Mass balance methods on Kongsvegen, Svalbard

On the glacier Kongsvegen (102 km(2)) in northwest Spitsbergen, Svalbard, t raditional mass balance measurements by stake readings and snow surveying h ave been conducted annually since 1987. In addition, repeated global positi oning system (GPS) profiling, shallow core analysis and ground-penetrating radar (GPR) surveying have been applied. The purpose of this paper is to ev aluate the input from the different methods, especially the GPS profiling, using the results from the traditional direct method as a reference. The annual flow rate on Kongsvegen is low (2-3 m a(-1)), and the emergence velocity is almost negligible, Thus the geometry changes of the glacier, i. e. the change in altitude per distance from the head of the glacier, should reflect the change in net balance of the glacier. The mean annual altitude change from the longitudinal, centreline GPS profiles was compared to the direct stake readings and showed a very good agreement. On Kongsvegen the m easured actual ice flux is so low that the mass transfer down-glacier at th e mean equilibrium line altitude is less than 10% of what is needed to main tain steady-state geometry. This is clearly shown in the changing altitude profiles. GPS profiling can be used on large glaciers in remote areas to mo nitor geometry changes, ice flow and net mass balance changes. However, it requires that the centreline profile changes are representative for the are a/altitude intervals, i.e. that the accumulation and ablation pattern is ev enly distributed, For this purpose the GPR surveying quickly gave the snow distribution variability overlong distances. Shallow cores drilled in different altitudes in the accumulation area were analysed to detect radioactive reference layers from the Fallout after the Chernobyl accident in 1986, and showed very good agreement to the direct me asured net balance. Thus older reference horizons from bomb tests in 1962 c ould be used to ex tend the net balance series backwards.