Holocene Climate Dynamics, Biogeochemical Cycles and Ecosystem Variability in the Eastern Mediterranean Sea - Integrated Analysis of Interglacial Climate Dynamics (INTERDYNAMIC) - page 110

deposition. The recovery of benthic ecosystems during the terminal S1 phase was
controlled by increasingly deeper convection and re-ventilation over a period of
approximately 1,500 years.

Keywords Paleoceanography Paleoclimatology Numerical climate modeling

Biogeochemistry Micropaleontology Stable isotope geochemistry Eastern

Mediterranean Sea Holocene Sapropel S1

1 Introduction

The present Mediterranean Sea has a negative water balance, which drives an anti-
estuarine circulation and provokes oligotrophic conditions in the surface mixed
layer of the Eastern Mediterranean Sea (EMS) Krom et al. ( 2010 ). Atlantic surface
water depleted in nutrients enters the Mediterranean Sea through the Strait of
Gibraltar and is partly compensated by the out ow of Mediterranean intermediate

water that exports nutrients mineralized from sinking organic matter. Today, high
evaporation rates and cooling of surface waters trigger deep winter convection and
initiate the formation of oxygen-rich deep and intermediate water masses in various
sites of the basins.
Since the late Miocene, the periodic deposition of organic matter-rich sediments,
so-called sapropels, documents the repeated interruption of EMS deep-water ven-
tilation. The timing of these events is closely linked to Northern hemisphere
summer insolation maxima and is attributed to phases of enhanced riverine fresh-
water runoff, surface-water warming and increased strati

cation at the base of the

mixed layer ( Sullivan

1999 ). Controversy still exists on the roles of productivity and preservation in
causing elevated organic carbon accumulation in sapropels (

“ stagnation ” hypothesis) (Lourens et al. 1996 ; Cramp and O ´

“ high-productivity ”

hypothesis), and the required nutrient sources (Emeis and Weissert 2009 ).
We combined simulations with a regional ocean circulation model coupled to a
biogeochemical model with a compilation of proxy data to examine the processes
and spatio-temporal environmental changes of sapropel S1 formation during the
early Holocene (from 10.2 thousand years (ka) before present (BP) to 6.4 ka BP)
and to test the existing hypotheses.

2 Materials and Methods

We used the ocean general circulation model MPIOM in a regional con guration

for the Mediterranean (Mikolajewicz 2011 ; Adloff et al. 2011 ) coupled to the
marine biogeochemical model HAMOCC (Grimm 2012 ; Ilyina et al. 2013 ) forced
by atmospheric fluxes from global Earth system model simulations for the 9 ka BP

time slice. A Holocene insolation maximum (HIM) baseline simulation represented