79JANUARY 2004AMERICAN METEOROLOGICAL SOCIETY |
T he idea that the southern winds might be impor-tant to the rate of the deep water formation inthe North Atlantic was first put forward by Toggweiler and Samuels (1995). They analyzed the results of a global circulation model (GCM) and showed that the rate of North Atlantic Deep Water (NADW) format...
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| Language: | English |
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| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.689.9621 http://doronnof.net/files/91.pdf |
| Summary: | T he idea that the southern winds might be impor-tant to the rate of the deep water formation inthe North Atlantic was first put forward by Toggweiler and Samuels (1995). They analyzed the results of a global circulation model (GCM) and showed that the rate of North Atlantic Deep Water (NADW) formation increased when the strength of the southern winds was increased. Since a zonal in-tegration of the geostrophic pressure associated with the interior (i.e., the domain below the top Ekman layer and above bottom topography) over the South-ern Ocean vanishes, and since there can be no local transformation of Ekman water to deep water, they concluded that the transformation must take place in the North Atlantic via the NADW. In this scenario, the Ekman flux in the Southern Ocean must some-how find its way to the Northern Hemisphere where, through cooling, it sinks to the bottom. We shall show here that, although the mass flux of water crossing the equator is indeed equal to the Ekman flux in the Southern Ocean, the crossing waters do not originate in the southern Ekman layer but rather in the south-ern Sverdrup interior. Background. The idea of Ekman to deep water conver-sion in the northern ocean did not go unchallenged and, using numerical integrations, England and Rahmstorf (1999) argue that most of the Ekman–deep water conversion takes place in the South Atlantic and not the North Atlantic. This has some similarity to the idea presented earlier by Döös and Webb (1994) that the Ekman to deep water conversion takes place in stages rather than one single step (such as the NADW formation). Related attempts to examine the role of the continuous zonal pressure gradient in the open Southern Ocean (or its absence) that should be men-tioned here are those of McDermott (1996), Tsujino and Suginohara (1999), and Klinger et al. (2002). We shall argue that the question of what happens to the |
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