The importance of deep, basinwide measurements in optimised Atlantic Meridional Overturning Circulation observing arrays

• Published in: Journal of Geophysical Research: Oceans
• Main Authors: McCarthy, G.D., Menary, M.B., Mecking, J.V., Moat, B.I., Johns, W.E., Andrews, M., Rayner, D., Smeed, D.A.
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2017
• Subjects: North Atlantic
• Online Access: http://nora.nerc.ac.uk/id/eprint/516041/; https://nora.nerc.ac.uk/id/eprint/516041/7/McCarthy_et_al-2017-Journal_of_Geophysical_Research__Oceans.pdf; https://nora.nerc.ac.uk/id/eprint/516041/1/second_revision_mccarthy.pdf; https://doi.org/10.1002/2016JC012200

The Atlantic Meridional Overturning Circulation (AMOC) is a key process in the global redistribution of heat. The AMOC is defined as the maximum of the overturning stream function, which typically occurs near 30°N in the North Atlantic. The RAPID mooring array has provided full-depth, basinwide, continuous estimates of this quantity since 2004. Motivated by both the need to deliver near real-time data and optimization of the array to reduce costs, we consider alternative configurations of the mooring array. Results suggest that the variability observed since 2004 could be reproduced by a single tall mooring on the western boundary and a mooring to 1500 m on the eastern boundary. We consider the potential future evolution of the AMOC in two generations of the Hadley Centre climate models and a suite of additional CMIP5 models. The modeling studies show that deep, basinwide measurements are essential to capture correctly the future decline of the AMOC. We conclude that, while a reduced array could be useful for estimates of the AMOC on subseasonal to decadal time scales as part of a near real-time data delivery system, extreme caution must be applied to avoid the potential misinterpretation or absence of a climate time scale AMOC decline that is a key motivation for the maintenance of these observations.