| Summary: | Patterns of primary productivity in the Arctic are expected to change with continued warming, yet productivity measurements are historically limited, both spatially and temporally. An established method of measuring net biological oxygen production, which can be used to estimate net community production (NCP) rates, is with an equilibrated inlet mass spectrometer (EIMS) that measures oxygen to argon ratios (O₂/Ar) in underway seawater. An emerging method that may provide comparable estimates of biological oxygen production involves a gas tension device (GTD) coupled with an optode, which yields oxygen to nitrogen ratios (O₂/N₂). The GTD+optode combination is small, inexpensive, and capable of autonomous deployments on ships, moorings, and other surface platforms; however, the dissimilarity in gas solubility between O₂ and N₂ makes this tracer pair less favorable than O₂/Ar. We conducted a side-by-side comparison of a GTD and EIMS during the 2019 Arctic Integrated Ecosystem Survey OS1901-L1 in the Pacific Arctic. We found that O₂/Ar and O₂/N₂ tracked each other closely, with small differences due to physical drivers of deviations between O₂/Ar and O₂/N₂, including wind and temperature changes. The NCP estimates from O₂/N₂ were generally consistent with O₂/Ar-based NCP estimates observed on this cruise, with median NCP from O₂/Ar and O₂/N₂ of 7.49 ± 2.34 and 7.16 ± 2.68 mmol O₂ m⁻² day⁻¹, respectively, suggesting the GTD-based method can be used to enhance spatial and temporal coverage of NCP measurements. However, the GTD/optode approach is reliant on well-calibrated oxygen observations, which may present a challenge in some cases.
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