Shockwaves have been sent through the climate science community today as a new article published in the December 1 issue of the journal Nature is reporting that the transport of water across the Atlantic Ocean towards Europe has decreased by 30 percent. This shutdown of the ocean's circulation is thought to be caused by a build-up of fresh ocean water at high latitudes caused by rapidly melting ice packs. Increased input of fresh water from the melting of ice and increased precipitation at the poles are thought to be strongly linked to global warming. The implications of these findings are huge and could effect the climate across the globe. A shutdown of the North Atlantic's circulation is thought to be the cause of the last ice age 12,000 years ago during a period known as the Younger Dryas.
The Gulf Stream provides incredible amounts of energy to warm Europe. Remembering that the 'warm' Mediterranean climate is located at the same latitude as New England will give you an idea of how substantial this warming is.
A slowdown in the warm water transport should theoretically lead to cooling of Europe. Such a cooling has yet to be observed, however, the dramatic warming trend observed during the 1990s has stopped. This has led researchers to believe that the cooling trend forced by the slowdown of the ocean currents may simply be cancelling the effects of greenhouse warming, while the rest of the world continues to warm. A decrease in warm water transport across the Atlantic would also leave considerably more warm water in the western Atlantic to fuel increased hurricane activity. Instead of warm water traveling across the Atlantic, the Gulf Stream was found to be recirculating warm water back into its own current off the US coast.
It is still not clear whether or not this is a long term trend or just an anomaly that will disappear. Some climate models have predicted that such a circulation shutdown would take place at the end of this century, but none forecasted a change like this so early. North Atlantic Deep Water (NADW) production north of Europe seems to have slowed significantly. NADW is a significant player in the world wide ocean circulation system and it can be found clear across the globe. The elimination of NADW would likely completely alter the global circulation patterns. In the past the elimination of NADW has been directly linked to ice ages.
Hollywood has taken this long postulated change and used it for the basis of the movie The Day After Tomorrow. However, climate changes are almost always gradual and no catastrophic consequences like those in the movie are forecast. In fact, the movie went as far as to incorrectly diagram the direction of oceanic flow. With that said, nobody knows the true consequences of these findings. One thing that can be certain is that substantial attention will now be diverted to these sensational findings and their dramatic implications for the world in which we live.
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