Quantifying the biological carbon pump in oligotrophic subtropical gyres is hindered by sparse in situ coverage and uncertainty in satellite-derived net primary production (NPP), particularly its seasonal variability. Here we estimate net community production (NCP) in the western North Pacific subtropical gyre using three years of BGC-Argo oxygen observations interpreted with a mixed-layer O \(_2\) mass balance integrated to the maximum winter mixed-layer depth. Annual NCP was estimated to be 1.7 ± 0.4 mol C m \(^{-2}\) yr \(^{-1}\) , with a coherent seasonal cycle characterized by near-zero NCP during deep winter mixing and sustained positive NCP from spring through early autumn. Independent near-surface NCP estimates from underway \(\Delta\) O \(_2\) /Ar observations during three late-summer to early-fall cruises agree in sign and order of magnitude with the float-based estimates. Comparing Argo NCP with four satellite NPP products yields implied export efficiencies (e-ratio = NCP/NPP) spanning 0.11−0.23 annually, while seasonal e-ratios become unrealistically extreme because satellite NPP shows weak seasonality relative to the observed NCP cycle. These results indicate that satellite-based export estimates are susceptible to uncertainty that is dominated by differences among NPP algorithms and by weak or incorrect seasonal phasing when evaluated against the Argo NCP cycle.
