Knowledge Bank

Seasonally ice-covered lakes represent nearly half of all lakes globally and play a major role in processes such as carbon cycling due to their storage and release of methane and carbon dioxide. However, the physical structure of the ice cover itself, particularly the void spaces within it, remains poorly quantified despite its climate and ecological importance because of its ability to store and release gases and solutes. This study aimed to quantify void space distribution in natural (Trout Bog, WI, USA) and laboratory-grown lake ice using X-ray micro-computed tomography (micro-CT) and assess the technique’s effectiveness for characterizing porosity and structural imperfections. Ice samples were scanned using a Bruker SkyScan 1173 system, and 3D reconstructions were processed to estimate porosity profiles with depth. Micro-CT was shown to be an effective method for visualization of void spaces in 3D and for quantifying porosity across ice sections. Natural ice samples exhibited the highest porosity in the uppermost superimposed ice layers and decreased to near zero with depth as congelation ice formed. The laboratory-grown ice exhibited an opposite trend with highest porosity nearest the water-ice boundary. Across all samples, porosity values were low relative to the shallow, methane-rich lakes of the Arctic. These findings suggest a reduced potential for gas retention within Trout Bog ice cover and highlight the influence of lake morphology and freezing conditions on void structure. This work shows the value of micro-CT scanning for future studies investigating bubble morphology, gas storage in ice-cover, and greenhouse gas cycling under changing winter conditions.