Active Scattering in Sea Ice for Measuring Internal Properties

Sea ice is filled with small brine pockets because the salt is rejected by the crystal lattice during the freezing process. These brine pockets have a significant influence on several aspects of sea ice, including its bearing capacity, the remote sensing of it, as well as the amount of solar energy available to support life beneath and within the ice. These pockets are usually measured directly by thin sectioning of ice cores or indirectly through the salinity of melted ice core sections. However, the extraction of ice cores introduces significant uncertainties due to both brine drainage and cooling. It is therefore important to act quickly in the field to minimize these effects. Previous work by Light et al. [2008] and most recently Perron et al. [2021] have utilized the ability of brine pockets to scatter light and thereby get insight into its structural properties. They both use a probe which is lowered into an auger hole, and it is therefore a non-destructive way of measuring profiles with minimal cooling and brine drainage. While Light et al. use passive scattering from the sun, Perron et al. use active scattering by attaching a light source to the probe and measuring the backscattering. My thesis aims to further develop the method of active scattering as it can be used during the polar night while providing profile information independent on higher layers in the sea ice. This will be done by building a similar prototype and using it to retrieve scatter profiles. By comparing the scatter profiles with temperature- and salinity profiles, a model will be set up to describe the relationship between the different profiles. The fieldwork will take place in collaboration with UNIS around Easter 2024, possibly as part of the courses AGF-211 and AT-311, but self-planned in Svea as plan B. In 2023, I made the first prototype and tested it in Qaanaaq. The results are very promising and I am therefore very optimistic in the second prototype, which is far more complex.