Three Years of Near-Coastal Antarctic Iceberg Distribution From a Machine Learning Approach Applied to SAR Imagery

Mass loss around the Antarctic Ice Sheet is driven by basal melting and iceberg calving, which constitute the two dominant paths of freshwater flux into the Southern Ocean. Although of similar magnitude, icebergs play an important and still not fully understood role in the balance of heat and freshwater around Antarctica. This lack of understanding is partly due to operational difficulties in large-scale monitoring in polar regions, despite observational and remote sensing efforts. In this study, a novel machine learning approach, augmented by visual inspection, was applied to three Synthetic Aperture Radar (SAR) mosaics of the whole Antarctic continent and its adjacent coastal zone. Although originally intended for a mapping of the Antarctic continent, the SAR mosaics allow us to document the evolution and distribution of the size (and mass) of icebergs in the pan-Antarctic near-coastal zone for the years 1997, 2000, and 2008. Our novel algorithm identified 7,649 icebergs in 1997, 13,712 icebergs in 2000, and 7,246 icebergs in 2008 with surface areas between 0.1 and 4,567.82 km(2) and total masses of 4,641.53, 6,862.81, and 5,263.69 Gt, respectively. Large regional variability was observed, although a zonal pattern distribution is present. This has implications for future climate modeling studies that try to estimate the freshwater flux from melting icebergs, which demands a realistic representation of the interannually varying near-coastal iceberg pattern to initialize the simulations.