CCI Science Lead Dr. Annett Bartsch introducing the Permafrost project

Hello, my name is Annett Bartsch, I’m the science lead of CCI permafrost. Now the permafrost is ground, which stays at temperatures below zero degrees Celsius for at least two years in a row. This actually means that at the very top, at the land surface, we do not have permafrost. This is because the surface starts thawing a little bit in the summer. So the permafrost starts then a little bit below the surface. Now, when we want to monitor permafrost, we need to actually, if you want to really measure the ground temperature, we need to make boreholes. And drilling such holes, is logistically quite demanding.

It is costly, and there are not so many boreholes as we would need because there’s quite a lot of dense surfaces underlain by permafrost. The northern hemisphere, we have permafrost occurring for approximately 20 percent.

So we need some approach to fill these gaps to monitor what is happening in the ground. And, of course, satellite data might be interesting to use, but this is very challenging and due to the fact that it’s a subsurface phenomenon. There are two major ways to address this. First, we can use models and feed these models with information. With parameters which we can measure from space and which have an impact on the ground below the surface? That’s, first of all, the temperature at the land surface. This is something what we can comparably easily measure from space. Then we need to consider the properties of the soil. We need to make assumptions about the heat conductivity of the soil.

And then we also need information about what is happening on the surface. Specifically the presence of snow and the amount of snow in the winter and how this is varying over the winter and from year to year. And this is also influencing the heat conductivity, how the changes in the air temperature are translated into into what is happening in the ground. So snow is something what we can observe from space, the land surface temperature, and we can use land cover information as a proxy for soil conditions.

And the second approach, is to look for proxies.

In many cases, we have ice in the ground. We have ice lenses or ice wedges and when temperatures are increasing and this ice may melt. And when then the water is flowing way, the terrain is changing, the ground is subsiding. And when there are depressions, they could fill with water. So we have small ponds or lakes forming. And this is something that you can already observe from space, with high resolution satellite data. And we can also measure this subtle changes in terrain with SAR interferometry from space.

So this is an alternative to using the model approach. But this is usually limited to local applications. So what we are interested in is to cover, the large parts, the entire globe.

So we are in CCI, we are using the modeling approach in the first moment.

And at the moment, we can go back to 1997, at spatial resolution of one kilometer. This one kilometer, is determined by the input data. Specifically the land surface temperature and the snow information here.

But in addition, we compare the results that we get, to these proxies at the land surface, these lake changes and terrain changes. Now, what is very challenging is permafrost in mountains. If you imagine, with one kilometre spatial resolution, you have a lot of terrain variation in the mountain area. And these terrain variations are determining where the permafrost is present, to a large extent. So here we, in addition, look at so-called rock glaciers. And they are permafrost, not glaciers. Those are rocks, in the gaps between the rocks, there is ice present, in case that there is permafrost.

At steep slopes, this this mixture of rock and ice is moving down the slope. And as long as this is moving, we have actually permafrost present. So this is our assumption. And these kinematics of rock glaciers are something that we are able to observe from space. And we are looking at that in addition for mountain areas.

So we provide this information for selected regions, for the Alps, for Scandinavia, for the Andes mountains and also Antarctica.

And for modelled permafrost the information that we provide here is not just the temperature, but also the extent of permafrost. For that what is usually used is the temperature at two meters depth.

And then a very important is this soil layer, the depth of soil layer on top, actually, so that’s the active layer. It can range from few decimeter to several meters, depending on temperatures and soil properties. And this active layer thickness is very important for microbial activity and it’s important for the stability of infrastructures. So the microbial activity is determining, or influencing how much of the carbon stored in the ground is released into the atmosphere, and depending on the witness conditions, as well as CO2 or methane. And there are lots of infrastructures in the Arctic, industry or settlements, which are impacted by the stability of the ground.

So we provide this information, this active layer thickness, in addition to the permafrost extent and the ground temperature at depths ranging from zero centimetres, so the surface, and one meter and down to 10-meter depth, plus the information on rock glaciers in the mountain regions.