IceBird summer sea ice thickness at the end of the Transpolar Drift from 2001 to 2020

• Main Authors: Belter, H. Jakob, Krumpen, Thomas, von Albedyll, Luisa, Birnbaum, Gerit, Hendricks, Stefan, Haas, Christian
• Format: Conference Object
• Language: unknown
• Published: 2020
• Subjects: Alfred Wegener Institute; Arctic Ocean; Fram Strait; Greenland; laptev; Laptev Sea; Sea ice; Svalbard
• Online Access: https://epic.awi.de/id/eprint/53796/; https://agu2020fallmeeting-agu.ipostersessions.com/default.aspx?s=F9-F8-09-91-92-46-26-1B-81-F3-A4-74-1B-C3-BC-6D; https://hdl.handle.net/10013/epic.464a6f12-5189-494e-b208-edef68cdad33

Fram Strait is the main exit gate for sea ice in the Arctic Ocean. Observations of changes in sea ice thickness (SIT) in this region are therefore an integration of time-varying changes along the pathways of sea ice that reaches Fram Strait. We present an extended time series of combined ground-based and airborne electromagnetic induction (EM) measurements of summer (July/August) SIT from within a selected area of interest (AOI, 81 to 86°N, 30°W to 20°E) between Svalbard and Northeastern Greenland, capturing the end of the Transpolar Drift. Measurements were taken within the framework of the regular IceBird Summer campaigns and ship-based expeditions conducted by the Alfred Wegener Institute for Polar and Marine Research between 2001 and 2020. While sea ice reaching the AOI was dominated by multi-year ice (ice older than two years) at the beginning of the time series, the fraction of second and first-year ice increased over the last decade. Mean and modal SIT decreased by about 0.5 m from 2001 to 2018. Minimum values were reached between 2016 and 2018, with 2016 showing the absolute minimum in modal SIT (approximately 1 m). Sea ice reaching the selected AOI was backtracked using the Lagrangian ice tracking tool, ICETrack. Resulting sea ice trajectories show that about 65% of the AOI-sampled ice originated from the Laptev Sea. The simple thermodynamic SIT model introduced by Thorndike (1992, T92) was utilized to model thermodynamic sea ice growth along the trajectories. The thermodynamic model generates ice thicknesses that are comparable to the modal thickness from EM measurements. T92 shows a general underestimation of AOI EM SIT for all years except 2016, when the modal AOI EM SIT is overestimated by about 0.4 m. This model overestimation was potentially connected to the increased upward ocean heat flux and more specifically a strong atlantification event in the regions of ice formation along the Russian shelves in 2015 (Polyakov, 2017).