Postglacial Relative Sea-Level Changes in the Gulf of Maine, USA : A Challenge for GIA Models

Abstract

Relative sea level (RSL) reconstructions from paleo records are often the most valuable data set in testing and constraining glacial isostatic adjustment (GIA) models. In some regions, the amplitude and rate of the reconstructed RSL changes are large making the data difficult to fit. Arguably, the reconstructed RSL curve from Maine, USA, is the classic example of such a data set with peak values at about 120 m dropping to a low stand of around -40 m within a few kyr. To our knowledge, no GIA model has captured these extreme variations and the record has been somewhat neglected by the GIA community. Here we critically assess and present a revised pre-10 ka RSL data base for this region and combine it with two recent Holocene compilations. To determine if a successful model fit can be found, output based on a parameter set of five ice models and 440, spherically-symmetric, Maxwell Earth viscosity models was compared to the compiled data. Results show that none of the ice models produce a good fit for the large suite of 1D viscosity models considered. Specifically, the modelled timing and rate of RSL fall are generally too early and low, and the RSL low stand from the models is significantly higher than that observed. A model sensitivity analysis suggests that Earth models that can simulate time-dependent viscosity (e.g., those including transient and/or non-linear effects) are required to fit the Maine RSL data set.