Rune Verpe Engeset

Glacier mass-balance and length variation in Norway

Abstract The importance of glaciers in mainland Norway for runoff is reflected in the extensive glacier measurement record. Mass balance has been measured for 42 glaciers. Length (or front-position) records exist for about 60 glaciers, and nearly half of these are presently measured. The mass-balance and front-position data have been analyzed with respect to spatial and temporal variations. The maritime glaciers with a large annual mass turnover have had a mass surplus between 1962 and 2000. In contrast, the continental glaciers with smaller summer and winter balances had a mass deficit over the same period. Since 2001 all monitored glaciers have had a marked mass deficit. The Norwegian glaciers have all retreated during the 20th century. However, both local and regional variations have been observed. Advances were recorded around 1910, around 1930, in the second half of the 1970s and around 1990. This last advance stopped in most glaciers at the turn of the century.

Analysis of the first jökulhlaup at Blåmannsisen, northern Norway, and implications for future events

Abstract The first known jökulhlaup from the Blåmannsisen ice cap in northern Norway began on 6 September 2001. It lasted 35 hours and emptied the lake Øvre Messingmalmvatn (∼4.0 × 107m3). Before the event, the lake drained steadily via a rock spillway into Sweden. The water from the jökulhlaup drained into the hydropower reservoir Sisovatn, and so was financially beneficial to Norway. Glaciological data show evidence of glacier retreat and thinning during the last four decades. Glacier thickness decreased in the ablation zone, reducing ice-barrier stability. The lake drained at a water level 40 m below that required to equalize the ice overburden pressure. Measurements show an ice-barrier thinning of 3.5 m since the jökulhlaup occurred. Climate scenarios indicate future negative mass balance and further thinning. The lake volume was 82% full 2.5 years after the event, suggesting a probable repeat interval of 3 years. Future jökulhlaups may be triggered at lower water levels and produce lower discharges.

Temporal variability in snow distribution

Abstract Snow-courses data have been collected in order to investigate the temporal variability of snow distribution in two catchments in southern Norway during the 2002 melt season. The profiles represent different elevations, aspects and terrain types. At snow maximum the spatial distribution of snow above the tree line was positively skewed (long tail in the positive direction), whereas the spatial distribution below the tree line followed a more normal distribution. During the snowmelt season the spatial distribution of snow became increasingly skewed. By separating the datasets into two terrain classes, alpine and forest, the snow distribution could be described by a time-variant gamma distribution function, one for each terrain class. The results of the study will be used to formulate a new snow routine in the Swedish rainfall–runoff model HBV, which is used for flood forecasting in Norway.