Lake Ice Thickness retrieval using TanDEM-X immediate interferometry

Abstract. Knowledge of Lake Ice Thickness (LIT) is essential for understanding the cryosphere and monitoring current climate change impacts. However, accurately retrieving LIT at the desired spatial-temporal scale remains a challenge, as many lakes are in remote regions and LIT is a logistically expensive parameter to measure. Interferometric synthetic aperture radar (InSAR) provides a novel approach to estimating ice thickness by measuring surface deformations at high resolution. This study used TanDEM-X pursuit mode that offers minimal temporal correlation to maintain high coherence for accurate LIT retrieval in thermokarst lakes in Northern Alaska during the 2014–2015 winter season. The InSAR-derived LIT was validated against simulations from the Canadian Lake Ice Model (CLIMo), supported by in-situ snow and ice measurements. Results show consistent ice growth patterns and an RMSE of 0.08–0.26 m, demonstrating that the proposed method captures LIT evolution with reasonable agreement with CLIMo estimates. By employing an immediate interferometric approach, the present study maintains sufficient coherence to isolate and highlight the influence of volume scattering, which shifts the phase center away from the ice-water interface, and is the main factor limiting the accuracy of the LIT retrieval. These findings provide new insights into the technology of InSAR-derived LIT and suggest that SAR missions operating at longer wavelengths, such as NISAR and TanDEM-L, hold significant potential for improving retrieval accuracy by enhancing penetration and reducing sensitivity to internal scattering within the ice volume.