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

Zhangxian Ouyang1, Wenli Zhong2, Di Qi3, Liqi Chen3 and Wei-Jun Cai1, (1)University of Delaware, School of Marine Science and Policy, Newark, DE, United States, (2)Ocean University of China, Qingdao, China, (3)Third Institute of Oceanography, State Oceanographic Administration of China, Key Laboratory of Global Change and Marine-Atmospheric Chemistry of State Oceanic Administration, Xiamen, China
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.