Glacial meltwater drives high CH₄ supersaturation in Maxwell Bay, King George Island (Southern Ocean)

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.