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 153

revealed not only the natural history of that area but also the change of the socio-
economic environment in reaction to the coastal retreat. In this chapter an extreme
sea level scenario for 2100 AD as a future projection is given for the Wismar Bight.

7.3 Regional Transgression/Regression Model

Within the Baltic Sea area, the interaction of crustal subsidence and uplift (glacio-
isostatic adjustment) and climatically driven eustatic sea level changes can be
studied in an exceptional manner.
For any time point t T the elevation of an area can be expressed by a digital

elevation model DEM t or geographic surface terrain model (Harff et al. 2005 ) cov-
ering as a grid an area of investigation R .TheDEM 0 is the “recent” digital elevation
model ( t

∈

= 0) for the area under investigation.

RSL t ,

if t < 0

DEM t = DEM 0 −

0 .

(1)

EC t + GIA t ,f t ≥

We can explore the surface terrain model DEM t in two different ways: for the
geological past ( t < 0) and for future projections. For t < 0 time is measured in
conventional radiocarbon years. t

0 stands for the reference year 1950 AD. For the
time ( t > 0) we apply the annual (calendar) scale. rsl t ( r )

=

∈ RSL t marks a relative sea

level curve at a location r R .RSL t has to be determined by spatial interpolation

of data from shoreline displacement curves (relative sea level data, rsl) to a grid
covering the area of investigation.
The relative sea level change RSL consists of two components: RSL

∈

EC+GIA.
Here, EC marks the eustatic component and GIA (glacial isostatic adjustment)
stands for the vertical deformation of the earth's crust. EC is controlled mainly by
the change of the palaeoatmospheric temperature which affects the volume of the
oceanic water body not only by thermal expansion but also by melt water inflow
from the decaying continental ice shields. GIA expresses the vertical movement of
the earth's crust due to loading and unloading caused by accumulation and melt-
ing of inland ice masses. For the Fennoscandian Shield this process is described
regarding the last glaciations by Lambeck et al. ( 1998a , b ) , Amatov et al. ( Chap. 3 )
in this topic, and more generally by Peltier ( 2007 ) . Also the gravitational influence
on the sea level change caused by compensational mass flow below uplifting crust
should be mentioned (Ekman 2009 ) . As a function of time t

=

∈

T ,ec t is regarded

constant for the whole area of investigation ( ∀ r ∈ R ). The isostatic component

gia t ( r ) RSL t at a location r is expressed

for each time step t by the difference between the value of the relative sea level curve
and the corresponding eustatic value.

∈ GIA t of a relative sea level curve rsl t ( r ) ∈

gia t ( r ) = rsl t ( r ) − ec t , r ∈ R , t ∈ T (2)