And I'm not gonna make any further ado and welcome Helen to the stage. So please help me welcome her. Hello. Well, thank you for coming to hang out here indoors on this beautiful sunny evening out there. And of course, we have the perfect topic. Who could have seen this coming? Um, so we're at least when you go back out into the sunshine afterwards, whether you're here in the room or uh watching online, you'll get to really appreciate the sunshine because you'll have been thinking about cold places. It's a big topic, and uh so we're gonna take a little dance through lots of different bits of it, but we're gonna start with a bit of history and this guy here, Fridjov Nansen, who is one of the most famous polar explorers from the end of the 19th century, and he was an interesting so-and-so. Basically, what he really liked was skiing and sport at school, and then he became interested in zoology. He chose zoology because he thought it would let him spend more time in the outdoors, and then he took he decided that he liked the outdoors, somebody let him loose on a ship, he discovered he really liked the outdoors, and he made he led the first team to cross Greenland on skis, and this is back in the uh 1880s. But the reason here is because of what happened after that, which is that he around that time there was an idea knocking around that well, the North people were people were sort of the Arctic was a mystery, no one had reached the North Pole, no one knew how to get there, and every time they tried, it kept going wrong. You know, people had set off in these expeditions, they'd set off across the sea ice, and they'd just be driven back, or they'd die, or some other great disaster would happen. So people were very interested in the North Pole, and a little idea came along by a guy who everyone thought was bonkers, it wasn't Nansen. So this is a picture of the top of the world looking down. There is no ice in this image, don't worry, it was there at the time, but this is just showing the land and the ocean. And a few years before, a ship called the USS Jeanette had sunk on the Russian side. So, just to orient you, on the right hand side here we've got the top of Russia, on the left you can see the top of Canada and then Greenland, which does have ice on this rendering. So a ship sunk there in June 1881, and the the uh people on it got off it, so they knew where it sunk, it definitely sunk, there's no doubt about that. And sometime later, some years later, wreckage appeared, definitely from that ship with the name on it down here. And that was very, very strange. It's kind of amazing that anybody linked up these two events, but it put an idea in someone's head, and that idea is that maybe what the reason that this is possible is that there's a current that goes across the Arctic from the Russian side over to the Canadian side. And so that was knocking around, and Nansen was looking for another expedition, and he said, Well, maybe the problem with trying to get to the North Pole all this time is that we've been going again, you know, we're always coming from the the top of Greenland, so we're always going against this current. Why don't we, first of all, start from the other side? That would be sensible, and secondly, why don't we let that current do all the work? That sounds like a good idea. But of course, in order to make that work, you'd have to have some kind of vessel that could survive being frozen into the ice. Because the reason no one had ever tried to sail to the North Pole is that the Arctic was full of sea ice, it's shifting around, and when it starts to converge, when the ice is pushed together by the winds and the currents, it crushes, it crushed any ship that came anywhere near it. So when Nansen said, well, maybe we could go around that side and just kind of you know float across the North Pole and get there that way, everybody said, You're an idiot. All the famous explorers of the day, nonsense, complete rubbish. But Nansen was not going to be deterred by that. He was 32 years old, he didn't care, and he was going to do it anyway. And eventually the public was so taken by this that he did get funding for a ship. And of course, the major thing the ship had to do was not get crushed, right? All of this is sort of theoretically simple, as long as your ship doesn't get crushed. And so, with the help of a ship, a naval architect called Colin Archer, he designed the Fram. And the Fram is an absolutely extraordinary ship. There's never been a ship like it before or since. Here's a photograph of it. The interesting thing about the Fram, here's the plan, is you can see it's a very bulbous ship. It's very, very wide and quite short, and it's very rounded. It's basically like a bowl. And that was exactly the point because the the designer of the ship said, Well, imagine holding an apple pip between your fingers. If you squeeze it, the pip pops upwards. And that is what Fram was designed to do. The idea was that when the ice started to crush this ship, squeeze it together, the rounded keel would just, you know, slide basically, and the ship would pop up and kind of sit on top of the ice and it wouldn't get crushed. Nobody had ever tried this before. And it had all kinds of clever adaptations to work, you know, to make this work. And actually, the inside of it in the bow, it is oak that is 1.2 meters thick. It's an astonishing amount of wood. So they're really committed to this. There's a huge story here that I haven't got time to tell you, but basically it worked. This was their path. So the idea was that they would sail through the open ocean or open-ish ocean along the bottom of Russia. They would go to more or less where the USS Jeanette had been sunk, and then they would just accept that the ship, the Fram, was going to freeze into the ice. And then the idea was that it would conveniently carry them right across the middle of the North Pole, hit the bullseye, and eventually pop out somewhere on the other side. So this they they planned for this to take several years. No one knew whether it would work, no one knew how long it would take. Nansen got a whole bunch of very keen volunteers to come along and they set off. And it did work. There's the Fram frozen into the ice. She wasn't crushed. This is the real path. So you can see they started in more or less the right place. But then this is a slightly simplified place. They kind of went backwards and forwards and round in circles for a bit, which was very frustrating because they wanted to go straight to the pole. They started to float to drift, so they drifted downwards, and then somewhere along the way, Nansen said, Well, this is no good. We're now drifting away from the pole. So he and another guy called Johansson set out on foot, and this is their path, the purple line, to try and get to the North Pole, having gone all of that way. This is a year and a bit in, by the way. They spent a long time doing this. And they eventually gave up because the sea ice was shifting, they got out. Fram eventually did pop out of the ice on the other side. There's an enormous story about this expedition, it's an astonishing thing. And so he got he did get the record for the furthest north, and he survived. Everyone came back alive. And the way that they stayed sane on the ship, well, they're just frozen into the ice. And these are kind of you know, active people, they want to be doing things. For them to be stuck on this ship for a long time is torture. So the thing they kept themselves occupied doing is science. Of course, there's lots of maintenance to do on the ship, there's always things to do, but they they made a lot of measurements. They made some of the first measurements of the depth of the Arctic Ocean, they watched how the ice moved, they measured wind speeds, they did all kinds of things. So there's a huge story here. The reason oh, and you can actually see the Fram today. Not only did Fram survive, she went on other expeditions, she went to the South Pole. Terrible idea, actually, because that rounded keel meant that she was really, really rocky in rough seas. So anybody going across a big ocean in it would sort of roll around and get very seasick, but she was very good in the ice itself. Um, but then she came back to Norway, she's in Oslo in a in a custom-built little uh triangular building, which is very cute. And if you're in Oslo, do go and visit her, it's an astonishing sight. But it was very homely. I mean, this was mostly a sort of solid oak bubble that was going to be a home to uh, you know, a bunch of men for three or four years. So the Fram is an extraordinary story, but this is kind of this is generally our picture of the Arctic, right? There's these amazing stories of exploration, there's ice, which is just the obstacle, it's the awkward thing which is stopping you going to wherever you want to go. It's hard, it's challenging, and no one really understands this is a mystery around ice. And so that's generally our perception of the ice of the world, that it's far away, mysterious, challenging, and definitely miserable if you really want to explore it. But of course, this underplays two very important things. One of them is that a lot of people live in the polar regions. This is a photograph that was taken uh at the foundation of Nunavut, which is a northern territory of Canada that is now self-governed by Inuit, and it's an enormous area. There are four million people who live in the Arctic today. No one officially lives in the Antarctic. So there's a lot of people who are living in these areas. They are human places, even though they seem challenging and difficult to us. But the other thing is that ice, even though it's kind of mysterious and weird and alien, is really important to how planet Earth functions. It is strange stuff. We'll talk about some of that. But it's important. And so what we're going to do is take a dance through some of how ice works and what it does. And I can't tell you everything because it's not enough time, and ice is very, very strange. But I hope to leave you with a flavor of what ice is doing, what it is that Nansen we now know that Nansen would love to have seen, um, and and what the future holds. So here's what's coming up. We're going to talk a little bit about ice physics, uh, where ice is around the world. Then there's this expedition called Mosaic, which was a modern day attempt a few years ago to basically repeat what Nansen did, but do it with all the tools of modern science. And then we'll talk a little bit about how ice is changing and a little bit about the future. So let's start with the physics, which is obviously the good bit. Um there's lots of ice is such weird stuff, it's almost hard to know where to start. But we'll start by looking at it and its colour. This is a photograph that I took from uh on top of the Greenland ice sheet. So I was standing on top of ice, which is on top, a lot of ice, which is on top of land, and it was during the summer, so some of that ice had melted to make a melt pond, and you can see that the water of the melt pond is very definitely blue. And this is because the colour of water is very definitely blue. When we look at the ocean and it looks blue, it's not generally, it's not fundamentally because it's reflecting the sky. It's because if you put enough water together, it has a very faint colour, and if you see lots of it, you can see that colour. And it is this spectacular blue. And you can see it here, obviously, because what's underneath it is ice, and that's white, and so you can see the colour. But ice itself is also blue. So, this is another picture I took on that expedition looking under up underneath a glacier, and you can see that the ice very, very clearly is this very beautiful, very rich blue. And it carries on, you know. If you look at it, you can see a blue tinge when you're looking. This is the front of a glacier, this is down into the hole in the glacier, and you can see there is a blue tinge. So, why is it like what's the deal here? Why do we think of ice as white when it very clearly isn't? Because the reason tells us something very important. So, here there's an example here, this was the side of an iceberg that had carved off that glacier, and it's got this very interesting stripe in it. And what happened in this stripe is that at some point the iceberg had cracked, and then pure water had filled the gap, and everything that had filled the gap and refrozen was blue, but everything on either side was white. And if you go on top of this, which I did, and you drill out a piece from where it's white and where it's blue, this is what you get. So the one on the uh right here is the one obviously that's white. The other one looks transparent because it's not quite blue enough for you to tell. But if you zoom in to the one that looks white, what you see are tiny little bubbles. And the reason it looks like this is that uh glaciers, ice sheets accumulate slowly by snow building up over time. That snow obviously has air inside it, it gets crushed and it gets crushed, and then you get these, when it's crushed down almost as far as it can go, you've still got tiny little pockets of air. And basically that means that most ice is full of boundaries, it's full of cracks or bubbles, something like that. And so light kind of goes in and bounces around and then comes back out before the ice has had enough time to absorb any of the colours. So if white light goes in, white light comes out, and that's why ice looks white. Whereas if you um in the middle there, that pure water that had come in to fill the gap had melted and then it had refrozen, it had frozen solid without any bubbles, and that's why you can see that it's blue. So the colour of ice is really important. This is uh it's obviously me, and I'm sitting next to these odd little holes in the ice on top of the Greenland ice sheet, and they look a bit odd because they are. What's in them is there are little uh pockets of black dust. And what's happened is that because the ice is white, it reflects most of the sunlight. But if you get a little pocket of some dust that's a darker colour, and that means that when sunlight comes in, uh the sunlight is more likely to be absorbed instead of reflected. So it takes some extra energy. So it gradually heats up, and that will melt the ice just around the dust, and then more dust falls into the hole, uh, and so it you know heats up a bit more, melts a bit more, and you and that little patch of blackish dust, sometimes it's soot, sometimes it's other stuff, will kind of melt itself a hole down through the ice. And that's what you're looking at here. There are these little holes, they were about 25 centimetres deep here. They all had black soot at the bottom. Um, and and you can see very clearly the effect of a black thing absorbing sunlight while a white thing is reflecting it. And this, so these are called cryoconite holes, they're they're relatively common in on big ice sheets. They're more common where you get dust and pollution on all these little particulates that might start it off. But the reason they're important is because the colour of ice and its reflectivity really, really matters. And the way that scientists describe this is a word called albedo, which is a bit weird, but I'm gonna use it a lot, so I'm gonna stick with it. So here's how albedo works. If we get one unit of light coming in, there's a question about how much of that is gonna get reflected out. So if we assemble an axis here, so uh on the left hand side we've got black, so nothing is being reflected out. On the right hand side we've got white, so everything is being reflected out. And then we can measure the albedo, the reflectivity of lots of different types of substance. Uh so for example, the ocean's really, really dark. So if light goes into the ocean, it tends to get absorbed, so very little gets reflected back. The albedo of the ocean is about 6%, 0.06. If we look at the melt ponds, those bright blue ponds on top of the ice, they reflect just under half. So an albedo of 0.45. Sea ice reflects a little bit more, 0.6, and fresh snow reflects almost everything, 0.9. So you can see even different types of ice are reflective in different ways. And the reason that this really matters is because we think of light as a way to see, but really light is energy. And so different types of ice are basically controlling how much energy comes into the system and comes back out of it, and that is really important. And actually, this is one of the sort of counterintuitive things about ice is that it actually keeps itself cool in a way because it reflects away the energy that might melt it. And this is a quote from a paper written about the Arctic as a whole that says the other thing that snow does is it insulates, so it stops uh convective heat energy getting through because it's got full of air. So snow is one of the most insulative naturally occurring materials on Earth and one of the most efficient reflectors of incident solar radiation, which is light. So basically, ice has this weird property of having to be cold to exist, but then it's really, really good at stopping anything else being colder around it. And that matters quite a lot. Next little bit of physics that's really important is something we don't think about, right? Now, this is this of all the weird things about water, this is pretty much up there as weird thing number one. And it's that this scene can even exist. So, what you're looking at here is a picture down of the North Pole from a helicopter. I was in a ship that is not quite on this image, just off to the side, but that ice flow in the centre is about two kilometres across, so you're looking at a big, a big patch of ice. Here's the thing: in almost for almost everything else you can think of, if you freeze a bit of it, it will sink. The solid is more dense than the liquid. So, for everything else, if you froze a little bit of it at the top, it would then sink, and then you'd freeze some more and that would sink, and then you'd freeze some more and that would sink. So all the solid stuff would be at the bottom, and everything at the top would be in the process of freezing. But with ice that doesn't happen. Ice is less dense. When it becomes a solid, it actually spreads out, the molecules spread out so it floats, and it is thoroughly odd, right? I cannot emphasize how different our planet would be if ice didn't float, because then it would just all sink to the bottom instead of being this amazing reflector and insulator. So ice floats, that what that's weird. Next question. Nansen, when he was on his three-year expedition across the Arctic, frozen in, you know, he could carry a lot of stuff on Fram, but he couldn't carry everything. So here's the question then: where does he get his fresh water from? Because we know people die at sea after, you know, a few weeks because they can't drink fresh water, they can't drink seawater, right? It's too salty. So where's Nansen getting his fresh water from? And the answer is also due to the physics of ice. And I may I did this sort of accidental demonstration of this a few years ago. So I was um filming a BBC show called Operation Iceberg. We were up near Greenland, and I wanted to do an ice demonstration, and I thought it would be great fun if I had some pink ice to use for this demonstration. So one of the scientists on board was using a very pink dye called Rhodamine that does that. So I borrowed some from them, I put it into a tub of water with, you know, mixed it up with some water and put that in the freezer, and then I came back a couple of days later expecting to get my pink ice cube, and I got this thing instead. I got a pink hedgehog, and which was not what I was expecting. Uh, and then I looked really closely, and on the side of the pink hedgehog, you can see there's all these little tiny channels, and I realized that what happened here is exactly what happens to salt when water ice when the ocean freezes. So ice has a crystalline structure which is really specific. All the water molecules have to go in their specific place. So if you start cooling down salt water, what happens is that the water molecules get on with locking into their places. It's kind of nowhere for the salt to go. So the salt just kind of goes into the bits that are still liquid, it gets squeezed out, and the ice keeps building itself, and the salt is getting squeezed out into these tiny channels, and eventually it just gets squeezed out of the ice completely. And that's what happened with my pink dye. So I started out with water that was entirely pink, it froze from the outside because it was in a freezer, it was losing heat from the outside. So where it froze on the outside, it froze perfectly unpink, no colour, and the dye got squeezed out and squeezed out into these tiny channels, and then eventually just ended up in the middle. And if I had uh chopped this in half, which I was not inclined to do, uh I what I would have found is probably the middle would have been slushy and not frozen because it had all this dye in it, it couldn't actually freeze. But basically, this is what happens when ice freezes, it squeezes out the salt. So what is left, the frozen bit, is pretty fresh, and that's what Nansen was drinking. So they were taking sea ice from the water surface, from the you know, ice surface, melting it, which obviously requires fuel, but then you've basically the physics of the ice itself was supplying drinking water to you know to the people on the ships, and it uh they had many, many things to worry about. A supply of fresh water was not one of them. But this thing with salt is really important in the ocean. So when sea ice forms, it's it is the surface of the ocean freezing, so it freezes freshish and it squeezes the salt out. But the effect of that is it's effectively unmixed the ocean. So the water and the salt are normally mixed together, they're pretty much the same concentration generally across the global ocean. But then you unmix them, you create a very salty bit and a less salty bit, and that makes some weird things happen. Um, salt's really important for the internal structure of the ocean, and the reason that the ocean is not exactly the same salinity everywhere is because the ice, the formation of ice, is basically mucking about with it. It's separating, it's unmixing the ice, the salt, and the water, and allowing them to stay a little bit unmixed and get distributed differently. And this there's a really interesting example of this in the Arctic. So The Arctic Ocean underneath the ice on the sea ice on the surface is generally really deep, up to sort of three ish three to four kilometres deep in places. So there's a lot that can go on underneath the surface, and the ocean is normally layered by density, like a cake. So if water is warm, for example, it's buoyant, it's less dense, it tends to float. If it's salty, it's more dense and it tends to sink. So warm and fresh floats to the top, cold and salty goes down to the bottom, and the ocean will order itself in those layers. But if you take a line through the middle of the Arctic Ocean, you see something really weird. Now, normally, almost everywhere else on Earth, those the layering is dominated by temperature. Warmer water at the top, where it's less dense and buoyant, colder water underneath. And the salt doesn't make that much difference. But if you look at a map of the temperature, so this is like a slice through part of the Arctic Ocean, and the colours here represent the temperature. So purple is the coldest temperature, and the red is the warmest temperature. And you can see something really weird here, right? Which is that there's a cold layer at the surface, but then there's this warm bit right underneath, and this is relatively warm, right? Two degrees C is not that warm, but in the context of Arctic water it's pretty warm. So we've got this kind of warm blob that is sitting underneath the surface of the Arctic, and it's got colder water sitting on top, which is odd. But we can find the reason why if we look at the same kind of plot and we draw it in salt instead of in temperature. So here what we can see is that in that blob that's really warm, it's also really salty. So the ice formation has concentrated the salt, it's made this bit of the ocean really salty, and so it can exist down below the surface. And the reason that that is really interesting is that the Arctic has this warm layer away from the surface, insulated from everything that's going up above, and there is enough energy in that layer to melt the whole of the Arctic, all sea ice in the Arctic, but it doesn't because it's held down underneath by the salt that's in it, because the ice has separated out the salt. So salt's really important in the global ocean, and ice, one of the reasons ice is so important to Earth is that it makes some water saltier than other water. And then there's one final bit of weird little physics that matters a lot when it comes to why ice is important for planet Earth. And that's what happens when you melt it or freeze it actually, but we're gonna look at it as melting. So we've got here a nice little graph. Uh we're gonna add heat to some theoretical ice which starts off very, very cold at minus 100 degrees centigrade. And the temperature is up the side, so we're gonna add in heat and see how much the temperature goes up. And if you do this experiment, it looks weird because you add heat and it gets the ice gets warmer, but then you keep adding heat and the temperature stays the same for a bit, and then after a while the temperature starts going up. So, what's happening in the middle here? And what's happening in the middle is that this is a transition from solid ice to liquid water. So down here, when you've just got ice, if you put in some energy, the ice gets a bit warmer. Put in some more energy, the ice gets a bit warmer. And so that's quite that bit's quite simple. But in order for solid ice to turn into liquid water, you need to add in energy all by itself. So just to pull those molecules apart takes some energy. And what that means is you keep putting heat energy in, but that energy is going into pulling molecules apart instead of making the lick the mixture hotter. And then once you've turned it all into water, that process is finished, and then you can just you add more heat and you get more uh you get a higher temperature. And so this gap, this this stuff in the middle here is called latent heat. And it's really important because it acts as a buffer. What it means is that when you've got a mixture of ice and water, you can add some heat or you can take some heat away, and the temperature doesn't actually change. So you kind of got a bit of a buffer for heat, and that matters when it comes to how energy is flowing around the earth. And it's the reason, for example, that in the polar summer, when I was there at the North Pole in the summer, it's the reason that the actual temperature doesn't get warm because all the heat energy is just going into melting the ice, and it keeps going in and it keeps going in and it keeps going in, and it never gets to this point here where it's all liquid water. So the temperature of the Arctic doesn't change much over the summer, but it would if the ice went away. Okay, so that's a little that is a proper gallop through lots of little bits of ice physics. But the important things that come out of this is that the ice is because of because ice is such weird stuff, it is really important for the planetary engine. It controls energy entering the system because it can reflect away the sun's energy. It shunts salt around, it can unmix the ocean, which is really hard to do, uh, and it floats. So it stays at the top, having all of these effects instead of disappearing down to the bottom of the ocean. And then finally, it acts as a sort of energy buffer because it's got this very high latent heat, this energy that goes into it as it's freezing or thawing, either way. So ice is weird. I hope we have established that now. Um, so now this weird stuff. So obviously there's lots of water on Earth, some of it is ice. Uh, let's have a look at where that ice is. So, just to take a step back, ice comes in different forms in different places. Um I'm going to mostly be talking about polar ice, but let's just have a look at the types of ice that we get because they're a bit easy to mix up. So, what everything I've been talking about so far, that what Nansen was walking across, what you were looking at in that picture, that is sea ice. And sea ice is what you get when the surface of the ocean freezes solid. So it's the ocean itself that has frozen at the surface. And actually, Nansen was some of the science he did demonstrated that ice didn't form underneath and pop up like everyone thought, it actually formed at the surface. The next type of ice you can get is either a glacier or an ice sheet. They are different, but fundamentally, this is ice that falls on land and builds up on land. So, over Greenland, for example, there's definitely land underneath, but it's got kilometres of ice on top of it. And the same, the middle of Antarctic has, I think, three kilometres of ice on top of the land. So those are glaciers and ice sheets. And then the most familiar bit, perhaps, if you uh, you know, it's certainly in popular culture, is the iceberg, because that's what you get when a bit of a glacier or a sea ice carves, it falls off and it floats off into the ocean. So these these are the types of ice I'm going to be talking about today. They're not the only interesting types of ice on Earth. I'm going to mention very briefly the other one, which is glacier ice. Now, this this diagram's a little bit complicated. It comes from one of the IPCC reports. The things to look at are the yellow. So if you look, we've got a map of the earth, and you can see that there's lots of kind of yellow bits over Mongolia, Tibet, there's yellow bits down the side of South America, there's lots of yellow bits around Greenland, there's yellow bits in Alaska, you can see some in the Alps. These are glaciers. So this is glacial ice. And glacial ice is really important, um, partly because a lot of glaciers are providing water for communities that live downstream. So they're really important water buffers. But that's all I'm going to say about glaciers. They exist, they're important, and then we're going to carry on looking at polar ice and seeing where the ice is on Earth. So it's a bit, you know, it's uh easy, I think, sometimes to for, you know, if you're not, if you don't think about this all the time, it's easy to mix up the Arctic and the Antarctic. So let's have a look at those two things. Um, oh, let's start with that one. So the Arctic is an ocean surrounded by land. The Greenland ice sheet, which is all of that white stuff on top of Greenland, definitely land underneath, it's just got snow piled up and piled up and piled up on top and then squashed down. There's 1.7 million square kilometres of that ice sheet, it's very, very big. If you melted all of that, you'd get just over seven metres of sea level rise because it's on the land now, so if you add it to the ocean, you've definitely added water to the ocean, so it would, you know, water level would go up. Um, and then the sea ice, the which is not the ice sheet on Greenland, it's the sea ice floating on the ocean, that varies depending on the time of year, between sort of four and 17 million square kilometres. And now compare those numbers with Antarctica. So the Antarctic ice sheet is much, much, much bigger, um, sort of seven or eight times bigger in terms of its area. If you melted Antarctica, you would get about 58 metres of sea level rise. Now we're not even in the worst climate projections, on course, to do that, which is a good thing. But that's it's a lot of water is locked up on Antarctica. And then the sea ice is around the continent, and that kind of you know fluctuates a lot more, but generally it is uh it's got a bigger range basically than the than the ice at the Arctic. So you've got ice in these two different places. And the thing about ice is that it's usually moving, it might be moving very, very, very slowly, but it is usually moving because all of these ice sheets formed by weather coming over the top and then snow, it's almost always snow, it could be hail or rain, but snow accumulates and so they just keep accumulating. These ice sheets keep accumulating, and water is heavy. So if you accumulate and accumulate and accumulate and pile it up and pile it up, it starts bulging out sideways. So these ice sheets are balanced by the snow falling on the top is balanced by bits falling off the edges after it's all flowed out to sea. So these are not static things, they are slowly moving all the time. And just to give you an example of that movement, you will have heard, I'm sure, of we've talked about trying to reach the North Pole, the attempts on the South Pole, of course, the most famous South Pole story is that Captain Scott set off to try and get to the South Pole. He tried one way of doing it, you know, a certain set of methods. The Norwegians came along from the other side and basically picked him to the post in a much shorter period of time. And there's a whole mythology around all of that. But the famous part of the story, of course, is that Captain Scott got to the South Pole, discovered the Norwegians had got there first, had beaten into it, and then he started trekking back to his ship, and he didn't they didn't make it. So basically they died on the way. And the point at which they died is moving. So here's a map of that map. So what you've got here is uh the the red dot is the south pole, and the the line at the top that is the ocean, that's the southern ocean. So they started a little bit uh north of that big cross, they walked down that dotted line all the way to the south pole, and then they retraced their steps back, and they didn't get all the way back, they got about as far as that cross there, and that's where they died. But if we look at this on the map, a different kind of map, here we go. Here's all of Antarctica. Red dot is the South Pole, uh, the uh the cross is where they died. All of this bit actually is not land, that's a floating section of ice sheets. So it's really thick. Uh at some bits it's sort of 750 meters thick of just of ice floating on top of the ocean in a large bay. And because of this sort of conveyor belt of snow falling on the top and everything being pushed out sideways, it's gradually moving sideways. Um here is the picture that was taken. So uh people found very other members of his party found, I think it was them, I think it was later, found Scott's tent, found where they'd all died, found his diaries, understood what happened. They built a cairn over the bodies, and they took a photograph and then they left it. And what happened to that was that the snow kept falling and the ice kept moving. So what's happening is that as snow accumulates, it's buried, it's buried the uh cairn, and then that's also moving out to sea really, really slowly. And so a calculation, so we don't actually know where it is now, although there's been some estimates, a lot of people have been interested. Uh, a few years ago, somebody did publish a paper where they looked at this, and they said that suggests that the the last camp may reach the position of the current ice front around the year 2250, 340 years after they were first buried there. And by that time, it will be a hundred metres deep into the ice shelf, and it will be well below sea level. And they went on to say it's extremely unlikely that the bodies will emerge from a submerged part of the ice shelf, but instead they will likely just break away as part of a massive, massive iceberg and just float out into the sea. So that will be the final resting place of Captain Scott. And what's interesting, I think, about that is that he did actually make it back off the edge of the continent of Antarctica. It's just he didn't make it over enough ice to get back to his ship. So he sort of he did reach the edge of the continent. He just he just hadn't got all the way back to his ship. So these icebergs are shedding, and of course, icebergs are carving naturally because snow in, icebergs out, but of course, as we're warming the oceans, icebergs are carving more quickly, and so it's estimated that there's effectively twice as many icebergs coming off, or twice as much volume of Antarctic icebergs coming off the continent as there were before, you know, the whole global warming thing started. But those icebergs aren't passive, so let's look at one of them. This one was really famous. It's a absolutely giant thing, it's not this thing here, it's the big thing in the background. Uh this carved off the uh carved off that floating ice shelf in Antarctica a few years ago. Uh it got given a name because they all get named, and it's enormous, right? It's a hundred kilometers long. It's a colossal great chunk of ice. It lasted almost four years because it sort of bubbled around the ocean a bit close into shore and then it moved out to sea and it slowly melted, about 200 meters thick. So there is a huge amount of water in this, and this is the path that it took. So if you can see it started down here at the so the colour here tells you the date. So by the time we start here, January 2020, it'd already been knocking around the edge of the continent for a while. And you can see as it goes more and more towards the purple, the time the time goes forward. So it's it gradually makes its way out into the Southern Ocean all the way to South Georgia, doesn't hit South Georgia, which made a lot of people very relieved, um, and then sort of drifted back into the Southern Ocean where it eventually melted. So it lasted four years, absolutely astonishing. But it wasn't passive. This isn't just melting freshwater, it's affecting the ocean around it as it goes. And very recently, so now we've moved on a bit from you know trekking around in seal skin, we've got more modern scientific techniques. And so a group of scientists from the British Antarctic Survey and other places went and visited this iceberg on a ship and used underwater autonomous vehicles to sort of fly around it underwater and measure what was going on around it. And they found this really interesting thing. So here's one of the pictures from the paper that they published. And what you're looking at is the colours of the ocean, effective colours of the ocean on the left-hand side. So we've got warmer water at the top where it's a bit orange, and colder water underneath. And then here's this colossal iceberg, so it's a bit thinner than 200 metres at this point, about 140 meters deep, floating along. But the interesting thing about this iceberg is it's so colossally deep that it is deeper than the mixed layer at the top of the ocean, than the warm layer. And the nutrients generally in the ocean, the nutrients are all down in the cold water, and then the warm water is nutrient-limited at the surface. So you don't get as much live as you could because it hasn't got enough nutrients. But what this iceberg was doing was it was melting from underneath, and that melt water, because it was fresh, was buoyant, so it was rising up around the sides of the iceberg, and it was mixing in with the water on its way around and effectively carrying sort of water upwards, so it was mixing in with all this nutrient-rich cold water, carrying it up, kind of breaking the layers a bit and producing this plume of nutrients. And so they estimated that about 36 hours after the iceberg had drifted past, there was a big algal bloom right behind it because suddenly there are all these nutrients that were brought up to the surface. So, so even when it's you know on its way out to sea and melt, ice, you know, ice is not passive, it's always doing something. And so this is we're opening the door now on modern exploration. And so, this is you know, some examples of what uh this was a 2018 expedition that I did. This is the one where we we went to the North Pole on that ship, Udin. You can see an enormous team, no dogs, uh, electric skidoos. I think those are the first electric skidoos that have gone that far north, and it's still challenging to get into the ice, it's still challenging to study it, but it's not impossible. So I want to tell you about Mosaic, which is the modern uh the sort of updated version of Nansen's Fram expedition. Because the thing no one has really been able to do very much since then is be in the sea, in the Arctic, in the central Arctic, during the polar night. All these expeditions tend to go in the summer because you can see, right, and you can get through the ice and it's accessible. But what is missing is modern data of what happens during the polar night. And so this is what the mosaic expedition was set out to do. So this is the German ship, the Polarston, that the whole thing was built around. And it the right the reason it's called mosaic is because ocean scientists are utterly terrible with their acronyms. They've got this obsession with acronyms, it's awful. I've done, I'm not even joking, I've done uh expeditions that have been called both teabag and mocker. It's ridiculous. Um, so anyway, the multidisciplinary drifting observatory for the study of Arctic climate became known as mosaic, made everyone very happy. But this was not just a single ship freezing into the ice for three years. Things have changed a bit since Nansen went. This was seven ships. Uh, the Pilar Stone was a sort of central floating body, the other ships were ferrying people in and out because no one was actually going to stay for the whole time to give different scientists a turn as well. And the so the people were sort of swapping, taking shifts on this ship. 20 nations, and because the ice had changed and the aims had changed, they didn't go for three years like Nansen did. The plan was they would go for one year. The plan was basically the same: that they would go to the Russian side of the Arctic, freeze in, and then drift with the sea ice for a year to the other side. Uh, and they did. The complication was that they left in September 2019. Six months later, the world shuts down, and they're still there. And Mosaic did keep going. I mean, they they reduced the number of legs a bit, so some people had to stay a bit longer, some people didn't get to go at all. Everyone who did go was quarantined for a long time before they were allowed onto any of the ships that went north, but it worked. So here's what here's what Mosaic did. Um, if we look at that area of the Arctic, so that's the same as the Nansen uh sort of map. They started up at that red bit up there, and the the colours is they sort of they started their expedition in September, but the colours start in January, which is a bit unhelpful. But anyway, so they they froze in in September and they floated, uh they repositioned it once, I think, along the way, and then they floated almost as Nansen did, sort of around, didn't quite get to the North Pole, and popped out of the sea ice a year later. So, just to give you a little taste of what that might be like. This is actually a graphic from one of their papers, and I thought that since they bothered to put it in the paper, I might as well use it for what it's clearly supposed to be used for. So they called this their polar clock, but what I want you to do is to watch the segment at the top. So at the top there, it's December, it's pitch black, right? It hasn't been light for a very long time, it's very, very cold. And what's going to happen is the clock is going to go around and we're going to see what you know what the scientists were seeing over a year. So you can see that it stays dark, and when it thaws again, there's just solid ice everywhere. But as the months go into the spring, the ice starts to thaw and to break up, and then by July and August, you're getting quite large areas of open water. In September, you've got the maximum, but then the dark comes back and the freeze-up starts, and then you're round back into the polar winter. So, so this is what this is what the year looks like if you're on that ship frozen in. I have colleagues who lived in that darkness for months. One of them told me that uh he said after when he came back, he'd sort of his eyes couldn't focus on the distance because he never had to look at the distance because it was just so dark, there was nothing to see. So So he you sort of had to adjust to being able to see something further away than the other end of a ship, which is a bit weird. Anyway, so this is modern science, right? They've moved on from Nansen's era and one guy measuring temperature with a bucket. There was an incredibly sophisticated array of instruments. They were studying biology, they were studying chemistry, they were looking at the clouds, they were looking at energy coming and going, uh, all of this while drifting across the ice. So, and this, when you get down to it, looks like a small city. And in the way that the Fram must have done. This is one of the maps from the papers, uh, the black sort of splodge at the centre, that's the ship, the Pilashton. And then you can see there's all these all these things around it. There's spaces allocated for studying snow, there's spaces allocated for looking at biology and optics. They basically built a city, a small village on the frozen sea ice, and then the whole thing drifted across the Arctic and they put instruments out around it. And the conditions were, you know, challenging. So this is in a day where it's probably warmer than what Nansen had to put up with. So the uh what have we got here? The ice temperature is the blue one, so that goes down to minus 40. The air temperature was going down to minus 20. This is in November. And then what they could do is see the things that Nansen was living in the middle of but could not see. Uh so what you're what this what these two images at the bottom are here are, so you know at the beginning I said that when the ice comes together it would crush a ship. Well, that puts strain on the ice, it squeezes it. And now we have satellites that can look and actually measure that squeezing. So what you're looking at here is patches of ice that are sort of 200, uh maybe it's a hundred kilometres from top to bottom. And those brightly coloured lines are where the ice has been squeezed and deformed, and that was what always killed Arctic ships. Because if your ship got stuck in the middle of one of those bits, it would basically get crushed, sheer. That was the end of it. And they could see all of that. So obviously, there's loads of science that was done in this expedition. I can't tell you about all of it. The big message, the big news from Mosaic that surprised everyone was how rapid the drift was. That they, even though they were frozen into the sea ice, the sea ice was moving much more quickly than they thought, and it was moving much more than they thought. And actually, there's a very interesting uh, and the polar, the transpolar current's still there. The one very lovely direct comparison with Nansen's measurements is this. So there's been this rule of thumb uh for a hundred more years that Nansen came up with, which said that the ice drift speed is about 2% of the wind speed. And and here, that so that black line, so we've got wind speed on the bottom here, we've got drift speed up the top. The black line is Nansen's drift law, that the ice drift speed is 2% of the wind speed, and the red dots are the data from July 2020, and the blue dots are the data from January. And you can see that for the summer, that it's pretty good, right? Nansen, you know, Nansen and Ekman knew what they were doing. They came up with some good data there. So during the winter, everything's obviously moving a bit more slowly, but in the summer, you know, Nansen's rule of thumb pretty much works. So, anyway, there's this is how this is an you know a very special expedition that probably won't ever be repeated because there might not be enough ice left by the next time it comes around. But uh it was they are still analyzing the data from this, it's it's an extraordinary amount of data. So, very quickly, then, this is the part of the story you'll be much more familiar with. The ice is changing. Global warming is all about the ice accumulating extra energy, and that energy has to go somewhere, so it goes into water, and warmer water will melt ice, warmer air will melt ice. So, this is a you've probably seen pictures like this in the press. What we've got here is a map of sea ice from 1985, and then on the right from 2021, and the colours indicate the age of the ice. So, some ice is so thick that it will last all the way through the summer, it'll get a bit thinner, but then September will come and then it will thicken again over the next winter. So, this is multi-year ice that never an ice flow that never thaws completely, it just grows and shrinks and grows and shrinks. So you can see that back in 1985, the red is four-year, four plus years multi-year ice. So that's ice that has survived four whole annual cycles or more, and there's a lot of it, and you can see that in 2021 it's basically confined to a very narrow line along the Greenland coast. Um, and then you can see you know the other colours for other years, basically almost everything. You know, we look at those maps of the Arctic and sea ice extent, it's not just the extent that matters, it's the fact that that ice is different. It's only been there, you can see here, for less than one season in a lot of cases. So the ice is changing very rapidly, we know why that's happened. This is a plot from a, I think it's the same paper, and along the bottom are cumulative carbon dioxide emissions, and up the side is the September sea ice extent, which is the minimum. And you can basically see that the more carbon dioxide you put into the atmosphere, the less sea ice there is in the summer. And of course, there's a debate about how, you know, how many years it's going to be before we get to zero at during the summer or in the at the you know at the ice minimum. But we know we know why it's happening, and you know, these the sort of I won't show you many of these plots because you've seen them before, I'm sure. Uh multi-year ice is coming down, ice more than four years old, almost disappeared. And so this is the reality of the Arctic we have today. And that has profound consequences for the rest of the planet. But while that is going on, we are still learning how the ice itself works. And so it's just one example of that. I talked about reflectivity from the ice itself, the albedo. Well, it turns out that biology that is in and around the ice also is reflective. And here's a paper on that recently, and it's just some examples. So, for example, there are the cryoconite holes at the sort of second one down on the right there. Number six here, that's algae growing on the ice. And it's coloured and so it absorbs sunlight. There are, it turns out that number one, top left there, those are ice worms. I did not know until I found this paper that ice worms existed, but apparently they do. And they have, you know, you can imagine one of those making its own little cryoconite hole. Um, you know, insects. Oh, this one's funny. In the paper, it says something along the lines, bottom left here, where the penguin is, it says something along the lines of um penguin uh it's something very uh, it's made to sound very nice, but it says something like penguin production fertilizes algal ice. Basically, penguin poo provides nutrients and then stuff eats it. But that stuff is then absorbs sunlight and warms things up. So even the biology on top of the ice is changing the energy balance in the ice, and we don't know, we don't know whether as climate change progresses, there's going to be more or less of this. So, this is just one of the examples to say that, you know, as we are understanding, you know, as the ice is disappearing, we are still learning how it works, we're still learning what it's doing. And obviously, there is a race to understand what it has been doing before it disappears completely. So, a little bit about the future. Again, I'm sure you've heard this before. There is a process called Arctic amplification, and basically what it means is that the way the planetary engine functions means that the Arctic is warming about four times faster on average than the rest of the planet. So, climate change is about the total amount of energy on planet Earth, but a lot of that extra energy is concentrated in the Arctic and it's warming it up. And the plot here shows you the change from 1980 to 2024, and basically the redder it is, the bigger the temperature difference. So you can see that in September, October, November, uh just over that period in 2024 it was much warmer than it was in uh 1980. So basically, this is Arctic amplification, that the Arctic, the ice there is vulnerable. And of course, the Antarctic also has its ice and is also melting faster, and you know, those ice sheets are also the subject of very serious study. And then alongside all of that, oh, so yeah, alongside all that, humans. We haven't talked very much about the humans. So humans want to access the Arctic. The Arctic certainly and the Antarctic actually have been protected by the fact that ice is very inaccessible, it's hard to get into. But humans have ships, ships are getting bigger, they're getting more powerful, they're getting better GPS, and they are having less ice to contend with. And so there's been a these are some of the major shipping routes. The Northwest Passage, which is the green one, was very famous because Franklin tried and famously failed to make it through the Northwest Passage. And then there's these other two. Well, now, more and more and more, as the ice disappears, this is the projected annual ice, you can see as it goes more and more yellow, that's time going forward. So at the dark lines at the top are now, and as we go forward in time, the minimum gets lower and lower and lower. And basically that means the Arctic is becoming open ocean, and that means ships are going to go there. And if ships go there, inevitably, unless they're all either nuclear or electric, they're going to produce particulates which fall on the ice, which are going to absorb more heat, which are going to speed up the cycle. And of course, what an icebreaker does by definition is breaks ice, so also potentially breaking it up. But it may well be that there's so little ice during the summer that they won't need icebreakers. And that's something shipping companies are excited about because being able to get between China and America without having to go the long way around obviously saves you a lot of fuel. It's not necessarily good for the Arctic. So there is a huge interest in the shipping industry in crossing through this ice. And then there's all of this. Suddenly, everybody is an Arctic nation. China has loads of icebreakers. The most ice, the greatest number of icebreakers in the world at the moment are owned by Russia. Um, everyone is talking about these big countries in the big geopolitical arguments of the day. We want to exploit oil, rare earths, other minerals. It's obviously a power play. You know, Russia already put its uh flag on the unacknowledged by everybody else, but put a flag on the seafloor at the North Pole. So the Arctic is also becoming a big geopolitical playground. And all of these things are happening at the same time. We have the physical changes taught by climate change, we have the changes coming in access and in shipping, and then we've got the fact that now it's being seen as part of the chessboard for geopolitical battles. And basically, there is no predicting how this goes at this point, other than the physics, right? The physics is definitely going in one direction and we can change it. Um, but all of this is suddenly making the the ice, what used to be ice, look like a place for countries to come and play. So um there's no good way to finish this, I have to say, because ice is fascinating. It's a critical part of how our planetary engine works now. We are used to a world in which ice does what it does, but it's decreasing. It's about 10% of the planet is now covered by ice, and that is going down all the time because we're burning fossil fuels. And it's this is a picture of the expedition I was on in 2018. I'm somewhere down there. On these were these were my colleagues' experiments and mine. In fact, I think I might be there. Um and so I spent a month actually working on the sea ice, walking on and off it every day on this two-meter thick ice flow. It's amazing how quickly you can walk around in it and forget you're walking on the ocean because you're just walking around and it feels like land. And I spent two months doing that, everyone there is thinking about the climate, studying the climate, and it was only when I came back that I thought I will probably live to see a day where this isn't possible anymore. And that hurt. So that's where we've got to. Ice ice is fascinating, it's physics matter to the planet, it controls all these interesting things, it's not lifeless either in terms of human or non-human biology. It's changing, but we do still have a choice about the future. That plot where carbon dioxide, you know, carbon dioxide emissions are basically directly correlated with ice loss, we can still change that if we choose to. And if we want a properly ice functioning planet in the future, we will have to do that. Thank you.