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    A 30-year reconstruction of the Atlantic meridional overturning circulation shows no decline

    Worthington, Emma and Moat, Ben I. and Smeed, David A. and Mecking, J. V. and Marsh, Robert and McCarthy, Gerard (2021) A 30-year reconstruction of the Atlantic meridional overturning circulation shows no decline. Ocean Science, 17. pp. 285-299.

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    A decline in Atlantic meridional overturning circulation (AMOC) strength has been observed between 2004 and 2012 by the RAPID-MOCHA-WBTS (RAPID – Meridional Overturning Circulation and Heatflux Array – Western Boundary Time Series, hereafter RAPID array) with this weakened state of the AMOC persisting until 2017. Climate model and paleo-oceanographic research suggests that the AMOC may have been declining for decades or even centuries before this; however direct observations are sparse prior to 2004, giving only “snapshots” of the overturning circulation. Previous studies have used linear models based on upper-layer temperature anomalies to extend AMOC estimates back in time; however these ignore changes in the deep circulation that are beginning to emerge in the observations of AMOC decline. Here we develop a higher-fidelity empirical model of AMOC variability based on RAPID data and associated physically with changes in thickness of the persistent upper, intermediate, and deep water masses at 26∘ N and associated transports. We applied historical hydrographic data to the empirical model to create an AMOC time series extending from 1981 to 2016. Increasing the resolution of the observed AMOC to approximately annual shows multi-annual variability in agreement with RAPID observations and shows that the downturn between 2008 and 2012 was the weakest AMOC since the mid-1980s. However, the time series shows no overall AMOC decline as indicated by other proxies and high-resolution climate models. Our results reinforce that adequately capturing changes to the deep circulation is key to detecting any anthropogenic climate-change-related AMOC decline.

    Item Type: Article
    Additional Information: Ocean Sci., 17, 285–299, 2021 © Author(s) 2021. This work is distributed under the Creative Commons Attribution 4.0 License
    Keywords: 30-year reconstruction; Atlantic meridional overturning circulation; AMOC; climate models; deep circulation;
    Academic Unit: Faculty of Social Sciences > Geography
    Faculty of Social Sciences > Research Institutes > Irish Climate Analysis and Research Units, ICARUS
    Item ID: 14864
    Identification Number:
    Depositing User: Gerard McCarthy
    Date Deposited: 01 Oct 2021 15:27
    Journal or Publication Title: Ocean Science
    Publisher: Copernicus Publications (for the European Geosciences Union)
    Refereed: No
    Use Licence: This item is available under a Creative Commons Attribution Non Commercial Share Alike Licence (CC BY-NC-SA). Details of this licence are available here

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