The ocean conveyor belt [1] is the system of ocean currents – also known as thermohaline circulation [2] – that move water around the Earth and have a great impact on a region’s climate. In the Atlantic, the conveyor moves warm water from south to north, bringing Northern Europe a relatively mild climate. Scientists believe the conveyor is slowing down, possibly due to human-caused climate change, and that could mean harsh winters for some parts of Europe within the next ten years.

Scientists have been periodically monitoring the Atlantic conveyor since 1957, via cruise ships that measure the water’s temperature and salinity at various points in order to calculate the flow of the ocean. The results of the most recent measurements [3] showed that the conveyor has slowed by 30% since 1998. The scientists believe the slowdown is due to global warming [3], which is causing glaciers to melt.

Melting glaciers dump freshwater into the salty ocean, changing the density of the sea and altering the patterns of water circulation. Climate experts have worried that global warming might shut down the Atlantic conveyor, and this latest research, published this week in the journal Nature, presents evidence that their fears might be coming true. (For in-depth commentary and debate from climate scientists, go to RealClimate.org [4].) Some climatologists predict the average annual temperature in Britain, Ireland, and parts of continental Europe could drop by more than 7 degrees Fahrenheit – though it’s also possible that worldwide warming trends could neutralize the cooling.

Image credit: Argonne National Laboratory [5]