also sort of cold and there's less solar radiation. Each year, you'll get a certain amount of snow falling in the mountains, some of that will melt away. But to get a glacier we need that each year a certain amount of that snow lasts, and lasts through the summer. Year after year, you get a little more snow accumulating than is melting away, and so over time that snow compresses down into ice, and over time, we eventually form our glacier.

Glaciers have this natural cycle of melting and retreating and then packing on the snow and growing back, but I know that climate change is changing how this process happens. Can you talk a bit about the natural cycles, and then what climate change is doing to change them and to accelerate this melting?
Yeah that's right Molly. As glaciologists, we're always telling everyone that glaciers are these awesome climate indicators. And they are, because we have this thing we call glacier mass balance: a glacier is always working to adjust its size and its volume to the current climate it's in. We have this “gaining snow, losing water” cycle going on and on. If the climate is cooling down, the glacier gets thicker, it gets fatter, it kinda gets longer. If the climate warms up, we actually start to lose more than we're gaining, so it thins and shortens. In natural cycles (like over the last two-and-half million years) we've had multiple "ice ages" or glacial periods, where glaciers have expanded around the Earth and then intervening times when they're retracted. At those really long time frames, those sort of cycles are related to the way Earth orbits the sun, the tilt of the planet, also things like large volcanic eruptions that can disrupt climate, sunspot activity, large scale weather systems like the El Niño Southern Oscillation, they can all alter our climate on scales that the glaciers will adjust to.

Certainly in more recent times, what we're seeing is, the climate is warming. The amount of fossil fuels humans are emitting into the atmosphere, we're seeing warming. So the glaciers will adjust. It's getting warmer so they're losing more mass than they’re gaining. So we're seeing them getting smaller and smaller. In some cases like Fox glacier, which I've been measuring for over twenty years, is shorter now than we've ever seen it before.

I saw that on the UC Science Facebook page, there was a video of you doing work at Tasman glacier and it looked really incredible. The thing you were studying was crevasses, and what impact they might have on melt rates. So my first question is what is a crevasse because I don't really know? And then, what are your hypotheses or ideas about how they may be influencing melt rate?
Yes, my latest very large research project I've got on the go, is exploring how crevasses affect melt rates of glaciers. I was really fortunate to get Royal Society Marsden Fast Start funding for this, so it's a great opportunity to explore the new idea. A crevasse is a part of the glacier just sort of essentially cracked open, split apart, so it's like a break in the surface of the glacier. We can think of glaciers a bit like viscous rivers, or you think of treacle or honey or something flowing down the mountains. The ice can actually stretch apart, and sort of compress back up as it's flowing over undulations. If it's not flowing too quickly, the ice can actually hold together with quite a lot of stress, you know it gets a bit skinny, it gets a bit squished up. But if we get to a point where the valley is steepening up quite a lot, and the ice gets stretched too quickly, what happens is that it will actually fail and break apart and that's what our crevasses are. We'll get crevasses in places like where the ice is flowing steeply or it's going around a corner. On the outside of a corner the ice gets stretched apart. So they're basically these holes in the glacier. But they don't go all the way to the bottom (despite what the movies may make you think), crevasses are often not necessarily as deep as people think. On average, they're only about 20 meters or so deep. They can get much deeper in polar regions, but on mountain glaciers, you know, 20 meters is a pretty deep crevasse.

My hypothesis of this research is thinking about how those crevasses influence the temperature of the glacier and the melt rates. We can think of the crevasse like in terms of making the surface more rough. Like if we have a rugby field or sort of flat green grass, and we think about how the wind blows over that rugby field. If the field's all smooth, it'll blow across quite normally. But if we planted a whole lot of trees on the rugby field (which I think would be quite cool, but I imagine the rugby players wouldn't think it was so cool), put a whole lot of native trees on the rugby field, that when the wind blows across that rugby field, it's going to create a whole lot of turbulence and disturb the wind. When we've got turbulence, that can actually increase melting on a glacier. I guess crevasses are a bit like holes down instead of trees up.

My hypothesis is that the way the crevasses disturb the surface may actually increase melt rates. It's quite new, we've got some pretty exciting field techniques, getting temperature sensors down crevasses. Certainly it's only really getting underway now, but we've definitely seen that the crevasses are often warmer than the surrounding ice. They do tend to be pooling warmer air, so that'll be really interesting to as the project evolves to see what the impact is. I guess one of the rationales for doing this, is that as our glaciers are getting thinner with climate change, we actually see more crevassing because as the ice gets thinner as it's flowing over the steeper parts, it tends to break up more easily. We tend to have less snow cover or the snow that falls on the glacier in the winter melts off more quickly in summer. So the crevasses are almost becoming a bit more frequent or are being exposed for longer. That's the rationale as to why I think it's important to try and understand what their role is. So yeah, it's all pretty exciting and gives me a good reason to get around the mountains for field work, so that's always a good thing too.

The video that I was talking about was taken with a drone. How has the drone technology changed the research that you do and do you think there's a potential for drone videos to be a way that people can experience glaciers when it may be difficult to go out and see them in person, especially as they keep changing?
Drones have actually been an amazing thing in terms of research. Back in the day, when I was measuring the length of the Fox Glacier, I would be walking around really close to the terminus with a little GPS and a little flouro vest on, managed safely but still not the most ideal way to do it. Of course now that we've got drones, I go to Fox Glacier with one of our technicians and we fly the drone and we get a fabulous map of the terminus. We can create these 3D models from the images that are taken with the drone. From a science perspective, they're really amazing in the way that they help us understand landscape change. But at the same time, they can be quite annoying when you're out tramping and someone's buzzing around with a drone. I think we need to be really mindful about how much we use drones, like use them when they're really an advantage and not use them just for the sake of using them.

Yeah in terms of field trips, that footage was amazing, wasn't it? I think definitely virtual field trips, I think they have a lot of scope. It's actually a really exciting area, particularly in our School of Earth and Environment. I'm actually at the moment working with a technical team to try and develop some virtual field trips because it is really hard to get large classes out into the field. Like where I used to take the students to Fox Glacier, there is no foot access there anymore. So trying to develop some virtual field trips is another way of getting that connection to environment I think is really important. But also I'm still just a real believer that while virtual field trips are amazing and definitely have a really important role that they can play, they'll never replace actually being there. You can create so much and things can be really, you know, in 3D, and quite realistic, but there's something almost intangible that you can't replicate with a video or a camera that you can only get by getting the students there and letting them touch it. I don't think virtual field trips will ever phase out real field trips, but they have an awesome role to play in supporting teaching and learning, and, you know, helping everyone get to the field, as well so for inclusion they're really awesome. But yeah, I'd never like to see a day where we don't actually get to go for a walk.

The way that these glaciers are melting and changing has changed how people can view them and how tourists can come and either go on the glacier or go to a viewing platform, and you've done work on this. So what are the changes that have been influencing how people can see the glacier and how have you worked with the Department of Conservation or tourist companies to work around what's happening?
: Yeah, that's actually one part of my research I really enjoy. There's this thinking about the implications of glacier retreat, or just glacier change, to how people interact with glaciers. As we've seen these glaciers getting shorter, there's a few different things going on. For example, over in Aoraki/Mount Cook National Park, we've got these very large sort of low sloping glaciers that are actually forming lakes at their terminus end. So at the end, where they sort of stop, now we've got this lake forming. It's been really interesting that the glaciers are getting harder to access from walking, but because we've got a big lake in front, there's some companies that have actually got people into boats and into kayaks and so they're taking tourists up to look at the glacier by utilizing the lake and we're seeing these lakes expanding. I do a lot of regular surveys of the lakes to look at how fast they're expanding and also we often have, near the terminus of the glacier, near the end, we have ice hidden under the water and that can present a hazard for these boat tours so we map that and communicate that to the companies.

Also, we see like over on the West Coast, the glaciers shrinking up the valley. Like I've said before, Fox is shorter than it's ever been before, so's Franz Josef. As the glaciers are retreating, they're not only getting shorter, but quite importantly, they also get thinner and what we find in these steep mountain catchments that it actually means they end up getting a lot of rock fall onto the surface because, you know, we've got very young mountains that are growing very rapidly so we end up with a lot of rock fall. That presents a hazard to people walking on the glaciers. The companies working over in the area, and the Department of Conservation, are having to constantly adapt where people go, how they go, how they're interacting with the glaciers to keep people safe. In some of our surveys over the years, we feed that information through to these companies just to help them with their decision making. We're seeing quite a loss of foot access or walking access onto the glaciers with the way they're retreating. So what's actually happening and one of the things that I've had a lot of interesting conversations with many people-- recreationists, mountaineers, tourists, tour operators, over the years, is about how they're adapting to that. We are seeing this increase in using helicopters to access the glaciers which I find a little bit ironic because we've got this fossil fuel usage that’s is contributing to the climate warming, and then we're kinda accessing the glaciers with the helicopters so it's kinda quite interesting.

You worked as a glacier guide. Can you talk about that experience and how it has influenced the work that you do today?
Yeah that's right. Before becoming an academic, I used to also work for the Department of Conservation as a ranger at Aoraki/Mount Cook and was really heavily involved in school group education, which was great, taking the kids out around the national park. I also worked as a glacier guide at Fox glacier and it's a fantastic job in that you're on the glacier every day, so you get this real sense of how dynamic it is, because every day you're walking up there with a different bunch of people and you're looking around and explaining to them how it works. As part of teaching philosophy too, I really want people to feel connected to the environment, and I think developing a connection to the environment is really important. Hence, you know, taking field trips and all those sort of neat things. Sometimes I used to feel like I achieved more for climate change education when I was a glacier guide. You know you've got these fifteen people wandering along behind you on the ice and you get them to walk through crevasses and touch the ice and when one they've had this really cool experience and start to understand what a glacier is, you also can engage in conversations with them about why glaciers are retreating. It was a really great chance to have that real face-to-face interaction and actually have people there breathing and touching and feeling the ice, and getting really into it. It's great.

Yeah, it sounds like you have this great connection to the glaciers and actually,  showing other people, being able to share that is pretty incredible. But how do you feel when you see and learn that these glaciers are retreating and changing and potentially disappearing? How do you stay positive in this work?
Yeah, that's the thing actually, for any of us working in teaching in the area of climate change, it's something we're quite mindful of and really mindful of our students, that your course doesn't end up being doom and gloom you know because things are changing and we're seeing unprecedented change in and around loss of snow and ice around the world. I think the thing is, you've got to focus on, take that positive thing that it's such a beautiful environment, it's an awesome thing to study and to inspire people to want to care for it. You have to stay positive because if you get too negative about it, people might just think: "Oh, the problem is too big. I can't possibly do anything about it." That's so not the thing, you know, there's millions of people, billions of people, on the Earth. If everyone actually does something, and thinks about their lifestyle and impact on the planet, then cumulatively that will get somewhere. So every person you can engage and connect and get them passionate about this, then that's a good thing.

I heard that you use a lot of storytelling in both your teaching and in just presenting about the glaciers to connect with people. What's that like and what are some of the stories you tell?
Yeah, I love telling stories! Particularly like Pūrākau, Māori legends and stuff which are awesome. It's all about creating this connection to what you're teaching, and you're in a lecture theatre or the classroom, and you’re trying to talk about Fox or Franz Josef glacier and Pūrākau, the Māori legend, about how they were formed is really awesome, you know. It's another way of thinking about the environment, not always just thinking about our landscape from a Western world view. One other thing that's really awesome about Māori culture, is how they view their maunga, their mountains, as ancestors, their awa. Engaging in some of those stories just kind of develops that respect for the environment. You're thinking of the mountains and the glaciers as ancestors, as part of your family, then I think you're going to look after them more. I also just love kōrero paki, just telling yarns. I do a lot of field work, lots of things go wrong in field work sometimes you know, losing drills down holes. So I like to share those moments with the students too because that helps take them out of the classroom to the field.

It's not just about me telling stories either, because it's really neat to get the students telling their stories and experiences. Because on the weekends, they all go out and explore their environment. The students that come and study geography are often out tramping or skiing, and so it's really good to get them to bring their stories into the classroom too because I think everyone loves a good story. Storytelling is actually a really underutilized technique these days. Many years ago there was a lot of storytelling, and then as we've got more digital and people often watch movies. We perhaps don't tell as many stories as we used to, so I think it's a cool thing.

I think in science too, there's this idea that you just present the facts and the equations and that's how you teach. But it's so much more engaging and perhaps will get more of an audience if you actually connect it to a story and bring it into life.
Yeah that's right. In glaciology, when we're doing anything in glaciology, we're measuring glaciers, we've always got to turn everything to water. Sounds a bit weird when you explain to your students, you've got to learn to turn snow into water and ice into water, because to measure change you've got to get a common unit. It can be a bit abstract and the equations we use for that, if you're not a really keen mathematics-orientated person, it can seem all a bit daunting. But if you actually get the students thinking about their experiences with snow, and their experiences with water and how different snow varies from place to place, and then you present the equation, then they kind of think: "Ah I can see why I'm doing this now." It actually can make the equations about how a glacier moves or how we measure snow, become not so daunting, because the equation's actually linked to the real world and real experiences they may have had, so yeah, it's a good way of doing it.

I think I might know a bit about the answer to this one, but what's the most fun or exciting part of your work?
I think when you're a glaciologist, field work is pretty exciting and fun, isn't it? It is really neat getting out and actually being in the environment, getting into the mountains. I'm a field-based glaciologist and I work a lot on observations, so for me as well, like, a lot of my research ideas and stuff developed by being there looking, watching, observing, measuring stuff and thinking about the processes as I see them. I'm definitely a very visual person, like if I'm walking around and looking at something, I'm thinking about how it works, whereas some people can kind of do that sort of thing just by reading. So I think being in the field is a really crucial part for the way my research develops and the way I develop research ideas, but also because it's really fun and it's that chance where you really get to engage everyone, and it's just so beautiful.

My last question is in one sentence, could you say why your work matters?
Because we only have one Earth, and so we need to look after it.

Well, thank you so much Heather. It was great to talk to you.
Thanks Molly. I've really enjoyed our chat today and it's great to get the opportunity to let people know what we're doing.

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