Advancing microwave radar retrievals of snow depth on sea ice: toward full characterisation of the snow and sea-ice layers

• Main Author: Jutila, Arttu
• Other Authors: Haas, Christian, Eisen, Olaf
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: Universität Bremen 2022
• Subjects: snow; sea ice; microwave remote sensing; radar altimetry; airborne measurements; 530; 530 Physics; ddc:530; Arctic; Arctic Ocean; Sea ice
• Online Access: https://media.suub.uni-bremen.de/handle/elib/5832; https://doi.org/10.26092/elib/1455; https://nbn-resolving.org/urn:nbn:de:gbv:46-elib58324

Snow is a key factor in the sea-ice and Earth's climate systems that modifies the physical, climatic, and biogeochemical processes taking place. One of its most important impacts is in regulating sea-ice growth and melt. Despite its importance, little is known about the spatial and temporal distribution of snow depth on sea ice on the regional to global scales. Snow is tightly coupled to the highly dynamic sea-ice and atmospheric conditions and it is, therefore, very heterogeneous and constantly evolving both in space and in time. As a spatially and temporally representative, global, year-round product of snow depth observations on sea ice does not exist to this date, applications often have to rely on climatological values that do not necessarily hold true in the rapidly warming global climate. The unknown properties directly translate into the uncertainty of the result. This dissertation takes on the ambitious goal of working toward full characterisation of the snow and sea-ice layers. To achieve that, the focus is on advancing microwave radar retrievals of snow depth on sea ice. Enhanced snow depth observations will enable improving other measurements of sea-ice related parameters, most importantly sea-ice thickness, and in joint analysis of coincident sea-ice measurements estimating sea-ice bulk density becomes possible. In the first step, field experiments with ground-based C and K band pulse radars are carried out to investigate microwave penetration into the snow cover. The results show the K band microwaves expectedly reflect from the snow surface while the C band microwaves penetrate closer to the snow–sea-ice interface potentially enabling dual-frequency snow depth retrieval in less than half of the studied cases and only on first-year ice. In the second step, radar measurements of snow depth on sea ice are upscaled by using an airborne radar in the western Arctic Ocean in 2017–2019. A high-sensitivity, ultra-wideband, frequency-modulated continuous-wave (FMCW) radar is integrated to the instrument ...