The North Atlantic Ocean Is in a State of Reduced Overturning. Issue 3 (12th February 2018) - Smeed, D. A.
Abstract: The Atlantic Meridional Overturning Circulation (AMOC) is responsible for a variable and climatically important northward transport of heat. Using data from an array of instruments that span the Atlantic at 26°N, we show that the AMOC has been in a state of reduced overturning since 2008 as compared to 2004–2008. This change of AMOC state is concurrent with other changes in the North Atlantic such as a northward shift and broadening of the Gulf Stream and altered patterns of heat content and sea surface temperature. These changes resemble the response to a declining AMOC predicted by coupled climate models. Concurrent changes in air‐sea fluxes close to the western boundary reveal that the changes in ocean heat transport and sea surface temperature have altered the pattern of ocean‐atmosphere heat exchange over the North Atlantic. These results provide strong observational evidence that the AMOC is a major factor in decadal‐scale variability of North Atlantic climate. Key Points: New data from the RAPID 26°N array show that the AMOC has been in a state of reduced overturning since mid‐2008 Observations of heat content and SSH indicate that the impact of the reduction in the AMOC is similar to that predicted by climate models The results indicate that changes in ocean heat transport have altered ocean‐atmosphere heat exchange over the North Atlantic