Thickness, subglacial relief and volume of Svalbard glaciers based on radio echo‐sounding data

Abstract

The authors present the results of repeated analyses of data from radio echo‐sounding surveys of Svalbard glaciers conducted in 1978–79 and using a frequency of 620 MHz. Data from surveys flown in 1974–75 and 1977–80 over Svalbard glaciers are also discussed. It has been established that glaciers with areas of up to 15²km are characterized by maximum ice thicknesses of 200 m and relatively complex subglacial topography. Reticulated glaciers have much greater ice thicknesses; on ice plateaux they reach 585 m (Holtedahlfonna), and on twinned, outlet and valley glaciers 430–540 m or more (e.g., Recherchebreen‐Vestre Torellbreen, Mittag‐Lefflerbreen and Veteranen). Major rises in the subglacial bedrock have been detected in the ice‐divide areas of some twinned glacier systems. Glaciers occupying valleys are characterized by maximum ice thicknesses of 350–400 m (in the accumulation zone) and comparatively flat, even subglacial relief, extending for distances of 5–30 km. These glacier beds lie near or below sea level, down to depths of ‐100 or ‐200 m. In the case of ice caps overlying positive relief forms (e.g., Aasgaardfonna) maximum ice thicknesses vary between 100 and 350 m, while in the case of the Vestfonna, which has a comparatively flat bed, they reach 385 m. In general there are no significant differences in the distribution of ice thicknesses over the areas of reticulated glaciers in Svalbard. Data from radio echo‐sounding and ratios established between ice volume and glacier area allow one to calculate the total ice volume in the glaciers of the archipelago and to determine its distribution over particular glacierized areas. According to our revised figures the total ice volume is about 7,500 km³. Mean thicknesses of glaciers in the area of reticulated glaciers in Svalbard range from 140 m in the south to 170 m in the northeast. In the central area, mainly involving mountain glaciers, mean ice thicknesses are about 70 m. The mean thickness of all Svalbard glaciers is close to 200 m. The problem of radio echo‐sounding of the firn areas on large glaciers still remains unresolved. A possible solution would be to carry out the measurements during the cold period of the year; in general, too, it can be resolved by using equipment operating at lower frequencies.