Snow, landscape and people: Fieldwork in Norway

Project Details

Snow surveys were completed in Heidal valley, Oppland, along three discontinuous transects from valley bottom to top, two on the sunny side and one on the shady side. The transects were surveyed twice, firstly between the 28th February and the 9th March 2010, and secondly between the 22nd and 27th April 2010. Snow depth was measured with a probe every 5 metres, and a snow tube measurement was taken every 50 metres, from which snow density and SWE was calculated. Meteorological data was recorded through the melt period at varying elevations along the transects.

The relationships between climate, vegetation, topography and snowcover were explored.

Results:

Snow depth is generally lower in clearings than forested areas due to the trapping of wind blown snow by higher vegetation. Snow melted faster in the clearings than the forested areas due to the direct radiation, and at lower elevations due to the higher temperatures. On the shaded side of the valley snow at the lower farming elevations melted almost 2 weeks earlier than on the shaded side (where landuse is used more for logging than farming, especially at higher elevations). Snow density was generally greater in the clearings where wind crusted denser snow and earlier melt occurs. Snow density increases over the melt period as the snow crystals metamorphose over time and with the weight of the overlying snow. Snow Water Equivalent (SWE) was therefore similar in the forest and clearings in the pre-melt period since the greater depths in the forest are compensated for by lower densities than in the clearings. Mid-melt, SWE was greater in the forest despite lower densities than the clearings because of the earlier melt in the clearings resulting in zero snow depths at the lower and mid-elevations clearings, especially on the sunny side of the valley. Despite snow density increasing throughout the melt period, mean SWE decreased in the clearings due to the large decreases in snow depth during melt. In forested areas, SWE increased through the melt period since the smaller decrease in snow depth due to melting was not enough to compensate for the increase in density.

Implications:

Throughout the winter period, higher densities in clearings result in easier mobility across the land than through the less dense snow of the forests. Whilst SWE is similar in forests and clearings through the winter period since differences in depth and density compensate for each other, the difference in vegetation becomes an important factor in the variation of SWE through the melt period. Forested areas retain snow for longer periods of time delaying the spring melt, and the increased vegetation height traps blowing snow thus increasing the magnitude of the spring melt locally. This is particularly noticeable on south facing slopes which receive more direct radiation causing exposed snow in the clearings to melt earlier and at a greater rate. Earlier melt of snow in clearings is important for farming since it allows a longer growing season, but the surrounding forests are key in maintaining soil moisture and fresh water throughout the spring after the snow has melted from the clearings. Future increases in temperature will result in earlier snow melt, thus the delayed melt in forested areas will become even more important for water supply and soil moisture levels, and a possible reduction in snow precipitation as a result of increased temperatures will increase the importance of forested areas in trapping the reduced volume blowing snow.

Account Owner

School of Geosciences

University of Edinburgh

Drummond Street

Edinburgh

Project Collaborators