| Summary: | The Norwegian Polar Institute measures mass balance on three glaciers, all in the Kongsfjorden area of north-western Spitsbergen, Svalbard. They are: Austre Brøggerbreen (data since 1967, Midtre Lovénbreen (since 1968) and Kongsvegen (since 1987). The first two are among the longest continuous high arctic glacier mass balance time-series. The Norwegian Polar Institute uses the so-called “combined method”, a mixture of the fixed-date and the stratigraphic methods, and comprises sounding of winter snow depth and repeated measurement of heights of an array of 8-10 stakes along the glacier centerline. Winter balance is obtained by snow-depth soundings over much of the glacier, an estimate of the autumn superimposed ice by shallow ice-cores along the longitudinal axis or at least by a measurement at the bottom of snow pits, stake height measurements, and snow density measurements. The work is carried out at the end of the accumulation period, in May. Stake positions are measured using differential GPS every year to monitor long-term velocity and elevation changes, both of which respond to the yearly mass fluctuations. Summer balance is obtained directly by comparing stake heights made in spring to fall stake measurements. The latter work is usually done at the end of the ablation period (in September and sometimes in October). Balance estimates are extrapolated over the entire glacier basin by using the distribution of glacier area per 50-m elevation band (hypsometry) obtained from maps or digital elevation models (DEMs). Net, winter and summer mass balance values are reported each year to MOSJ and as well to the World Glacier Monitoring Service.
|
|---|