25th International Meeting on Organic Geochemistry IMOG 2011

P-473
Application of TEX86-paleothermometry in the Baltic Sea:
Validation and temperature reconstruction of the past 1000
years
Jaap Sinninghe Damsté 1 , Karoline Kabel 2 , Florian Adolphi 2 , Marianne Baas 1 , Matthias
Moros 2
1 NIOZ Netherlands Institute for Sea Research, Department of Marine Organic Biogeochemistry, Den Burg,
Netherlands, 2 The Leibniz Institute for Baltic Sea Research, Department of Marine Geology, Warnemünde,
Germany (corresponding author:jaap.damste@nioz.nl)
The Baltic Sea is a brackish, enclosed shelf sea
located in the center of northern Europe. The
surrounding continent is densely populated. The
Baltic Sea is, therefore, strongly influenced by human
impact on the one hand and on the other hand the
health of its ecosystem is important for human welfare
in the Baltic region. Today eutrophication,
cyanobacterial blooms and anoxic bottom water
masses are major problems of the Baltic Sea
environment. To answer the question to which degree
these are caused by human activities sound data
about the functioning of the Baltic system and its
natural elasticity is needed. The BONUS project
INFLOW aims to deliver such data for the past 6000
years using sediment cores and evaluating the data
using a modeling approach. In this context the
reconstruction of surface water temperature, as a
driving factor for primary production, is of major
importance.
Due to the fact that the Baltic is a brackish sea,
common methods for marine temperature
reconstruction like δ 18 O of planktonic foraminifera and
U k‘ 37 of alkenones do not work because the specific
organisms are absent in this brackish setting. We
tested the use of the molecular temperature proxy
TEX86 since it has been successfully applied in both
marine and lacustrine settings [1-3]. The TEX86
temperature proxy is based on temperature-induced
changes in the distribution of membrane lipids of
thaumarchaeota which are found in high abundances
in the Baltic Sea.
To provide a local calibration for the Baltic Sea a set
of surface sediment from 23 locations as well as
sediment trap samples covering several seasonal
cycles and from different stations were analyzed and
compared with instrumental data. The trend in TEX86
values of surface sediments was in line with mean
annual (sub)surface water temperature and these
data were used to construct a local calibration for this
area. Sediment trap data indicate that TEX86-derived
temperatures are predominantly influence by summer
temperature. The local calibration was subsequently
applied on short cores covering the past 1000 years.
Our reconstructions indicate that for the Medieval
Warm Period temperatures were similar to present
day temperatures, whereas a temperature decrease
of 3-4°C can be observed during the Little Ice Age.
Our data indicate that TEX86-paleothermometry
provides useful reconstructions of past climate
development in the Baltic region.
References
[1] Schouten S., Hopmans E.C., Schefuss E. and
Sinninghe Damsté J.S., 2002. Earth Planet. Sci. Lett.
204, 265-274.
[2] Kim J.H, van der Meer J., Schouten S., Helmke P.,
Willmott V., Sangiorgi F., Koç N., Hopmans E.C.,
Sinninghe Damsté J.S., 2010. Geochim. Cosmochim.
Acta 74, 4639-4654.
[3] Powers L.P., Werne J.P., Vanderwoude A.J.,
Sinninghe Damsté J.S., Hopmans E.C. and Schouten
S., 2010. Org. Geochem. 41, 404-413.
Fig. 1. The Baltic Sea area with the locations of the
sites where surface sediments were sampled. Core
sampling and sediment trap deployment was in the
central basin of the Baltic.
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