Shoreline displacements in southern-central Sweden and the evolution of the Baltic Sea since the last maximum glaciation

During late- and post-glacial times the Baltic basin has been periodically isolated from the Atlantic and freshwater and saline conditions have altern ated. This is a consequence of the interactions between the spatially varia ble glacial rebound of the region and the simultaneous eustatic sea-level r ise in the adjacent Atlantic. Observations of the timing of these isolation s and of the location of the barriers therefore provide constraints on the rebound models. High resolution numerical models of rebound of southern Swe den, the Danish straits, and the Baltic have been developed and tested agai nst observations of lake-level change as well as against the observed eleva tions of the Last Baltic Ice Lake shoreline which formed before about 10.3 ka sp. Predictions of sea- and lake-levels are used to test two alternative hypotheses about the ice thickness over Scandinavia and to estimate parame ters that describe the Earth's response. Optimum values for the latter are: lithospheric thickness of 60 +/- 20 km, upper-mantle viscosity of 3.3 x 10 (20) Pa s, and lower-mantle viscosity of 10(22) Pa s. The rapid lake-level fall at the end of the Baltic Ice Lake stags is estimated to be 30 +/- 5 m. The optimum ice model for Scandinavia is one in which the ice thickness ov er southeastern and southern Scandinavia was relatively thin compared with the ice thickness over Sweden and Norway: the ice thickness in the southeas t and south changes slowly with distance inwards of the ice margin whereas over Sweden and Norway the ice thickness profiles are considerably steeper. The earth and ice models have been combined with high-resolution digital t errain data to develop a comprehensive model for the evolution of the Balti c basin since the time the area last became ice free. The reconstructions p redict the occurrence of barriers at certain times which impede free flow b etween the Atlantic and Baltic and confirm that the Baltic lake levels ape controlled by rebound at four localities; Degerfors in the Narke region of southern-central Sweden, the Vanern outlet through the Gota Alv, Oresund, a nd the Darss-Langelands-Store baelts in Denmark.