The behaviour of the Earth's continental crust and mantle may be modelled as a buoyant floating plate on a viscous liquid, and the variations of load imposed by an ice sheet may be modelled as a time-dependent force. In recent work it has been shown that the mathematical solution of this problem can be subdivided into a propagating far-field forebulge term and a non-propagating near-field term. The latter often dominates and can be approximated satisfactorily by a generalized Gaussian function. Here we fit empirical data from the Main Postglacial Shoreline of northern Britain to a Gaussian trend surface. We show that the fit is significantly better than that of a polynomial trend surface previously published, and that the method has the potential to predict the likely sea surface level offshore at the zero isobase for the shoreline.