Refined Estimates of Net Community Production in the Subarctic Northeast Pacific Derived From ΔO₂/Ar Measurements With N₂O‐Based Corrections for Vertical Mixing

We present the first field application of a N 2 O‐based approach to correct for vertical mixing in the estimation of net community production (NCP) from mixed layer O 2 measurements. Using new ship‐based observations of N 2 O and biological oxygen saturation anomalies (ΔO 2 /Ar) from the Subarctic Northeast Pacific, we provide refined mixed layer NCP estimates across contrasting hydrographic regimes and a comprehensive assessment of the methodological considerations and limitations of the approach. Increased vertical mixing coefficients at the base of the mixed layer, derived using N 2 O measurements, corresponded with periods of heightened wind speed and coastal upwelling. Corrections were most significant in coastal regions where the vertical supply of low‐O 2 water can otherwise falsely imply net heterotrophy from negative ΔO 2 /Ar measurements. After correcting for the mixing flux, all coastal stations showed autotrophic signatures, with maximum NCP exceeding 100 mmol O 2 m −2 d −1 in the spring and summer. Vertical fluxes were lower in off‐shelf waters but often contributed more than 50% to corrected NCP. At some oceanic stations, however, the cooccurrence of N 2 O minima and O 2 maxima resulted in biased (overestimated) N 2 O corrections. Evaluating vertical fluxes in these regions remains a challenge for ship‐based studies. Nonetheless, our refined NCP estimates show better coherence with surface chlorophyll, temperature, and mixed layer depth than uncorrected values. Potential mixed layer N 2 O production introduces some uncertainty in the approach, but errors are likely to be small. Ultimately, this work provides rationale for the adoption of the N 2 O correction to refine NCP estimates, particularly in coastal waters.