Quantitative determination of tip undercooling of faceted sea ice within situexperiments.

Sea ice growth with lamellar microstructure containing brine channels has been extensively investigated. However, the quantitative growth information of sea ice remains lack due to the uncontrolled crystalline orientation in previous investigations. For the first time, wein situobserved the unidirectional growth of lamellar sea ice with well-manipulated ice crystal orientation and visualized tip undercooling of lamellar sea ice. With the real-time observation, interesting phenomena of doublon tip in cellular ice growth and growth direction shift of unidirectionally grown ice tip are discovered for the first time, which are attributed to the complex solutal diffusion and anisotropic interface kinetics in ice growth. The quantitative experiments provide a clear micro scenario of sea ice growth, and are suggested to promote relevant investigations of sea ice.