TESTS OF GLACIAL REBOUND MODELS FOR FENNOSCANDINAVIA BASED ON INSTRUMENTED SEA-LEVEL AND LAKE-LEVEL RECORDS

Evidence for changing sea levels in northwestern Europe related to gla cial rebound is found in both the geological record of the past millen nia and in the instrumental records of the past two centuries. The lat ter records are of two types: records of sealevel change, primarily fr om the Baltic and the Gulfs of Finland and Bothnia, and records of the tilting of some of the larger lakes in both Finland and Sweden. The s ealevel records are particularly important because of their long durat ion and high quality, their large number and good spatial distribution , and the spatially coherent background noise. The two instrumental da ta types are complementary and provide constraints on the upper-mantle rheology and on the distribution of ice during the late glacial stage . Comparisons of the observed rates of change of the water levels with models for glacial rebound yield earth models with a lithospheric thi ckness of 80-100 km and an upper-mantle viscosity of (4-5) x 10(20) Pa s, effective parameters that are consistent with those obtained from the analysis of the geological evidence for the same region. The mareo graph results support ice-sheet models in which the Late Weichselian i ce thickness over the eastern and southern parts of Fennoscandia is re latively thinner than that for the western region, also consistent wit h the interpretation of the geological evidence for sea-level change. In addition, the instrumental records provide constraints on the eusta tic sea-level change for about the past 100 years. A satisfactory sepa ration of the earth rheology parameters from this rate of change can b e achieved by estimating the latter only from those records for which the predicted isostatic effects are small. A check on these results is possible by using the lake-level records to establish constraints on the earth-model parameters and the sea-level records to constrain also the eustatic change. All approaches lead to an average eustatic sea-l evel rise for the past century of about 1.1 +/- 0.2 mm yr(-1).