<P> The dense water masses that sink into the deep basins are formed in quite specific areas of the North Atlantic and the Southern Ocean . In the North Atlantic , seawater at the surface of the ocean is intensely cooled by the wind and low ambient air temperatures . Wind moving over the water also produces a great deal of evaporation , leading to a decrease in temperature , called evaporative cooling related to latent heat . Evaporation removes only water molecules , resulting in an increase in the salinity of the seawater left behind , and thus an increase in the density of the water mass along with the decrease in temperature . In the Norwegian Sea evaporative cooling is predominant , and the sinking water mass , the North Atlantic Deep Water ( NADW ) , fills the basin and spills southwards through crevasses in the submarine sills that connect Greenland , Iceland and Great Britain which are known as the Greenland - Scotland - Ridge . It then flows very slowly into the deep abyssal plains of the Atlantic , always in a southerly direction . Flow from the Arctic Ocean Basin into the Pacific , however , is blocked by the narrow shallows of the Bering Strait . </P>
where are the two major regions where dense water masses are created
North Atlantic Southern Ocean