Holocene Climate Dynamics, Biogeochemical Cycles and Ecosystem Variability in the Eastern Mediterranean Sea

Abstract

To understand the processes leading to the formation of Holocene sapropel S1 in the Eastern Mediterranean Sea, we integrated results from regional ocean-biogeochemical general circulation model experiments with biogeochemical and micropaleontological proxy records. Sapropel S1 formed during the Holocene insolation maximum, when strong Aegean north winds (Etesian) caused enhanced downwelling and mixing of warm surface waters in the Cretan and western Levantine seas accounting for the complex sea-surface temperature pattern derived from planktonic foraminiferal transfer functions. Our results support a scenario where sufficient organic matter for sapropel formation is buried under oligotrophic conditions in an anoxic water column refuting the ``high-productivity'' hypothesis. We reconstructed a synchronous shift in the state of deep-sea benthic ecosystems, documenting a rapid expansion of dysoxic to anoxic conditions with onset of S1 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.