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    Signal and Noise in the Atlantic Meridional Overturning Circulation at 26°N


    McCarthy, Gerard, Hug, Guillaume, Smeed, David, Morris, Kirsty J. and Moat, Ben (2025) Signal and Noise in the Atlantic Meridional Overturning Circulation at 26°N. Geophysical Research Letters, 52 (7). pp. 1-10. ISSN 0094-8276

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    Abstract

    The Atlantic meridional overturning circulation (AMOC) plays a crucial role in redistributing heat within the climate system. The RAPID mooring array has observed an AMOC weakening of 1.0 [0.4–1.6] Sv per decade from 2004 to 2023, consistent with climate model projections and not consistent with a collapse in the mid‐21st century. Here, we analyze the AMOC change within a signal‐to‐noise framework. We find a strong signal in Lower North Atlantic Deep Water (LNADW) and thermocline transports. By removing the influence of Ekman transport on AMOC and LNADW estimates, we reduce noise by 30% and 22%,respectively. Moreover, we demonstrate that a simple model of LNADW yields a comparable signal‐to‐noiseratio to the full AMOC estimate. Ultimately, we conclude that current AMOC trends are unlikely to reach“unfamiliar” (signal‐to‐noise ratio > 2) or “unknown” (signal‐to‐noise ratio > 3) thresholds until the 2040s and 2060s, respectively.
    Item Type: Article
    Additional Information: We would like to thank Chris Piecuch and an anonymous reviewer for their comments that greatly improved this manuscript. We would like to express great appreciation to all who have been involved in maintaining the RAPID‐MOCHAWBTS array, including collecting data at sea. GM and KM are supported by the A4 Project (Aigéin, Aeráid, agus athrú Atlantaigh), with the support of the Marine Institute, under the Marine Research Programme, funded by the Irish Government Grant PBA/CC/18/01). GM and GH are supported by iCRAG, with the support of Science Foundation Ireland (Grant 13/RC/2092_P2). BM and DS are supported by Natural Environment Research Council Grants NE/Y003551/1 and NE/Y005589/1.
    Keywords: Atlantic meridional overturning circulation; AMOC; RAPID mooring array; Lower North Atlantic Deep Water; LNADW; thermocline transports;
    Academic Unit: Faculty of Social Sciences > Geography
    Faculty of Social Sciences > Research Institutes > Irish Climate Analysis and Research Units, ICARUS
    Item ID: 19913
    Identification Number: 10.1029/2025GL115055
    Depositing User: Gerard McCarthy
    Date Deposited: 28 May 2025 09:35
    Journal or Publication Title: Geophysical Research Letters
    Publisher: Advancing Earth and Space Sciences, AGU
    Refereed: Yes
    Related URLs:
    URI: https://mural.maynoothuniversity.ie/id/eprint/19913
    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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