[Paper Review] In situ visualization of tip undercooling and lamellar microstructure evolution of sea ice with manipulated orientation

Tongxin Zhang, Zhijun Wang+3 more|arXiv (Cornell University)|Dec 8, 2020

Arctic and Antarctic ice dynamics66 references4 citations

TL;DR

This study presents the first in situ visualization of tip undercooling and lamellar microstructure evolution in sea ice with controlled, unidirectional ice crystal orientation. Using real-time observation, the authors quantitatively link tip undercooling to growth velocity and salinity via a semi-empirical model, revealing novel phenomena such as doublon tips and dendritic tip direction shifts due to solutal diffusion and anisotropic kinetics.

ABSTRACT

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, we in-situ observed the unidirectional growth of lamellar sea ice with well-manipulated ice crystal orientation and visualized tip undercooling of sea ice. A semi-empirical model was proposed to quantitatively address the variation of tip undercooling with growth velocity and salinity and compared with a very recent analytical model. With the real-time observation, interesting phenomena of doublon tip in cellular ice growth and growth direction shift of ice dendritic tip were discovered for the first time, which are attributed to the complex solutal diffusion and anisotropic interface kinetics in sea ice growth. The quantitative experiment provides a clear micro scenario of sea ice growth, and will promote relevant investigations of sea ice in terms of the theoretical approach to describing the diffusion field around faceted ice dendritic tip.

Motivation & Objective

• To overcome the lack of quantitative growth data in sea ice due to uncontrolled crystalline orientation in prior studies.
• To enable real-time observation of microstructural evolution during unidirectional sea ice growth with controlled crystal orientation.
• To quantify tip undercooling as a function of growth velocity and salinity using a semi-empirical model.
• To investigate the influence of solutal diffusion and anisotropic interface kinetics on ice dendritic tip dynamics.
• To provide a clear microscale scenario of sea ice growth for advancing theoretical models of diffusion fields around faceted dendritic tips.

Proposed method

• Employed a directional solidification setup to achieve unidirectional growth of lamellar sea ice with well-controlled crystal orientation.
• Used in situ optical microscopy to visualize the growth front and microstructure evolution in real time.
• Measured tip undercooling directly from the growth interface using high-resolution imaging and temperature gradient analysis.
• Developed a semi-empirical model to correlate tip undercooling with growth velocity and salinity, validated against a recent analytical model.
• Analyzed the dynamics of ice dendritic tips, focusing on morphological instabilities such as doublon tips and growth direction shifts.
• Integrated observations with theoretical considerations of solutal diffusion and anisotropic interface kinetics to explain observed phenomena.

Experimental results

Research questions

• RQ1 How does tip undercooling vary with growth velocity and salinity in lamellar sea ice with controlled orientation?
• RQ2 What microstructural instabilities, such as doublon tips or tip direction shifts, occur during cellular and dendritic ice growth in sea ice?
• RQ3 How do solutal diffusion and anisotropic interface kinetics influence the dynamics of ice dendritic tips in sea ice?
• RQ4 To what extent can a semi-empirical model accurately describe tip undercooling in sea ice under controlled growth conditions?
• RQ5 What insights do real-time observations of microstructure evolution provide for theoretical modeling of diffusion fields around faceted dendritic tips?

Key findings

• The study observed doublon tips in cellular ice growth for the first time, indicating complex interfacial instabilities during solidification.
• A growth direction shift of ice dendritic tips was visualized in real time, attributed to anisotropic interface kinetics and solutal diffusion effects.
• Tip undercooling was quantitatively linked to growth velocity and salinity using a semi-empirical model, showing good agreement with a recent analytical model.
• The observed microstructural evolution provides direct experimental evidence for the role of solutal diffusion in shaping dendritic ice morphology in sea ice.
• The controlled orientation enabled precise measurement of tip undercooling, resolving a key gap in quantitative sea ice growth studies.
• The findings establish a clear microscale scenario of sea ice growth, supporting future theoretical modeling of diffusion fields near faceted dendritic tips.