Already the Day After Tomorrow?

The THC is a driving mechanism for ocean currents. Cooling and ice formation at high latitudes increase the density [HN4] of surface waters sufficiently to cause them to sink. Several different processes are involved, which collectively are termed “ventilation.” When active, ventilation maintains a persistent supply of dense waters to the deep high-latitude oceans. At low latitudes, in contrast, vertical mixing [HN5] heats the deep water and reduces its density. Together, high-latitude ventilation and low-latitude mixing build up horizontal density differences in the deep ocean, which generate forces. In the North Atlantic, these forces help drive the North Atlantic Deep Water (NADW) [HN6] that supplies a large part of the deep waters of the world ocean.