Summer Net community production (NCP) and CO2 flux evolutions in the western Arctic Ocean

Using high-resolution underway measurements of sea surface O₂/Ar and pCO₂collected in the summer of 2016 and 2018 in the western Arctic Ocean, we examined the seasonal and regional variabilities in biological metabolic status and the coupling of net community production (NCP) and CO₂ fluxes. We found that the variation in the coupling of NCP and CO₂ flux is intimately associated with the histories of wind and ice. In the heavy ice-covered region, a weak primary production could induce a large CO₂ air-sea gradient (DpCO₂) but a small CO₂ flux due to the presence of ice and the long residence time of gases. At the marginal ice zone, we observed that the magnitudes of NCP and CO₂ flux well match to each other with a strong linear relationship, suggesting that, at the early-melting stage, biological CO₂ removal was balanced by air-sea CO₂ fluxes. For the ice-free waters, the coupling of NCP and CO₂ flux vary regionally based on the differences in nutrient supply. In the oligotrophic ice-free basin, no apparent correlation between NCP and CO₂ flux was found. The weak NCP and small DpCO₂ prevent the basin from being a bigger CO₂ sink. On the contrary, a strong biological primary production far exceeded the rate of CO₂ uptake was found on the nutrient-rich Chukchi Shelf, which not only results in a large CO₂ sink but also a large mismatch between NCP and CO₂ flux. Our extensive data and analysis provide an overview of seasonal (summer to early fall) NCP and CO₂ flux evolutions in the western Arctic Ocean with potential implications for future changes.