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

Abstract:

The Arctic surface is undergoing rapid changes due to the gradual warming of the Earth’s atmosphere, including the reduction in sea ice and creation of leads in early Spring, as well as fractured sea ice in late Spring and Summer. These changes are occurring faster than in the rest of the globe. This changing surface can lead to modifications in Arctic meteorology, which can also then spread to lower latitudes. The strong thermal contrast between warm sea water and cold Arctic air/ice is shown to generate convective plumes and secondary circulations that drastically enhance the transport of heat, humidity, and aerosols. Turbulence-resolving large-eddy simulations are used to understand the non-linear interactions of surface temperature and roughness contrasts between ice and water surfaces. Idealized flow setups are first 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. Simulations over remotely sensed sea-ice fields then underscore the role of heterogeneity scale and pattern. The conclusions inform the development of parametrizations for mesoscale and global models, underlining the importance of accounting for a range of unresolved processes and feedbacks that give rise to the non-linear atmosphere-surface coupling.