NADW

North Atlantic Deep Water (NADW) is a deep water mass that forms in the high-latitude North Atlantic and is a major component of the global thermohaline circulation. It represents the cold, relatively saline water produced when surface conditions in the subpolar North Atlantic lead to dense water that sinks to depth.

Formation and characteristics: NADW forms primarily through winter cooling and brine rejection during sea-ice formation in regions such as the Greenland, Iceland, and Labrador Seas. The resulting dense water sinks and becomes a defining part of the North Atlantic’s deep layer. NADW is characterized by low temperatures and high salinity compared with surrounding waters, giving it a density that drives its descent and persistence at depths of about 1500 to 2500 meters.

Circulation and global role: After formation, NADW flows southward along the western boundary of the North Atlantic and disperses into the Atlantic’s deep interior. It contributes to the lower limb of the Atlantic Meridional Overturning Circulation (AMOC) and continues into the Indian and Pacific Oceans after crossing the Southern Ocean, where it mixes with other deep and bottom waters. Through these pathways, NADW helps set the structure and ventilation of the global deep ocean.

Significance and variability: NADW is a key driver of oceanic density-driven circulation and plays a central role in climate by transporting heat, carbon, and nutrients. Formation rates are sensitive to freshwater input, wind patterns, and sea-ice dynamics, and climate change is expected to influence NADW production, with potential consequences for the AMOC and regional climate.