Precessional drivers of late Miocene Mediterranean sedimentary sequences: African summer monsoon and Atlantic winter storm tracks

Abstract

Cyclic sedimentary patterns in the marine record of the Mediterranean Sea have been consistently correlated with orbitally-driven shifts in climate. Freshwater input driven by the African summer monsoon is thought to be the main control of such hydrological changes, where the runoff signal is transferred from the eastern to the western Mediterranean. The geological record from the Atlantic margin also contains precession-driven dilution cycles that have been correlated with the sedimentary sequences in the western and eastern Mediterranean despite the lack of a direct connection with the basin.  In these regions, Atlantic winter storms have also been invoked to explain the wet phases. In the absence of seasonally-resolved proxy data, climate simulations at high temporal resolution can be used to investigate the drivers of Mediterranean hydrologic changes both on precessional and seasonal timescales. Here, we use the results of 22 ocean-atmosphere-vegetation simulations through an entire late Miocene precession cycle. These show that the African summer monsoon drives the hydrologic budget in the Eastern Mediterranean during precession minima, while the western marginal basins are generally dominated by local net evaporative loss. During precession minima, the western Mediterranean and the Atlantic margin are also influenced by enhanced winter precipitation from the Atlantic storm tracks. We can, therefore, identify two different moisture sources affecting the circum-Mediterranean area, characterized by the same phasing with respect to precession, but with opposite seasonality. This supports the interregional correlation of geological sections in these areas, as we show for the Messinian and speculate for other time periods.

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