MOSAIC (Modelling of Snowmelt And Its Consequences)


Project description

The conceptual framework is dealing with different aspects of snowmelt and its consequences. Particular regions at high latitudes are to a great extend characterised by the existence of seasonal snow covers. Their spatial structure and course of development, metamorphism and depletion are consequences of climatic and terrain conditions, as well as their dependence on structure and state of the sublayer. Snow covers strongly modify not only the regional climate, but also geomorphic processes, soil development, vegetation and fauna, and finally life conditions and economic possibilities by influencing energy balance and water budget. At the end of the snowmelt period, energy balance and water budget have strongly changed in comparison to the previous snow-covered situation.

The snowmelt period not only is a transitional season, but also possesses its own dynamics, which is of great importance, e.g. for nutrient and sediment budgets. The occurrence of so called slush streams, periodically or episodically observed in arctic and subpolar areas, can reach catastrophic dimensions under extreme meteorological conditions. During these events, an activation of geomorphic and hydrologic processes takes place, which would never be possible under so-called 'normal' conditions. Short-term sediment transports, caused by extremely high discharge values, can dominantly contribute to the total sediment yield of a drainage basin.

The research work within MOSAIC included:

Slushflows:

Slushflow is the expression for the downhill movement of water-saturated snow. The movement is restricted to channels and occurs on gentle slopes of less than 20°. They can therefore be easily distinguished from avalanches, which are normally triggered on slopes with an inclination of more than 20°. The extent of slush flows has a wide range. High-energy variants show extreme velocities of over 20 m/s and runoff values of up to several thousand m3/s. Slushflows have been reported from Arctic and subpolar regions, but there are also indications of their occurrence in the Swiss Alps.

A new physical concept for the mechanism of slushflow release is being developed based on the assumption that mainly the development of a hydrostatic pressure gradient due to the generation of an inclined water level in the snow cover is responsible for the initiation of slushflows. The snowpack condition is decisive for the release of slush flows, since the hydrostatic pressure gradient is compensated by the shear stability of the snow matrix as long as the pressure gradient does not exceed a certain threshold value. Another part of the project is the investigation and evaluation of the model prerequisites for the development of a physically based and fully distributed snow melting model.

The slush flows were investigated in two expeditions to Spitsbergen and in two field campaigns to Kärkevagge, Northern Sweden

Project Leader:

Prof. Dr. Dieter Scherer (TU Berlin)

Prof. Dr. Eberhard Parlow (Universität Basel, Schweiz)

Publications

Gude, M. & D. Scherer (1995):
Snowmelt and slush torrents - preliminary report from a field campaign in Kärkevagge, Swedish Lappland. Geogr. Ann., 77A(4), 199-206. DOI: 10.1080/04353676.1995.11880440
Link

Gude, M. & D. Scherer (1998):
Snowmelt and slushflows: hydrological and hazard implications. Ann. Glaciol. 26, 381-384. DOI: 10.3189/1998aog26-1-381-384
Link

Scherer, D. et al. (1998):
Atmospheric and hydrological boundary conditions for slushflow initiation due to snowmelt. Ann. Glaciol. 26, 377-380. DOI: 10.3189/1998AoG26-1-377-380