 All right, yeah, so thank you very much. And thanks for the opportunity to presenting my research here today. So yeah, we're going to make a little excursion now to more northern more areas of the planet. So in the Arctic where there is permafrost. So yeah, you can see in the background here the type of landscape we are interested in. So it's a typical lowland tundra region here. It's a picture of the Lena River Delta in northern Siberia. That's where we have field sites. And yeah, you can see this polygonal patterned ground here. This is a very typical feature and form there. And yeah, I'm going to talk a bit about this and how this system responds to... Okay, yes. Ah. Should we start over again? Okay, yeah. So this is the kind of system we're interested in. And yeah, just a brief intro to permafrost because not everyone might be so familiar with that. So permafrost just refers to state of the ground that it's low zero degrees Celsius for at least two consecutive years. And this condition is found in about a quarter of the northern hemisphere, this land area. There are huge amounts of carbon stored in these areas about twice as much as contained in the entire atmosphere. And there's also a lot of critical infrastructure in this region. So it's a big question, how permafrost falls and how this is going to change in the context of climate warming. Yeah, so one key complexity in this system which is I would argue often neglected is the presence of excess ground ice. And it's also why my title is called Ice-Rich Permafrost Landscapes. So that means that there are deposits where there's so much ice in the ground that its volume exceeds the poor volume of the soils. And when this ground toss or this ice melts then it leads to a collapse of these landscapes. Yeah, because the ice was kind of consolidating the red. And it leads to the formation of different kind of landforms. So we have formation of far lakes. It can lead to better drained areas to formation of gullies or thermo-erosional valleys. We observe far slums in regions where there's a lot of buried glacier ice and also degradation of these ice wedge polygons which I showed in the beginning. And yeah, all these processes are quite local and rapid. And so an often neglected in like large-scale model assessments of permafrost models. And so I will try to present an approach how to starting this and I will do this for this last case of these wedge polygons. All right, so at the top, you saw these typical polygonal patterns. They're typically water-covered centers and elevated rims between these polygons. Underneath the surface, there are huge ice wedges. So they form due to cracking of the ground in very cold winters. Then you get accumulation of snow in these cracks and in the next summer and winter this will melt and re-freeze again over hundreds of years, accumulate huge amounts of ice in the subsurface. So it leads to a very heterogeneous distribution of ice on the subsurface. Now if this protective active layer, which is the part of the permafrost which also freezes every year becomes deeper, it can lead to melting of these ice wedges at the top. And what we then see are these degradation features, water impoundment in these troughs between the polygons and subsidence of the rims because the ice in the ground is melting and the ground just subsides. If this continues further, it can lead to an inversion of the topography from these low center to high centered polygons. It often increases the drainage of the landscape and we have completely shifted energy and water balance these landscapes. And it's also very relevant for decomposition of carbon in these soils. So the first objective here was to set up a model which is able to simulate this transition of these polygons. Then we do that for our field site in the inner river Delta in northern Siberia. We have a very long data record here for about 20 years to evaluate our models. And if we look at this island, so it's about two kilometers in diameter, we see that in different parts of the landscapes, actually the polygons look quite different. We have like these undecrated low centered polygons in many parts. We see some degradation features in other parts, quite advanced degradation and drainage of the landscape in some parts and also strong degradation but with more water locked conditions and water filled troughs in some areas. And so even though this is all subject to the identical climate, so the next, the second objective was to investigate with the hypothesis of how and how far local hydrological conditions control this evolution of these ice wedge polygons. To do this, we used what we call a tiling approach. So instead of really doing a 3D modeling of these polygons, we split the landscape into units. We just looked at polygon centers, polygon rims and the troughs in between. Did some idealized assumptions on the geometry of the system and then integrated these different parts into what we call tiles which represent all the polygon centers, rims and troughs in a certain area of the landscape. And now with each of these tiles, we would associate an instance of a permafrost model which is a vertical 1D model. It takes into account the microtopography. So here we would have higher elevated rims, lower centers and troughs. And what we have here in this white-tish color indicated is actually a representation of these very ice-rich ground, these ice wedges. So in this model there's implemented an excess ice scheme. What it does as soon as the thawing front goes into these ice-rich layers, it will lead to subsidence of the ground and a change in microtopography. What we also implemented is lateral processes between these landscape tiles. So especially lateral transport of snow and water according to the microtopography of the terrain is a very important factor. And then in order to control these hydrologic conditions which I mentioned, we connected these troughs. It's sort of a boundary condition to an external water reservoir with which we can control the drainage. So if this has a low value, we would take water out of the troughs. If it has a high value, it would lead to inundation of the system. Now I would just like to show two example simulations for this system. So it's a 60 years run. It's actually, it goes to 2040 here, but it's not a projection. It's just repeating current day climate conditions. And we have centers, rims and troughs. First case is for rather wet waterlocked conditions where we see these stable low centered polygons for about the first decade of the simulation. So you see up here centers of water covered, water table is above the soil surface. The rims are rather dry with water table within the active layer. And down here are the troughs. And now after about 10 years, the climate or the active layer gets a bit deeper and now reaches actually into these ice rich sediment here. Or it's almost pure ice actually, which is represented here in this white color. And now it, yeah, these troughs start to subside and this process continues for the next years. It's kind of feed it positive feedback loop due to, because of this, yeah, ice from the ice wedges is then in the active layer. It increases thermal conductivity. It increases ground heat fluxes, which leads to deeper active layers and so on. And so, yeah, this subside in here for about one meter or so, about a period of 20 years. And concurrently also the rims of these polygons start to subside and get wetter and wetter. After about these three decades, the rims actually subside below the level of the centers and what we then see that the centers suddenly run dry. So that's exactly what I showed in the beginning. Now we have much shallower active layers in the centers and yeah, wet conditions in the rims and the whole thing reaches kind of new equilibrium state for this climate. Briefly another case that's now for the drain conditions. So it's all same, but for this water reservoir level, again, we have this low centered polygon phase in the beginning, even though we drain water out of the troughs, the centers stay water covered or wet because of the elevated rims, which are kind of in between. It's like a bathtub, you can imagine. Yeah, and this state is now stable for about three decades. And then there's in the forcing data, particularly warm year where this degradation sets in. We have deeper active layers. And again, it's fed by a positive feedback loop. We have subsidence and degradation of these ground ties for next two or three decades until the end of the simulation. The rims also start to subside a little and what you can see that now the water tables everywhere drop considerably. And the final state here is entirely different regarding the initial state, regarding water coverage of the landscape and associated energy fluxes. Okay, so yeah, if we now come back to our study site, so our simulations should be seen more as proof of concept, I would say, but they also give some supporting evidence for the critical role of these local hydrologic conditions in this system and might add some explanation to why we see for the identical climate, these quite different types of polygons in such a small region. And yeah, that's what I would like now to conclude. So first of all, I would like you to maybe to remember that in these permafrost regions, we might have a lot of ground ice and that this leads to quite rapid and drastic changes in the landscape, which is not taken into account by almost all large scale models which try to project permafrost states in the future. Yeah, this tiling approach might be also a tool to reach a bit this scaling and possibility to integrate these small scale processes into larger scale models. And finally, yeah, we showed here that this is possible to simulate this transition of these ice which landscapes by coupling classical permafrost models which just have the heat transport with, yeah, schemes which also take into account the dynamic topography of the terrain. This out, we published this also in a paper that's been published about a month ago in the cryosphere and the code of our model is also available on GitHub if you're interested. You can also talk to me later and that's it. Thank you very much. Thank you, Jan. We have time for a question or two? So yeah. Jan, can you sort of summarize the question? Okay, yeah, so the question was if I got it right regarding how these different hydrologic conditions, if they actually match with what we see in the field or have, yeah, so it's a quite shallow landscape so you don't have large gradients. It's really super flat. So this is an island. So in this case, typically be that at the margins of the island, you would have a better drainage towards the river which is surrounding the island and more in the central parts of the island. Yeah, you would tend to have more waterlock conditions. So that's a bit, yeah, there's what a correspondence I would say, but in our model, it's quite, I would construct it or artificial boundary condition. There is not this external water as a word. It's just a measure of prescribing different conditions there, yeah. I think I saw another question here, Jaya. Of the entire permafrost area, I would say, I don't have a number, I must admit, in the cold continuous permafrost, which makes up maybe half of the permafrost region, it's quite dominant landscape type in the lowlands. So especially it might not be like the most dominant form, but there's a lot of carbon in this, especially these landscapes. So we have deposits from the late Pleistocene that they're called Yadoma, and they have really a lot of carbon. They're especially not so, like they're not everywhere, but it's very like localized, yeah, deposits where we have a lot of carbon and should really be sure what's going to happen there. Thank you, Jan. Yeah, thanks.