Brine and pressure dynamics in growing sea ice: measurements and modelling in the Roland von Glasow air-sea-ice chamber

• Main Author: Thomas, Max
• Format: Thesis
• Language: English
• Published: 2018
• Subjects: Roland; Sea ice
• Online Access: https://ueaeprints.uea.ac.uk/id/eprint/71112/; https://ueaeprints.uea.ac.uk/id/eprint/71112/1/Thesis_to_print_MaxThomas.pdf

I investigate two physical processes in growing sea ice using a new experimental facility, the Roland von Glasow air-sea-ice chamber, which I helped develop. I also write two numerical models to simulate the facility and support the experimental results. The processes investigated are 1) the redistribution of solutes within sea ice by gravity drainage, and 2) the build up and release of pressure within sea ice. Measurements of salt and a tracer during a sea-ice growth experiment are used to evaluate four gravity drainage parameterisations. I have coded these parameterisations in a halo-dynamic model that can predict the evolution of solute concentrations in sea ice. Two parameterisations based on brine convection outperform empirical and enhanced diffusivity schemes. These results 1) confirm that convective parameterisations are a powerful tool for predicting the salinity evolution of sea ice, 2) show that these tools can be extended to any solute, and 3) add a novel line of evidence that gravity drainage is a convective process. Pressure is measured during a suite of sea-ice growth experiments. Pressure build up, of up to 33 kPa, and relaxation are observed during initial sea-ice formation, or when sea ice is warmed. I write a thermal stress model that qualitatively reproduces observations, and aids interpretation of the pressure signals. The pressure build up during initial growth may be caused by a combination of the expansion of water upon freezing and thermal stress, while the build up during warming is caused by thermal stress. The observed signals may have significant consequences for sea-ice gas dynamics, and for setting the stress state of sea ice. The results from this thesis provide a strong foundation for future studies in the Roland von Glasow air-sea-ice chamber, and inform the numerical modelling of sea-ice physics and biogeochemistry.