18 Sep 2023
 | 18 Sep 2023
Status: this preprint is currently under review for the journal CP.

Multi-annual variability of a new proxy-constrained modeled AMOC from 1450–1780 CE

Eric Samakinwa, Christoph C. Raible, Ralf Hand, Andrew R. Friedman, and Stefan Brönnimann

Abstract. The ongoing discussion about the Atlantic Meridional Overturning Circulation (AMOC) slowdown over the 21st century requires an understanding of preindustrial AMOC variability. Here, we present a new AMOC reconstruction during the Little Ice Age from 1450–1780 CE, generated with a novel nudging technique. The technique uses a 10-member ensemble of ocean-model simulations nudged to proxy-reconstructed sea surface temperature. The new reconstruction improves existing knowledge of the AMOC variability and underlying processes, showing that the AMOC weak phases under stable atmospheric CO2 conditions are mainly driven by a 4-to-7-year lagged effect of surface heat flux associated with the North Atlantic Oscillation (NAO). However, the strong phases are a response to instantaneous surface wind stress. Analyses of our AMOC reconstruction reaffirm previous findings about the mechanisms of AMOC variability and its link to the NAO. In addition, we show that processes leading to the phases of weak and strong AMOC are non-symmetric. Overall, the nudging technique enables us to better constrain past AMOC variability.

Eric Samakinwa et al.

Status: open (until 13 Nov 2023)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • CC1: 'Comment on cp-2023-67', Paola Moffa-Sánchez, 29 Sep 2023 reply
  • RC1: 'Comment on cp-2023-67', Paola Moffa-Sánchez, 02 Oct 2023 reply

Eric Samakinwa et al.

Eric Samakinwa et al.


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Short summary
In this study, we nudged a stand-alone ocean model MPI-OM to proxy-reconstructed SST. Based on these model simulations, we introduce new estimates of the AMOC variations during the period 1450–1780 through a 10-member ensemble simulation with a novel nudging technique. Our approach reaffirms the known mechanisms of AMOC variability and also improves existing knowledge of the interplay between the AMOC and the NAO during the AMOC's weak and strong phases.