Regardless, the research teams typically go on extended trips every 18 months to remove and replace sensors from three or four berths on the east side of the Bahamas. Your British counterparts do the same job on the east side of the ocean and along the Atlantic Ridge.
Other groups have set up moorings in different parts of the Atlantic to better understand how different components work, how closely the system is connected, and whether changes in one part affect everywhere.
Susan Lozier, an oceanographer at the Georgia Institute of Technology, leads an international project called OSNAP that began in 2014. It has anchored cables across the Labrador Sea and from the southeastern edge of Greenland to the coast of Scotland.
The hope of the international research effort was to go to the sources of the deep water subsidence, largely responsible for driving the currents in the Atlantic, to “try to gain a much better understanding of the mechanisms driving change in the AMOC. “Says Lozier.
So far, the surveillance programs have mainly found that Atlantic circulation is more variable than previously thought, she says.
Its strength and speed vary dramatically from month to month, year to year, and region to region. Most of the deep water subsidence in the North Atlantic does not seem to occur in the Labrador Sea, as has long been believed, but in the basins east of Greenland. The limbs flowing north and south work more independently than previously understood. Local wind patterns seem to play a more influential role than expected. And some realizations are just confusing.
It is very likely that the Atlantic circulation has weakened. Studies by Rahmstorf of the Potsdam Institute and others have shown that it is about 15% slower than the mid-20th. Both results are based in part on long-term reconstructions of its behavior using records such as temperatures in the Atlantic and the size of the grains on the seabed that may reflect changes in deep sea currents.
There is also “strong agreement” in the models that if greenhouse gas emissions persist, currents will continue to weaken this century.