The A. aims to determine the effective sample size of 2 glaciers by analysis of the spatial correlation between point mass balance measurements. Correlograms from multiple time series of point mass balance, measured on White Glacier (Axel Heiberg
Island, Canada) and Abramov Glacier (Alai Range, Kirgizia), show that the correlation decreases with the difference in elevation between the points. A principal component analysis confirms that the effective sample size is very small.