Coastlines of the Baltic Sea – Zones of Competition Between Geological Processes and a Changing Climate: Examples from the Southern Baltic - The Baltic Sea Basin - page 157

postglacial sea level rise was decelerated, and 3000 years BP standing for the warm
period of the Roman Climate Optimum (RCO). For each of these time slots the sea
level values have been picked from the curves cited by Rosentau et al. ( 2007 ) and
interpolated to grids RSL t , t . These grids are displayed as

isoline maps at the left panel in Fig. 7.5 and show clearly the deceleration in relative
sea level change since the Littorina Transgression onset. Within the maps the zero-
isoline (hinge line) marks the transition between falling sea level in the centre of
the Fennoscandian Shield and rising sea level in its circumjacent belt. According
to Eq. ( 1 ) palaeogeographic scenarios have been generated for the three time slots
of 7700, 5000, and 3000 years BP. These scenarios are given at the right panel in
Fig. 7.5 .

∈ { 7700, 5000, 3000 }

7.5 Vertical Displacement of the Earth's Crust

Rosentau et al. ( 2007 ) have published an isobase map as a compilation of tide
gauge measurements (rsl curves) in the area of the Baltic Sea, combined with
data from Ekman ( 1996 ) for the central Baltic and new sea level data from the
Kattegat to the Gulf of Gdansk provided by R. Dietrich and A. Richter from
the Technical University Dresden for the western Baltic Sea area. So, the result-
ing map of Rosentau et al. ( 2007 ) is an update of the one published by Ekman
( 1996 ) for the area south of 57.5 ◦ N. As shown in Eq. ( 1 ) the relative sea level
change consists of the glacio-isostatic component and the eustatic (climatically
driven) one. The eustatic component can be regarded constant for the western
Baltic Sea during the last century (Hupfer et al. 2003 ) . Therefore, one can sep-
arate quantitatively the isostatic field by subtracting a constant from the field
displayed by Rosentau et al. ( 2007 ) . Hupfer et al. ( 2003 ) and Ekman ( 2009 ) in
his complete treatment of the eustatic sea level rise in the Baltic Sea during the
last centuries suggested 1.0 mm/year eustatic sea level rise for the western Baltic
Sea during the twentieth century. Based on this assumption we subtracted this
value from the data mapped by Rosentau et al. ( 2007 ) and received a map of
vertical crustal movement (Fig. 7.6 ) . The uplifting Fennoscandian Shield caused
by unloading of Scandinavia due to the melted Weichselian ice sheet is clearly
marked by its centre at the Gulf of Bothnia. The hinge line between the rising
Fennoscandian Shield and its subsiding belt follows at the southern Baltic the
coastline.
In order to get a map in a higher resolution for the southern area we have cor-
rected the gauge data in the southern Baltic by subtracting the eustatic component
and re-interpolated these data to a grid covering the western Baltic Sea. The corre-
sponding contour map is displayed in Fig. 7.7 . It is eye catching that the hinge line
which strikes almost coast-parallel WSW in the eastern part of the area bends NW
south of Rügen Island and forms a step south of the Danish Islands. This pattern is
mirroring the generally NW striking tectonic elements close to the SW border of the
Eastern European Platform (Krauß 1994 ) .