The ecotopes in the Sor Rondane Mountains can be selected according to five factors:
1.Orientation of the slope (N, S)
2.Availability of a melt water (position close to a snow bank or not, it also
depends on the wind direction and position on the slope)
3.Stability of the rock (the crusts require a long time for development)
4.Type of substrate (rock, soil...)
5.Fertilization (presence of birds colonies)
Interestingly, the availability of melt water on the Northern windward slope of the Utsteinen nunatak strongly depends on the relative position on the slope. At the foot of Utsteinen, there is a high snow deposition, but higher on the slope, the snow deposition is low and on the top of Utsteinen, the snow deposition is high again.
This observation can be explained by the aerodynamic properties of the nunatak. As the wind hits the nunatak, it gets forced upward, which increases its speed and lowers the pressure according to Bernoulli's principle. This is the so called "orographic" lifting. The highest wind speed is observed at the highest levels of the slope, and the wind erosion of the rocks is also the highest there. There is no snow deposition and, as a result, there is no melting water and biological crusts.
In contrast, at the foot of the nunatak, the wind speed is relatively low and we can see an intensive snow deposition here. As a result, there is a lot of melt water and a high number of biological crusts. Such high numbers of biological crusts can also be observed behind the top of the nunatak where the wind turbulence leads to intensive snow deposition. Crusts develop on the borders of the snow banks in the rock cavities. The same situation can be observed also on the Utsteinen ridge. It is relatively flat and there is no strong increase in the wind speed. Snow deposition is high and there are a lot of biological crusts.
Another type of communities develops near the petrel colonies. They are dominated by a green algae (Prasiola) and associated with bird's faeces and dead bodies. The snow deposition is relatively low in this area, so I am not sure which the source of water?
The wind seems to turn, so that I will probably be able to start the filtration tomorrow.
Last Saturday, we have helped to unload the containers with cargo that arrived with the traverse. Today, we have continued to unload them. I still didn't find my box sent from Liège, and it is probably in one of the remaining containers. Alain and his group went to the Antarctic plateau to check the route to the place where the meteorite team will work. Saturday evening, we had a nice Christmas party!