A consistent map of the postglacial uplift of Fennoscandia

Abstract

ABSTRACTA consistent map of the recent postglacial rebound of Fennoscandia is constructed on the basis of sea‐level records, lake‐level records and repeated high‐precision levellings.The uplift rates calculated from the sea‐level series form a consistent framework of the map. The sea‐level stations used are 56 reliable stations in the Baltic Sea and adjacent waters with series spanning 60 years or more, many of them about 100 years. Using a reference station in the Baltic Sea and another one outside the Baltic, all results are reduced to a common time span, the 100‐year‐period 1892–1991, in order to eliminate oceanographic changes. Inland, uplift differences are obtained from the repeated national levellings and, in four of the large lakes, from long water level series in pairs. The levellings, however, yield less accurate land uplift values than the sea‐level and lake‐level data.The resultant map shows a fairly smooth phenomenon, with a maximum apparent uplift in the Gulf of Bothnia of 9.0 mm yr‐1. The standard error is typically 0.2 mm yr‐I close to the sea level stations, larger inland.Finally the pattern of the present uplift as determined here is observed to be very similar to that of the past uplift as determined from ancient shore‐lines of the Litorina Sea. However, the ratio between the past uplift and the present uplift rate tends to increase somewhat towards the uplift centre. This might reflect a non‐uniform mantle viscosity. Also, the uplift maximum seems to have migrated towards NNE.