On the Nordic Seas'
role in the Meridional Overturning Circulation
Description of PhD project
WP1 (NERSC)
Broecker and others (Broecker 1991, 1997; Rahmstorf 1997, 2000; Weaver et al. 1999) have put the deep water formation north of the Greenland-Scotland ridge at the heart of the Meridional Overturning Circulation (MOC) as the engine of 'the Great Ocean Conveyor'. The conceptual model of the conveyor is well established and has found many useful applications. What is striking, however, is that there seems to be no conclusive evidence that the Nordic Seas (and the Greenland Sea in particular) is powering the Atlantic MOC. The general circulation model (GCM) simulations of Ganopolski et al. (1998) and Wood et al. (1999) support the concept, while those of Mauritzen and Häkkinen (1999), and Bentsen et al. (2002) find little influence of the variability of convective mixing in the Nordic Seas on the MOC. Dedicated process studies are needed. This will constitute the PhD project. Both Marotzke and Scott (1999), and Spall and Pickart (2001) have done fundamental studies of the MOC and how it relates to deep sinking and mixing. They use full GCMs on idealized computational domains representing the North Atlantic proper (60° × 60° boxes of constant depth). The present PhD project is a logical extension of these studies. A similar process model ocean will be set up to mimic the North Atlantic-Nordic Seas system as the above model domain is extended to include an idealized Greenland-Scotland ridge (e.g., Lohmann and Gerdes 1998) and a 30° × 20° 'Nordic Seas box'. This model system should capture the fundamental dynamics of the Atlantic domain described by the above authors, the equivalent dynamics of the Nordic Seas domain, and through the overflow the dynamics of the coupled system. The project will thus provide an assessment of the fundamental communication between the Nordic Seas and the Atlantic Ocean. A further extension, and also part of the project, will be to add a 'shelf sea box' representing the Barents Sea and thereby include the important exchange between a shelf sea and the deep ocean. The GCM to be used will either be MICOM (Bleck et al. 1992) or MITgcm (Marshall et al. 1997), both established models at NERSC.
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