The Gulf Stream

The oceans of the world are permanently connected to one another by large systems of tides. These ocean tides are - besides atmospheric circulation - the most important factor in the global temperature offset. They are driven by differences in the temperature and the salt content of the sea water. Cold and water rich in salt sinks, because it has a higher density than warm water with a low salt content. Changes in temperature to the salt content of sea water leads to changes in the ocean tides with unseen consequences.

[Image: "Bundesministerium für Umwelt, Naturschutz und Reaktorsicherheit" (German Federal Ministry for the Protection of Nature and Reactor Safety)]

The Gulf Stream - or more accurately a part of the Gulf Stream, the North Atlantic Stream - transports warm, tropical water from the Gulf of Mexico to North Europe. As a consequence the unusually mild climate of West and North Europe is favoured ("Europe's warm-water heating system"). The approx. 10°C warm, slat-rich surface water from the Gulf of Mexico streams into the North Atlantic. Cold Arctic winds cool it down to approx. 3°C. In winter a part of the sea water freezes, whereby the ice only contains a little salt. The sea water that is not frozen is now cold and contains a high level of salt. Because of this it sinks to a depth of 3000 m to the bottom of the sea in front of Greenland and Iceland and streams back towards the south as cold water at great depth. The more water there is at these depths, the more salt-rich water is pushed to the surface in the north. Can the Gulf Stream come to a standstill? Due to the earth warming up, the global circulation of water increases in the air. More water evaporates in the tropics that rains in northern latitudes. In addition, due to the earth warming up, more Arctic ice in and around Greenland melts and less sea water freezes in winter.

These factors have the affect that an increasing volume of fresh water streams into the North Atlantic. The surface water from the south becomes diluted and soon is not cold or salty enough to sink into the depths. Which means that no more warm surface water flows. The North Atlantic stream comes to a standstill and it becomes clearly colder in Europe.

Other than in the film "The Day After Tomorrow" (see Basic Course 4) an ice-age will not occur as a result according to researchers. In addition a shift in the ocean tides is not expected to occur in the next few decades. Most climate researchers see this danger taking place in the second half of the 21st Century.

[Author: Dipl.Biol. Marietta Enss, Edited by: Ragnar Müller]

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