Using aerial photography to study glacier changes in Norway

The Norwegian Water Resources and Energy Administration has photographed glacial areas in Norway for several decades. Detailed maps or digital terrain models have been made for selected glaciers from vertical aerial photographs. Multiple models of seven glaciers have been used here to calculate glacier volume change during the time between mappings using the geodetic method. Analyses and results are presented and compared with traditional mass-balance measurements. We estimated uncertainties of +/-1.3-2.7 m w.e. for the geodetic method, and 13-3.5 m w.e. for the traditional method. The discrepancies between the methods varied between 0.4 and 4.7 m w.e. All glaciers decreased in volume from the 1960s/70s to the 1990s, except Hardangerjokulcn. This glacier experienced a significant increase in volume: the geodetic and traditional methods showed net balance values of +6.8 m and +9.4 m w.e., respectively. Trollbergdalsbreen had the largest total volume loss: the geodetic and traditional methods showed net balance values of -12.3 and -16.8 m w.e.