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It is true that the model resolves only the large-scale circulation, but large-scale thermohaline overturning is responsible for over 80% of the heat transport in the North Atlantic. Johnson's basic premise that Mediterranean Outflow Water (MOW) upwells in high latitudes (near the Wyvilie-Thomson Ridge) to enter the Faroe-Shetland Channel and eventually the Norwegian Sea is neither supported by a recent hydrographic data analysis that specifically looked at this question {McCartney and Mauritzen, 1998) nor by high- resolution circulation model results (A. Coward, pers. commun., 1998; also see Web site http://www.soc.soton.ac.uk/JRD/OCCAM/POSTERS/canigo_posterl .pdf).

In recent research, M. S. McCartney and C. Mauritzen (pers. commun., 1998) show that there is no rise of water from the depths of the Rockall Trough into the Faroe-Shetland Channel, and that the water entering the Norwegian Sea through that channel is derived from the North Atlantic Current. They find that the northward flow of the eastern boundary undercurrent of MOW fades in intensity through the Bay of Biscay and does not penetrate past Porcupine Bank into the Rockall Trough. Particle trajectories from the OCCAM model (1/4 degree resolution in latitude and longitude) are consistent with this analysis. Only one of the more than 100 MOW particles tracked in the model moved north and upwelled into the Faroe-Shetland Channel along the path advocated by Johnson.