Patterns of sea ice floes shape ocean turbulence in the marginal ice zone

As Arctic sea ice transitions to a more seasonal regime, the marginal ice zone (MIZ) is emerging as increasingly relevant to the climate system. Within this region, the evolution of turbulent ocean eddies is tightly coupled to the fate of sea ice. Yet, most existing approaches treat sea ice as a continuum, even though in the MIZ it is composed of discrete floes whose sizes overlap those of the eddies. Here, using a coupled model system that explicitly resolves interactions between individual floes and the ocean, we show that the patterns of sea ice cover regulate the energy pathways associated with large-scale turbulence. Variations in the floe size distribution reshape both the generation and damping of ocean eddies, producing more than a twofold difference in kinetic energy between realizations with different floe arrangements. These differences arise as both the sizes and spatial organization of floes imprint on surface forcing, while the resulting turbulence reorganizes the ice into clusters and open-water regions at scales distinct from the floes themselves. Heterogeneity in the sea ice cover, not just its concentration, govern upper-ocean turbulence, underscoring the challenges inherent to the growing implementation of high-resolution Earth-system models.