Episode 039: Josh Thienpont
Dr. Josh Thienpont is a paleolimnologist from York University's Faculty of Environmental and Urban Change. He studies inland aquatic ecosystems in the Arctic to understand what the distant past of lakes and streams can tell us about how climate change is affecting the Arctic. His work is crucial for understanding the effects of humanity on the very waterways on which human life depends.
Transcript
Cameron: My guest today is Dr. Josh Thienpont, a paleolimnologist from York University's Faculty of Environmental and Urban Change. Dr. Thienpont studies inland aquatic ecosystems in the Arctic. He looks at what we can learn about the distant past of lakes and streams, and what that tells us about how climate change is affecting the Arctic. I hope you enjoy our conversation. Josh, welcome to the podcast.
Josh: Thanks for having me, Cam.
Cameron: I want to ask you about this word, paleolimnology, because it's got a lot more syllables than it ought to have. Let's break it down into pieces. What is limnology?
Josh: Yeah. It's a great place to start. Limnology is the study of inland waters. So that means lakes, rivers, streams. The things we think of most commonly, but also wetlands reservoir. So artificial lake ecosystems. Anything that's wet and not the ocean is a part of limnology. And that includes fresh water, which we're most familiar with, but also technically inland saline waters.
Cameron: You mentioned the oceans. When I think of global warming, the first thing that comes to mind is the ice caps melting. And there goes Venice, there goes Miami, all these low line coastal cities. So what's the link between global warming and these inland waters?
Josh: Yeah. And that makes sense. It should. Most of the water on our planet is in the marine environment. So it's not surprising that people jump towards saline ocean waters when they're thinking about the planet as a whole, but also the impact of climate change. And a lot of the similar kinds of changes you would expect to see in the Marine environment that we predict are going to occur are also likely to impact inland water. So warming of the ecosystem that can be really important for stream ecosystems, which tend to be cooler flowing, changes in the way in which the organisms live in those locations. And from a human perspective, because we can't really do a lot from consumption, with salt water, it's really important, even though it's a small piece of the whole water pie on the planet to understand fresh water in particular, which is in lakes, and streams, and those kinds of places.
Cameron: In one of your papers that you wrote with your co-author and colleague at York, Jennifer Korosi, you've got this line that says, "Arctic near-surface air temperatures warmed by more than three degrees between 1971 and 2019, three times faster than the global average." So there's certainly something going on in the Arctic with warming and that's affecting the lakes.
Josh: Yep. That's exactly right. If you have this average temperature changed on the planet, some places are going to warm earlier, some places are going to warm more. And the high latitude areas, both in the Arctic and the Antarctic — which I'm not as familiar with, but also has similar types of amplification — are experiencing those changes earlier for a variety of different reasons related to the circulation of the atmosphere, related to feedback associated with the presence of ice and also just related to changes in the seasonality. So in the North, we're seeing really rapidly warming winters which are important for making the next summer quite cold. So it's a positive type of feedback system. But in general, yes, the Arctic has been warming. It started to warm earlier and is warming faster than more temperate locations. And we know how much those areas are changing. So it's quite significant up North.
Cameron: So that's the limnology part. Tell me about how "paleo-" fits into this.
Josh: From a definition, it's pretty straightforward. Paleo means old or ancient. And so that's just old limnology, though that maybe doesn't do it fully justice. But the idea is that for most locations that you go to in terms of any area, whether you're measuring temperature, whether you're measuring the water, chemistry, any of those things, we really don't know that much about how they've changed over time. People weren't measuring temperature in lake waters, even around us in Southern Ontario or wherever you're listening from, 100 years ago. We always say this for pH, which is how acidic the water is. The function for pH to measure was only invented — or come up with, it's not really invented, but ... in 1909. So it was impossible to measure the pH of waters in 1850. There was no modern analog to do that. And in the North there, there's just not that many people around all of these ecosystems to measure them, to study them in a modern context. So we need to be able to infer how those ecosystems have changed. And paleolimnology uses the sediments, the mud at the bottom of the lake to reconstruct and infer changes over long time scale, sometimes tens of thousands of years, depending on the lake where we are missing those monitoring data.
Cameron: So you're studying the layers of sediment. What's your primary means of looking at those? What's the technology involved?
Josh: Well, it really depends on how much sediment ... what the sediment looks like and how much sediment you want to retrieve. So the sediment builds up continuously all day, every day throughout the entire year. Even under the winter ice, a little bit of material is filtering down. It collects the stuff that's in the lake, what we call autochthonous material, but it also collects the stuff that comes in from outside of the lake, what we call allochthonous material. And some of those things are transported, not just locally or regionally, they're transported globally like contaminants and things like that. And if you go out to a lake right now, it's kind of mid-June, and the pollen is absolutely horrible in the Northern hemisphere. Anyone is suffering allergies and you see that yellow scum on the top of the lake, that's all those pollen grains from all of the area around the tree settling down into it. How you get that sediment out really depends on how much sediment you want. So for things like looking at recent climate warming, you may only need to get the top 30, 40, 50 centimetres of sediment accumulation representing, depending on the location, 100 to 200 years. And you can do that basically in the same way that you drink from a straw, is the analogy we always use. So if you take an open straw and you put it into your liquid and you cap it with your finger and pull up that straw, you get a plug of the liquid. And our sediment cores for the watery stuff in the recent past do exactly the same thing. We send down an open tube, we use a messenger, something that we drop down to the bottom to trigger some sort of closing mechanism, that's your finger going on top of the straw, and then we pull up that mud and take it away. For longer records, if we want the entire history of this lake going back to the beginning of the Holocene or even longer for some lakes, the sediment gets much coarser, much thicker, at the bottom because it's losing its water as it's compacting. And so you have to push a rod into it, but the concept is the same. We're sucking the sediment out with some sort of mechanism.
Cameron: Once you've got this kind of core sample, when you ... do you have to freeze it to make sure that it stays in the right layers or ...?
Josh: That's a good question. It really, again, depends a little bit. The thicker stuff that you get from these tubes that you push down into the deep sediment will hold its form. You can cut them in half in the lab and then you can do things with them. And it's kind of the consistency of modeling clay or something like that. Those ones. The watery material at the top is 80 to 90% water by weight. So it doesn't hold its integrity on its own. And you do need to do something with that. So you can freeze it, that's one option, and then slice it into little intervals that you then put into bags. And so you have that record. The other thing I tend to use just because freezing things in situ is a little bit of a logistical headache and it's also quite hard in the Arctic where you may not have access to really cold materials like dry ice and that kind of thing, we use a type of what of approach that's called vertical extrusion. So you push from the bottom of the core up into some sort of tray and you scrape off a little bit of the material. So you would take the top half a centimetre representing a couple of years, 10 years depending on the lake, and put that into a bag. And then you push it up a little bit more. So you are basically cutting the pieces of the sediment core going down, and down, and down into the bottom in known intervals that represent this stratographic order of the core. And then when you get back to the lab, you can do all sorts of stuff with them.
Cameron: Right. So you end up with this record that you can analyze of the different layers of the different years of the past.
Josh: Exactly. And we have good methods for dating those. Most people are familiar with carbon-14 radiocarbon, which is used for older sediments because of its longer half-life. And in the more recent times, we use other radio isotopes to date how old the sediment is and tell us what year this interval represented. So if we see this big change starting in 1960, we would know that maybe this is related to some sort of enhanced warming that's going on.
Cameron: One of the things you've studied in the past is the effects of mining on our inland waters. So are using the same sorts of research methods then to get these core samples in the lakes and you're looking for what? Specific toxins or ...?
Josh: Yeah. That's a good question. So in more Northern regions, mining tends to be one of the more kind of large scale damaging types of activities. Not all the time, but as with any industrial activity, especially in a more pristine landscape, there can be deleterious impacts. So in the North, that's something that has happened historically and is ongoing and is a concern to understand the environmental changes. And the methods are the same. That's right. So you would access these sediment cores. No one was measuring the concentration of contaminants associated with mining for a mine that started in the 1930s. There was just no knowledge that was ongoing. So we can use these sediment cores to reconstruct that past. And what it is in the actual mud that you look like really can depend. There's a record of the physical environment. So how coarse or fine the sediment is, how sandy it is versus how fine grain clay it is. It can tell you about processes that are bringing material in. You can look directly at chemical remains. So how much metal concentrations are there. If you're looking at a mine that is a metal mining type of activity and you see the increase in this metal contaminant in the sediment, you might infer that was as a result of the mine or you can look at the biological remains of different organisms, small organisms, generally microscopic things to tell you how the ecosystem itself has changed over time if you see a change in the algal community or the zooplankton community, the invertebrates.
Cameron: Is there an annual cycle or something in the sediment that allow you to distinguish the different years similar to the bands in a tree?
Josh: Some lakes do have what we would call annual laminations, or "varves" is the term for them, where you do see visible repeated banding representing yearly conditions. That is not the case in most lake ecosystems. If you look at a sediment core, you won't be able to see a tree ring chronology. The individual yearly bands. It takes specific kind of conditions for those to form. Sometimes they're there, but you can't see them. So under an X-ray or a CAT scan. People take these cores and put them in medical devices at hospitals. You may actually find that there is lamination, but most of them don't have that just because there is some sort of internal microscopic mixing within a given year. But in the sediments, it may still be recording that historic changes. And if you take small enough slices, you may be able to reconstruct those things, but that's often used for more specific kind of process-based questions. At a scale of looking at say how a mine impacts the lake, we tend to be okay with the resolution that we get from a little bit course or sampling because before the mine, versus the height of the mining activity, versus post mining, we can really tease apart those differences, even at that resolution.
Cameron: I'm just curious about the mechanisms by which toxins can get into the lakes because you've got obviously stuff that could come from a mine that's nearby, but potentially you could get toxins coming in that were airborne from other continents even, like maybe the nuclear meltdown in Japan might have created an effect in the lake. What are the different ways that the toxins get in?
Josh: All of those things exactly. So you can have direct spills. So in the catchment of the lake or the release of tailings, which is the mine wastes that are often kept in pools nearby to detoxify.
Cameron: Familiar with that from Fort McMurray.
Josh: Yeah. Right, yeah. And we've done some work in the downstream area of the oil sands in Canada. So that can be one way. There can be the airborne release. So our mining work we did around Yellowknife related to the Giant Mine, which some people are familiar with either from its deleterious ecological impacts or the history of labor that went on there. It was really obviously an important facility. For many, many years, they opened and roasted the material that they took out of the ground to get the gold out of it. And when that roasting happened, they released an incredible amount of arsenic into the environment, just in the air, in the local area. And that settled out on the landscape, including the lakes. But we do have contaminants that are globally transported. Mercury is a great example of that. Mercury, just based on its chemistry, depending on the species of mercury, will transport long distances in these hopping kind of events as cold distillation as it moves to the North. So even though there's no local source of mercury from the combustion of fossil fuels, from artisanal gold mining, any of those kind of activities that are sources of mercury to the environment, we find mercury in the Arctic because of this global cycling of the material. And radiation is another great example of that. One of the things we actually use to date our sediment is radio isotopes of caesium-137. It's a non-natural isotope. So we find it in the sediments because of nuclear bomb testing. And so we see a peak of it in the '60s when the peak of atmospheric weapons testing occurred during the cold war. But in some locations, we see a second peak in the '80s associated with the Chernobyl accident. And you would see smaller scale examples of that from other activities.
Cameron: You're using an interesting combination of methods here because you've got to get right out into the field of the Arctic to get your samples, but then you've got to come back and have the disciplines of lab technology in order to analyze all these samples.
Josh: Yeah. I find it a really great combination. I like the field based work, I like to see the sites. You often combine that with modern limnological sampling. So go and measure the water chemistry and the biology that are currently in the lake and then record the sediments and bring it back to the lab and use a range of different techniques to infer the change you're interested in, whether that is ... And which techniques you use really depends on the question you're interested in.
Cameron: You've also done a lot of work around permafrost thaw. What are the concerns here? Obviously global warming is going to have a huge impact as you mentioned on the ability of the permafrost to be regenerated each winter. What are the concerns for the environment?
Josh: Yeah. So permafrost thaw is what I did my graduate work on. And it's what my research is really interested in moving forward. It's where my primary focus is in the Arctic at the moment. And permafrost is really an interesting component of the high latitude environment of our planet. More than half of Canada is underlain by permafrost. We are a permafrost nation, even though most people don't have that much direct contact with it. And just for the simple definition, it's ground that remains frozen for two or more consecutive years. So on top of the permafrost is that material that thaws every summer, every spring and freezes back every winter. And below that, there's material that never thaws. It is always frozen. But a simple definition doesn't really get at the complexity of it because what that permafrost is made up of really has a strong impact on what happens when it eventually does thaws associated with climate change. It's just rock that's really, really cold and stays cold. When you warm up a rock, it doesn't really change. It doesn't contribute any water. It's just no longer frozen, but if it's water, mud, all of those kind of what we would call ice rich permafrost and really fine grain stuff, when you thaw that, all sorts of things can happen. You can get flows of materials. So landslide type of materials, you can get substance where it settles and you get ponds forming or lakes forming in the space where this permafrost was. So the nature of the permafrost is really important. And being that the Arctic is changing so rapidly, it's a material that is really in a state of flux and has a real potential to impact and degrade on the landscape.
Cameron: So it's not just this widespread gentle fine. You actually get these dramatic shifts of the landscape. There's a word that you used in one of your papers. The word is "thermokarst." Can you explain that?
Josh: Absolutely. So that is exactly right. Sometimes thaw can be gradual and occur over long time scales, and sometimes it can be quite catastrophic. So thermokarst is broadly where you have the substance or the sinking of the ground for some reason due to the thaw of ice rich permafrost. I think in Alaska, they've identified 14 different forms of thermokarst, but one of the ones I'm most interested in is what are called thaw slumps. So there are geomorphic disturbance. They occur on slopes. So on the edges of lakes, which is where my interest comes in on the edges of river systems, on the coastal areas. If you see pictures of — on CBC, for example — of permafrost thaw in Canada, it's probably a thaw slump on the Arctic ocean coast because they are massive. You can land planes in them. They're so big sometimes. And when they occur, you can get very rapid mass movement like you would with a large landslide, except it's not a water and significant precipitation. It's thawing of the ice, although they are accelerated by rain, which is one of the things we're learning.
Cameron: When I lived in BC, you sometimes have a massive rainfall and a huge landslide coming out from the side of a hill or down a water course of some sort. This is something that's happening right out in the middle of the Arctic just on a much more gentle terrain than the coast of BC and yet you're still getting these dramatic almost mudslides.
Josh: Yeah. A slump is a type of slide in the geomorphology definition and they can be quite catastrophic. There are some in the foothills of, for example, the Richardson mountains, where there is a little bit more of that slope terrain that are massive, where the pieces of thawed material, the size of school buses that they fill up valleys. We just don't see them really because there's not as many people in those areas, but they can be really catastrophic. And what we're finding is that they have a really important role to play in understanding the thaw of permafrost more broadly, but also for impacting the lake and other aquatic ecosystems that they're occurring on the shores of.
Cameron: These are hugely important topics that you're addressing. They've got huge economic and environmental implications. Where is your research going now? You shared a research grant proposal with me that is looking at lake sediments. Tell me about that.
Josh: They are very important. One of the really critical things that's from an infrastructure perspective. So understanding the stability of the landscape more broadly for things like roadways. The Inuvik–Tuktoyaktuk Highway was just completed a few years ago. This is this grand project that's been envisioned in Canada for many, many years to connect all three of the oceans finally. So you can now drive from anywhere in Canada to the Arctic ocean. So it's really important. And there are other infrastructure pieces like pipelines and things like that run through permafrost terrain. So understanding stability at a very big scale is quite important. And one of the things I'm starting to realize, as I started by saying there that all permafrost is not created equal. And so what has happened to the permafrost in the past is important for what's going to happen in the future. We can learn things about the past to tell us about future changes that are going to happen and be able to better predict the likelihood of permafrost thaw, the potential for failure, and what then happens to the ecosystem when permafrost is thawing. And that's what I'm interested in doing. So using sediments to go back in time from a methodological perspective. I haven't invented a time machine yet though, that would be nice, to find out about the changes that occurred when the permafrost thawed perhaps in the past, including in the very distant past and use that to tell us about if it's more likely to thaw now, what will that look like. Because this has happened in the past. There are periods of the history of the environment that have been quite analogous to what they're like now. So one of the things I'm really interested in is going back to this period of the early Holocene called the Holocene climate optimum, or Holocene thermal maximum — they have all different names depending on the literature you read — which was this period about 8,000 years ago that was quite warm. And we know from some of our work that on the terrestrial environment, that it was a period of pretty rapid permafrost thaw, at least in the McKenzie Delta area because it had already lost its ice from the glaciers. So using the lake sediments going back very far into the past 8,000-plus years to come up with this long history of these lake ecosystems to see what the changes to the landscape looked like when this thaw happened in order to predict what's going to happen moving forward as we get into this enhanced climate warming that we're at the leading edge of.
Cameron: So you developed some sort of a model of what might happen based on what you see in the ancient records of the sediment in those lakes.
Josh: Yeah. That's exactly right. Yeah. Permafrost that has thawed previously tends to not thaw as much again. So if we know that thaw was very, very significant in the past at a landscape level, that will lead into the fact that maybe it's actually not as primed for significant failure going forward as we may assume. If we just assume that it's virgin permafrost in some ways, that it hasn't had this history, there's this legacy of previous changes to the permafrost that all feed into how likely it is to thaw moving forward. These are the same models or the same kind of assumptions about our landscape that feed into global climate models because we assume there's this much carbon, there's X amount of carbon in the permafrost, tied up in permafrost globally, but that doesn't get any of ... at any of this complexity. We don't know is this likely to thaw, has this thought before, is not going to be as likely? Those are really important for refining some of the predictions about global climate changes associated with the permafrost aspect of it. There's all the other things about sea ice and those kind of ideas, but from a permafrost perspective, knowing what's happened in the past is really quite important.
Cameron: You're going to have to explain this mechanism to me. I don't understand why if it's thawed before, it's more resistant to thawing again.
Josh: It is a little counter-intuitive in some ways. And one of the ways we know that there's this period where there was really deep thaw is because as you go into the older permafrost, which is built up from the past, there's areas that have lower amounts of water in them. They tend to be drier in nature because that water thawed away before. We call them thaw unconformities. There's areas in the permafrost that have this legacy of the fact that they lost some of that water in the distant past. So because water is so important for modern thaw and the impact that it has at a landscape level, historic thaw events can precondition the landscape to be a little less susceptible to this catastrophic failure when future thaw occurs. It is pretty counter-intuitive.
Cameron: It sounds like an immune response.
Josh: It is a feedback mechanism in the exact same way.
Cameron: Any chance of being able to inoculate some permafrost, by kind of pre-thawing it and then freezing it again?
Josh: [laughs] That's a good question. There's all sorts of geotechnical, sort of engineering, applications moving forward. And in building types of activities, those are the kind of things that are, are incorporated into thinking about where you establish, for example, the footings of buildings that are being built in them or of a pipeline. Yeah. There is lots of interesting stuff.
Cameron: Tell me about what happens to your research findings after they leave the lab, so to speak. How does it get out into policy, or industry, or local community knowledge?
Josh: All are critical part. I have some really strong collaborations that I've worked on for many years since my graduate days with government researchers in the Northwest territories, especially at the Northwest territories, geological survey. Permafrost scientists who are really quite familiar with this area. And that feeds into a network at the territorial science level that connects to the geomatics. So the mapping, the hazard identification part connects to environment, natural resources, the road infrastructure, and those sorts of things. So feeding this research results into the government scientists who are responsible understanding and then implementing some of these changes is a critical part. Community engagement and working with the Inuvialuit and Gwichʼin communities who are both have their traditional territories in the Western Arctic is really important. We're getting to a point where a lot of the research is strongly connected to the human resources in that location and getting a great amount of capacity building in the community to continue some of this research and do that research. And that's something that came out of COVID a little bit as people had to figure out how to do research when they couldn't go there. And really the buildup of some of this capacity over many years has been really successful in doing that and will continue to going forward.
Cameron: One of the ways that our research gets out into the world is through our students. What kinds of courses are you involved with?
Josh: Yeah. Absolutely. So having students go into the field is a great part of research. I don't know. I've done it enough times, take it for granted, flying around in a helicopter in the Western Arctic. You forget just how amazing it is. And you are reminded of it when students who have never been up there, perhaps have spent their entire time in Toronto, go and get to do that for the first time. And it really makes this connection that is irreplaceable. And they then take that they have that understanding and that interest in the location, in the environment, and they take that into other places. So that's the first part and connecting them with the community is integral part of that experience as well. And then they can take that to their societies, to their specific societies for young researchers in permafrost science and those kind of things. All great networks to get into for graduate students and feed that into the research that they'll continue to do into the future.
Cameron: You've also got your own kind of hands on way of distributing your insights into this. I understand you've got your own podcast.
Josh: I do have my own podcast. Yes. It was one of those things that we started just before COVID and then had all these great ambitions to go to conferences and do all sorts of live interviews. And I think we'll hopefully still get there, but right now it's become a little more of an educational thing. It's called "Core Ideas: The Paleolimnology Podcast." Done with a good friend from graduate school of mine, Adam Jeziorski. Yeah. It started out as an opportunity for us to talk more often and talk about paleolimnology. We both just sat down and said, "Hey." I had this blog on my website that I'd only ever made one post. And he's like, "Why don't you ever post anything in the blog?" And I'm like, "Oh, I don't know what to say. It's weird to write about some of these things," and decided that saying it actually was a lot easier. And we have had a series of different types of episodes. We either talk about methods, we talk about applications, or we talk about more big picture things and about how paleolimnology fits into science more broadly, the funding scheme, scientific societies, those kind of things. It's really geared for the graduate student audience, but maybe a few other people find it interesting and we have a good time making it.
Cameron: Yeah. That comes across. I've listened to a couple of episodes. And it sounds like you guys are having fun.
Josh: Yeah. It's just a good way. I haven't seen Adam in more than two years now and yet we get to talk all the time as we plan these things. We've had a few guests, we'd like to have a few more. Sometimes those are logistically challenging as you know for sure, but it is a good time and it keeps me thinking about the broader science and out of just my permafrost Northern kind of focus putting it into the context of all of paleolimnology and where it fits into science.
Cameron: Great. Well, Josh, thank you so much for talking to me about your research. It's important obviously that you also make it very interesting.
Josh: Thanks for having me. Talk to you soon.
A thaw slump in the Mackenzie Delta (photo: York University)
Links
Josh Thienpont’s faculty page at York University
Josh on Twitter
Core Ideas podcast
Credits
Host and producer: Cameron Graham
Production assistant: Andrew Castillo
Photos: York University
Music: Musicbed
Tools: Squadcast, Audacity
Recorded: May 20, 2022
Location: Toronto
