A mooring array known as the RAPID-MOCHA array, has been deployed at 26°N between the Bahamas and the Canary Islands and has provided continuous measurements of the strength and variability of this circulation since 2004. The AMOC and its component parts are monitored by combining a transatlantic array of moored instruments with submarine-cable based measurements of the Gulf Stream and satellite derived Ekman transport (Fig. 1 and 2).

The time series has recently been extended to October 2012 (Fig. 3) and the results show a downward trend since 2004. From April 2008 to March 2012 the AMOC was an average of 2.7 Sv weaker than in the first four years of observation (95% confidence that the reduction is 0.3 Sv or more). Ekman transport reduced by about 0.2 Sv and the Gulf Stream by 0.5 Sv but most of the change (2.0 Sv) is due to the mid-ocean geostrophic flow. The change of the mid-ocean geostrophic flow represents a strengthening of the subtropical gyre above the thermocline.

The increased southward flow of warm waters is balanced by a decrease in the southward flow of Lower North Atlantic Deep Water below 3000 m. The transport of Lower North Atlantic Deep Water slowed by 7% per year (95% confidence that the rate of slowing is greater than 2.5% per year).

http://moocs.southampton.ac.uk/oceans/2014/02/17/the-rapid-project-monitoring-th...

So the articles on the clearly slowing AMOC will repay close reading.

Oceanographers have put a stethoscope on the coursing circulatory system of the Atlantic Ocean, and they have found a skittish pulse that’s surprisingly strong in the waters east of Greenland—discoveries that should improve climate models.

The powerful currents known as the Atlantic meridional overturning circulation (AMOC) are an engine in Earth’s climate. The AMOC’s shallower limbs—which include the Gulf Stream—move warm water from the tropics northward, warming Western Europe. In the north, the waters cool and sink, forming deeper limbs that transport the cold water back south—and sequester anthropogenic carbon in the process. This overturning is why the AMOC is sometimes called the Atlantic conveyor belt.

Last week, at the American Geophysical Union’s Ocean Sciences meeting here, scientists presented the first data from an array of instruments moored in the subpolar North Atlantic. The observations reveal unexpected eddies and strong variability in the AMOC currents. They also show that the currents east of Greenland contribute the most to the total AMOC flow. Climate models, on the other hand, have emphasized the currents west of Greenland in the Labrador Sea. “We’re showing the shortcomings of climate models,” says Susan Lozier, a physical oceanographer at Duke University in Durham, North Carolina, who leads the $35 million, seven-nation project known as the Overturning in the Subpolar North Atlantic Program (OSNAP).

But the AMOC is slowing. That is clear. See the cold pool off S Greenland.