The geodetic glacier mass balance of Jan Mayen for the period 1949 to 2008

The volcanic island Jan Mayen covers an area of 377 km2 and it is located at N 71°02’, W 8°12’. Twenty glaciers covering an area of ~111 km2 are protruding the 2277 m high Beerenberg crater. Ground penetrating radar survey on two of the glaciers imply that the glaciers are thin (<100 m). They consist mainly of cold ice except in the lowest parts of the glaciers where only a thin cold layer covers temperate ice. The glacier mass balance has not been monitored before, except for Sørbreen glacier (area: ~15 km2), where the direct glaciological mass balance was measured in 1972 to 1974, and 1976 to 1977. The island Jan Mayen was mapped by the Norwegian Polar Institute using photogrammetry on oblique aerial photographs recorded in 1949. This dataset is now combined with a digital terrain model derived from the 2008 SPOT 5 stereoscopic survey of Polar Ice: reference images and topographies (SPIRIT) by CNES. Preliminary results show that the geodetic mass balance for 1949 to 2008 is 6.3±11 m w.e. The uncertainty in the elevation difference for the two data sets is estimated for the surrounding rocks, and this value is assumed to be representative for the glacier surface. The uncertainty is determined as follows; the elevation grids for the surrounding rocks are subtracted and the scales of spatial correlation are determined for this differential data set. Finally the standard deviation for the spatially averaged elevation differences is calculated. The results show that no statistically significant glacier ice volume change in respect to the determined uncertainty for this data set has occurred in this 59 year period.