In-situ comparison of interface instability of basal and edge planes during unidirectional growth of sea ice.

The evolutions of water/ice interface with distinct ice orientations are one of the central problems in sea ice growth. Some misunderstandings prevailed in previous hypothesis on morphological evolution of sea ice, which need the validation with carefully designed experiments. Up to now, there is no in-situ comparison of unidirectional freezing behavior between distinct ice orientations, which makes the previous hypothesis on sea ice growth skeptical about its physical basis. The aim of this paper is to provide an in-situ comparison of unidirectional growth behavior of lamellar sea ice between basal and edge planes. Our experiment is realized by a delicate design of parallel freezing samples with two specified ice orientations in a modeled sea water under an imposed thermal gradient. The planar instability as well as the unidirectional cellular/dendritic growth patterns of water/ice interfaces of basal and edge plane ice are compared. It is found that the instability grows faster for edge plane ice, which is addressed by an incubation time coupled with the surface tension anisotropy. In addition, two types of tilted growth patterns of sea ice after planar instability are observed simultaneously, which are suggested to stem from distinct physical origins and provide a new insight into the tilted growth of cellular/dendritic ice. Collectively, these experimental results are suggested to promote our understanding of morphological evolution of unidirectional growth of sea ice, as well as its diverse relevance to many other areas involving ice growth.