An X-ray micro-tomographic study of the pore space, permeability and percolation threshold of young sea ice
The hydraulic permeability of sea ice is an important property that influences the role of sea ice in the environment in many ways. As it is difficult to measure, so far not many observations exist and the quality of deduced empirical relationships between porosity and permeability is unknown. The p...
| Main Authors: | , , |
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| Format: | Text |
| Language: | English |
| Published: |
2020
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| Subjects: | |
| Online Access: | https://doi.org/10.5194/tc-2020-288 https://tc.copernicus.org/preprints/tc-2020-288/ |
| Summary: | The hydraulic permeability of sea ice is an important property that influences the role of sea ice in the environment in many ways. As it is difficult to measure, so far not many observations exist and the quality of deduced empirical relationships between porosity and permeability is unknown. The present work presents a study of the permeability of young sea ice based on the combination of X-ray tomographic imaging and direct numerical simulations. The approach is new for sea ice. It allows to relate the permeability and percolation properties explicitly to characteristic properties of the sea ice pore space, in particular to pore size and connectivity metrics. For the young ice from the present field study we obtain a brine volume of 2.4 ± 0.3 % as threshold for the vertical permeability (transition to impermeable sea ice). We are able to relate this transition to the necking of brine pores at a critical pore throat diameter of ≈ 0.07 mm, being consistent with some limited pore analysis from earlier studies. The obtained critical brine porosity is considerably smaller than the value of 5 % proposed in earlier work and frequently adopted in sea ice model studies and applications. We revise the uncertainties associated with earlier estimates suggesting that the present result is more accurate. We then propose a consistent parametrisation for the permeability of young sea ice that will be useful for modelling. The study highlights the large potential of X-ray tomography, in combination with appropriate sampling, storage and processing, to derive physical properties of sea ice. |
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