The Use of the Rammsonde as an Instrument for Determining the Density of Firn

Abstract

Abstract It has been found that in the cold firn of the Greenland Ice Sheet a direct relationship exists between the specific gravity of a layer and its “resistance to penetration” as measured with a Rammsonde. Corrections which should be applied to the measured “resistance” to allow for the frictional resistance of the walls of the hole on the Rammsonde tube are discussed. In certain circumstances these corrections can be estimated with reasonable accuracy for tube lengths up to three metres. The statistical method of obtaining the relationships between “resistance” and specific gravity is briefly outlined, and the effect of the size of the snow grains is also considered. It is shown that under these particular conditions it is possible, from measurements of “resistance”, to estimate the specific gravity of a firn layer with a standard error of 0.04, when the specific gravity of the sample is in the range 0.3 to 0.57.