Best possible estimation of mass balance combining glaciological and geodetic methods

Variance analysis of the long time series of mass balances recorded on Glacier de Sarennes (45 degrees 07'N, 6 degrees 07'E) France, since 1949 shows that the variability can be separated linearly in two spatial and temporal terms. Annual balances deviate from their mean values over the period of record by an annual amount that is uniform over the glacier. Annual balances at each stake are therefore highly correlated, and sampling at a single site would be acceptable to record the annual deviation. A result of the linear character of the variance is the possibility of obtaining a systematic error-free estimate of the annual glacier-total budget by combining the mean annual balance obtained from photogrammetry and the annual deviation obtained from the variance analysis, rather than using the traditional area integration of balances at each stake.