**3. Sea ice thickness inversion**

The thickness and volume of the sea ice in the Arctic region are estimated in this paper by using L1b level data from the Cryosat-2 radar altimetry satellite, and the main steps are illustrated in **Figure 5**. First, the echo signal data in the Arctic sea region are denoised. Then, the echo signal classification and re-tracking correction are performed, and the sub-satellite point elevation is calculated. Finally, the sea ice thickness is calculated based on the sea ice static equilibrium model, supplemented by the snow depth and the sea ice density data.
