In DepthOceanography

New scrutiny for a slowing Atlantic conveyor

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Science  13 May 2016:
Vol. 352, Issue 6287, pp. 751-752
DOI: 10.1126/science.352.6287.751

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Summary

Scientists are retrieving data from the largest effort yet to monitor the Atlantic conveyor belt, a set of powerful ocean currents with far-reaching effects on the global climate that has mysteriously slowed over the past decade. Five research cruises this spring and summer will fetch data from the 53 moorings in an array called Overturning in the Subpolar North Atlantic Program (OSNAP), which stretches from Labrador to Greenland to Scotland. The array's measurements of temperature, salinity, and current velocity will be key to understanding the Atlantic Meridional Overturning Circulation (AMOC), and how it is affected by climate change. The AMOC currents include the Gulf Stream, which brings shallow warm waters north, nourishing fisheries and warming northwest Europe. The warm waters give up their heat in the bitterly cold regions monitored by OSNAP, become denser, and sink, forming ocean-bottom currents that return southward, hugging the perimeter of the ocean basins. Models suggest that climate change should weaken the AMOC as warmer Arctic temperatures, combined with buoyant freshwater from Greenland's melting ice cap, impede the formation of deep currents. But so far, limited ocean measurements show the AMOC to be far more capricious than the models have been able to capture.