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The main difficulties to retrieve sea ice thickness and volume in the southern ocean come from the lack of in-situ observation and knowledge related to sea ice properties. For instance, whereas in-situ observations in the Arctic have enabled to construct snow depth climatologies (e.g the Warren climatology), there are no equivalent snow depth data in the Austral. By consequence, except for a few studies such as Zwally et al, 2008, Kurtz and Markus, 2012 and more recently Kacimi and kwok, 2020, mainly based on based on ICESat's data, no valid sea ice thickness estimations have yet been drawn apart from an experimental ESA-SICCI product (available on the CCI Data Portal, http://cci.esa.int/data), but it does not currently extend beyond the 2016 winter. In this context, the objective of this presentation is to review the recent developments on sea ice volume estimations in the southern ocean conducted in the framework of an ESA Living Planet Fellowship and the ESA CSAO+ project. We will first present and compare two radar freeboard solutions calculated from the CryoSat-2 data. The first solution is based on the commonly used TFMRA50 retracker and the second solution has been derived from altimetric ranges calculated on the GPOD platform with the SAMOSA+ physical retracker. Then, we will describe the methodology used to recalibrate the Envisat Low Resolution Mode (LRM) on CryoSat-2 Synthetic Aperture radar (SAR) mode in order to provide homogeneous freeboard estimations. In a second part, we will evaluate the recent altimetric snow depth product (ASD) computed from the difference of radar penetration between the SARAL/AltiKa Ka-band and the CryoSat-2/SIRAL ku-band radar frequencies (Garnier et al, 2021). The ASD data will be used to compute the first 100 % altimetric SIT estimation that should also mimic the future CRISTAL mission datasets. This estimation will be compare with the ESA-SICCI product that considers the AMSR passive radiometer snow depth data. In addition, first elements of validation are presented by comparison with some Upward Looking Sonar data (ULS, Behrendt et al, 2013), transects measurements during the Sea Ice Mass Balance in the Antarctic, (SIMBA, Lewis, 2011) and the ICESat's data. Finally, we will present and analyse tendencies of 2003-2020 sea ice volume time series in the Antarctic. |
