| Summary: | This study uses an atmospheric general circulation model to examine the regional and global climate response to the Messinian Salinity Crisis (MSC) roughly 6 Ma. During this time, the tectonic collision of the African and European plates isolated the Mediterranean Sea (MedSea) from the Atlantic Ocean. MedSea level is estimated to have fallen between 1000-2000 m and desiccation may have lasted for 90 kyr. Our results show that the substantial MedSea depression generates planetary-scale atmospheric waves responsible for significant climate effects throughout the Northern Hemisphere. A notable deepening of the Aleutian Low and a significant equator-ward shift in the Atlantic jet stream are evident. Cyclical patterns in Messinian sediments suggest alternating wet and dry climate during the MSC. These cycles have been attributed to variations in the Earth's precession. This is the first study to detail how reduced MedSea level alters orbitally-driven climate change during the Late Miocene. Reduced MedSea level results in wetter conditions to the Northeast, in particular the Alps, consistent with proxy data. This signal is robust under all precession signals and is supported by evidence of greater weathering of the Alps during the MSC. Desiccation and lowered MedSea level results in greater precipitation over the Guinea Coast region of North Africa. Greater runoff from this region is supported by proxy evidence of higher monsoon intensity and enhanced total organic carbon accumulation throughout the Messinian. We couple our model to an online aerosol model to examine the response of dust to varying orbital parameters and to MedSea desiccation. Modeling dust source and transport changes in response to decreased dustiness during precession minimum shows that warmer tropical North Atlantic SSTs, attributed to increased insolation in the absence of dust, enhances evaporation and favors more precipitation over the western tropical North Atlantic. This stresses the importance of allowing dust to respond to climate change ...
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