60° 40° 20°W 0° 
Fig. 3. Location of the sections in Figure 2. The 500 m and 2000 m isobaths are adapted from 
General Bathymetric Chart of the Oceans (GEBCO) numbers 5.04 (1978 edition) and 5.08 (1982 
edition). 
Another issue of interest is why the North Atlantic produces new deep water while the 
North Pacific does not. Many factors have been proposed, such as effects of basin geometry 
and evaporation/precipitation/run-off differences. The North Atlantic also includes two principal 
Mediterranean seas: the Mediterranean Sea and the combined Arctic Ocean, Greenland/ 
Iceland/Norwegian Sea system. The first is an evaporation basin, and it supplies dense salty 
water to the North Atlantic. The high-salinity waters extend north into the second Mediterranean 
region, where they are cooled to near-freezing temperatures and overturn to provide the dense 
overflow waters (for example, see Aagaard, Swift and Carmack, 1984). To the extent that this 
is true, it is the presence of these Mediterranean seas which triggers the present-day ther- 
mohaline circulation and makes NADW the primary ventilator of the deep World Ocean. 
