SnowFlurry 22 2016/17 | The summer firn

In the correct manner, "firn" - as we have all been told countless times - would only be snow that is at least one year old and has therefore survived a summer. This is primarily found on glaciers, in the so-called nutrient zone or where avalanche deposits can last for several years. A well-known representative of an avalanche cone, which usually remains in place for several summers, is the ice chapel on the Watzmann.

In skiing terminology, "firn" refers to those types of snow that have been created by melting and are suitable for skiing, regardless of their age. In practice, this almost never includes snow that is more than one year old. Snow that has been transformed by melting, which does not fall into the linguistic group of "firn", is usually less suitable for skiing - for example, broken harsch, sulz, slush = rotten snow.

There is the Zischfirn: a softened harsch cover (= sulz on a melt crust), named after its typical sound when it hits the snow surface after each turn. Next to it is the Trittfirn: soft, moderately soaked old snow in which the original (dry) snow form is still faintly recognizable. And today's star: the summer firn, also known as "summer snow" or just "summer snow". Information on summer firn is thin on the ground and the term itself is relatively unknown.

Properties

Summer firn therefore again has a lower water content than sulz or rotten snow. As a result, summer firn - regardless of whether it is frozen or isothermal - no longer collapses, it is solid. It is usually characterized by a wavy or perforated and discoloured surface. This is formed by so-called cryoconite - material from the atmosphere that collects in minimal depressions, where it increases radiation absorption due to its darker color and thus promotes snow melting at certain points. The darker color of summer firn comes from the melting of the snow cover, whereby the embedded dust from each melted snow layer ultimately collects on the surface.

In addition, a red-colored green algae species is regularly found on summer firn, which finds good conditions for photosynthesis due to the reflection of the white gold and protects itself from radiation damage of the high-energy, low wavelengths (UV) through the stored dye.

Summer firn can be frozen, i.e. hard as a rock, or slightly softened, whereby you can only sink in a maximum of a few centimetres. The Schneestöberer has already skied the best summer firn at over +37°C in valley locations. When summer firn softens, which has frozen on the surface at night due to radiation, the snow quality changes from a morning wash rump due to the irregular surface to a casually slushy, but hardly reminiscent of sizzling firn. The risk of avalanches in summer firn is limited to sliding snow avalanches due to the high firmness and homogeneity. There is no more diurnal ascent because the snow always remains firm. It is no longer possible to break through - no matter how thick the snow cover is. Nevertheless, time planning is necessary due to the quality of the turns: if the surface is frozen, you rattle down, if the surface is too soft, summer firn usually slows you down a lot and no longer allows a great descent.

Note: The transitions between all snow types are fluid, classifications with sharp boundaries only exist in our heads.