Late Quaternary Climate Variations Reflected in Baltic Sea Sediments - The Baltic Sea Basin - page 100

5.1 Introduction
The study of recent global climate change commonly involves the reconstruction
of climate variation during the late Quaternary based on adequate proxy variables
(Bond et al. 1997 , 2001 ) . Due to the high sedimentation rate, sediments from the
Baltic Sea provide ideal climate archives for climate and environmental reconstruc-
tions. In this topic, Andrén et al. ( Chap. 4 ) give an overview about the environmental
change for the Baltic area during the last glacial cycle (LGC). The postglacial cli-
mate and environmental change have been intensively studied based on sediment
proxies from the Baltic Basin by Ignatius et al. ( 1981 ) , Winterhalter et al. ( 1981 ) ,
Emelyanov ( 1994 ) , Björck ( 1995 , 2008 ) , Sohlenius et al. ( 1996 ) , Winterhalter
( 2001a ) , Repecka ( 2001 ) , Andrén et al. ( 2001 , 2002 ) , Harff et al. ( 2001a , b ) , Emeis
and Dawson ( 2003 ) , Dippner and Voss ( 2004 ) among others. Based on a multi-proxy
approach, Harff et al. ( 1999 , 2001a ) subdivided the Late Pleistocene to Holocene
sediments from the central Eastern Gotland Basin into physico-stratigraphic facies
zones. Lower parts of the postglacial sediments (facies zones A1-A6) represent
mainly freshwater sediments accumulated in an isolated basin. At about 8,000 cal.
years BP the system changed rapidly to a brackish-marine environment resulting
in the accumulation of sediments with changing intensity of lamination. Harff et al.
( 2001a ) structured the brackish sediments into physico-stratigraphic facies zones
B1-B6 and ascribe a change in lamination intensity to differences in ventilation
of the bottom water during the deposition. Westman and Sohlenius ( 1999 ) and
Sohlenius et al. ( 2001 ) showed, on the basis of diatom analysis and oxygen isotope
measurements, that the changes from homogeneous to laminated layers coincide
with variations in salinity. However, main findings are still the subject of discussion,
and an important scientific question is any coupling of the depositional environment
of the Baltic Basin to global climate driving forces. To contribute to this discussion
an international research team of geoscientists studied sedimentary sequences from
the Baltic Sea during 2004-2006. A main task was to interpret the facies variation as
an environmental signal reflecting climatic change during the late Pleistocene and
Holocene (Project GISEB: GIS for Time/Space Modeling of Sediment Distribution
as a Function of Changing Environment in the Baltic Sea). During an expedition to
the central Baltic in 2005 the German R/V “Poseidon” (Harff 2005 ) sampled Late
Quaternary sediments for detailed studies and the comparison with earlier research
results. Numerical methods have been applied for stratigraphic core zonation, cor-
relation of sediment cores, development of 3D space models for stratigraphic units,
and interpretation and time series analysis of proxy data. Here, we report about
results achieved within the frame of this research project.
5.2 The Area of Investigation and the Geological Development
as a Response to Climate Variability
The Baltic Sea is a semi-enclosed intra-continental sea surrounded by the
landmasses of Scandinavia, northern central Europe, and northeastern Europe.