On Postglacial Sea Level

Abstract

Summary An exact method is presented for calculating the changes in sea level that occur when ice and water masses are rearranged on the surface of elastic and viscoelastic non-rotating Earth models. The method is used to calculate the instantaneous elastic and delayed vi scoelastic sea level changes following the partial melting of late Quaternary ice sheets. We find that there can be large errors in the usual assumption that changes in sea level are uniform over the ocean basins. If a quantity of ice equivalent to a uniform 100-m rise in sea level melts from the Laurentide and Fennoscandian ice sheets, then in the South Pacific the instantaneous rise in sea level can be as large as 120m. In the North Atlantic the instantaneous rise is always less than 100 m. There is a zone in the North Atlantic with almost no sea level change and near Greenland and Norway the sea level falls, rather than rises, by over 100 m. One thousand years after the melting a forebulge migrating towards the ice loads causes water to flow from the South Pacific into the North Pacific suggesting that raised beaches should occur in the South Pacific. The gravitational attraction of an ice mass upon a nearby ocean tends to hold sea level high in the vicinity of the ice. This extra load near the ice may have a significant influence on postglacial isostatic adjustment.