BREAK OUT OF A-76 ICEBERG AND RECENT DYNAMIC CHANGES OF ITS ENCOLSURE RIFTS IN RONNE ICE SHELF, ANTARCTICA

Abstract. Monitoring the stability of the Ronne Ice Shelf, particularly the calving event, is an integral and important part of the study of Antarctic ice sheet mass balance and sea-level rise. This paper presents the results of the analysis of the world’s largest iceberg (A-76 iceberg), which was formed during a calving event in the Ronne Ice Shelf (RIS) on May 13, 2020, and subsequently broke into three fragments (A-76A, A-76B, and A-76C icebergs). The iceberg development cycle, up to this point, including its formation, separation and drift, was observed and analyzed. The detailed development process of rifts associated with the detachment of the A-76 iceberg in front of RIS before calving was analyzed using remote sensing data from multiple sources (ERS, RADARSAT-1, ALOS PALSAR, Landsat-7, and Landsat-8). In addition, based on a total of 66 Sentinel-1 A/B Synthetic Aperture Radar (SAR) images acquired between May 13, 2021 and March 11, 2022, a multi-scale segmentation approach was applied to continuously track the drift path of A-76 icebergs, A-76A, A-76B, and A-76C. We calculated the average drift velocity of these icebergs and found that A-76C iceberg drifted the fastest, followed by A-76A, and A-76B, from May 30, 2021, to March 11, 2022. Future tracking of other iceberg parameters, such as area, thickness, freeboard, and volume, could help assess the melting rates of the icebergs.