A decade-plus of Antarctic sea ice thickness and volume estimates from CryoSat-2 using a physical model and waveform-fitting

Abstract. We utilize a physical waveform model and a waveform-fitting method to estimate the snow depth and snow freeboard of Antarctic sea ice from CryoSat-2, and use these estimates to calculate the sea ice thickness and volume over an 11+ year time series. We compare our snow depth and thickness estimates to other altimetry- and ship-based observations, and find good agreement overall with some discrepancies in certain regions and seasons. The time series is used to calculate trends in the data, and we find small but statistically significant negative trends in the Ross Sea autumn (-0.3 cm yr-1), the Eastern Weddell winter (-0.8 cm yr-1), and the Western Weddell autumn and annual-average (-2.6 and -1.6 cm yr-1, respectively). Significant positive trends are found in the pan-Antarctic summer (0.4 cm yr-1) and Amundsen-Bellingshausen winter and annual-average (2.3 and 0.9 cm yr-1, respectively). Though pan-Antarctic trends in sea ice thickness and volume are small between 2010–2021, we find larger-magnitude trends regionally and since 2014. We place these thickness estimates in the context of a longer-term, snow-freeboard-derived, laser-radar sea ice thickness time series that began with ICESat and continues with ICESat-2. Reconciling and validating this longer-term, multi-sensor time series will be important in better understanding changes in the Antarctic sea ice cover.