Expanding seawater carbon dioxide and methane measuring capabilities with a Seaglider

Abstract. Warming, ocean acidification, and deoxygenation are increasingly putting pressure on marine ecosystems. At the same time, thawing permafrost and decomposing hydrates in Arctic shelf seas may release large amounts of methane (CH₄) into the water column, which could accelerate local ocean acidification and contribute to climate change. The key parameters to observing and understanding these complex processes and feedback mechanisms are vastly undersampled throughout the oceans. We developed carbon dioxide (CO₂) and CH₄ gliders, including standard operational procedures with the goal that CO₂ and CH₄ measurements become more common for glider operations. The Seagliders with integrated Contros HydroC CO₂ or CH₄ sensors also include conductivity, temperature, depth, oxygen, chlorophyll-a, backscatter, and fluorescent dissolved organic matter sensors. Communication via satellite allows for near-real time data transmission, sensor adjustments, and adaptive sampling. Several sea trials with the CO₂ Seaglider in the Gulf of Alaska and data evaluation with discrete water and underway samples suggest near ‘weather quality’ CO₂ data as defined by the Global Ocean Acidification Network. A winter mission in Resurrection Bay, Alaska provides first insights into the water column inorganic carbon dynamics during this otherwise undersampled season. The CH₄ Seaglider passed its flight trials in Resurrection Bay and is ready to be deployed in an area with greater CH₄ activity. Both sensing systems are available to the science community through the industry partners (Advanced Offshore Operations and -4H-JENA) of this project.