Abstract
AbstractWe analysed the three-dimensional microstructure of sea ice by means of X-ray-micro computed tomography. Microscopic (brine- and air- pore sizes, numbers and connectivity) and macroscopic (salinity, density, porosity) properties of young Arctic sea ice were analysed. The analysis is based on ice cores obtained during spring 2016. Centrifuging of brine prior to CT imaging has allowed us to derive confident relationships between the open, vertically connected and total porosity of young sea ice at relatively high temperatures. We analysed the dependence of the microscopic properties on vertical position and total brine porosity. Most bulk properties (salinity, density) and pore space properties (pore sizes and their distribution) show a strong dependence on total brine porosity, but did not change significantly over the course of the field work. However, significant changes were observed for pore numbers (decreasing over time) and pore connectivity (increasing over time). CT-based salinity determinations are subject to larger than standard uncertainties (from conductivity), while the CT method yields important information about the salinity contributions from closed and open pores. We also performed a comparison of CT-based air porosity with calculations based on density from hydrostatic weighing. The consistency is encouraging and gives confidence to our CT-based results.
Highlights
Sea ice is a key element in earth’s climate system, it has an impact on the heat and moisture transfer between the ocean and the atmosphere and influences the global albedo (Ebert and Curry, 1993)
Microscopic properties have been derived from the combination of two non-destructive techniques (i) centrifuging of brine for separation of the connected and disconnected pore space and (ii) 3-D micro-computed tomography (CT) imaging followed by analysis of the pore size characteristics
(1) Density and air porosity determinations based on hydrostatic weighing and CT images show good consistency within the range measurement accuracy (≈ 0.2 %) and natural variability (≈ 0.5 %)
Summary
Sea ice is a key element in earth’s climate system, it has an impact on the heat and moisture transfer between the ocean and the atmosphere and influences the global albedo (Ebert and Curry, 1993). Unlike freshwater ice, brine in pore networks and inclusions. As the interest in exploring natural resources and shipping traffic in the Arctic is increasing (Peters and others, 2011), sea ice becomes an engineering challenge (Schwarz and Weeks, 1977). The sea-ice porous space can act as a buffer (Petrich and others, 2013; Salomon and others, 2017; Desmond and others, 2021). Physical, optical and mechanical characteristics of sea ice, relevant to its geophysical, biological and engineering properties, are strongly linked to its microstructure
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