Observing the Relationship Between Freeboard, Snow Depth, and Sea-Ice Thickness: Recent Advances in the AWI IceBird Campaigns

• Main Authors: Jutila, Arttu, Hendricks, Stefan, Ricker, Robert, von Albedyll, Luisa, Krumpen, Thomas, Haas, Christian
• Format: Conference Object
• Language: unknown
• Published: 2021
• Subjects: Arctic; Arctic Ocean; Sea ice
• Online Access: https://epic.awi.de/id/eprint/55289/; https://epic.awi.de/id/eprint/55289/1/jutila-agu.pdf; https://agu2021fallmeeting-agu.ipostersessions.com/?s=A1-D5-39-92-1F-8D-44-A2-58-9D-3A-5D-6B-15-54-E5; https://hdl.handle.net/10013/epic.4c1a097b-3b65-4854-b8f0-d2ad2dafaf62; https://hdl.handle.net/

Alfred Wegener Institute’s (AWI) IceBird program is a series of airborne campaigns carried out in winter and summer using a fixed-wing Basler BT-67 research aircraft to measure Arctic sea ice and to monitor its change. In 2017, the primary scientific instrument configuration including an airborne laser scanner (ALS) for surface topography and freeboard measurements and a tethered electromagnetic induction sounding instrument (EM-Bird) for total (snow+ice) thickness measurements was complemented with an ultrawideband frequency-modulated continuous-wave microwave radar to measure snow thickness. With the unique instrumentation onboard the IceBird campaigns, we are able to observe the respective thicknesses of the snow and sea-ice layers in high resolution along survey tracks on regional scale. Here, we describe the IceBird program concept and focus on the winter campaigns that take advantage of the full instrument configuration. We present recent data of high-resolution, collocated, airborne sea-ice and snow thickness and freeboard measurements based on over 3000 km of profiles collected in the western Arctic Ocean in April 2017 and 2019. The individual parameters are important for describing and monitoring the state of the Arctic sea ice and validating retrievals from satellite data, but combined they offer further possibilities to characterize sea ice. By assuming isostatic equilibrium, we are able to derive up-to-date estimates for sea-ice bulk density for first-year and multi-year ice, including deformed ice. As an outlook, we derive a parametrization of sea-ice bulk density based on sea-ice freeboard for further applications, such as evaluating the freeboard-to-thickness conversion for satellite altimetry.