Webinar: Arctic Extremes - The Frontlines of Global Warming

Hi everybody and welcome to today's webinar. It is 2:30 on the dot according to my clock, and we still have a number of people streaming in, so we'll get a slow start. But I'd like to welcome you to our first webinar of this month of May in 2020. This is part of our new Spring 2020 KNAB webinar series. And thank you so much to the Knab family for their support of this effort to reach out to you in a new way. We are going to be hearing today about Arctic the front lines of global warming. And I'm really excited for everything that we're going to be able to bring you today. These webinars, as I said, were recently launched at the middle of May or March, excuse me, toward the middle or end of March as Woods Hole Research center was transitioning into what has become our new normal of working from home, working remotely in most cases from around southeastern Massachusetts, but as you'll see today in some cases, working from around the globe to adapt to COVID 19. And these webinars were a way for us to stay connected with those of you whom we might usually see at our in person events and also reach out to new people who found themselves stuck at home and looking for meaningful content, ways to connect to the outside world and to to learn more about important issues like climate change, which of course remains the greatest challenge of the century with COVID still right there in the running and very much top of mind right now. But when Covid ends, we will still have a climate crisis and Woods Hole Research center scientists will still be and are still studying that. And so we're excited today to talk to you about some of our Arctic research. Before we do that, as we've been doing each week in these webinars, we'd like to get to know a little bit about you. And we recognize that that's really difficult in these webinar settings. It can feel a little disembodying and a little odd to be on the receiving end. So to give you an idea, you are currently in the company of 155 other participants in this webinar, whether or not you can see them all. And that number is still increasing. We've still got people joining us, so welcome. If you are just joining us, we'd like to get to know a little bit about each of you. And we've been starting with one very easy question each week, which is how old are you? And what I'm going to do here is launch a poll that should be popping up on your screen and give you an opportunity to tell us how old you are. We're always curious, especially given that these events are happening during what would have been in normal times during the school day or during the work day. But of course, most of us now find ourselves at homes during this window. So today we have about 85% of you have voted at this point and 57% are 65 or older. 16% of our participants are in the 51 to 65 year old age range, another 16% in the 30 to 50 age range and about 12% in, in the 19 to 29 year age range. So we've got a nice diverse group in terms of age with us here today and I can share those results with you so you can take a look at them. Of course, age is not the only way to get to know somebody and we've done a few other polls. But today, especially since we are going to be talking about the Arctic and it's a place that for many of us can feel very remote. That is very remote, but can feel very separated from our lives and very unfamiliar, I thought I would ask if anyone in our audience has actually been to the Arctic. And you can just go ahead and raise your hand if you have been to the Arctic. Okay, we're up to 17, 22, 24, 29. Numbers are just, I'm not going to keep ticking them off. The numbers are still climbing. This is terrific. So we've got at least three dozen of our attendees here, close to 40 people saying that they have been to the Arctic and a couple of people letting me know in the chat that they have been either alternately or additionally also to the Antarctic. So a well traveled group here and more familiar maybe than your average crowd with the Arctic. And so I'd like to, I'm going to pop up the screen share here again and ask you each. I'm going to also have you all, I'm going to lower all your hands because I'm going to ask you to raise your hands again here in a second. And what I'm going to do is show you a picture here and ask you to raise your hand if you remember going back about five years to the summer of 2015, seeing images like this of craters that were detected in Arctic regions in the Siberian Arctic. So a number of you raising your hand here and raised hands are now filling my screen. Hopefully they're not filling all of your screens as well. But a lot of you clearly do remember that these craters, newly discovered Craters in the Arctic permafrost made international headlines. And I bring this up because this is really just one of perhaps the better known extreme effects of climate change at the time. Completely unexpected, as you may hear from Sue Natali, one of our panelists today. Very unexpected even to leading scientists in the field. And that's the kind of change that we're going to be hearing more about today. These really sudden, dramatic and often unexpected changes that we're seeing happening in the Arctic as a result of extremely rapid warming there. And we're going to talk about that not only in terms of the facts and the fact that these things are happening, but also why it's so important to understand why and how these extreme events are happening and also the challenges, from the logistical challeng to the intellectual challenges of trying to understand such abrupt change as a result of climate. So without further ado, I'm going to introduce our first presenter. Rachel Treharn is one of our newest staff members at Woods Hole Research Center. She is a postdoctoral researcher in our Arctic program and as a result of COVID she is working not only from home near the center, but she started after we had all gone into remote working mode. And so she is joining us today and joins us for work each day from Oxford where she is quarantining or isolating there. And we are looking forward to the day when we will be able to welcome Rachel to the Woods Hole Research center campus. But for now, welcome to our webinar, Rachel, and take it away.

Great.

Thanks for the introduction, Heather, and thanks so much for everyone who's logging in. I can see there's still some people coming in. It's fantastic to see so many people getting involved. And yeah, it's particularly nice for me, given, as Heather said, I haven't quite made it across the Atlantic yet. So it's fantastic to be able to get involved despite that. So I will start sharing my screen and we can get going. So hopefully you can now see this. Fantastic. Yes. Okay. Right. And so as we've already discussed, we are going to be focusing on the Arctic for this session and I'm really excited that we're doing this because as Heather mentioned, the Arctic can feel particularly remote. It can feel very sort of out of sight and out of mind, but it really doesn't deserve for that to be the case. So, first and foremost, of course, the Arctic is home to more than 4 million people worldwide. But also for those of us sort of down here in more temperate latitudes, the Arctic plays an important role in Regulating our weather, it helps to regulate our climate globally. And we'll be talking a little bit more about that later on. But also this is just a really fascinating and I think a really exceptional, exceptionally beautiful part of the world. And I hope that we could give you a little sort of flavor of that today, particularly for those of us who haven't been to the Arctic. Before we go any further, I want to take a moment to think about what actually is the Arctic. So quite often I talk to people who are really surprised that I work mainly on Arctic vegetation, because so often when we say the Arctic, people think of sea ice, we think of polar bears. But the Arctic is, of course, much, much more than that. And actually there's a whole range of definitions that we can use for the Arctic, and not all of them sort of just limit us to this area within the Arctic Circle that you can see on the map here. So, for example, we might, by saying the Arctic, we might be referring just to the sort of the darkest area you can see on this map here. And this is the, the extent of tundra vegetation. So these are landscapes that look a little bit like this picture here. But we can also sort of broaden that definition out a little bit, which we do very commonly, and that's what we're going to be doing today. And also sort of expand what we mean by the Arctic into this paler area you can see on the map here. And this is showing the extent of the boreal forest. So landscapes look a little bit more like this. But regardless of which definition we're using here or whether we're using a completely different definition, of course, when we say the Arctic, we're talking about the northernmost part of the Earth. And because of that, among the sort of defining characteristics of what we mean by the Arctic are of course, extreme conditions, or what we might think of as extreme conditions. So this might be just extremes of temperature, they might be extremes of remoteness and in excess of. Or of course, they could be extremes of light. This is a part of the world where the sun never sets during the summer and never rises during the winter. But another, another really important part of what is extreme about the Arctic is of course, its response to human induced climate change. So this figure here is showing you the warming that we've seen so far compared to temperatures during the second half of the 20th century. So the redder the color here, the more warming we're seeing. And you can see that this red color is really quite clearly highlighting the Arctic. So the warming we're seeing Here is really among the most acute that we're seeing anywhere in the world. And you can see much of the Arctic has actually already warmed by more than 3 degrees. And this trend is showing no sign of slowing down. So the Arctic as a whole at the moment is warming more than twice as fast as the globe on average. And so this means that unless we really step up our climate action efforts, then we're looking at warming in the region of sort of six degrees across the Arctic by around the middle of this century. But pinning down what this warming, this really rapid warming actually means for the Arctic is still quite a challenge for a lot of Arctic scientists and a number of us working at Woods Hole. And one of the reasons for that is that the Arctic isn't warming in a uniform way. And what I mean by that is that in many cases, Arctic environments aren't just warming up, they're also becoming more variable. And in turn, that means that Arctic ecosystems aren't just responding to climate change in a gradual, linear, sort of predictable way. They're also changing very suddenly and very dramatically, and sometimes in ways that we don't expect. And the only analogy I could really come up with for this is a coin slot machine. I don't know how many people out there might have encountered one of these, but if you haven't used one. So the sort of the top layer, which you can see at the back of this image, sort of continually is moving backwards and forwards and shunting these coins forwards towards the front. And the idea is that you drop in your own coin from the top, and initially, of course, nothing happens, but these coins build up and they build up, and eventually enough of them have built up that suddenly a whole lot of them will tip over the front all at once. And the idea then is, of course, that you win lots of coins, but in the Arctic, the equivalent of this sort of build up of coins suddenly tipping over the edge is one of these dramatic, substantial shifts in how an ecosystem is functioning. So, in other words, an extreme event. But what do we really mean when we say extreme event? What do these things look like on the ground? And, of course, there's a whole range of different ways that we can answer that question. But one of the extreme events that many of us might have heard the most about is, of course, wildfire. So fire isn't just something we see in more southerly, more warmer latitudes. Fire is a really important part, an increasingly important part of both tundra ecosystems and boreal forest ecosystems. And this is something that Tatiana is going to be telling us a little bit more about later on. Something else that, again, we might have heard quite a lot about is permafrost thaw. Permafrost thaw is actually one of these processes that does happen a bit more gradually and a bit more linearly, but it doesn't. It doesn't just happen that way. We also see permafrost Thor happening very dramatically and very abruptly. And that's what this image here, this is a Thor crater in eastern Russia. That's what this is showing, and I think it kind of demonstrates what I'm saying there quite sort of intuitively. And again, sue will be picking up on this later on and talking to us a little bit more about this. But as well as these things, there are also a number of extreme events happening more often in the Arctic that are less well known. And this image here is showing you a quite fine scale, abrupt southern plant dieback, which we also refer to as browning. And this is something that is a result of a number of types of extreme events, but particularly climatic events that happen during the winter. And we're seeing this browning happening really at landscape scales now. But until just a few years ago, we didn't even know this was happening at all. And one of the reasons that this was so unexpected is that it is a little bit counterintuitive. We might imagine that as the Arctic warms up, and perhaps it's the summer's become a little bit more favorable for plant growth, that we'd be seeing more vibrant plant communities, sort of greener, more productive, bigger vegetation communities. And in fact, that is actually the case across much of the Arctic. And we are seeing a lot of this greening. But greening is a response to that gradual change. And as we've seen already, the Arctic is not just changing in a gradual way. So the reality of what we're seeing is that we are seeing the Arctic greening up, becoming more productive, but we're also at the same time, seeing more extreme events that are interrupting that trend and driving this sudden browning, this sudden plant dieback. Just to give you a bit of a flavour for the types of extreme events that result in this browning, I'm just going to take you through an extreme winter warming event. Extreme winter warming begins with often a really very abrupt increase in temperature. Of course, during the winter, if those warm temperatures then persist, we see the snow cover melting away, and that exposes any evergreen vegetation. The exposure of that evergreen vegetation to these really unusually warm conditions essentially means that these plants think it's spring we'll see them losing their cold tolerance. We might even see these plants bursting bud in the middle of the Arctic winter. And, of course, the result of that is that when temperatures drop back down to a more sort of sensible, normal Arctic winter level, we see these plants are unable to cope, and we see vegetation damage and death. My research looking at these events over the last few years has focused mostly on what are the consequences of this browning, so of this dieback of evergreen species, what are the consequences for the ability of Arctic ecosystems to soak up carbon and lock it away from the atmosphere? And I'm just going to talk you through one key outcome of this work. So this figure is showing you the net carbon uptake across a single growing season. And it's showing you that in healthy green vegetation that hasn't been affected by an extreme event on the left, and in some vegetation which has been affected by browning on the right. In this figure, a deeper bar means more carbon being absorbed by that landscape. You can see here that the vegetation damage that we see with browning does have a really substantial effect on the ability of this landscape to do that, to soak up carbon. But what we also saw here is that this isn't actually the whole story. So up until now, we thought that the only response, the only type of browning that we saw from these extreme events was what we've talked about so far. So this plant dieback, this plant death. But spending lots of time in the field and really looking into these events in more detail, what we've also found is that we see something else. We also see this. You can see from this photo that this vegetation is still alive. It hasn't been killed. But what's happened here is that a natural and normal process, which is the process for this plant to synthesize red protective pigments, has gone into complete overdrive. And that's why you can see this really deep red, almost black coloration. And this is signaling plant stress, because most often we're out in the field later on in the growing season, collecting data. We hadn't actually ever seen this response before because often later in the growing season, this response becomes much more difficult to spot. This plant sort of becomes much more green. And so that meant that we also had absolutely no idea whether this was having any impact on the ability of these ecosystems absorb carbon alongside this dieback response that we were more familiar with. And so this figure here is showing you the answer to that question. So this is the same figure that we talked through a moment ago, but now with that stress response added in. And you can see really quite remarkably, that whether this reduction in carbon uptake is associated with dieback, so with the death of evergreen species in this community, or with this stress response, those reductions are very remarkably similar. And perhaps even more importantly, you can see in both cases, this is a really major impact on the carbon that's being taken up by the Zika system. In both cases, that carbon uptake is almost halved. So in response to this extreme event, and this brings us on really, to one of the key reasons that we shouldn't let the Arctic stay kind of out of sight and out of mind, and that is that the Arctic is an enormous carbon store. And that's really not an exaggeration. Arctic soils alone contain more carbon than our entire atmosphere and all plant life across the surface this planet put together. And the reason for that is, again, the extreme conditions that we find there. So the carbon that Arctic plants take up and lock away, instead of decomposing and being released back to the atmosphere, instead builds up into these really rich, deep soils. And this kind of temperature effect on decomposition is something that we see everywhere. So even in your compost heap, of course, the warmer it is, the more decomposition we see. But of course, what this means is that as the Arctic continues along this really rapid warming trajectory that we've pushed it onto, more and more of this plant matter will begin to decompose, and we'll see more carbon being lost from the Arctic soil carbon store and moving into the atmosphere. And of course, the natural question here is, how much of that carbon are we going to lose from the Arctic? And this, of course, is a critical question for those of us working in this region. But it's also one that does still have, has, unfortunately, a lot of uncertainty associated with it. Don't have the answer to that question. Of course, all the events that we've talked through so far do threatening Arctic carbon storage to some extent. But as you can kind of imagine from the scale and the abruptness and the unpredictability of these events, it's really hard to build them into our kind of predictions of the future of this process. And so because of that, this is still a really big question for all of us working on this area. And it's maybe something that we can talk out, talk about a little bit more later on, but for now, that is it from me. So I will stop sharing my screen. I'll hand us back to Heather. Thank you.

Terrific. Thank you so much, Rachel, for that great introduction and overview of what we're Talking about when we say things like extreme Arctic change and extreme events, we're going to turn for another perspective, as we said, to another Woods Hole Research center staff member, also a postdoctoral researcher in the Arctic group, Tatiana Shestikova, whose focus is on fire, as Rachel mentioned. And Tatiana, I wonder if you could share with us some of your perspective on how fires are perhaps becoming more extreme and what their impacts actually are, what you're learning from your research.

Yeah, absolutely. Can you hear me? Fine.

We can hear you perfect.

So let me share my screen. Okay. I would just like to show like, you know, a few pictures or images that we capture in the field, so just to better illustrate what I'm going to talk about. And. Well, fires are actually a natural part of boreal ecosystems, both boreal and Arctic ecosystems. So boreal forests that I'm working in actually have been evolved together with fires over thousands of years. And fires actually serve as a rejuvenated. They rejuvenate the forest ecosystems, they help to foster biodiversity, they help the nutrient cycling of the soils in those forests. So on the left picture, you can see an example of mixed large pine forests in Siberia that eventually can survive through several cycles of low surface, low severity fires during their life cycle. And what we actually see now is our accelerated fire cycling. And what I mean by that is that fires are getting more severe and they are getting more frequent because of climate change. And those fires are affecting more higher areas and they often lead to tree mortality. That is unexpected for duss ecosystems. And an example of that you can see on the right picture. So what are the reasons? Can I change my slides? Okay, here. So what are the main reasons for these changes? And of course, the biggest one is the climate warming. So as we get higher temperatures, we are seeing hotter and drier summers, and this dries out the fuel in the forest. And then we get also longer fire seasons. And altogether this results in increased fire severity and the extent of the fire events together. With that, we already see that there are important interactions between fires and other disturbances, such as recurrent droughts, insect outbreaks, and human activities such as logging, mining, etc. But there are also more surprising reasons too. So, for example, warmer climates can lead to more lightning strikes, which are actually one of the major cause of the Arctic fires. And most of the times. So since boreal forests and Arctic are sort of remote, so they don't have an easy access through roads, and most of the times, wildfires are left to burn uncontrolled, unless they threaten an important infrastructure or settlements so as a result of that, they grow large and consume thousands of hectares of vegetation and also carbon rich top moors soil layer. And it might be not very obvious, but not all boreal forests are burned the same way. So for example, as you can see from this map, North American species known as fire embracers, because they have evolved to promote and spread fire, high intensity ground fires. And in general these trees are killed by fires, but they also benefit from the fire event because they use this heat from the fire, from the flames to trigger seed fall. And thus they use it as a regeneration trigger. So in Eurasia, under, on the other hand, you can see that trees, well we can refer to them as fire resistors. So they have developed thick barks for example, to protect living tissues from heat from low severity surface fires. So they also drop lower branches in order to as tree grows in order to prevent fire climbing up and damage the needles of those forests. And the point I want to make here, that without the right kind of fire regimes, these trees simply cannot regenerate or even survive, even those that are usually adapted to fire. So on the left picture you can see an example of a Canadian forest that failed to regrow after a wildfire in 2014, because the fire was so intense that it burned all the seed bank and also removed the nutrients from the soil. On the other hand, the frequent, too frequent fires also can be a problem because imagine if a tree is too young and it burns so it's not mature enough in order to produce cones and seeds. So the regeneration potential of that forest also can be limited and another reason why it's important. So the frequent burnings may affect the, may affect soils and in general degrades or cause cumulative degeneration of the soils. So eventually this might alter the whole successional pathways of a particular stand. And we already see the results of these on the ground. So for example, in low elevation dry environments, we can see that mostly coniferous forests turning into deciduous broadleaf forests or even forest vegetation is completely altered and substituted by steep vegetation. So unfortunately, these big fire events are happening more and more frequently now. And I'm sure that all of you have seen all these dramatic pictures of fires that went out of control. And well, just to give you one example, just last year in 2019, the Arctic wildfires were again record breaking in terms of severity, location, timing and the scale that they happen. And this resulted, as you can see on this graph, in releasing of about 320 megatons of carbon into the atmosphere. And just to put this number into the context. So it's about the third total emission of the cars that, well, that are actually running in the US during the year. So those fires were accelerated by the especially hot and dry summer, unusually hot and dry summer, and they burn across the whole Arctic in Siberia, Alaska, Canada and even in Greenland. So on the top right picture, you can see an example of one of the fires in central Siberia where they initially started. And this location, as you can imagine, is relatively remote and far from populated areas. So the fires were left unattended, and in just few weeks, those fires grow as much, so they cover in smoke hundreds of kilometers. And on the lower picture, you can see an example of the capital of that region that were completely covered in smoke for several weeks. And so people couldn't breathe, they didn't see sun. So a lot of emissions, not only from fire, but of course a lot of carbon emissions happened, but also it affected health of the people living there, and not living only there, because this smoke have spread through Urals on the west and even to Alaska on the east. So, and finally, I wanted to say that we happened to work on the field in Siberia last summer, and the picture with this red sun was taken about 1000 km up from the fires, but we still got just this smoky haze for the two weeks in a row, although we were pretty far from the original source of the fire. And it's just another reminder for us that although Arctic ecosystems, they can look very remote and be in very lightly populated areas, but they do affect the whole world. And we are still lacking a lot of pieces to put the puzzle together and need to do more research to understand what are the impacts of these drastic changes for the ecosystems, climate, and, of course, human health. So that's sort of all I wanted to say.

Thank you so much, Tatiana. You know, we started off saying that the Arctic often seems very, as we said, remote or perhaps removed from our daily lives for most of us, and is not necessarily the place that many of us envision of entirely ice and snow. But as we've heard from Rachel and now Tatiana, of plants, of boreal forests, and unfortunately, of dieback and forest fires increasingly. And our final panelist, who I'm pleased to welcome, is Sue Natali. She's an associate scientist in the Arctic Program at Woods Hole Research Center. And much like Tatiana, who experienced the impacts of those forest fires while in the field last year, sue, you also did. And so I'd love to hear from you some of your experience with what it was like to try to do field work under Those conditions. And also about the work that you were there to do studying. We've heard about from Rachel about vegetation. We've heard from Tatiana about fires. And you were there to study permafrost. So a little bit of what we're seeing in terms of extreme events involving permafrost as well.

Great.

Sure. Thanks, Heather. And thanks for everyone for joining. I'm going to share my screen and just show a few pictures as I talk.

Okay.

Can everyone see that? So, yeah. So fires, we think of fires in terms of forests, but fires also can burn tundra. So this is an example of that. And this is actually wetland tundra. So it's kind of surprising that it burned. This is a picture of a wetland tundra system that burned in 2015 in the Yukon Kuskokwim Delta region. That's in western Alaska. And 2015 was a really extreme year in terms of the climate leading to these very widespread burns. So in this area in 2015, more area burned in 2015 than the previous 70 years. So it was a very low snow year and very warm and dry conditions that led to this fire. One of the things that's interesting and problematic about fire in the Arctic is that it doesn't just burn the trees and the plants above ground, but it also burns the roots and it burns the soil, because the soil, as Rachel had mentioned, it contains a lot of carbon. So the carbon is in the form of organic matter. And that organic matter can be combusted. And so that's the problem when we think about climate, because when it gets combusted, it gets released into the atmosphere as we greenhouse gases, carbon dioxide and methane. It's also a problem because that organic material in the soil and the surface vegetation act as a very good insulator for the permafrost. So the permafrost is the perennially frozen ground that's beneath the soil in northern regions and also in mountainous mountain areas. So the Arctic, we think of it as a cold place, but have you heard it's not always cold and actually can get quite warm in the summertime, as I'll show you a couple slides. So this organic layer acts as an insulator for the permafrost against these warm summer temperatures. You can kind of think of it when you remove that organic layer in a fire. It's sort of like opening the top of a cooler on a very hot summer day. So this is what that same fire looks like on the ground four years later. So this is a picture from last summer. The first thing you can See, there's a lot of green, so the vegetation is starting to recover. But the other thing you see is this big crack in the ground. And this is an abrupt thaw event or a thermokarst. And this happens because the permafrost contains a lot of carbon, it contains organic material, but it also contains ice. And that frozen ground, including the ice, provides structure kind of like cement. But when the permafrost thaw and the ice melts and the ground loses its, its structure and you can get these ground cracks. We had saw quite a lot of these last summer. You can see this is just air temperature. Over two weeks when we were in the field, it was up to 32 Celsius, which is about 90 degrees Fahrenheit. And that is really, really hot. Last summer was, as Tatiana mentioned, widespread fires across the Arctic. So we were not, not surrounded by active fires. Where we were, we couldn't see them. But it was very, very smoky. It was very, very hot. And a lot of the area that had burned because of these extreme temperatures we were seeing last summer and also very warm winters, the ground was cracking. And literally when you walked in some areas, your foot would fall into the ground up to your knee because there was really just no more ground structure for, for support. One of the things, one of the reasons why this is important, one of the focus of the research that I do focuses on the consequences of permafrost thaw, both what we refer to as gradual thaw and then these abrupt thaw events. In this picture in the upper right hand corner, this is a student who worked with us last summer, and she's collecting samples to measure carbon dioxide, methane and nitrous oxide in these abrupt thaw areas. And she had some really interesting results, one of which was substantially higher nitrous oxide emissions from these abrupt thaw areas. And you know, the reason that was really interesting is because we had measured nitrous oxide or collected samples for nitrous oxide in soils and undisturbed areas. And we have never measured elevated nitrous oxide in the soils until we started seeing this cracking happening. Nitrous oxide, as many of you know, is a really potent greenhouse gas. It's more than 250 times more powerful as a greenhouse gas than carbon dioxide. This is some really interesting work and it's work that we just started exploring. I want to show another picture from another place in the Arctic where I work. This is in Northeast Siberia. And this is another example of an abrasive thaw event. And you can really Get a good idea from this picture when I say there's a lot of ice in permafrost. There is a lot of ice in this permafrost. This area has these massive ice wedges which kind of look like the shiny areas in this picture. Maybe it looks like water, but it's actually ice. And so you can see when the ice melts out. This is a forest. You can see it at the top of this exposure here.

And.

And the trees are just tumbling down as the ground collapses. And just to give you a sense of scale, these are 10 to 20 meter tall trees. The other thing you can notice in this picture is a lot of exposed soil. And that soil had been frozen as permafrost. It's now thawed. And as it thaws, the organic material is available to microbes which can release carbon dioxide and methane and nitrous oxide from these extreme events. The other thing I want to point out is, you know, permafrost. Permafrost, once it thaws, it can refreeze.

Right?

So if we reduce global temperatures, some of the permafrost can refreeze. That's possible and it does happen. But when you think about these abrupt events, this is something that really is irreversible, at least on a human relevant timescale. And that's really important to keep in mind when we think, you know, what does it mean for something to be an extreme event? I mean, permafrost thought itself may be an extreme event, but some of these things are really irreversible. And I just want to show one more slide. Has come up with the previous two presenters. There are people who live in the Arctic and may seem remote to us. Changes that happen in the Arctic are important to everyone on this call because of global linkages, particularly through greenhouse gas emissions. But, you know, these abrupt events are. Have been for many years now and continue to affect the people of the Arctic directly. This is a village also in the Yukon Kuskokwim Delta region of Alaska. Permafrost thaw is one extreme event that's happening. Loss of sea ice is causing extreme storm damage and flooding. And you can see just how vulnerable some of these communities are that are built on top of permafrost. These sort of both the gradual and the extreme events are impacting homes, impacting cultural resources, and also impacting infrastructure. And with that, I will hand us back. Stop sharing my screen and hand us back over to Heather.

Thanks, Sue. I think the picture we're getting from all of you, whether it's Tatiana talking about fire in boreal forests, or Rachel talking about this dieback that she and Browning, that she's been documenting, or sue, you talking about these abrupt permafrost thaw events. We can use these words like abrupt or extreme, but I wonder what that feels like as a researcher when you first encounter that. I mean, are they surprising, are they shocking? Or is this something that, you know, the first time you encountered it, you thought, oh, well, that is the natural progression of what we were seeing, and it's an extreme version, but it's not terribly surprising. You know, how actually, like, shocking or surprising is this when you first realize what you're looking at in your data. Do you want to start and then we'll.

Yeah, sure. Yeah. I guess I'm going to actually talk about observations from the field even before looking at the data. And I think when you go back to a field site year after year after year after year, and you see, you know, interannual variability in climate and temperature and plant growth, you get used to that. But I think what I saw last year in that area that. Where I show the ground cracking, it's actually quite shocking when you get used to a place and all of a sudden the landscape has actually changed. So imagine, you know, imagine going in your yard, and your yard is, you know, one day it's, you know, whatever 100 meters long, and the next day it's only 80 meters long because 20 meters have fallen away. And, you know, this is the case. We set out a transect and we go back the next year, and we can't set out that same transect because part of the ground has collapsed. So it's really, you know, there's the numbers behind it that are really important. What does that ground collapse number? And where is that carbon going? Is it going into the air, is going into the water? But there's also kind of. I don't want to say. I don't know if it's an emotional connection, but it's just your connection to place. And that's just for me, as a scientist who goes there and comes back. And I think this is even just so much more for the people who are living in the Arctic and seeing this and watching these changes happen in their lifetime from one year to the next.

Rachel, do you want to chime in there?

Yeah, yeah. I think. I'd say similarly, I think it is. It is quite shocking with a lot of the events that I've worked on. So the dieback events I was talking about, you arrive in an area and one event in particular, you know, driving, driving through this landscape looking for a field site and you just look at all the vegetation around you, almost all of it is dead. And it's very, it's very dramatic. I mean, in the sense of those events the extremists have comes from that extreme ecological response. So it's very, it's very dramatic, it's very visible, it's very tangible. And it is again, you know, staying with the sort of field experience rather than the data is. It's quite shocking. And it is also quite sad as well because you see these things more and more and obviously, you know, we work in these landscapes partly because, you know, it's an amazing part of the world and, you know, we sort of really care about these landscapes and you see these very dramatic, very extreme feeling things happening and yeah, it's a strange experience.

Tatiana, how about for you, can you speak to your experience a little bit looking at fire and how that's changing?

Yeah, well, I agree with everyone that sue and Rachel just said, but I would like to add to that that also frequency of those extreme events are really important because, you know, once you get a large fire, so you are not really probably should worry about because vegetation will recover and eventually everything will become as usual as it was before. But once we start getting these extreme fires or other changes that actually large in scale affect huge amounts of area and then you can realize that the ecosystem is just not used to that, so they cannot simply recover from those events. And then you have to think what is actually coming after that, so how it's going to be altered by these changes in the future.

Tatiana, we've had a couple of questions from the audience and I should say to everyone, if you have questions, please join in here. We have just a little bit less than 15 minutes for some Q and A with all of our panelists. So there is a little Q and A icon at the bottom of your screen. You can type your question in there and we'll see how many we can get to. But Tatiana, a couple of people have asked just for some more kind of basic information about what are boreal forests and you know, what is. And you hit on this in your presentation that there are actually different types and some are more fire adapted than others. But give us a sense, just kind of what are these forests and what would normal look like in terms of a, you know, a fire regime?

Yes, that's a great question because, yeah, probably it's not very obvious for many people. So I would Broadly define boreal forest is forest more or less like 60 degrees north that are dominated by conifer species. And, well, in North America is basically Alaska and Canada, and in Eurasia it's Siberia and part of the Fennoscandian countries. So, and in terms of frequency and intensity, if you recall the map that I showed during my presentation. So, for example, North American species, they are really adapted to high severity fires, but they should be relatively low frequency because the trees has to have time to mature and then produce the seeds. So when the fire happens, trees are killed and it's not a problem because they still can regenerate from the seeds that they produce during their lifetime. In Siberia or Eurasia as a whole. Well, particularly in Siberia, the fire events that the DUS ecosystems are adapted to low severity fires. So they really killed very easily if the crown is damaged. And they actually developed some protective measures. As I mentioned, sick barks really like they, they throw lower branches during the lifetime. So they really try to prevent the fires or suppress fires when they happen. And I also didn't mention that there are a certain kind of structure species that are fire avoiders that are completely killed by the fire and they cannot stand any fire at all. So if this ecosystem eventually start to get fires and they are less represented in arboreal forest, but in general, so those ecosystems are just going to disappear.

We have a couple of questions here that I'm going to combine a bit, which is curiosity about wildlife impacts, which obviously if you're impacting forests and the soils and the ground and the vegetation, you have to be impacting wildlife as well. And also whether invasive species might be something that we're seeing more of as we're seeing Arctic ecosystems disrupted in these really extreme ways. Sue or Rachel, is that something you want to try to tackle a little bit?

I can say a little bit about wildlife. It is certainly not my expertise, but the 1, 1 change that's been happening in the Arctic is that they've been getting rain events in the winter, which is really uncommon and it causes a lot of problems. But people call these rain on snow events. So, you know, you get rain in January and then of course it's going to freeze up again. And this is a problem for causing a problem for wildlife, who, caribou who may be searching around the snow, you know, trying to get food sources in the winter and losing access to some of those food sources because you have this really impenetrable layer on top of the snow. I mean, there are many other reasons why rain on snow events are problems for humans. But that's the one really obvious wildlife impact that you see of these kind of extreme winter events. And perhaps Rachel has more insight on this.

Yeah, only really on that type of event. So those ground dicing events were one of the types of events that I looked at that caused browning. So actually I think that first picture that I put up of the sort of close up of the sort of gray dead plants, that was from a ground dicing event, Svalbard, where that rain on snow event resulted in a layer of ice, which I think was something like 30cm thick solid ice across this huge area that persisted for several months. And that did result in a real crash in the reindeer population who just couldn't get through to the food, to the ground to feed. And there were some really quite distressing sort of stories I heard about people observing reindeer sort of trying to, trying to cut, climb up steep slopes, try and access food because there was so little access to food and falling down and also being killed that way. You know, quite quite upsetting stuff. But yeah, again, I'm not a wildlife specialist, so that's the extent of my insight on that one.

Thank you both for jumping in there. Sue, I want to circle back to that picture that I showed at the beginning of a crater in the permafrost. That's not one of the permafrost effects that you explicitly mentioned in your comments, but it is something that you're now taking a look at, trying to figure out more about the prevalence of these craters. And it highlights for me the fact that that was five years ago and you're studying these now, that there may be difficulties in trying to study unexpected and really rapidly changing systems. Just because our infrastructure for, for studying it, for going out once a year in the summer, for getting funding to do that, may not really be set up to actually study these kinds of events. Is that a challenge that you've encountered in your work?

Yeah, it's definitely a challenge. And I guess I should just quickly say that crater is. People call them gas emission craters or methane emission craters. They resemble what looks like a pingo. So as a pingo is an ice cream filled mound in the Arctic that can take decades to hundreds of years to form, and these can form in a couple years. There's gas that's produced below ground and then it's sort of creating literally an explosion which then forms this crater. And you know, I guess it's been about five years ago when the first ones were found. There's still only six known craters and so why do we not know about more of these? Are there not more out there? And so we're working on a mapping project right now to try to use remote sensing and satellites to find more of these craters. And we've actually found quite a few more. And one of the challenges is, you know, something, an event like this happens that's unexpected, but it takes a couple years to get funding. And then once you have funding, you get the project going. And so when events are happening, particularly these sort of new events and how the Earth is functioning when these are occurring, and these are events that perhaps you're not anticipating, you're not anticipating to happen, where they're happening, or at the pace that they're happening, it's hard to be prepared for that. And then, even then, once you're on the ground studying these, getting those processes, say, into models that inform how we understand how the arches is going to affect the climate system, it takes a while. It takes many years. And it's just the way our funding system and way science is done is definitely slower than the way that we need to find out this information, Information and the information that we need to start making smart decisions.

So we've got about five minutes left for our webinar, and I'd like to just kind of piggyback on what you were just saying, sue, and ask each of you to wrap up by sharing how studying these sorts of extreme and abrupt events might have changed your broader understanding of climate change or your attitude toward this issue. When you start to see, as you were saying, sue, things happen that are unexpected. And to our knowledge of how human, our knowledge of how Earth systems work, completely new. What does that do to your whole mindset around this issue?

I think a couple things. We often talk about average global temperature increase, and that's really not what affects ecosystems. It's these extremes and. And it's these localized temperatures. From what I've been seeing, the surprise processes, the unexplained processes, the processes that are not in models, all tend to push the system in one direction, which is that the climate is having a bigger impact than we expected. And the system is responding in a way to accelerate that climate change. And there are some feedbacks that offset the climate change. But we tend to see in these extreme events in the. And the fire and in the craters and the abrupt thaw that keeps pushing and pushing and pushing the system in one direction. And so to me, what I think about when I see this is that we really, really need to ramp up our response and do that immediately.

Thanks, Sue. Tatiana, how has studying fire and how that is changing in these boreal forests changed your outlook more broadly on the issue of climate change?

I would like to mention here interactions, complex interactions in the ecosystems, because you can think about fire effect, but then when you study more and more and learn more about the processes, you can see that it's not only climate change that actually impacts the change in fire regimes, but it also the, for example, insects, as I mentioned, or other disturbances that change together with other components of the system. And altogether this is highly difficult to predict and just to foresee our future because what we have now is based on the past. So basically what we could learn from 100 years ago. But we've never been in this situation as now, so we urgently need more data, more research and deeper understanding of the problem.

Thanks, Rachel. We started with you, so we'll end with you. How has studying dieback and extreme Arctic change changed your outlook on this issue?

Yeah, I think just spending time working in the field in the Arctic change had a really big impact on my perspective on climate change. But I think in quite a simple way, really, I think often we are still framing climate change as this, you know, something that will happen if we don't do X or if we don't do Y. And, you know, being in the Arctic and you see these, these really transformative changes that are happening in these ecosystems and that people are already experiencing the effects of. And it just really, it really brings home that that's not true. This isn't a future problem, this is a now problem. And really the questions, the questions that we should be asking about this are not sort of, oh, how long do we have left before X? That it's really, you know, how much longer are we going to. How much worse are we going to allow this to get? What can we do to really limit the damage of this as much as we can? And because really, at this point we have to be doing all of those things. And I guess for all of us, that's really. It's not just those sort of individual changes which we all make, which are fantastic, but it's also that the scale of this problem means it is holding to account leaders and business leaders or political leaders, anyone else in positions of authority, because this is a very current crisis.

Thank you, Rachel. Thank you, Sue. Thank you, Tatiana, for sharing your experiences and what you've been learning. Thank you to all of our participants. There were about 200 of you at the peak here. We appreciate all of you sharing part of your day with us and learning more about this issue and would like to just end by reminding you that the kind of work that you have learned about today is often supported by donations. And if what you have heard has inspired you and moved you to want to support this kind of science, science that really is hoping to drive change, working to drive the kinds of actions that Rachel and Sue and Tatiana were just talking about, then we would encourage you to consider a donation to Woods Hole Research Center. We also encourage you, of course, to join us again for future webinars. Our next one will be in two weeks and we will be focusing on the upcoming hurricane season and how that is connected to extreme warming. So please do join us for future webinars. Thank you all for being here and have a wonderful day.

Falling away and you know, this is the case. We set out a transect and we go back the next year, and we can't set out that same transect because part of the global ground is collapsed. So there's the numbers behind it that are really important. What does that ground collapse mean? And where is that carbon going? Is it going into the air? Is it going into the water? But there's also kind of, I don't want to say. I don't know if it's an emotional connection, but it's just your connection to place.