A Sea‐Ice‐Enhanced KPP Parameterization: Impacts on AMOC Simulation and Physical Pathways

Abstract This study presents a sea‐ice‐enhanced K‐profile parameterization to improve simulations of the Atlantic Meridional Overturning Circulation (AMOC) in ocean–sea ice coupled models. The modified KPP dynamically scales the background vertical diffusivity with local sea‐ice fraction, representing the insulating and turbulence‐suppressing effects of sea ice on upper‐ocean mixing. Sensitivity experiments forced by the JRA55‐do (1958–2018) data set show that the proposed schemes strengthen deep‐water formation in the subpolar and Nordic Seas, leading to a more realistic AMOC representation. In addition to AMOC strengthening, the modified scheme produces consistent upper‐ocean salinity increases under sea‐ice conditions, which enhance density and support deep convection. The enhanced AMOC arises through two main physical pathways: (a) intensified deep‐water formation in the Labrador Sea, strengthening the southward branch of the overturning circulation, and (b) increased transport of denser waters to the Nordic Seas, which uplifts isopycnal surfaces across the Greenland–Iceland–Scotland Ridge and promotes the Denmark Strait overflow. Together, these processes reinforce the AMOC and improve agreement with observations. This study establishes a physically based framework for incorporating sea‐ice‐controlled vertical mixing and demonstrates how Arctic sea‐ice‐induced density changes can modulate large‐scale overturning circulation and its variability.