Impact of global SST gradients on the Mediterranean runoff changes across the Plio-Pleistocene transition

This work explores the impact of the development of global meridional and zonal sea surfacetemperature (SST) gradients on the Mediterranean runoff variability during the Plio-Pleistocene transition,about 3 Ma. Results show that total annual mean Pliocene Mediterranean runoff is about 40% larger thandu...

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Bibliographic Details
Main Authors: Colleoni, F, Cherchi, A, Masina, S, Brierley, CM
Format: Article in Journal/Newspaper
Language:English
Published: 2015
Subjects:
Mediterranean runoff
Pliocene climate
climate modeling
SST gradient
Plio-Pleistocene transition
North Atlantic
North Atlantic oscillation
Online Access:https://discovery.ucl.ac.uk/id/eprint/1474373/7/Colleoni_et_al-2015-Paleoceanography.pdf
https://discovery.ucl.ac.uk/id/eprint/1474373/
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Summary:This work explores the impact of the development of global meridional and zonal sea surfacetemperature (SST) gradients on the Mediterranean runoff variability during the Plio-Pleistocene transition,about 3 Ma. Results show that total annual mean Pliocene Mediterranean runoff is about 40% larger thanduring the preindustrial period due to more increased extratropical specific humidity. As a consequenceof a weakened and extended Hadley cell, the Pliocene northwest Africa hydrological network producesa discharge 30 times larger than today. Our results support the conclusion that during the Pliocene, theMediterranean water deficit was reduced relative to today due to a larger river discharge. By means ofa stand-alone atmospheric general circulation model, we simulate the separate impact of extratropicaland equatorial SST cooling on the Mediterranean runoff. While cooling the equatorial SST does not implysignificant changes to the Pliocene Mediterranean hydrological budget, the extratropical SST coolingincreases the water deficit due to a decrease in precipitation and runoff. Consequently, river dischargefrom this area reduces to preindustrial levels. The main teleconnections acting upon the Mediterraneanarea today, i.e., the North Atlantic Oscillation during winter and the “monsoon-desert” mechanism duringsummer already have a large influence on the climate of our Pliocene simulations. Finally, our results alsosuggest that in a climate state significantly warmer than today, changes of the Hadley circulation couldpotentially lead to increased water resources in northwest Africa.

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