Towards an ocean biogeochemical modelling framework for long-term transient simulations with a focus on the Eastern Mediterranean Sea

Sediment archives of the Eastern Mediterranean Sea (EMed) indicate very different physical and biogeochemical conditions during the LGM and the early Holocene than for present day. The ultimate goal of the here presented project is to disentangle the controlling processes of the circulation in the EMed over the last deglacial period by applying a regional ocean model including biogeochemistry covering the entire Mediterranean Sea. This model setup will be driven by downscaled forcing fields from a simulation with the paleo version of Max Planck Institute Earth System Model (pMPI-ESM) spanning from 26 to 0 kaBP.  pMPI-ESM has unique features like automatic bathymetry adjustment due to sea level rise and transient river routing. Despite its coarse model resolution, pMPI-ESM simulations catch the humid period of the early Holocene with corresponding increased Nile river discharge, a relevant driver for the conditions in the EMed. Thus, we are convinced that pMPI-ESM can provide a long-term transient and consistent forcing which is appropriate for our aims.

Here we present first results to evaluate the performance of our regional model driven by the downscaled forcing from pMPI-ESM. Main characteristics of the present day Mediterranean circulation are well captured such as locations of deep water formation, Mediterranean and Black Sea fresh water budgets, and the baroclinic transports through the Strait of Gibraltar.  We test our model framework for different time slices of deglaciation.