Turbulence-Resolving Simulations of Atmosphere-Surface Coupling in the Marginal Ice Zone: The Interacting Effects of Temperature and Roughness Heterogeneity

The Arctic surface is undergoing rapid changes due to the warming of the Earth's atmosphere, including the reduction in perennial sea ice, creation of leads in early spring, and fractured sea ice in late spring and summer. The thermal contrast between warm sea water in leads and adjacent cold Arctic sea ice generates secondary circulations that drastically enhance the transport of heat, humidity, halogens, and aerosols. We propose a nondimensional framework to reduce the parameter space of this complicated turbulent atmospheric boundary layer flow over fractured sea ice. Large-eddy simulations are conducted to understand the non-linear interactions of surface temperature and roughness contrasts between ice and water surfaces. Idealized flow setups are considered where the surface wind is parallel, perpendicular, or oblique to the ice/water interface. The results elucidate the synergistic interactions of surface temperature and roughness in the context of heterogeneous Arctic sea ice, and the critical role of wind angle. The conclusions will inform the development of parametrizations for mesoscale and global models, underlining the importance of accounting for unresolved processes and feedbacks that give rise to the non-linear atmosphere-surface coupling.