Warming substantially amplifies Antarctic coastal polynyas as key carbon sinks

Antarctic coastal polynyas, small open-water areas within sea ice, are revealed in this study to be unexpectedly powerful carbon sinks. Despite covering just ~3% of the Southern Ocean, they bury 42% of its organic carbon, making them the region’s most efficient carbon sequestration hotspots. Importantly, warming over the past 12 kyr amplifies this process ninefold by extending ice-free seasons, boosting phytoplankton growth, and accelerating carbon export to the seafloor. This counterintuitive finding reveals a natural brake on climate change: As global warming progresses, these polar carbon sinks grow stronger, partially offsetting rising CO2. This work transforms understanding of the Southern Ocean’s role in the global carbon cycle and highlights the need to incorporate these dynamics into climate models and policy.