Changing Arctic Sea-ice Thickness observed by Radar Altimetry

Radar altimetry represents the longest continuous remote sensing data record for observing changes of sea-ice thickness in the northern hemisphere. The ESA Climate Change Initiative publically released the version 2 of the sea-ice thickness climate data record (CDR) from Envisat and CryoSat-2 data from 2002 to 2017 and operational continuity is ensured by the Copernicus Climate Change Services (C3S). The C3S CDR includes monthly thickness fields from 16 winter seasons, adding crucial information to other sea ice parameters, such as concentration and type. However, estimating changes of sea-ice volume in this period is impracticable due to the large pole hole of the Envisat orbit.

We therefore analyse the variability, overall trend and extreme conditions of the radar altimetry CDR in the period of 2002 to 2018 and the Arctic Basin where both Envisat and CryoSat-2 provide continuous regional coverage. The results are compared to those from ICESat and we find that thickness anomalies are in better agreement than magnitude of thickness. On longer periods, comparison to in-situ observations along moorings and aircraft surveys indicate that the radar altimetry CDR tends to underestimate the sea-ice thickness decline in the Beaufort Sea between 2002 and 2015. Both findings reinforces the need to improve parametrizations and auxiliary data sources for better stability of the climate data record, especially with a potential extension of the data coverage with the ERS-1/2 time series.