From marine to brine and back – a new box model approach to investigate the external influences on the Messinian salinity crisis

The Messinian Salinity Crisis is an event that not only led to the youngest known salt giant, but also impacted the global ocean salinity due to the mass of ions trapped in the Mediterranean Sea. Understanding its full implications requires comprehensive understanding of the events, and due to limitations in data acquisition, modeling is essential to bridge knowledge gaps.
Our latest box model aims to include those processes and aspects that have been indicated to be the most influential by previous model studies. It is forced by (1) a reconstructed freshwater budget with the option to include a salinity feedback, (2) the depth of the Sstrait of Gibraltar and (3) changes in the sea level of the Atlantic. The circulation in the Mediterranean includes the exchange between the eastern and the western basin across the sill  of Sicily on the horizontal level, as well as vertical exchange between two layers. The shapes of the boxes are determined by the hypsometry of the basin, which allows for realistic drawdown and refilling scenarios. The latter offers the option to test the influence of the Paratethys.
To assess the validity of scenarios, the model output is compared to the volume of the known deposits as well as the cycles recorded in gypsum outcrops. An additional tracer in the model is the Sr isotope signal. 
Our findings highlight the importance of horizontal gradients in explaining gypsum deposits in the western basin, unlike the more uniform distribution of gypsum and halite the model produces in the eastern basin. While the onset of gypsum deposition may not necessarily differ between the basins, our results support the theory that halite precipitation began earlier in the east than in the west. This type of model will not answer all questions, but it might guide us to the new ones.