Snow Microstructure over Antarctic Landfast Ice

Landfast ice plays a significant role in climate and ecosystems in Antarctic coastal regions. From October to December 2022, we investigated the physical properties of snow and sea ice on Antarctic landfast ice in McMurdo Sound, following the protocols from the MSOAiC expedition. Our measurements confirmed some findings from MOSAiC (e.g. the potential mass transfer from the sea ice surface to snow , the high spatial variability of snow depth}, and the discrepancy between meteorological snowfall and snow accumulation),  but we also had observations that were contrasting our MOSAiC data, for example: 1) presence of salt up to 15 cm of snow height (as opposed to MOSAiC's 5 cm for a relatively similar total snow height), 2) the lack of the surface scattering layer on melting sea ice, which caused significantly lower albedos of bare sea ice (0.45, as opposed to MOSAiC's 0.65), 3) average densities of non-melting snow of 450 kg/m³ (as opposed to MOSAIC'S 350 kg/m³ ). Here, we will discuss the microCT measurements from our samples and relate them to the macroscale obervations of parameters like snow density, snow height, snow surface roughness, salinity or stable water isotopes. The main focus in this study in on the prevalance of a prominent depth hoar layer at the snow-ice interface, which we to be caused by the mass transfer between snow and ice because of the large vertical temperature gradients. This is also visible by the microscale roughness of the interface. Additionally, we will discuss the microstructure of the extremely dense wind slab that dominates most of the snow profile and the implications of these findings for modelling and remote sensing of snow on sea ice.