North Atlantic Deep Water (NADW) is a deep
water mass formed in the North
Atlantic Ocean.
Thermohaline circulation of the world's oceans involves the flow of warm surface waters from the southern hemisphere into the North Atlantic. Water flowing northward becomes modified through evaporation and mixing with other water masses, leading to increased salinity. When this water reaches the North Atlantic it cools and sinks through convection, due to its decreased temperature and increased salinity resulting in increased density. NADW is the outflow of this thick deep layer, which can be detected by its high salinity, high oxygen content, nutrient minima, and
chlorofluorocarbons (CFCs). CFCs are anthropogenic substances that enter the surface of the ocean from gas exchange with the atmosphere. This distinct composition allows its path to be traced as it mixes with
Circumpolar Deep Water (CDW), which in turn fills the deep
Indian Ocean and part of the
South Pacific. NADW and its formation is essential to the
Atlantic Meridional Overturning Circulation (AMOC), which is responsible for transporting large amounts of water, heat, salt, carbon, nutrients and other substances around the globe. In the conveyor belt model of
thermohaline circulation of the world's oceans, the sinking of NADW pulls the waters of the
North Atlantic drift northward; however, this is almost certainly an oversimplification of the actual relationship between NADW formation and the strength of the
Gulf Stream/North Atlantic drift.