Brief data description In 2019, winter and spring scientific research expeditions aboard the SA Agulhas II were conducted along the Good-Hope line (0o E) to the Antarctic marginal ice zone (MIZ) in the north-eastern Weddell Sea region as part of the Southern oCean seAsonal Experiment (SCALE; Ryan-Keogh and Vichi, 2022). During the winter expedition, three polar Iridium Surface Velocity Profilers (p-iSVPs; MetOcean model) were deployed by the South African Weather Service (SAWS) between 27 July and 28 July 2019. These buoys were analysed in de Vos et al. (2022). The region of deployment consisted of pancake-ice conditions with an average ice thickness of 40-60 cm. The instruments were deployed by hand by three people, lowered by crane from the ship to the ice on a basket cradle. The first buoy (p-iSVP 1) was deployed in water, in between pancake ice floes, while the other two buoys (p-iSVP 2 and p-iSVP 3) were deployed on roughly circular ice floes > 3 m in diameter. These buoys were expendable devices that recorded GPS position, air and ice temperature, and barometric pressure. The temporal resolution is 30 minutes for p-iSVP 1 and hourly for p-iSVP 2 and p-iSVP 3. The survival of these sensors depended on their battery life, since p-iSVPs can continue to drift in the ocean after ice melting and can be further refrozen in between floes. p-iSVP 1 and p-iSVP 3 continued to transmit data until 15 October 2019. p-iSVP 2 stopped transmitting data on 25 August 2019. During the spring expedition, three standard Iridium Surface Velocity Profilers (iSVPs 4-6; Pacific Gyre model) were deployed by SAWS between 24 October and 28 October 2019 (de Vos et al., 2022). Specifically-designed frames were built around these three iSVPs to allow them to stand securely on the ice, without damaging the non-polar battery, and also to make sure they operated as Lagrangian ice trackers. These buoys were deployed during first-year ice conditions, with an average ice thickness of 80-90 cm. The instruments were deployed with the same protocol as the winter buoys. These buoys recorded GPS position, air temperature and barometric pressure, every hour. Their survival, like the winter p-iSVPs, also depended on their battery life, and therefore it was possible for them to continue to drift after ice melting. The iSVPs transmitted data until 19 December 2019. Buoy names and raw data: p-iSVP 1: 300234067003010-300234067003010-20191015T064320UTC.csv p-iSVP 2: 300234067002060-300234067002060-20191015T064316UTC.csv p-iSVP 3: 300234066992870-300234066992870-20191015T064314UTC.csv iSVP 4: 300234066433050.xlsx iSVP 5: 300234066433051.xlsx iSVP 6: 300234066433052.xlsx Related code: The buoy data has been processed using https://github.com/mvichi/antarctic-buoys/.

{"references": ["de Vos, M., Barnes, M., Biddle, L.C., Swart, S., Ramjukadh C., and Vichi\u00a0M. (2022). Evaluating numerical and free-drift forecasts of sea ice drift during a Southern Ocean research expedition: An operational perspective,\u00a0Journal of Operational Oceanography,\u00a015(3),\u00a0187-203, https://doi.org/10.1080/1755876X.2021.1883293, 2022.", "Ryan-Keogh, T. and Vichi, M. (2022). SCALE-WIN19 & SCALE-SPR19 Cruise Report, Southern Ocean Seasonal Cycle Experiment, South Africa, 339 pp,\u00a0 https://doi.org/10.5281/zenodo.5906324.", "Womack, A., Vichi, M., Alberello, A., and Toffoli, A. (2022). Atmospheric drivers of a winter-to-spring Lagrangian sea-ice drift in the Eastern Antarctic marginal ice zone.\u00a0Journal of Glaciology, 1-15. https://doi.org/10.1017/jog.2022.14."]}

This research has been supported by the National Research Foundation of South Africa (grant no. 118745). This work has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement no. 101003826 via project CRiceS (Climate Relevant interactions and feedbacks: the key role of sea ice and Snow in the polar and global climate system). The authors would like to thank the South African Weather Service (SAWS) for the funding and deployment of the buoys. We acknowledge the Southern oCean seAsonaL Experiment (SCALE), and thank the captain and the crew of the SA Agulhas II for the assistance during the deployments.