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the pre-sapropel well-ventilated conditions (Adloff et al. 2011 ).To assess the sen-
sitivity to increased freshwater input, a set of perturbation experiments was
implemented to modify the baseline simulation. These include: the opening of the
Bosporus, strong increase in Nile and Po runoff, freshening from the in
Atlantic water, and increased precipitation. We implemented an age tracer in the
model to infer the stability and duration of EMS deep-water stagnation caused by
each perturbation (Adloff 2011 ; Grimm 2012 ).
To validate the model results, we compiled proxy data from existing studies and
generated a new multi-proxy dataset. We produced two independent sea-surface
temperature (SST) records using planktonic foraminiferal transfer functions (Adloff
et al. 2011 ) and alkenones. In addition, we estimated ventilation and organic matter
flux using benthic foraminiferal assemblages and stable carbon isotopes (Schmiedl
et al. 2010 ). Finally, using stable nitrogen isotope and organic carbon data, we
evaluated productivity and carbon sequestration (M
bius et al. 2010 ). Monomeric
distribution of amino acids allowed us to estimate the state of organic matter
decomposition expressed in the degradation index (DI) (M
bius et al. 2010 ). For
the quanti
cation of oxygen changes in benthic ecosystems, we applied an OI that
is based on the ratio between high- and low-oxygen benthic foraminiferal indicator
taxa and the benthic foraminiferal diversity (Schmiedl et al. 2010 ).
3 Key Findings
During the HIM, our model simulated an enhanced seasonal cycle with a
homogenous winter cooling of the water column and a summer warming restricted
to the top few meters. The enhanced summer insolation induced a surface warming
with well-de
ned spatial patterns of subsurface warming/cooling in the Cretan and
western Levantine seas. An initial comparison of the simulated SST for the HIM
and a reconstruction based on planktonic foraminiferal transfer functions showed a
poor agreement especially for summer, when the vertical temperature gradient is
steep. The model-proxy agreement improved considerably when the proxy data
were calibrated to the entire modern habitat depth ranges of surface-dwelling
planktonic foraminifers (Fig. 1 ). This implies that planktonic foraminifers in this
case predominantly record an integrated upper ocean signal. The dynamical
explanation for the regional contrasts of subsurface temperatures during the HIM
summers is the wind-driven transport of warm surface waters due to strengthened
northerly Aegean (Etesian) winds, ampli
ed by enhanced vertical mixing. This
leads to subsurface warming in areas of convergence, e.g., in the Cretan and
western Levantine seas, and to subsurface cooling in areas of divergence. Such a
process may be characteristic for time intervals of enhanced summer insolation in
the EMS during the late Neogene and Quaternary (Adloff et al. 2011 ).
The compiled biogeochemical records and benthic foraminiferal successions
across sapropel S1 from various sediment cores suggest that the accumulation of
organic matter in the abyssal parts of the basins occurred under low-productive
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