Abstract

Coastal waters exhibit the highest and most dynamic dissolved CH4 concentrations in marine environments, but significant knowledge gaps on the distribution and emissions, particularly in the Southern Ocean, still exist. We quantified dissolved CH4 concentrations and sea–air fluxes in the coastal waters of Maxwell Bay, King George Island, Antarctica, in December 2023. Surface waters showed exceptionally high CH4 supersaturations (213–2342%), associated with lower salinity and higher turbidity, which were attributed primarily to meltwater discharge from a retreating tidewater glacier. Our findings suggest that glacial melt may significantly increase CH4 emissions from Antarctic coastal waters, highlighting the need for further research to understand CH4 dynamics and improve emission estimates in the context of accelerating climate-driven glacial melt. © 2025 The Author(s). Limnology and Oceanography Letters published by Wiley Periodicals LLC on behalf of Association for the Sciences of Limnology and Oceanography.