A regional NEMO 4.0 configuration of the subpolar North Atlantic Polina Verezemskaya a,b,1,* , Sergey Gulev a,b , Bernard Barnier b , Jean-Marc Molines b , Pedro Colombo c , Alexander Gavrikov a , Mikhail Kalinin a a Shirshov Institute of Oceanology of Russian academy of sciences, Moscow, Russia b Institut des Geosciences de l’Environment, University Grenoble-Alpes, Grenoble, France c Climate change research center, University of New South Wales, Sydney, Australia ARTICLE INFO Keywords: North Atlantic subpolar gyre Atlantic meridional overturning circulation NEMO ocean model Local-sigma coordinate ABSTRACT The dynamics of the North Atlantic subpolar gyre (SPG) largely control the Atlantic Meridional Overturning Circulation (AMOC), thus affecting the long-term climate variability of the global ocean. Many key processes in the North Atlantic SPG, such as Gulf Stream detachment, eddy activity, deep convection and overflows, are frequently incorrectly presented or misrepresented in modern ocean general circulation models. Here, we demonstrate a new regional eddy-resolving model of the subpolar North Atlantic based on the NEMO4 config- uration and analyze its ability to adequately represent the dynamics of the subpolar North Atlantic. The model performance is assessed using in situ data (cross-section hydrography, Argo and sea gliders), remote sensing data (satellite sea surface temperature and salinity) and the ANDRO and ARMOR3D products based on optimal interpolation products. In the next step, we analyze the effects of several recent developments in ocean modeling to improve the model solution. The implementation of the self-diffusive momentum advection scheme with additional viscosity allows for the simulation of more realistic Deep Western Boundary Current and Irminger Rings lifecycle characteristics. The surface current feedback parameterization implemented in the forcing function and the modification of the kinetic energy budget in the upper ocean, especially in intensively eddying areas, simulate the behavior predicted by coupled models. While the model is sensitive to the implementation of cool skin–warm layer parameterization, this parameterization does not significantly improve the solution compared to the observational data. Regional implementation of the local-sigma vertical coordinate system in cascading areas allows overflow waters to spread over the ocean bottom more realistically. The remote effect of the implementation of the local-sigma coordinate is traced in the vertical thermohaline structure at the western slopes of the Irminger Sea and Iceland Basin as well as in the Deep Western Boundary Current in the Labrador Sea. Compared to z-partial step setting, local-sigma allows for correct representation of continuous densification of the water in the overturning part of the AMOC and thus North Atlantic Deep Water formation. The potential of the new model configuration for analyzing the subpolar North Atlantic, including convective activity, is discussed. 1. Introduction In recent decades, the subpolar North Atlantic has been the focus of both modeling and experimental oceanographic studies. Processes in the North Atlantic subpolar gyre (SPG), such as eddy activity, overflow and deep convection, largely control the Atlantic Meridional Overturning Circulation (AMOC) (Kuhlbrodt et al., 2007; Wang et al. 2015; Yang et al. 2016; Lozier et al. 2017). The AMOC is a key ocean circulation phenomenon that has profound implications for climate variability at decadal and longer time scales (Mahajan et al. 2011; Caesar et al. 2018; Yan et al. 2018; among others). Existing climate and ocean general circulation models as well as ocean reanalysis systems frequently demonstrate biased representations of the key processes of regional circulation in the subpolar North Atlantic. These processes include (while not limited to) Gulfstream detachment, representation of over- flows and eddy formation (Marzocchi et al. 2015; Chassignet and Marshall 2008; Drews and Greatbatch 2016; Verezemskaya et al. 2021). Thus, the development of new regional configurations of ocean general * Corresponding author. E-mail addresses: verezem@sail.msk.ru, pverezemskaya@uliege.be (P. Verezemskaya). 1 Current affiliation: Department of Astrophysics, Geophysics and Oceanography, FOCUS-MAST research group, University of Liege, Liege, Belgium. Contents lists available at ScienceDirect Ocean Modelling journal homepage: www.elsevier.com/locate/ocemod https://doi.org/10.1016/j.ocemod.2024.102457 Received 9 June 2023; Received in revised form 19 September 2024; Accepted 25 October 2024 Ocean Modelling 194 (2025) 102457 Available online 31 October 2024 1463-5003/© 2024 Elsevier Ltd. All rights are reserved, including those for text and data mining, AI training, and similar technologies.