Thermohaline Circulation and Global Warming

Thermohaline circulation is the term used to describe the ocean's cyclical temperature variations. Global Warming experts measure thermohaline circulation, but the results are sometimes interpreted as supporting Global Warming, while other times it seems to contradict global warming theory.

From everything2.com:

Thermohaline circulation is a process in the world's oceans involving fluxuations in temperature and salinity. Such variations create massive currents that move huge volumes of seawater around the world every day. Differences in the temperature and salinity of oceanwater have effects on its density, which is what drives these currents.

Colder water that has a higher salt content from the North Atlantic is flushed southward along the eastern coasts of the Americas and south of Africa and Australia, where it turns northward east of Asia and wamer water with lower concentration of salt is pushed along the current back toward the North Atlantic. The freezing ocean water of the North Atlantic is the primary drive behind thermohaline circulation. This is due to the fact that its density is much greater than any other water along the currents. As water is brought up from the south, it chills very quickly and freezes, but the salt is not, making the water that is still in liquid form have a relatively high concentration of salt. The extremely low temperature of the water, combined with the high salt levels, makes this water much more dense. It sinks to ocean floor, and is known as North Atlantic Deep Water (NADW). As it flows southward, it encounters Antarctic Bottom Water (AABW) which is similarly quite cold and high in salinity, making the current even stronger as it turns eastward. Once it reaches the Pacific Ocean, it has warmed considerably, and has risen closer to the surface as a result. Here a second current is generated, travelling westward along the same path, except north of the coldwater current, hugging the coasts.

...and finally...

Throughout history, the direction and strength of thermohaline circulation has changed. The concern today is that with the increased warming trend going on that has been accelerated by the various industrial efforts of humans, the process of thermohaline circulation may again change drastically. The most obvious way in which this may occur is through the increased melting at the poles. The release of fresh water into the North Atlantic may lead to a desalinization point that could cause the density of the North Atlantic Deep Water to lower, and eventually might slow the deep water formation there. This will slow the currents of cold, dense water flowing southward, and also may slow the northward surface currents of warm water that contribute to the moderate climate enjoyed by eastern Canada, the eastern United States, Great Britian, and western Europe. Wind-driven ocean currents undoubtedly also help contribute to this, but without the effects of thermohaline circulation, change would likely be drastic and irreversible. Some reasearch even indicates that given the recent trends, there is a 70% likelihood that a slowing or even a shutdown of thermohaline circulation will occur between now and 2205.


I tire of reading headlines like "in spite of inactive hurricane seasons, experts still claim we are in an active hurricane season". I tire of the media hype. I tire of the apparent 'scientific consensus'. It seems there's not much consensus when it comes to global warming (and definitely not in the interpretation of thermohaline circulation data and its impacts on global warming).