The parameterisation of Mediterranean–Atlantic water exchange in the Hadley Centre model HadCM3, and its effect on modelled North Atlantic climate

Multiple palaeo-proxy and modelling studies suggest that Mediterranean Outflow Water (MOW) is an important driver of Atlantic Meridional Overturning Circulation (AMOC), particularly during periods of weak overturning. Here, we employ the HadCM3 ocean–atmosphere General Circulation Model (GCM) to inv...

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Bibliographic Details
Published in:Ocean Modelling
Main Authors: Ivanovic, Ruza F., Valdes, Paul J., Flecker, Rachel, Gregoire, Lauren J., Gutjahr, Marcus
Format: Article in Journal/Newspaper
Language:English
Published: Elsevier 2013
Subjects:
North Atlantic
Online Access:https://oceanrep.geomar.de/id/eprint/21232/
https://oceanrep.geomar.de/id/eprint/21232/1/Ivanovic%20OM.pdf
https://doi.org/10.1016/j.ocemod.2012.11.002
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Summary:Multiple palaeo-proxy and modelling studies suggest that Mediterranean Outflow Water (MOW) is an important driver of Atlantic Meridional Overturning Circulation (AMOC), particularly during periods of weak overturning. Here, we employ the HadCM3 ocean–atmosphere General Circulation Model (GCM) to investigate the effect of using different parameterisations of Mediterranean–Atlantic water exchange on global ocean circulation and climate. In HadCM3, simulating flow through the Gibraltar Straits with an ‘open seaway’ rather than a ‘diffusive pipe’ causes a shoaling and strengthening of the MOW plume. This reorganises shallow Atlantic circulation, producing regional surface air temperature anomalies of up to + 11 °C and −7.5 °C. We conclude that when investigating the influence of MOW on modelled ocean circulation and climate, an accurate parameterisation of Mediterranean–Atlantic exchange is important and should match observed fresh water and salinity flux constraints. This probably cannot be achieved through a simple ‘diffusive pipe’ with depth invariant mixing coefficient.

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