e intervals of the resultant non-Gaussian distributions were calculated using the bias-corrected and accelerated (BC,) percentile method (Efron and Tibshirani, 1998). Reference Sandwell DT (1987) Biharmonic spline interpolation of GEOS-3 and SEASAT altimeter data. Geophys Res Lett 2:139-142. EFTA_R1_020